Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources
Not a member yet
7916 research outputs found
Sort by
Beta diversity diminishes in a chronosequence of desertification in a desert steppe
No full textBiodiversity is a central and multifaceted concept of community ecology, but a major challenge remains in understanding the variation mechanisms of biodiversity. Two ecological phenomena are shown in beta diversity: (a) spatial species turnover in space and (b) nestedness-resultant of assemblages. Using a field experiment focusing on a desert steppe ecosystem, we show that desertification influences those two components in divergent ways depending on whether a deterministic or stochastic process is driving community composition. Desertification was a major driver of local environmental heterogeneity, which also resulted in decreased soil nutrients and led to increased turnover in a heterogeneous environment; however, spatial turnover of species decreased with desertification intensify. Desertification decreases resource availability, which causes species loss and reduced total beta diversity. Those desertification effects, therefore, had a homogenizing effect on the community. However, stochastic processes cannot be disregarded as a factor in community composition determination. Overall, these results indicated that the study of desertification effects on beta diversity would add our knowledge of the deterministic and stochastic processes that create and maintain biodiversity. This is crucial to assess the relative importance between stochastic processes and deterministic processes
COMPETITIVE INTERACTION BETWEEN MIXED-PLANTING MAIZE CULTIVARS ENHANCED YIELD AND WATER-USE EFFICIENCY IN A SEMI-ARID REGION
No full textEffects of competitive interaction between two mixed planting maize (Zea mays L.) cultivars on yield and water use efficiency are inevitable and the positive process needs more excavation. Two maize cultivars were mixed planting in two densities to explicit the potential of competitive interaction improving yield and water use efficiency in a semi-arid region over two growing seasons. During grain filling stage firstly, competitive interaction optimized stem to leaf ratio of two maize cultivars, and decreased root to shoot ratio at harvest under the same-high mixed planting density, great competitive intensity caused by high planting density suppressed vegetative growth of maize. Secondly, land equivalent ratio positively increased from 1.02 to 1.14, which signified the advantage of farming land use. Furthermore, positive values of total actual yield loss in the four mixed systems indicated a yield advantage. Over two years, mean yield and water use efficiency increased by 6.5 % and 11.7 % which resulted from the positive performance of two maize cultivars in the mixed systems. Thus, consequences of competitive interaction in the mixed planting systems performed as land use, maize yield and water use efficiency advantages in the dry land farming
Modern hexaploid wheat differs from diploid and tetraploid ancestors in the importance of stress tolerance versus stress avoidance
No full textCombined high temperature and weak radiation stress negatively influences wheat production. However, related eco-physiological mechanisms across wheat species of different genetic backgrounds are not well documented. A pot-culture experiment was conducted in growth chambers to analyse the prevailing strategies of wheat genotypes with different ploidy levels under combined high temperature and weak radiation (30 degrees C-25 degrees C, 200 mu molm(-2) s(-1) photosynthetically active radiation (PAR)) stress compared with normal growth conditions (20 degrees C-15 degrees C; 400 mu molm(-2) s(-1) PAR). The diploid and tetraploid wheat genotypes showed better avoidance ability to high temperature and weak radiation stress than the hexaploids. These diploids and tetraploids produced high vegetative biomass under control conditions but this was reduced substantially under the stress. The adaptive response to avoid the stress was a strong reduction in vegetative organs, mainly leaf area. Consequently, these genotypes produced lower yields. By contrast, modern hexaploid wheat varieties displayed a stronger tolerance to the stress and produced higher yields through greater green leaf area, higher relative leaf water content, and higher proline and soluble sugar contents. The relative importance of these tolerance and avoidance strategies was estimated to account for 60% and 22%, respectively, of the variations in grain yield. Our study demonstrated that modern hexaploid wheat has acquired a greater proportion of tolerance rather than avoidance strategy in response to high temperature and weak radiation stress
Responses of soil microbial communities to nutrient limitation in the desert-grassland ecological transition zone
