Table of Content

18 March 2018, Volume 29 Issue 3

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Effects of simulated warming and functional group removal on survival and growth of Abies faxoniana seedlings.

PANG Xiao-yu, YUAN Xiu-jin, WANG Ao, LI Mai-he, LIU Xing-liang, PAN Hong-li, YU Fei-hai, LEI Jing-pin

2018, 29(3):  687-695.  doi:10.13287/j.1001-9332.201803.010

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Warming and herbaceous functional group removal experiment was conducted in subalpine meadow to examine the effects of herbaceous species on Abies faxoniana seedlings by analyzing its physiological responses. The survival rate and non-structural carbohydrate content were significantly increased, but the growth and root/shoot of A. faxoniana were decreased. Seedling survival was significantly positively correlated with non-structural carbohydrate content, especially with soluble sugar. Under the treatment without warming, herbaceous species inhibited the survival of A. faxoniana, increased height growth and aboveground biomass. Grasses and forbs decreased the root length and belowground biomass of A. faxoniana. In the warming treatment, forbs increased the survival of A. faxoniana, sedges decreased root length and belowground biomass of A. faxoniana, and grasses and forbs decreased height growth and aboveground biomass of A. faxoniana. Simulated warming increased the survival of A. faxoniana seedlings, but also made it face stronger competition from herbaceous and thus inhibited its growth.

Response of seed reproduction of two dominant lakeside species to experimental warming in a typical plateau wetland in Northwestern Yunnan Plateau, China.

WANG Zhi-bao, SUN Mei, LIU Zhen-ya, ZHANG Xiao-ning, WANG Hang, ZHANG Yun, XIAO De-rong

2018, 29(3):  696-704.  doi:10.13287/j.1001-9332.201803.008

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Based on the forecasted warming scenarios by IPCC, we studied the impacts of warming (increased by 2.0 and 3.5 ℃) on seed reproduction of two lakeside dominant species (Schoeno-plectus tabernaemontani and Sparganium stoloniferum) in a typical plateau wetland (Napahai) in Northwestern Yunnan, by using “open-top chamber” technique. The results showed that warming had significant effects on the seed setting rate of both species, though with interspecific variation. The seed setting rate of S. tabernaemontani was significantly increased under two warming treatments, while that of S. stoloniferum was significantly decreased under the 2.0 ℃ warming treatment and had no variation under the 3.5 ℃ warming treatment. Warming promoted the spike growth of both species. For S. tabernaemontani, under the warming of 2.0 and 3.5 ℃ treatments, the spike length was increased by 82.9% and 89.0%, the spikelet number was increased by 133.3% and 150.0%, the biomass of each individual was increased by 10.1% and 89.6%, and the rate between biomass of per plant panicle and total biomass was increased by 79.5% and 409.3%, respectively. For S. stoloniferum, under the warming of 2.0 and 3.5 ℃ treatments, the spike length was increased by 66.1% and 95.2%, and the rate between biomass of per plant panicle and total biomass was increased by 878.8% and 1052.6%, respectively. Warming significantly increased seed yield of both species. Under the warming of 2.0 and 3.5 ℃ treatments, the seed yield per panicle of S. tabernaemontani was increased by 33.7% and 58.3%, respectively. For S. stoloniferum, the seed yield was increased by 3.4% and 69.5%, respectively. Under the warming of 2.0 and 3.5 ℃ treatments, the seed length of S. tabernaemontani was increased by 5.4% and 6.9%, and the seed length/width was increased by 9.1% and 5.3%, respectively. Warming had no significant effects on the seed shape of S. stoloniferum. The maximum and minimum temperatures were dominant factors affecting seed reproductions of both species. The advance of growing season, the prolonging of nutrition growing period, and accumulation of organic matter induced by warming would provide sufficient nutrient and energy accumulation for the reproduction and development of plants, which would promote seed reproduction capability of both species under the warming conditions.

Effects of soil warming on specific respiration rate and non-structural carbohydrate concentration in fine roots of Chinese fir seedlings.

SONG Tao-tao, CHEN Guang-shui, SHI Shun-zeng, GUO Run-quan, ZHENG Xin, XIONG De-cheng, CHEN Wang-yuan, CHEN Ting-ting

2018, 29(3):  705-712.  doi:10.13287/j.1001-9332.201803.009

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A field mesocosm experiment with Chinese fir (Cunninghamia lanceolata) seedlings was conducted in Chenda State-Owned Forest Farm, Sanming, Fujian Province. The effects of soil warming (ambient +5 ℃) on specific respiration rates and nonstructural carbohydrate (NSC) concentrations in fine roots were measured by the ingrowth core method, to reveal the belowground responses and the adaptability of Chinese fir to global warming. The results showed that soil warming caused significant changes of fine root NSC in the second year. The NSC and starch concentrations in 0-1 mm fine roots, and the NSC and sugar concentrations in 1-2 mm fine roots decreased signifi-cantly in January. The NSC, sugar and starch concentrations in 0-1 mm roots and the starch concentration in 1-2 mm roots increased in July. Soil warming had no significant effect on fine root NSC in the third year. The specific root respiration rate of the 0-1 mm roots significantly increased in July of the second year but significantly decreased in July of the third year in the warmed plots. Compared with the 0-1 mm roots, soil warming had no significant effect on the specific root respiration rate of the 1-2 mm roots. In conclusion, the responses of fine root respiration to soil warming depended on the duration of warming. Fine root respiration partly acclimated to soil warming with increasing duration of soil warming, which kept fine root NSC being relatively stable.

Simulating the effects of climate change and fire disturbance on aboveground biomass of boreal forests in the Great Xing’an Mountains, Northeast China.

LUO Xu, WANG Yu-li, ZHANG Jin-quan

2018, 29(3):  713-724.  doi:10.13287/j.1001-9332.201803.011

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Predicting the effects of climate warming and fire disturbance on forest aboveground biomass is a central task of studies in terrestrial ecosystem carbon cycle. The alteration of temperature, precipitation, and disturbance regimes induced by climate warming will affect the carbon dynamics of forest ecosystem. Boreal forest is an important forest type in China, the responses of which to climate warming and fire disturbance are increasingly obvious. In this study, we used a forest landscape model LANDIS PRO to simulate the effects of climate change on aboveground biomass of boreal forests in the Great Xing’an Mountains, and compared direct effects of climate warming and the effects of climate warming-induced fires on forest aboveground biomass. The results showed that the aboveground biomass in this area increased under climate warming scenarios and fire disturbance scenarios with increased intensity. Under the current climate and fire regime scenario, the aboveground biomass in this area was (97.14±5.78) t·hm^-2, and the value would increase up to (97.93±5.83) t·hm^-2 under the B1F2 scenario. Under the A2F3 scenario, aboveground biomass at landscape scale was relatively higher at the simulated periods of year 100-150 and year 150-200, and the value were (100.02±3.76) t·hm^-2 and (110.56±4.08) t·hm^-2, respectively. Compared to the current fire regime scenario, the predicted biomass at landscape scale was increased by (0.56±1.45) t·hm^-2 under the CF2 scenario (fire intensity increased by 30%) at some simulated periods, and the aboveground biomass was reduced by (7.39±1.79) t·hm^-2 in CF3 scenario (fire intensity increased by 230%) at the entire simulation period. There were significantly different responses between coniferous and broadleaved species under future climate warming scenarios, in that the simulated biomass for both Larix gmelinii and Betula platyphylla showed decreasing trend with climate change, whereas the simulated biomass for Pinus sylvestris var. mongolica, Picea koraiensis and Populus davidiana showed increasing trend at different degrees during the entire simulation period. There was a time lag for the direct effect of climate warming on biomass for coniferous and broadleaved species. The response time of coniferous species to climate warming was 25-30 years, which was longer than that for broadleaf species. The forest landscape in the Great Xing’an Mountains was sensitive to the interactive effect of climate warming (high CO₂ emissions) and high intensity fire disturbance. Future climate warming and high intensity forest fire disturbance would significantly change the composition and structure of forest ecosystem.

Sap flow characteristics of Quercus liaotungensis in response to sapwood area and soil moisture in the loess hilly region, China.

