Table of Content

15 March 2021, Volume 32 Issue 3

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Opinion of the Editor in Chief

Thinking on large-scale terrestrial ecosystem management and its theoretical fundament and practice

YU Gui-rui, YANG Meng, FU Chao, WANG Qiu-feng, CHEN Zhi

2021, 32(3):  771-787.  doi:10.13287/j.1001-9332.202103.040

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Ecosystem management at large scales is one of the core solutions to solve current global challenges of environmental and resources problem, mitigate climate change, govern ecosystems and environments regionally and achieve sustainable development. It is also a hotspot in the research and practice of conservation of global natural resources and ecosystems. Based on recalling and synthesizing of several large international actions on ecosystem management in the past two decades, this article rethought the concept of ecosystem management and its application from the perspective of discipline development of ecosystem management, theoretical fundaments and practices. The content included three parts: firstly, we reviewed the development of the scientific concept and practice of ecosystem management, discussed the connotations of the concept and redefined it, and summarized the practice of ecosystem management and its contribution to the development of the discipline. Secondly, we clarified the scientific and technological mission and basic tasks of ecosystem management, organized the discipline system of ecosystem management and its main research fields, summarized fundamental theories and the knowledge system of the science of ecosystem management, and clarified critical steps of ecosystem management actions, basic elements of management plans and management approaches. Finally, we proposed new trends of scientific research and the discipline development of ecosystem management, discussed the important spatial scales and its objects system of the scientific research on ecosystem management, proposed the cutting-edge scientific questions of global ecosystem management, integrative ecology thought and macro ecosystem approach. This review aimed at providing references for the scientific research and discipline deve-lopment of ecosystem management in China.

Original Articles

Spatiotemporal variations in leaf-out phenology of typical European tree species and their responses to climate change

LIN Shao-zhi, GE Quan-sheng, WANG Huan-jiong

2021, 32(3):  788-798.  doi:10.13287/j.1001-9332.202103.019

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Over the past decades, global warming significantly affected the spring phenology of plants. Many studies have reported the temporal and spatial patterns of spring phenological changes in China, but relatively less is known for that in Europe, which is also located in the temperate area of the Northern Hemisphere. To facilitate the regional comparison of phenological change and understand its response to climate change, we used the data of first leaf date (FLD) in Europe (1980-2014) and the corresponding meteorological data to examine the spatiotemporal variations in leaf-out phenology of four typical tree species (Aesculus hippocastanum, Betula pendula, Fagus sylvatica, and Quercus robur), and to identify the major climatic factors driving such variations. The results showed that the FLD of the four species in the study area advanced by 3.3-7.5 d·10 a^-1 during 1980-2014. The FLD was delayed at a rate of 2.03-3.19 d per degree of latitude from south to north, of 0.19-0.80 d per degree of longitude from west to East (except for Fagus sylvatica), of 2.25-3.44 d·100 m^-1 from low to high elevation. The advances in the FLD were mainly attributed to the increases of temperature in spring and the increases of precipitation in spring and winter. The rise of temperature in autumn and winter would delay FLD.

Spatial-temporal variations of carbon storage and carbon sequestration rate in China’s national forest parks

LI Wei, HUANG Mei, ZHANG Yuan-dong, GU Feng-xue, GONG He, GUO Rui, ZHONG Xiu-li, YAN Chang-rong

2021, 32(3):  799-809.  doi:10.13287/j.1001-9332.202103.015

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Forests play an important role in regulating climate change and maintaining carbon balance. To explore the carbon storage and carbon sequestration rate of national forest parks is of great significance for carbon sequestration capacity assessment and sustainable forest management. A process-based ecosystem model (CEVSA2 model) was used to simulate the spatial distribution of carbon density, carbon storage and carbon sequestration rate of 881 national forest parks in China during 1982-2017. The results showed that the average carbon density of national forest parks was 255.18 t C·hm^-2, being higher than the average carbon density of forest ecosystem in China. In 2017, the total carbon storage of national forest parks increased to 3.56 Pg C, accounting for 11.0%-12.2% of the total carbon storage in national forest ecosystems. During 1982-2017, the average carbon sequestration rate of national forest parks reached 0.45 t C·hm^-2·a^-1, and the carbon sequestration rate of all national forest parks was above 0.30 t C·hm^-2·a^-1. National forest parks in the northeast and southwest of China had the highest total carbon storage. The national forest parks in northeast of China had the highest soil organic carbon sequestration rate, while those in eastern China and central southern China had the highest biomass carbon sequestration rate. The area of national forest parks accounted for 5.8% of the total forest area of China, playing an important role in forest carbon sink management of China. Accurate assessment of the growth status, carbon sequestration potential and carbon absorption characteristics of national forest parks could provide reference for the comprehensive assessment of ecosystem service of forest parks in China.

Effects of natural and artificial restoration on plant community characteristics of alpine cutting blank in Western Sichuan, China

XU Qian, SHI Song-lin, JIA Long-yu, BAI Hai, CAO Ji-xin, WANG Guo-yan, PENG Pei-hao

2021, 32(3):  810-818.  doi:10.13287/j.1001-9332.202103.002

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To investigate the plant community characteristics of alpine cutting blanks under different restoration approaches, we conducted a field survey on cutting blanks experienced either natural restoration (40 years) or artificial restoration (30, 40 and 50 years) in western Sichuan, with natural forests as the reference. Our results showed that after 40 years natural succession, cutting blank was replaced by the secondary shrub of Spiraea alpina, while artificial restoration plantation was dominated by Picea likiangensis var. rubescens. The similarity indices between these communities and natural forests were low (0.19) and medium (0.28-0.49), respectively. Cutting blank through natural and artificial restoration had lower species diversity in the shrub layer but higher diversity in the herb layer than that of natural forests. With the increases of recovery time, total cross-sectional area at breast height, wood volume, index of species diameter class distribution, diversity indices, and similarity indices between plantations and natural forests gradually increased, while stand density gradually decreased. Compared with natural forests, plantations were facing with problems including high stand density, unreasonable structure, pure stands of cohorts and poor regeneration.

Relationship between climate and leaf carbon stable isotope of Hippophae

HE Ling-wei, YANG Jun-long, LI Xiao-wei

2021, 32(3):  819-824.  doi:10.13287/j.1001-9332.202103.007

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We analyzed the relationship between carbon stable isotope characteristics of 131 Hippophae populations and environmental factors by measuring the foliar δ¹³C value in Hippophae. The results showed that the foliar δ¹³C values of Hippophae ranged from -24.65‰ to -29.11‰, with an average of -26.97‰. Hippophae species were C3 plants. For the foliar δ¹³C values, the coefficient variation at intraspecific level was higher than that at interspecific level, indicating that environmental factors should be main factors driving the variations of leaf δ¹³C. The δ¹³C values had no significant correlation with latitude and longitude, but were negatively correlated with altitude. The regression equation was δ¹³C(‰)=0.118VAP-0.007GST-0.000028RDA-20.721 (R²=0.212,P<0.0001). Water vapor pressure (VAP), growing season temperature (GST), and radiation (RDA) were the major factors affecting foliar δ¹³C values. Our results could provide a theoretical basis to understand the responses of Hippophae species to global climate change.

Effects of aboveground and belowground litter inputs on the balance of soil new and old organic carbon under the typical forests in subtropical region

HONG Xiao-min, WEI Qiang, LI Meng-jiao, YU Tan-wei, YAN Qiang, HU Ya-lin

2021, 32(3):  825-835.  doi:10.13287/j.1001-9332.202103.008

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Litter is one of the most important factors controlling the accumulation, stabilization, and turnover of soil organic carbon (SOC) in forests. There is a knowledge gap of the impacts of aboveground and belowground litter inputs on the balance of new and old SOC under different forests in subtropical region. We examined the effects of aboveground and belowground litter inputs on SOC turnover using isotopic tracing technique, based on a 3-year C3 plants/C4 soil replacement experiment in natural forest (NF), Masson pine (Pinus massoniana) plantation (PM) and Chinese fir (Cunninghamia lanceolata) plantation (CL). Our results showed that forest types, litter treatments, and sampling time significantly affected SOC contents, δ¹³C, new and old SOC contents. Moreover, there were significant interactions between forest types and litter treatments. Litter input increased SOC content and net SOC increment, with higher sensitivity of NF than CL. Litter inputs decreased soil δ¹³C, with lower values in NF and PM compared to CL. For PM, the new SOC content in belowground litter treatment was significantly higher than that in aboveground litter treatment. The contents of old SOC were lower in belowground litter treatment than aboveground litter treatment in the NF and CL. Above- and below-ground biomass were positively correlated with SOC content and net increment. Belowground litter biomass were positively correlated with soil C/N ratio and new SOC content. Our results implied that belowground litter input had stronger effects on SOC turnover compared to aboveground litter input, with the effects varying among different forests. Our results provided new information on SOC accumulation and on sustainable management of the typical forests in subtropical region.

