Table of Content

15 January 2022, Volume 33 Issue 1

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Drought tolerance traits of leaves of 20 tree species in temperate forest of Northeast China

WANG Le-le, ZHOU Zheng-hu, JIN Ying, WANG Chuan-kuan

2022, 33(1):  1-8.  doi:10.13287/j.1001-9332.202201.003

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The increases in frequency and intensity of drought worldwide has seriously affected tree growth, and even led to widespread forest mortality. Leaf traits estimated from pressure-volume (PV) curve provide key leaf physiological information that reflects the drought tolerance of trees. However, it is uncertain that which PV parameter performs the best at local scale. Here, we measured five PV traits (including TLP, π₀, ε, C_leaf, and RWC_tlp) and two leaf structural traits (specific leaf area and leaf density) in 20 tree species (16 angiosperms and 4 gymnosperms) in a temperate mixed forest at the Maoershan Forest Ecosystem Research Station, Northeast China. The objectives of this study were to search the best indicators of leaf drought tolerance at local scale, and to explore the correlation between PV traits and leaf structural traits. We found that angiosperms had significantly greater RWC_tlp and lower C_leaf than gymnosperms, indicating that RWC_tlp and C_leaf might be the good indicators of leaf drought tolerance in temperate mixed forest in Northeast China. Within angiosperm species, TLP and π₀ were significantly and negatively correlated with leaf density, but positively correlated with specific leaf area; while ε was negatively correlated with specific leaf area. However, the opposite trends between PV traits and leaf structural traits were observed between gymnosperms and angiosperms, which might be attributed to their differences in drought response and adaptation strategies.

Comparison of artificial neural network with compatible biomass model for predicting aboveground biomass of individual tree

LIANG Rui-ting, WANG Yi-fu, QIU Si-yu, SUN Yu-jun, XIE Yun-hong

2022, 33(1):  9-16.  doi:10.13287/j.1001-9332.202201.001

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Forest biomass is an important index in forest development planning and forest resource monitoring. In order to provide a more efficient and low-biased method for estimating individual tree biomass, we introduced artificial neural network here. We used the data of aboveground biomass of 101 Larix olgensis trees harvested from the Dongzhelenghe Forest Farm in Heilongjiang Province to develop four aggregation model systems (AMS), based on different combination of the variables (diameter at breast height, tree height, crown width). The weighted functions were used to eliminate heteroscedasticity. Then, we trained artificial neural network (ANN) biomass model based on the optimal combination. The models were tested by the leave-one-out cross-validation method to compare the accuracy of the two biomass estimation methods. The results showed that biomass model based on only one variable, diameter at breast height, could accurately estimate the biomass of L. olgensis. Adding two indices, tree height and crown width, could improve the fitting performance of models, with AMS4 performing the best among the four addictive model systems. The biomass models developed by the two methods both could estimate biomass at tree level accurately, with the coefficient of determination (R²) of each component was higher than 0.87. Compared with the AMS4, R² of leaf biomass model was about 0.05 higher, and that of other organs were also about 0.01 higher in artificial neural network model system. In addition, the root mean square error (RMSE) and other indicators were also significantly smaller. For example, the RMSE of tree stem and aboveground biomass were smaller by 2.135 kg and 3.908 kg, respectively. The model's validation statistics mean relative error (MRE) performed better. In general, ANN was a flexible and reliable biomass estimation method, which was worthy consideration when predicting tree component biomass or aboveground biomass.

Effects of radiation changes on net ecosystem exchange of carbon dioxide in a middle subtropical Chinese fir plantation

PENG Li, ZHAO Zhong-hui, XIANG Wen-hua, DENG Xiang-wen, OUYANG Shuai

2022, 33(1):  17-24.  doi:10.13287/j.1001-9332.202201.006

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Total solar radiation is an important factor affecting carbon exchange in forest ecosystem. In order to understand the effects of radiation change on carbon exchange in Chinese fir plantation, long-term monitoring data of carbon dioxide flux and meteorological factors measured by open eddy covariance system and meteorological gradient observation system were used in this study. The clearness index (k_t) was used to represent the condition of solar radiation. We analyzed the effects of k_t on net ecosystem exchange of carbon dioxide (NEE) in the central subtropical Chinese fir plantation during the growing season (from April to October). The results showed that total solar radiation in clear sky was usually higher in the morning than that in the afternoon, and that NEE was lower in the morning than in the afternoon. Such difference in NEE reached the maximum when the solar elevation angle was about 50°. At the medium k_t(0.42-0.52), carbon absorption of Chinese fir plantation was the strongest. The ave-rage maximum relative change of NEE in 10 years in different solar elevation angles ranged from 11.0% to 29.4%, while the minimum and maximum critical values appeared at 35°-40° and 45°-50°, respectively. When k_t was at the moderate degree due to the existence of clouds, carbon absorption and diffuse photosynthetically active radiation of Chinese fir plantation reached the maximum, and the latter might be the main reason for the former. Moderate radiation condition with the presence of cloud clould promote NEE of Chinese fir plantation and lead to largest carbon absorption.

Effects of short-term combined application of ammonium nitrogen and nitrate nitrogen on the growth and leaf traits of Machilus pauhoi seedlings

YANG Ting, ZHONG Quan-lin, LI Bao-yin, CHENG Dong-liang, XU Chao-bin, ZHOU Yu-xing, ZHANG Xue, ZHOU Zong-zhe

2022, 33(1):  25-32.  doi:10.13287/j.1001-9332.202201.026

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Trees are characterized with selective absorption of different forms of nitrogen. Ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^--N) are the main forms of nitrogen for plant absorption. We examined the differences of absorption between NH₄⁺-N and NO₃^--N for 1-year-old Machilus pauhoi seedlings planted in local hilly red soil in a pot experiment. A controlled experiment with 7 different NH₄⁺-N/NO₃^--N treatments was conducted, to study the effects of nitrogen forms and different NH₄⁺-N/NO₃^--N ratios on the growth and leaf traits of M. pauhoi seedlings. The results showed that there were no significant differences in the relative growth rate of ground diameter (GD), plant height (TH), and biomass (RGR) of M. pauhoi seedlings with different NH₄⁺-N/NO₃^--N ratios for four months, but these parameters were relatively high under the treatment of NH₄⁺-N:NO₃^--N=5:5. The seedlings of M. pauhoi didn't show obvious preference for NH₄⁺-N and NO₃^--N in short term. The extremely low NH₄⁺-N/NO₃^--N ratio application was unsuitable for their growth. Different NH₄⁺-N/NO₃^--N application had significant effects on leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf relative water content (LRWC), net photosynthetic rate (P_n), intercellular CO₂ concentration (C_i), water use efficiency (WUE), and photosynthetic nitrogen use efficiency (PNUE). M. pauhoi seedlings under the treatment of NH₄⁺-N:NO₃^--N=1:9 had the highest LA, SLA, P_n, WUE and PNUE. However, the seedlings under the treatment of NH₄⁺-N:NO₃^--N=9:1 had the lowest LDMC, leaf tissue density (LTD), LRWC and C_i. Different NH₄⁺-N/NO₃^--N combined application did not affect leaf nitrogen content (LN) and leaf phosphorus content (LP), which were highest under the treatment of NH₄⁺-N:NO₃^--N=5:5. Across different NH₄⁺-N/NO₃^--N combined treatments, GD, TH, and RGR were significantly negatively correlated with SLA, while both GD and RGR were significantly negatively correlated with PNUE. Our results could provide theoretical basis for precise nutrient management and high-efficiency cultivation techniques during the seedling stage of the M. pauhoi.

