围封年限对荒漠草原植物群落生态位和种间联结的影响OA

Enclosure is an important management practice in grassland ecosystems.To clarify the effects of enclosure duration on the niche characteristics and interspecific associations of plants in desert steppe,this study employed methods including importance value,niche breadth,niche overlap,Chi-square test,Ochiai index,and Percentage of Co-occurrence(PC)to investigate the niche characteristics and interspecific associations of dominant plants species in a Stipa breviflora steppe under different enclosure durations(1,10,19,and 25 years).The findings reveal that enclosure duration significantly influenced the importance values and niche breadths of the main plant species.In the early stage of enclosure,Cleistogenes songorica was the dominant species in the community.As enclosure duration extended to 10 and 19 years,the dominance species shifted,and Convolvulus ammannii became the most important species.By 25th year of enclosure,the perennial plant Cleistogenes songorica had regained its status as the absolute dominant species.With increasing enclosure duration,the niche overlap index of the main plant species exhibited a pattern of decrease-increase-decrease,indicating intense interspecific competition.Under different enclosure durations,interspecific associations among the main species in the steppe were predominantly negative.Chi-square analysis revealed that negatively associated species pairs accounted for a large proportion,while the Ochiai index and PC values were generally low,indicating weak species associations.Overall,with increasing enclosure duration,a trade-off pattern was observed between annual and perennial species,leading to shifts in the status of dominant species within the community.The overall species association remained negative,suggesting considerable community fluctuations and strong interspecific competition,reflecting an unstable community structure.