Invasion of Lantana camara and Ageratina adenophora alters the soil physico-chemical characteristics and microbial biomass of chir pine forests in the central Himalaya, India

Abstract

Plant invasion has been considered as one of the most influential forces that change the soil physico-chemical and biological properties of forest ecosystems. We have investigated the impact of two invasive alien plants, Lantana camara and Ageratina adenophora on soil physico-chemical and microbial properties in three different pine forests (Chanfi, Matial and Mehra) in the central Himalaya. Three subsites viz., non-invaded (NI), L. camara invaded (LI) and A. adenophora invaded (AI), were identified in each forest. Soil samples were collected seasonally in triplicate from the surface (0–10 cm) and subsurface (10–20 and 20–30 cm) depths and processed in the laboratory. PCA and correlation analysis were conducted to explore the relationship between soil properties, status (invaded and non-invaded) and soil depths. The soil variables were further compared between status and depth using linear mixed-effect model (LMM) and Tukey’s HSD test. It was found that in LI and AI sites, soil properties such as moisture (Mo), porosity (Po), organic carbon (OC), total nitrogen (N), potassium (K), microbial biomass carbon (MBC) and nitrogen (MBN) were significantly (p < 0.05) higher and bulk density (BD) was lower in the surface soil (0–10 cm) than NI site but the difference was less prominent in subsurface (10–20 and 20–30 cm) depths. The MBC and MBN showed similar seasonal variations among LI, AI and NI sites following the trend of rainy > summer > winter. The results indicated that L. camara and A. adenophora invasion alter the soil properties and develop nutrient-rich substratum which may further promote the invasiveness in chir pine forest. The present findings would be helpful to develop appropriate management strategies for minimizing the impact of these invasive species on the soil characteristics including nutrient cycling processes of chir pine forests in the central Himalaya.