Soil enzyme stoichiometry revealed the changes of soil microbial carbon and phosphorus limitation along an elevational gradient in a Pinus taiwanensis forest of Wuyi Mountains, Southeast China

LIN Hui-ying, ZHOU Jia-cong, ZENG Quan-xin, SUN Jun, XIE Huan, LIU Yuan-yuan, MEI Kong-can, WU Yue, YUAN Xiao-chun, WU Jun-mei, SU Xian-chu, CHENG Dong-liang, CHEN Yue-min

2022, 33(1):  33-41.  doi:10.13287/j.1001-9332.202201.033

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Understanding changes in soil enzyme activities and ecoenzymatic stoichiometry is important for assessing soil nutrient availability and microbial nutrient limitation in mountain ecosystems. However, the variations of soil microbial nutrient limitation across elevational gradients and its driving factors in subtropical mountain forests are still unclear. In this study, we measured soil properties, microbial biomass, and enzyme activities related to carbon (C), nitrogen (N), and phosphorus (P) cycling in Pinus taiwanensis forests at different altitudes of Wuyi Mountains. By analyzing the enzyme stoichiometric ratio, vector length (VL), and vector angle (VA), the relative energy and nutrient limitation of soil microorganisms and its key regulatory factors were explored. The results showed that β-glucosaminidase (BG) activities increased along the elevational gradient, while the activities of β-N-acetyl glucosaminidase (NAG), leucine aminopeptidase (LAP), acid phosphatase (AcP) and (NAG+LAP)/microbial biomass carbon (MBC) and AcP/MBC showed the opposite trend. Enzyme C/N, enzyme C/P, enzyme N/P, and VL were enhanced with increasing elevation, while VA decreased, indicating a higher degree of microbial P limitation at low elevation and higher C limitation at high elevation. In addition, our results suggested that dissolved organic carbon and microbial biomass phosphorus are critical factors affecting the relative energy and nutrient limitation of soil microorganisms at different elevations. The results would provide a theoretical basis for the responses of soil carbon, nitrogen, and phosphorus availability as well as the relative limitation of microbial energy and nutrition to elevational gradients, and improve our understanding of soil biogeochemical cycle process in subtropical montane forest ecosystems.

Effects of nitrogen addition on soil microbial biomass and enzyme activities of Pinus massoniana-Quercus variabilis mixed plantations in the Three Gorges Reservoir Area

WANG Li-jun, CHENG Rui-mei, XIAO Wen-fa, SUN Peng-fei, SHEN Ya-fei, ZENG Li-xiong, CHEN Tian

2022, 33(1):  42-50.  doi:10.13287/j.1001-9332.202201.034

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We examined the effects of nitrogen addition (0, 30, 60, and 90 kg N·hm^-2·a^-1) to soil microbial biomass, enzyme activities, and nutrient contents of the Pinus massoniana-Quercus variabilis mixed plantations in the Three Gorges Reservoir Area, with the aim to provide a theoretical basis for predicting soil carbon dynamics under the background of continuously increasing atmospheric nitrogen deposition in this area. The results showed that nitrogen addition at all levels led to a significant increase of the contents of organic carbon, total nitrogen, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) in the forest soil, while a decrease of soil pH-value, and no significant effect on the total phosphorus content. Nitrogen addition increased the activities of β-1-4 glucosidase (BG), cellobiose hydrolase (CB), acid phosphatase (AP), N-acetylglucosaminosidase (NAG) and peroxidase (POD), while inhibited that of polyphenol oxidase (PPO). There was a significant seasonal variation in soil oxidase activities, in which the peroxidase activity was higher in May and August, and the polyphenol oxidase activity was the highest in August. Soil enzyme activities were significantly correlated with soil moisture and the contents of soil nutrients, MBC, MBN, and MBP. The variation of soil enzyme activities was caused by the comprehensive effects of multiple factors. The redundancy analysis (RDA) showed that the contents of total soil nitrogen and MBC were the main environmental factors driving soil enzyme activities. The continuous increase of atmosphere nitrogen deposition would lead to soil acidification and promote the turnover of soil organic carbon and nutrient cycling in the Pinus massoniana-Quercus variabilis mixed plantations of the study area.

Ecosystem carbon uptake was co-limited by nitrogen and phosphorus in alpine meadow on the Qinghai-Tibet Plateau

LI Wen-yu, ZHANG Yang-jian, SHEN Ruo-nan, ZHU Jun-tao, CONG Nan

2022, 33(1):  51-58.  doi:10.13287/j.1001-9332.202201.004

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Alpine grassland is threatened by the import of chemicals, fertilizers and other external resources with increasing human activities on the Qinghai-Tibet Plateau. It is unclear how carbon cycle of alpine grasslands is affected by the inputs of external resources such as nitrogen, phosphorus, and potassium (N, P, K) and their interactions. We conducted a 3 year experiment on the interactive addition of N, P and K with alpine grassland as the research object to clarify ecosystem carbon exchange process in response to resource addition by measuring community coverage and ecosystem carbon exchange. The results showed the alpine meadow was represented by carbon sequestration during the growing season. The mean value of net ecosystem CO₂ exchange (NEE) was -13.0 μmol·m^-2·s^-1 under the control treatment. NEE, ecosystem respiration (ER), and gross ecosystem productivity (GEP) showed no significant responses when N, P and K were added separately. NEE was significantly increased by 95.3% and 63.9%, GEP was significantly increased by 45.5% and 33.0% under the combined addition of NP and NPK, but ER remained stable. The combined addition of NP or NPK mainly increased NEE and GEP by increasing the coverage of plant communities and affecting ecosystem water use efficiency. Plant community coverage was increased by 18.1% and 21.4%, respectively. The addition of NP increased productivity and autotrophic respiration in alpine meadow. It might cause soil acidification to inhibit heterotrophic respiration, thereby did not change ER due to the two aspects canceling each other out. The addition of N, P, K alone and NK and PK did not change ecosystem carbon exchange, while the combined addition of NP increased NEE and GEP on the nutrient-deficient alpine meadows, indicating that ecosystem carbon uptake was co-limited by N and P in alpine meadow.

Effects of water content on gross nitrogen transformation rates in forest land and grassland soils

LI Ping, WEI Wei, LANG Man

2022, 33(1):  59-66.  doi:10.13287/j.1001-9332.202201.022

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Soil water content is an important factor driving microbial activities related to soil nitrogen (N) transformation. In this study, ¹⁵N pair tracing technique combined with the numerical model FLUAZ was used to investigate the gross N mineralization, immobilization, nitrification, and denitrification rates in grassland and forest land soils from Beian City, Heilongjiang Province, China under laboratory condition [60% or 100% water holding capacity (WHC)]. The responses of soil gross N transformation rates to soil water content changes, and the mechanisms of N production, consumption, and conservation in soil under different water conditions and its environmental effects were elucidated. The results showed that changes of soil water content did not affect gross rates of N mineralization and NH₄⁺ immobilization in the forest land and grassland soils. Increasing soil water content from 60% WHC to 100% WHC significantly increased soil gross nitrification rate in forest land soil, but not affect that in grassland soil. Gross denitrification rates in grassland and forest land soils were close to zero under 60% WHC, and significantly increased under 100% WHC. The rate in grassland soil was significantly lower than that in forest land soil. In forest land soil, the ratio of gross nitrification to NH₄⁺ immobilization rates (gn/ia) and N₂O emissions under 100% WHC were significantly higher than that under 60% WHC. N₂O emission from grassland soil under 100% WHC was significantly higher than that under 60% WHC, but without significant difference in gn/ia between the two water conditions. Our results indicated that increasing soil water content in the short-term may increase the negative environmental effects of nitrogen cycling in grassland and forest land soils, especially in forest land soil.