LYU Jin-lin, HE Qiu-yue, YAN Mei-jie, LI Guo-qing, DU Sheng

2018, 29(3):  725-731.  doi:10.13287/j.1001-9332.201803.019

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To examine the characteristics of sap flow in Quercus liaotungensis and their response to environmental factors under different soil moisture conditions, Granier-type thermal dissipation probes were used to measure xylem sap flow of trees with different sapwood area in a natural Q. liaotungensis forest in the loess hilly region. Solar radiation, air temperature, relative air humidity, precipitation, and soil moisture were monitored during the study period. The results showed that sap flux of Q. liaotungensis reached daily peaks earlier than solar radiation and vapor pressure deficit. The diurnal dynamics of sap flux showed a similar pattern to those of the environmental factors. Trees had larger sap flux during the period with higher soil moisture. Under the same soil moisture conditions, trees with larger diameter and sapwood areas had significantly higher sap flux than those with smaller diameter and sapwood areas. Sap flux could be fitted with vapor pressure deficit, solar radiation, and the integrated index of the two factors using exponential saturation function. Differences in the fitted curves and parameters suggested that sap flux tended to reach saturation faster under higher soil moisture. Furthermore, trees in the smaller diameter class were more sensitive to the changes of soil moisture. The ratio of daily sap flux per unit vapor pressure deficit under lower soil moisture condition to that under higher soil moisture condition was linearly correlated to sapwood area. The regressive slope in smaller diameter class was larger than that in bigger diameter class, which further indicated the higher sensitivity of trees with smaller diameter class to soil moisture. These results indicated that wider sapwood of larger diameter class provided a buffer against drought stress.

Effects of stand density on understory species diversity and soil physicochemical properties of Pinus massoniana plantation.

SUN Qian-hui, WU Xia, WANG Mei-zhen, ZHANG Liu-hua, YAO Xiao-lan, QI Jin-qiu, HAO Jian-feng

2018, 29(3):  732-738.  doi:10.13287/j.1001-9332.201803.004

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We analyzed understory species diversity, soil physicochemical traits and their relationships in the 25-year-old non-commercial Pinus massoniana plantations with five different stand densities, i.e., 1057, 1136, 1231, 1383 and 1515 trees·hm^-2, in Wenfeng Mountain, Xinjin District, Sichuan Province, China. The results showed that a total of 110 species were found, belonging to 57 families and 98 genera. With the increase of tree density, the understory species showed a succession pattern from positive to moderate to shady. Different densities had significant effects on the contents of total potassium and organic matter in the soils. With the increase ofdensity, the contents of organic matter and total potassium in understory vegetation first increased and then decreased. The trends of the relationship between both diversity and soil physiochemical characteristics and tree density were similar. Both of them increased with the increase of density, with the maximum value presented at the density of 1136 trees·hm^-2. The concentrations of total phosphorus, available potassium, total potassium and total nitrogen was closely related to plant diversity index. The results suggested that the density at 1136 trees·hm^-2 would be more beneficial to improve the stability of species diversity and soil fertility of P. massoniana non-commercial plantations in Wenfeng Mountain.

Optimizing vegetation pattern for the riparian buffer zone along the lower Yellow River based on slope hydrological connectivity.

CAO Zi-hao, ZHAO Qing-he, ZUO Xian-yu, DING Sheng-yan, ZHANG Yi-fan, XU Shan-shan, WU Dong-xing

2018, 29(3):  739-747.  doi:10.13287/j.1001-9332.201803.014

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Riparian buffer zone is important ecological transitional region between river and upland. Restoring the degraded vegetation system is important for preventing soil erosion, improving ecological environment and helping to achieve the sustainable development of ecosystems. Based on the scenario simulation of vegetation pattern and flow length index, we analyzed the responses of hydrological connectivity to vegetation pattern under different vegetation coverages and slope gradients, and explored the optimal vegetation pattern of soil and water conservation in riparian buffer zone in the lower reaches of the Yellow River. The results showed that the midslope-coarsness-clustered distribution of vegetation configuration, which exhibited the shortest flow length and the weakest hydrological connectivity, being the optimal vegetation pattern for controlling slope runoff generation and flow concentration. For the optimal vegetation pattern, its flow length increased with increasing slope length, namely, the longer slope length the more significant difference of hydrological connectivity between different slope gradients. Meanwhile, flow length of the optimal vegetation pattern decreased with increasing vegetation coverage. The differences between different slope gradients were obvious under low vegetation coverage, while it was unobvious on slope with vegetation coverage of 45%. Compared with the irregular variation trend of flow length on the actual vegetation slope, there was a consistent trend of first increase and then decrease on the simulated slope with the optimal vegetation pattern. Within the pre-set slope gradient range (5°-20°), the optimal vegetation pattern changed the variation of flow length between different slope gradients in the process of coverage change, which highlighted the influence of riparian buffer zone vegetation pattern on hydrological connectivity.

Characteristics of soil organic carbon mineralization in low altitude and high altitude forests in Wuyi Mountains, southeastern China.

NIE Yang-yi, WANG Hai-hua, LI Xiao-jie, REN Yin-bang, JIN Chang-shan, XU Zi-kun, LYU Mao-kui, XIE Jin-sheng

2018, 29(3):  748-756.  doi:10.13287/j.1001-9332.201803.015

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Examining the variations of soil organic carbon mineralization at different altitudes is crucial for better understanding of soil organic carbon (SOC) dynamics. We selected the low altitude and high altitude broad-leaved forest soils in Wuyi Mountains as the research object, and incubated them under particular annual average temperature (17 and 9 ℃, respectively) in laboratory to investigate the difference of SOC mineralization characteristics. The results showed that the cumulative SOC mineralization had no significant difference between forest soils at low and high altitude in a 126-day incubation period under ambient temperature. Soil organic carbon content of high altitude soil was significantly higher than that from low altitude. The dynamics of SOC mineralization could fitted by the first-order kinetics. Both mineralization potential (C_P) and mineralization rate constant (K) values of two soils had no significant difference, but C_P/SOC value and mineralization ratio were significantly higher at low altitude, indicating that the carbon sequestration capacity of low altitude soil was relatively lower than that of high altitude under ambient temperature. Soil microbial biomass carbon and microbial quotients were significantly higher than that of low altitude with the increase of incubation time, indicating that the ability of microbial carbon assimilation was greater at high altitude. On the other hand, the activities of β-1,4-glucosidase and cellobiohydrolase in high altitude soil were higher, suggesting that more labile carbon would be decomposed by soil microbes. The carbon sequestration capacity and microbial carbon utilization efficiency in high altitude soil would be reduced and thus result in a decline of soil organic carbon storage under the scenarios of climate warming.

Effects of naphthalene on soil respiration, dissolved organic matter and microbial biomass in the subalpine forest of western Sichuan, China.

YANG Fan, YANG Wan-qin, WU Fu-zhong, XUE Qiao, LIU Yu-wei, GUO Cai-hong, CHEN Ya, TAN Bo

2018, 29(3):  757-764.  doi:10.13287/j.1001-9332.201803.002

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The effects of naphthalene on soil respiration, dissolved organic matter and microbial biomass, and its inhibition efficiency for soil fauna of subalpine forest in western Sichuan were studied by in situ control experiment. The results showed that naphthalene application significantly inhibited the individual density and group number of soil macro- and meso-/micro- arthropods, with the individual density being decreased by 76.3%-78.5% and 83.3%-84.8% respectively, and the number of groups being decreased by 48.3%-56.1% and 45.8%-58.3%, respectively. The seasonal dynamics of soil respiration rate showed single peak curves in both naphthalene treatment and control. The lowest and the highest soil respiration rates were observed in February and August, respectively. The naphthalene treatment had little effect on soil respiration. Compared with the control, naphthalene treatment significantly reduced the contents of soil dissolved carbon and dissolved nitrogen in August and October as well as microbial biomass carbon (MBC) in April and August, but increased MBC/MBN in April. The naphthalene treatment and sampling time significantly interacted to affect the MBC and MBN, but had no significant effect on individual density, the number of groups of soil fauna and DC content. In all, naphthalene as biocide could effectively inhibit the soil arthropods and had no significant effect on soil respiration, but it had varying degrees of effects on soil carbon and nitrogen components in subalpine forest of western Sichuan.

Characteristics of soil moisture variation in different land use types in the hilly region of the Loess Plateau, China.

