Soil Carbon and Nutrient Cycling Regulated by Fine Roots Distribution and Dynamics in Teak (Tectona grandis L.)-Based Agroforestry System in Semi-Arid Central India

Understanding of root distribution provides insights on the species-specific tree-crop interactions and its nutrient cycling. This study intended to understand spatio-temporal variation of fine roots distribution, soil organic carbon (SOC), nutrient availability and intercrop yield in a teak-based agroforestry system across a gradient of soil depth and distance from tree-base. Soil samples were collected during winter (2020) and summer (2021) at six distances (0.5-3.0 m) and six depths (0-0.90 m). Fine roots (< 2 mm) were analyzed for length, biomass, and length density. Soil samples were assessed for SOC, nutrients (N, P, K), Walkley-Black C, and bulk density to estimate SOC stock. Crop yields (black gram and mustard) were recorded at varying distances from the tree base. Statistical analyses included analysis of variance (ANOVA) under factorial randomized block design and principal component analysis (PCA) for multivariate analysis. Fine root length and biomass peaked at 1.5 m distance and 0.15-0.30 m depth, with higher values in winter. Bulk density increased with depth and distance, while SOC and nutrient levels were highest near the tree (0.5-1.0 m) and surface layers (0-0.15 m). Available N and P sharply declined with distance and depth; K showed milder variation. Crop yields increased up to 25% with distance from the tree, indicating reduced competition. The PCA highlighted optimal root growth and nutrient availability between 1.0 and 1.5 m distance and 0.15-0.45 m depth. Enhanced SOC near the tree base indicates strong C-sequestration potential, while reduced crop yields nearby suggest root-induced competition. These findings underscore the need to balance tree-crop interactions for sustainable productivity.