Studies on the niches of the main populations in different habitats of the Loess Hilly Region,China
HU Xiang-ming~(1,2),CHENG Ji-min~1,WAN Hui-e~1,ZHAO Yan-yun~(1,2)(1.Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources,Northwestern Sci-Tech University of Agriculture and Forestry,Yangling 712100,China;2.Graduate School of Chinese Academy of Sciences,Beijing 100039,China)
The landscape of the Loess Hilly Region of China is very complex,with soil water conditions greatly varied.It is well known that the distribution of plant populations and the inter-specific relationships of grassland plants can be greatly affected by habitat conditions.As such,it is of great significance to both clarify the changing patterns of inter-specific relationships in different habitats in order to study the adaptabilities of plant populations to landforms and to forecast population dynamics and community succession trends.In this paper,both an improved Levins niche breadth index and a Pianka niche overlap index are used in order to compare and analyze transects from different habitats,varieties of niche breadth and responses of interspecific relationships and the community structures of various landforms.The results showed that the constructive species of the grassland community,Stipa bungeana,was hardly impacted on by their habitats.The values of niche breadth were highest in four habitats,which was due to the populations having a strong ability to utilize available resources and as they were well adapted to complicated environmental conditions.However,other plant populations were influenced greatly by habitats because these species had a stronger selectiveness to available resources and a relatively higher demand for certain environmental factors.Differences in changing patterns of niche breadth for different plant populations under various habitats were significant,which reflected their different responses to habitats.There were obvious variations in plant populations in different habitats,which was indicative that community structure of grasslands were strongly affected by their habitats.The niche overlap index indicated that there were large overlaps between species of broad niche breadth with others,the reason being that these species had a wide living space and had strong abilities to utilize resources.But there were also large overlaps between species of narrow niches in certain habitats due to a drastic competition for limited resources.With various habitats,there was shown to be changing patterns of niche overlapping with among different specie-pairs,which was mainly determined by biological characteristics and ecological demands of different species,whereas in contrast,the niche overlapping of the same pair-species in different habitats was the result of habitat infection.In conclusion,owing to influences of environmental stress,a higher differentiation in niches of plant populations and relatively lower niche overlaps between species were apparent in the Loess Hilly Region.
【Fund】： “十五”国家科技攻关计划项目(2004BA508B16);; 中国科学院水土保持研究所知识创新领域前沿项目(SW04103);; 国家高技术研究发展计划(863计划项目2002AA2Z4301);; 国家自然科学基金重点项目(30230290);; 国家林业局荒漠化监测专项资助
【CateGory Index】： Q948.1
【CateGory Index】： Q948.1