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Inner Mongolia Agricultural University (2019)

Shrub-herbaceous Interactions in A Desert Steppe under Different Stocking Rate

闫宝龙;

Titre : Shrub-herbaceous Interactions in A Desert Steppe under Different Stocking Rate

Auteur : 闫宝龙;

Grade : Doctoral Dissertation 2019

Université : Inner Mongolia Agricultural University

Résumé partiel
In recent years,the dynamics of woody plants under grazing disturbance is one of the hot issues in grassland ecology and grassland management.Ecologists focused on the dynamic change mechanism of woody plants and its impact on ecosystem functions and services ;while grassland managers paid more attention on the ideal proportion and sustainable utilization of woody and herbaceous plants.Different plant populations or functional groups had various strategies to cope with grazing,which lead to changes of the relationship among plant populations or functional groups.In order to explore the response characteristics and principles of the relationship between shrubby and herbaceous plants under different stocking rates(no grazing,CK ;light grazing,LG ;moderate grazing,MG ;heavy grazing,HG,respectively)in desert steppe,a long-term control experiment(2004-2018)of stocking rate was applied in a desert steppe.From 2016 to 2018,concentric circle method(radius 0.25 m,0.5 m,0.75 m and 1 m,respectively)was used to monitor individual quantitative characteristics of four main shrubs and semi-shrubs,including Artemisia frigida,Kochia prostrata,Caragana microphylla and Ceratoides latens,as well as the individual quantitative characteristics of plants and soil properties in adjacent areas(radius 1 m).According to the dynamic trend of shrub-herbaceous plants in time series(2004-2017),variance analysis was used to compare the difference of shrubs’ individual quantity characteristics,and the difference of main plant population density(Stipa breviflora,Cleistogenes songorica,A.frigida),functional groups density(perennial grasses,perennial forbs,shrubs and semi-shrubs,annuals and biennials),and community density in adjacent areas under different stocking rate and in different direction(east,south,west and north).The geostatistical method was used to analyze the heterogeneity of soil properties and the spatial distribution of population density of main shrubs(A.frigida,K.prostrata,C.microphylla and C.latens).The population density,functional group density,community density and community standing crop of main herbaceous populations(S.breviflora,C.songorica)were also analyzed.Canonical correlation was used to analyze the interactions between shrubs and their neighboring plant populations,functional groups and communities,as well as the relationship between shrubs and soil properties.This paper tried to reveal the tradc-off process of shrub-hcrbaccous on multiple organizational levels under biotic and abioticfactors interactions.The main results are as follows :(1)Stocking rate had a significant effect on species composition of plant communities in desert steppe.With the increase of grazing years and stocking rate,the dominant effect of herbaceous plants on the community was enhanced(the aboveground standing crop of MG and HG were higher than 90%from 2014 to 2017),meanwhile the functional group of perennial grasses represented by S.breviflora gradually occupied a dominant role in the community.Shrubs showed an opposite trend with the longer grazing time and heavier stocking rate,after 10 consecutive years of grazing(LG,MG,HG),the accumulated aboveground standing crop of shrubs tended to flatten.The individual quality characteristics of A.frigida,K.prostrata,C.microphylla and C.latens were generally decreased.(2)A.frigida and K.prostrata influenced the population density,functional group density and community characteristics in the range of 0.25 m in the nearest neighbor,while the effect of C.microphylla and C.latens on the population density,functional group density and community characteristics in the nearest neighbor was up to about 0.50 m.Shrubs and semi-shrubs had the orientation effect on the neighboring plants,but the influence of different shrub species on the direction existed differences.(3)There were distance effect,orientation effect,species effect and stocking rate effect of A.frigida,K.prostrata,C.microphylla and C.latens posed on soil nutrients in their adjacent areas.The distance effect was mainly reflected in the range of 0.50 m centering on shrubs,however the four shrubs showed different effects in orientation effect,species effect and stocking rate effect.

Mots clés : Temperate grassland; Grazing intensity; Interspecific relationship; Level of organization; Spatial pattern; Conical correlation;

Présentation (CNKI)

Page publiée le 28 février 2020