Spatial Pattern And Resource Allocation Of Three Shrubs In Response To Grazing Disturbance In Western Ordos

Western Ordos is an important ecologically fragile area in Northwest China,where ancient remnant endangered plants of the Tertiary period such as Tetraena mongolica and Helianthemum songaricum are distributed.The ecological functions of the species such as Zygophyllum xanthoxylon,Ammopiptanthus mongolicus and T.mongolica are especially important as the common desert scrub in the desert area.The harsh natural environment and human disturbances have led to an increasing deterioration of the ecological environment in the region.Population distribution pattern is the most important content in the field of ecology,and plays an important role in the composition,dynamics and function of community.It is the result of the biological characteristics effects of population,interspecific and intraspecific relationships,and environmental conditions.In our study,extending Point Pattern Analysis was to analyze the spatial pattern,interspecific relationship and response of resource allocation to grazing disturbance of three shrubs in western Ordos area.It provides a theoretical basis for protecting the cherished and endangered plants in the Western Ordos region and exploring the ways of sustainable development in desert areas.The main conclusions are as follows:(1)Among the three desert shrub species,the overall distribution pattern of Z.xanthoxylon was from uniform distribution to random distribution,and the spatial distribution pattern of A.mongolicus and T.mongolica populations was from uniform distribution to random distribution with the increase of scale and grazing intensity.The interspecific relationships of the three shrubs showed positive correlations at small scales,and the interspecific relationships of Z.xanthoxylon and A.mongolicus decreased with the increase of scale.There was a negative correlation between the population of Z.xanthoxylon and T.mongolica.The interspecific relationship between A.mongolicus and T.mongolica was gradually weakened.(2)The average moisture content under rotational grazing and grazing was significantly lower than that under enclosure.The average moisture content of shrub was as follows: T.mongolica>Z.xanthoxylon>A.mongolicus.Under different grazing intensities,there were remarkable differences in soil moisture content use efficiency among the three kinds of shrubs.Combined with root distribution,the Z.xanthoxylon population was mainly related to lateral root distribution,while the A.mongolicus and T.mongolica populations were related to main root distribution.(3)The grazing conditions had different effects on the soil bulk density of each soil layer in the shrub community,the soil sorting ability of the enclosed area was better than that in the rotating grazing area.Soil organic carbon,total nitrogen and total phosphorus decreased remarkable with the increase of soil depth.(4)Under different grazing conditions,there were significant differences in density,coverage,average ground diameter and average height of the three shrub communities,which were in the order of rotating grazing area >enclosed area > grazing area.The main food sources of Z.xanthoxylon and A.mongolicus leaves and the tertiary branches of the tertiary branches of T.mongolica.The proportion of root biomass was distinct,the taproots were mostly distributed in the shallow soil,and the lateral roots were mostly distributed in middle soil.with the increase of grazing intensity,the distribution of lateral roots in deep soil(40 ? 80cm)increased(5)The population of Z.xanthoxylon did not respond strongly to grazing disturbance,and long-term grazing did not change the spatial pattern.Compared with Z.xanthoxylon,long-term grazing would change the spatial pattern of A.mongolicus and T.mongolica.The spatial pattern of the three shrubs did not change under rotational grazing,which could reduce the competition among the three shrubs to some extent.Therefore,moderate grazing conditions can improve the stability of the desert ecosystem and play a positive role in maintaining the biodiversity of the desert.