Table of Content

15 September 2019, Volume 30 Issue 9

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Soil carbon, nitrogen and phosphorus stoichiometry characteristics of Pinus sylvestris var. mongolica belt-mixed forests.

WANG Kai, LEI Hong, SHI Liang, ZHANG Ri-sheng, SONG Li-ning

2019, 30(9):  2883-2891.  doi:10.13287/j.1001-9332.201909.001

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To provide theoretical basis for management of Pinus sylvestris var. mongolica mixed plantation, the variation of soil carbon, nitrogen and phosphorus stoichiometry in different P. sylvestris var. mongolica belt-mixed plantations were explored. Taking the monoculture plantation as control, soil samples were collected at the distance of 0, 1, 2, 3, and 4 m from the center point in P. sylvestris var. mongolica and Ulmus pumila mixed plantation and P. sylvestris var. mongolica and Maackia amurensis mixed plantation along the two directions of P. sylvestris var. mongolica and its associated species in different soil layers. Contents and stoichiometric ratios of soil organic C, total N, total P, available N, available P were analyzed. The results showed that soil organic C, total N, and available N in P. sylvestris var. mongolica mixed plantations were higher than those in pure plantation. The soil organic C, total N contents, C/N and C/P in deep soil layers were increased under P. sylvestris var. mongolica and U. pumila mixed plantation. The soil N content increased but P content decreased in P. sylvestris var. mongolica and M. amurensis mixed plantation. With the increases of distance from the center of mixed plantation, soil C/N firstly increased and then decreased, while soil total P and available P contents decreased and N/P increased in P. sylvestris var. mongolica belt. Soil C/N decreased and available P contents firstly increased and then decreased with the increases of distance from the center in U. pumila belt of P. sylvestris var. mongolica and U. pumila mixed plantation. Soil total N content firstly decreased and then increased in P. sylvestris var. mongolica belt, but it firstly increased and then decreased in M. amurensis belt of P. sylvestris var. mongolica and M. amurensis mixed plantation. P. sylvestris var. mongolica mixed plantation could improve soil C and N stocks compared with pure plantation. The best mixed mode was P. sylvestris var. mongolica and U. pumila mixed by one row, as well as P. sylvestris var. mongolica and M. amurensis mixed in two rows.

Responses of productivity of typical natural secondary forests and plantations to climate change in Shaanxi Province, China

LIANG Si-qi, PENG Shou-zhang, CHEN Yun-ming

2019, 30(9):  2892-2902.  doi:10.13287/j.1001-9332.201909.022

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We analyzed the changes of net primary productivity (NPP) and net ecosystem productivity (NEP) of Quercus spp. forest and Robinia pseudoacacia plantation under different future climate scenarios in Shaanxi Province during 2015-2100, using the process-based dynamic vegetation model-LPJ-GUESS. The results showed that compared with the benchmark period (1961-1990), NPP of Quercus spp. forest and R. pseudoacacia plantation in northern Shaanxi would decrease by 4.9%-29.5% and 22.5%-56.2% respectively, while that in Guanzhong and southern Shaanxi would increase by 13.0%-49.0% and 21.3%-62.9% respectively in the future. The NPP of Quercus spp. forest and R. pseudoacacia plantation under the RCP_8.5 scenario was the highest, followed by that under the RCP_4.5 and RCP_2.6 scenarios. Those two types of forest would be carbon sink in three subregions in the future. Quercus spp. forest would have stronger carbon sink function in nor-thern Shaanxi and Guanzhong, while R. pseudoacacia plantation would have stronger carbon sink function in Southern Shaanxi. Under different RCP scenarios, the NEP variation range of R. pseu-doacacia plantation was greater than that of Quercus spp. forest in three subregions.

Effects of freeze-thaw and soil moisture on content and spectral structure properties of dissolved organic matter in forest soil leachates.

KONG Yu-hua, ZHU Long-fei, WU Hao-hao, FU Ping-qing, XU Xing-kai

2019, 30(9):  2903-2914.  doi:10.13287/j.1001-9332.201909.005

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The contents and stability of soil dissolved organic matter (DOM) can affect key processes of soil carbon and nitrogen cycle. The responses of DOM content and its spectral structure pro-perties in forest soils to climate change remain unclear. We collected soil samples from two temperate forests, i.e., the broadleaf and Korean pine mixed forest (BKPF) and adjacent secondary white birch forest (WBF), in Changbai Mountains, northeastern China. Using a combination of three-dimensional fluorescence spectrum and parallel factor analysis, a simulated freeze-thaw experiment was conducted in the laboratory. We examined the effects of freeze-thaw intensity, freeze-thaw cycle and their interaction on the content, components and spectral properties of DOM leached from the two forest surface soils with different moisture levels. The results showed that DOM content and components of soil leachates varied with forest types, soil moisture, freeze-thaw intensity and freeze-thaw cycle. The DOM content in the leachates was lowest at medium moisture level and was significantly affected by the high freeze-thaw intensity. In addition, the DOM content increased first and then decreased with the increases of freeze-thaw cycles. Three fluorescence components of DOM in the forest soil leachates were identified as humic acid-like DOM, fulvic acid-like DOM and protein-like DOM. The DOM components of BKPF soil leachates were mainly consisted of fulvic acid-like substances with a high humification index. However, the DOM from WBF soil leachates was dominated by humic acid-like substances with low stability, and the three fluorescence components were significantly affected by the freeze-thaw intensity. Results from the redundancy analysis showed that under the experimental conditions, forest type played a leading role in changing DOM properties. The DOM content and its three fluorescence intensities of WBF soil leachates were higher than those of BKPF. Soil moisture significantly affected the aromaticity of DOM in the forest soil leachates, and the DOM aromaticity of soil leachates from the two forest stands ranked as medium moisture > high moisture > low moisture. With the increases of freeze-thaw intensity, the DOM aromaticity of BKPF soil leachates significantly decreased. Furthermore, the increases of freeze-thaw cycles significantly increased the humification degree of DOM in the forest soil leachates. Therefore, upon different freeze-thaw disturbance, the DOM content and bioavailability of soil leachates with low moisture tended to increase, particularly in the WBF soil leachates, which may result in an increased lea-ching of DOM in temperate forest soils during spring freeze-thaw periods. The results provide a refe-rence for further investigating DOM turnover in temperate forest soils during spring freeze-thaw periods.

Effects of slope direction on soil nutrient and its ecological stoichiometry in bamboo forest

CHEN Han-xi, HAI Long, HUANG Li-min, MAO Zheng-rong, CHAI Yan-jun

2019, 30(9):  2915-2922.  doi:10.13287/j.1001-9332.201909.025

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We analyzed the effects of slope direction on soil nutrients and ecological stoichiometry by collecting soil samples from different slope directions (shady slope and sunny slope) of the bamboo forest in Longyou County, Zhejiang Province. The results showed that soil nutrients were affected by slope direction and soil depth. The nutrients level of soils in the sampling area showed the trends of shady slope > sunny slope, and surface soil > bottom soil. Compared to sunny slope, the cation exchange capacity (CEC), the contents of total organic carbon, total nitrogen, alkaline hydrolyzed nitrogen, available phosphorus, total potassium and available potassium of shady soils significantly increased by 43.7%, 103.8%, 92.0%, 75.5%, 22.4%, 89.4% and 240.7%, respectively. There was no significant difference in total phosphorus contents between shady slope and sunny slope. At all soil layers, there was no significant difference of C/N ratio between shady and sunny slopes. The average C/P ratio of shady slope was 180.8%, 42.0% and 54.3% higher than that of sunny slope at 0-20 cm, 20-40 cm and 40-60 cm, respectively. At each soil layer, the average C/K and N/K ratios between shady and sunny slopes had no significant difference. The average C/K and N/K ratios of shady slope and sunny slope were all significantly different among the three soil layers. In the shady slope, the contents of soil organic carbon showed significantly positive correlation with total nitrogen, total phosphorus, total potassium, and soil available nutrients. Overall, soil nutrients and ecological stoichiometry characteristics of shady slope of bamboo forest were superior to those of sunny slope.

Effects of litter removal and nitrogen addition on carbon and nitrogen in different soil fractions in a subtropical broad-leaved forest.

WU Yue, MA Hong-liang, YIN Yun-feng, GAO ren, WANG Meng-si, YANG Liu-ming

2019, 30(9):  2923-2932.  doi:10.13287/j.1001-9332.201909.011

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The increasing nitrogen deposition due to human activities has impacted forest ecosystems to a large extent. The organic carbon and nitrogen released from decomposing litters play an important role in the formation, stability and transformation of soil organic carbon and nitrogen. We collected soil samples from a subtropical evergreen broadleaved forest experiment with nitrogen deposition [control (0), LN (75 kg·hm^-2·a^-1), HN (150 kg·hm^-2·a^-1)] and litter control (litter retained and litter removal) for eight years. After extracted by solution of K₂SO₄, Na₂B₄O₇, Na₄P₂O₇, NaOH, H₂SO₄, Na₂S₂O₄ and HF step by step, carbon and nitrogen in each extraction was analyzed. The results showed that overall most of soil carbon and nitrogen existed in the Humin fraction, accounting for 33.5% of the total carbon and 33.3% of the total nitrogen. The soluble total carbon and nitrogen extracted by Na₂B₄O₇ solution was the highest, followed by NaOH and Na₄P₂O₇ solution. The soluble total carbon, soluble total nitrogen and soluble organic nitrogen of soil extracted by three reagents accounted for 46.2%, 47.9%, and 76.5% of the total extractions, respectively. In addition, nitrogen addition significantly increased carbon and nitrogen content in Na₂S₂O₄ and Humin fractions. Litter removal reduced carbon content in Na₂B₄O₇, H₂SO₄, Na₂S₂O₄ and Humin fractions, and nitrogen content in NaOH, HF and Humin fractions. The nitrogen content in the K₂SO₄ extraction was significantly increased by both litter remained and nitrogen addition. Our results demonstrated that litter and nitrogen added could mutually affect carbon and nitrogen concentration of soil fractions with different chemical stability, with consequences on the process of soil carbon and nitrogen.

