Austroeupatorium inulifolium invasion alters litter dynamics in Cymbopogon nardus-dominated man-made grasslands

Austroeupatorium inulifolium has become a noxious invader, expanding its populations in a variety of habitats in the mid-country of Sri Lanka. Highly degraded man-made grasslands dominated by Cymbopogon nardus in the Knuckles Conservation Area (KCA) have shown a high vulnerability for A. inulifolium spread. The present study was aimed at assessing the ability of A. inulifolium to alter soil nutrient turnover through changes in quality and quantity of litter inputs, and decomposition rates. Two grassland communities were selected based on the extent of A. inulifolium invasion viz., less-invaded (LIG) and highly-invaded (HIG). The surface litter and standing litter biomass was quantified using randomly placed 1 m2 and 0.25 m2 quadrats, respectively. An in situ litterbag experiment was conducted using air-dried A. inulifolium and C. nardus litter separately and as a mixture to estimate decomposition rates and nutrient release patterns. The surface and standing litter biomass were significantly higher (at p ≤ 0.001 and ≤ 0.05, respectively) in HIG than in LIG, with A. inulifolium contributing significantly (at p ≤ 0.001) to the standing litter biomass in both communities. A. inulifolium litter decayed and released nutrients rapidly than that of C. nardus. The findings of the study suggest that A. inulifolium invasion has the potential to increase the soil nutrient status through its high-nutrient litter inputs, rapid decomposition and nutrient release patterns. The results demonstrated the positive impact of A. inulifolium invasion on these nutrient-starved grasslands, while highlighting the potential role of invasive species in altering ecosystem functions, especially when they colonise degraded habitats.