Table of Content

15 March 2020, Volume 31 Issue 3

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Functions and applications of Multi-Tower Platform of Qingyuan Forest Ecosystem Research Station of Chinese Academy of Sciences

GAO Tian, YU Li-zhong, YU Feng-yuan, WANG Xing-chang, YANG Kai, LU De-liang, LI Xiu-fen, YAN Qiao-ling, SUN Yi-rong, LIU Li-fang, XU Shuang, ZHEN Xiao-jie, NI Zhen-dong, ZHANG Jin-xin, WANG Gao-feng, WEI Xiao-hua, ZHOU Xin-hua, ZHU Jiao-jun

2020, 31(3):  695-705.  doi:10.13287/j.1001-9332.202003.040

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The relationship between the structure and function of forest ecosystems is the main intere-sts in the research area of forest ecology and management. However, over complex terrains in particular, these studies had been challenged as uneasy tasks due to the limitations in the forest survey and measurement techniques and other supporting technologies. Chinese Academy of Sciences (CAS) funded “Multi-Tower LiDAR/ECFlux Platform for Monitoring the Structure and Function of Secondary Forest Ecosystems” (Multi-Tower Platform, MTP) as a field station network corner-stone research infrastructure project, which was completed by Qingyuan Forest CERN (Chinese Ecosystem Research Network). In a distinctively-bounded and monitored-outlet watershed, the MTP was integrated by light detection and ranging (LiDAR) scanners, eddy covariance (EC) flux instrument systems, whole- and sub-watershed hydrology station network, long-term forest plot arrays, and live data center. Using LiDAR scanning, the MTP can get cloud data for holographic information on canopy structure. The EC-flux instrument system and hydrology station network along with forest plot arrays could ensure the reliability of water and carbon observations over this complex terrain, which allows to verify the studies on flux measurement technologies and methods, as well as to understand the processes of ecohydrology and CO₂ exchange between forest ecosystem and the atmosphere. Further, we can also assess the primary ecosystem services, including water conservation and carbon sequestration. All the data from “tower-station” were streamed through wireless network, which would facilitate data monitoring, management, and sharing. There are three tasks of MTP team: 1) defining innovative methods and descriptors to quantify three-dimensional forest structure; 2) developing theories and techniques to measure CO₂/H₂O fluxes and other trace gases over complex terrains; 3) understanding the relationship between structure and function of forest ecosystems, providing information and rationales for forest management practices to assure broad and sustainable benefits from forests.

Changes of productivity with stand development in broadleaf-Korean pine forest in Changbai Mountain, China

LI Xu-hua, YU Da-pao, DAI Li-min, SUN Jian-xin

2020, 31(3):  706-716.  doi:10.13287/j.1001-9332.202003.018

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Stand age is a key factor affecting carbon stocks and fluxes of forest ecosystem. Quantification of the changes in forest productivity with stand development is critically important for optimizing forest age structure, facilitating maximum utilization of resources, and better realizing the role of forests in regulating the uptake, storage, and emission of CO₂. In this study, using space for time substitution approach, we established 12 chronosequence plots in the broadleaf-Korean pine forests of Lushuihe. Using a locally parameterized Biome-BGC model, we simulated the dynamics of net primary productivity (NPP) with stand development and examined the changes with stand development in NPP of broadleaf-Korean pine forests under four developmental scenarios. Results showed that the biomass in broadleaf-Korean pine forests of different age-classes ranked in the order of young stand < mid-age stand < mature stand < over-mature stand, with the average value of (224.35±20.68), (237.23±39.96), (259.16±19.51), and (357.57±84.74) t·hm^-2, respectively. Modelled NPP in broadleaf-Korean pine forests of different developmental stages varied in the range of 489.8-588 g C·m^-2·a^-1, which were consistent with the observed data of MODIS NPP, highlighting the adequacy and accuracy of Biome-BGC model in simulating the carbon flux of broadleaf-Korean pine forests. Simulated NPP displayed a pattern of initial increase and later decrease with stand development, reaching peak in the mid-age stand and being smallest in the over-mature stand. Simulations of NPP in broadleaf-Korean pine forest under four developmental scenarios showed that, for the two scenarios with planted Korean pine forests experiencing either natural development or controlled cutting, NPP was highest in the mature stage; whereas for the two scenarios with initial natural secondary birch forests experiencing either natural development or controlled cutting, NPP was highest in the young stage.

Effects of retention density on growth, biomass, and economic benefit of Cunninghamia lanceolata plantation

LU Li-hua, NONG You, LI Hua, ZENG Ji, SUN Dong-jing, CHEN Lin, MING An-gang, YANG Yu-jing

2020, 31(3):  717-724.  doi:10.13287/j.1001-9332.202003.002

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We examined the effects of retention density on plant DBH (diameter at breast height), height, volume growth, stand biomass, and stand economic benefit of Cunninghamia lanceolata plantation by Pingxiang, Guangxi Province. Four treatments of different retention density were set up a 14-year middle-aged Cunninghamia lanceolata plantation, 500, 750 and 1000 trees·hm^-2, with stand without thinning as the control (1500 trees·hm^-2). Results showed that DBH (20.55 cm), increment in height (15.70 m), and large-diameter timber volume (18.31 m³·hm^-2) of the C. lanceolata plantation were the highest in 500 trees·hm^-2 treatment. The volume of living trees was the highest in the control (199.63 m³·hm^-2), which was significantly higher than that in 500 and 750 trees·hm^-2. The biomass of arbor layer and ecosystem, as well as the economic benefit differed significantly across the treatments, with arborous biomass (90.72 t·hm^-2), ecosystem biomass (94.97 t·hm^-2), and economic benefit (1.184×10⁵ yuan·hm^-2) of 1000 trees·hm^-2 treatment being significantly higher than others. Reducing stand retention density increased the DBH, plant height, timber diameter, proportion of large diameter timber, average volume and biomass of single timber, but it did not enhance the volume of living trees. The retention density of 1000 trees·hm^-2 was the optimum for middle-aged C. lanceolata plantation. Compared with the control, it significantly increased the total stand volume, arbor biomass, ecosystem biomass, and economic benefit by 2.3%, 5.7%, 4.7%, and 5.8%, respectively.

Effects of plant roots on soil preferential flow in typical forest and grassland in the dry-hot valley of Jinsha River, China

SHAO Yi-min, ZHAO Yang-yi, DUAN Xu, WANG Ke-qin, CHEN Ting-ting, WAN Yan-ping

2020, 31(3):  725-734.  doi:10.13287/j.1001-9332.202003.013

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To clarify the morphological characteristics of soil preferential flow and the effect of plant roots on its formation, plants from the typical vegetation types of an artificial woodland (Leucaena acacia) and a dry watershed grassland (Heteropogon contortus) of Yuanmou County, Jinsha River were selected as the experimental objects. Based on the staining and tracing method combined with Photoshop CS5 and the Image-Pro Plus 6.0 image processing technology, we analyzed the morphological and distribution characteristics of soil preferential flow under the two planting types and examined the effects of plant roots. We found significant difference in soil preferential flow dyeing area between the woodland and grassland species, and the overall variation trend of the forestland dyeing area ratio decreased with increasing soil depth. The dyeing area of the grassland decreased monotonously with the increases of soil depth. The occurrence degree of soil preferential flow in forest was higher than that of grassland. Root systemaffected the formation of soil preferential flow. At the root diameter ranges of 0≤d≤5 mm and d>10 mm, root length density of the woodland showed a monotonous decreasing trend with increasing soil depth, while in the root diameter range of 5 mm<d≤10 mm, it fluctuated in the 30-40 cm soil layer. Root length densities at all the root diameter levels of desert grassland were negatively correlated with soil depth. The dyeing area ratio of the woodland was significantly correlated to root length density in the 3 mm<d≤5 mm root diameter range, while that of the grassland was significantly correlated to root length density in the d≤3 mm range. The dyeing area ratio of both land types showed significant correlation with root weight density in the range of 1 mm<d≤3 mm and with root surface area of d≤1 mm, but did not correlated with root length density, root weight density, and root surface area in the root diameter range of d>5 mm. The overall change trend of soil preferential flow dyeing area of two vegetation types in the study area decreased with increasing soil depth. Plant root system was closely related to the formation of soil preferential flow. Fine roots could promote while coarse roots may retard the formation of preferential flows.