Spatial structure characteristics of the main tree species in a mixed broadleaved Korean pine (Pinus koraiensis)forest in a mountainous area of eastern Liaoning Province, China

MAO Yi-xin, ZHANG Hui-dong, WANG Rui-zhao, YAN Ting-wu, WEI Wen-jun, YOU Wen-zhong

2019, 30(9):  2933-2940.  doi:10.13287/j.1001-9332.201909.021

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Maintaining forest structural diversity is generally considered as an effective way to preserve forest stability and biodiversity. The spatial structure characteristics of the dominant tree species in a climax community were investigated in a primary mixed broadleaved Korean pine (Pinus koraiensis) forest in a mountainous area of eastern Liaoning. Stand spatial structure parameters were determined based on the relationships among neighboring trees. The climax communities were used as a theoretical reference for optimizing the spatial structure of a low-quality secondary forest and monoculture plantation. The diameter distribution of the trees in the pine forest exhibited an inverse J-shape, indicating that understory regeneration was relatively good and with certain proportion of large-diameter trees. The main tree species were randomly distributed across the whole plot (=0.507) and in an intensively mixed state (=0.82). An average DBH comparison of trees in the stand indicated that they were at a intermediate status (=0.506). There was a differentiation among different dominances along the high intensity mixed dimension in the stand, indicating an optimal distribution of understory trees and the rational utilization of resources. Trees in the small diameter category were at a state of complete compression, while canopy trees were at a state of complete dominance in terms of their vertical space. Individuals of each dominant tree species were randomly scattered, with a random pattern of individuals throughout the climax community.

Effects of shading on chlorophyll content and photosynthetic characteristics in leaves of Phoebe bournei.

TANG Xing-lin, JIANG Jiang, JIN Hong-ping, ZHOU Chen, LIU Guang-zheng, YANG Hua

2019, 30(9):  2941-2948.  doi:10.13287/j.1001-9332.201909.002

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To explore the photosynthetic adaptation of Phoebe bournei to different light conditions, two-year-old P. bournei seedlings were grown under three light regimes (full light, shading rate 50% and 78% of full light). The chlorophyll contents, leaf gas exchange and chlorophyll fluorescence of P. bournei were measured after six-month treatment. The results showed that the contents of chlorophyll a, chlorophyll b, chlorophyll (a+b) and carotenoids in leaves were in a descending order of shading rate 78% > shading rate 50% > full light. There was no significant difference of chlorophyll a/b between natural and shade treatments. The shading treatment reduced light compensation point (LCP), but increased light saturation point (LSP) and apparent quantum yield (AQY), suggesting that plants could utilize both the weak light and the high light. Maximum net photosynthetic rate (P_{n max}), dark respiration rate (R_d), and maximum electron transfer rate (J_max) increased under the shading treatment. There was significant difference between natural and shade treatment in net photosynthetic rate (P_n), stomatal conductance to CO₂(g_sc), intercellular CO₂ concentration (C_i), and mesophyll conductance (g_m). P_n and g_m of different light regimes were sorted from the highest to the lowest as shading rate 78% > shading rate 50% > full light. g_sc under shading rate 78% was higher than that under full light. C_i under shading rate 50% and 78% were lower than that under full light. Actual photochemical efficiency of PSⅡ (F_v′/F_m′), quantum yields of PSⅡ (Φ_PSⅡ), and electron transport rate (J) of P. bournei leaves were significantly higher under shading rate 78% than those under shading rate 50% and full light. In conclusion, P. bournei could increase P_n by increasing chlorophyll content, AQY, J, g_sc, and g_m under shade condition.

Sampling time of living leaf for estimating phytolith-occluded organic carbon sequestration rate of Phyllostachys edulis.

HU Xiao-wei, HUANG Cheng-peng, HUANG Zhang-ting, JIANG Pei-kun, WU Jia-sen, ZHANG Yun-qing, SUN Kai, LIU Li-jun

2019, 30(9):  2949-2954.  doi:10.13287/j.1001-9332.201909.023

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Monthly phytolith-occluded organic carbon (PhytOC) content in living leaves and litterfall of Moso bamboo (Phyllostachys edulis) were measured for a year. The PhytOC sequestration rate in living leaves of different months were compared with that in annual litterfall to determine the optimum sampling time of living leaves for estimating PhytOC sequestration rate of Moso bamboo. The contents of phytoliths and PhytOC in living leaves of Moso bamboos were 23.45-101.07 g·kg^-1 and 0.73-1.98 g·kg^-1, respectively, with significant difference among different months. The monthly PhytOC sequestration rates of living leaves of Moso bamboo in different months ranged from 0.75 to 7.68 kg·hm^-2·a^-1. The maximum and minimum rates of the PhytOC sequestration occurred in December and April respectively, with significant difference between them. There was no difference between the PhytOC sequestration rate in living leaves of Moso bamboos in February or December and that of litterfall in the whole year. Therefore, February or December should be the optimal month of sampling living leaves for estimating the PhytOC sequestration rate of Moso bamboo stands.

Responses of seed germination and seedling growth of Cunninghamia lanceolata and Schima superba to different light intensities.

LIU Qing-qing, HUANG Zhi-jun, GUO Si, WANG Da-yang, WANG Chang-hui, WANG Zheng-ning, MA Xiang-qing, LIU Bo

2019, 30(9):  2955-2963.  doi:10.13287/j.1001-9332.201909.007

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Light is a key factor affecting seed germination and seedling growth. In this study, seed germination and seedling growth of Cunninghamia lanceolata and Schima superba were compared under controlled conditions with five light treatments (100%, 60%, 40%, 15% and 5% of full sunlight). The results showed that light intensity significantly impacted seed germination and seedling growth of both species. With decreasing light intensity, the germination rate and germination index of C. lanceolata increased, while those of S. superba showed a trend which increased first and then decreased, with the maximum at 40% light intensity. The seedling survival rate of both species was 0 under full sunlight, while significantly decreased with decreasing light intensity from 60% to 5%. Root length, basal stem diameter and height showed a consistent trend with the change of light availability in both species. Root length significantly decreased, basal stem diameter and height increased first and then decreased with decreasing light intensity, with the minimum at 5% light intensity. With decreasing light intensity, root biomass, stem biomass, leaf biomass and total biomass of C. lanceolata seedlings declined, while high biomass accumulation of S. superba seedlings were observed in 15%-60% light intensities, and lowest at 5% light intensity. Biomass accumulation in each organ of S. superba seedlings was greater than that of C. lanceolata seedlings under the same light intensity. High stem biomass and leaf biomass, low root biomass and root to shoot ratio were a phenotypic response to low light intensity in C. lanceolata and S. superba seedlings grown under poor light condition. The growth of C. lanceolata is better under relatively high light intensity than S. superba. Whereas S. superba is moderately shade-tolerant at the seedling stage, thus is more suitable for planting under closed canopy.

Effects of rainfall reduction on the quantity and spectroscopic characteristics of soil dissolved organic matter in a subtropical natural Castanopsis carlesii forest.

CHEN Ying-yi, SI You-tao, BAO Yong, CHEN Hui, LI Shuai-jun, QIAN Wei

2019, 30(9):  2964-2972.  doi:10.13287/j.1001-9332.201909.009

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The alteration of rainfall pattern under the background of global climate change may affect the quantity and quality of soil dissolved organic matter (DOM). To better understand the responses of soil DOM to rainfall reduction in subtropical forests, we conducted a 6-year rainfall reduction experiment. There were three treatments: control (CK), 30% rainfall reduction (-30%), and 60% rainfall reduction (-60%). With ultraviolet-visible, infrared and three-dimensional fluorescence spectroscopy, we investigated the effects of rainfall reduction on the quantity and structure of DOM from different soil layers of a natural Castanopsis carlesii forest in subtropical China. Rainfall significantly reduced the content of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in the 0-10 cm soil layer. Specifically, less decreases of DOC than DON were found under the -30% treatment, while more reduction of DOC than DON for the -60% treatment. Under each treatment, the contents of DOC and DON were significantly higher in the 0-10 cm soil layer than that in the 10-20 cm soil layer. Relatively more microbial metabolite with complex structures, such as aromatic humus and alkanes, contributed to soil DOM from the -30% treatment than that from the -60% treatment. Beyond water availability, microbial activity was a key factor regulating the quantity and structure of soil DOM in response to rainfall reduction.