TANG Min, ZHAO Xi-ning, GAO Xiao-dong, ZHANG Chao, WU Pu-te

2018, 29(3):  765-774.  doi:10.13287/j.1001-9332.201803.013

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Soil water availability is a key factor restricting the ecological construction and sustainable land use in the loess hilly region. It is of great theoretical and practical significance to understand the soil moisture status of different land use types for the vegetation restoration and the effective utilization of land resources in this area. In this study, EC-5 soil moisture sensors were used to continuously monitor the soil moisture content in the 0-160 cm soil profile in the slope cropland, terraced fields, jujube orchard, and grassland during the growing season (from May to October) in the Yuanzegou catchment on the Loess Plateau, to investigate soil moisture dynamics in these four typical land use types. The results showed that there were differences in seasonal variation, water storage characteristics, and vertical distribution of soil moisture under different land use types in both the normal precipitation (2014) and dry (2015) years. The terraced fields showed good water retention capacity in the dry year, with the average soil moisture content of 0-60 cm soil layer in the growing season being 2.6%, 4.2%, and 1.8% higher than that of the slope cropland, jujube orchard, and grassland (all P<0.05). The water storage of 0-160 cm soil profile was 43.90, 32.08, and 18.69 mm higher than that of slope cropland, jujube orchard, and grassland, respectively. In the normal precipitation year, the average soil moisture content of 0-60 cm soil layer in jujube orchard in the growing season was 2.9%, 3.8%, and 4.5% lower than that of slope cropland, terraced fields, and grassland, respectively (all P<0.05). In the dry year, the effective soil water storage of 0-160 cm soil profile in the jujube orchard accounted for 35.0% of the total soil water storage. The grey relational grade between the soil moisture in the surface layer (0-20 cm) and soil moisture in the middle layer (20-100 cm) under different land use types was large, and the trend for the similarity degree of soil moisture variation followed terraced fields > grassland > slope cropland > jujube orchard. The slope cropland in this area could be transformed into terraced fields to improve the utilization of precipitation and promote the construction of ecological agriculture. Aiming at resolving the severe water shortage in the rain-fed jujube orchard for the sustainable development of jujube orchard in the loess hilly region, appropriate water management measures should be taken to reduce the water consumption of jujube trees and other inefficient water consumption.

Non-structural carbohydrates characteristics of different forest layers in monsoon broad-leaved evergreen forest in Pu’er, Yunnan Province, China.

LIU Wan-de, SU Jian-rong, LI Shuai-feng, XU Chong-hua, LANG Xue-dong, HUANG Xiao-bo, ZHONG Hua

2018, 29(3):  775-782.  doi:10.13287/j.1001-9332.201803.005

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Based on cluster analysis of species vertical stratification, the variations in concentration, allocation and seasonal dynamics of non-structural carbohydrates were investigated in a monsoon broad-leaved evergreen forest in Pu’er, Yunnan Province. The results showed that the concentrations of soluble sugar (3.9%) and nonstructural carbohydrates (NSC, 13.3%) were the highest in the sub-canopy. In contrast, the sugar/starch (0.76) of understory was the lowest. There was no significant difference in starch content among three forest layers. For all forest stories, the soluble sugar was mainly allocated to leaves and the roots had more starch and NSC. The soluble sugar contents in leaves and trunks of sub-canopy species were higher than canopy and understory species. There were no significant differences in soluble sugar content of twigs and roots among three different forest layers. The starch content of leaves increased with decreasing height of forest layers. In contrast, the lowest starch content (10.7%) of roots was in understory. There was no significant difference in starch content of twigs and trunks among three different forest layers. The NSC content of leaves was lower in canopy (10.7%) than that in sub-canopy (12.3%) and understory (12.0%). The lowest NSC content of roots was in understory (14.2%). The lowest sugar/starch of leaves, twigs, and trunks presented in understory, while the lowest sugar/starch of roots presented in canopy (0.79). There were dramatic seasonal variations in concentrations and components of NSC. The concentration of soluble sugar and the sugar/starch were higher in the rainy season than that in the dry season. However, the concentration of starch and NSC were higher in the dry season than in the rainy season. The variations in concentration of NSC and its components among forest layers indicated that species with different heights varied in their utilization strategies of carbon, which partly explained species coexistence.

Biomass and morphological characteristics of fine roots and their affecting factors in diffe-rent vegetation restoration stages in depressions between karst hills.

SU Liang, SONG Tong-qing, DU Hu, ZENG Fu-ping, WANG Hua, PENG Wan-xia, ZHANG Fang, ZHANG Jia-yong

2018, 29(3):  783-789.  doi:10.13287/j.1001-9332.201803.006

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This study focused on four vegetation restoration stages of grasslands, shrublands, secondary forests and primary forests in the typical karst peak-cluster depression. The soil core method was used to collect fine roots with 2 mm or less in diameter in three layers (0-10, 10-20, 20-30 cm). The biomass, morphological characteristics of fine roots and their relationship with soil properties were analyzed. The results showed that fine root biomass ranged between 194.63 and 255.19 g·cm^-2 in different vegetation restoration stages. Most of fine roots distributed in the surface soil of 0-10 cm, which accounted for more than 60% of the total biomass in the soil layer of 0-30 cm. No significant difference was found among different stages in fine root biomass. There was significant difference among different stages in the specific root length and specific surface area of fine roots. Both parameters were gradually decreased with vegetation forward restoration from grassland to primary forest. More than 66% root length and 64% root area were distributed in the surface soil of 0-10 cm. The length and area of most of the fine root were in the diameter class of 0-0.5 mm and 0.5-1mm, respectively. These two levels of the root length and root area accounted for more than 87% and 72% of the total amount, respectively. Results from the redundancy analysis showed that there were different correlations between karst peak-cluster depression vegetation community characteristics and soil properties, with soil organic carbon, available potassium, and total nitrogen having a great influence on the characteristics of fine roots. It is an effective strategy for plants to better adapt to the habitats.

The impact of phylogenetic uncertainty on the metrics of community phylogenetic structure.

CAI Jia-yao, DING Yuan-yuan, Tong Xin, WANG Ren-ren, GONG Xiao-ling, CHEN Xiao-yong, SHEN Guo-chun

2018, 29(3):  790-796.  doi:10.13287/j.1001-9332.201803.039

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Phylogeny has been widely used to quantify community phylogenetic structure and to infer the underlying mechanism. Many studies, however, neglected phylogeny uncertainty and its potential impact on community phylogenetic structure. In this study, we explored the potential impact of phylogenetic uncertainty among 150 species in a 20 hm² plot in Tiantong, Zhejiang. One consensus tree and 999 phylogenetic trees representing the phylogenetic uncertainty were estimated based on two cpDNA fragments (rbcL and matK). Combined with the species distribution data, community phylogenetic structure was quantified by two common indices (NRI and NTI) and their significances were tested by the independent swap null model. Our results showed that tree topology and node age showed a large uncertainty. The uncertainty was larger for young species and significantly increased with mean phylogenetic distance. Phylogenetic uncertainty increased the variation of both standardized NRI and NTI in each quadrat. These impacts were independent between both indices in either spatial pattern or the degree of impact. NRI was more sensitive than NTI to the uncertainty. At community scale, phylogenetic uncertainty also affected the variation of the mean standardized NRI and NTI of all quadrats, with mean standard deviation of 0.37 and 0.077, respectively. Such a result suggests that mean standardized NRI at community level was more vulnerable to the phylogenetic uncertainty, which is consistent with the result at the sample level. Our findings showed that phylogenetic uncertainty could add different variation into the NRI and NTI series indices and might increase biases in the quantification of community phylogenetic structure and its underlying ecological processes. Our results implied that non-random community phylogenetic structure was probably overestimated in the previous studies which ignored phylogenetic uncertainty.

Effects of exogenous glucose on growth and root nitrogen metabolism in Malus baccata.