Effects of shrub patch pattern on runoff and sediment yield

ZHAO Ming, YANG Xiao-nan, CHEN Pan-yu, SUN Wen-yi, MU Xing-min, GAO Peng, ZHAO Guang-ju

2020, 31(3):  735-743.  doi:10.13287/j.1001-9332.202003.017

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Understanding the changes of runoff, sediment transport, and hydrodynamic parameters of slopes under the influence of landscape patch coverage and connectivity is of great significance for revealing the hydrodynamic mechanism and hydrological connectivity of slope soil erosion process. In this study, the changes of runoff, sediment transport and hydrodynamic parameters of downhill surface in different coverage levels (0%, 20%, 40%, 60%, 90%) and different connectivity modes (vertical path, horizonal path, S-shaped path, random patches) of shrublands were analyzed by field artificial simulated rainfall test. The results showed that, with the increases of shrub cove-rage, runoff yield and sediment yield decreased exponentially. When the coverage increased to more than 60%, the capacity of shrubs to reduce runoff and sediment became stable. With the increases of shrub coverage, flow velocity, flow depth, Reynolds number, Froude number, stream power, and flow shear resistance significantly decreased, while Manning’s roughness coefficient and Darcy-Weisbach resistance coefficient increased significantly. When shrub coverage increased to more than 60%, there was no significant difference in the eigenvalues of hydraulic parameters. The runoff rate under the four connectivity modes followed the order of vertical path > S-shaped path > horizonal path > random patches. The sediment rate was the largest in the vertical path, followed by the S-shaped path, and the horizonal path was not significantly different from the random patches. The path with poor connectivity (horizonal path, random patches) exhibited stronger resistance of hydraulic transmission and poor hydraulic sedimentation capacity than the well-connected path (vertical path, S-shaped path). Our results could provide important theoretical basis for soil erosion control on the Loess Plateau and high-quality development of the Yellow River basin.

Dynamics of soil respiration and its influencing factors in urban forests under nitrogen addition

FU Ruo-xian, YU Jing-song, ZHANG Yun-bin, YU Yuan-chun, TAO Xiao

2020, 31(3):  744-752.  doi:10.13287/j.1001-9332.202003.037

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Urban forest is an important carbon pool, soil respiration of which is an important part of terrestrial carbon cycle. To understand the dynamics and influencing factors of soil respiration in urban forest under the background of increasing nitrogen deposition, we conducted dynamic observation on soil respiration rate, temperature, moisture and chemical properties by adding 0 (CK), 50 (LN), 100 (HN) kg N·m^-2·a^-1 ammonium nitrate to a typical urban forest. The results showed that soil respiration had significant seasonal variation, which was not affected by nitrogen addition. Soil respiration was significantly correlated with soil temperature. The interaction between soil temperature and soil moisture could better explain the variation of soil respiration. Nitrogen addition changed temperature sensitivity of soil respiration, with the order of Q₁₀ values as LN (2.12) > CK (2.10) > HN (2.05). Soil nitrate concentration, soil soluble organic carbon, pH, soil carbon to nitrogen ratio had significant correlation with soil respiration. The positive effect of nitrogen deposition on soil respiration was mainly in the growing season, with slightly inhibitive effect in the non-growing season.

Responses of soil phosphorus fractions and microorganisms to nitrogen application in a subtropical Phyllostachys pubescen forest

ZENG Quan-xin, ZENG Xiao-min, LIN Kai-miao, ZHANG Qiu-fang, CHENG Lei, ZHOU Jia-cong, LIN Qiao-yu, CHEN Yueh-min, XU Jian-guo

2020, 31(3):  753-760.  doi:10.13287/j.1001-9332.202003.033

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Phosphorus (P) is an important nutrient for plant and microbial growth. Soil P availabi-lity is poor in subtropical areas. Long-term heavy nitrogen (N) deposition might further reduce P availability. The experiment was performed in a Phyllostachys pubescens forest in Daiyun Mountain. The effects of N application on soil basic physical and chemical properties, soil P fractions, microbial biomass, and acid phosphomonoesterase activity were analyzed after three years of N application. The results showed that N application significantly increased NO₃^--N content and thus soil N availability, while it significantly reduced the percentage of decomposable organic P to total P, with the ratio of carbon (C) to organic P being over 200. The soil microbial biomass C, microbial biomass P, acid phosphomonoesterase, and the ratio of microbial biomass N to microbial biomass P and microbial biomass C to microbial biomass P were increased as the N application rate increased. There was a significant negative correlation between the percentage of decomposable organic P to total P and microbial biomass P. Consequently, N application enhanced soil P limitation and increased microbial P demand.

Difference of soil nematode communities between the humus and soil surface layer in the cold temperate coniferous and broadleaved mixed forest of Yulong Snow Mountain Nature Reserve, Yunnan, China

WANG Wen-ting, XIA Shang-wen, XIAO Hai-feng, LIU Sheng-jie, YANG Xiao-dong

2020, 31(3):  761-768.  doi:10.13287/j.1001-9332.202003.020

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A high-throughput sequencing approach was used to differentiate the nematode communities in the humus and soil surface layer (0-10 cm) in 20 hm² plot located in the cold temperate coniferous and broadleaved mixed forest of Yulong Snow Mountain Nature Reserve, Lijiang, Yunnan. A total of 5744582 sequences were obtained, which were further annotated to 44 nematode families. In the humus layer, 37 families were recorded, with Tylenchidae (18.1%) being the most dominant family. For trophic groups, bacterivorous, fungivorous and herbivorous were predominant. The soil surface layer had 41 families, with Mononchidae (45.4%) being the most dominant family. The relative abundance of predatory nematode was highest in the soil surface layer. There was no significant difference in the α diversity indices (Shannon, Simpson and Chao1 index) of nematode communities at the OTU level between two habitats. At the family level, however, α diversity of nematode community in the humus layer was significantly lower than in soil surface layer. β diversity of the nematode community was significantly different in the two habitats, with lower Cody index but high Sorensen non-similarity index in the humus habitat. Results of non-metric multidimensional scaling (NMDS) analysis showed that the internal structure difference of nematode community in the soil surface layer was higher than that in the humus layer.

Effects of shading on photosynthetic characteristics and chlorophyll fluorescence parameters of four Corydalis species

WANG Ya-nan, DONG Li-na, DING Yan-fen, LI Han, SONG Peng, CAI Hui, XU Zi-han

2020, 31(3):  769-777.  doi:10.13287/j.1001-9332.202003.004

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We examined the effects of five shading treatments (0, 20%, 40%, 60% and 80% shading) on chlorophyll content, photosynthetic characteristics, and chlorophyll fluorescence chara-cteristics of four Corydalis species (C. incisa, C. decumbens, C. edulis and C. pallida) in a pot experiment. The results showed that the contents of chlorophyll a, chlorophyll b and chlorophyll (a+b) increased with the increment of shading, with that of C. incisa reaching the maximum under 80% shading treatment and that of C. decumbens, C. edulis and C. pallida reaching a maximum under 60% shading treatment. In contrast, chlorophyll a/b, light saturation point, light compensation point and dark respiration rate decreased with increasing shading. Among the four Corydalis species, C. incisa reached up to the maximum chlorophyll fluorescence parameters under 80% shading treatment, and C. decumbens, C. edulis and C. pallida reached the maximum at 60% shading treatment. The shade tolerance of four species was as follows: C. incisa ＞ C. decumbens ＞ C. edulis ＞ C. pallida. C. incisa under 80% shading treatment and C. decumbens, C. edulis, C. pallida at 60% shading treatment had the highest light energy utilization and photosynthetic capacity, which would facilitate their growth.

Responses of plant growth of different life-forms to precipitation changes in desert steppe

WANG Jun-feng, ZHANG Li-hua, ZHAO Rui-feng, XIE Zhong-kui

2020, 31(3):  778-786.  doi:10.13287/j.1001-9332.202003.001

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Under the background of global climate change, precipitation changes will have profound impacts on plant community dynamics. Through field experiment with precipitation manipulation in a desert steppe of western Loess Plateau, we examined the responses of species richness, density, coverage, height and aboveground biomass of different plant life-forms to precipitation changes. The results showed significant effects of precipitation on richness, density and coverage of annual herbs in the third year of manipulation experiment (2015), with lowest values in the decreased precipitation treatments. The height of annual herbs was more sensitive to precipitation changes, and was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of growth and aboveground biomass of annual herbs to decreased precipitation were larger than that to increased precipitation. Richness, density and coverage of perennial herbs in the decreased precipitation were significantly lower than those in the +40% precipitation in the 3rd year, but were insignificantly different from the control. The height of perennial herbs was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of richness, coverage and height of perennial herbs to decreased precipitation were larger than positive response to increased precipitation, while the positive response of aboveground biomass to the +40% precipitation treatment was stronger. The positive responses of richness, density, coverage and aboveground biomass of shrub to ±20% precipitation treatments were most obvious, which might be related to the relatively concentrated distribution of shrub in these treatments. The precipitation reduction inhibited the growth of herbaceous plants, particularly on the annual herbs, whereas increasing precipitation promoted perennial herbaceous growth and biomass accumulation to some extent. The annual herbaceous growth and biomass fluctuated with interannual variation of precipitation. Shrubs were relatively less affected by precipitation changes. Precipitation changes would have significant effects on plant community composition and function of desert steppe in western Loess Plateau.

