Influence of slope aspect on plant community composition and its implications for restoration of a Chinese mountain range

Excessive human disturbance (e.g., overgrazing, deforestation) has degraded the environment in the Qilian Mountains in China. Vegetative restoration is likely to be a crucial tool to restore these biologically significant habitats, but it is impossible to achieve this goal if the baseline plant community composition and its variation with local environmental conditions were not understood fully. To assess plant community composition by slope aspect, four different aspects – south-facing slope (SF), southwest-facing slope (SW), northwest-facing slope (NW), and north-facing slope (NF) – were surveyed on three almost non-degraded mountains. The results showed that each slope aspect has different abiotic environments. From SF to NF, soil water content has an increasing trend, but it shows no difference between SF and SW; and daily soil temperature and pH have a decreasing trend, while the former shows no difference between SF and SW, and SW and NW; and the latter shows no difference between SW and NW; and soil organic carbon was significantly increased, but soil bulk density was significantly decreased. Herbaceous plants were dominant on SF, SW, and NW, and trees (Picea crassifolia) were dominant on NF. From SF to NW, the dominant herbaceous plants were Agropyron cristatum and Stipa grandis, Agropyron cristatum and Carex aridula, and Kobresia humilis and Carex crebra, respectively, while on NF they were Carex spp. and Polygonum macrophyllum. The baseline survey points to the need to consider underlying patterns in abiotic conditions when planning restoration programs in these degraded mountain habitats, and to select native plants similar to the original vegetation. The survey provides a vital milestone for the development of policy-based funding initiatives and for ongoing vegetation monitoring during restoration to assess if these vegetative targets have been met.