Relationship between tree species richness and productivity of Quercus aliena var. acutiserrata forest in Xiaolongshan Mountain, Gansu Province of northwestern China

  Objective  The relationship between species richness and productivity (PDR) is the theoretical basis of biodiversity conservation for natural forests and maintenance of ecosystem functions. Species richness indirectly covers functional diversity, system development diversity and genetic diversity; therefore, the study of the diversity-productivity relationship could analyze the effect of other diversity factors on the productivity of vegetation. Previous studies about PDR mostly focused on the community level. Responses of single species productivity to neighboring biodiversity could affect the relationship between species richness and productivity at the community level. The studies focusing on this topic are rarely conducted.

  Method  This study conducted regression analysis, the index of association (AI) model and heterogeneous Poisson model on inventory data from the Quercus aliena var. acutiserrata natural forest in Xiaolongshan Mountain, Gansu Province of northwestern China to discuss the relationship between species richness and productivity at community and species levels.

  Result  The diversity-productivity relationship had significant scale dependence at the community level. At the 10 m × 10 m sampling scale, a quartic correlation (the hump curve first increased and then decreased) was found between species richness and productivity. At the 20 m × 20 m scale, species richness had no significant effect on productivity. At the species level, the species that behave neutrally in the diversity-productivity relationship had the highest proportion, and accounted for 68.8%−81.3% of total target species; followed by accumulators (i.e., the species increase diversity); and repellers (i.e., the species decrease diversity) had the smallest proportion. A fraction of the species in the study area showed a clear deviation from the neutral relationship. This indicated that the interaction between interspecific promotion or inhibition had an important impact on the diversity-productivity relationship.

  Conclusion  Species richness and species attributes can both affect the productivity of Q. aliena var. acutiserrata forests in Xiaolongshan Mountain of northwestern China.