Interactive effects of disturbance intensity, seasonality, and soil depth on fine root biomass and carbon and nitrogen content in a tropical dry forest of central India

Abstract

Abstract Disturbance-driven changes in tropical dry forests can alter belowground carbon storage and nutrient dynamics, yet the combined effects of seasonality, soil depth, and root traits on fine-root functioning remain poorly understood. We conducted a factorial field experiment across low, medium, and high disturbance levels. Root samples were collected in five replicates during three seasons from two soil depths (0–10 and 10–20 cm). Fine roots were classified by diameter (<1 and 1–5 mm) and status (live or dead). Biomass and nutrients were analyzed using ANOVA and principal component analysis (PCA). Fine-root biomass, carbon, and nitrogen content significantly declined with increasing disturbance, with strongest reductions during winter. Biomass declined from 1.75 g m−2 under low disturbance to 1.10 g m−2 under high disturbance, maximum during the rainy season (2.10 g m−2) and minimum during winter. Carbon content ranged from 250 to 400 mg m−2, whereas nitrogen ranged from 22.5 to 35 mg m−2. Roots <1 mm had higher nutrient concentrations and greater sensitivity to disturbance. Soil depth had a stronger effect on nitrogen than carbon, with higher carbon and nitrogen contents in surface soil. The C:N ratio increased with disturbance in live roots, suggesting reduced nutrient quality under stress, while dead roots showed greater variability and higher C:N ratios. PCA revealed separation of root traits by season and disturbance level, indicating shifts in belowground resource allocation and nutrient status. Overall, increasing disturbance reduced fine-root biomass and nutrient concentrations, potentially weakening belowground carbon sequestration and nutrient cycling in tropical dry forests.