Effects of grazing on soil organic carbon stocks in the revegetated grasslands on the Loess Plateau, China

MA Xin-xin, ZHAO Yun-ge, MA Ning, LI Wen, SUN Hui, XU Ming-xiang

2022, 33(1):  67-75.  doi:10.13287/j.1001-9332.202201.007

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Grazing is an important driving factor for soil carbon sequestration in grasslands. The objective of this study was to clarify the effects of grazing and its intensity on soil organic carbon stocks (SOCS) in the revegetated grasslands in the Loess Plateau region. With the grasslands excluded from grazing ＞20 years as the control, we investigated the SOCS in the 0-20 cm soil layer in three grazing intensities in the west, middle, and east of wind-water erosion crisscross region and the water erosion region. The intensity of grazing in the study was represented by the number of goat dung in the sampling sites, which included 0-10, 10-20, and more than 20 goat dung·m^-2, respectively. Results showed that grazing significantly affected SOCS in the 0-20 cm soil layer in the west of crisscross region, 0-10 cm soil layer in the east of crisscross region, and 0-5 cm soil layer in the water erosion region. There was no significant effect in each soil layer in the middle of crisscross region. Only in the west of crisscross region, the SOCS in the grazing intensity of 0-10 and ＞20 goat dung·m^-2 significantly decreased by 34.8%-50.9%, whereas the SOCS in each grazing intensity was not different from that in the enclosure in the other three regions. The SOCS was mainly affected by grazing intensity in the east of crisscross region and by soil physical and chemical properties and (or) litter biomass in the other three regions. In conclusion, grazing intensity of 10-20 goat dung·m^-2 did not affect SOCS in the 0-20 cm soil layer in the revegetated grassland on the Loess Plateau, China.

Pyrolysis and gas emissions characteristics of six tree species in Heilongjiang Province, China

CHEN Bo-xuan, GUO Yan, FAN Jia-le, LI Bao-zhong, TAN Chuan-qiao, LI Dong-hui, HU Hai-qing, HU Tong-xin

2022, 33(1):  76-84.  doi:10.13287/j.1001-9332.202201.012

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Forest fuels are the basis of fire occurrences, while ground dead fuels are an important part of forest fuels. Undestanding the pyrolysis characteristics and gas emissions of forest fuels is of great significance to explore the effects of forest fire on atmospheric environment and carbon balance, as well as to prevent and combat forest fire. In this study, the thermogravimetric analysis and gas emission analysis were conducted on leaf litter of six tree species (Pinus sylvestris var. mongolica, Picea koraiensis, Fraxinus mandshurica, Juglans mandshurica, Quercus mongolica, Betula platyphylla) in Heilongjiang Province to explore the pyrolysis process and combustibility of forest fuels, to analyze their pyrolysis characteristics, pyrolysis kinetics characteristics, gas emission characteristics. A four-dimensional evaluation of their combustibility was conducted based on pyrolysis parameters. The results showed that the pyrolysis temperature of holocellulose in the leaves of those six tree species ranged in 143.31-180.48 ℃ at the beginning and 345.04-394.38 ℃ at the end, lignin pyrolysis temperature ranged in 345.04-394.38 ℃ at the beginning and 582.85-609.31 ℃ at the end. The pyrolysis of the six kinds of arbor blades during the pyrolysis process affected fuel ash content, quality and temperature of the total pyrolysis. The activation energies of two main pyrolysis stages of leaves of six tree species were 18.88-27.08 kJ·mol^-1 and 13.25-27.54 kJ·mol^-1, respectively, and the pre-exponential factors were 3.13-26.28 min^-1 and 1.30-22.55 min^-1. The holocellulose activation energy and pre-exponential factor of the pyrolysis stage for P. koraiensis, F. mandshurica, Q. mongolica, and B. platyphylla were greater than that of the lignin pyrolysis stage, while the opposite was true for P. sylvestris var. mongolica and J. mandshurica. The release amounts of CO and CO₂ at the pyrolysis stage of the holocellulose was 535.16-880.11 mg·m^-3 and 7004.97-10302.05 mg·m^-3, and that at the pyrolysis stage of lignin was 240.31-1104.67 mg·m^-3 and 20425.60-33946.68 mg·m^-3, respectively. The release of CO and CO₂ at the pyrolysis stage of healdellulose was less, but mass loss was greater than that at the pyrolysis stage of lignin. In the four-dimensional combustibility ranking of the six tree species leaves, B. platyphylla was the best ignitable, P. koraiensis was the most combustible, and P. sylvestris var. mongolica was the most sustainable and consumable. The ignitability was significantly positively correlated with pyrolysis kinetics parameters of the holocellulose, while the sustainability was negatively correlated with that of lignin.

Effects of heterogeneous habitats on the coexistence of aquatic ecotype Alternanthera philoxeroides and Paspalum paspaloides

WU Hao, ZHANG San-yu, JI Qiu-bo, WANG Wen-hao, XIAO Nan-nan, ZHANG Le-hui

2022, 33(1):  85-96.  doi:10.13287/j.1001-9332.202201.002

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Species coexistence depends on the comprehensive effects of biological properties and habitat heterogeneity. Based on a large-scale field survey (21°—35° N), we compared the differences on morphological and stoichiometric characteristics between the invasive aquatic species Alternanthera philoxeroides and the native co-occurring species Paspalum paspaloides, and examined the effects of environmental factors on such differences. The results showed that the coverage and importance value (IV) of A. philoxeroides were all significantly greater than P. paspa-loides (34.3% and 104.0%, respectively), whereas the height of P. paspaloides was significantly greater than A. philoxeroides (13.8%). Moreover, the total nitrogen concentration (TN) and N:P of A. philoxeroides were significantly greater than those of P. paspaloides (55.1% and 55.8%, respectively), whereas the total carbon concentration (TC) and C:N of P. paspaloides were significantly greater than those of A. philoxeroides (4.1% and 83.8%, respectively). A. philoxeroides coverage increased with the increases of longitude, and its abundance increased with the increases of water nitrate concentration and longitude, while its IV increased with the increases of water ammonium concentration. However, the coverage, abundance, and IV of P. paspaloides decreased with the increases of ammonium concentration. C:N of A. philoxeroides decreased with the increase of ammonium concentration. Increased mean annual temperature and mean annual precipitation increased C:N but decreased N:P of P. paspa-loides. The C:P of both species decreased with the increases of ammonium concentration and electrical conductivity. N:P of A. philoxeroides was little affected by environment. These results indicated that A. philoxeroides had greater coverage and N absorption capacity than P. paspaloides, and that enriched water nitrogen would aggravate the invasion of A. philoxeroides. Meanwhile, P. paspaloides improved its C-assimilate reserves and chose the growth competition strategy for resisting A. philoxeroides invasion under the superior hydrothermal conditions. Different responses to environmental changes contributed to their coexistence in aquatic ecosystem.

Mineral nitrogen accumulation and its spatial distribution in soils in dense planting dwarf rootstock apple orchard on the Weibei dry plateau, Northwest China

CHEN Dong-kai, LUO Han, LYU Jiao-rong, ZHANG Bing-xue, LIU Dun, XIE Yong-sheng

2022, 33(1):  97-103.  doi:10.13287/j.1001-9332.202201.030

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With the rapid development of dense apple tree plantings with the dwarf rootstock cultivation method, determining accumulation and distribution characteristics of soil mineral nitrogen in densely planted orchards with dwarf rootstock is important to enable scientific fertilization of apple orchards. We investigated densely planted apple orchards with dwarf rootstocks and different plant ages (6 a, 9 a, and 12 a). We collected soil samples under trees, between trees, between rows, and at the midpoints between the trees and rows, and examined the accumulation and distribution characteristics of nitrate, ammonium, and mineral nitrogen. The cumulative amount of nitrate in the 0-300 cm soil layer increased with plant age. The difference between orchards with different plant ages was significant and showed the trend 6 a<9 a<12 a. The cumulative amount of nitrate increased from 1729 kg·hm^-2 to 3771 kg·hm^-2 with increasing plant age. The ammonium content was low for orchards of all plant ages and had little effect on the accumulation and spatial distribution of mineral nitrogen. There were two accumulation peaks of nitrate nitrogen in the vertical direction. The depth of soil layer where the second accumulation peak was located decreased from 180 cm to 220 cm with increasing plant age. In the horizontal direction, soil nitrate nitrogen content between rows increased from 27 mg·kg^-1 to 138 mg·kg^-1 with increasing plant age, representing a more than 400% increase. The difference between orchards with different plant ages was significant. In summary, excessive usage of nitrogen fertilizer and serious leaching of nitrate were problematic in all orchards with different ages. Less nitrogen fertilizer should be applied, and anti-seepage measures should be used at the fertilization location to prevent the leaching of nitrate to deep layers.