Estimating standing stocks of the typical conifer stands in Northeast China based on airborne lidar data

YUAN Yu-na, PENG Dao-li, WANG Wei, ZENG Wei-sheng

2021, 32(3):  836-844.  doi:10.13287/j.1001-9332.202103.001

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To promote the application of lidar technology in estimating standing stocks of the typical conifer stands in Northeast China, i.e., spruce-fir forest, larch forest, Korean pine forest, Pinus sylvestris var. mongolica forest, we combined the point cloud data obtained by airborne lidar with the data of 800 ground plots and established models of standing stocks for the four conifer stands by stepwise regression and partial least square. Partial least squares method was better than stepwise regression method (R²=0.05-0.15, RRMSE=2.6%-4.2%). Among the three types of feature variables involved in modeling, height variable (selected for 26 times) is more important than others (selected for 12 times and 11 times, respectively). With respect to the accuracy of models established based on the means of the partial least square, they worked best for Korean pine forest (R²=0.79, RMSE=60.92, RRMSE=22.9%) and larch forest (R²=0.76, RMSE=28.39, RRMSE=25.8%), followed by spruce-fir forest (R²=0.81, RMSE=46.96, RRMSE=27.7%) and P. sylvestris var. mongolica forest (R²=0.50, RMSE=55.49, RRMSE=30.4%). This study provi-ded an effective way to estimate standing stocks of four typical conifer stands in Northeast China.

Photosynthetically physiological mechanism of Stipa krylovii withered and yellow phenology response to precipitation under the background of warming

WANG Si-qi, ZHOU Guang-sheng, ZHOU Meng-zi, LYU Xiao-min, ZHOU Li, JI Yu-he

2021, 32(3):  845-852.  doi:10.13287/j.1001-9332.202103.003

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We examined the photosynthetically physiological mechanism of Stipa krylovii response to warming and precipitation changes, based on an experiment with the treatments of warming by infrared radiator and precipitation treatments by irrigation water. Under the warming background, precipi-tation was the main influencing factor of the withered and yellow phenology. Increasing precipitation postponed the occurrence time of both the beginning and the peak of the withered and yellow phenology, and prolonged the duration of the withered and yellow phenology. The effect of decreasing precipitation on prolonging the duration of the withered and yellow phenology was much stronger. Under the background of warming, the changes of precipitation markedly affected the physiological and ecological characteristics of the withered and yellow phenology, with the effect being the most significant at the beginning of the withered and yellow phenology. The net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (T_r), and the maximum ribulose 1,5-bisphosphate (RuBP) carboxylation rate (V_{c max}), RuBP regeneration capacity (J_max) were positively correlated with precipitation. Results of the pathway analysis showed that the photosynthetically physiological mechanism of withered and yellow phenology of S. krylovii would be different under different conditions of precipitation and temperature. Under the current environmental condition, J_max was the main influencing factor of the withered and yellow phenology, and V_{c max} was the main limiting factor. Under the scenarios of warm and dry climate and warm and wet climate, V_{c max} become the main influencing factor of the withered and yellow phenology. J_max would be the main limiting factor in the warm and dry climate conditions, and there would be no limiting factor in the warm and wet climate conditions. Our findings indicated that the withered and yellow phenological changes of S. krylovii depend on the photosynthetical capacity limitation resulted from meteorological conditions.

Physiological changes of Larix principis-rupprechtii seedlings inoculated with Trichoderma spp. under drought stress

SUN Yue-yan, WANG Xiu-li, GAO Run-mei, LI Jin

2021, 32(3):  853-859.  doi:10.13287/j.1001-9332.202103.004

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Tree regeneration is significantly affected by water deficiency, which could be alleviated by the inoculation of Trichoderma spp. In this study, the effects of rhizosphere inoculation with Trichoderma spp. on the antioxidant system and osmotic substances in the seedlings of Larix principis-rupprechtii was investigated under experimental drought stresses, with the relative water content 50%-60%, 35%-50%, and 20%-35% as the light, moderate and severe drought stress, respectively. The results showed that, with increasing drought stress, the activities of protective enzymes, SOD and POD in the needles of seedlings were significantly promoted, the contents of MDA and proline were remarkably increased, whereas the contents of soluble protein and starch showed a decreasing trend. Inoculation with Trichoderma spp. promoted much stronger increase in the activities of SOD and POD in the needles, yet the MDA content showed a lower level of increase. Under moderate drought, the activity of POD in the seedling inoculated with Trichoderma spp. was 1.8 folds of that in the control, while the content of MDA was 62.9% of the control. The contents of proline, soluble protein, soluble sugar, and starch in the inoculated seedlings were higher than that in the uninoculated seedlings. Drought-resistance of L. principis-rupprechtii seedlings inoculated by Trichoderma spp. was significantly enhanced due to the augmenting regulation of antioxidant system and osmotic adjustment substances. Therefore, under the trend of warming and drying in North China, the technique of rhizosphere inoculation of Trichoderma spp. could be popularized for forest plantation or understory tending.

Characteristics and environmental driving factors of water transformation in the Balaguer River watershed of Inner Mongolia steppe

FANG Li-jing, GAO Rui-zhong, JIA De-bin, YU Rui-hong, LIU Xin-yu, LIU Ting-xi, WANG Xi-xi

2021, 32(3):  860-868.  doi:10.13287/j.1001-9332.202103.24

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Inner Mongolian steppe is one of the ecological barriers in China. The variation of water resources is very important for the development of social-economy and the protection of eco-environment. We collected 254 water samples of precipitation, river, and shadow groundwater during wet-season and dry-season of 2018-2019 from Balaguer River watershed and meansured the physical-chemical indicators, δD and δ¹⁸O of water samples. The stable isotope technology, mathematical statistics, and the inverse distance weighting method were used to analyze the stable isotope composition, spatial-temporal variation, and impact factors. Moreover, the d-excess and the isotopic mixing ratio formula were used to analyze the conversion characteristics of different water and to identify their environment driving variables. The results showed that δD and δ¹⁸O of precipitation, river and shallow groundwater were higher in wet season than in dry season. The driving factors of different water transformation in the watershed were air temperature, altitude, and groundwater depth. Altitude was significantly negatively correlated with river δD, and the δD and δ¹⁸O of groundwater. δD and δ¹⁸O of groundwater fluctuated significantly in the area with groundwater depth less than 10 m, but were stable in other areas. There was a positive correlation between precipitation δ¹⁸O and air temperature. The d-excess in wet season was higher than that in dry season, with a decreasing distribution characteristic from southern to northern part in the study area. More than 50% river in upper stream came from precipitation, while more than half river water converted to groundwater, with different recharge-drainage relationships existed between surface water and groundwater in different river reaches.

The characteristics of soil fungal community in degraded alpine meadow in the Three Rivers Source Region, China

ZHAO Wen, YIN Ya-li, LI Shi-xiong, WANG Yu-qin, WANG Yan-long

2021, 32(3):  869-877.  doi:10.13287/j.1001-9332.202103.038

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To clarify the variation of species composition, diversity, and functional structure of soil fungi community along alpine meadow degradation,we examined the characteristics and controlling factors of soil fungal communities in non-degraded, lightly degraded, moderately degraded, severely degraded and extremely degraded (black soil beach) alpine meadows at the Three Rivers Source Region, based on the high-throughput gene sequencing and FUNGuild functional prediction. The results showed that the dominant phyla in alpine meadow soil were Ascomycota, Basidiomycetes, and Mortierellomycota. Species composition of soil fungal community varied greatly in alpine meadow under different levels of degradation. The abundance of Cladosporium flabelliforme, Entoloma sodale, Hygrocybe conica, Inocybe sp. and Trichocladium opacum increased, while that of Gibberella tricincta and Dactylonectria macrodidyma decreased following grassland degradation. The meadow under severe degradation had higher soil fungal Chao1 index, while that under light degradation had lower Shannon index and Simpson index. The abundance of pathologic, symbiotic, and saprophytic types of fungi varied among different alpine meadows. Along with the grassland degradation, the abundance of soil symbiotic fungi decreased, while that of pathological fungi increased. The soil fungal community and functional compositions changed obviously with degradation in the alpine meadow. Plant aboveground biomass, soil water content, pH, total organic carbon, total nitrogen, ammonium nitrogen, available phosphate, total potassium and AN/AP (ratio of available nitrogen and available phosphorus) were the main driving factors for the variations in soil fungal community structure.

