Species‐Specific Controls on Rhizosphere Soil Respiration in a Tropical Deciduous Forest of Bangladesh

ABSTRACT

Soil respiration (Rs) is a major pathway of CO ₂ release from terrestrial ecosystems and plays a fundamental role in regulating forest carbon cycling. However, species‐specific controls on rhizosphere soil respiration in tropical deciduous forests remain poorly understood, particularly under tree species with contrasting functional characteristics. This study investigated rhizosphere Rs and associated soil physicochemical properties in the rhizosphere soils of three dominant tree species, Shorea robusta , Albizia procera , and Acacia auriculiformis , in Bhawal National Park, Bangladesh. Rhizosphere soils were collected from two depths (0–15 and 15–30 cm), and soil physicochemical properties were analyzed alongside laboratory‐based measurements of Rs. Soil respiration differed significantly among tree species and soil depths, with the highest values observed in A. auriculiformis , followed by S. robusta , whereas the lowest in A. procera . In contrast, soil organic carbon and total nitrogen were greatest in the rhizosphere of A. procera and lowest in A. auriculiformis . Multivariate analyses revealed distinct differences in rhizosphere soil characteristics among tree species, primarily associated with soil pH, moisture content, calcium, and organic carbon. Multiple regression analysis identified soil moisture and calcium as the strongest predictors of Rs, explaining 52% of the observed variation. The negative relationship between Rs and soil organic carbon suggests differences in carbon turnover and stabilization rather than carbon quantity alone. Although the underlying mechanisms were not directly examined, the observed differences among species are likely associated with species‐specific belowground functional traits that influence rhizosphere processes. These findings demonstrate that tree species identity is an important determinant of belowground carbon dynamics and highlight the importance of considering species‐specific effects when designing forest restoration and management strategies aimed at maintaining soil carbon storage and ecosystem functioning in tropical deciduous forests.