Effects of exogenous methylglyoxal on chesnut seedlings under drought stress

SUN Xiao-li, JIA Chun-yan, TIAN Shou-le, XU Wen-yan, WANG Jin-ping, RAN Kun, SHEN Guang-ning

2022, 33(1):  104-110.  doi:10.13287/j.1001-9332.202201.021

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Methylglyoxal (MG) is a novel signaling molecule with multiple functions in plants. To explore the effects of MG on Chinese chestnut (Castanea mollissima) under drought stress, two-year-old ‘Huangpeng' chestnut seedlings were treated with 15% polyethylene glycol (PEG) coupled with MG or its scavenger N-acetyl-L-cys-teine (NAC). We measured the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), and glyoxalase enzymes, including glyoxalase Ⅰ (GlyⅠ) and glyoxalase Ⅱ(GlyⅡ). Contents of antioxidants such as endogenous MG, malondialdehyde (MDA), H₂O₂, and O₂^-· as well as the osmotic adjustment substances including proline (Pro), soluble sugar (SS), glycine betaine (GB) were also detected. The results showed that 0.5 mmol·L^-1 MG significantly increased the activities of antioxidant enzymes (SOD, POD, CAT, APX, GR) and glyoxalase enzymes (GlyⅠ, GlyⅡ) in leaves of chestnut seedlings under drought stress, elevated the contents of osmotic adjustment substances (Pro, SS, GB) and antioxidant substances (ASA, GSH), and reduced the contents of MG, MDA, H₂O₂, O₂^-· and dehydroascorbate (DHA). Drought stress induced damages such as membrane lipid peroxidation and osmotic stress was alleviated by MG, leading to an overall improved adaptability of chestnut to drought stress. Moreover, the addition of MG scavenger NAC could reverse the effects induced by MG, indicating that MG had positive impacts on drought resistance of chestnut plants. Our study provided a theoretical basis for further exploring the mechanism of MG in alleviating drought stress induced symptoms in chestnut.

Effects of chitosan on chloroplast protein of vegetable soybean under NaCl stress

WANG Cong, GUO Yuan, ZHANG Wei-wei

2022, 33(1):  111-118.  doi:10.13287/j.1001-9332.202201.029

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Chitosan (CTS) can effectively enhance the tolerance of plants to salt stress, but its role in driving the responses of vegetable soybean seedlings to salt stress at proteomic level is still unclear. Here, both 200 mmol·L^-1 CTS and distilled water were used to spray the leaves of vegetable soybean ‘Lvlingtezao' seedlings. After 5 days of induction, NaCl stress and nutrient solution without NaCl were treated. Chloroplast proteins were extracted from leaves on the third day of NaCl treatment and analyzed by using the isobaric tags for relative and absolute quantification (iTRAQ). The result showed that CTS significantly increased net photosynthetic rate (P_n) of vegetable soybean seedlings under NaCl stress. Totally 549 reliable quantitative information proteins were identified, of which 442 existed in at least two biological repeats, including 26 up-regulated proteins and 4 down-regulated proteins associated with the effects of CTS on vegetable soybean response to NaCl stress. In addition, enrichment analysis of molecular function and metabolic pathway showed that up-regulated proteins were mainly related to molecular functions, including electron transport, chlorophyll binding, electron carrier activity, and were enriched in the pathways of photoreaction, carbon reaction and glyoxylic acid and dicarboxylic acid metabolism. Down-regulated proteins were mainly related to poly (U) RNA binding. Our results suggested that CTS could affect photosynthesis of vegetable soybean seedlings under NaCl stress through multiple pathways.

Accumulation of Cry proteins in soil released from Bt rice after planting for multiple years

WANG Yong-mo, DENG Jia-xin, ZHANG Jin-xin, JIA Rui-zong

2022, 33(1):  119-125.  doi:10.13287/j.1001-9332.202201.028

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Cry protein residue and accumulation in soil are two important components of the environmental safety assessment for the plantation of transgenic Bt crops. Several Bt rice lines with good commercial prospects have been developed in China, but it is unclear whether Cry proteins will accumulate in soils after multiple years of Bt rice cultivation. We planted the transgenic Bt rice lines cry1Ab/1Ac Minghui 63 (Huahui No. 1) and cry2A Minghui 63 for 9 years in the same field. The Cry proteins in the rhizosphere soil were estimated with enzyme linked immunosorbent assay (ELISA) at tillering stage and on the 60th day after harvest in each year. The Cry protein residues during the seedling, flowering and ripening stages were estimated in the first year (2012) and the last year (2020) of the experiment. In 2012, the concentration of Cry1Ab/1Ac in the rhizosphere soil of Huahui No. 1 was 1.25, 1.77, 1.97, 1.71 and 0.30 ng·g^-1 at the seedling, tillering, flowering, ripening stages and on the 60th day after harvest, respectively. In 2020, the corresponding values were 1.30, 1.69, 2.03, 1.77, and 0.43 ng·g^-1. In 2012, the concentration of Cry2A in rhizosphere soil of line cry2A Minghui 63 was 0.91, 1.52, 1.53, 1.37, and 0.12 ng·g^-1 at the seedling, tillering, flowering, ripening stages and on the 60th day after harvest, respectively. The corresponding values in 2020 were 0.95, 1.43, 1.61, 1.40, and 0.15 ng·g^-1. Results of multi-way ANOVA showed that the effect of year was not significant, but the effects of rice variety and growth stage were significant. Our results indicated that Cry proteins could be detected in rhizosphere soil during the growth stages of Bt rice, but would be degraded by 60 d after harvest, and that the concentrations of Cry proteins in the soil would not accumulate across multiple planting years.

Characteristics of acidification and the distribution of available phosphorus along soil depths in heavy clay soils in southern Henan Province, China

CHEN Wen-ju, LI Pei-pei, WEN Qian, HUANG Ke-ming, WANG Meng-yu, XU Heng, HUA Dang-ling, HAN Yan-lai

2022, 33(1):  126-132.  doi:10.13287/j.1001-9332.202201.025

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The acidification of agricultural soil in the southern part of the North China Plain has become more obvious, which is particularly true for the heavy clay soil types, such as yellow-cinnamon and lime concretion black soils. To understand the spatial variability of the pH value and nutrients on the vertical agricultural soil profile of heavy clay soils in this area, we measured pH values and available phosphorus (AP) in 63 farmland sample points from Xiping County in the southern Henan Province. Geostatistical methods and ArcGIS technology were used to map soil pH values along three soil depths (0-10, 10-20, and 20-30 cm) and the spatial distribution of soil AP in the tillage layer (0-20 cm). Furthermore, the correlation between pH and AP was analyzed. The results showed that mean pH values of typical yellow-cinnamon and typical fluvo-aquic soils from three soil layers were 4.98, 4.93, 5.31, and 5.46, 5.81, 6.26, respectively, which gradually increased with soil depths. However, there was no significant difference among the three soil layers. Mean pH values of typical lime concretion black soil from the three soil layers were 5.23, 5.43 and 6.03, respectively, and that of the 20-30 cm soil layer was significantly higher than that of the 0-10 cm (by 0.8-1 pH unit) and the 10-20 cm layers. The pH of the 20-30 cm soil layer of the calcareous lime concretion black and moist soils were also significantly higher than that of the 0-10 and 10-20 cm soil layers. The AP contents of the typical yellow-cinnamon, typical lime concretion black, moist, typical fluvo-aquic and calcareous lime concretion black soils in 0-20 cm soil layer were 8.85-54.75, 4.27-37.49, 8.22-51.80, 6.07-34.82, and 13.22-22.85 mg·kg^-1, respectively. The results of the map indicated that the areas with low AP were distributed in the middle of the study area in blocks, and the areas with high AP were distributed around the study area in dots and flakes. The pH values of the typical yellow-cinnamon, typical lime concretion black, and moist soils positively correlated with the content of AP in the 0-20 cm soil layer. In conclusion, the heavy clay soil in southern Henan Province became stratified acidification, which slowed down along the soil depth. Soil AP contents in the tillage layer were distributed unevenly in the study area, and were affected by soil types and soil pH. These results would be useful for the improvement of heavy clay soil acidification in the southern part of the North China Plain.