Effects of community succession on plant reproductive allocation and ecological stoichiometry for two dominant species in the Hulunbuir Grassland, China

JIN Xiao-ming, YU Liang-bin, ZHANG Ying-qi, WANG Qiu-hong

2020, 31(3):  787-793.  doi:10.13287/j.1001-9332.202003.003

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To explore the physiological and ecological adaptability of different dominant species during grassland community succession, we measured soil nutrients, plant biomass and C, N and P contents of two dominant species using the method of spatial sequences instead of chronosequences in the successive series of Agropyron michnoi community - A. michnoi + A. cristatam community - A. cristatam community in Hulunbuir Grassland. During the succession progress, the contents of soil total C, total C, available N and available P increased significantly. The N and P contents and N/P of leaves, stems and roots of A. michnoi and A. cristatam increased significantly, while the C/N showed opposite response. The leaf C content of A. michnoi and the C contents of leaves, stems and roots of A. cristatam significantly increased. The leaf C/P of A. michnoi and the C/P of leaves and roots of A. cristatem increased significantly, while the C/P of stems and roots of A. michnoi and the stem C/P of A. cristatem decreased significantly. In the community co-dominated by A. michnoi and A. cristatam, A. michnoi improved its interspecific competitiveness by reducing C content in stems and roots and increasing the C content in leaves, while A. cristatem adapted to environmental changes by reducing root to shoot ratio and reproductive ratio. A. michnoi was limited by N availability (N/P<14) in different communities, while A. cristatem was limited by P availability in single dominant community(N/P>16)and by both N and P in co-dominant community (14<N/P<16). The index of stoichiometric homoeostasis of foliar N of A. michnoi in the single dominant community and the co-dominant community were 5.92 and 2.94, respectively, indicating higher N stability, while the index of stoichiometric homoeostasis plant of foliar P of A. cristatem in the single dominant community and the co-dominant community were 4.12 and 3.37, respectively, which indicated higher P stability.

Spatio-temporal characteristics of the matching degree of water, soil, and heat resources based on ecosystem services in Central Asia

YAN Xue, MENG De-kun, CHEN Di-tao, LI Qian, YANG Tao, LI Lan-hai

2020, 31(3):  794-806.  doi:10.13287/j.1001-9332.202003.012

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The status of matching degree among water, soil, and heat resources determines ecosystem stability and sustainability. Under the framework of ecosystem services related to human well-being, we constructed the matching index of water, soil, and heat resources in Central Asia by the vegetation net primary productivity (NPP) index method based on remote sensing data. We analyzed the spatio-temporal characteristics of the matching degree in Central Asia, and correlations between the matching degree and climatic factors, water use efficiency using trend analysis and the Hurst index. The results showed that the matching degree of water, soil, and heat resources was generally low in Central Asia with a mean value of 9.3. There were obvious differences in the mat-ching degree in different biomes, with the order of alpine forest region > alpine meadow region > typical steppe region > desert steppe region > lake > desert region. From 2000 to 2015, the matching degree of water, soil, and heat resources in each biome and in the whole Central Asia showed a fluctuating downward trend. However, the matching degree changed slightly, with relatively poor persistence. There was a large difference and misalignment of spatial variation in temperature and precipitation, which was the main cause of low matching degree of water, soil, and heat resources. The effect of precipitation on the matching degree of water, soil, and heat resources in Central Asia was stronger than that of the temperature. There was a strong correlation between the matching degree and water use efficiency in Central Asia.

Nutrient resorption patterns of Phragmites australis leaves and its response to soil moisture in Yangguan wetland, Dunhuang, Northwest China

LIU Dong, ZHANG Jian, BAO Ya-lan, ZHAO Hai-yan, QI Xuan-xuan, XIE Huan-jie, ZHANG Jing-bai

2020, 31(3):  807-813.  doi:10.13287/j.1001-9332.202003.031

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Nutrient resorption of leaves is an important nutrient conservation mechanism for plants in nutrient-poor habitats. Understanding the responses of leaf nutrient resorption to soil moisture is helpful to reveal the adaptation strategies of plants to the environment. In this study, the dominant plant in the Yangguang wetland of Dunhuang Phragmites australis was used as research material, to explore nitrogen and phosphorus resorption patterns of P. australis leaves and their responses to soil moisture under different moisture regimes, i.e. high (33.5%±1.9%), medium (26.4%±1.3%) and low (11.3%±1.5%). The results showed that: 1) With the decreases of soil moisture, soil N concentration decreased significantly, and N concentrations in mature and senescent leaves increased significantly, the P concentration in mature and senescent leaves as well as in soil did not change. 2) N resorption efficiency of leaves under high moisture condition was 76.1%, which was significantly higher than the medium (65.5%) and low (62.5%) moisture conditions. P resorption efficiency varied among different moisture conditions. 3) The N concentrations of mature and senescent leaves were negatively correlated with N resorption efficiency. There was no significant correlation between P concentration and P resorption efficiency in mature leaves, but the P concentration of senescent leaves was negatively correlated with P resorption efficiency of leaves. As a result, water scarcity is not conducive to leaf N resorption.

Responses of soil potential carbon/nitrogen mineralization and microbial activities to extreme droughts in a meadow steppe

LI Lei, WANG Yan, HU Shu-ya, LI Yang, SHEN Yan, YU qiang, HUANG Jian-hui, WANG Chang-hui

2020, 31(3):  814-820.  doi:10.13287/j.1001-9332.202003.005

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The mineralization of soil carbon (C) and nitrogen (N) is a critical process in the cycling of C and N in terrestrial ecosystems, which is strongly controlled by water availability. In this study, we collected soil samples in a 3-year extreme drought experiment in a meadow steppe in Inner Mongolia, freeze-dried these samples, and measured the potential C and N mineralization rates and water sensitivity of soil microorganism by incubating soils under soil water contents (SWC) of 3%, 8%, 13%, 18%, 25% and 35%. The results showed that averaged across different SWC, the extreme drought treatment of reducing 66% precipitation in growing season significantly increased potential N mineralization rate by 14.2%, but did not affect the potential C mineralization. Extreme drought significantly increased soil microbial biomass N and soil dissolved organic C by 26.8% and 26.9%, respectively. In both the control (natural rainfall) and extreme drought treatment, the potential C and N mineralization and microbial biomass C and N increased with SWC in the incubation, which was possibly caused by the enhanced substrate diffusion. Extreme drought also promoted the initial pulse response of C mineralization, implying the enhanced microbial response to water availability. Extreme drought significantly reduced the ratio of the potential soil C mineralization to the potential N mineralization, suggesting that extreme drought might weak the coupling of soil C and N. Extreme drought could cause different responses to soil water availability between soil C and N cycling. Extreme drought could enhance microbial response to increasing water availability, weak coupling between soil C and N, with consequences on nutrient cycling and primary productivity in the meadow steppe of northern China.

Spatial variability of soil water content in field of Guanzhong Plain, Northwest China

ZHANG Shi-qi, NIU Wen-quan, LI Guo-chun

2020, 31(3):  821-828.  doi:10.13287/j.1001-9332.202003.024

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To clarify the spatial variability of soil water content at field scale, a reasonable sampling method was established to support precision irrigation in the field. Soil samples were collected from Caoxinzhuang experimental area in Yangling District, Shaanxi Province at seven different dates. The spatial variation of soil water content in different soil layers of 0-60 cm were analyzed with classical statistics and geostatistics methods. The results showed that spatial distribution of soil water content in field scale was weak and moderate. When soil water content was within the range of 11.7%-20.1%, soil water content was negatively correlated with spatial variability. Sampling interval signifi-cantly affected the calculation accuracy of the spatial variability of soil water content. The coefficient of variation of soil water content between the east-west direction spacing of 27 m and the north-south direction spacing of 9 m was about 3.3% higher than the east-west direction spacing of 9 m and the north-south direction spacing of 18 m. With increasing sampling density, the contour change of soil water content distribution increased, and the number of grids with the least spatial variability of soil water content at the field scale was 21 points. When the sampling spacing was 18 m in the east-west direction, 9 m in the north-south direction, soil water content at field scale had a high spatial distribution correlation with soil water content in the middle position being 3%-5% higher than the surrounding. Our results provided reference for reasonable sampling of soil water content in the Guanzhong Plain and could guide the precision irrigation in agriculture.

Effect of soil moisture on water potential gradients in the soil-plant-atmosphere continuum (SPAC) of apple orchards in the Loess Plateau, Northwest China

DANG Hong-zhong, QUE Xiao-e, FENG Jin-chao, WANG Meng-meng, CHEN Shuai

2020, 31(3):  829-836.  doi:10.13287/j.1001-9332.202003.023

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The variations of water potential gradients through the soil-plant-atmosphere continuum (SPAC) are of great significance to reveal the responses of plant water use to environmental changes. We conducted a continuous experiment to monitor the potentials in the near-canopy atmosphere (Ψ_air), soil (Ψ_soil) and plant xylems (Ψ_stem) during the growing season in an apple orchard located in the Loess Plateau. The results showed that the average Ψ_stem during the growing season ranged from -0.24 to -2.0 MPa, with a mean value of -0.57 MPa. The average water potential gradient in soil-plant-atmosphere system was 1:9.8:1155 (Ψ_soil:Ψ_stem:Ψ_air). We found a significant positive linear correlation between the Ψ_stem:Ψ_soil gradient and volumetric soil water content (VWC, %). The Ψ_stem was more strongly correlated with Ψ_soil than Ψ_air. Moreover, the sensitivity of Ψ_stem to Ψ_soil decreased when Ψ_soil was lower than -0.08 MPa which corresponded to VWC=17%, 0.56 times of field capacity. This was reflected by the increased linearity between Ψ_air /Ψ_stem and Ψ_soil as Ψ_soil decreased. There was a threshold effect for the relationship between Ψ_air and Ψ_stem. That is, the Ψ_stem in a day increased with the increasing of Ψ_air before the latter reached -69 MPa, after which the Ψ_stem decreased. The decline of soil water content caused an obvious decrease in water potential gradient through the SPAC system, and the threshold effect existed when VWC was below 17%. The results provide a basis for understanding the mechanisms of plant water in response to soil and atmospheric drought.

