Diversity Characteristics And Species Coexistence Pattern Of Fenced And Fenced Grazing Plant Communities In Desert Steppe

Since Yanchi County of Ningxia Hui Autonomous Region implemented grassland enclosure and banned grazing in May 2001,it has been 19 years.During this period,measures for contracting grasslands to households or joint households,and grassland fences based on this have been adopted to prohibit grazing.Fencing and grazing prohibition have also undergone a gradual change from the complete fenced pasture prohibition in the past to fenced grazing or rotation grazing.These measures have made the ecological environment overall and greatly improved,and farmers and herdsmen have also paid a price for this.The specific effect of enclosure and grazing ban on vegetation improvement has become one of the main factors that determine the direction of grazing ban policy.The tracking study has been carried out,from the initial evaluation of grassland coverage,grass layer height,and positive effects of plant species,to the subsequent restrictions on animal activities,no or little interference with grassland degradation,and crust formation to promote plant community structure The evaluation of negative effects such as simplification has gone through a comprehensive and deepening process.The desert grassland is the main vegetation type in Yanchi County,Ningxia.Excessive reclamation and grazing have caused the grasslands in this area to degrade to varying degrees.Since the 21st century,policies such as fenced grazing and returning farmland to grass have promoted the overall vegetation situation in the region.The fencing function was obvious during the restoration process.In Yanchi County,gray calcareous soil and aeolian sandy soil are typical zonal soils.For the restoration of specific degraded ecosystems,it is necessary to have a clear restoration goal.Different habitats have different composition,community structure,and species diversity.Differences in ecosystem functions.The ultimate goal of the restoration of degraded ecosystems is to realize the restoration of ecosystem functions.In some studies,the background conditions,grazing prohibition methods and corresponding vegetation succession stages of the research object are not strictly defined or the statements are not clear,which has led to obvious differences in the conclusions of the research on the impact of enclosure and grazing on vegetation,which directly affects the closure.The future direction of the policy of no-breeding and grazing and the health of grassland ecosystems.At present,the research on the impact of fence enclosure on diversity is mostly focused on the study of diversity characteristics,and there is relatively little research on the diversity of plant communities on different soil types under fence enclosure,in which the diversity characteristics and species at different time scales Research on the coexistence pattern is lacking.This study focuses on the maintenance mechanism of plant community species diversity,with different soil types in long-term enclosure and grazing,and different time scale plant communities as the research object,using SPSS20.0 independent sample T test,analysis of variance,CANOCO 5.0 Principal component analysis(PCA),redundancy analysis(RDA),zero-model species coexistence pattern analysis,significant species pair identification and other analytical methods to study plant community structure characteristics at different time scales on different soil types under fenced enclosure and grazing conditions,Species diversity and species coexistence pattern.The results are as follows:1)Fencing is one of the most effective ways to restore degraded grasslands in desert grasslands.The specific performance is as follows:the height of the fencing is 58%higher than that of the fencing grazing community;the coverage is increased by 47%;the degree is reduced by 25%;Biomass increased by 23%,which promoted the development of plant communities in the direction of progress and succession.2)Community characteristics:under fence enclosure,the community type is mainly Gramineae+Leguminosae,and the main functional group is perennial Gramineae;under fence grazing,the community type is mainly Leguminosae+Asteraceae,and the main functional group is Asteraceae And legumes.Compared with grazing management,the biomass,abundance,height,and coverage of Gramineae and Leguminosae on grey calcareous soil were significantly different under enclosure conditions;the biomass and abundance of Compositae were significantly different.The biomass,abundance and height of Gramineae on aeolian sandy soil are significantly different;the controlling factors are mainly 0-5cm coarse sand content,clay powder content,TN,TC,pH,10-20cm clay powder content The difference in species composition and distribution in the community depends mainly on the soil habitat.3)Diversity characteristics:Compared with grazing management,there is no significant difference in the fence enclosure diversity index;there is a significant difference in the alpha diversity index between gray calcium soil and aeolian sand soil.The ? diversity of lime-calcareous soil in fenced enclosure area was significantly lower than that of aeolian sandy soil,and the turnover rate of species on aeolian sandy soil was higher than that of grey calcareous soil.Environmental filtration plays a role in regulating diversity.Fencing enclosure significantly improves soil organic carbon and total nitrogen.Enclosure and grazing significantly affected the diversity of lime-calcareous soil habitat communities,but had a weaker effect on the diversity of aeolian soil.4)Species coexistence pattern:The significant species competition coexistence pattern mainly occurs in the lime-calcareous soil habitat,and the maintenance of plant diversity is regulated by the biological filtration mechanism.Wind-sand soil mainly exhibits a non-competitive coexistence pattern,and plant diversity may be regulated by environmental filtering and random processes.