No full textSoil microorganisms are crucial to indicate ecosystem functions of terrestrial ecosystems. However, the responses of microbial communities to soil nutrient limitation in desert-grassland are still poorly understood. Hence, we investigated soil microbial community structures and metabolic characteristics in a desert-grassland ecological transition zone from the northern Loess Plateau, China, and explored the association of microbial communities with nutrient limitation via high-throughput sequencing.Threshold elemental ratios (TER) indicated that the microbial communities were strongly limited by nitrogen (N) under A. ordosica and P. tabuliformis communities. The phosphorus (P) limitation of microbial communities was observed in the aeolian sandy soil. The results imply that soil microbial communities had strong nutrient competition for N and P with aboveground vegetation in arid and oligotrophic ecosystems. The LEfSe and linear regression analysis revealed that the microbial taxa of Micrococcales, Micrococcaceae and Herpotrichiellaceae were significantly correlated with microbial N limitation. The Thermoleophilia taxa were significantly correlated with microbial P limitation. These biomarkers related to microbial nutrient limitation could be considered as the key microbial taxa to shape microbial communities and functions. Furthermore. N form had different effects on microbial communities, which NH4+-N strongly affected bacterial communities, whereas NO3--N had a significant influence on fungal communities. The different responses indicate that soil microorganisms had corresponding nutrient preferences for bacterial and fungal communities, which might alleviate the nutrient limitations and environmental stress. This study provided important insights on microbial community structures linking to community functions and on the mechanisms governing microbial N and P limitation in arid land ecosystems. (C) 2018 Elsevier B.V. All rights reserved
Development of pedotransfer functions for soil hydraulic properties in the critical zone on the Loess Plateau, China
No full textSoil hydraulic properties (SHPs) including the soil water retention curve and saturated soil hydraulic conductivity (Ks) are crucial input data for simulations of soil water and solute transport in the Earth's critical zone. However, obtaining direct measurements of SHPs at a wide range of scales is time consuming and expensive. Pedotransfer functions (PTFs) are employed as an alternative method for indirectly estimating these parameters based on readily measured soil properties. However, PTFs for SHPs for the deep soil layer in the Earth's critical zone are lacking. In this study, we developed new PTFs in the deep soil profile for Ks and soil water retention curve on the Loess Plateau, China, which were fitted with the van Genuchten equation. In total, 206 data sets comprising the hydraulic and basic soil properties were obtained from three typical sites. Samples were collected from the top of the soil profile to the bedrock by soil core drilling. PTFs were developed between the SHPs and basic soil properties using stepwise multiple linear regression. The PTFs obtained the best predictions for Ks (R-adj(2)=0.561) and the worst for van Genuchten (R-adj(2)=0.474). The bulk density and sand content were important input variables for predicting Ks, , and s, and bulk density, clay content, and soil organic carbon were important for n. The PTFs developed in this study performed better than existing PTFs. This study contains the first set of PTFs of SHPs to be developed for the deep profile on the Loess Plateau, and they may be applicable to other regions
Sustainability of Abandoned Slopes in the Hill and Gully Loess Plateau Region Considering Deep Soil Water
No full textSoil desiccation of the deep soil layer is considered one of the main limiting factors to achieving sustainable development of ecosystems in the hill and gully Loess Plateau region. In this study, slope croplands were selected as the control, and deep soil water was studied on abandoned slopes, including natural abandoned slopes, Robinia pseudoacacia plantations, and Caragana korshinskii plantations. Then, we explored deep soil water characteristics of different vegetation types and slope aspects and the variation tendencies of deep soil water at different recovery stages. The results showed that there were no significant differences in deep soil water content between sunny and shady slopes, and thus, slope aspect was not the key impact factor affecting deep soil water. Deep soil water content on R. pseudoacacia plantations and C. korshinskii plantations was lower than that on natural abandoned slopes; there were no significant differences in soil water content between the natural abandoned slopes and slope croplands. Soil desiccation did not exist on natural abandoned slopes; thus, natural vegetation restoration is an appropriate way to achieve a sustainable ecosystem with respect to deep soil water. In contrast, soil desiccation intensified until it was difficult for vegetation to obtain available water in the deep soil layer on the plantations; soil desiccation began to appear at the 11-20-year stage, and it became increasingly severe until the deep soil water was close to the wilting coefficient at the >= 30-year stage on R. pseudoacacia plantations. Deep soil water was rapidly consumed, and soil desiccation began to appear at the 1-10-year stage and then was close to the wilting coefficient in the later stages on C. korshinskii plantations. According to the results, the plantations needed to be managed in a timely manner to prevent or reduce soil desiccation
Numerical experiments on stagnation points influenced by the Three Gorges Dam in the Yangtze Estuary