Effects of ant nesting on soil microbial biomass carbon and quotient in tropical forest of Xishuangbanna.

CHEN Min-kun, WANG Shao-jun, CHEN Wu-qiang, CAO Run, CAO Qian-bin, WANG Ping, ZUO Qian-qian, ZHANG Zhe, LI Shao-hui

2019, 30(9):  2973-2982.  doi:10.13287/j.1001-9332.201909.036

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Ant nesting can modify soil physicochemical conditions in the tropical forest, exerting a crucial effect on spatiotemporal variation in soil microbial biomass carbon and quotient. In this study, the chloroform fumigation method was used to measure the spatiotemporal dynamics of microbial biomass carbon and quotient in ant nests and the reference soils in Syzygium oblatum community of tropical Xishuangbanna. The results were as following: 1) Microbial biomass carbon and quotient were significantly higher in ant nests (1.95 g·kg^-1, 6.8%) than in the reference soils (1.76 g·kg^-1, 5.1%). The microbial biomass carbon in ant nests and the reference soils showed a signifi-cantly unimodal temporal variation, whereas the temporal dynamics of microbial biomass quotient presented a distribution pattern of “V” type. 2) The microbial biomass carbon and quotient showed significant vertical changes in ant nests and the reference soils. The microbial biomass carbon decreased, and microbial biomass quotient increased significantly along the soil layers. The vertical variations in microbial biomass carbon and quotient were more significant in ant nests than in refe-rence soils. 3) Ant nesting significantly changed the spatiotemporal distributions of soil water and temperature in ant nests, which in turn affected spatiotemporal dynamics of soil microbial biomass carbon and quotient. Soil water content could explain 66%-83% and 54%-69% of the variation of soil microbial biomass carbon and quotient, respectively. Soil temperature could explain 71%-86% and 67%-76% of the variation of soil microbial biomass carbon and quotient in ant nests and the reference soils, respectively. 4) Changes in soil physicochemical properties induced by ant nesting had significant effect on the soil microbial biomass carbon and quotient. There were positive correlations of soil microbial biomass carbon to soil organic carbon, soil temperature, total nitrogen and soil water content, and to bulk density, nitrate nitrogen and hydrolyzed nitrogen; whereas a negative correlation of them was observed with soil pH. Soil pH was positively and other soil physicochemical properties were negatively correlated with microbial biomass quotient. Total organic carbon, total nitrogen and soil temperature had greater contribution to microbial biomass carbon, while total organic carbon and total nitrogen had the least negative effect on microbial biomass quotient. Therefore, ant nesting could modify microhabitats (e.g., soil water and soil temperature) and soil physicochemical properties (e.g., total organic carbon and total nitrogen), thereby regulating the spatiotemporal variation in soil microbial biomass carbon and quotient in tropical forests.

Effects of soil fauna on microbial community during litter decomposition of Populus simonii and Fargesia spathacea in the subalpine forest of western Sichuan, China.

LAN Li-ying, YANG Wan-qin, WU Fu-zhong, LIU Yu-wei, YANG Fan, GUO Cai-hong, CHEN Ya, TAN Bo

2019, 30(9):  2983-2991.  doi:10.13287/j.1001-9332.201909.033

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To understand the relationship between soil fauna and microorganism in the detrital food chain during litter decomposition, leaf litters of poplar (Populus simonii) and fargesia (Fargesia spathacea) in a subalpine forest of western Sichuan were taken as study objects. Phospholipid fatty acid (PLFAs) biomarker method was used to determine the effects of soil fauna on the abundance, structure and diversity of microbial community during the decomposition of leaf litter of two species from April 2016 to April 2018 with in situ control experiment. The results showed that the presence of soil fauna significantly affected the microbial PLFAs content during the decomposition of both species, reducing the PLFAs content in the first 240 days and increasing the PLFAs content in the 360 to 480 days. Soil fauna participation reduced the ratio of fungi to bacteria in the decomposition of poplar litter, and increased the ratio of gram-positive bacteria (G⁺) to gram-negative bacteria (G^-), which had the opposite effect on the ratio of fungi/bacteria and G⁺/G^- in the decomposition of fargesia litter. Microbial diversity and evenness maintained a high level in 120^th and 480^th days of the decomposition, and decreased sharply in 360^th and 720^th days of decomposition. Soil fauna participation significantly affected microbial diversity and evenness of poplar litter, but it had no signifi-cant effect on fargesia litter. The effects of soil fauna on the changes of litter PLFAs content were different with the decomposition days and tree species. The interaction between soil fauna and microbial community during litter decomposition in subalpine forest varied with seasons and tree species.

Effects of nitrogen supplementation on forage yield and quality of a degraded grassland in Hulunbuir, China.

LIU Zhuo-yi, WANG Xiao-guang, WEI Hai-wei, ZHANG Zhi-wei, YANG Guo-jiao, HU Yan-yu, LYU Xiao-tao

2019, 30(9):  2992-2998.  doi:10.13287/j.1001-9332.201909.003

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Long-term overuse of grasslands results in quantitative and qualitative decline of forage yield. Nutrient supplementation is a key strategy to improve forage yield. While mounting evidence showed that nitrogen (N) supplementation can increase forage yield, little is known about its impacts on forage quality. To understand the effects of N supplementation on forage quality at the community level, we carried out a field experiment in the meadow steppe of Hulunbuir. Our results showed that N supplementation significantly increased forage yield by 23%, which was mainly due to positive responses of perennial rhizomatous grass. The yield of other plant functional groups showed neutral response to N supplementation. The concentrations of crude protein, crude fat, and crude fiber varied significantly among different plant functional groups. Nitrogen supplementation significantly enhanced the concentration of crude protein in rhizomatous grass, bunchgrass, legume, and sedge. It enhanced the content of crude fat in rhizomatous grass but with no effect on other functional groups. Nitrogen supplementation had no effect on the concentration of crude fibre in all functional groups. At the community level, N supplementation significantly increased the concentrations of crude protein and crude fat. Our results are important for understanding the responses of forage production in meadow steppe under the scenarios of N enrichment.

Soil physical characteristics of shallow vadose zone and modeling its effects on upward capillary rise of groundwater in an arid-desert area.

ZHOU Hong, ZHAO Wen-zhi

2019, 30(9):  2999-3009.  doi:10.13287/j.1001-9332.201909.016

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Two typical soil profiles of sand dune (mixed sandy loam with sandy soil; uniform sandy soil) were selected from the arid region on the edge of the Badain Jaran desert to analyze soil physical characteristics. The effects of soil physical characteristics on capillary rise were monitored and simulated. The relationship between two typical soil profiles of sand dune and capillary rise were investigated to reveal the interactive processes among groundwater, capillary water, and soil water. Results showed that capillary rise was mainly affected by soil bulk density and soil clay content in the arid-desert area. The capillary rise could reach to 152 cm above shallow layer in the profile of mixed sandy loam with sandy soils, and 120 cm in the profile of sandy soil, respectively. Soil water distribution driven by the capillary rise was more uniform in the profile of sandy soil. Soil water content showed a diminishing trend from the groundwater to the maximum distance of capillary rise. In contrast, soil water distribution was markedly varied in the profile of mixed sandy loam with sandy soil. The process of capillary movement could be well simulated with Hydrus-3D model. Soil structure above the groundwater was the critical factor, which could affect the capillary rise and soil water distribution. However, the effects of soil in-season evaporation and plant root uptake on capillary rise movement need to be explored in further studies.

Responses of soil physicochemical properties and microbial characteristics to mowing and nitrogen addition in a meadow steppe in Inner Mongolia, China.

WANG Zhi-rui, YANG Shan, MA Rui-ao, WANG Ru-zhen, FENG Xue, LI Hui, JIANG Yong

2019, 30(9):  3010-3018.  doi:10.13287/j.1001-9332.201909.034

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Frequent mowing and nitrogen enrichment can lead to the degradation of grassland ecosystem. It remains largely unknown that how the soil microbial characteristics, important bio-indicators of soil quality, respond to mowing and nitrogen enrichment. In this study, using a field experiment established in the meadow steppe in Hulunber, Inner Mongolia, we explored the responses of soil properties, microbial biomass, soil respiration, and soil enzyme activities to mowing and nitrogen addition during growing seasons. Mowing significantly reduced microbial biomass carbon, nitrogen and phosphorus, and soil respiration (basal respiration and substrate induced respiration), which might be caused by the moisture- and carbon-limitation. Mowing significantly reduced activities of the enzymes involved in nitrogen acquisition (N-acetyl-β-D-glucosaminidase) and phosphorus acquisition (acidic phosphomonoesterases), which supports the resource allocation theory. Soil pH was significantly reduced by N addition. However, microbial biomass showed no significant response to nitrogen input, implying that soil acidification induced by nitrogen inputs was not profound enough to affect microbial biomass. Nitrogen addition did not affect soil respiration and microbial enzymatic activities, inconsistent with results from most of previous studies conducted in typical steppe. Combination of mowing and nitrogen addition reduced the activity of acidic phosphomonoesterases, which might be due to the increased phosphorus availability under the combined treatment. Combination of mowing and nitrogen addition reduced microbial biomass phosphorus, but increased soil available phosphorus, corresponding to the lowered activity of acidic phosphomonoesterases under the combined treatment. Microbial biomass carbon, nitrogen and phosphorus, and soil respiration peaked in July, which was associated with the high temperature and precipitation in summer. Soil enzymatic activities were higher in the spring and summer than in the late growing season. In summary, our results indicated that mowing would result in the imbalance of soil nutrients and intensify the risk of grassland degradation. In contrary, nitrogen addition exerted no effects on microbial biomass and activity.

