Comparative Study of Litter Quality, Decay Rates and Nutrient Fluxes of Invasive Species, Austroeupatorium inulifolium and Cymbopogon nardus

Abstract

Invasion of alien species into new habitats poses serious threats to their vegetation and ecosystem processes. Austroeupatorium inulifolium, an invasive species, has been rapidly invading degraded grasslands dominated by Cymbopogon nardus, another invasive, in the Knuckles Conservation Area (KCA). Invasive plants with rapid growth rates and elevated leaf nutrient concentrations could alter decomposition process and nutrient release patterns. This study was aimed at studying the litter quality, decay rates and nutrient release patterns of Austroeupatorium and Cymbopogon. In situ litterbag experiment was conducted in less and highly invaded grasslands at KCA. Surface litter and standing litter (above-ground) also have been quantified to assess the contribution of C3 and C4 plants to soil nutrient pool.Litterbags (n=40) were prepared with air-dried litter samples of Austroeupatorium and Cymbopogon and were distributed in highly-invaded (HIG) and less invaded (LIG) sites (by Austroeupatorium). Litterbags were collected at different time intervals and chemically analysed. The decomposition rate was calculated using loss of litter biomass. The surface litter was estimated using randomly placed quadrates (0.0625 cm 2 ). Standing litter biomass was quantified by clipping quadrates (0.25 m 2 ) to the ground level. Contributions to aboveground litterfall by C3 and C4 plants were assessed. The results were statistically analysed and compared using Minitab 14.0.Higher mass loss was observed with Austroeupatorium litter than that of Cymbopogon in both less and highly invaded habitats. Austrosupatorium litter quality (in terms of N and P) is higher than that of Cymbopogon. Leaf litter of Austroeupatorium showed significantly lower C:N and C:P ratios compared to Cymbopogon. Nitrogen and phosphorus release patterns during decomposition found to be slow in both Austroeupatorium and Cymbopogon irrespective of their habitats. Austroeupatorium showed relatively higher decomposition rate throughout the study period compared to Cymbopogon. The surface litter and standing litter biomasses were significantly higher in HIG compared to LIG. In both habitats, C3 plants contributed more to the standing litter biomass than that of C4 plants. Austroeupatorium plants contributed more to the total C3 biomass in both LIG and HIG.The present results suggest that due to higher quality and decomposition rates of Austroeupatorium litter, the invasion may leads to changes in the soil nutrient pools and also their cycling processes. Long-term soil studies need to be carried out in order to investigate these findings further.

Austroeupatorium inulifolium invasion increases arbuscular mycorrhizal abundance in Cymbopogon-dominated grasslands in Knuckles Conservation Area

“…For the past few years, many land-use types in the KCA including man-made grasslands have been invaded by an exotic shrub, Austroeupatorium inulifolium. Studies showed that Austroeupatorium invasion has not only altered the structure and diversity of these grassland communities but also the soil fertility levels, litter loading and decomposition rates as well (Piyasinghe et al, 2013). The present study investigated whether the A. inulifolium invasion has altered the AMF abundance and diversity in Cymbopogon-dominated grasslands in the Knuckles Conservation Area (KCA) in Sri Lanka.…”

<em>Austroeupatorium inulifolium</em>nvasion alters soil microbial populations to facilitate its own growth

“…For the past 7-8 years, many land-use types in the Knuckles Conservation Area (KCA), including highly degraded, man-made grasslands, have been invaded by an exotic shrub, Austroeupatorium inulifolium. Studies suggest that Austroeupatorium invasion can alter the structure and the diversity of these grassland communities, soil edaphic properties and other ecosystem functions including, litter loading and decomposition rates (Piyasinghe et al, 2014). The present study investigated whether the A. inulifolium invasion has altered the soil microbial populations in order to facilitate its growth while at the same time making the environment inhospitable for co-occurring native, Psiadia ceylanica.…”