Characteristics of soil anti-scouribility in gully head wall of grass-covering on the gullied Loess Plateau, Northwest China

SHA Xiao-yan, LI Kui, WANG Wen-long, LOU Yi-bao, KANG Hong-liang, FENG Lan-qian, NIE Hui-ying

2022, 33(1):  133-140.  doi:10.13287/j.1001-9332.202201.027

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Vegetation restoration in the Chinese Loess Plateau has significantly changed soil erosion process of gully head wall. In order to investigate the characteristics and controlling factors of soil anti-scour properties of gully head covered by grasses, we carried out indoor undamaged soil trench scouring tests. By using barren gully head as the control, the physical and chemical properties and anti-scouring characteristics of soil in different soil layers (0-10, 10-20, 20-40, 40-60, 60-80, 80-100 cm) of the vertical wall of gully with grass cover were analyzed. The results showed that water-stable aggregate content and cohesion in barren and grass-covering gully head decreased with soil depth. Soil organic matter content and soil anti-scouribility coefficient in barren gully head decreased with soil depth, while the two indicators for gully head covered by grass increased firstly and then decreased with soil depth, with the maximum value (24.30 g·kg^-1 and 58.86 L·g^-1) in 10-20 cm soil layer. Meanwhile, the soil anti-scouring coefficient in each soil layer of grass-covering gully head was 1.7-9.3 times of that in soil layer of barren gully head. Soil organic matter content, water-stable aggregate content, cohesion and root length density all presented significantly positive correlation with soil anti-scouribility, among which soil organic matter content had the highest coefficient (r=0.98). Results of this study might provide basic data for the study of headcut erosion mechanism in Loess Plateau gully region, and scientific basis for effective control of soil and water loss in this region.

Effects of straw returning to movement characteristics of soil preferential flow in sugarcane fields

WU Han, CHEN Xiao-bing, JIANG Bo, QIN Zi-cheng, LIU Si-jia, LIU Jun-jie

2022, 33(1):  141-148.  doi:10.13287/j.1001-9332.202201.014

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The measures of returning straw to the field can change soil environment in the field and affect crop growth. In order to explore the impacts of different straw returning measures on the preferential flow in the field, we investigated the movement characteristics of preferential flow in sugarcane fields under different straw returning measures [straw mulching (CM), straw burning mulching (BM), and non-straw mulching (CK)] in Guangxi by combining image analysis techniques with ecological landscape pattern analysis methods. The results showed that under the same external water supply environment, soil staining morphology of non-straw mulching sugarcane fields differentiated into finger-like and clump-like. Both straw mulching and straw burning mulching were mainly differentiated into clump-like. The mean total staining area ratio was significantly higher than that of non-straw mulching (26.0%). The ratio of surface staining area decreased rapidly under non-straw mulching. The water movement range decreased rapidly under straw mulching and straw burning mulching in the depth of 15-30 cm. The change rate of straw mulching staining area ratio was the lowest in the deep soil. The shape index of non-straw mulching was 15.54. The water flow movement was more concentrated. The average sub-circular index of straw mulching and straw burning mulching was 0.67 in the sugarcane field, with a higher degree of preferential flow bending, an average proximity index of 0.87, and better water flow connectivity. The average substrate flow depth (3.52 cm) and edge density index (11.51) were the smallest under non-straw mulching, but the priority flow ratio was the largest (73.2%), and the spatial development degree of preferential flow was the highest. The straw returning measures reduced the preferential flow in the sugarcane fields, with positive effects on water conservation.

Territorially ecological restoration zoning and optimization strategy in Guyuan City of Ningxia, China: Based on the balance of ecosystem service supply and demand

YUE Wen-ze, HOU Li, XIA Hao-xuan, WEI Jing-xian, LU You-peng

2022, 33(1):  149-158.  doi:10.13287/j.1001-9332.202112.024

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Scientifically identifying the territorially ecological restoration zoning is a vital prerequisite for implementing ecological restoration projects and enhancing environmental quality. Based on remote sensing data, we syste-matically assessed supply and demand for ecosystem service and their relationship in Guyuan City, China by using the InVEST model, coordination degree model, and spatial autocorrelation analysis. We carried out territorially ecological restoration zoning by coupling the ecosystem service supply and demand. Furthermore, the corresponding optimization strategies were put forward according to the regional characteristics of natural resources and socio-economic development. The results showed that the areas with high water yield, carbon storage, soil conservation and habitat quality were mainly located in the southern part of Guyuan City. The areas with high population density, economic development level and high ecological demand were mainly located in the central urban area and the location towns of the county government. The spatial mismatch of supply and demand for ecosystem services in Guyuan City was dominant, as indicated by the fact that the areas with high ecological supply having low ecological demand and low ecological supply having high ecological demand. The average coordination index was 0.5, indicating that the relationship between ecological supply and ecological demand was basically coordinated. Based on the diffe-rences between supply and demand of ecosystem services and regional natural geographical pattern, the administrative township units in Guyuan could be classified into six ecological restoration zonings: key ecological restoration area, potential ecological restoration area, ecological economic reconstruction area, characteristic agricultural development area, ecological core protection area, and ecological industry construction area. Different management strategies were proposed to provide scientific support for ecological restoration.

Ecological compensation strategy of the old revolutionary base areas along the route of Long March based on ecosystem service value evaluation

DENG Yuan-jie, HOU Meng-yang, JIA Lei, WANG Ya-qin, ZHANG Xiao, YAO Shun-bo

2022, 33(1):  159-168.  doi:10.13287/j.1001-9332.202201.019

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The conflict between ecological protection and socio-economic development in the old revolutionary base areas along the route of Long March can be addressed by ecological compensation. In this study, we collected 2018 data of land use, net primary productivity of vegetation, climate factors and so on. The ecosystem service value of 310 counties in the old revolutionary base areas was calculated using the data and modified equivalent factor. Then, the regional differentiated ecological compensation estimation method was applied to estimate the priority and amount of ecological compensation within the area. We further proposed the ecological compensation strategy adopted for the old revolutionary base areas along the route of Long March. The results showed that the total value of ecosystem services in the old revolutionary base areas along the route of Long March amounted to 2593.74 billion yuan in 2018. Forest services took the highest proportion (58.8%), followed by grassland and waters. The total amount of ecological compensation made for the old revolutionary base areas along the route of Long March reached 183.405 billion yuan. Compared with this amount, there was a large gap in the actual compensation funds available to the region. In addition, the total amount of ecological compensation accounted for only 0.04% of the aggregate GDP in this area, which put some strain on local fiscal resources and showed certain viability in ecological compensation. In 2018, totally 100 old revolutionary base areas along the route of Long March were designated as the priority areas for ecological compensation, consistent with the national key eco-function zone policy. However, there were deviations in the allocation of ecological compensation funds, with some priority areas receiving no compensation. As for the compensation strategy, it is necessary to put in place a diversified, market-oriented and comprehensive ecological compensation mechanism to increase the sources of ecological compensation funds at first. Then, efforts should be continued to optimize the spatial selection of ecological compensation in the old revolutionary base areas along the route of Long March and to improve the efficiency of regional ecological compensation mechanism.

