Abstract: As an endemic to China,Juglans mandshurica is one of the rare and endangered plants under protection in Shanxi Province.The individuals of species is shrinking due to serious impacts by human activities,so it is important to study the relationship between J.mandshurica and its habitats for scientific protection.Based on niche theory,niche width and niche overlap of 26 dominant species in J.mandshurica communities in Lishan Nature Reserve of Shanxi were analyzed.The results demonstrated that the constructive species and dominant species,such as J.mandshurica,Forsythia suspense,and Carex lanceolata had a broad niche,because they were widely distributed with more individuals,and had stronger competition for resources.Other species such as Toxicodendron vernicifluum and Rhamnus parvifolia had narrow niche width.The results of general overlap showed that 26 dominant species were not of completely general overlap.The species with wider niche width had wider niche specific overlapping with the other species,such as J.mandshurica,Forsythia suspense,Syringa pekinensis with other species.But some species pairs with wider niche width had narrow niche specific overlap,such as J.mandshurica and Ajuga ciliate,Syringa pekinensis and Artemisia subdigitata etc.The species with narrower niche width are likely to have higher niche specific overlap such as Ostryopsis davidiana and Crataegus pinnatifida.

Key words: Niche width, Niche overlap, Juglans mandshurica communities, Lishan Nature Reserve, Shanxi