Assessing the synergistic effect of two invasive plants on native plant communities in Kanha National Park, Central India

Abstract

Over time, community assembly and functioning of native ecosystems is known to shift from native species to non-native species thus, restructuring the native community. When this shift of diverse native ecosystem interaction to less diverse invasive-centric interaction, occurs due to synergistic effect of two invasive species, it is known as ‘invasional meltdown’. Since last two decades, the effects posed by invasive species on ecosystems are widely debated. Studies across the globe have reported simplification in community structure with biological invasions, leading towards monotonous ecosystems and homogenization of biodiversity. 2. I assessed the interaction of two invasive plant species, Lantana camara complex (lantana) and Pogostemon benghalensis (pogostemon) with native understorey vegetation in Shorea robusta (Sal) forest of Kanha National Park, Central India. Here, I tested biotic homogenization, invasional meltdown and intermediate disturbance hypothesis. To achieve this, 56 km2 out of 230 km2 of Sal forest covering 5613 cells (100X100m) was extensively surveyed, to model species distribution of lantana and pogostemon using different correlative, mechanistic and ensemble models. From the surveyed area, 120 plots (10X10m) were selected based on the percent cover of invasive species, where vegetation and soil sampling was conducted. The correlations in community composition with edaphic and climatic parameters were established using nonparametric ordination, and the potential effects of single invasive species and their interaction were estimated using linear models by considering the uninvaded plots as control. 3. From the sampled area, 40 km2 (71%) and 37 km2 (66%) were found to be invaded by lantana and pogostemon respectively. Lantana presence was best explained as a function of nearby lantana density and was constrained by evapo-transpiration rate of summer, light availability and dry stress. Whereas, pogostemon presence was best explained by moistness of forest patch, lower summer temperature and habitat openings due to anthropogenic factors and was constrained due to climatic heat, edaphic dry stress, and remote deciduous forest. Study results indicate an insignificant effect of intermediate disturbances, and significant impacts of invasive species on species composition and edaphic factors, thereby affirming the biotic homogenization and invasional meltdown hypothesis and rejecting intermediate disturbance hypothesis. Present study can be used as an evidence to prioritize immediate management interventions in areas where multiple invasions are present, as the chances of extirpation of rare species is high.