Analysis Of Soil Characteristics And Species Diversity Of Plant Community Patches And Their Relationships In The Loess Hilly Region

The loess hilly region is one of the most serious areas of soil erosion and soil degradation in China.It is also a key and difficult area for eco-environmental construction and management in China.The patch distribution pattern of plant communities is the result of the interaction between ecological and hydrological processes in arid and semi-arid areas,and it is also a common and relatively stable way of the existence of vegetation in this area.Plant habitat changes due to patch distribution of plant communities,which affects species diversity.Studying the effects of plant community patch on soil properties and species diversity can better predict the development trend of plant spatial pattern in the community,and provide scientific basis and theoretical reference for correctly understanding and evaluating the development trend of slope vegetation pattern and its ecological effects in loess hilly region.In this paper,the Yanhe River basin was used as the study area and the rainfall difference from southeast to northwest was used as the large environmental gradient.And typical communities were selected as the research objects.Field investigation and indoor analysis were conducted to study the soil properties of different patches(plant shrub grassland patch and bare land patch)in different soil layers.In this study,the characteristics of species diversity of different community patches and typical communities were analyzed,and the relationship between species diversity and soil properties was studied.The main conclusions are as follows:(1)In the Yanhe River basin,with the variation of rainfall gradient from southeast to northwest,the effects of plant community patches on soil properties were different in different communities.In 0-10 cm and 10-20 cm soil layers,the soil bulk density in all plots of Bothriochloa ischaemum,Artemisia gmelinii and Sophora davidii communities showed that:shrub grassland patch<bare land patch.The soil organic matter content in all plots showed that:shrub grassland patch>bare land patch.The soil water-stable aggregates content in all plots showed that:shrub grassland patch>bare land patch.In the same patch,the soil bulk density in all plots showed 0-10 cm soil layer less than 10-20 cm soil layer,and the soil organic matter content showed 0-10 cm soil layer more than 10-20 cm soil layer.With the decrease of rainfall from southeast to northwest,the soil moisture content in all plots of Bothriochloa ischaemum,Artemisia gmelinii and Sophora davidii communities generally showed a gradually decreasing trend.T-test results showed that shrub grassland patch could significantly increase soil organic matter content and water-stable aggregates content,decrease soil bulk density,and improve local soil physical properties compared with bare land patch.(2)The patchy distribution pattern of plant communities had different effects on the species diversity index of typical communities and shrub grassland and bare land patches.Margalef richness index,Shannon-Wiener diversity index and Simpson dominance index in the species a diversity of shrub grassland and bare patches in all plots were basically as follows:shrub grassland patch>bare patch.Pielou evenness index was generally showed that:shrub grassland patch<bare patch.There was no significant difference in species diversity index between most shrub grassland and bare patches.For ? diversity,with the change of rainfall gradient,shrub grassland and bare patches of S(?)rensen index in all plots of Bothriochloa ischaemum and Sophora davidii communities increased at first and decreased thereafter,Cody index exhibited a gradually increased tendency.The Sorensen index between shrub grassland and bare patches in all plots of Artemisia gmelinii community was basically unchanged,and Cody index showed a trend of increasing first and then decreasing.The results of the analysis of species diversity of different patches showed that shrub grassland could improve microhabitat and increase local species diversity to a certain extent.Along the slope direction,Margalef richness index,Shannon-Wiener diversity index,Pielou evenness index and Simpson dominance index in all plots of Bothriochloa ischaemum,Artemisia gmelinii and Sophora davidii communities all generally showed a wave-like trend.(3)The results of analysis of the relationship between species diversity and soil properties were different.The results of correlation analysis showed that soil bulk density and organic matter were the main influencing factors that affect the species diversity of shrub grassland and bare patches.There were positive or negative correlations between species diversity of typical communities and soil properties under different patches,but there was no significant difference(P<0.05).Stepwise regression analysis results showed that soil properties of different patches mainly affected the evenness and dominance of species and the substitution rate of species along gradients,but had little effect on richness and diversity.And the soil properties of different patches had no obvious effect on the species diversity of typical communities.The principal component analysis showed that 5 and 4 principal components could be selected as the basis for the principal component analysis for evaluating community patches and typical communities.