Semi-arid savanna grasslands are vital ecosystems for biodiversity, local livelihoods, and serve as long-term reservoirs of carbon soil. Grasslands store up to 90% of their carbon below ground, making them vital yet overlooked carbon sinks in global climate mitigation efforts. Understanding carbon dynamics in these ecosystems is essential because shifts in vegetation composition, grazing regimes, or management practices can significantly affect soil carbon storage and soil health. Despite the importance, grasslands remain poorly studied and are often misclassified as “wastelands,” leaving them vulnerable to land use changes, overgrazing, and invasion by woody shrubs. In Tamil Nadu’s Tirunelveli district, grasslands are undergoing rapid ecological transformation, particularly due to the encroachment of Dodonaea viscosa, a native shrub historically absent in dense stands. Its proliferation has reduced the availability of palatable grasses and altered biomass allocation patterns, raising concerns about its impact on carbon storage.

This study investigates how species composition, biomass and key environmental factors interact to influence total carbon (TC) dynamics, with a focus on the impact of Dodonaea viscosa removal and grazing management. Field research was conducted in a 52-hectare restoration site stratified into five microhabitats: Dodonaea patches, grassland patches, forest plantations, palm plantations, and streambeds. A paired experimental design compared grazed and ungrazed plots across four treatments: control, D. viscosa removal, removal plus tilling, and removal plus tilling with native grass seeding. Data collected included the density of plants, measurements of above - and below-ground biomass, soil pH, bulk density, total carbon, and total nitrogen. Analytical methods included diversity indices, non-metric multidimensional scaling, Kruskal–Wallis tests, and two-way ANOVA to test for significant differences and drivers of variables.

I found that the species composition and biomass allocation were not statistically significant across microhabitats and treatments. Microhabitat conditions such as soil pH and bulk density emerged as significant factors influencing TC variation, while streambeds and forest plantations supported unique assemblages that contributed to overall heterogeneity. Fenced plots with D. viscosa removal had greater total biomass and higher TC compared to grazed plots.

The findings demonstrate that species composition, grazing management, and shrub encroachment control are one of keyways to improve total carbon storage in semi-arid savanna grasslands. The study highlights the need for context-specific restoration strategies that balance vegetation structure and soil conditions to enhance carbon stocks and biodiversity.