LANG Dong-mei, QIN Si-jun, ZHU Zi-tan, LYU De-guo

2018, 29(3):  797-804.  doi:10.13287/j.1001-9332.201803.007

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To examine the effects of external glucose on growth, root architecture and nitrogen metabolism of Malus baccata seedlings in low carbon soil condition, Malus baccata seedlings were grown in sandy soil with the concentration of soil organic matter being 0.65%. The experiment consisted of three treatments: Control, with 2 g·kg^-1 glucose that equal to the ambient microbial biomass carbon (MBC), and with 10 g·kg^-1 glucose that was five times higher than the ambient MBC. The plant height, biomass, total root length and superficial area of the five times MBC group were 12.3%, 26.4%, 23.2% and 14.6% higher than that of the control, respectively. Root diameter, root volume and average diameter exhibited no significant difference under glucose treatments. The root activity was significantly increased under equal and five times MBC-glucose treatments, and reached its peak at 3 d and 15 d, about 119.1% and 75.7% higher than the control, respectively. Exogenous glucose addition significantly enhanced the concentrations of NO₃^-, NO₂^- and NH₄⁺ in roots. The activities of nitrate reductase, glutamine synthetase, glutamate dehydrogenase, glutamate synthase, glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase were substantially increased in the roots, especially under five times MBC treatment. Five times higher than the ambient MBC of external carbon source promoted biomass accumulation, root growth, morphogenesis and N absorption of plants in low carbon sandy soil.

Module growth and biomass allocation of Chloris virgate clone at different growth stages in Songnen Plain, China.

TIAN Xue, LI Hai-yan, YANG Yun-fei

2018, 29(3):  805-810.  doi:10.13287/j.1001-9332.201803.001

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The growth characteristic and strategies of Chloris virgate at different growth stages were examined in Songnen Plain by analyzing the quantitative characters and biomass allocation of aboveground and belowground parts at shooting and ripening stages in C. virgate population, with a large amount of sampling. The results showed that height, total root length, total root surface area, root volume, aboveground biomass, belowground biomass, and total biomass were significantly different between the two growth stages. There was power allometric relationship between total biomass and biomass allocation of aboveground and belowground, respectively. At shooting stage, there was a significant linear isometric growth between the total biomass and the number of ramets, total root length, total root surface area and root volume, but there was a power allometric growth at ripening stage. C. virgate clone showed different growth strategies under different growth stages, with a priority expansion strategy of clonal outer space at shooting stage and a complementary and expansive strategy in the inner and outer space of the clones at ripening stage.

Physiological integration of growth and photosynthesis of Zoysia japonica clonal ramets under nutrient heterogeneity.

XU Su-nan, LIU Yi-chen, LIU Yan-hong, CHEN Zhong-lin, LI Yue, ZHANG Li-hong

2018, 29(3):  811-817.  doi:10.13287/j.1001-9332.201803.003

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This study was carried out to analyze the changes of growth and photosynthesis of clonal ramets under nutrient heterogeneity, where the connected and disconnected ramets were treated with different nutrient levels. The results showed that under the nutrient heterogeneity the parent ramets in middle or high nutrient levels improved leaf length, leaf width, root mass, leaf mass, net photosynthetic rate, stomatal conductance, transpiration rate and water use efficiency of the connected daughter ramets, with an increase of 16.0%, 8.3%, 24.4%, 58.1%, 30.3%, 54.0%, 9.2% and 21.9% in high nutrient level, respectively, but reduced the root/shoot and intercellular CO₂ concentration of the connected daughter ramets, with a decreases of 21.6% and 31.5% in high nutrient level, respectively. In contrast, the daughter ramets in the middle or high nutrient level had no significant impacts on the growth and photosynthesis of the connected parent ramets. There was a physiological integration from the parent ramets to the daughter ramets. The larger the nutrient differences of ramets was, the stronger the intensity of physiological integration was. The daughter ramets were the unidirectional beneficiary from the physiological integration, as the daughter ramets benefited from the parent ramets but had no positive effects on the daughter ramets.

Effects of cultivation patterns on wheat yield and grain nutrient concentration in dryland.

HE Hong-xia, WANG Zhao-hui, BAO Ming, MA Xiao-long, SHE Xu, HE Gang, QIU Wei-hong

2018, 29(3):  818-826.  doi:10.13287/j.1001-9332.201803.027

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A field experiment was conducted to examine the effects of plastic film mulching (PM), straw retention (SR) and planting green manure (GM) on grain yield and nutrient concentrations of winter wheat. Compared to the traditional pattern (TP), plastic film mulching showed no significant effect on the average yield over the three years but increased the average phosphorus (P) uptake and concentration in grain by 8.4% and 13.0%, respectively. The average uptake of nitrogen (N), sulfur (S) and iron (Fe) was decreased by 12.6%, 15.0% and 11.1%, and the corresponding concentration was decreased by 12.1%, 12.9% and 10.1%, respectively. There was no significant effect on grain zinc (Zn) concentration. Straw retention decreased grain yield by 12.1%, reduced the average uptake of N, S and Fe decreased by 22.5%, 21.0% and 19.8%, and their corresponding concentration by 10.1%, 9.4% and 3.8%, respectively. The average uptake of P in grain was decreased by 9.8% with straw retention, while the P concentration was increased by 5.0%. There was no significant effect of straw retention on Zn concentration in grain. Planting green manure decreased the grain yield by 12.1%. It had no significant effect on the average uptake of N and Zn, but increased the grain N and Zn concentration by 12.1% and 12.6%, respectively. It showed no impact on P, S and Fe concentration in grain. The discordance between variation of grain yield and its nutrient uptake under different cultivations was the key reason for the changes of their nutrient concentration. Considering the potential adverse effects of plastic film mulching and straw retention on the quantity and quality of grain yield, suitable N fertilization should be applied to ensure the nutrient requirement for grain yield and regulate the uptake and utilization of N, S and Fe for improving the grain quality. Planting green manure could improve soil fertility and increase grain N and Zn concentration, but the yield reduction deserves more attention.

Characteristics of CO₂ flux and its influence factors over winter wheat agroecosystem in the North China Plain.

WU Dong-xing, LI Guo-dong, KANG Qiong-qiong, ZHANG Xi, Cao Zi-hao, LI Zhen

2018, 29(3):  827-838.  doi:10.13287/j.1001-9332.201803.012

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Using CO₂ flux data of winter wheat recorded by eddy covariance system, combined with the meteorological data, we examined the diurnal variations of CO₂ fluxes in four growth stages (tillering stage, overwintering stage, jointing stage and filling stage) of winter wheat in an agroecosystem of the North China Plain from 2013 to 2014. The seasonal variation of net ecosystem exchange and its relationship with meteorological factors were investigated. The results showed that the net ecosystem exchange in the whole growing season was -360.15 g C·m^-2. The gross primary productivity in the whole growing season was 1920.01 g C·m^-2. The winter wheat agroecosystem had strong capacity in carbon sequestration. The CO₂ fluxes showed an obvious diurnal and seasonal variation characteristics in winter wheat agroecosystem. This ecosystem was a carbon source in tillering stage, while it was a carbon sink in overwintering stage, jointing stage and filling stage. The mean value of apparent initial light energy utilization was 0.03 mg CO₂·μmol^-1. The mean value of ecosystem production was 1.53 mg CO₂·m^-2·s^-1 when light was saturated. The monthly average value of ecosystem respiration was 193.92 g C·m^-2·month^-1. The net ecosystem exchange and photosynthetically active radiation had a significant correlation in four growth stages of winter wheat. The correlations between net ecosystem exchange and vapor pressure deficit were significant in all the growth stages. There was a positive correlation between daily total net ecosystem exchange and soil temperature in tillering stage, overwintering stage and filling stage, but a negative correlation between them in jointing stage.

Soil quality assessment under different cropping system and straw management in farmland of arid oasis region.

