Altered composition and structure of plant communities in response to Lantana camara invasion in forest ecosystems of Kumaun Himalaya, India

Abstract

Ecosystem stability is being threatened by the invasion of exotic plant species. This study examined the impact of Lantana camara (Verbenaceae) on associated plant communities and regeneration status across three different forests: Banj oak (Quercus leucotrichophora), Chir pine (Pinus roxburghii) and Sal (Shorea robusta) in Kumaun Central Himalaya, India. In each forest site, two paired plots (invaded by L. camara and uninvaded) of 0.5 hectare each were established. Within each plot, 5 random quadrats of 10 × 10 m for trees, 10 quadrats of 5 × 5 m for shrubs and 20 quadrats of 1 × 1 m for herbs were sampled and community variables for each species were recorded. Regeneration status was studied by classifying individuals into different size classes and developing population structure for tree species. Results showed decreasing trend in the density (92 % in oak, 74.7 % in pine, and 80.3 % in sal forests) and basal area of tree layer in invaded plots. However, shrub and herb layers exhibited higher density and diversity in invaded areas. Tree regeneration was decreased in invaded sites with few seedlings converting to sapling and mature trees mainly in oak and pine forests. Statistical analyses (ANOVA) revealed that invasion had significant impact on density, diversity (H′), evenness (e) and species richness (SN), especially in the seedling and shrub layers. Principal Component Analysis indicated that variation due to invasion was explained by differences in diversity, species richness and dominance. The invasion by L. camara led to increase in the shrub and herb layer, which in turn had a detrimental impact on the tree layer of the studied forests. The observed decline in species diversity and richness indicate loss of ecosystem resilience and function. This decline in the native flora could have long-term harmful effect on the forest ecosystem.