Role of photosynthesis in regulating soil respiration under nitrogen application in a sandy grassland

LIN Li-tao, HAN Xiao-xiao, YU Zhan-yuan, SUN Xue-kai, HUANG Yue, ZENG De-hui

2019, 30(9):  3019-3027.  doi:10.13287/j.1001-9332.201909.012

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We examined the role of photosynthesis in regulating soil CO₂ emission under nitrogen enrichment in Keerqin sandy grassland. Results showed that nitrogen (N) application could affect soil respiration rate by altering the allocation of photosynthetic products to the belowground. Gross ecosystem photosynthesis rate (GEP) was positively correlated with soil respiration rate (R_s). Nitrogen application reduced slope of the fitting function from 0.236 to 0.161, with the equation intercept difference (0.51 μmol·m^-2·s^-1) being similar to the nighttime soil respiration rate increment (0.52 μmol·m^-2·s^-1). From May to October, the difference of photosynthetic rate (differential ratio) caused by nitrogen application was significantly correlated with that of soil respiration (differential ratio). Results from partial correlation confirmed the essential role of photosynthetic rate difference (ΔGEP) in driving soil respiration rate difference (ΔR_s) caused by nitrogen application. In the nighttime, soil respiration rate was affected by the aboveground vegetation activities in daytime. The daily mean GEP was an important factor affecting the nighttime soil respiration rate difference (ΔR_s) (P<0.01). Photosynthesis, rather than soil temperature, was the main factor affecting soil respiration rate difference (ΔR_s) under nitrogen application. Thus, the role of photosynthetic assimilation-regulating may provide a novel supplement for elucidating the responses of soil respiration to nitrogen enrichment.

Effects of rotational grazing methods on soil aggregates and organic carbon characteristics in desert steppe.

LU Qi, MA Hong-bin, YU Hong-qian, WANG Li, SHEN Yan, XU Dong-mei, XIE Ying-zhong

2019, 30(9):  3028-3038.  doi:10.13287/j.1001-9332.201909.010

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Reasonable rotation is of great significance to grassland management. We examined the distribution characteristics, stability, organic carbon content and contribution rate of 0-30 cm soil aggregates in the forbidding grazing, continuous grazing, and rotation in the two-paddock, four-paddock and six-paddock rotational districts in a desert steppe in Ningxia. The results showed that except for the forbidding grazing grassland that was dominated by mechanically stable large aggrega-tes, other water-stable aggregates were mainly composed of microaggregates. Increasing the rotational grazing zoning was conducive to maintain the content of water-stable aggregates in the surface soil and increase the content of large aggregates. The mechanical stability aggregate fractal dimension was the largest in continuous grazing, increased the fractal dimension of the rotation and shepherd partition to reduce the trend, but the fractal dimension of water-stable aggregates did not change. The average weight diameter (MWD) and geometric mean diameter (GMD) of the aggregates were the largest in the pastoral grassland and increased with the increases of the rotational grassland partition. MWD and GMD were negatively correlated with the microaggregate content. The organic carbon content in water-stable large aggregate was higher in the six-paddock rotational district and forbidding grazing, and the two-paddock rotational grazing and continuous grazing were lower. The contribution rate of micro-aggregates organic carbon to soil organic carbon content was higher in this region. In the 0-20 cm soil layer, the contribution rate of organic carbon in large aggregates increased with the increases of rotation. Considering the characteristics of soil aggregates and their organic carbon, the rotation of six-paddock was the most suitable method for rotational grazing in the desert steppe of the study area.

Responses of stoichiometric characteristics of rhizosphere soil to the degradation of alpine meadow.

MA Yuan, LI Lin-zhi, ZHANG De-gang, XIAO Hai-long, CHEN Jian-gang

2019, 30(9):  3039-3045.  doi:10.13287/j.1001-9332.201909.004

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This study aimed to understand the stoichiometric characteristics of carbon (C), nitrogen (N) and phosphorus (P) and soil nutrients in rhizosphere and non-rhizosphere soils and to obtain information on the status of soil and microbial nutrient limitation in degraded alpine meadow. We collected soil samples from rhizosphere (0-2 mm) of dominant plant species and non-rhizosphere (0-10 cm) of the alpine meadow with four different degraded degrees in the Qilian Mountains. We measured the concentration of C, N and P and extractable C, N, P (Ext-C, Ext-N, Ext-P), the activity and proportion of extracellular enzymes (β-1, 4-glucosidase, β-1, 4-N-acetylglucosaminidase, leucine aminopeptidase and acid phosphatase) involved in C, N, P cycles, as well as soil microbial biomass (MBC, MBN, MBP). The results showed that nutrient concentrations in the rhizosphere of dominant species was higher than that in non-rhizosphere. With the increases of degradation degree, soil C:N:P changed significantly, and resulted in a serious imbalance of C:N and severe N limitation. In the degraded alpine meadows, the ratio of log-transformed rhizosphere C-, N- and P-extracellular enzymes deviated from the 1:1:1 of global ecosystem, indicating that nutrient supply was mainly restricted by N and followed by P. The contents of soil total nutrients in degraded alpine meadow was relatively high, but the contents of soil available nutrients were low, which would hinder plant growth.

Effects of grazing intensity on spatial heterogeneity of the constructive species Stipa breviflora in desert steppe.

ZHANG Feng, CHEN Da-ling, ZHAO Meng-li, ZHENG Jia-hua, YANG Yang, QIAO Ji-rong, ZHAO Tian-qi

2019, 30(9):  3046-3056.  doi:10.13287/j.1001-9332.201909.006

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This study evaluated the changes of spatial distribution of the constructive species Stipa breviflora in the desert steppe under different grazing intensities (control, light, moderate, and heavy grazing) in Siziwang, Inner Mongolia. The small-scale spatial distribution of S. breviflora was measured. Results showed that population density of S. breviflora was following the order: heavy grazing (27.81 individuals·m^-2) > moderate grazing (22.17 individuals·m^-2) > control (11.31 individuals·m^-2) > light grazing (10.76 individuals·m^-2). The moderate and heavy grazing significantly increased population density of S. breviflora. According to the model fitting by semi-variance function, the population density of S. breviflora under the control, light, moderate and heavy gra-zing treatments were consistent with the exponential model, spherical model, exponential model and spherical model, respectively. Results from spatial distribution pattern analysis showed that structural ratio of S. breviflora population was control (99.7%) > heavy grazing (94.7%) > light grazing (92.7%) > moderate grazing (87.9%). Such a result indicated that the spatial autocorrelation of the four treatments was high, which were mainly affected by structural factors. In comparison, S. breviflora population structure ratio under moderate grazing treatment was the smallest, and partly affected by random factors. Based on fractal dimension analysis, spatial structure of the four treatments was good with simple spatial distribution. With the increases of grazing intensity, the spatial distribution was simpler and more homogeneous. Combined with 2D and 3D views, both light and heavy grazing changed spatial distribution of S. breviflora population from gradient distribution to patch distribution and resulted in the reduction of spatial heterogeneity.

Soil microflora characteristics under different vegetation patches in a desert steppe of Ning-xia, Northwest China.

DU Ya-xian, KANG Yang-mei, NIU Yu-bin, WANG Pan, YU Hai-long, ZHANG Zhen-shi, HUANG Ju-ying

2019, 30(9):  3057-3065.  doi:10.13287/j.1001-9332.201909.032

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Vegetation patch is one of the most basic characteristics of natural grazing grassland. To explore the effects of vegetation patch on soil microbial community, the changes of soil microbial biomass and community structure under four different vegetation patches in Ningxia desert steppe were quantified using phospholipid fatty acid (PLFA) analysis. The results showed that: 1) Soil microbial groups were abundant in vegetation patches, with the highest bacterial content, low fungal and actinomycete content, and the Gram-positive bacteria content being higher than that of Gram-negative bacteria in the patches of the four plant communities; 2) The total soil microbial biomass of Glycyrrhiza uralensis patch was significantly higher than that of Artemisia scoparia, Sophora alopecuroides, and Astragalus melilotoides patches; 3) Total PLFAs, Gram-positive bacteria, Gram-negative bacteria, fungi, anaerobic bacteria and fungi/bacteria were significantly positively correlated with soil organic C, and significantly negatively correlated with soil pH, indicating that soil organic C and pH were important factors affecting the growth and development of soil microorganisms in desert steppe.

Relationship between forest city landscape pattern and thermal environment: A case study of Longquan City, China.