Spatial-temporal evolution and drivers of ecosystem service value in the Dongting Lake Eco-economic Zone, China

CHEN Rui, YANG Can, YANG Yan, DONG Xiang-ze

2022, 33(1):  169-179.  doi:10.13287/j.1001-9332.202201.015

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With the rapid urbanization, research on the spatial-temporal evaluation and drivers deduction of ESV is important for regional social-economic-ecological coordinated and sustainable development. Based on remote sensing data of Dongting Lake Eco-economic Zone in four years (2005, 2010, 2015, and 2018), we investigated the spatial-temporal pattern deduction characteristics of ecosystem service value (ESV) from a grid scale of 3 km × 3 km with the technological support of ArcGIS and GeoDa, as well as combining the equivalent factor, spatial auto-correlation and hot-spot analysis method. We further explored the dominant drivers of spatial heterogeneity of ESV and the interaction mechanisms among different drivers using geo-detector. The results showed that, during the study period, the construction land area had the most significant growth by 49.2%. Nevertheless, grassland and water area had a relatively large decrease, while the other land area did not change. The ESV decreased gradually in general during the study period. The ESV of unused land increased rapidly, while that of the other lands all showed decrease to different extents. The overall spatial layout of ESV in the study area was “high in the middle and low in the surroundings”. The spatial cluster effect of ESV was significant, but the cluster effect of high and low values of ESV tended to weaken during the study period, showing a trend of gradually decreasing. The spatial heterogeneity of ESV was affected by the coupling and coordination of natural environmental factors and socio-economic factors in the study area, with largest contribution from the human active index.

Spatial effects and influencing factors of natural capital utilization in the Yangtze River Economic Belt, China

LI Zhu, WANG Zhao-feng, WU Wei

2022, 33(1):  180-190.  doi:10.13287/j.1001-9332.202201.020

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Clarifying the regional natural capital utilization and its spatial effects and influencing factors has important theoretical and practical significance for regional sustainable development. Here, we used a three-dimensional ecological footprint model, exploratory spatial data analysis, a spatial Markov chain, and a spatial panel Durbin model to explore the spatial effects and influencing factors of overall and subcategory natural capital flow and stock occupancy of 112 prefecture-level cities in the Yangtze River Economic Belt from 2008 to 2018. The results showed that the total, per capita, and subcategory natural capital flow and stock occupancy increased during the study period. Most of the regions with low overall and subcategory natural flow occupancy were located in the East, whereas most of the regions with high overall and subcategory natural flow occupancy were mostly located in the Central and Wes-tern area. However, their stock occupancy behaved differently. Except for farmland stock, the overall and subcategory natural capital flow and stock occupancy showed spatial agglomeration. The traditional and spatial Markov chain presented a “Matthew effect” and a “spatial spillover effect” in natural capital flow and stock occupancy. Economic growth and industrial structure positively affected natural capital flow and stock occupancy. Population growth positively affected natural capital flow occupancy. Urbanization rate negatively affected natural capital flow occupancy, and positively impacted natural capital stock occupancy. Government intervention negatively affected the farmland flow and fossil fuels land stock occupancy. Environmental governance negatively affected the natural capital flow occupancy, but positively affected the natural capital stock occupancy. Environmental pollution positively affected natural capital flow and stock occupancy.

Responses of aquatic vegetation coverage to interannual variations of water level in different hydrologically connected sub-lakes of Poyang Lake, China

WANG Huan, CHEN Wen-bo, HE Lei, LI Hai-feng

2022, 33(1):  191-200.  doi:10.13287/j.1001-9332.202201.013

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The variation of water level is the main environmental factor controlling the growth of aquatic vegetation. It is of significance to understand its influences on aquatic vegetation coverage in sub-lakes under different hydrolo-gical control modes. Taking the free connected sub-lake Bang Lake and locally controlled sub-lake Dahuchi Lake of Poyang Lake as a case and based on remote sensing cloud computing platform of the Google Earth Engine (GEE), we used the pixel binary model to estimate aquatic vegetation coverage from 2000 to 2019, and analyzed the temporal and spatial differentiation characteristics, and the variation trend was simulated by combining the method of Sen+M-K. We analyzed the water level change characteristics during the study period and the relationship between the hydrological parameters and the aquatic vegetation coverage area of sub-lakes with different hydrological connectivity was explored by setting up the water level fluctuation parameters. The results showed that the aquatic vegetation coverage of Bang Lake was more susceptible to water level changes, while Dahuchi Lake was more stable. The aquatic vegetation was patchily and sporadically distributed in the years with low vegetation coverage. In the years with high vegetation coverage, it was distributed in a ring-like pattern, spreading from the center of the lake to the shore. The aquatic vegetation coverage of Bang Lake was more likely influenced by water level fluctuation rate, while the aquatic vegetation coverage of Dahuchi Lake was more likely influenced by the flooding duration of 17 m characteristic water level. The flooding duration of 19 m characteristic water level had a strong negative correlation with the aquatic vegetation coverage of Bang Lake and Dahuchi Lake. The trend of aquatic vegetation in Bang Lake was dominated by stabilization and slight improvement, while that in Dahuchi Lake was dominated by stabilization and significant degradation. Our results could help to further understand the dynamics of water hydrological ecosystem with different hydrological connectivity and provide a reference for lake management and conservation.

Spatio-temporal variation of reference crop evapotranspiration and its climatic mechanism in Nenjiang River Basin, China

ZHU Guang-lei, TONG Shou-zheng, ZHAO Chun-zi

2022, 33(1):  201-209.  doi:10.13287/j.1001-9332.202201.017

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To understand the temporal and spatial variations of reference crop evapotranspiration (ET₀) in Nenjiang River Basin, and clarify the effects of climatic factors on ET₀, we calculated the daily ET₀ of each station in Nenjiang River Basin from 1970 to 2019 by Penman-Monteith formula, analyzed the temporal variation trend and spatial distribution pattern of ET₀. We further quantitatively examined the sensitivity of ET₀ to meteorological factors by sensitivity analysis, and explored the contribution of meteorological factors to ET₀ changes. The results showed that ET₀ generally showed an insignificant decreasing trend during the study period in the Nenjiang River Basin. ET₀ decreased in spring, summer, and autumn, but increased in winter, and decreased from southeast to northwest. ET₀ had the highest sensitivity to relative humidity at both temporal and spatial scales. The sensitivity coefficients of mean temperature, relative humidity and wind speed increased gradually, while that of sunshine hours decreased gradually. ET₀ was sensitive to mean temperature in northern Greater Khingan Mountains and Lesser Khingan Mountains, while to wind speed in southern Greater Khingan Mountains and Songnen Plain. Wind speed was the main factor affecting the change of ET₀ in the whole year, spring, autumn, and winter. Sunshine hours was the main affecting factor in summer. The mean temperature and relative humidity had the greatest contribution to ET₀ in the north of Greater Khingan Mountains and Lesser Khingan Mountains, and it was the wind speed in Songnen Plain.