ZHANG Peng-peng, PU Xiao-zhen, ZHANG Wang-feng

2018, 29(3):  839-849.  doi:10.13287/j.1001-9332.201803.030

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To reveal the regulatory mechanism of agricultural management practices on soil quality, an experiment was carried out to study the different cropping system and straw management on soil organic carbon and fractions and soil enzyme activity in farmland of arid oasis region, which would provide a scientific basic for enhancing agricultural resources utilization and sustainable development. In crop planting planning area, we took the mainly crop (cotton, wheat, maize) as research objects and designed long-term continues cropping and crop rotation experiments. The results showed that the soil organic carbon (SOC), soil microbial biomass C, labile C, water-soluble organic C, and hot-water-soluble organic C content were increased by 3.6%-9.9%, 41.8%-98.9%, 3.3%-17.0%, 11.1%-32.4%, 4.6%-27.5% by crop rotation compared to continues cropping, and 12%-35.9%, 22.4%-49.7%, 30.7%-51.0%, 10.6%-31.9%, 41.0%-96.4% by straw incorporated compared to straw removed, respectively. The soil catalase, dehydrogenase, β-glucosidase, invertase glucose, cellulase glucose activity were increased by 6.4%-10.9%, 6.6%-18.8%, 5.9%-15.3%, 10.0%-27.4%, 28.1%-37.5% by crop rotation compared to continues cropping, and 31.4%-47.5%, 19.9%-46.6%, 13.8%-20.7%, 19.8%-55.6%, 54.1%-70.9% by straw incorporated compared to straw removed, respectively. There were significant positive linear correlations among SOC, labile SOC fractions and soil enzyme. Therefore, we concluded that labile SOC fractions and soil enzyme were effective index for evaluating the change of SOC and soil quality. Based on factor analysis, in arid region, developing agricultural production using cropland management measures, such as straw-incorporated and combined short-term continues cotton and crop rotation, could enhance SOC and labile SOC fractions contents and soil enzyme activity, which could improve soil quality and be conducive to agricultural sustainable development.

Carbon footprint of wheat-summer direct-seeding peanut planting system in Shandong Pro-vince, China.

ZOU Xiao-xia, ZHANG Xiao-jun, WANG Yue-fu, WANG Ming-lun

2018, 29(3):  850-856.  doi:10.13287/j.1001-9332.201803.020

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Clarifying the carbon emissions in wheat-summer direct-seeding peanut planting (W-P) system could help realize the synergistic effects of high yield and low carbon emissions. Based on whole life cycle method, we constructed a carbon footprint model to calculate the carbon emissions of W-P system. We found that the net income of W-P system was 71.2%-88.3% higher than that of wheat-maize rotation (W-M) system. The carbon emissions per unit area under W-P system was 6977.9-8018.5 kg·hm^-2, being 6.2% higher than that of W-M system. The carbon emission of per net income under W-P system was 0.23-0.28 kg CO₂-eq·yuan^-1, which was 37.4%-44.1% lower than that of W-M system. Combining the net income and carbon emissions of per net income, W-P system could achieve synergistic effects of high yield and low carbon emissions, which would fulfill the targets of agricultural supply-side structural reform with optimizing supply, enhancing quality and efficiency, and increasing income of peasants.

Responses of organic carbon mineralization and priming effect to phosphorus addition in paddy soils.

TANG Mei-ling, WEI Liang, ZHU Zhen-ke, LI Huan, ZHOU Ping, GE Ti-da, WU Jin-shui,WANG Guang-jun

2018, 29(3):  857-864.  doi:10.13287/j.1001-9332.201803.023

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To understand the coupled controlling of carbon (C) and phosphorus (P) on the minera-lization of soil organic carbon and amended substrates in paddy soil, we investigated the effects of P addition on the decomposition of organic carbon and its induced priming effect by using ¹³C isotope probing technique in microcosm. The results showed that P addition accelerated the release of CO₂ but inhibited the release of CH₄, leading to 53.1% reduction of total accumulated CH₄ and 70.5% reduction of the ¹³CH₄ derived from exotic glucose-¹³C. P addition altered the carbon distribution during the microbial turnover progress, with 3.6% of glucose-¹³C being transferred into the labile carbon pool, therein significantly increased potential of the mineralization rate of exogenous C. A transient negative priming effect was observed in the early stage of incubation. With time prolonging, the priming effect on CO₂ emission (PE_CO2) generally increased and then decreased after a peak. The priming effect on CH₄ emission (PE_CH4) kept increasing and finally fluctuated at a relative stable value until the end of the experiment (100 days). P addition increased PE_CO2 by 32.3% but reduced PE_CH4 by 93.4%. Results from the RDA and Pearson analysis showed that electric conductivity, oxidation-reduction potential and dissolved organic carbon significantly affected soil C mineralization. There were significantly negative correlations between available phosphorus (Olsen-P) and ¹³CH₄, and between Olsen-P and PE_CH4. In conclusion, with the addition of exogenous organic matter, P application could reduce CH₄ emissions and inhibit its priming effect, acce-lerate the mineralization of SOC, probably improve the nutrient supply, and thus enhance the avai-lability of organic C and promote C cycling in paddy soil.

Responses of main characters of root system to salt stress among cotton varieties with diffe-rent salt tolerance.

WANG Qing-hui, HAN Wei, HOU Yin-ying, FENG Lin, YE Zu-peng, GU Hui-min, CHEN Bo-lang

2018, 29(3):  865-873.  doi:10.13287/j.1001-9332.201803.025

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A pot experiment was carried out to test the effects of salt levels on root morphology as well as the relationship between root morphology and salt tolerance with four cotton cultivars (salt-sensitive cultivar CCRI45, weak salt-resistance cultivar XLZ17, moderate salt-resistance cultivar XLZ13 and salt-resistance cultivar CCRI35). Results showed that dry mass and K⁺/Na⁺ ratio of cotton root and leaf were significantly reduced by salt stress. Dry mass of root and leaf and K⁺/Na⁺ ratio of root of cultivars XLZ13 and CCRI35 were 69.3%-104.4%, 24.8%-45.3% and 25.0%-45.8% higher than those of cultivar CCRI45, respectively. Root development was significantly restrained by salt stress. Total root length, total root surface area and total root volume of cultivars XLZ13 and CCRI35 were 15.2%-85.8%, 12.0%-68.5% and 31.7%-217.8% higher than those of cultivar CCRI45, respectively. Furthermore, the length of fine and middle roots, root surface area and root volume of cultivars XLZ13 and CCRI35 in 0-10 cm soil layer were 27.2%-73.9%, 39.6%-74.3% and 99.0%-309.7% higher than those of cultivar CCRI45, respectively. Results from principal component analysis showed that the variations of specific root length, root length ratio at 0-10 cm soil layer and fine root length ratio at 0-10 cm soil layer among cultivars was significant. Specific root length, root length ratio at 0-10 cm soil layer and fine root length ratio at 0-10 cm soil layer were the main root characters to distinguish different salt tolerant cotton cultivars. Results from the stepwise regression analysis showed that specific root length, coarse root length, coarse root area, and coarse root volume at 0-10 cm and 10-20 cm soil layers, as well as fine root area and middle root ratio at 0-10 cm soil layer were sensitive to salt. Salt tolerant cultivar adapted to salt stress through increasing root length ratio, fine length ratio, and specific root length.

Effects of spraying paclobutrazol at different stages on physiological characteristics, yield and quality of peanut.

ZHANG Jia-lei, GUO Feng, LI Xin-guo, YANG Sha, GENG Yun, MENG Jing-jing, FAN Zhong-xue, WAN Shu-bo

2018, 29(3):  874-882.  doi:10.13287/j.1001-9332.201803.028

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To explore the optimum stage of spraying with paclobutrazol (PBZ) for different peanut cultivars under high yield condition, we investigated the effects of spraying PBZ at different stages on chlorophyll content, root activity, protective enzymes, nitrogen and carbon metabolism enzymes of leaves, pod yield and kernel quality of peanut, with Huayu 20 and Huayu 25 as materials. The results showed that spraying PBZ at different stages increased root activity, chlorophyll content, SOD, POD, CAT, SS, SPS, PEPC activities and decreased the MDA content, NR, GS, GDH and GOGAT activities for pod setting stage of two cultivars. These results suggested that the effects would be more obvious at earlier spray time. For HY25, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 25 cm. For HY20, spraying PBZ when the main stem height was 25 cm decreased the activities of protective enzymes. Earlier spraying time to HY20 would lead to early senescence, lower chlorophyll content, root activity and carbon metabolism enzyme activity. For HY20, the most significant effects of spraying PBZ on those parameters of pod filling stage could be obtained when the main stem height was 30 cm. Our results indicated that PBZ treatments at the optimum stage could improve pod yield and economic coefficient of both cultivars and enhance the fat content and the relative content of oleic acid and the O/L. Under high yield condition, the optimum stage of spraying PBZ was 25 cm height of the main stem for HY25 and 30 cm for HY20.

Effects of light intensities after anthesis on the photosynthetic characteristics and chloroplast ultrastructure in mesophyll cell of summer maize (Zea mays L. ).

