分类： 地球科学 >> 地球科学史 提交时间： 2020-06-22 合作期刊: 《干旱区科学》
摘要： Overgrazing is regarded as one of the key factors of vegetation and soil degradation in the arid and semi-arid regions of Northwest China. Grazing exclusion (GE) is one of the most common pathways used to restore degraded grasslands and to improve their ecosystem services. Nevertheless, there are still significant controversies concerning GE's effects on grassland diversity as well as carbon (C) and nitrogen (N) storage. It remains poorly understood in the arid desert regions, whilst being essential for the sustainable use of grassland resources. To assess the effects of GE on community characteristics and C and N storage of desert plant community in the arid desert regions, we investigated the community structure and plant biomass, as well as C and N storage of plants and soil (0–100 cm depth) in short-term GE (three years) plots and adjacent long-term freely grazing (FG) plots in the areas of sagebrush desert in Northwest China, which are important both for spring-autumn seasonal pasture and for ecological conservation. Our findings indicated that GE was beneficial to the average height, coverage and aboveground biomass (including stems, leaves and inflorescences, and litter) of desert plant community, to the species richness and importance values of subshrubs and perennial herbs, and to the biomass C and N storage of aboveground parts (P<0.05). However, GE was not beneficial to the importance values of annual herbs, root/shoot ratio and total N concentration in the 0–5 and 5–10 cm soil layers (P<0.05). Additionally, the plant density, belowground biomass, and soil organic C concentration and C storage in the 0–100 cm soil layer could not be significantly changed by short-term GE (three years). The results suggest that, although GE was not beneficial for C sequestration in the sagebrush desert ecosystem, it is an effective strategy for improving productivity, diversity, and C and N storage of plants. As a result, GE can be used to rehabilitate degraded grasslands in the arid desert regions of Northwest China.
分类： 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间： 2019-12-06 合作期刊: 《干旱区科学》
YANG Yuling
LI Minfei
MA Jingjing
CHENG Junhui
LIU Yunhua
JIA Hongtao
LI Ning
WU Hongqi
SUN Zongjiu
FAN Yanmin
SHENG Jiandong
JIANG Ping'an
摘要： The association between biodiversity and belowground biomass (BGB) remains a central debate in ecology. In this study, we compared the variations in species richness (SR) and BGB as well as their interaction in the top (0–20 cm), middle (20–50 cm) and deep (50–100 cm) soil depths among 8 grassland types (lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients (elevation, energy condition (annual mean temperature (AMT) and potential evapotranspiration (PET)), and mean annual precipitation (MAP)) based on a 2011–2013 survey of 379 sites in Xinjiang, Northwest China. The SR and BGB varied among the grassland types. The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths. The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition; however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths. The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth. Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition. These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.
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