Structure and function of soil bacterial communities in the monoculture and mixed plantation of Pinus massoniana and Castanopsis hystrix in southern subtropical China

LIANG Yan, MING An-gang, HE You-jun, LUO Ying-hua, TAN Ling, QIN Lin

2021, 32(3):  878-886.  doi:10.13287/j.1001-9332.202103.37

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Establishing monoculture of native broadleaved tree species and mixed coniferous broadleaved plantations is the tendency for forest management in subtropical China. The variations of structure and function of soil bacterial community in monoculture and mixed tree plantations are still not clear. We examined soil bacterial community structure and function under different soil layers (0-20, 20-40 and 40-60 cm) in three planted forests, including broadleaved Castanopsis hystrix, coniferous Pinus massoniana and their mixed plantation, in south subtropical China, using 16S rRNA gene high-throughput sequencing and PICRUSt prediction. The results showed that soil bacterial community structure of mixed plantation and P. massoniana plantation were similar but being significant different from that in C. hystrix plantation. The diversity, biological pathways metabolic function, and nitrogen cycling function of soil bacterial community in C. hystrix plantation were lower than those in P. massoniana plantation and mixed plantation. Soil total nitrogen, nitrate nitrogen and C/N were the main factors driving the variations of soil bacterial community structure and function among different forest types. Our results suggested that the mixed plantation of C. hystrix and P. massoniana is better than C. hystrix plantation in this area in terms of soil bacterial community structure and function.

Changes of soil bacterial community structure at the secondary successional stages in the Pinus yunnanensis forest

XU Fan-di, LI Shuai-feng, SU Jian-rong

2021, 32(3):  887-894.  doi:10.13287/j.1001-9332.202103.039

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Soil bacterial diversity is a key factor for the maintanence of forest ecosystem function. Soil bacterial community would change along forest succession. We analyzed the variations of soil bacterial diversity and community composition at different successional stages in the Pinus yunnanensis forest, which would help understand the mechanism underlying forest restoration. We investigated soil bacterial diversity, community composition, and effect factors at different successional stages (including coniferous forest, mixed coniferous and broadleaf forest, and evergreen broadleaf forest) using Illumina Hiseq platform. The results showed that OTUs, Chao1 index, Ace index, and Shannon index of soil bacterial community decreased with the process of secondary succession. The highest soil bacterial total OTUs, richness, and complexity appeared at early successional stage. Soil bacterial community composition varied across different stages, with the mixed coniferous and broadleaf forest showing largest variation. Proteobacteria and Acidobacteria were common dominant phyla at secondary successional stages. Actinobacteria, Chloroflexi, and Patescibacteria were dominant phyla at the early successional stage, the abundance of which decreased with successional process in the P. yunnanensis forest. Proteobacteria and WPS-2 increased with the succession. Soil pH and tree species richness were key factors in driving soil bacterial community structure. The soil bacterial diversity decreased with forest succession, while the variations of soil bacterial community composition became larger.

Effects of phosphorus fertilizer on root characteristics, uptake and utilization of phosphorus and yield of dryland wheat with contrasting yearly rainfall pattern

WANG Wen-xiang, SUN Min, LIN Wen, REN Ai-xia, XUE Jian-fu, YU Shao-bo, ZHANG Rong-rong, GAO Zhi-qiang

2021, 32(3):  895-905.  doi:10.13287/j.1001-9332.202103.006

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To understand the growth responses of dryland wheat to different application rates of phosphorus fertilizer in different rainfall years, we examined root characteristics, spike number, yield and phosphate utilization. Results would help improve phosphate fertilizer use in dryland wheat production. We carried out a field experiment at the research station of Shanxi Agricultural University from 2012 to 2016. We examined the effects of four application rates of phosphorus (0, 75, 150 and 225 kg·hm^-2 on root growth, phosphate utilization and yield formation of dryland wheat in different years with contrasting rainfall pattern. Compared with the treatment without phosphorus fertilization, phosphate application increased root surface area at all growth stages and root weight density in the 0-80 cm soil layer at jointing, anthesis, and maturity stages. Phosphate application significantly increased soil water consumption from jointing to anthesis, and total soil water consumption in the growing season. Phosphate application enhanced the amount of pre-anthesis phosphate translocation and phosphate accumulation of grain. Spike number, yield and water use efficiency were increased with 75, 150 and 225 kg P·hm^-2 by 9.2% to 22.5%, 11.8% to 30.0%, and 2.1% to 12.1%, respectively. In the dry years, the application rates of 150 and 225 kg P·hm^-2 in comparison to 75 kg P·hm^-2 significantly increased root weight density and root surface area at all stages, soil water consumption from sowing to jointing and from jointing to anthesis, and total water consumption in the growing season. In comparison to the rate of 75 kg P·hm^-2, 150 and 225 kg P·hm^-2 increased soil water consumption from sowing to jointing by 7.3-8.7 mm, soil water consumption from jointing to anthesis by 15.6-18.1 mm, and total water consumption by 15.6-18.1 mm. Significant increase in the pre-anthesis phosphate translocation and phosphate accumulation in grain was higher under 150 and 225 kg P·hm^-2 than that under 75 kg P·hm^-2 in dry years. Furthermore, the two rates (150 and 225 kg P·hm^-2) in dry years increased spike number by 9.3%-10.7% and yield by 11.9%-14.6%. The application rate of 150 kg P·hm^-2 significantly improved phosphorus use efficiency by 20%-82% in comparison to other rates. In normal years, the rates of 150 and 225 kg P·hm^-2 increased root surface area, root weight density at both anthesis and maturity compared with 75 kg P·hm^-2. Soil water consumption from anthesis to maturity and total soil water consumption in the growing season were also increased by 1.2-15.0 and 3.8-23.1 mm, respectively. In addition, phosphorus accumulation in post-anthesis and phosphate accumulation in grain were increased in both 150 and 225 kg P·hm^-2, which increased spike number by 1.4%-9.6% and yield by 3.5%-10.4%. The effects of phosphate application at the rate of 150 kg P·hm^-2 were significantly different from 75 and 225 kg P·hm^-2. In conclusion, phosphorus fertilizer application enhanced uptake of water and phosphate in dryland wheat at early and middle growth stages in dry years and at the late growth stage in normal years. Phosphorus application increased wheat yield mainly due to the increases of spike number. The application of 150 kg P·hm^-2 is the best choice for high water and phosphorus fertilizer use efficiency and high yield in both dry and normal years.

Effects of phosphorus application rates on spring rape yield and soil phosphorus balance

FU Rong, YUAN Jiu-dong, XU Ting-ting, XU Qian, ZHANG Yang, ZHANG Rong, TIAN Hui, GAO Ya-jun

2021, 32(3):  906-912.  doi:10.13287/j.1001-9332.202103.010

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Excessive application of phosphorus fertilizer leads to high soil available phosphorus content but low phosphorus use efficiency in the main production areas of spring rape in eastern Qinghai. Understanding the effects of phosphorous application rates on the growth, phosphorus absorption, soil phosphorus balance in the field of spring rape could improve nutrient management of spring rape, and benefit for the sustainable development of agriculture in Qinghai-Tibet Plateau. A field experiment was carried out in Huzhu County of Qinghai Province from 2017 to 2018. We mea-sured seed yield, phosphorus uptake and oil content of spring rape under five phosphorous fertilizer rates (0, 30, 60, 90 and 120 kg P₂O₅·hm^-2). In 2017, the seed yield and oil production of spring rape with the rate of 60 kg·hm^-2 were significantly higher than that of no phosphorus fertilizer treatment. In contrast, seed yield and oil production did not increase when the phosphorus rate exceeded 60 kg·hm^-2 in 2017. Phosphorus rate did not affect seed yield, phosphorus accumulation, and oil production of spring rape in 2018. The phosphorus use efficiency was low in both years, with a mean value of 6.7%. Phosphorus fertilizer application caused phosphorus surplus in soils, which was low when the application rate was less than 60 kg·hm^-2. Our results suggest that the rate of 60 kg·hm^-2 is suitable for spring rape production in the eastern Qinghai Province.