GAO Jia, CUI Hai-yan, SHI Jian-guo, DONG Shu-ting, LIU Peng, ZHAO Bin, ZHANG Ji-wang

2018, 29(3):  883-890.  doi:10.13287/j.1001-9332.201803.021

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We examined the changes of photosynthetic characteristics and chloroplast ultrastructure in mesophyll cell of summer maize in response to different light intensities in the field, with the summer maize hybrid Denghai 605 as experimental material. Two treatments of both shading (S) and increasing light (L) from flowering to physiological maturity stage were designed, with the ambient sunlight treatment as control (CK). Under shading treatment, poorly developed thylakoid structure, blurry lamellar structure, loose granum, large gap between slices and warping granum were the major characteristics in chloroplast. Meanwhile, photosynthetic rate (P_n), transpiration rate, stomatal conductance, chlorophyll content, and actual photo-chemical efficiency (Φ_PSII) decreased, whereas the maximal photochemical efficiency and non-photochemical quenching increased, which resulted in decreases in grain yield under shading treatment. However, a better development was observed in chloroplasts for L treatment, with the number of grana and lamellae increased and lamellae arranged compactly. In addition, P_n and Φ_PSII increased under L treatment, which increased grain yield. The chloroplast arrangement dispersed in mesophyll cells and chloroplast ultrastructure was destroyed after shading, and then chlorophyll synthesis per unit leaf area and photosynthetic capacity decreased. In contrast, the number of grana and lamellae increased and lamellae arranged compactly after increasing light, which are beneficial for corn yield.

Effects of exogenous spermidine and arbuscular mycorrhizal fungi on plant growth of cucumber.

WU Ya-sheng, GUO Shi-rong, ZHANG Jie, DU Nan-shan, SUN Jin

2018, 29(3):  891-898.  doi:10.13287/j.1001-9332.201803.022

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Effects of spermidine (Spd) and arbuscular mycorrhizal fungi (AMF) on the growth and photosynthesis of cucumber (Cucumis sativus L., cv. Jinchun 2) seedlings, fruit yield and quality, microorganism and enzymatic activity in rhizosphere were investigated. The results showed that combined Spd and AMF addition significantly promoted the growth of cucumber seedlings, increased the root activity, fruit production and quality, enhanced nutrients absorption of seedlings. Net photosynthetic rate, actual photochemical efficiency, light quantum efficiency, carboxylation efficiency and light respiration rate of cucumber seedlings were increased by combined addition of Spd and AMF. The abundance of bacteria and actinomycetes in the rhizosphere of cucumber seedlings were increased, but that of fungi was decreased. The activities of enzymes, including sucrase, neutral phosphatase, catalase, and urease, were enhanced. These results suggested that the light utilization efficiency of cucumber seedlings was improved by combined addition of Spd and AMF. The growth substrate has been changed from a low-fertility type caused by fungi to a high-fertility one caused by bacteria. The decomposition and transformation of organic phosphorus and nitrogen in substrate were increased by combined addition of Spd and AMF, and thus could provide more N and P for the growth and development of cucumber, which further led to enhanced seedling growth, higher yield and quality of fruits. Moreover, Spd could increase the infection rate of AMF in cucumber roots, and together they had a synergistic effect on the growth of cucumber. Our results suggest that it is an effective method to enhance the infection rate of AMF by using Spd.

Effects of exogenous 2,4-epibrassinolide on the growth and redox balance of cucumber seedlings under NaHCO₃ stress.

NIE Wen-jing, WANG Shuo-shuo, JING Xin, GONG Biao, WEI Min, YANG Feng-juan, LI Yan, SHI Qing-hua

2018, 29(3):  899-908.  doi:10.13287/j.1001-9332.201803.024

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The effects of 0.2 μmol·L^-1 exogenous 2,4-epibrassinolide (EBR) on the growth and reactive oxygen species metabolism of cucumber seedlings (‘Jinyan 4’ cucumber) under salt-alkaline stress (30 mmol·L^-1 NaHCO₃) were examined by hydroponics method. The results showed that NaHCO₃ stress significantly induced production of O₂^-· and accumulation of H₂O₂ in leaves and roots, resulting in the increases of MDA content and electrolyte leakage. Under NaHCO₃ stress, activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, dehydroascorbatereductase, monodehydrodroascorbate reductase, and glutathione reductase as well as contents of ascorbic acid and glutathione were firstly increased and then decreased with progress of stress time. Exogenous EBR application significantly increased the activities of antioxidant enzymes and contents of antioxidants as well as the ratio of AsA/DHA (dehydroascorbic acid) and GSH/GSSG (L-glutathione oxidized) in leaves and roots of cucumber under NaHCO₃ stress. Such changes improved the redox hemostasis in plants, reduced the level of reactive oxygen species, and alleviated the membrane lipid peroxidation. Together, they increased the alkaline tolerance of cucumber seedlings.

Effects of intercropping Chinese milk vetch on functional characteristics of soil microbial community in rape rhizosphere.

ZHOU Quan, WANG Long-chang, XING Yi, MA Shu-min, ZHANG Xiao-duan, CHEN Jiao, SHI Chao

2018, 29(3):  909-914.  doi:10.13287/j.1001-9332.201803.031

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The application of green manure is facing serious problems in purple soil region of southwest China. With the aim to explore the potential application of green manure, we examined the functional characteristics of soil microbial community in a system of Chinese milk vetch intercropped with rape. The innovations are the application of Chinese milk vetch in dry land of the southwest China and the establishment of new planting pattern of rape by providing empirical data. Results showed that the intercropping with Chinese milk vetch decreased the carbon resource use efficiency of microbial community in rape rhizosphere, especially for the utilization of carbohydrates. At the same time, Shannon index, Simpson index, and richness were reduced, but evenness index was increased by intercropping. Those results from cluster analysis and principal component analysis suggest that the soil microbial community composition was significantly different between monocropping and intercropping. The carbohydrates, amino acids and carboxylic acids were the sensitive carbon sources for differentiating the changes of the microbial community induced by monocropping and intercropping. Intercropping Chinese milk vetch could decrease functional activity, change community composition, and reduce diversity of soil microbial community in rape rhizosphere.

Effects of habitat conditions on the genetic diversity of Apis cerana cerana.

PANG Qian, ZHANG Wen-wen, WANG Kang, CHEN Xiao-mei, MENG Xiang-jin, JI Ting

2018, 29(3):  915-920.  doi:10.13287/j.1001-9332.201803.034

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To assess the effects of different habitat conditions on the genetic diversity of Apis cerana cerana, 2400 individual workers from 120 colonies in four localities of South Anhui mountainous area were analyzed using microsatellite DNA loci. Results showed that in the tea tree monoculture, the number of alleles, average expected heterozygosity and polymorphism information content showed no significant difference with those in the natural forest. The number of alleles and polymorphic information content in domesticated population were significantly different from those in the wild population. The average expected heterozygosity was not significantly different between those two populations. The number of alleles, the average expected heterozygous and polymorphic information content were significantly different from those in the wild for samples collected in 2006. There was significant genetic differentiation among populations, with an average differential coefficient of 0.32. Our results indicated that the cultivation of tea plantation in South Anhui would not affect the genetic structure and conservation of bees.

Effects of nutrient solution supply amount on yield, quality and volatile matter of tomato.