LE Ke-jun, FANG Lu-ming, HE Xiao-bing, ZHENG Xin-yu

2019, 30(9):  3066-3074.  doi:10.13287/j.1001-9332.201909.017

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The differentiation characteristics of landscape pattern affect the urban thermal environment. In this study, temperature characteristics of nine types of landscape in a national forest city, Longquan City, were analyzed by temperature inversion method and spatial analysis. The landscape pattern analysis method was used to explore the correlation of landscape metrics and the thermal environment from 1 km to 3.5 km. The results showed that the high and sub-high temperature zones of Longquan City were distributed in northeast-southwest, mainly composed of urban and rural residential areas. The low and sub-low temperature zone were mainly distributed in the northwest and southeast areas, mainly composed of public welfare forests. By calculating the mean land surface temperature of each landscape type in the area below 700 m above sea level, the temperature of coniferous forest, broadleaf forest, conifer-broadleaf forest, bamboo forest and water was relatively low, whereas that of shrub land, other forest land, cultivated land and construction land was relatively high. Through the analysis of landscape pattern and thermal environment, it was found that the class pattern index was more practical than the landscape pattern index. The correlation between thermal environment effect and construction land distribution reached 0.835, coniferous forest land, broadleaf forest land, coniferous-broadleaf forest land and water were the second, up to -0.5 to -0.4. The cooling effects of different forest types vaied across different spatial scales. Broadleaved forests and coniferous-broadleaved forests were more conducive to cooling at large scales. The larger the area and volume stock of forest land, the more likely it had the lowest land surface temperature.

Spatial distribution characteristics and influencing factors of eco-environmental quality based on RS and GIS in Shiyang River Basin, China.

GUO Ze-cheng, WEI Wei, ZHANG Xue-yuan, LI Zhen-ya, ZHOU Jun-ju, XIE Bin-bin

2019, 30(9):  3075-3086.  doi:10.13287/j.1001-9332.201909.013

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Based on RS and GIS, 11 indexes from three aspects including natural capital, social pressure and economic supports were selected. The natural capital index (NCI), social pressure index (SPI), economic support index (ESI), and environment quality evaluation index (EQEI) were constructed by using spatial principal component analysis, variation coefficient method, and analytic hierarchy process. The spatial distribution characteristics and influencing factor of the environmental quality in Shiyang River Basin were analyzed. The results showed that the overall environmental quality was at poor level in Shiyang River Basin. The regions with better classes of environmental quality were mainly concentrated in the upper reaches of Qilian Mountains, and those with poorer classes were mainly concentrated in the middle-lower reaches of low hills land and desert. The EQEI value in Shiyang River Basin had polarization phenomenon from southwest to northeast. With the variation of distance, the value had large variation range, with obvious spatial heterogeneity. The environmental quality showed both high and low aggregation patterns, with "fault" distribution. There were highly clustered hot spots and highly clustered cold spots in the basin. Among the influen-cing factors of environmental quality, natural capital was the dominant one, social pressure was the second, and economic support was the least contributor.

Spatio-temporal evolution and influencing factors of inter-provincial green inclusive efficiency in China.

ZHAO Lin, WU Dian-ting, JIN Rui-he, WANG Qian

2019, 30(9):  3087-3096.  doi:10.13287/j.1001-9332.201909.020

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This study used Super-SBM model considering the undesirable outputs to measure inter-provincial green inclusive efficiency in China, analyzed the spatial and temporal changes and the influencing factors by panel Tobit model during 2000 to 2016. The results showed that green inclusive efficiency considering both social and eco-environmental factors was significantly lower than that only considering social factors. Green inclusive factors had significant impacts on the measurements. From 2000 to 2016, the inter-provincial green inclusive efficiency in China showed a trend of U-shaped evolution with obvious staged characteristics. The absolute and relative differences of green inclusive efficiency between provinces were expanding. China’s inter-provincial green inclusive efficiency showed an unbalanced spatial pattern. There were three high-efficient agglomeration areas in the whole country: Beijing-Tianjin, the Yangtze River Delta, and the Pearl River Delta. The low-efficient types were scattered in the southwestern, northwestern, northern China, as well as in the middle and lower reaches of the Yangtze River. To comprehensively improve green inclusive efficiency, it should take more measures by promoting the optimization and upgrading of industrial structure, upgrading the level of macro-control of local governments, optimizing the import and export structure, fully considering the role of the market, and improving the level of scientific and technological innovation.

Extracting method of tidal creek features under heterogeneous background at Yellow River Delta using remotely sensed imagery.

WANG Qi-wei, GONG Zhao-ning, GUAN Hong-liang, ZHANG Lei, JING Ran, WANG Xing

2019, 30(9):  3097-3107.  doi:10.13287/j.1001-9332.201909.019

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The Yellow River Delta exhibits irregular tidal flat, with tidal creeks that vary in width and experience tidal creek current anisotropy. Given such characteristics, the GF-2 multi-spectral image was selected as the data source to characterize the details of tidal creeks. First, the normali-zed difference water index (NDWI) and OTSU classification were used to delineate the wide tidal creeks. Second, the modified fuzzy C-means clustering algorithm (MFCM) and multi-scale Gaussian matching filter (MGMF) were used to enhance the narrow tidal creeks on the basis of weakening the heterogeneity of tidal flat background. Then, the adaptive threshold segmentation was conducted to delineate the narrow tidal creeks. Finally, the complete tidal creek networks were delineated by combining the wide and narrow tidal creeks. We fully used the spatial resolution and spectral information of the GF-2 image and took into account the geometric features of the linear features, ensuring the spatial continuity of the tidal creek extraction results. In the four tested areas, the Kappa coefficient was greater than 0.8 and the overall accuracy was greater than 97%, which performed better than the maximum likelihood method and support vector machine. The results showed that the proposed method could completely differentiate different types of tidal creeks, with good extraction accuracy and stability. The method could provide scientific reference for real-time dynamic monitoring of tidal creek and its development and evolution.

Improvement and application for ecological networks using landscape pattern and connectivity methods.

LIU Jun-jie, CHEN Jing-ru, LAI Yan-ni, LUO Bo-ya, ZHAO Fang, DU Qin

2019, 30(9):  3108-3118.  doi:10.13287/j.1001-9332.201909.014

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In landscape ecology, the target species ecological network is often constructed by the least-cost path model (hereafter LCPM) to improve landscape connectivity among discrete habitats and to mitigate the negative impacts of habitat fragmentation. Nevertheless, the traditional ecological network method based on LCRM has insufficient understanding of landscape structure changes and ecological processes of research site. We used landscape pattern index and connectivity probability index to quantitatively evaluate the landscape structure and connectivity characteristics of the research area before and after the construction of the ecological network. The ecological network of the habitat of Presbytis leucocephalus, located in Chongzuo, Guangxi Province, was used as an example to describe the optimization and application of this method in detail. We identified the habitat and stepping stone patches of the target species, classified land use types of the study area, set up different resistant values, and obtained 20 corridors of ecological network using LCPM. The results showed that LCRM could effectively improve habitat integrity and continuity, reduce overall fragmentation level, and improve habitat quality based on the structural and functional connectivity evaluation by landscape pattern index and connectivity probability index. Meanwhile, its construction could improve the structural connectivity and functional connectivity of the habitat landscape, with significant consistency of the connection degree changes in both aspects (R²=98.3%, P<0.01). However, the relationship between landscape structure changes and functional connectivity caused by the network was not strong, and their relationship was not as significant as the inherent relationship between the structure and function.

Dynamic evaluation of ecosystem integrity in Greater Khingan Range area, China.

LIU Qiong-yu, CHENG Quan-guo, WEI Jian-bing, GU Guang-he

2019, 30(9):  3119-3125.  doi:10.13287/j.1001-9332.201909.018

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The impacts of global climate change and human disturbance on terrestrial ecosystems has been expanding in intensity and scope. However, there is a lack of evaluation methods for large-scale heterogeneous landscape systems during ecosystem integrity assessment. From the perspective of landscape ecology, this study chose the indicators of landscape structure and landscape stability to comprehensively evaluate regional landscape change characteristics and ecosystem integrity dynamics of Greater Hinggan Mountains area using land use data and NPP data of 2005, 2010 and 2015 with GIS data processing and analysis platform. The results showed that Greater Hinggan Mountains area was dominated by forest land. The dominance degree of forest land was stable at 64.9%, which was much higher than the grassland that with the second dominance. The landscape diversity index was 0.59 in all three periods, accounting for 42.4% of the maximum value of landscape diversity index. Such a result indicated that the landscape resistance was stable in this area. From the view of landscape biomass, farmland and residential land had increased year by year, while forest area had decreased year by year, indicating that the effects of human disturbance on Greater Hinggan Mountains area were increasing.

Effects of irrigation amounts on soil CO₂, N₂O and CH₄ emissions in greenhouse tomato field.