Evaluating the effects of different sowing dates and tillage methods on dry-land wheat grain dry matter accumulation based on the APSIM model

NIE Zhi-gang, LI Guang, WANG Jun, DONG Li-xia, LUO Cui-ping, MI Rong-juan

2021, 32(3):  913-920.  doi:10.13287/j.1001-9332.202103.022

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Accurate simulation of dry matter accumulation in wheat grains can provide important technical support for regulating wheat production in hilly areas of Loess Plateau. Using the APSIM model, we analyzed dryland wheat grain dry matter accumulation and distribution using the meteorological data from 1971 to 2017 in Anding District, and the field test data from 2016 to 2017 in Anjiagou Village, Fengxiang Town, Anding District, Dingxi City, Gansu Province. Furthermore, the influence of sowing date and tillage method on dry matter accumulation of wheat grain was quantitatively analyzed on the basis of model validation. The results showed that the root mean square error (RMSE) between the simulated and measured values of grain dry matter was 57.5-143.1 kg·hm^-2 and the normalized root mean square error (NRMSE) was 1.4%-9.9% under the three sowing dates and four tillage methods, respectively. The precision of the APSIM model was satisfactory. Under different sowing dates, the order for beneficial degree of tillage treatment to dry matter accumulation in wheat grains was no tillage with straw cover > conventional tillage with straw cover > no tillage > conventional tillage. The treatment of no tillage with straw covered was the most favora-ble to dry matter accumulation in wheat grains, with no significant difference between no tillage and conventional tillage treatments. Under different farming methods, early sowing was better than normal sowing and late sowing for the dry matter accumulation process of wheat. Late sowing had stronger impacts on dry matter accumulation, with the least ideal accumulation process.

Effects of long-term fertilizer management on soil labile organic carbon fractions and hydrolytic enzyme activity under a double-cropping rice system of southern China

SHI Li-hong, LI Chao, TANG Hai-ming, CHENG Kai-kai, LI Wei-yan, WEN Li, XIAO Xiao-ping

2021, 32(3):  921-930.  doi:10.13287/j.1001-9332.202103.023

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Fertilization is an effective way to improve soil quality, increase soil fertility and soil microbial diversity in paddy soil. To explore the changes of soil labile organic carbon (C) fractions and hydrolytic enzyme activity after 34 years fertilization treatments in a field experiment in double-cropping rice system of southern China. There were four treatments, including chemical fertilizer alone (MF), rice residue and chemical fertilizer (RF), 30% organic matter and 70% chemical fertilizer (OM), and the control without fertilizer input (CK). We measured soil organic carbon (SOC) content, soil labile organic C fractions, SOC related hydrolytic enzyme activity, correlation coefficients of soil enzyme activity with SOC content and its labile organic C fractions. The results showed that MF, RF and OM increased SOC content by 4.5%, 22.4% and 53.5%, respectively. Compared with MF and CK, RF and OM increased soil labile organic C fractions [cumulative C mineralization (Cmin), permanganate oxidizable C (KMnO₄-C), particulate organic C (POC), dissolved organic C (DOC), light fraction organic C (LFOC), microbial biomass C (MBC)] and the proportion of each labile organic C fractions to total organic C. The contents of Cmin, KMnO₄-C, POC, DOC, LFOC and MBC under OM treatment were 3.5, 3.1, 3.7, 1.9, 1.2 and 1.9 times higher than CK treatment, respectively. The proportion of labile organic C fractions to total organic C of RF and OM treatments was significantly higher than that in CK. The order of soil hydrolytic enzyme activity [α-glucosidase (αG), β-glucosidase (βG), β-xylosidase (βX), cellobiohydrolase (GBH), and N-acetyl-β-glucosaminidase (NAG)] was OM>RF>MF>CK. The soil hydrolytic enzyme activity under OM treatment increased by 111.8%, 14.1%, 127.3%, 285.6% and 91.4% compared with CK, respectively. Furthermore, RF and OM treatments were beneficial to soil peroxidase (POD) activity. MF treatment was beneficial to soil polyphenol oxidase (PPO) activity. There was a significant positive correlation between soil hydrolytic enzyme activity and SOC content and its labile organic C fractions. In conclusion, the combined application of organic manure, rice straw returning and chemical fertilizer is an effective method to improve soil labile organic C fractions and hydrolytic enzyme activity in a double-cropping rice paddy field of southern China.

Effects of basic application of chlorocholine chloride combined with nitrogen fertilizer on nitrogen use of summer maize in North China Plain

MA Zheng-bo, DONG Xue-rui, FANG Meng-ying, WANG Qi, YAN Peng, WANG Qing-yan, LU Lin, DONG Zhi-qiang

2021, 32(3):  931-941.  doi:10.13287/j.1001-9332.202103.021

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To clarify the effects of combined applications of chlorocholine chloride (CCC) and nitrogen fertilizer (CN) on nitrogen metabolism and nitrogen use efficiency of summer maize, we conducted a field experiment in Xinxiang experimental station of Chinese Academy of Agricultural Sciences in 2018 and 2019, with four nitrogen application rates (0, 62.5, 125 and 187.5 kg·hm^-2), and two maize varieties of Jingnongke 728 (JNK728) and Zhongdan 909 (ZD909). The results showed that across the two years CN-CCC increased maize yield by 7.7% and 5.0% under the nitrogen application rates of 62.5 kg·hm^-2 and 125 kg·hm^-2, respectively. CN-CCC increased the contents of nitrate reductase, glutamine synthetase, glutamate synthetase and soluble protein, and finally promoted nitrogen metabolism. Under the low and middle nitrogen application conditions (62.5 kg·hm^-2 and 125 kg·hm^-2), plant nitrogen content of JNK728 and ZD909 increased by 17.6% and 30.3%, grain nitrogen content increased by 10.3% and 17.4%, nitrogen partial productivity, agronomic efficiency of applied nitrogen, recovery efficiency of applied nitrogen, nitrogen use efficiency increased by 10.0%, 15.7%, 23.3%, 24.8% and 5.7%, 15.0%, 49.9%, 71.7%, respectively. In conclusion, appropriate basic application of CN-CCC could enhance nitrogen metabolism, increase nitrogen use efficiency and grain yield of summer maize. Our results showed that CCC combined basic nitrogen application of 125 kg·hm^-2 had the best effect.

Effects of long-term fertilization without phosphorus on greenhouse gas emissions from paddy fields

HE Zhu, XU Chen, ZHOU Bei-bei, XUE Li-hong, WANG Yu, SHEN Ming-xing, YANG Lin-zhang

2021, 32(3):  942-950.  doi:10.13287/j.1001-9332.202103.028

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The strategy of few or no-phosphorus fertilization in rice season but more in wheat season can effectively increase phosphorus use efficiency and reduce phosphorus loss through runoff and leaching. It remains unknown whether the lack of phosphorus will affect greenhouse gas emission in the rice season. We monitored the CH₄ and N₂O emission fluxes during the growth period of rice treated with normal phosphorus application (NPK) and no-phosphorus application (NK) in two long-term experimental fields in Suzhou and Yixing. The results showed that long-term no-phosphorus application promoted CH₄ and N₂O emission in both fields. Compared with the NPK treatment, CH₄ and N₂O emissions from the NK treatment significantly increased by 57% and 25% in Suzhou experi-mental field, respectively, while those in Yixing experimental field were also significantly increased by 221% and 70%, respectively. The contents of organic acid, dissolved organic carbon and available phosphorus in soil were reduced under long-term NK treatment, and they were closely related to CH₄ emission. Soil available phosphorus content was significantly negatively correlated with CH₄ emission (r=-0.987). The global warming potential (GWP) was greater in NK treatment than NPK treatment in both fields. Therefore, long-term no-phosphorus application could decrease the contents of organic acid, soluble organic carbon, and available phosphorus in soils, resulting in more CH₄ and N₂O emission in rice field.