CAI Dong-sheng, LI Jian-ming, LI Hui, HU Xiao-hui, ZHANG Jun-heng

2018, 29(3):  921-930.  doi:10.13287/j.1001–9332.201803.026

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We examined the effects of different amounts of nutrient solution supply on the yield, quality and volatile substances of tomato fruit by substrate cultivation. Using tomato cultivar ‘HL2109’ as experimental material, four treatments were set, including Control: irrigating with 117 L pure water for each plant; T₁: irrigating each plant with 39.0 L of nutrient solution; T₂: irrigating each plant with 58.5 L of nutrient solution; T₃: irrigating each plant with 117 L of nutrient solution. The quality and volatile substances of tomato fruits were determined by using chemical method and SPME-GC-MS technique. The results showed that the yield per plant and the gross production increased and then decreased with the increases of nutrient solution supply. The yield of T₂ was the highest among all treatments. The yields of T₁, T₂ and T₃ were 29.3%, 72.6% and 47.0% higher than that in Control, respectively. The irrigation water use efficiency of T₁ was the highest and T₂ took second place, though the difference being not significant. The soluble solids content and sugar acid ratio of tomato fruits in T₂ were the highest, and the flavor and quality were significantly improved. The content of ascorbic acid and soluble protein gradually increased with the increases of nutrient solution supply. The contents of total soluble sugar and reducing sugar were first increased and then decreased, both being highest in T₂. Using GC-MS analysis, a total of 69 volatile compounds were detected. The total content of volatile compounds from T₁, T₂ and T₃ were higher than that in Control, which presented as T₂﹥T₁﹥T₃﹥CK. Among them, the content of volatile compounds from T₂ was 6971 μg·kg^-1, which was 1.97 times higher than that in the Control. The content from T₃ was 4070 μg·kg^-1, being 0.73 times of that in the Control. The contents of 1-Pentene-3-one, 6-Methyl-5-hepten-2-one, hexanal, hexanoic acid, Phenylacetaldehyde and cis-3-hexenal were highest in T₂ among all treatments. Moreover, the content of characteristic volatile compounds, the quantity and total content of volatile compounds were highest in T₂. Taken together, the T₂ treatment (irrigating each plant with 58.5 L of nutrient solution) had the best effects, with the quality and content of volatile compounds in tomato fruit being improved.

Fate of fertilizer nitrogen and soil nitrogen pool budget of Fuji apple from germination stage to new shoot growing stage.

WANG Fen, TIAN Ge, LIU Jing-jing, GE Shun-feng, JIANG Yuan-mao

2018, 29(3):  931-937.  doi:10.13287/j.1001-9332.201803.029

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¹⁵N trace technique were used to explore the fertilizer nitrogen (N) absorption and utilization, soil residue and soil nitrogen pool budget under different nitrogen fertilization levels (0, 50, 100, 150, 200, 250 kg·hm^-2) for five-year-old ‘Yanfu 3’/SH6/M. hupehensis Rehd. from germination stage to new shoot growing stage. The results showed that ¹⁵N were preferentially distributed to the roots and then transported to aboveground for the construction of new organs after N application in early spring. After the end of new shoot growing (two months later after N application), 5.9%-9.9% of fertilizer N was absorbed by apple tree, 29.8%-33.4% of fertilizer N was resided in 0-60 cm soil, and 56.7%-64.4% of fertilizer N was lost. With the increases of N application rate, the amount of fertilizer N absorbed by trees and the amount of soil residual N gradually increased, the utilization ratio of fertilizer N and soil residual ratio decreased, and the loss and the loss ratio of N were increased. With the increases of N application rates, the total balance of soil N changed from deficit to surplus, and the surplus increasing significantly with the increases of N application rates. The results indicated that low N application rate could cause a decrease of soil N fertility and the excessive application of nitrogen could increase the accumulation of N and increase the risk of N pollution. Fertilizer N levels showed a significant linear correlation with soil total N balance, with the regression equation being y=0.3511x-20.808 (R²=0.9927). In the stages from germination to new shoot growing, soil N pool reached balance when the N application rate was 59.27 kg·hm^-2.

Analysis of influence on spatial distribution of fishing ground for Antarctic krill fishery in the northern South Shetland Islands based on GWR model.

CHEN Lyu-feng, ZHU Guo-ping

2018, 29(3):  938-944.  doi:10.13287/j.1001-9332.201803.037

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Based on Antarctic krill fishery and marine environmental data collected by scientific observers, using geographically weighted regression (GWR) model, we analyzed the effects of the factors with spatial attributes, i.e., depth of krill swarm (DKS) and distance from fishing position to shore (DTS), and sea surface temperature (SST), on the spatial distribution of fishing ground in the northern South Shetland Islands. The results showed that there was no significant aggregation in spatial distribution of catch per unit fishing effort (CPUE). Spatial autocorrelations (positive) among three factors were observed in 2010 and 2013, but were not in 2012 and 2016. Results from GWR model showed that the extent for the impacts on spatial distribution of CPUEs varied among those three factors, following the order DKS>SST>DTS. Compared to the DKS and DTS, the impact of SST on the spatial distribution of CPUEs presented adverse trend in the eastern and western parts of the South Shetland Islands. Negative correlations occurred for the spatial effects of DKS and DTS on distribution of CPUEs, though with inter-annual and regional variation. Our results provide metho-dological reference for researches on the underlying mechanism for fishing ground formation for Antarctic krill fishery.

Subhabitat selection and differences of diet composition for Acanthogobius ommaturus in the Dongtan wetland of the Yangtze estuary, China.

ZHANG Heng, YE Jin-yu, ZHANG Ying-ying, JIN Shao-fei, ZHANG Sheng-mao

2018, 29(3):  945-952.  doi:10.13287/j.1001-9332.201803.033

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We examined the temporal and spatial variation in the abundance and diet composition of Acanthogobius ommaturus at three subhabitats (mudflat, salt marsh, and creek) of the Dongtan wetland of Yangtze Estuary with monthly field samplings from July 2015 to June 2016. The results showed that the samples of A. ommaturus were mainly composed of young individuals in the period of June-November, whereas no fish was collected during the other months. Most of the samples were collected in July (71) and only three individuals was collected in November. Most of the samples were collected (93) in creek, which was 5.2 and 4.9 times of those in mudflat and salt marsh, respectively. The diet of the A. ommaturus included 10 taxa and 30 prey species, dominated by shrimps. In the taxonomic level, the dominant preys were the Exopalaemon annandalei or other Exopalaemon sp. of shrimps, the Sesarma sp. of crabs and Micromecta quadriseta of insects. Compared with other taxonomic groups, the fish prey had relatively higher mass percentage but lower abundance percentage. The prey composition of A. ommaturus differed among subhabitats. The feeding level of A. ommaturus increased gradually from July to November and reached 3.0 in late autumn. The differences in the abundances of A. ommaturus among subhabitats would be induced by prey composition.

Sagittal otolith morphology and the relationship between its mass and the age of Liza haematocheila in the Yangtze Estuary, China.

JI Yan, ZHAO Feng, YANG Qin, MA Rong-rong, YANG Gang, ZHANG Tao, ZHUANG Ping

2018, 29(3):  953-960.  doi:10.13287/j.1001-9332.201803.040

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To examine the relationship of morphological characters of sagittal otolith and the age of Liza haematocheila in the Yangtze Estuary, we analyzed the morphological parameters of 324 pairs of otoliths extracted from 358 L. haematocheila specimens from the Yangtze Estuary in February to June of 2017. The results showed that sagittal otolith had rostrum, antirostrum and obvious central notch. The size and shape of sagittal otolith significantly changed with their growth, from regular melon seeds shape outline to long narrow leaf shape and increasing irregular wavy outline. The average density of sagittal otolith was 1.52 mg·mm^-2. The average rectangularity was 0.68. The length of sagittal otolith was 0.021%-0.047% of entire body length (BL), the width was 0.009%-0.021% of entire BL, and the mass was 0.045‰-0.731‰ of the entire body mass (BM). Otolith length (OL), otolith width (OW) and otolith mass (OM) were all significantly related to the BL, with the determination coefficient for OW and OM model being the highest (R²=0.928). The relationship between OM and BL was described best by exponential regression: OM=0.0009BL^1.8737(R²=0.967). The relationships between OM and age (A), BL and A were well fitted by multinomial regressions, respectively: OM=2.9262A²+4.8437A+2.1894 (R²=0.847), BL=-3.2248A²+102.54A+38.373 (R²=0.858). In addition, OM was linearly correlated with A. The estimated otolith’s ages from the model did not significantly variate from the real ages counting from annulus counts. Therefore, OM could be an effective parameter for the age estimation of L. haematocheila.

Draft of soil environmental function regionalization of China.

WU Bo, GUO Shu-hai, LI Bao-lin, ZHANG Ling-yan

2018, 29(3):  961-968.  doi:10.13287/j.1001-9332.201803.038

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Soil environmental function regionalization is of significance for soil environmental classification management in China. In this paper, we discussed the broad and narrow concept of soil environmental function and its corresponding attributes. Based on the constraint analysis on the soil environmental quality to function, relationship between soil environmental function and quality was illustrated. Compared with different methods and indices of soil environmental function regionalization, we established the index system of soil environmental function regionalization according to the soil environmental suitability and function. The proposed draft of soil environmental function regionalization included four first-class function types, 10 second-class function types, and 75 soil environmental functional areas. According to the differences among those functional areas, we proposed corresponding management countermeasures. The results provided scientific basis for the control and prevention of soil pollution and the control of regional risk in China.

