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Chen B.,Hulunber Grassland Ecosystem Research Station | Chen B.,Chinese Academy of Agricultural Sciences | Li H.,Xin Baerhu You Banner Grassland Station of Hulunber | Zhu Y.,Nanjing University | And 8 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Hulunber steppe with a plateau landscape is a component of the Mongolian Plateau of central Asia and located in the eastern part of Inner Mongolian. Its elevation is almost over 600 meters, and the ground-surface is undulated due to hilly distribution and precipitation decrease from the east to west following the climatic change from sub-humid to semi-arid. The region of ecological space expanded greatly as complex terrain small changes, and the relationship between vegetation and environment is complicated. Our study is focused on the effect of the terrain and the influence of soil-environment on the structure of Hulunber steppe communities. A DCCA was used to quantitatively analyze the relationship between soil and topographic factors, both of which influenced the changes of community structure based on field experiment in 2006 in Hulunber grassland. The results showed that the pure soil environmental factors can explain 12.48% of the species diversity change, and the pure topographic factors can explain 8.34% of the species diversity change. 4.76% can be explained by the latter two factors and the unexplainable parts were 74.42%. Topographic factors played an important role to community structure by affecting the reallocation of the hydro-thermal combination. Among all the factors, total soil nitrogen, effective potassium and nitrogen, available phosphorus, organic matter and the slope shape decide the changes of the communities' niche, which lead to changes of the communities' types distribution gradient.

Chen B.,Hulunber Grassland Ecosystem Research Station | Chen B.,Chinese Academy of Agricultural Sciences | Yang G.,Hulunber Grassland Ecosystem Research Station | Yang G.,Chinese Academy of Agricultural Sciences | And 6 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Grassland degradation is one of the important environment and resource issues in North China. Different degrees of grassland degradation in Hulunber grassland are mainly caused by global climate change, overexploitation and other reasons, which threats to the sustainable development of grassland animal husbandry and improvement of living standards of farmers. The relationship between spatial patterns and ecological processes at different scales is one of the hottest research topics, the key point of which is to select an appropriate observation scale. Disturbance as part of the process, is the main sources of spatial heterogeneity, which can significantly change the ecological pattern and processes at different scales, causing apparently shift of the structure and function of ecological systems. Small-scale spatial structure of plant species was important in plant ecology as it affected the dynamics of plant populations, communities and ecosystem processes. Hulunber steppe with a plateau landscape is a component of the Mongolian Plateau in central Asia and located in the eastern part of Inner Mongolian, which with the unique ecosystem characteristics, relatively well-preserved natural environment, abundant landscape types and biodiversity, relatively advanced and intensive production mode, is the optimal object for researching the natural ecological patterns and process in steppe ecosystems, and its responses to human-caused disturbances. Leymus chinensis, the zonal vegetation in Hulunber grassland, has a great significance for understanding ecological processes and sustainable utilization of grassland resources with studies on population patterns of Leymus chinensis. We recorded fine-scale (0 - 100cm) spatial patterns of this species as presence/absence maps from 2m × 2m grids (2cm × 2cm quadrats) in two plots under three kinds of disturbances: cutting, fencing and grazing. Ripley's K function and Monte Carlo stochastic simulation method were used to quantitatively analyze Lemus chinensis population patterns. Based on life history characteristics, strategies of ecological adaptation of Leymus chinensis population and interspecific interaction in the community under different disturbances, the mechanism generating and maintaining these patterns was discussed. The results showed that: First, there were significant effects on spatial patterns of Lemus chinensis populations under the disturbances of cutting, fencing and grazing in the Restoration Succession Sample of Leymus chinensis Meadow Steppe (abbr. LM) and Long-term Observation Sample of Stipa baicalensis Meadow Steppe (abbr. SM). The density of Leymus chinensis population in LM was significantly greater than SM, but its L (h) value in LM was lower than SM, which indicated the aggregation level of SM was greater than LM. Second, there is a difference at virous scales. On the scales less than certain critical points with the population usually characterized by non-random distribution, is being regular in LM and clumped in SM respectively; In contrast, if the scales enlarge beyond these critical points, the plants will disperse randomly but without disturbances of cutting which is clumped. It is mainly related to Leymus chinensis's reproductive responses community's position, and competition ability for resources under different disturbances. Third, the nature of spatial structure seemingly depends on the scale of observation, but the smaller-scale data are likely to provide a more powerful biologically explanation for local spatial structure in this community.

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