Responses of soil aggregate-associated organic carbon and nutrients to tea cultivation age in southern Guangxi, China

WANG Sheng-qiang, DU Lei, YE Shao-ming

2020, 31(3):  837-844.  doi:10.13287/j.1001-9332.202003.008

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Understanding the response mechanism of soil aggregate-associated organic carbon (OC) and nutrients to tea cultivation age can lay a theoretical foundation for improving soil fertility, ensuring soil health, and promoting sustainable utilization of soil resources in the tea plantations. In this study, concentrations of soil OC and nutrient were analyzed in >2, 2-1, 1-0.25, and <0.25 mm fractions (split by a dry-sieving procedure) at the 0-20 cm soil layer in four tea plantations with Baimao tea of different ages (8, 17, 25, and 43 a) in southern Guangxi, China. The distribution of soil aggregates showed that the dominant aggregates were >2 mm fractions with a mean value of 63.8%, followed by <0.25 mm fractions, while 2-1 and 1-0.25 mm fractions with mean values of 9.9% and 7.8%, respectively. As an indicator of soil aggregate stability, the mean weight diameter (MWD) in the tea plantations showed an order of 17 a >8 a >25 a >43 a. Regardless of tea cultivation age, soil aggregate-associated OC and total nitrogen (TN) concentrations increased with increasing aggregate size. Soil OC and TN concentrations in >2 and 2-1 mm fractions were significantly higher than those in other fractions. The mean values of soil OC and TN concentrations were 18.76 and 0.84 g·kg^-1 in the >2 mm fractions, and were 18.65 and 0.80 g·kg^-1 in the 2-1 mm fraction. Soil aggregate-associated available nitrogen (AN), available phosphorus (AP), and availa-ble potassium (AK) concentrations were highest in the <0.25 mm fractions with mean values of 50.43, 23.06, and 68.04 mg·kg^-1, respectively. Long-term tea cultivation was favorable to the accumulation of soil OC, TN, AN, and AP, whereas the accumulation rates of these element stocks in the whole soil decreased with increasing tea cultivation age. In contrast, soil AK was susceptible to leaching in tea cultivation, with the loss rate of this element stock in the middle stage (from 17 to 25 a) being higher than those in the other stages. To ensure soil quality and promote the sustainable utilization of soil resources, more attention should be paid to the problems such as the decrease of soil aggregate stability and the aggravation of AK loss after 17 a of tea cultivation.

Phenological responses of apple tree to climate warming in the main apple production areas in northern China

LIU Lu, GUO Liang, WANG Jing-hong, LUAN Qing, FU Wei-dong, LI Man-hua

2020, 31(3):  845-852.  doi:10.13287/j.1001-9332.202003.026

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To reveal the spatio-temporal variation characteristics of apple’s phenology and their critical response time period and intensity to the temperature change in the main production areas of northern China, we chose Fushan, Wanrong and Akesu to respresent the Bohai Gulf, the Loess Plateau and Xinjiang apple production areas, respectively. Apple’s phenology data of buds opening (BO), first leaf unfolding (LU), first flowering (FF), fruit maturing (FM), end of leaf coloring (LC) and the end of leaf fall (LF) at the three stations during 1996-2018 were used to analyze the changes of phenological occurrence dates and different growth stage lengths. Partial least squares (PLS) regression was applied to identify the impacts of climate warming on different phenology events at daily resolution. Results showed that regional mean occurrence dates of apple’s BO, LU and FF advanced by a rate of 0.36, 0.33 and 0.23 day per year, respectively. However, apple’s LF postponed by 0.68 d·a^-1. The FM and LC showed different trends among all the sites. The length of fruit growing period (FG) and that of tree growing period (TG) extended at average rates of 1.20 and 0.82 day per year. Apple’s spring phenophases dates at all stations correlated negatively with mean temperature during early January to pre-phenophases date, with a 1 ℃ increase inducing an advancement of 3.70, 3.47 and 3.48 days for apple’s BO, LU and FF, respectively. In contrast, apple’s autumn phenophases correlated positively with mean temperature 21-72 days before the phenophases date, and its correlation with mean temperature was lower than the correlation for spring phenophases. Generally, the effect of temperature on spring phenophase was stronger than that of autumn phenophase, and the extension of FG and TG was mainly caused by the advance of spring phenophase. The responses of apple’s phenophases to climate warming differed across all the stations. Temperature had the greatest impact on the development of apple industry in Akesu, less in Wanrong, and with the least influence in Fushan. Our results could provide theoretical basis for response to climate change for apple industry in different areas of China.

Estimating the climatic capacity of food security in Henan Province, China under the future climate change scenarios

JI Xing-jie, XU Yan-hong, ZUO Xuan, FANG Wen-song, LU Yan-yu

2020, 31(3):  853-862.  doi:10.13287/j.1001-9332.202003.011

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To explore the effects of future climate change on food production in Henan Province, the climate potential productivity and its change characteristics in Henan Province were calculated by agro-ecological zone (AEZ) model. This study was based on the production potential and climate resource carrying capacity of summer maize and winter wheat, combined with the observation data of 111 meteorological stations in Henan Province from 1961 to 2017 and the meteorological data under two emission scenarios of RCP4.5 and RCP8.5 in 2041-2080. With the grain demand index under different living standards, we analyzed climate carrying capacity and surplus space of Henan Pro-vince. The results showed that the average climatic potential productivity of maize was 18408.87 kg·hm^-2 from 1961 to 2017, with high values in the middle and east, and low values in the west. Compared with the reference period (1981-2010), climatic potential productivity of maize under RCP4.5 and RCP8.5 decreased by 13.0% and 8.0% respectively, with the high value center shifting from the east to the southwest of Henan. The average climatic potential productivity of wheat was 10889.79 kg·hm^-2, which was high in the middle region and low in the north. Compared with the reference period, climatic potential productivity of wheat under RCP4.5 and RCP8.5 decreased by 18.6% and 21.7%, respectively. Under the current condition of subsistence and well-off food demand, the maximum carrying capacity of climate resources respectively could support 252 million and 183 million people. In 2070s (2071-2080), the average supporting population of the maximum climate resource carrying capacity (C_max) would decrease. Compared with the reference period, C_max under the level of well-off and subsistence would decrease by 9.7% and 18.4% respectively in RCP4.5 scenario, and 7.7% and 16.6% respectively in RCP8.5 scenario. Under current climate condition, the relative surplus rate of climate resources in Henan Province ranged from -93.0% to 356.9%. Compared with the reference period, the relative residual rate of climate resources in the future would reduce nearly 40%.

Hyper-spectral inversion of soil organic carbon content under different land use types

GUO Jia-xin, ZHU Qing, ZHAO Xiao-min, GUO Xi, HAN Yi, XU Zhe

2020, 31(3):  863-871.  doi:10.13287/j.1001-9332.202003.014

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Soil spectral information differ across different land use types. Understanding the appropriate modeling methods for different land use types can efficiently and accurately invert soil organic carbon content. We collected 248 samples from forest, cultivated land and orchard in the north-central part of Fengxin County, Jiangxi Province. First, original spectral reflectance curves were reduced noises with Savitzky-Golay (SG) filter. Then 10 nm resampling method was used to reduce data redundancy. We used partial least squares regression (PLSR), support vector machine regression based on grid search method (GRID-SVR) and support vector machine regression based on particle swarm optimization (PSO-SVR) to construct the inversion models of soil organic carbon content. The results showed that when constructing a single land-use type inversion model, RPD of the PLSR method for forest, cultivated land and orchard was 1.536, 1.315 and 1.493 respectively. RPD of GRID-SVR method increased 0.150, 0.183 and 0.502 than that of PLSR method, respectively. The PSO-SVR method had higher accuracy, with RPD being 20.8%, 10.0% and 2.7% higher than GRID-SVR for forest, cultivated land and orchard, respectively. The RPD of forest and orchard were 2.036 and 2.049, which well predicts soil organic carbon. The RPD of cultivated land was 1.647, which can make a rough estimate of soil organic carbon. The PSO-SVR model had the best prediction effect on soil organic carbon of different land use types, with the prediction accuracy of soil organic carbon content in forest and orchard being close and higher than cultivated land. Soil nutrition diffed acorss different land use types, which affect the prediction of soil organic carbon content. Models for inversion of soil organic carbon should be constructed separately for different land use types.

