Comparative Assessment of Soil Physico-chemical Properties in Invasive and Non-invasive Soil Habitats of Lakhimpur District, Assam, India

Abstract

Invasive alien plant species (IAPS) are recognised as major drivers of ecosystem degradation, altering soil properties and nutrient cycling, thereby facilitating their establishment and spread. The present study evaluated the influence of invasive plant species on the physicochemical characteristics of soils in roadside and agricultural habitats of Lakhimpur District, Assam, India. Seasonal field surveys were conducted during the pre-monsoon, monsoon, and post-monsoon periods to assess the occurrence and frequency of invasive plant species and to collect soil samples (0–20 cm depth) from invaded and adjacent non-invaded (control) plots. Soil samples were analysed for key physicochemical parameters using standard analytical methods, and the data were statistically evaluated using two-way analysis of variance (ANOVA) followed by Tukey's HSD post hoc test. Pearson correlation analysis and principal component analysis (PCA) were employed to examine relationships among soil variables and to identify the principal factors distinguishing invaded and non-invaded habitats. A total of fourteen invasive alien plant species were recorded, among which Eichhornia crassipes, Mikania micrantha, Chromolaena odorata, and Parthenium hysterophorus were the most dominant at the study sites. Invaded soils exhibited slightly lower pH (5.6–6.2) but significantly higher organic matter (3.4–4.5%) and total nitrogen (15–34 mg kg⁻¹) than non-invaded soils (p < 0.05), indicating enhanced nutrient accumulation in invaded habitats. Multivariate analysis further demonstrated clear separation between invaded and non-invaded sites based on soil characteristics, suggesting that invasive species substantially modify soil conditions and nutrient dynamics. These changes are likely to create positive soil–plant feedback that enhance the persistence and competitive advantage of invasive species while impeding the regeneration of native vegetation. The findings highlight the importance of habitat-specific management strategies, including timely removal of invasive biomass, restoration with native plant species, and continuous monitoring of soil quality, to reduce invasion-induced soil nutrient enrichment and support long-term ecosystem restoration in the region.