CHEN Hui, SHANG Zi-hui, WANG Yun-fei, ZHU Yan, CAI Huan-jie

2019, 30(9):  3126-3136.  doi:10.13287/j.1001-9332.201909.024

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To understand the effects of different irrigation amounts on soil CO₂, N₂O, and CH₄ emission characteristics and tomato yield, and further put forward effective reduction measures, we carried out an experiment with three irrigation levels: full irrigation (1.0W, W_1.0; W meant irrigation amount needed to provide the adequate water), 20% deficit irrigation (0.8W, W_0.8) and 40% deficit irrigation (0.6W, W_0.6). We used static closed chamber and gas chromatography method to measure greenhouse gas emission in two consecutive greenhouse tomato rotation cycles from April to December, 2017. The results showed that cumulative soil CO₂, N₂O and CH₄ emissions increased with increasing irrigation amounts in the two growing seasons (W_1.0＞W_0.8＞W_0.6), and significant difference of N₂O between W_0.6 and W_1.0 was observed, while other treatment effects on soil gas emissions were not obvious. Compared to W_1.0, cumulative soil CO₂ emissions were decreased by 12.2% and 8.3%, cumulative soil N₂O emissions were decreased by 19.1% and 8.0%, and cumulative soil CH₄ emissions were reduced by 11.0% and 6.2% for W_0.6 and W_0.8, respectively. Tomato yield and global warming potential of soil N₂O and CH₄ emissions (GWP) increased as irrigation amount increasing. Compared with W_1.0, W_0.6 significantly decreased tomato yield by 17.0% and GWP by 22.9%, while the difference between the effects of W_0.8 and W_1.0 on these two parameters was not significant. Global warming potential per tomato yield presented an increase then a decrease as irrigation amount increasing (W_0.8＞W_1.0＞W_0.6), but without stanificance. Irrigation water use efficiency (IWUE) showed a decrease with increasing irrigation amount. Compared with W_1.0, IWUE under W_0.6 and W_0.8 was increased by 38.3% and 9.4%, respectively. Soil CO₂ flux was nega-tively and exponentially correlated with soil moisture. The dependence of soil CH₄ flux on soil moisture showed a significantly positive correlation. An exponential negative correlation was observed between the soil N₂O flux and soil temperature when soil temperature was below or above 18 ℃. Irrigation increased tomato yield and soil greenhouse gas emissions, but decreased IWUE. Therefore, W_0.8 was the best mode of irrigation management when synthetically considering tomato yield, IWUE, and greenhouse effect.

Effects of partial root-zone irrigation and rational close planting on yield and water productivity of cotton in arid area.

LUO Zhen, XIN Cheng-song, LI Wei-jiang, ZHANG Dong-mei, DONG He-zhong

2019, 30(9):  3137-3144.  doi:10.13287/j.1001-9332.201909.030

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The objective of this study was to evaluate the effects and underlying physiological mecha-nisms of partial root zone irrigation (PRI) and rational close planting, as well as their interaction on yield and water productivity (WP) of cotton and to explore new alternatives of water-saving irrigation in dry land areas. A factorial field experiment with irrigation mode (normal irrigation, partial root-zone irrigation and deficient irrigation) and plant population density (135000, 180000 and 225000 plants·hm^-2) was conducted in the west of Inner Mongolia to examine their effects on cotton growth, yield, water productivity and related physiological characters. The results showed that the irrigation mode and plant density as well as their interaction significantly affected the biomass, yield, yield components and harvest index. Under normal irrigation, the biomass and the number of bolls per unit area increased with the increasing of plant density, but the harvest index and boll weight significantly reduced. The yield of high plant density was comparable to that of medium plant density, both of which were increased significantly compared with that of low plant density. The content of abscisic acid (ABA) significantly increased and that of auxin (IAA) significantly reduced in cotton leaves under partial root-zone irrigation, which significantly increased the harvest index by improving the partitioning of assimilates to reproductive organs under partial root-zone irrigation. The number of bolls per unit area increased and boll mass remained unchanged with the increasing of density under partial root-zone irrigation. The yield of high density increased by 6.7% and 11.5% compared with that of medium and low density under partial root zone irrigation. The pre-frost seed cotton increased by 22.5%, the amount of irrigation reduced by 30%, and water productivity increased by 49.3% under partial root zone irrigation compared with that under normal irrigation at high plant density. Plant density did not affect photosynthetic rate (P_n) of functional leaves, but irrigation mode significantly affected P_n. Deficient irrigation significantly reduced the P_n of the main-stem functional leaves, but the P_n under partial root-zone irrigation was comparable to that of normal irrigation. The jasmonate (JA) content and the expression level of plasma membrane intrinsic protein (PIP) gene were significantly increased in the hydrated root under partial root-zone irrigation compared with those under normal irrigation. The results suggested that the increased JA content, as a signal molecule, up-regulated the expression level of PIP gene in dehydrated root and increased water uptake capacity of roots and guaranteed water balance of leaves, and then contributed to a relatively high P_n. Partial root-zone irrigation combined with relatively high plant density (225000 plants·hm^-2) is an important agronomic alternative for water saving in cotton plantation in the dry land areas.

Long-term effects of bio-organic fertilizer application on soil organic carbon pool and enzyme activity of cucumber continuous cropping.

QU Cheng-chuang, CHEN Xiao-min, ZHANG Zhi-long, WANG Nuo, LYU Jing-yan, ZHANG Jun, HUANG Chun-yan

2019, 30(9):  3145-3154.  doi:10.13287/j.1001-9332.201909.028

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The combination of field trial and indoor incubation experiment were conducted to examine the long-term effects of one-time application of bio-organic fertilizer on soil organic carbon (C) components, organic C mineralization, and enzyme activity in cucumber continuous cropping. Compared with CK, bio-organic fertilizer application significantly increased the content of soil organic C, activated C pool, slow-release C pool and inert C pool during four continuous cucumber planting seasons. With the increases of the number of consecutive crops, the proportion of soil inert carbon gradually increased. After four continuous seasons of cucumber planting, the cumulative and daily mineralization rate of soil organic C in the bio-organic fertilizer treatment increased by 17.3%-31.0% and 7.8%-43.0%, respectively. In the stage of cucumber ripening, bio-organic fertilizer application increased the activities of continuous soil urease, catalase, sucrose and neutral phosphatase by 10.5%-62.1%, 4.8%-25.5%, 3.9%-21.4% and 4.6%-66.4%. The activities of those four enzymes increased with the increases of the application amount of organic fertilizer. Results from the correlation and path analysis showed that the activity of the four enzymes were significantly correlated with the dynamics of organic carbon components in soil cucumber continuous cropping process. Soil urease and invertase activities significantly affected organic carbon mineralization during the continuous cropping process of cucumber. Application of bio-organic fertilizer could increase soil organic carbon content and enzyme activity, improve inert carbon ratio of soil organic carbon pools, cumulative and mineralization rate of organic carbon in continuous cropping process, thereby enhance soil carbon sequestration capacity.

Effects of drought stress on root development and physiological characteristics of sweet potato at seedling stage

WANG Jin-qiang, LI Huan, LIU Qing, XIANG Dan

2019, 30(9):  3155-3163.  doi:10.13287/j.1001-9332.201909.026

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The effects of drought stress on root morphology, endogenous hormones, chlorophyll fluorescence and active oxygen metabolism in three different stages of sweet potato rooting, branching and tubering stage were studied by sand culture method with 10% PEG-6000 simulating drought stress. The results showed that the biomass of sweet potato decreased significantly under drought stress in different periods, with the degree of drought stress being 10 days > 20 days > 30 days after transplantation. Drought stress significantly reduced the average diameter and root volume at the 10 days after transplantation, followed by the 20 days and 30 days. Both the main and interactive effects of different periods and drought stress significantly affected root morphological characteristics. Drought stress at different stages significantly reduced chlorophyll fluorescence characteristics, resulting in blocked photosynthate formation, and inhibited root differentiation. Drought stress affected the proportion of endogenous hormones in root (with decreases of indoleacetic acid and zeatin riboside contents but increases of abscisic acid contents) and thus inhibiting root differentiation of sweet potato. The earlier the stress time, the more serious the root differentiation of sweet potato was hindered. Across different drought-tolerant varieties, the severity of root differentiation blocked in Jishu 26 was significantly lower than that in Guangshu 87. Root endogenous hormones and chlorophyll fluorescence were the key drivers for the average diameter and root volume (R₁=0.936, R₂=0.972). Zeatin riboside, maximal photochemical efficiency, and abscisic acid had greater direct effects on average diameter and root volume of sweet potato. Sweet potato was more sensitive to drought stress in the 10th day after transplanting. Therefore, proper irrigation should be considered in case of drought in seedling stage of sweet potato.

Plant growth and Cd accumulation characteristics in different planting modes of maize and Amaranthus hypochondriacus.