Responses of net assimilation rate to elevated atmospheric CO₂and temperature at different growth stages in a double rice cropping system

MA Ping, LI Ru-nan, WANG Bin, LI Yu-e, WAN Yun-fan, QIN Xiao-bo, LIU Shuo, GAO Qing-zhu

2020, 31(3):  872-882.  doi:10.13287/j.1001-9332.202003.029

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Effects of elevated atmospheric CO₂ concentration and temperature on rice dry matter accumulation vary in planting regions and cropping systems. It remains unclear how dry matter productivity responds to factorial combination of elevated CO₂ and temperature in the double rice cropping system of China. Field experiments were conducted using open-top chambers (OTC) to simulate different scenarios of elevated CO₂ and/or temperature for three rotations of double rice in Jingzhou, Hubei Province. Liangyou 287 and Xiangfengyou 9 were used as rice cultivar for early rice and late rice, respectively. There were five treatments: UC, paddy field without OTC covering; CK, OTC with the similar temperature and CO₂ concentration to field environment; ET, OTC with 2 ℃ temperature elevation; EC, OTC with 60 μmol·mol^-1 CO₂ elevation; ETEC, OTC with simu-ltaneous 2 ℃ temperature elevation and 60 μmol·mol^-1 CO₂ elevation. We measured aboveground biomass, leaf area index (LAI) and net assimilation rate (NAR) of dry matter under different treatments. Our results showed that elevated CO₂ and/or temperature had no significant effects on NAR from transplanting to jointing, increased NAR from jointing to heading, but decreased NAR from heading to maturity (except for EC treatment in early rice). Elevated CO₂ and/or temperature promoted leaf area development at all growth stages, with ETEC showing the highest increase in LAI except at maturity. Warming and CO₂ enrichment jointly promoted dry matter accumulation at heading, with ETEC increasing aboveground biomass by 10.3%-39.8% and 23.6%-34.4% compared with CK in early rice and late rice, respectively. At maturity of early rice, elevated temperature partly offset the positive effects of elevated CO₂ on aboveground biomass, as shown by a reduction of 3.2%-14.1% under ETEC compared with EC. Contrarily at maturity of late rice, co-elevation of CO₂ and temperature further increased aboveground biomass, showing a synergistic interaction. Results from regression analysis showed that warming and CO₂ enrichment had positive effects on NAR at vegetative stages of double rice, while warming showed negative effects on NAR at reproductive stages. Considering the dissimilarities in growth characteristics, growing periods and ambient temperature, elevated CO₂ and temperature might increase dry matter production in the Chinese double rice cropping system.

Effects of corn-based cropping systems on phosphorus fractions and availability in red soil

GOU Xiao-mei, WANG Chang-quan, LI Bing, CAI Yan, YE Xiang, YANG Fu, ZHOU Kun-xiang, ZHOU Xue-yu

2020, 31(3):  883-889.  doi:10.13287/j.1001-9332.202003.025

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To clarify the effects of corn-based cropping systems on phosphorus (P) fractions and availability in red soil, we measured P fractions and availability of topsoil (0-20 cm) and subsoil (20-40 cm) in abandoned farmland (control) and three corn-based cropping systems (corn continuous cropping, zucchini-corn rotation and pea-corn rotation), respectively. The results showed that total P, available P contents and P activation coefficient in topsoil were higher than those in subsoil. The value of relative P parameters in topsoil of pea-corn rotation was the highest among all cropping systems. Organic P was the main P fraction in red soil, accounting for 57.8%-81.1% (topsoil) and 74.3%-85.5% (subsoil) of total P. Except for pea-corn rotation soil, sodium hydroxide extractable P (NaOH-P) was the main P fraction in other cropping systems. The contents of water-soluble P (H₂O-P) and sodium bicarbonate extractable P (NaHCO₃-P) with high availability were lower than other P fractions, only accounting for 0.3%-2.1% (topsoil) and 1.7%-10.0% (subsoil) of total P. The pea-corn rotation soil had the highest hydrochloric acid extractable P (HCl-P) content in topsoil and subsoil, and significantly differed from other cropping systems. The contents of available P, sodium bicarbonate extractable organic P (NaHCO₃-P_o), sodium hydroxide extractable organic P (NaOH-P_o) and hydrochloric acid extractable inorganic P (HCl-P_i) were significantly correlated with pH, cation exchange capacity, iron-aluminum oxides and soil texture. In conclusion, pea-corn rotation was the most suitable system to improve P availability of red soil in Panxi area.

Effects of no-tillage, mulching, and organic fertilization on soil fungal community composition and diversity

WANG Xiao-ling, MA Kun, FU Yun-zhen, WANG Zhi-qin, AN Yuan-yuan

2020, 31(3):  890-898.  doi:10.13287/j.1001-9332.202003.039

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We examined the responses of soil fungal community to no-tillage, mulching, and organic fertilization by setting up different treatments for three years in winter wheat land in mountain areas of southern Ningxia, including no-tillage, mulching and organic fertilization (NF), no-tillage, mulching and no organic fertilization (NC), conventional tillage without mulching and organic fertilization (TF), and conventional tillage without mulching and no organic fertilization (TC). Based on Illumina Miseq high-throughput sequencing platform, the relationship between the composition and diversity of soil fungal community and soil environmental factors were examined. A total of 3490 fungal OTUs were obtained from four treatments, which included some unidentified or unknown fungi. In the identified ones, Ascomycota and Basidiomycota were the dominant phylum, contributing to 82.1%-94.2% of the total abundance. The relative abundance of Dothideomycetes from Ascomycota was the highest under TF, while that of Tremellomycetes from Basidiomycota was highest under NF. Both Shannon and Simpson indices of soil fungal community were in order of NC>TC>NF>TF. The results of multivariate analysis showed that soil microbial biomass carbon was the main factor affecting the relative abundance of Basidiomycota and Zygomycotabased at the phylum level, while soil total phosphorus, available potassium, and available phosphorus were key factors driving the changes of relative abundance of Ascomycota. Therefore, popularizing of conservation tillage based on the no-tillage, mulching and organic fertilization technology would be beneficial to the diversity of soil fungal community in mountainou areas of southern Ningxia.

Relationship of population quality and nitrogen fertilizer utilization characteristics of direct seeding rice under water-nitrogen interaction

WU Yun-xia, GUO Chang-chun, SUN Yong-jian, LIU Fang-yan, ZHANG Qiao, XIANG Kai-hong, SUN Yuan-yuan, MA Jun

2020, 31(3):  899-908.  doi:10.13287/j.1001-9332.202003.022

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Understanding population quality and nitrogen utilization characteristics of direct seeding rice under water-nitrogen interaction could provide theoretical and practical basis for high yield and ample production of direct seeding rice. Hybrid rice F You 498 was used as the material. Three irrigation methods were set in this study: flooding irrigation (W₁), dry-wet alternate irrigation (W₂) and drying irrigation (W₃), with different ratio of base fertilizer: tiller fertilizer: panicle fertilizer at 5:3:2 (N₁), 3:3:4 (N₂), 3:1:6 (N₃), respectively. No nitrogen application (N₀) was set as the control. We investigated the effects of water-nitrogen interaction on population quality and nitrogen utilization characteristics of direct seeding rice, with the aim to clarify the relationship between population quality construction, nitrogen utilization characteristics and yield of direct seeding rice. The results showed that irrigation and N rate significantly interacted to affect dry matter accumulation, rice harvest index, heading high-efficiency leaf (the upper three leaves) dry weight, light transmittance rate at maturity stage, total nitrogen accumulation (TNA), apparent nitrogen use efficiency (ANE), nitrogen partial factor productivity (NPFP), nitrogen physiology efficiency, and rice yield. Taking population quality, yield and N fertilizer utilization characteristics into consideration, suitable panicle N-fertilizer under each irrigation mode was 20%-40% (N₁-N₂). Panicle N-fertilizer reached 60% (N₃) and W₃ treatment would significantly reduce population quality, yield, nitrogen agronomy efficiency (NAE), NPFP of direct seeding rice. Yield and nitrogen utilization characteristics of direct seeding rice were significantly correlated with effective panicles, dry matter accumulation at maturity stage, other leaf (except the upper three leaves) dry weight reduction, total leaf dry weight reduction, and middle part and basel part light-receiving rate under water-nitrogen interaction. The dry-wet alternative (W₂) treatment could increase the rate of production til-lers, dry matter accumulation, rice harvest index, TNA, NAE and rice yield. W₂ combined with N₂ could improve population quality of direct seeding rice and realized the coordination and unification of high yield and efficient utilization of nitrogen, which is the best combination in this experiment.