Regulating effect of spraying stage of ethephon on the formation of source-sink in peanut

GAO Fang, LI Yue-rong, ZHANG Qiong, LIU Zhao-xin, ZHAO Ji-hao, YANG Dong-qing, LI Xiang-dong

2021, 32(3):  951-958.  doi:10.13287/j.1001-9332.202103.029

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To solve the problem of uncoordinated source-sink relationship that limits the increase of peanut yield, we investigated the regulating effects of ethephon on the formation of source-sink in cultivar Shanhua 9 by spraying at 10, 20, and 30 d after anthesis in a field experiment. The results showed that spraying ethephon at 10 d and 20 d after anthesis significantly reduced the number of flowers, pegs and young pods, but increased the number of immature pods and mature pods. Spraying at 30 d after anthesis did not affect the number of flowers, pegs and young pods. Spraying ethephon could improve the leaf area per plant. Spraying at 10 d after anthesis achieved the highest leaf area per plant and the increment amplitude decreased with the delay of spraying stage. Spraying ethephon at 10 d and 20 d after anthesis significantly improved the photosynthetic performance of peanut, whereas spraying at 30 days after anthesis increased the photosynthesis only in the short-term and had no effect at late growth period. In terms of the comprehensive characters of source and sink, spraying ethephon at 20 d after anthesis achieved the most harmonious source-sink relationship, which could promote the transport of photosynthate to pods and increase the economic pods ratio, pod fullness, and the yield. Therefore, spraying ethephon is an effective practice to solve the problems of “more flowers but less pegs” and “more pods but less kernels” in peanut. The optimum spraying stage of ethephon to regulate flowering should be at 20 d after anthesis.

Estimation of SPAD value in waterlogged winter wheat based on characteristic indices of hyperspectral and digital image

GAO Xiao-mei, LI Yan-li, LU Bi-lin, XIONG Qin-xue, WU Qi-xia, LI Ji-fu

2021, 32(3):  959-966.  doi:10.13287/j.1001-9332.202103.009

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To explore the optimal monitoring method for soil and plant analyzer development (SPAD) of winter wheat under waterlogging stress based on hyperspectral and digital image techno-logy, the correlations between SPAD of the waterlogged winter wheat and fifteen indices of hyperspectral characteristic and fourteen indices of digital image feature were analyzed under a micro-plot which could be irrigated and drainage separately. Then, the BP neural network models for SPAD estimation were constructed based on the optimal monitoring feature indices. Compared with the normal winter wheat, SPAD and the value of hyperspectral reflectance did not change under short-term waterlogging (less than 7 d), whereas the SPAD was significantly decreased after more than 12 d waterlogging treatment with the value being close to zero at the late stage of growth. The estimation accuracy based on the digital image characteristics of green minus red, excess red index, norma-lized redness index and excess green index showed similar results compared to that using the BP network model based on the characteristics of the corresponding hyperspectral band. The highest R² between the measured value and the predicted value was 0.86, while the root mean square error (RMSE) was 3.98. Compared with the BP network models built with the digital image feathers, the accuracy of the models based on the four hyperspectral characteristic indices (carotenoid reflex index, yellow edge amplitude, normalized difference vegetation index and structure insensitive pigment index) for SPAD was significantly improved, with the highest R² of 0.97 and the lowest RMSE of 1.95. Our results suggest that both hyperspectral and digital image technology could be used to estimate SPAD value of waterlogged winter wheat and that the BP network model based on hyperspectral characteristic indices performed better in the estimation accuracy.

Effects of water-nitrogen coupling on photosynthetic characteristics, yield, water and nitrogen use efficiency for mountain apple trees under surge-root irrigation in Northern Shaanxi area of China

LI Zhong-jie, FEI Liang-jun, HAO Kun, LIU Teng, ZHANG Quan-ju, CHEN Nan-shu, LIU Li-hua, ZHONG Yun

2021, 32(3):  967-975.  doi:10.13287/j.1001-9332.202103.027

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Taking 7-year-old apple trees (Hanfu) as the test material, an experiment with three irrigation levels including high water (W₁, 85%-100%θ_f, θ_f was the field water holding capacity), medium water (W₂, 70%-85%θ_f) and low water (W₃, 55%-70%θ_f), and three nitrogen application levels, high (N₁, 600 kg·hm^-2), medium (N₂, 400 kg·hm^-2) and low (N₃, 200 kg·hm^-2), was conducted to investigate the effects of water and nitrogen coupling on photosynthetic characteristics, yield and water and nitrogen utilization of apple trees in mountainous areas under surge-root irrigation (SRI). The results showed that the net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), leaf instantaneous water use efficiency (WUE_i) of apple trees leaves decreased with decreasing nitrogen application rates under the same irrigation amount, but C_i increased. Under the same nitrogen application rate, foliar P_n, T_r, g_s and WUE_i decreased with decreasing irrigation amount, but C_i increased. The daily average values of P_n and T_r under W₁N₁ treatment were the largest, while W₂N₂ treatment had the largest WUE_i. Apple yield, irrigation water use efficiency (IWUE) and nitrogen partial productivity (NPFP) were significantly affected by irrigation and nitrogen application. The W₂N₂ treatment had the highest yield (26761 kg·hm^-2). IWUE increased significantly with the decreasing irrigation and the increasing nitrogen application, while NPFP increased significantly with the increases of irrigation and the decreases of nitrogen application. Results of the regression analysis showed that the combination of irrigation and nitrogen application was closest to W₂N₂ treatment when yield and IWUE got the optimal solution. Therefore, W₂N₂ treatment was the best combination mode of water and nitrogen application for apple under SRI in Northern Shaanxi mountain area.

Status and causes of soil compaction at apple orchards in the Weibei Dry Highland, Northwest China

WEI Bin-meng, LI Zhong-hui, WANG Yi-quan

2021, 32(3):  976-982.  doi:10.13287/j.1001-9332.202103.025

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To find out the recessive factors of soil degradation threatening the healthy development of Weibei apple orchards, we examined soil compaction status and its inducing factors. This study could provide a theoretical basis for apple orchard scientific management. We evalua-ted the changes of soil bulk density and compaction with the depth of soil layer in 0-60 cm in four apple orchards with various planting period, including <10 years (4-6 years), 10-20 years (14-16 years) and ＞20 years (24-26 years). The location and degradation degree of soil compaction in orchard were investigated. Through analyzing the number of soil aggregates and the stability, soil clay and organic matter contents, we tried to find the reasons for the internal compacting of soil in Weibei orchards. The results showed that soil bulk density and compactness in the 0-60 cm soil layer significantly increased with increasing planting years and soil depth. With the 20 cm soil layer as a boundary, soil of Weibei orchards in different planting years showed obvious variation characteristics of loose in upper and compact in lower. The above indicators in soil layer above 20 cm basically met the normal requirements of apple trees, whereas soil layer below 20 cm exceeded the threshold for healthy growth of apple trees. The main reasons for soil compaction below the subsurface layer were poor soil aggregation, the lack of soil organic matter, less human disturbance during fruit planting, and the movement of scattered clay particles to the lower layer. With increasing years of fruit planting, soil compaction became more severe.

Evolution and spatial heterogeneity patterns of ecological efficiency of resource recycling in China

TANG Yan, MENG Fan-yue

2021, 32(3):  983-992.  doi:10.13287/j.1001-9332.202103.014

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Analyzing the evolution and heterogeneity patterns of resources’ ecological efficiency in China could provide reference for balancing regional development and improving the ecological efficiency of resource recycling. With the panel data of resource recycling in 26 provinces (cities, regions), we measured the ecological efficiency during 2004 to 2017 by the super efficiency DEA model, and analyzed the evolution of ecological efficiency and heterogeneity patterns based on the regionalization. The results showed that, from 2004 to 2017, the ecological efficiency of resource recycling was increasing yearly, with a mean annual growth potential of 1.5%, showing an spatially increasing trend from inland to coast. The ecological efficiency in China showed significant spatial correlation, with clustering character among provinces. During 2004 to 2017, the overall correlation decreased yearly due to the strong radiation effect of high level provinces. Because of the decrease of differentiation in the north, northeast, east, central, south, southwest and northwest in China, the spatial heterogeneity of ecological efficiency of resource recycling in China turned to relieve, which was weakened by the increasing heterogeneity in the southwest region.