Effects of simulated rainfall enhancement on sediment CO₂ flux in dry lakebed of Barkol Lake, China

ZHANG Yu-xin, JIANG Jing-bai-lun, LI Dian-peng, YAO Mei-si, SUN Tao, ZHOU Jian-qin, JIA Hong-tao

2022, 33(1):  210-218.  doi:10.13287/j.1001-9332.202201.018

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Understanding the responses of lake sediment carbon process to climate change is an important part of a comprehensive understanding of lake carbon budget. To explore the effects of future rainfall increase on sediment carbon flux, undisturbed sediment samples were collected from the bottom of dry lake Barikun in Hami, Xinjiang for the incubation experiment. Based on the increase rate of precipitation (4 mm·10 a^-1) and the distribution characteristics of rainfall in the plant growing season in Hami, Xinjiang since 1960, five rainfall treatments were set (86 mm, T₀; 94 mm, T₁; 102 mm, T₂; 110 mm, T₃; 126 mm, T₄) based on the rainfall in growing season of 2016 (86 mm). We analyzed the effects of rainfall increase on sediment CO₂ flux. Results showed that compared with that before rainfall, the sediment CO₂ flux increased after 1 day of rainfall in the study area. Compared with that during May to July, the CO₂ flux of sediments in August to October decreased. There was no variation of CO₂ accumulative emission among the T₀-T₃ treatments from May to October. However, the average CO₂ emission rate under the T₃ treatment (0.22 μmol·m^-2·s^-1) was significantly higher than that under the T₄ treatment (0.14 μmol·m^-2·s^-1). All treatments showed CO₂ sink at the first day of rainfall (1 d), with T₄ treatment (-0.13 μmol·m^-2·s^-1) having the highest “carbon sink” capacity. After 1 day, the CO₂ sink converted to CO₂ source under the five rainfall treatments, with the CO₂ emission rate under T₃ treatment (0.34 μmol·m^-2·s^-1) being significantly higher than those under other treatments. Compared with May, the CO₂ emission fluxes of T₂-T₄ treatments were significantly higher than those at the time from August to October. Under the condition with relatively stable temperature, the CO₂ flux of sediments was significantly correlated with the sediment moisture and air humidity. In the next 60 years, the continuous increase of future rainfall may be an important factor promoting CO₂ emission from lake sediment in arid regions, and thus affecting global warming.

Characteristics of soil microbial communities in different restoration models in the ecological immigrants' emigration area in southern Ningxia, China

YANG Hu, MA Qiao-rong, YANG Jun-long, ZHOU Liang, CAO Bing, ZHANG Wei-jiang

2022, 33(1):  219-228.  doi:10.13287/j.1001-9332.202201.036

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To reveal the effects of plantations on soil microbial environment,the composition and diversity of soil fungi and bacterial communities in five restoration models (Robinia pseudoacacia, Populus hopeiensis, Pinus tabuliformis, Picea crassifolia, natural restoration) in the mountainous area of southern Ningxia were compared by using high-throughput sequencing technology. The correlation between soil physical-chemical properties and dominant microbial groups was analyzed. The results showed that: 1) Dominant fungi in different restoration models were Ascomycota, Basidiomycota, Mortierellomycota, and unclassified fungi, which accounted for 90% of total fungal community. The dominant soil bacteria were Actinobacteria, Proteobacteria, Acidobacteriota, Chloroflexi, and other bacteria, accounting for more than 80% of total bacterial community. 2) The diversity of soil fungi in P. tabuliformis forest was the highest, with Shannon index, and Simpson index being 3.72±0.37 and 0.07±0.04, respectively. The richness of fungi in naturally restored forest land was the highest, with Ace and Chao1 index of 708.19±137.25 and 706.26±125.34, respectively. The bacterial diversity and richness of species in P. tabuliformis forest land was the highest. The Shannon, Simpson, Ace and Chao1 indices were 6.57±0.04, 0.004±0.00, 3439.81±41.67, 3463.14±32.16, respectively. 3) The fungus with significant difference among restoration models were Solicoccozyma, Cladosporium, and Alternaria. Bacteria from Norank_f_67-14, Rubrobacter_f_Rubrobacteraceae, Sphingomonas_f_Sphingomonadaceae had significant difference among restoration models. 4) The RDA ordination of the dominant microbial flora and soil physical-chemical properties showed that soil bulk density (BD), carbon to nitrogen ratio (C/N), and pH were the major factors affecting the dominant fungal flora. BD, nitrogen to phosphorus ratio (N/P), total phosphorus (TP), and total carbon (TC) were the main factors affecting the dominant bacterial flora. In general, the difference of composition and diversity in the fungal community of different restoration models was higher than that of the bacterial community, indicating that the fungal communities were more sensitive to the changes of tree species and soil environment than bacterial communities. Our results could provide the theoretical foundation for vegetation restoration measures and the maintenance of ecosystem function stability in southern Ningxia.

Growth and degradation characteristics of an efficient and broad-spectrum atrazine-degrading strain SB5

LU Chang-ming, LI Xiang, XU Ming-kai, LI Xin-yu, LI Xu, GU Wu, GUO Qiu-cui, ZHANG Hui-wen

2022, 33(1):  229-238.  doi:10.13287/j.1001-9332.202201.032

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In this study, triazine-degrading strain SB5 was isolated and screened from the activated sludge contaminated with atrazine by enrichment culture technology. Based on its morphology and 16S rRNA gene analysis, strain SB5 was initially identified as Paenarthrobacter sp. It contained the atrazine-degrading genes trzN, atzB, and atzC. The addition of glucose, sucrose, sodium citrate, yeast extract and peptone to the culture medium significantly increased the biomass and atrazine degradation efficiency of strain SB5. The addition of (NH₄)₂SO₄ and NH₄Cl inhibited the biomass of strain SB5, but did not affect its degradation efficiency for atrazine. The addition of starch did not affect the biomass of strain SB5, but significantly inhibited its degradation for atrazine. Strain SB5 showed good atrazine tolerance and atrazine degradation ability in the temperature range of 4-42 ℃, initial pH of 4-10 and initial concentration of 50-1000 mg·L^-1. Using 100 mg·L^-1 atrazine as the sole carbon source, the strain SB5 degraded 100% of atrazine within 36 h under the optimal conditions of 37 ℃ and initial pH 8.0. The results of degradation spectrum analysis showed that strain SB5 had a good degradation effect on the six triazine herbicides (simazine, terbuthylazine, propazine, cyanazine, ametryn and prometryn) at an initial concentration of 100 mg·L^-1, and the degradation rates were 86.4%, 92%, 98.6%, 95.6%, 100% and 99.2% after 48 h of incubation, respectively. The results demonstrated that SB5 was an efficient and broad-spectrum degradation strain. The strain SB5 further enriched the strain resources for atrazine biodegradation, and its high-efficient and broad-spectrum degradation characteristics for triazine herbicides showed a potential application value in the development of bioremediation technology for the pollution of triazine herbicides.

Spatial and temporal characteristics of community structure of nitrite-dependent anaerobic methane-oxidizing bacteria in paddy soil

TIAN Mao-hui, SHEN Li-dong, LIU Xin, YANG Wang-ting, JIN Jing-hao, YANG Yu-ling, LIU Jia-qi

2022, 33(1):  239-247.  doi:10.13287/j.1001-9332.202112.025

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Paddy fields are one of the most important methane sources, which have great impacts on climate change. The nitrite-dependent anaerobic methane oxidation, by NC10 phylum bacteria-Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria, is a new process regulating methane emission from paddy fields. However, little is known about the spatial and temporal variations of M. oxyfera-like bacterial communities and the regulating factors in paddy soils. We investigated the community composition, diversity, and abundance of M. oxyfera-like bacteria in 0-40 cm depth of paddy soils at key growth stages of rice, including tillering, jointing, flowering, and milky stages. Results of high-throughput sequencing showed that community composition of M. oxyfera-like bacteria differed significantly among different soil layers, while no significant variation was observed among different rice growth stages. The diversity of M. oxyfera-like bacteria increased with soil depth. Real-time quantitative PCR showed that the 16S rRNA gene abundance of M. oxyfera-like bacteria ranged from 5.73×10⁶ to 2.56×10⁷ copies·g^-1 (dry weight), with the highest gene abundance in the 10-20 cm layer. Further, the abundance of these bacteria showed a decreasing trend with rice growth. Soil organic carbon content and soil pH were correlated with the M. oxyfera-like bacterial community structures and abundance. In all, our results suggested a certain degree of heterogeneity of spatial and temporal distribution of M. oxyfera-like bacterial communities in paddy soils, which was largely influenced by soil organic carbon and soil pH.