Effects of water and nitrogen coupling on grain yield formation and nitrogen accumulation, transportation of oil flax in dryland

CUI Zheng-jun, LIU Dong, WU Bing, YAN Bin, MA Jun, ZHAO Bang-qing, GAO Yu-hong, NIU Jun-yi

2020, 31(3):  909-918.  doi:10.13287/j.1001-9332.202003.028

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A completely random split zone experiment with irrigation as main plots and nitrogen application rate as sub-plots was carried out to examine the optimal water-nitrogen coupling mode for oil flax planting in dryland. There were three irrigation levels, no irrigation (0 m³·hm^-2, I₀), irrigation at 1200 m³·hm^-2(I₁₂₀₀) and at 1800 m³·hm^-2(I₁₈₀₀); and three nitrogen application rates, no nitrogen (0 kg N·hm^-2, N₀), 60 kg·N hm^-2(N₆₀) and 120 kg·N hm^-2(N₁₂₀). We investigated nitrogen accumulation content at different growth stages, nitrogen transport characteristics after anthesis, grain yield and nitrogen utilization efficiency of oil flax. Results showed that the coupling effects of water and nitrogen application on nitrogen uptake in different organs, nitrogen accumulation during different growth stages and grain yield of dry land oil flax varied greatly. Under no irrigation, nitrogen application was beneficial to stem nitrogen absorption at anthesis and maturity stages, but 120 kg N·hm^-2 inhibited it at different irrigation levels. At the 1200 m³·hm^-2(I₁₂₀₀) irrigation level, foliar nitrogen content at anthesis stage increased first and then decreased with increasing nitrogen rates, and N₆₀ increased foliar nitrogen content by 11.0% and 28.9% respectively compared with N₀ and N₁₂₀. At the 1800 m³·hm^-2(I₁₈₀₀) irrigation level, nitrogen application increased foliar nitrogen content at maturity stage, with that in N₆₀ and N₁₂₀ treatments being 39.7% and 26.9% higher than N₀, respectively. The effects of water-nitrogen coupling on nitrogen accumulation in different growth stages of oil flax was mainly shown after budding stage. Under the same irrigation level, N₆₀ promoted and N₁₂₀ inhibited nitrogen accumulation in each stage after budding. Nitrogen application increased nitrogen transport rate and contribution rate of leaves and stems under I₁₂₀₀ and I₁₈₀₀. The coupling of I₁₈₀₀ and N₆₀ significantly increased the number of effective capsules per plant and grain yield of oil flax (6.6%-22.8%), which was a suitable water-nitrogen coupling management mode in this area.

Effects of seeding pattern and phosphorus application on population structure, photosynthe-tic characteristics and yield of winter wheat

LIU Chong, JIA Yong-hong, ZHANG Jin-shan, SUN Peng, LUO Si-wei, WANG Huan, LI Peng, SHI Shu-bing

2020, 31(3):  919-928.  doi:10.13287/j.1001-9332.202003.009

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Under Xinjiang winter wheat seeding pattern, in order to sort out proper phosphorus application (PA) and find out the effects and mechanism of PA on population structure, photosynthesis characteristics and yield and provide reliable evidence for PA management of winter wheat, we arranged a two-factor complete split-plot design of wheat variety “Xindong 22”. The main area consisted of two seeding ways: drill seeding pattern (D) and uniform seeding pattern (U), while in the sub-area there were four levels of PA(P₂O₅): 0, 60, 120, and 180 kg·hm^-2(represented by P₀, P₆₀, P₁₂₀ and P₁₈₀ for those treatments, respectively). The results showed that the earbearing percentage in U was 15.9% higher than that in D, and the other features (PAR interception rate, extinction coefficient, leaf area index, SPAD and photosynthetic parameters) were more optimal in 120 kg·hm^-2 treatment. Our results showed that the 120 kg·hm^-2 treatment in U would be the optimal option with respect to population structure, photosynthetic characteristics, and yield.

Effects of organic fertilizer on soil environment and yield of tomato under year-round cultivation

LIU Zhong-liang, GAO Jun-jie, GU Duan-yin, YAN Wei-qiang

2020, 31(3):  929-934.  doi:10.13287/j.1001-9332.202003.021

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The early-spring and autumn-winter tomato in greenhouse is the main planting patterns of protected vegetable in North China. Taking the customary fertilization amount of farmers under this planting pattern as control (CK, 100% chemical fertilizer), six organic fertilizer replacing chemical fertilizer treatments were set, namely, 15% (T₁), 30% (T₂), 45% (T₃), 60% (T₄), 75% (T₅), 100% organic fertilizer (T₆), to examine the replacing effects on soil environment and tomato yield. The results showed that soil bacteria increased with increasing organic fertilizer amount, the actinomycetes wers up to 12.12×10⁶ cfu·g^-1 under T₁ treatment which was the highest one. Combined application of organic fertilizer could increase soil urease activity, decrease catalase activity, increase soil organic matter, and enhance the concentrations of available phosphorus and available potassium, indicating that organic fertilizer had significant effects on soil physical and chemical properties, soil enzyme activity and nutrient accumulation. The invertase activity and available phosphorus content under T₁ treatment were the highest, being 1.36 mg·g^-1 and 305.4 mg·kg^-1, respectively, while the available potassium content of T₂ treatment was the highest (582.6 g·kg^-1). In addition, T₂ had the largest percentage of >0.25 mm water-stable agglomerate (94.2%). Compared with CK, the application of organic fertilizer could improve tomato quality and increase yield. The lycopene content of T₁ was the highest (5.69), the sugar-acid ratio of T₁ and T₂ was 8.19 and 8.70, respectively, with better tastes. The yield of T₁ was the highest, followed by T₂ treatment, which was 16.6% and 5.8% higher than that of CK, respectively. It suggested that reducing the application rate of chemical fertilizers by 15%-30% with organic fertilizer was a preferred fertilization measure in this planting pattern.

Effects of nitrogen management on soil microbial community structure at different growth stages under straw returning in paddy soils

WANG Qing-xia, LI Mei-lin, CHEN Xi-jing, SU Yao, YU Man, SHEN A-lin

2020, 31(3):  935-944.  doi:10.13287/j.1001-9332.202003.027

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Effects of different nitrogen application methods on microbial community structure of paddy soil at different rice growth stages were examined using phospholipid fatty acid analysis (PLFA) and Biolog technique. There were four treatments, no straw returning or fertilization (CK), straw returning +urea with the proportions of after wheat harvest, before rice transplanting, tillering stage and booting stage being 0:6:2:2 (T₁) and 3:3:2:2 (T₂), and straw returning+co-application of biogas slurry and urea with the proportion of after wheat harvest, before rice transplanting, tillering stage and booting stage being 3 (biogas slurry):3 (2biogas slurry+1urea):2 (urea):2 (urea)(T₃). Results showed that T₃ significantly increased soil available nitrogen contents at all growth stages, which was significantly higher at maturity stage than that at tillering and booting stages. T₁-T₃ had higher available phosphorus and available potassium contents at all growth stages compared with CK, which were higher at tillering stage than at booting and maturity stages. The interaction between growth stage and treatment in paddy soil significantly affected the contents of soil available nitrogen, available phosphorus and available potassium. Furthermore, carbohydrate, amino acid, polymer and carboxylic acid were the primary carbon sources for microbial community of paddy soil. T₃ effectively enhanced soil carbon sources metabolic utilization intensity. The interaction between growth stage and treatment in paddy soil significantly affected the microbial utilization capacity of carbohydrates and carboxylic acids. Soil microbial biomass was significantly higher in T₂ and T₃ treatments. Moreover, T₂ had high fungi/bacteria (F/B) value, indicating that fungi could benefit the stabilization of paddy soil. In summary, simultaneous nitrogen application (urea or biogas slurry) and straw returning could increase soil microbial activity and improve soil environment in paddy field.

Development of critical nitrogen dilution curve based on leaf dry matter for maize under drip irrigation

FU Jiang-peng, JIA Biao, YANG Wen-wei, WEI Xue, MA Cheng, LIU Gen-hong, WANG Rui, SUN Quan

2020, 31(3):  945-952.  doi:10.13287/j.1001-9332.202003.030

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To provide a theoretical reference to nitrogen fertilizer management for maize and eco-enviromental protection in the irrigated area of Ningxia, we established the critical nitrogen concentration (N_c) dilution curve of maize under drip-irrigated condition. The nitrogen nutrition index (NNI) was deduced from the established N_c curve model, to diagnose feasibility of nitrogen nutrition. Six levels of nitrogen application rates including 0, 90, 180, 270, 360 and 450 kg·hm^-2 were conducted in field with maize variety ‘Tianci 19’. During two-year field study, the N_c dilution curve and NNI model of maize were established based on leaf dry matter (LDM). The results showed that: 1) There was a negative power function relationship between LDM and N_c, which presented as two parts, if LDM<1.15 t·hm^-2, N_c=3.2%, while if LDM≥1.15 t·hm^-2, N_c=3.29LDM^-0.29. 2) The root mean square error (RMSE) and standardized root mean square error (n-RMSE) of the model were 0.203 and 8.0%, respectively, with fine stability among years. 3) The NNI ranged from 0.47 to 1.44 with different nitrogen application rates. In addition, NNI was positively correlated with yield and negatively correlated with agronomic utilization efficiency of nitrogen fertilizer at different growth stages of maize. Therefore, NNI could be used to explain maize yield changes with and without nitrogen limit under drip-irrigated system. In conclusion, the critical nitrogen dilution curve established from leaf dry matter could be applied to accurately estimate nitrogen nutrition status throughout the whole growing stages from the jointing stage to silking stage of maize under drip irrigated system.