GUO Nan, CHI Guang-yu, SHI Yi, CHEN Xin

2019, 30(9):  3164-3174.  doi:10.13287/j.1001-9332.201909.038

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To achieve the goal of remediation while producing for farmland contaminated by Cd, maize and grain amaranth (Amaranthus hypochondriacus) were planted on farmland contaminated by Cd in five different intercropping modes, including alternating wide-narrow-row of maize and single-row grain amaranth intercropped between wide rows (T₁), alternating wide-narrow-row of maize and double-row grain amaranth intercropped between wide rows (T₂), equidistant double-row maize and single-row grain amaranth intercropped between rows (T₃), equidistant double-row maize and double-row grain amaranth intercropped between rows (T₄), maize and grain amaranth intercropped with equal four rows (T₅), while maize (CK₁) and grain amaranth (CK₂) single planted as control to explore the effects of different intercropping modes on growth and Cd accumulation of crops and hyper-accumulation plants (A. hypochondriacus). The results showed that: 1) Compared with mono-culture (CK₁), grain yield of maize per plant showed an increasing trend in intercropping modes. The grain yield of maize in T₁ increased by 10.5%, while that in T₄ and T₅ decreased by 6.3% and 5.4% respectively, and that in T₂ or T₃ did not change compared with monoculture of maize. The aboveground biomass per plant and yield per unit area of grain amaranth decreased by 69.5%-95.7% and 83.9%-96.9% in intercropping modes respectively compared with monoculture (CK₂). 2) The Cd content of maize grain showed an increasing trend in intercropping modes compared with monoculture (CK₁). The Cd content of grain amaranth showed a decreasing trend in intercropping modes compared with monoculture (CK2). 3) Compared with monoculture (CK2), the enrichment coefficient, transport coefficient, and effective transport coefficient of grain amaranth all showed an increasing trend in intercropping modes, while the aboveground Cd extraction amount per plant and per unit area of grain amaranth decreased by 40.4%-86.7% and 70.4%-88.9% in intercropping modes, respectively. The total amount of Cd extraction per unit area of maize and grain amaranth in intercropping modes was significantly higher than that in monoculture of maize and lower than that in monoculture of grain amaranth. 4) The content of available Cd in maize rhizosphere soil and the content of total/available Cd in grain amaranth rhizosphere soil both showed an increasing trend in intercropping modes compared with monoculture of both crop, but it had no significant effect on non-rhizosphere soil. In this study, T₁ was beneficial to increase maize grain yield, while T₅ was beneficial to maximize the Cd extraction amount of grain amaranth.

Effects of combined red, blue and white LED light on the quality of eggplant seedlings and fruit peels.

DU Yu-fen, GAO Zhi, DI Qing-hua, YANG Feng-juan, WANG Xiu-feng, WEI Min, MI Qing-hua, LI Yan

2019, 30(9):  3175-3182.  doi:10.13287/j.1001-9332.201909.027

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The effects of red/blue=3/1 [R/B=3/1(9/3), as control, CK₁], white light (W, as control, CK₂), and combined light of red, blue and white [R/B/W=3/1/1 (9/3/3), T₁; R/B/W=9/3/8, T₂; R/B/W=3/1/6 (9/3/18), T₃; R/B/W=3/1/16 (9/3/48), T₄] on the growth, root development, quality and yield of eggplants were examined to provide theoretical and technical support for intensive and high-efficient light supplement and eggplant seedlings cultivation, using LED to accurately regulate light environment and ‘Gailiangdalong’ eggplant, based on the previous findings of the benefits of R/B=3/1 to the cultivation of eggplant seedlings. The results showed that R/B/W=9/3/8 treatment significantly increased plant height, stem diameter, seedling index, shoot dry weight, root dry weight, root development, anthocyanins and flavonoids content in eggplant peels and early yield. Root/shoot, total phenolic content in eggplant peels and soluble sugar content in pulps under R/B/W=3/1/1 treatment were significantly higher than those of other treatments. Total leaf area and free amino acid content in pulps were higher under R/B/W=3/1/6 treatment. The soluble protein content in pulps was higher under R/B/W=3/1/16 treatment. In summary, combined LED light of red, blue and white could improve the quality of eggplant seedlings and the yield and quality of eggplant fruits, with R/B/W=9/3/8 treatment being the best one in our study.

Responses of soil organic carbon and microbial community structure to different tillage patterns and straw returning for multiple years.

FU Min, HAO Min-min, HU Heng-yu, DING Wen-chao, ZHAI Ming-zhen, ZHANG Hai-yi

2019, 30(9):  3183-3194.  doi:10.13287/j.1001-9332.201909.039

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Soil organic carbon is essential for maintaining terrestrial ecosystem function and mitigating soil degradation. Soil microorganisms participate in soil carbon cycling. They are affected by tillage methods and straw returning. A split-plot design was adopted in this experiment. The whole-plot treatment had two tillage methods, subsoil tillage (ST) and rotary tillage (RT). The split-plot treatment included full straw returning (F) and no straw returning (0). The microbial community structure and carbon sequestration genes were assessed by Illumina sequencing technique. Soil organic carbon contents were measured during 2012-2017. The results showed that 1) subsoil tillage and straw returning significantly increased pH, microbial biomass carbon, total nitrogen, silt content, and clay content, while significantly decreased sand content; 2) during the test period (2012-2017), soil organic carbon (SOC) content under all treatments showed an increasing trend, but the increment for average SOC content under straw returning and subsoiling treatments was significantly higher than that of no straw returning and rotary tillage by 33.2 % and 30.6%, respectively; 3) Proteobacteria was the most abundant type of bacteria in the soil, followed by Acidobacteria and Gemmatadanetes; 4) STF treatment maintained high microbial diversity; 5) Excepted for soil sand content, soil pH, microbial biomass carbon, total nitrogen, silt content and clay content all caused the variation of soil microbial community structure under the STF treatment in the direction of SOC accumulation; 6) in addition to the gene abundance in the di- and oligosaccharides metabolic pathway, the gene abundance in the metabolic pathways for CO₂ fixation, central carbohydrate metabolism, fermentation, one-carbon metabolism, organic acids, sugar alcohols and glycoside hydrolases showed that subsoil tillage was significantly higher than rotary tillage, with posi-tively correlation with soil organic carbon content. Therefore, the combination of subsoil tillage and straw returning could improve basic soil properties, affect soil microbial community structure, and increase the capacity of soil carbon fixation, thus providing a realistic basis for solving soil degradation.

Growth-promotion and disease control effects on chili and eggplant by arbuscular mycorrhizal fungi and plant symbiotic actinomycetes

NING Chu-han, LI Wen-bin, ZHANG Chen, LIU Run-jin

2019, 30(9):  3195-3202.  doi:10.13287/j.1001-9332.201909.037

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Arbuscular mycorrhizal fungi (AMF) or plant symbiotic actinomycetes (PSA) play an important role in stimulating plant growth, antagonizing pathogens, tolerating stress, and controlling plant disease. However, whether there is a synergistic effect between AMF and PSA in promoting plant growth and controlling disease is worth exploring. The aim of this study was to evaluate the effects of AMF and PSA on growth-promotion and controlling disease on Solanaceae vegetables and to obtain effective AMF+PSA combinations. Under greenhouse pot conditions, chili (Capsicum annu-um, cultivar: Yangjiaojiao) and eggplant (Solanum melongena, cultivar: Heiguanchangqie) were inoculated with or without AMF Funneliformis mosseae (Fm), Glomus versiforme (Gv), PSA Streptomyces globosus H6-1, Streptomyces rochei S2-2, Streptomyces coralus D11-4 or/and pathogenic fungi Botrytis cinerea. There were a total of 48 treatments. The growth, disease and root symbiont development of plants were determined. The results showed that Fm and PSA could promote each other’s colonization, while Gv and PSA inhibited each other. Compared with the control, AMF, PSA and AMF+PSA improved the photosynthetic performance, root activity, and growth of chili and eggplant. Under the condition of inoculation with pathogenic fungi, AMF and/or PSA treatment significantly increased growth and reduced the disease index of plants, with the effects of PSA being greater than that of AMF. Fm+H6-1 combination had the best effect on the growth-promotion and controlling disease of chili plants, with the controlling effect on gray mold reaching 69.1%. Fm+ D11-4 had the best effect on the growth promotion and controlling disease of eggplant, the controlling effect of which on gray mold reached 75.5%. Fm+H6-1 andFm+D11-4 were efficient combinations of chili and eggplant for promoting growth and controlling disease under the conditions of this experiment. Further tests in field are needed.

Suitability of human settlement environment in Buyei traditional villages in rocky desertification area of Guizhou, China.

ZHANG Yuan-bo, HUANG Zong-sheng, CHEN Xuan, GUO Xiao-lan, FENG Wei-wei, LIU Yi-fu, PANG Min, FANG Yin

2019, 30(9):  3203-3214.  doi:10.13287/j.1001-9332.201909.015

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To investigate the traditional village living environment adaptability to desertification and topography, the suitability evaluation index system and weight of traditional Buyei traditional villages in the rocky desertification area human settlement were quantified using Delphi method and comprehensive weighting method. We calculated human settlements environment suitability value and threshold to comprehensively analyze the human settlements environment suitability. The results showed that 10% of the traditional Buyei traditional villages were located in the rocky desertification areas with high intensity and extremely high intensity and had the tradition of selecting the best environment. The index system of residential environment suitability was composed of five first-level indices (economy, historic culture, ecology, society, and building environment suitability) and 26 second-level indices. This index system was applicable to villages in karst regions. The comprehensive environmental suitability value (2.81-3.77), the economy value (0.77-1.17), the historic culture value (0.39-0.50), the ecology value (0.83-1.07), the social environment value (0.38-0.53) all decreased with the increasing intensity of rocky desertification, but the suitability value of building environment did not change, which ranged from 0.43 to 0.51. Rocky desertification had profound and synergistic impacts on economy, historic culture, ecology and social environment. The floor level of the human settlement suitability threshold was 2.93. If the threshold was lower than 2.93, it could be considered to move or take measures to improve its value. The suitability value (3.56) of traditional village living environment in mountain slope was higher than that in depression (3.42) and valley (3.16). The human settlement suitability of traditional villages in rocky desertification area was higher than that of ordinary villages, but was lower than that of normal landform, with the differences in economy and ecology being the main reasons. To improve the living environment of traditional villages in rocky desertification areas, we should strengthen the comprehensive control of rocky desertification and policy support, develop ecological economy and tourism, protect historic culture or choose ecological migration. This research could provide theoretical base for the planning and construction of village living environment protection in karst areas.

