Distribution of non-native plant species along elevation gradients in a protected area in the eastern Himalayas, China

Mountain ecosystems are becoming increasingly threatened by non-native plant invasions. In this paper, the occurrence of non-native plant species was examined in a protected area (Laojun Mountain Area) in the eastern Himalayas, China. Sampling plots were systematically set up along elevation from 1950 to 3500m a.s.l. Sixty-one non-natives were recorded that account for 24% of the roadside flora. The number of non-native species decreased continuously with increasing elevation and significant nestedness was found between the low- and high-elevation plots. Moreover, all non-native species distributed at high elevation were also found at low elevation and mountain specialists were not found among non-natives. These results indicate that the eastern Himalayan ecosystem is not immune to invasion and most of the non-natives spread from lowland areas upward to the highlands. Future efforts to manage plant invasions in this region should concentrate on low-elevation areas where agriculture and disturbances by tourism are increasing rapidly.