Effects of foliar selenium fertilizer on fruit yield, quality and selenium content of three varieties of Vitis vinifera

YIN Ning, MU Lan, LIANG Yin-li, HAO Wang-lin, YIN Hong-fei, ZHU Shuai-meng, AN Xiao-juan

2020, 31(3):  953-958.  doi:10.13287/j.1001-9332.202003.007

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With three grape varieties, Red Barbara, Summer Black and Hutai No. 8 as test mate-rials, we investigated the effects of foliar spraying of organic selenium fertilizer on greenhouse grape quality and selenium content. The results showed that spraying 12 mg·L^-1 amino acid chelated selenium-enriched foliar fertilizer on grape leaves significantly increased selenium content and the quantity and quality of grape yield, including the contents of soluble sugar, organic acid, soluble protein, soluble solids, vitamin C and proanthocyanidins. However, there was no increase in resveratrol. Among the three varieties, selenium content of Summer Black in 2017 and 2018 was increased by 36.7% and 37.1%, respectively, being higher than that of Red Barbara and Hutai No. 8. Red Barbara sprayed with selenium fertilizer had better quality due to high sugar and low acid contents, as well as high health-care components. Moreover, the selenium content of Hutai No. 8 in 2018 was 53.26 μg·kg^-1, higher than the others, indicating a stronger ability of selenium enrichment. We concluded that the increase range of Se content was larger in Summer Black, Red Barbara showed the better nutrition value and quality, and Hutai No. 8 was a suitable variety for selenium-rich grape production.

Phospholipase Dα1 and hydrogen sulfide were involved in the allelopathy of oridonin to Arabidopsis thaliana

ZHAO Qi-an, LIU Bo, ZHANG Yue, LIU Qin, ZHANG Li-huan, LIU Rui-fang, YANG Ning

2020, 31(3):  959-968.  doi:10.13287/j.1001-9332.202003.035

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We investigated the signal relationship between phospholipase Dα1 (PLDα1) and the gas signal molecule hydrogen sulfide (H₂S) in Arabidopsis thaliana response to the allelopathy of diterpenoid oridonin. The wild type Arabidopsis Columbia (WT), phospholipase Dα1 (PLDα1) deletion mutant pldα1, D-/L-cysteine desulfyrase synthetic deletion mutant d-cdes and l-cdes seedlings were used as experiment materials, while 60 μmol·L^-1 oridonin was applied as treatment concentration. The results showed that oridonin significantly increased H₂S content, PLD and D-/L-CDes activities, and gene expressions of PLDα1 and D-/L-CDes in WT. Under oridonin treatment, the D-CDes and L-CDes activities of pldɑ1 seedlings were significantly lower than those of WT. Both D-CDes and L-CDes activities increased after exogenous addition of phosphatidic acid (PA) and were higher than those of WT. Oridonin significantly inhibited root growth of four lines, with d-cdes and l-cdes being more sensitive to oridonin. Application of NaHS promoted root growth and endogenous H₂S production of four lines under oridonin treatment, while application of PA increased root growth and endogenous H₂S production in WT, pldɑ1 and l-cdes, but had no effect in d-cdes. These results indicated that PLDα1 and H₂S played a vital role in driving the response of Arabidopsis to oridonin, and that PLDα1/PA was located at the upstream of D-CDes to participate the regulation of the H₂S production and root growth.

Physiological responses of symbiotic rhizobium pea to exogenous calcium under salt stress

MA Shao-ying, MA Lei, XU Bo, YANG Ning, ZHANG Xu-hui, CHAI Qiang, LI Sheng

2020, 31(3):  969-977.  doi:10.13287/j.1001-9332.202003.010

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To clarify the effects of exogenous calcium on salt tolerance of nodule symbiotic pea, a pot experiment was conducted under salt stress (170 mmol·L^-1) to examine the effects of exogenous CaCl₂(0, 5 and 15 mmol·L^-1) on physiological parameters of two pea cultivars, ‘Dingwan 8’ (salt tolerant) and ‘Longwan 6’ (salt sensitive), inoculated with rhizobium strains 15657, 15735 and Ca66. The results showed that plant biomass, the activities of superoxide dismutase (SOD) and peroxidase (POD), and the contents of proline (Pro) and soluble sugar (SS) were enhanced, but malondialdehyde (MDA) content was decreased, with rhizobium inoculation, CaCl₂ application or CaCl₂ application after rhizobium inoculation. Plant biomass and activities of SOD and POD and Pro content were increased significantly by the application of 15 mmol·L^-1 CaCl₂ after rhizobium inoculation. The application of CaCl₂ after inoculation of rhizobium strain 15735 suitable for pea had limited effects on physiological parameters of pea plants, whereas the application of CaCl₂ after inoculation of rhizobium (15657, Ca66) unsuitable for pea had obvious effects. The comprehensive analysis of membership function showed that pea treated with CaCl₂ after rhizobium inoculation exhibited stronger salt tolerance, and ‘Dingwan 8’ plants treated with 15 mmol·L^-1 CaCl₂ after inoculation of rhizobium strain 15735 showed the strongest ability of salt tolerance with the highest membership function value of 0.814. In summary, compared with CaCl₂ application or rhizobium inoculation alone, CaCl₂ application after rhizobium inoculation could effectively enhance the activities of antioxidant enzymes and osmotic regulation ability, reduce the damage of membrane lipid peroxidation, and consequently improve the salt tolerance of pea.

Relationships among different types of ecosystem service in Southwest China

LIN Zi-yan, XIAO Yi, RAO En-ming, SHI Xue-wei, ZHANG Ping

2020, 31(3):  978-986.  doi:10.13287/j.1001-9332.202003.015

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Understanding the relationships among different ecosystem services is the basis for optimizing ecological protection strategy and achieving sustainable ecological management. Based on the ecosystem services and their spatial patterns in Southwest China, we analyzed tradeoffs and synergies of five ecosystem regulation services (water retention, soil retention, carbon sequestration, biodiversity conservation, and water purification) and five provision services (rice production, wheat production, corn production, vegetable production, and fruit production) using statistical analysis, ArcGIS technology and GeoDa software. Further, we identified the win-win areas of ecosystem servi-ces through overlay analysis, and discussing the influence of ecosystem types on win-win pattern. There were synergistic relationships among different types of regulation or provision services in Southwest China, while there were both synergies and trade-offs between regulation and provision services. The high win-win areas of the total ecosystem services in Southwest China were mainly distributed in Qionglai Mountains, Ailao Mountains, Dayao Mountains, as well as Lujiang River and Lancang River basins. The proportion of forest and farmland areas significantly affected all kinds of win-win trend.

Spatial-temporal evolution of ecological land and influence factors in Wuhan urban agglome-ration based on geographically weighted regression model

LIU Yan-wen, LIU Cheng-wu, HE Zong-yi, ZHOU Xia, HAN Bing-hua, HAO Han-zhou

2020, 31(3):  987-998.  doi:10.13287/j.1001-9332.202003.016

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Ecological land is essential to sustainable development of urban agglomeration. Based on the results of remote sensing image interpretation, we analyzed the spatial-temporal evolution of ecological land in 32 research units of ecological land in Wuhan urban agglomeration in 2000-2005, 2005-2010 and 2010-2015, using the land use transition matrix, exploratory regression analysis, the ordinary least squares (OLS) model, and geographically weighted regression (GWR) model. Then, the best regression model was selected after perfecting the traditional index system of influencing factors by data of the location and quantitative information of companies, enterprises and life services, etc., and conducting exploratory regression analysis. Finally, we analyzed the influencing factors and spatial differentiation rules of different research periods with GWR model. The results showed that, from 2000 to 2015, the amount of transition from ecological land use to non-ecological land use in the urban agglomeration showed an inverted U-shaped change pattern, and the space showing the expanding trend from point to surface. Land use patterns of 8.4% area had changed in the urban agglomeration, among which the conversion of cultivated land, forest land, grassland, water body and unused land to non-ecological land accounted for 41.9% of the total area. The spatial pattern gradually expanded from the central urban area of Wuhan to the periphery of the municipal sub-center and county-level towns. The total number of passing models in the three stages of exploratory regression analysis was 326. The GWR and OLS regression were used for comparative analysis of all models. The adjusted R² in the three stages of selected models were 0.83, 0.91 and 0.76, respectively. The former improved by 0.02, 0.03 and 0.02, and the AICc decreased by 2.88, 3.42 and 0.83, respectively. The results of GWR model showed substantially spatial differentiation of influencing factors of ecological land evolution in Wuhan urban agglomeration, and that the influence patterns was dominated by gradual transition in different directions in space, with other patterns such as “V” distribution. The effects of spatial factors were significant. The potential information of spatial data enhanced the interpretation of ecological land evolution within the urban agglomeration.

Heavy metal pollution and comprehensive ecological risk assessment of surface soil in diffe-rent functional areas of Shenzhen, China

CHANG Wen-jing, LI Zhi-jian, ZHOU Yan-zi, ZENG Hui

2020, 31(3):  999-1007.  doi:10.13287/j.1001-9332.202003.036

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To explore the impact of urban functional zones on surface soil metal pollution, we analyzed the concentrations and pollution status of eight heavy metals (i.e., Mn, Ni, Cr, Pb, Cd, Zn, Cu, and As) in surface soils from various urban functional zones of Shenzhen City. Nemero index and potential ecological hazard indices were used to quantify the ecological risk levels of different heavy metals in different urban functional zones. Moreover, we spatially classified ecological risk zones for soil heavy metal pollution. Results showed that: 1) concentrations of Cd, Zn, Cu, and As in the surface soil were heavily impacted by human activities, while those of Mn, Ni, Cr, and Pb were not. High-intensity urbanization and industrialization with the constraints of physical environment were identified as the determining factors for regional and functional variation of heavy metal pollution. 2) Pb, Cd, Zn, and Cu had high pollution risks in the surface soils, with Pb having the highest risk, which necessitated further management and control of heavy metals. The overall level of heavy metal pollution risk in the surface soils of Shenzhen was higher than that of other cities in China. 3) Nemero index and potential ecological hazard indices had different emphases in terms of assessing the risk level of heavy metals. Those indices showed different performances in the risk assessment of single heavy metal, overall ecological risks in the different urban functional zones, and ecological risk classification of heavy metal pollution in the urban surface soils. We suggest that those indices should be combined to provide more holistic information about urban heavy metal pollution.