Coupling coordination and interaction between urbanization and eco-environment in Cheng-Yu urban agglomeration, China

YANG Liang-jie, ZHANG Xiao-hong, PAN Jing-hu, YANG Yong-chun

2021, 32(3):  993-1004.  doi:10.13287/j.1001-9332.202103.012

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We built a comprehensive evaluation index system of urbanization in Chengdu-Chongqing (Cheng-Yu) urban agglomeration from four subsystems, including the economic, social, ecological, and urban and rural coordination. The comprehensive evaluation index system of eco-environment was constructed by combining ecological environment carrying capacity and ecological flexibi-lity. The coupling coordination degree model was applied to quantify the coupling coordination degree between urbanization and eco-environment in the prefecture-level cities of Cheng-Yu urban agglo-meration from 2005 to 2018. With GIS spatial analysis, phenomenon analysis and Tapio model, we analyzed the interaction type, evolution path and path of decoupling between urbanization and eco-environment in the prefecture-level cities of Cheng-Yu urban agglomeration. The results showed that the urbanization quality of Cheng-Yu urban agglomeration showed a trend of fluctuation and rise during the study period. Both Chengdu and Chongqing as high value areas showed “double-core” radia-ting to the surrounding areas. The eco-environment quality showed a slowly rising trend. The spatial pattern was a “ U ” shape with a north opening, high perimeter and low center. The degree of coupling coordination between the urbanization system and the eco-environment system was rising, with a spatial pattern of low in the middle and high in the east and west. The overall level of coupling coordination was relatively high. The type of coupling coordination degree was gradually evolving from near-disorder and reluctant coordination to moderate coordination. The evolution paths of urbanization and eco-environmental interaction were divided into two categories: stable and changing. The stable type included 20 cities in 5 subcategories, with Chengdu, Deyang, Mianyang, etc. being always well-coordination. The change type included 16 cities in 9 subcategories. The coordination degree of Chongqing main urban area, Tongliang and most other cities was improved, showing “rising” development. Hechuan, Zigong and a few other cities showed “sinking” development. The growth rates of both ecological environment and urbanization were positive. The decoupling state of urbanization and ecological environment was mainly characterized by weak decoupling and expansion connection.

Temporal-spatial variation and the affecting factors of protected areas in Guizhou, China

FAN Han, YANG Zhao-hui, WANG Cheng, BI Xing, ZHANG Ming-ming

2021, 32(3):  1005-1014.  doi:10.13287/j.1001-9332.202103.016

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The establishment of protected areas is the bottom line of ecological security for promoting the construction of ecological civilization and supporting economic and social development, which is an important strategy to realize sustainable development and maintain ecological security. In order to reveal the large spatial process of protected areas and its influencing factors, we used the methods of nearest neighbor index, kernel density, and standard deviational ellipse to analyze the temporal-spatial variation characteristics of the protected areas in Guizhou Province from 2002 to 2017, as well as the influencing factors combined with geo-detectors. The results showed that, during the study period, the number, area, and types of protected areas in Guizhou Province showed a diversified and rapid development, forming a protected area system with nature reserves, forest parks and scenic spots as the main body and wetland parks, geoparks and natural heritage sites as the supplement. The spatial cohesion of protected areas was strengthened, the scope of spatial distribution was expanding, and the speed of spatial movement was declining, forming a spatial pattern dominated by the northeast-southwest direction and gradually stable. The coalescence process in protected areas was strongly influenced by topography and vegetation distribution. The protected areas tended to cluster in gentle terrain around rivers and mountains and in areas of concentrated vegetation. The spatial differentiation of protected areas was jointly affected by multiple factors at different levels. The explanatory power of different factors to the spatial differentiation of protected areas was different. Among them, the normalized difference vegetation index, areas of forest and highway mileage were the common main factors affecting the spatial differentiation of the number and area of protected areas, and the explanatory power of different factors was significantly consolidated after interaction, characterized as nonlinear or bi-factor enhancement.

Effects of the distribution of biological soil crust on the hydrodynamic characteristics of surface runoff

JI Jing-yi, ZHAO Yun-ge, YANG Kai, ZHANG Wan-tao, GAO Li-qian, MING Jiao, WANG Shan-shan

2021, 32(3):  1015-1022.  doi:10.13287/j.1001-9332.202103.017

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The distribution pattern of biological soil crusts (biocrusts) is one of the main factors affecting runoff and sediment yield. The relationship between runoff and sediment yield and biocrusts’ distribution pattern is not clear, which hinders understanding the mechanism underlying the effects of biocrusts on runoff and sediment from slopes. To fill the knowledge gap, we investigated the relationship between the landscape indices of three biocrusts’ distribution patterns, i.e. zonation, chessboard and random, and the hydraulic parameters, using of simulated rainfall experiments and landscape ecology methods. The results showed that biocrust significantly affected the erosion force of slopes and that its distribution pattern could affect slope erosion dynamics. Compared to bare soil, the presence of biocrusts significantly reduced the runoff velocity (54.6%) and Froude number (67.0%), increased the runoff depth (86.2%) and Darcy-Weisbach resistance coefficient (10.68 times), but did not affect the Reynolds number and runoff power. Expect for the runoff depth, there were significant differences in the hydraulic parameters of the three biocrusts’ distribution patterns, with the random pattern having the strongest impacts on the dynamics of slope erosion. Based on factor analysis and cluster analysis, five indices of percentage of patch to landscape area, patch density, landscape shape index, patch cohesion and splitting could be used as the indicators for the distribution characteristics of biocrust patches. The patch cohesion and splitting of biocrust patches were the main distribution pattern indices of the hydrodynamics of surface runoff. As the patches patch cohesion decreased, the splitting increased, which caused the surface runoff velocity increase, the resistance decrease, and the slope erosion became more severe.

Estimation of soil Na⁺ content based on measured hyperspectral and Sentinel-2B data in northern Ningxia, China

SHANG Tian-hao, CHEN Rui-hua, ZHANG Jun-hua, SUN Yuan, JIA Ping-ping

2021, 32(3):  1023-1032.  doi:10.13287/j.1001-9332.202103.018

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To explore the ability of different sensors to estimate soil Na⁺ content, we got the mea-sured soil spectra and Sentinel-2B image spectra of the typical soil samples from the northern area of Ningxia. We filtered the sensitive parameters from the spectra data by means of stepwise regression (SR) and principal component regression analysis (PCA). We established the models to estimate soil Na⁺ content based on the measured spectra and image data using partial least square regression (PLSR), support vector machine (SVM) and back propagation neural network model (BPNN). The results showed that, except for Band9, there was significant correlation between the resampling data and the image data. The estimation accuracy of models based on SR-screening was generally higher than the PCA (excluding SVM model). The PCA-SVM model was the best image estimation model for soil Na⁺ content, with a prediction accuracy of 0.792. The SR-BPNN model was the best measured estimation model, with a prediction accuracy of 0.908. The estimating accuracy of the SR-PLSR image-spectra-based model increased from 0.481 to 0.798 after calibrated by the resampled measured spectrum model, which effectively enhanced the accuracy in estimating the soil Na⁺ content at large scale. We successfully made the spatial transformation of soil Na⁺ content from point to surface. Our results provided a scientific reference for Sentinel-2B image to monitor Na⁺ content in salinized soil.

Vegetation coverage change of the demonstration area of ecologically friendly development in the Yangtze River Delta, China based on GEE and BRT during 1984-2019

LIU Yao-yi, ZENG Peng, ZHANG Ran, SUN Feng-yun, CHE Yue

2021, 32(3):  1033-1044.  doi:10.13287/j.1001-9332.202103.011

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The demonstration area of ecologically friendly development in the Yangtze River Delta is a major national strategy area, and thus eco-environmental protection should be a priority for the sustainable development. Exploring the spatial-temporal variations of franctional vegetation coverage (FVC) is conducive to accurate assessing the ecological quality of environment, which is of great significance to regional sustainable development. In this study, the characteristics and trends of spatial-temporal variation of vegetation cover during 1984-2019 in the demonstration area were analyzed based on Google Earth Engine (GEE). The effects of different ecological factors on FVC were quantified by the boosted regression tree (BRT). Results showed that,the changing trend of FVC in the study area shifted from decreasing to increasing trend from 1984 to 2019. The spatial distribution of FVC in the study area varied with both stages and regions. FVC was mainly degraded. Compared with the year 1984, the area of vegetation degradation and improvement in 2019 accounted for 49.8% and 12.8%, respectively. The vegetation degradation mainly occurred in the north of Wujiang, south of Jiashan, and northeast of Qingpu. Human activities severely weakened the influence of natural factors on FVC. Our findings suggested that the GEE is an effective tool for monitoring the dynamics of vegetation coverage.

