Main drivers of plant diversity patterns of rubber plantations in the Greater Mekong Subregion

Abstract

Abstract. The Greater Mekong Subregion (GMS) is one the global biodiversity hotspots. However, the diversity has been seriously threatened due to environmental degradation and deforestation, especially by expansion of rubber plantations. Yet, little is known about the impact of expansion of rubber plantations on regional plant diversity as well as the drivers for plant diversity of rubber plantations in this region. In this study, we analyzed plant diversity patterns of rubber plantations in the GMS based on a ground survey of a large number of samples. We found that diversity varied across countries due to varying agricultural intensities. Laos had the highest diversity, followed China, Myanmar, and Cambodia. Plant species richness of Laos was about 1.5 times that of Vietnam. We uncovered latitudinal gradients in plant diversity across these artificial forests of rubber plantations and these gradients caused by environmental variables such as temperature. Results of redundancy analysis (RDA), multiple regression, and random forest demonstrated that latitude and temperature were the two most important drivers for the composition and diversity of rubber plantations in the GMS. Meanwhile, we also found that higher dominance of some exotic species (such as Chromolaena odorata and Mimosa pudica) was associated with a loss of plant diversity within rubber plantations; however, not all exotic plants cause the loss of plant diversity in rubber plantations. In conclusion, not only environmental factors (temperature), but also exotic species were the main factors affecting plant diversity of these artificial stands. Much more effort should be made to balance agricultural production with conservation goals in this region, particularly to minimize the diversity loss in Vietnam and Cambodia.