Variations in growth response and cadmium accumulation of different gender Morus alba seedlings to combined treatments of Cd and acid rain.

ZANG Chang, LYU Zhi-qiang, DONG Lian-chun, XU Yi, YU Fei

2018, 29(3):  969-975.  doi:10.13287/j.1001-9332.201803.035

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To investigate sex-specific adaptive responses and cadmium accumulation of Morus alba seedlings, we analyzed growth parameters, photosynthetic capacity and chlorophyll fluorescence parameters, and Cd accumulation and allocation of Qiangsang 1 (female) and Nongsang 14 (male) under different treatments [cadmium (Cd, 100 mg·kg^-1), acid rain (AR, pH 3.0) and their combinations (Cd+AR)]. When exposed to Cd stress alone, females showed higher cadmium content in root, stem and leaf than males. The root, stem and total biomass, and maximum net photosynthetic rate (A_max) of males were significantly decreased, while those of females (except A_max) showed no significant changes. Cd had no effect on maximal photochemical efficiency (F_v/F_m), photochemical quenching coefficient (q_P), non-photochemical quenching coefficient (q_N) in both sexes. When exposed to Cd+AR stress, the total biomass and A_max of males and females decreased. Compared to Cd stress alone, the cadmium content in root and leaf of females significantly increased while those of males did not under Cd+AR. In addition, Cd+AR stress had no effect on F_v/F_m and q_P, but significantly increased q_N in both sexes. Our results suggested that females had greater tolerance than males when exposed to Cd stress alone in short term. Acid rain would decrease the tolerance of females to Cd stress, which might attribute to the enhanced absorption and accumulation of cadmium.

Terrain gradient effect of ecosystem service value in middle reach of Yangtze River, China.

YANG Suo-hua, HU Shou-geng, QU Shi-jin

2018, 29(3):  976-986.  doi:10.13287/j.1001-9332.201803.016

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Using land use data in the year 1995, 2005 and 2014, this study estimated the ecosystem service value (ESV) in each county located in the middle reach of Yangtze River and analyzed its spatiotemporal variation features and terrain gradient effects based on “the equivalent value per unit area of ecosystem services in China”. The results showed that ESV in the middle reach of Yangtze River was generally higher in mountainous area but lower in plain region, with an obvious terrain gradient effect. Specifically, the relationship of the relief degree of land surface (RDLS) and the ESV showed significant logarithm function at county scale with a high curve fitting degree of 0.53. The ESV increased from 400.35×10⁴ yuan·km^-2 to 554.57×10⁴ yuan·km^-2 with the increasing RDLS (grade 1-5) in 2014. During 1995-2004, the ecosystem service value variation changed from decreasing to stable with the increases of the RDLS. With a perspective of ecosystem service values, the value of food production and waste treatment service value decreased with the increase of the RDLS, while the others increased in general, such as the production of raw materials and gas regulation service value, because of the influences of dynamic land use structure in varied topography and distinct dominant ecosystem services from different land types.

Quantitative assessment of urban ecosystem services flow based on entropy theory: A case study of Beijing, China.

LI Jing-xin, YANG Li, YANG Lei, ZHANG Chao, HUO Zhao-min, CHEN Min-hao, LUAN Xiao-feng

2018, 29(3):  987-996.  doi:10.13287/j.1001-9332.201803.017

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Quantitative evaluation of ecosystem service is a primary premise for rational resources exploitation and sustainable development. Examining ecosystem services flow provides a scientific method to quantity ecosystem services. We built an assessment indicator system based on land cover/land use under the framework of four types of ecosystem services. The types of ecosystem services flow were reclassified. Using entropy theory, disorder degree and developing trend of indicators and urban ecosystem were quantitatively assessed. Beijing was chosen as the study area, and twenty-four indicators were selected for evaluation. The results showed that the entropy value of Beijing urban ecosystem during 2004 to 2015 was 0.794 and the entropy flow was -0.024, suggesting a large disordered degree and near verge of non-health. The system got maximum values for three times, while the mean annual variation of the system entropy value increased gradually in three periods, indicating that human activities had negative effects on urban ecosystem. Entropy flow reached minimum value in 2007, implying the environmental quality was the best in 2007. The determination coefficient for the fitting function of total permanent population in Beijing and urban ecosystem entropy flow was 0.921, indicating that urban ecosystem health was highly correlated with total permanent population.

A diachronic study on resettlers’ perceptions toward ecological relocation in world heritage site: A case study of Wulingyuan Scenic Area, China.

WANG Kai, CHEN Qin-chang, LI Zhi-miao

2018, 29(3):  997-1005.  doi:10.13287/j.1001-9332.201803.018

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Perceptions of residents in ecological resettlement area are important for evaluating the implementation effect of ecological relocation and sustainable development of world heritage site. With the residents from three different resettlement communities in Wulingyuan Scenic Area as the research object, we carried out a diachronic study on changes of the resettlers’ perceptions of ecological relocation at different times and the main driving factors based on systematic survey data in 2010 and 2016. The results showed that in the year 2010 and 2016, resettlers reacted negatively to the indicators such as “enhancement of employment opportunity”, “improvement of education and training opportunity”, “enhanced environment in scenic area”, “recognizing the identity change ‘from rural to non-rural’ after relocation”. They favored the indicators such as “undermining traditional value”, “lack of supervision during the implementation of policies”. In 2016, resettlers of different gender, age and average monthly income had substantial different opinions on the economic and psychological impacts of ecological relocation. Education and income level had great impacts on their opinions of ecological relocation policies. Resettlers relocated by the way of investment for developing perceived were more sensitive to the economic impacts. Economic and policy impacts became the dominant driving factors for their general perception of ecological relocation. They pay more attention to employment, children’s education opportunity as well as social security system for relocation.

Reviews

Research progress on DNA barcoding analysis methods.

YANG Qian-qian, LIU Su-wen, YU Xiao-ping

2018, 29(3):  1006-1014.  doi:10.13287/j.1001-9332.201803.032

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DNA barcode is a fragment of short DNA sequence from a standard part of the genome. DNA barcoding is an effective taxonomic method for species identification through analyzing the DNA barcodes. With the dramatic increasing of DNA barcode sequences, the analysis methods have developed rapidly, which promoted their applications in molecular identification for organisms. Since 2003, DNA barcoding has been widely used in species identification for animals, plants, fungi, etc. It has also robustly promoted the development of scientific disciplines, such as taxonomy, biodiversity science, and ecology. Based on review of DNA barcoding techniques, we summarized five main analysis methods on DNA barcodes, i.e. the genetic distance-, genetic similarity-, phylogenetic tree-, sequence characters-, and statistical classification-based methods. Moreover, we proposed a prospect for research and applications of DNA barcoding in the future.

Progress on the regulation of quorum sensing in wastewater treatment.

LI Song-ya, FEI Xue-ning, JIAO Xiu-mei, WANG Le, XING Yan-jun

2018, 29(3):  1015-1022.  doi:10.13287/j.1001-9332.201803.036

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Quorum sensing is a phenomenon that microorganisms secrete some signal molecules, when such molecules accumulate to a threshold level, which would realize the information communication by regulating specific gene expression. Quorum sensing, which is widely found in information communication of various microorganisms, regulates a variety of social behaviors, such as biofilm formation, public goods production, and gene horizontal transfer of bacteria. The phenomenon of quorum sensing is widespread in biological aggregates, such as activated sludge, biofilm and granular sludge. Learning and understanding the regulation behavior between quorum sensing and microorganisms plays an important role in wastewater treatment. Here, we reviewed the classification of the sensing signal molecule, regulation mechanism of quorum sensing, as well as the regulation behavior of quorum sensing in activated sludge, biofilm, aerobic granular sludge, and anaerobic granular sludge. The future researches of quorum sensing in wastewater treatment were discussed. This review could deepen the understanding of the regulation of quorum sensing in wastewater treatment.