No full textIn order to study the changes of stagnation points in the Yangtze Estuary influenced by the Three Gorges Dam operation, 3-D hydrodynamic and sediment transport model ECOMSED was used to simulate the dynamic process of flow varying with the river discharge and tide of the Yangtze Estuary. The results show that the location of stagnation points varied markedly in different areas after the impoundment of the Three Gorges Dam, with the large extent of downward movement during flood periods due to the hydrodynamic enhancement of the Yangtze River in the North Branch, while the movement range was smaller in the South Branch. Along with the runoff changes, the variation extent from big to small is North Channel, South Passage and North Passage, while the rank order changed as South Passage, North Channel and North Passage as valued by the tidal changes. After the impoundment of the Three Gorges Dam, the movement range of stagnation points reduced because of the reduction in river discharge. Thus, it can be considered that the turbidity maximum zone has a decreasing trend which might lead to changes in geomorphic features of the Yangtze Estuary
Rainfall variation prediction using SD technology based on temperature model for Weihe River basin
No full textGlobal warming has exerted a significant influence on the water cycle in global drainage basins, involving various aspects associated with ecology, society, economy and human activity. Therefore, accurate forecast and analysis of climatic change trends are the prerequisite to disaster alleviation and prevention. This paper selects a large-scale climate predictor by modeling steps and evaluation indicators for a statistical downscaling (SD) model and establishes a statistical relation between atmospheric circulation factor and precipitation and air temperature at eight stations in Wei River basin in Shaanxi Province for a global climate model output based on hydrological data for Wei River basin in Shaanxi Province. A study was made of the simulated precipitation and air temperature in Wei River basin by principal component analysis and multiple linear regression and achieved favorable results. The approach is better in physical significance and is characterized by accurate climate simulation, simple calculation for statistical downscaling and is convenient for application in various climate models
Soil water depletion patterns of artificial forest species and ages on the Loess Plateau (China)
No full textAfforestation as an effective measure to control soil erosion has achieved remarkable effects in northern China. However, large scale of artificial afforestation can increase soil water consumption and induce soil desiccation in arid and semi-arid areas. This study analyzed the variations of soil water storage following the conversion of croplands into forests with different species and stand ages on the Loess Plateau. Three most common artificial forests dominated by Salix matsudana, Populus cathayana, and Sophora japonica with stand ages of 5, 10, and 15 years were investigated to determine the variations in soil water storage. The results showed that soil water storage decreased with increasing afforestation ages and soil depth. Salix matsudana mainly consumed shallow soil water (0-100 cm), P. cathayana mainly consumed deep soil water (100-150 cm), while S. japonica had relatively lower water consumption than the other two species. Converting cropland into forest resulted in a significant water deficit. Soil water deficit in the 0-100 cm soil profiles was significantly higher under S. matsudana than under the other two artificial forests. Severe soil water depletion and obvious soil desiccation occurred after 12 years of afforestation. Therefore, artificial forests with less water consumption, e.g. S. japonica, should be given priority in future afforestation practice. To maintain the sustainability of vegetation, changes in land-use patterns should be considered after 12 years of afforestation
Maize Yield Response to Nitrogen Rate and Plant Density under Film Mulching
No full textFilm mulching has significantly improved crop productivity in semiarid areas. We hypothesized that plants grown under the film-mulched system (FM) require higher N rates and higher plant densities than the non-mulched system (NM) to optimize grain yield and water use efficiency (WUE). A 2-yr field experiment was conducted at the Changwu experimental station to evaluate the effects of N supply and plant density on grain yield, yield components, evapotranspiration, and WUE in spring maize (Zea mays L.) with and without film mulching. Results showed that FM improved topsoil water content. Mulch practice x N rate and mulch practice x plant density interactions existed for yield and WUE in both years. Regression analysis showed that yield and WUE increased with increasing N rate and plant density for FM. The predicted maximum yield (14.3 and 15.1 Mg ha(-1) in 2013 and 2014, respectively) and WUE (31.3 and 38.4 kg ha(-1) mm(-1) in 2013 and 2014, respectively) for FM were obtained at 280 kg N ha(-1) and 80,000 plants ha(-1). Lower N amounts and lower plant densities were required for NM to obtain the maximum yield and WUE. However, field experiments showed that the N amount of 225 kg ha(-1) in FM increased N use efficiency while yielding > 94% of the maximum. In conclusion, film mulching together with optimum N application rates and plant densities can improve maize production and WUE in semiarid regions