Changes in plant community and soil ecological indicators in response to Prosopis juliflora and Acacia mearnsii invasion and removal in two biodiversity hotspots in Southern India

Abstract

Invasion of alien plant species can alter local plant diversity and ecosystem processes closely linked to soil organic carbon (SOC) and nutrient dynamics. Soil ecosystem processes such as microbial respiration and enzyme activity have been poorly explored under alien plant invasion and especially following invasive plant species removal. We studied the impact of Prosopis juliflora and Acacia mearnsii invasion and subsequent removal on local plant community composition and diversity and on soil microbial respiration and enzyme activity in two biodiversity hotspots in Southern India. Removal of Prosopis promoted recolonisation of local vegetation as indicated by a 38% and 28% increase in species richness and ground vegetation cover, respectively, compared to an unremoved site. Prosopis and Acacia removal led to a significant reduction in soil microbial biomass C (MBC), respiration, dehydrogenase and urease activity due to increased microbial respiration and N mineralisation rate. Higher metabolic quotients qCO 2 in soil at Prosopis and Acacia removed sites indicate that MBC pools declined at a faster rate than SOC, resulting decreased MBC/SOC ratios compared to their respective removed sites. Natural and undisturbed ecosystems maintain more SOC through increased belowground and aboveground C input in the soil, resulting in a higher MBC content per unit SOC. Our results indicate that the interaction between above-and below-ground communities is a critical factor determining the structure and dynamics of local plant communities, especially in ecosystems affected by plant invasions.

Removal or utilization? Testing alternative approaches to the management of an invasive woody legume in an arid Indian grassland

“…Our findings of reduced native plant diversity under Prosopis canopy, and increased richness and cover after its removal align with what studies in other Indian grasslands have found (Kaur et al 2012). Our findings of increased herbaceous diversity after removal of Prosopis are qualitatively similar to recent findings from a similar Prosopis‐ removal experiment in coastal southern India (Murugan et al 2020). Given that our study site and the one studied by Murugan et al (2020) differ considerably in terms of bioclimatic factors, it might be possible that mechanical removal of Prosopis is an efficient method across diverse grassland ecosystems and not just arid grasslands.…”

Immediate and long-term effects of invasive plant species on soil characteristics

“…The significantly lower microbial parameters noted for the other sites were likely a result of the previous agricultural management coupled with early invasive plant-mediated shifts with subsequent contributions to the current longer-term shifts in soil biological properties, as noted for other invasive plants (Gibbons et al, 2017). For example, Murugan et al (2020), in their study of invasive species removal in Southern India, reported invasive leguminous species decreasing SOC and microbial biomass C.…”

Differential Impacts of Acacia Invasion on Nutrient Fluxes in Two Distinct Bornean Lowland Tropical Rain Forests

“…Although we did not determine tree species composition in our study plots, Acacia-invaded MDF and HF in related studies within the Andulau FR [117,118] and at other sites [28,29] have documented a significantly lower abundance of native tree species. A proportionally lower abundance of dipterocarp trees in our invaded plots could result in a decreased density of ectomycorrhizal fungi [119], further affecting nutrient mineralization. Additionally, invading tree species can alter microsite properties, specifically below their canopy [120,121], and impact soil decomposer communities [122][123][124], thus affecting leaf litter decomposition rates and nutrient release in the invaded habitats.…”