Ecosystem service pattern of Fuzhou City based on ecosystem service bundles

SONG Jia-peng, CHEN Song-lin

2021, 32(3):  1045-1053.  doi:10.13287/j.1001-9332.202103.013

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Based on InVEST model, recreational opportunity spectrum, factor analysis, cold and hot spot analysis, SOFM neural network, relief degree of land surface (RDLS) methods, we evalua-ted six kinds of ecosystem service in Fuzhou City and analyzed the trade-offs and synergies among them, with the aim to clarify the dominant services and the spatial pattern of service bundles in different topographical regions. The results showed substantial spatial heterogeneity in different ecosystem services of Fuzhou City. Water yield, carbon sequestration, habitat quality, and recreational opportunities were totally high, whereas the supply of agricultural products and soil and water conservation were low and substantial differences. The interaction between water yield and cultural servi-ces were synergies, but trade-offs occurred among regulating service, supporting service and agricultural products service. There were spatial aggregations for both trade-offs and synergies. Ecosystem service bundles could be divided into suburban recreation bundle, water conservation bundle, agricultural products bundle, urban life bundle, and forest ecological conservation bundle. The composition of service bundles clusters was different under different RDLS, with obvious spatial heterogeneity.

Amphibian habitat network planning based on the graph theory: A case study of Pelophylax nigromaculata

ZHANG Li, HE Ling, YAN Feng, CHEN Ya-heng

2021, 32(3):  1054-1060.  doi:10.13287/j.1001-9332.202103.020

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Both biodiversity conservation and the construction of biological habitat networks are key components of territorial spatial planning in China. Improving the landscape functional connectivity of biological habitat networks plays a vital role in biodiversity conservation. Although biological habitat network planning is a hot topic in literature, there is still lack of operable technological and methodological support in practical planning. According to the graph theory, the following three different aspects of biodiversity conservation and ecological network construction should be addressed in territorial spatial planning. First, the importance of biological habitat patches should be evaluated to determine the priority of patch protection. Second, the best locations for adding new elements should be identified to increase landscape functional connectivity of biological habitat network. Third, the impacts of construction projects should be judged and the potential impact of new construction projects according to the reduction of landscape function connectivity should be evaluated. We applied such framework to the network planning of amphibian (Pelophylax nigromaculata) habitat in Xiong’an New Area. The results showed that graph theory approach effectively met the requirements of those three aspects. The identification of the five optimal locations of new habitats of P. nigromaculata improved the overall landscape functional connectivity of habitat network by 19%. Four optimal locations of cross passage were identified to reduce the impacts of G45 expressway by assessing its impacts on functional connectivity of the amphibian habitat network.

Habitat hierarchies distribution of Sargassum muticum in Lidao bay, Shandong, China based on habitat suitability index model

LIU Wei, XIN Mei-li, ZHOU Jian, ZHAN Dong-mei, DING Gang, WU Hai-yi

2021, 32(3):  1061-1068.  doi:10.13287/j.1001-9332.202103.034

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We used the habitat suitability index (HSI) model to determine the habitat suitability of Sargassum muticum in Lidao bay, Shandong Province. Eight environmental factors, including temperature, salinity, depth, turbidity, sediment, inorganic nitrogen concentration, phosphate concentration, distance from seaweed bed, were used as input variables for HSI model. The weight of each factor was defined by the analytic hierarchy process (AHP). We implemented the distribution of S. muticum suitable habitat along the coast of Lidao bay with the HSI model, based on the investigation of the environmental factors in spring and autumn 2018. The results showed that most of the S. muticum natural habitats were identified as excellent habitat and suitable habitat, accounting for 14.2% in spring and 18.6% in autumn. The distribution of habitat hierarchies varied across seasons, while habitat hierarchies showed spatial intersections in different seasons. There were significant seasonal differences in the factor suitability indices of temperature and phosphate concentration, which accounted for the seasonal HSI variations of S. muticum in Lidao bay. The S. muticum HSI model could be used to detect the habitat hierarchies distribution of S. muticum, and also to find its potential suitable habitat, which could provide a reference for future resource conservation and artificial proliferation of S. muticum.

Spatio-temporal niche of major fish species in Pishan waters off Zhejiang Province, China

LIU Kun, YU Cun-gen, XU Yong-jiu, JIANG Xin-qin, ZHENG Ji, YU Nan-jing, ZHANG Pei-yi, JIANG Qiao-li, NIU Wei-zhen, WANG Hui-jun

2021, 32(3):  1069-1079.  doi:10.13287/j.1001-9332.202103.033

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Based on seasonal bottom trawl surveys in November 2015 (autumn), February (winter), May (spring) and August (summer) in 2016, the index of relative importance (IRI), Shannon index and Pianka index were used to analyze the breadth and overlap of spatio-temporal niche of major fish species in the Pishan waters off Zhejiang Province. Redundancy analysis and interspecific competition coefficient were used to examine the competition relationship and niche differentiation of those major fish species. The results showed that a total of 61 fish species were recorded throughout the year, which belonged to 13 orders, 29 families and 48 genera. A total of 19 species with IRI>100 were identified as major fish species. The temporal niche overlap value between Chelidonichthys kumu and Atule kalla was largest, indicating high temporal synchronization. Both the spatial niche overlap value and the spatio-temporal niche overlap value between Trpauchen vagina and Cynoglossus interruptus were largest, indicating that their spatial homology was high and that the use of spatial and temporal two-dimensional resource of both species were consistent. The percentage of species pairs with spatio-temporal niche overlap at the significant level (Q_ik>0.6) was only 5.8% in Pishan waters, indicating that the spatial and temporal distribution of those species were quite different. The overlap of spatio-temporal niche significantly varied across different seasons. The results of the interspecific competition coefficient were basically consistent with the niche overlap. Results of the redundancy analysis revealed the relationships between major fish species and environmental factors (temperature, salinity, dissolved oxygen), and further explained the niche diffe-rentiation among species.

Understanding the feeding ecology of Cynoglossus joyneri in Haizhou Bay based on stable isotope analysis

CHEN Wan, REN Xiao-ming, XU Bin-duo, ZHANG Chong-liang, REN Yi-ping, XUE Ying

2021, 32(3):  1080-1086.  doi:10.13287/j.1001-9332.202103.036

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We analyzed the feeding ecology of Cynoglossus joyneri by carbon and nitrogen stable isotope analysis based on the samples collected from the bottom trawl surveys during spring and autumn of 2018 in Haizhou Bay, China. The results showed that the δ¹³C and δ¹⁵N values of C. joyneri ranged from -20.75‰ to -15.91‰ and from 5.98‰ to 12.02‰, respectively. The mean values of the δ¹³C and δ¹⁵N were (-17.79±1.00)‰ and (9.37±1.33)‰, respectively. There was a significantly negative correlation between the δ¹³C values and standard length and a positive correlation between the δ¹⁵N values and standard length. The mean trophic level of C. joyneri was (3.43±0.97). There was a significantly positive correlation between the trophic level and standard length. The dominant prey groups of C. joyneri were fish, crabs, shrimps, mollusca, polychaeta, plankton and particle organic matter (POM). The trophic contribution of shrimps was the highest among these prey groups. The trophic contribution of fish, crabs and shrimps was higher in autumn than those in spring. This study would help to understand the role of C. joyneri in the material cycling and energy flow in Haizhou Bay ecosystem, and provide scientific basis for the protection and rational utilization of this species.