Spatial pattern in larval distribution, settlement and growth of Crassostrea sikamea in Xiangshan Bay, Zhejiang Province, China

JIANG Wei, WANG Tao-ni, CHEN Shai, SUN Zhao-yue, FAN Rui-liang, LI Nan-nan, LI Xue-ying, QUAN Wei-min

2020, 31(3):  1008-1014.  doi:10.13287/j.1001-9332.202003.038

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The migration and settlement of oyster larvae significantly affect the distribution, recruitment, establishment and ecological services of oyster populations. We investigated the variations of Crassostrea sikamea larvae abundances between the two water layers and between the two experimental sites (seed bed and spawning bed) in Xiangshan Bay within a tidal cycle (9 sampling times), and explored the spatial patterns in larval settlement and spat growth at three intertidal zones (top, T; middle, M and bottom, B) of both experimental sites by a field settlement experiment. At the seed bed and spawning bed, oyster larvae abundance at the surface water significantly changed with sampling time. At the seed bed, oyster larvae abundance (20.8±5.6 larvae·L^-1) was greatest at the high flood tide, and was significantly greater than that at the other eight sampling times. Contrasting results were found at the spawning bed where oyster larvae abundance was the lowest (0.1±0.1 larvae·L^-1) at the high flood tide. At each site, oyster larvae abundance at the bottom water did not change within the tidal cycle. At the seed bed, total abundance, survival rate and shell height of the settled oysters significantly varied across intertidal zones, ranking as B>T=M for total oyster abundance, and T>M>B for survival rate and shell height. There was no significant difference in live spat abundance among intertidal zones. At the spawning bed, the total and live abundances, survival rate and shell height of the settled oysters had no difference among intertidal zones. Our results indicate that oyster larvae commonly settle at the high flood tide, and the abundance of settled spats are similar between seed bed and spawning bed.

Spatial-temporal variation in hotspot and coldspot of Antarctic krill distribution in recent 100 years

LIU Hui, ZHU Guo-ping

2020, 31(3):  1015-1022.  doi:10.13287/j.1001-9332.202003.019

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To analyze the long-term variation in the spatial-temporal patterns of Antarctic krill (Euphausia superba) distribution, based on krill density data collected from 1926 to 2016, we analyzed the spatial and temporal variation of krill using the Getis-Ord G_i^* statistic and the Triangulated Irregular Network (TIN) model. We compared the krill abundance, the percentage of krill abundance, and the size of hotspot/coldspot area. The results showed that there were one core hot-spot area, one sub-hotspot area and one edge hotspot area from 1926 to 1935 and from 1936 to 1945; one core hotspot area, one sub-hotspot area and one edge hotspot/coldspot area from 1976 to 1985; two core hotspot areas, two sub-hotspot areas, two edge hotspot areas, one sub-coldspot area and one coldspot area from 1986 to 1995; two core hotspot areas, two sub-hotspot/sub-coldspot areas and two edge hotspot/coldspot areas from 1996 to 2005; and from 2006 to 2016, there were two sub-hotspot areas, two edge hotspot areas, one sub-coldspot area and one edge coldspot area, respectively. Those hotspots/coldspots mostly occurred in the South Sandwich Islands, the Antarctic Peninsula, and the west of the Prydz Bay. From 1926 to 2016, krill abundance, the percentage of krill abundance in the hotspot area and the size of hotspot area had generally reduced, but the percentage of krill abundance in coldspot area and the size of coldspot area were increasing, while krill abundance in coldspot area decreased. It is a feasible approach to build an irregular triangle network to measure the size of hotspot/coldspot area and utilize hotspot analysis with 95% confidence to analyze the spatial-temporal pattern of krill distribution.

Spatial distribution and inter-annual variability of spawning grounds of Cynoglossus joyneri in the Yellow Sea coastal waters in summer

WAN Rong, ZHANG Tong-zheng, LI Zeng-guang, REN Yi-ping, SONG Peng-bo

2020, 31(3):  1023-1032.  doi:10.13287/j.1001-9332.202003.034

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With survey data from three voyages in the summer of 2014, 2016, and 2017, spatial distribution and inter-annual variability of spawning grounds of Cynoglossus joyneri in the coastal waters of Yellow Sea were examined based on Tweedie-generalized additive model (GAM). The results showed that the spawning grounds of C. joyneri mainly distributed in the Haizhou Bay ranging within 34°00′-35°18′ N, 119°30′-121°30′ E. The other one in Subei Shoal 32°18′-34°00′ N, 120°18′-122°00′ E. Fish eggs of C. joyneri were few in the southern waters of Shandong Peninsula 34°42′-36°48′ N, 119°30′-122°00′ E. The distribution of fish eggs was significantly related to the location (i.e., longitude and latitude), depth, and sea surface temperature, and did not relate to the sea surface salinity and surface chlorophyll a. The optimal range of depth, sea surface temperature, sea surface salinity, and surface chlorophyll a were 15-26 m, 29-32 ℃, 22-25 and 0.10-3 mg·m^-3, respectively. There was notable inter-annual variability in the spatial distribution of spawning grounds of C. joyneri and its influencing factors. Overall, the distribution of spawning grounds is relatively stable, but potentially move northward in the year with high sea surface temperature.

Reviews

Characteristics of soil nitrogen cycle and mechanisms underlying the increase in rice yield with partial substitution of mineral fertilizers with organic manure in a paddy ecosystem: A review

CHEN Xiang-bi, HU Ya-jun, QIN Hong-ling, ZHANG Xiao-fang, SU Yi-rong, LI Hui-xin

2020, 31(3):  1033-1042.  doi:10.13287/j.1001-9332.202003.006

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Partial substitution of mineral fertilizers with organic manure is a key strategy for stable and increase crop yield accompanying with zero growth of mineral fertilizers. Based on recent stu-dies, we reviewed the effects of partial substitution of mineral fertilizers with organic manure on rice yield, nitrogen utilization efficiency, soil nitrogen fractions, and microbial nitrogen fixation, ammonification, nitrification, and denitrification in rice paddy ecosystems. We further compared the cha-racteristics of soil nitrogen cycle of mineral fertilizers alone and partial substitution of mineral fertili-zers with organic manure. The partial substitution altered key processes of nitrogen cycling, including enhancement of ammonification, mediation of nitrification and denitrification, reduction of ammonia volatilization and nitrogen loss, improved the status of nitrogen supplements (enriching the supplement of low-molecular-weight organic nitrogen, adjusting the distribution of inorganic nitrogen components, increasing the amount of microbial biomass nitrogen, and decreasing the loss of total nitrogen), improved soil nitrogen supply (increasing supply of small molecule organic nitrogen, coordinating inorganic nitrogen components and proportions, and increasing soil microbial biomass nitrogen and total nitrogen fixation), which promoted nitrogen uptake and regulated nitrogen allocation in rice plant to realize stability and enhancement of rice yield.

Maintaining mechanisms of riparian invertebrate biodiversity: A review

WANG Ke-hong, YUAN Xing-zhong, ZHANG Guan-xiong, WU Shuai-kai, LIU Shuang-shuang, ZHANG Meng-jie

2020, 31(3):  1043-1054.  doi:10.13287/j.1001-9332.202003.032

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Riparian zones, the critical ecological interfaces between terrestrial and aquatic ecosystems, are species rich habitats. However, riparian zones are seriously threatened by human activities in the world. Riparian invertebrates represent a large proportion of riparian biodiversity, perform various ecological functions, and provide an essential link between aquatic and terrestrial ecosystems. Although many studies have investigated the riparian invertebrate communities, there is lacking a comprehensive summary of maintaining mechanisms underlying riparian invertebrate diversity. This review discussed seven characteristics of riparian zones that might support high riparian invertebrate diversity: flood and drought, nutrient, microhabitat diversity, riparian vegetation, microclimate gradients, food resources and river spatial gradients. Further, we summarized the maintaining mechanisms of riparian invertebrate diversity. Disturbances of periodic flood and drought trigger the reproduction and migration of invertebrates, increase the turnover of invertebrate communities, and create suitable conditions for riparian invertebrates. Adequate nutrients support a high invertebrate diversity by increasing primary productivity of riparian habitats. Elevated microhabitat diversity provides a variety of niche space for specialist riparian invertebrates. Strong microclimate gradients provide complex and diverse habitats and thus facilitate the coexistence of aquatic and terrestrial invertebrates in riparian zones. Cross-ecosystem resource subsidies increase food availability and contribute unique food sources to riparian invertebrates. The differentiation of these factors along river longitudinal and lateral gradients provides conditions for the diversification of riparian invertebrates at a larger scale. Understanding the maintaining mechanisms of riparian invertebrate diversity is important for conservation of riparian biodiversity and integrated management of river ecosystems.