Influencing factors for natural populations of Lycorma delicatula in different habitats

BAO Ke-xin, DANG Ying-qiao, WANG Xiao-yi, CUI Jian-zhou

2022, 33(1):  248-254.  doi:10.13287/j.1001-9332.202201.037

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To explore the differences between growth and population dynamics of natural Lycorma delicatula in the plantations and semi-natural forests, the susceptible stages and major suppression factors were determined to provide basis for the prediction and controlling the pest. The development duration and life table of L. delicatula in different habitats were established by using tracking method. The index of exclusion effect for lethal factors and the K-value in each development stage were calculated. The population trends were analyzed through the survival curve and key drivers of population change. The results showed that the development duration of L. delicatula in the plantation habitat and semi-natural habitat was significantly different, with thelatter being 25.7 d longer than the former. There were significant differences in the development duration of 1st-3rd-instars nymphs and pre-oviposition period of adults between these two habitats, but no significant difference in the 4th-instar nymphs. The total mortality rate in the plantation habitat and semi-natural habitat was 83.6% and 98.6%, respectively. The index of population trend in the plantation habitat was significantly higher than that in the semi-natural habitat. The population of L. delicatula increased sharply in the plantation habitat, but showed a decline trend in the semi-natural habitat. All of the survival curves of L. delicatula were Deevey-Ⅲ type, and the EIPCs of the “parasitic natural enemies” in egg stage were the highest in both habitats as 1.3 and 1.6, and the total K values were 0.2 and 0.3, respectively. The regression slopes of K-value of natural enemies were the highest (both 0.6). These findings revealed that the semi-natural habitat played an important role in the natural regulation of L. delicatula.

Microplastics in the stomach and intestine of pelagic squid: A case study of Dosidicus gigas in open sea of Peru

WANG Ya-xin, FAN Jiang-tao, GONG Yi, NIU Cheng-gong, CHEN Xin-jun

2022, 33(1):  255-260.  doi:10.13287/j.1001-9332.202201.038

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Microplastic (MP) ingestion by marine animals has been well documented, but less being known about pelagic squid. Jumbo squid Dosidicus gigas supports the world's largest cephalopod fishery and plays an important ecological role in the Eastern Pacific Ocean. In this study, D. gigas taken from the open sea of the Peruvian Exclusive Economic Zone were selected as research objects. We estimated the abundance and characteristics of MPs in the stomach and intestine of D. gigas and investigated the differences between tissues and sexes. Similar abundance and characteristics of MPs were observed in the same tissue of females and males. However, the stomach had a higher abundance of MPs with larger size than the intestine, while the MP abundance by stomach wet weight was lower than that of the intestine. The MPs were predominantly fiber-shaped, with blue or black color. The most frequent polymers were high-density cellophane and polyacrylic acid. These polymers could sink into deeper sea layers and were available for D. gigas living there during the daytime. Our findings revealed the distribution pattern of MPs in the waters of the Peruvian fishing ground. This study could improve our understanding of the MP contamination level in pelagic squid, and have implications for evaluating the ecological effects of MP on cephalopods.

Identification of released population of Japanese flounder based on stable isotopes analysis

WANG Qing-lin, YU Shan-shan, JIN Xiao-min, REN Jian-gong, SI Fei, SUN Gui-qing, SUN Zhao-hui, BAI Zeng-qi

2022, 33(1):  261-267.  doi:10.13287/j.1001-9332.202201.023

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Japanese flounder (Paralichthys olivaceus) is an important releasing fish in the Yellow and Bohai Seas of China. The identification of wild and releasing population is the premise to evaluate the enhancement effects. In order to study the application of stable isotope in the identification of released P. olivaceus population, captured juveniles in the offshore releasing area of Qinhuangdao were distinguished into wild and released population using previous method (combination of morphology and molecular). Then, the contents of carbon and nitrogen stable isotope in muscle and otoliths (including the whole and the core region) were measured. The cultured population was set as control. The results showed that δ¹³C values (wild population: -17.19‰±0.73‰; released population: -17.10‰±0.61‰; cultured population: -20.75‰±0.07‰) and δ¹⁵N values (wild population: 11.81‰±0.38‰; released population: 11.62‰±0.48‰; cultured population: 8.64‰±0.60‰) of muscle and δ¹³C value (wild popu-lation: -4.47‰±0.35‰; released population: -4.63‰±0.29‰; cultured population: -6.59‰±0.58‰) of the whole otolith could be used to identify the cultured population, but could not be used to distinguish the wild from the released population. The δ¹³C value (wild population: -4.66‰±0.30‰; released population: -5.41‰±0.21‰; cultured population: -5.37‰±0.19‰) of the core region of otolith could be used to identify the wild popu-lation. The δ¹⁸O values of the whole and the core region of otolith from these three groups were overlapped and could not be used to distinguish different populations. Our results indicated that the δ¹³C value of the core area of otolith could be used to identify wild and released population, with application prospect in the identification of broodstocks participating in spawning migration. This study provided basic data and technical methods for evaluating early resources replenishment and the effects of Japanese flounder enhancement.

Reviews

Problems and countermeasures of soil health quality in urban green space

HAN Ji-gang, LI Gang, ZHANG Wei-wei, LIU Wen, LIU Shu, MA Xiang, ZHANG Lang, ZHU Yong-guan

2022, 33(1):  268-276.  doi:10.13287/j.1001-9332.202201.009

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Soil quality of urban green space (UGS) is the basis for ensuring healthy growth of plants and maintaining the healthy ecosystem services for the residents and the sustainable development of city. At present, in order to improve the soil quality of UGS, more attention has been paid to fertility quality and environmental quality, but less to the health quality. We analyzed the concept, connotation, and assessment indicator of soil health quality, summarized the main problems and challenges of soil health quality of UGS. Finally, we put forward the ways and strategies to improve soil health quality of UGS, and prospected future research direction. Our aim was to attract the attention to the soil quality of UGS, especially soil health quality, and the importance of comprehensively improving soil quality of UGS, eventually providing strong technical support for urban sustainable development and eco-city construction.

Research progress on soil soluble organic nitrogen

QUAN Zhi, LIU Xuan-ang, LIU Dong

2022, 33(1):  277-288.  doi:10.13287/j.1001-9332.202201.010

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Soluble organic nitrogen (SON) and inorganic N are two crucial nitrogen (N) forms in the cycling of N within terrestrial ecosystems, acting as either a “source” or a “sink” to the environmental N release. The mineralization, retention, leaching, and plant absorption of N in terrestrial ecosystems are closely related to SON. As a result, the role of SON in soil material circulation and nutrient flow has attracted much attention and has become one of the hotspots in various research fields, such as ecology, environmental science, soil science, and hydrology. We reviewed the research progress on soil SON, including the definition and quantification, the size and composition, the absorption and utilization by plants and microorganisms, the sources and influencing factors, and the transformation, migration, and leaching loss of SON. SON is a complex collection of multi-component soluble organic matter, mainly as recalcitrant components (difficult to degrade), with relatively low proportion as labile components (easily degradable). Due to the difference in the turnover time among recalcitrant and labile components, the roles of SON in N cycling and turnover cannot be fully represented by the SON quantity. Therefore, to accurately reflect the role of SON in N turnover, N uptake, and N leaching, it is necessary to establish new methods and distinguish between recalcitrant and labile SON components in future studies. When studying the role of SON in N conversion and N absorption, it is essential to focus on its labile components. When studying the contribution of soil SON to N leaching or runoff loss, it is necessary to focus on the recalcitrant components.