Tree species distribution and its impact on soil properties, and nitrogen and phosphorus mineralization in a humid subtropical forest ecosystem of northeastern India

Abstract

The impact of tree species on net N and P mineralization, and soil properties beneath their canopy were studied in a subtropical evergreen broad-leaved forest of northeastern India. Four types of experimental plots were identified based on tree species dominance. The first plot was dominated by Myrica esculenta Buch.-Ham. ex D. Don., the second by Rhododendron arboreum Sm., the third by Neolitsea cassia Koster., and the fourth was a mixed-species plot. Organic carbon content (3.11') and NH₄⁺-N concentration (11.40 μg·g^-1) in the Rhododendron plot, pH (4.64) and total N content (0.89') in the mixed plot, available P (5.16 μg·g^-1) and NO₃^--N (8.63 μg·g^-1) concentrations in the Neolitsea plot were significantly higher (p < 0.001) than the other plots. All these soil parameters were lowest in the Myrica plot. The net N and P mineralization rates in an annual cycle across different plots ranged between 18.83 and 22.14 μg·g^-1·month^-1 and between 4.54 and 5.87 μg·g^-1·month^-1, respectively. The flux varied significantly (p < 0.001) among the plots, the lowest and highest being in the Myrica plot and mixed plots, respectively. The differences in soil properties and in net N and P mineralization among different species plots were related to litter quality and yield of the respective species as well as soil microenvironment.