Climatic effects on plant species distribution within the forest-steppe ecotone in northern China

Abstract

Questions: As a narrow belt extending from the northern to the southern edges of the temperate forest zone, there is not only a strong temperature gradient and a long geographic distance but also a very sharp precipitation gradient in the temperate forest-steppe in northern China at a regional scale. Patches of forest are scattered in the steppe matrix. At the local scale, each forest patch shows a climatic gradient from patch centre to its edge and to the open steppe. How do these climatic gradients determine plant species distribution for the forest and steppe within this ecotone? Location: The temperate forest-steppe ecotone in northern China. Methods: Species were recorded in paired plots of forest and steppe at 68 sites. t-tests were conducted to show differences in floristic composition among forest types. Mantel tests were applied to correlate site-level floristic distances with geographic and climatic distances for forest and steppe separately as well as for their combination. Floristic differences between paired plots of forest and steppe at each site were correlated to MAT, MAP and geographic factors at that site. Results: There was no significant floristic difference in the understorey of forests dominated by Betula platyphylla, B. dahurica or Populus davidiana. Quercus mongolica forests, however, were floristically dissimilar to the other forest types. Floristic distance of both forests and steppes were significantly correlated with ΔMAT and geographic distance, while there was a significant correlation with ΔMAP for forests only, but not for steppes. The floristic difference between forest understorey and steppe plots within each site showed no significant correlations with climatic or geographic factors. Conclusions: The plant species distribution of both forest and steppe was more dependent on temperature than on precipitation gradients. The floristic distance between the forest understorey and steppe plots within sites seemed to depend on factors other than climate.