Adsorption of Cd²⁺ from wastewater by modified fly ash.

HUANG Xun-rong, ZHAO Hang-hang, ZHANG Gui-bin, LI Jing-tian, JI Pu-hui

2019, 30(9):  3215-3223.  doi:10.13287/j.1001-9332.201909.040

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The modified fly ash (MFA) was prepared through roasting the mixture of fly ash and NaOH/Ca(OH)₂ at 250 ℃ for 1.5 h. The physicochemical properties of MFA were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), surface area analyze (BET), and Fourier transform infrared spectroscopy (FTIR) techniques. Results from BET analysis showed that the BET of MFA was enlarged by 20.6 times compared with FA. Results from SEM analysis showed that the glass phase was dissolved, with a rough surface and porous structure. Results from FTIR analysis demonstrated that -OH played an important role in Cd²⁺ adsorption. Results from the static adsorption experiment revealed that the removal efficiency of Cd²⁺ reached 97.3% when 0.2 g MFA was applied while the concentration of Cd²⁺ was 100 mg·L^-1, the solution pH was 7.0, the adsorption temperature was 25 ℃ and the adsorption time was 90 min. In addition, the coexisting cations (K⁺, Na⁺, Mg²⁺, and Ca²⁺) might inhibit Cd²⁺ adsorption. Among all the cations, Ca²⁺ showed a most significant inhibitory effect on the removal of Cd²⁺. Langmuir isotherm and the pseudo-second-order kinetic models could well describe the adsorption behavior of Cd²⁺ on MFA, with the maximum adsorption capacity of 55.77 mg·g^-1. Meanwhile, thermodynamic studies showed that Cd²⁺ adsorption onto MFA was spontaneous and endothermic process. MFA had better adsorption capacity than FA and had certain application pro-spects in wastewater treatment.

Improvement effects of quicklime and calcium magnesium phosphate fertilizer on acidified soil cultivating Codonopsis tangshen.

ZHOU Wu-xian, HE Yin-sheng, ZHU Ying-hui, ZHANG Mei-de, DUAN Yuan-yuan, HUANG Da-ye, XU Da-bing, AI Lun-qiang

2019, 30(9):  3224-3232.  doi:10.13287/j.1001-9332.201909.008

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To solve the problem of soil acidification in the cultivation of Codonopsis tangshen, laboratory experiments were carried out to investigate C. tangshen seed germination, seedling growth and soil exchangeable acid, microbial community structure after applying quicklime (QL) and calcium magnesium phosphate fertilizer (CMP). The results showed that QL and CMP treatments significantly improved the survival rate of C. tangshen seedlings from 147.7% to 326.7% and from 270.1% to 311.2%, respectively. The maximum increase rates of the height of C. tangshen seedlings were 516.7% and 546.3%, and that of root length were 798.0% and 679.2% in the treatments of QL and CMP, respectively. 1‰-4‰ QL or CMP treatments increased the relative chlorophyll content, antioxidant enzyme activity and the content of soluble protein of C. tangshen seedlings, decreased the content of malondialdehyde and superoxide anion radical of seedlings, increased soil pH by 0.88-2.02 units and 0.23-1.19 units, and decreased the exchangeable aluminum content in soil by 53.0%-95.3% and 17.6%-81.3%, respectively. Soil bacterial and actinomycetic abundances were significantly higher in 2‰-4‰ QL or CMP treatments than that in the control. Soil fungal abundance was significantly lower in the QL treatment of 2‰ and CMP treatment of 4‰. 1‰-4‰ QL or CMP treatments significantly increased fresh weight of C. tangshen tubers by 40.5%-78.5% and 28.4%-78.8%, respectively. In conclusion, the suitable quantity of QL and CMP for acidified soil (pH=4.12, ρb=1.15 g·cm^-3, tillage layer=15 cm) amendment were 1.73-3.45 t·hm^-2 and 3.45-6.90 t·hm^-2, and QL and CMP amendment could fit the optimum soil pH (5.5-6.5) for the growth of C. tangshen seedlings.

Spatio-temporal variations of functional diversity of fish communities in Haizhou Bay.

ZHANG Xiao-zhuang, WANG Jing, XU Bin-duo, ZHANG Chong-liang, XUE Ying, REN Yi-ping

2019, 30(9):  3233-3244.  doi:10.13287/j.1001-9332.201909.035

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As the link among species, ecological environment, and ecosystem function, functional diversity can help us to better understand the relationship between biodiversity and ecosystem function. We analyzed functional diversity with thirteen functional traits reflecting the characteristics of food acquisition, locomotion, ecological adaptation, reproduction and population dynamics of fish species. The seasonal, interannual and spatial variations of functional diversity of fish communities were examined using functional richness index (FRic), functional evenness index (FEve), functional divergence index (FDiv) and community weighted mean index (CWM) based on the data from the bottom trawl surveys in spring and autumn from 2011 to 2017 (except 2012) in Haizhou Bay. The results showed that functional diversity indices were significantly different in spring and autumn, with FRic was significantly higher in autumn than that in spring and FDiv was significantly higher in spring than that in autumn. Migration might be the main reason for the seasonal change of functional diversity indices. CWM analysis showed that dominant fish species were cold-temperate or warm-temperate species, with higher trophic level, strong motion ability, and relatively high growth coefficient, resilience and vulnerability in spring. In autumn, the dominant species showed the opposite traits. In both spring and autumn, fish species with pelagic eggs dominated the fish communities. Inter-annual variations in functional diversity indices were observed in spring and autumn. The functional diversity indices showed an annual fluctuation during the study period in both spring and autumn, indicating the low stability of fish community in Haizhou Bay. Significant spatial changes in functional diversity of fish assemblages were observed, with FDiv being higher in the offshore coastal waters (>20 m) than that in the shallow waters (<20 m). The functional diversity showed obvious spatio-temporal variation. The ecological niches and resource utilization of fish species varied with season, year and space in Haizhou Bay.

Stability of biochar and the mechanisms underlying its response to mineral modification: A review.

GAO Cheng-xiang, LIU Yu-xue, WANG Yu-ying, LYU Hao-hao, HE Li-li, YANG Xue-yun, YANG Sheng-mao

2019, 30(9):  3245-3251.  doi:10.13287/j.1001-9332.201909.029

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Biochar, with high degree of carbon stability, is considered as a kind of carbon sequestration material that can effectively alleviate the greenhouse effect. It is of great significance for carbon sequestration and mitigation to develop biochar with high carbon retention and stability. Mineral modification can regulate the stability of biochar. However, the relevant research has not received enough attention, and the underlying mechanism is not very clear. Firstly, the evaluation indices of biochar stability were summarized, mainly including H/C atomic ratio, O/C atomic ratio, coefficient of stability R₅₀, volatile-matter content, thermal weight loss rate of carbon, carbon (chemical) oxidation loss rate, and cumulative CO₂ emission of microbial mineralization. Then, based on the analysis of impact factors of biochar stability (such as raw material type, carbonization condition, external environment, etc.), we reviewed research progress about the effects of mineral modification on biochar stability. Furthermore, possible mechanisms of both enhancement and weakening effects on biochar stability were put forward. Enhancement is mainly due to the effects of physical barrier of minerals and the organic mineral complex formed by the interaction of mineral and biochar. While weakening effect is mainly due to special mineral composition, such as the Fe-bearing mineral composition, which promotes the thermal decomposition of biochar at high temperature. Finally, future research directions were proposed, in order to promote the development of carbon sequestration technology of biochar and provide technical support and theoretical basis for obtaining more stable biochar.

Research advances on the pollution of pharmaceutical and personal care products (PPCPs) in natural waters and their toxicity to freshwater algae.

DING Teng-da, LI Wen, KAN Xiao-lin, LI Ju-ying

2019, 30(9):  3252-3264.  doi:10.13287/j.1001-9332.201909.031

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The continuous discharge of pharmaceutical and personal care products (PPCPs) into aquatic environment and their potential threaten to ecological environment or human health has received more and more attention all over the world. Algae are primary producers in aquatic environment and play an important role in ecosystem balance and stabilization. In this review, the concentrations of PPCPs in natural waters from different countries and regions are introduced to demonstrate their characteristics of pollution in aquatic environment. Furthermore, we reviewed some progresses on the toxicity, bioaccumulation and ecological risk of PPCPs. We introduced the toxicity effect and mechanism of PPCPs to algae, the bioaccumulation of PPCPs in algae, as well as the ecological risks of PPCPs in surface water. The review will provide references for development of PPCPs related criteria and assessment of ecological risks in aquatic environment.