Trophic niche and gut microbiota of Dosidicus gigas in the eastern equatorial Pacific Ocean

GAO Xiao-di, GONG Yi, CHEN Xin-jun, LI Yun-kai

2021, 32(3):  1087-1095.  doi:10.13287/j.1001-9332.202103.035

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Understanding the adaptation of important marine species to environmental changes is critical for evaluating the effects of fisheries and climate change on marine services. The jumbo squid, Dosidicus gigas, is a keystone species in the eastern Pacific, which plays an intermediate role in the marine food web. Better understanding of their responses to climate change would be a big step to understand their population dynamics. In this study, stable isotope and high-throughput 16S rRNA sequencing were used to compare the variation of trophic niche, gut length, and gut microbiota of D. gigas in the eastern equatorial water during normal and El Niño periods. The results showed a significant variation in δ¹³C values for D. gigas in different periods, indicating differences in their food sources. The main phylum-level gut microbiome included Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Proteobacteria, and Tenericutes. There was no significant difference in the gut microbial composition during normal and El Niño periods, but differences in gut microbial diversity and relative abundance of some phyla bacteria. El Niño events could decrease the trophic niche breadth of D. gigas, and positively impact gut length and gut microbial diversity and richness. Firmicutes, Bacteroidetes, Spirochaetes, WPS-2, and Kiritimatiellaeota had a significant increase in the gut microbiota of D. gigas combined with a more concentrated intraspecific rank of distance during El Niño, suggesting that the changes of habitat and food sources caused by El Niño events could limit the distribution range of D. gigas. D. gigas might change their digestive system to improve the digestive and absorption capacity and enhance their immunocompetence. Such a climate-driven alteration might help D. gigas rapidly adapt to the changes of environmental conditions and food resources under El Niño.

Regulating effects of silicon on Cd-accumulation and stress-resistant responding in rice seedling

PAN Bo-gui, MO Han-qian, WANG Wei, CAI Kun-zheng, TIAN Ji-hui, CAI Yi-xia

2021, 32(3):  1096-1104.  doi:10.13287/j.1001-9332.202103.005

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Silicon (Si) application could significantly alleviate the toxic effects of cadmium (Cd) on the growth and development of rice. Here, we examined the regulatory effects of Si on Cd accumulation and stress response in rice seedlings through a hydroponic root separation test. The results showed that the biomass of rice seedlings decreased significantly under Cd stress, while the addition of Si could alleviate such negative effect. The uptake, transfer, and accumulation of Cd in rice seedling were significantly affected by Si addition under Cd stress. Si application under the unilateral Cd stress (Si-Cd+Si, Si-Cd) increased Cd-retention coefficient of root by 83.3%-83.6%, which restricted the transfer of Cd from root to aboveground. However, the treatment with Si added to the non-stressed side (Si-Cd) elevated the uptake and accumulation of Cd in rice seedling, with the accumulation in root being increased by 48.2% when compared to the treatment under the unilateral Cd stress without the addition of Si (CK-Cd). The treatment with Si added in two sides (Si-Cd+Si) decreased the uptake of Cd both in root and aboveground parts by 36.7% and 54.9%, respectively. The addition of Si under bilateral Cd stress (Cd-Cd+Si) significantly reduced the Cd uptake of both the root and aboveground parts by 57.8% and 46.5%, respectively, compared to the treatment of bilateral Cd stress (Cd-Cd). Higher Si concentration in rice seedling was found under the Cd stress. More Si was accumulated in rice seedling to resist the Cd stress when Si was added. The addition of Si affected the absorption of other metal elements in rice seedlings, including calcium (Ca), magnesium (Mg) and manganese (Mn). The concentrations of Ca and Mg in root and aboveground parts were significantly increased by Si addition under bilateral Cd-stress (Cd-Cd+Si), but Mn concentration was changed with the stress degree of Cd. The activities of superoxide dismutase (SOD) and peroxidase (POD) in root were affected by Si under Cd stress, especially for the Si-Cd treatment. The activity of POD in the root of the Cd-stress side and that of SOD in non-stress side were significantly increased, which benefit to scavenging the free radicals induced by Cd stress. In conclusion, Si could regulate the growth of rice seedlings, the uptake of elements such as Cd and Si, and the antioxidant reaction of the root system under the Cd stress. High Si concentration in plant is conducive to enhancing Cd tolerance.

Impacts of cuprous oxide nanoparticles on wheat root morphology and genotoxicity

MA Zhan-qiang, XU Yan-chong, FAN Zhen-jie, HOU Dian-yun, XU Qiu-yue

2021, 32(3):  1105-1111.  doi:10.13287/j.1001-9332.202103.031

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To explore the ecotoxicity of Cu₂O nanoparticles (NPs) on plant roots, the effects of Cu₂O-NPs with different concentrations of 10, 50, 100 and 200 mg·L^-1 on the seedling growth, root morphology, and cytogenetic toxicity of wheat ‘Zhoumai 18’ (Triticum aestivum Zhoumai 18) were examined in a hydroponic experiment. The results showed that Cu₂O-NPs inhibited the growth of wheat seedlings. Cu₂O-NPs reduced root and shoot lengths, fresh weights of shoot and root, root relative activity and ratio of root to shoot of wheat seedlings, but increased primary root number. Furthermore, with the increases of Cu₂O-NPs concentrations, the root elongation zone shortened and the root became hard and brittle, while the average diameter of roots increased. Under the concentration of 100 mg·L^-1 Cu₂O-NPs, the mitotic index significantly decreased, and vacuolization, plasma membrane detachment, chromosomal abnormality occurred in the root tip cell. In conclusion, Cu₂O-NPs are genotoxic to wheat seedlings, with consequences on the growth and development of wheat seedlings and root morphology.

Reviews

Effects of deficit irrigation on cotton growth and water use efficiency: A review

YANG Bei-fang, YANG Guo-zheng, FENG Lu, HAN Ying-chun, LEI Ya-ping, FAN Zheng-yi, WANG Zhan-biao, LI Ya-bing

2021, 32(3):  1112-1118.  doi:10.13287/j.1001-9332.202103.026

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Cotton is one of the most important crops in the world. With the increasing scarce of global water resources, irrigation water will become a major limiting factor in cotton production. Deficit irrigation is an irrigation method which consumes less water than the normal evapotranspiration of crops. It is an effective water-saving method due to improved water use efficiency without sacrificing cotton yield and fiber quality. We summarized the effects of deficit irrigation on the growth and water use efficiency of cotton. The results showed that deficit irrigation promoted the transformation from vegetative growth to reproductive growth, reduced plant height, leaf area, and total biomass of cotton, and subsequently improved the harvest index, stem diameter and water use efficiency. Finally, based on the current research and combined with cotton production reality, the application and future development of deficit irrigation were proposed, which might provide theoretical guidance for the sustainable development of cotton plantation in arid areas.

Application of ecoacoustic monitoring in the field of biodiversity science

BIAN Qi, WANG Cheng, HAO Ze-zhou

2021, 32(3):  1119-1128.  doi:10.13287/j.1001-9332.202103.032

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Sound is an important way of communication among organisms. The monitoring and analy-sis of biological sound is an emerging method to describe and evaluate biodiversity. This method does not invade or damage the natural environment. By recording ecological information through sound, it can effectively reflect the relevant characteristics of biodiversity. The sound-based exploration of biodiversity change has broadened the interdisciplinary approach and has been increasingly applied to ecological research. Here, we expounded on the main theoretical foundations and research methods of using acoustic monitoring to assess biodiversity. We introduced related research fields from two aspects, namely the biodiversity of vocal animals and the temporal and spatial diversity of soundscape. We presented examples of the application of acoustic monitoring to assess the impact of land-use change, climate change and urbanization on biodiversity. Finally, we proposed the future direction of development, and hope that the potential of sound surveys could be further explored to provide an effective reference for biodiversity monitoring and assessment.

A review on aquatic ecosystem mesocosms

WANG Jia-wen, HE Ping, XU Jie, DING Sen

2021, 32(3):  1129-1140.  doi:10.13287/j.1001-9332.202103.030

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Aquatic ecosystem mesocosm refers to an artificially constructed near-natural simulation facility in aquatic ecosystem. With aquatic ecosystem mesocosms, experiments on the responses of biological communities can be conducted by controlling physical, chemical and other habitat conditions. Mesocosm experiments can bridge the gap between laboratory experiments and field experiments. Laboratory experiment can only simulate a small number of simple factors, whereas field experimental systems are complex and difficult to conduct controlled experiments. By resear-ching into global long-term mesocosms, we classified them into four types, i.e. flowing type mesocosm, enclosure, land-based simulation pool and mobile experimental tank. The meoscosms gene-rally include physical-biological simulation system, automatic control system, monitoring and analysis system, and central control system. In recent years, aquatic ecosystem research in China has gradually changed from a single environmental factor to the whole ecosystem. We suggest that the construction of the mesocosms in China’s aquatic ecosystem should increase the structural complexity and be combined with field in situ monitoring to support large scale simulation.