AVAILABILITY OF N AND P IN THE RHIZOSPHERE OF THREE SUBTROPICAL SPECIES

Abstract

This study aimed to assess the variation in soil chemical properties in the rhizosphere soils between plantations of 25-year-old Chinese fir (Cunninghamia lanceolata), Chinese gugertree (Schima superba) and Masson pine (Pinus massoniana), which were all situated in a typical subtropical forest in southern China. Acid phosphatase activity, urease activity, nitrogen (N) mineralisation, nitrification rate, available phosphorus (P) and microbial biomass carbon (C), soil basal respiration, pH, total organic C, total N, total P and inorganic N concentrations were examined in the rhizosphere and bulk soils. Results indicated that total organic C, total N, total P, soil basal respiration, net N mineralisation, nitrification rate, urease activity and acid phosphatase activity significantly increased in the rhizosphere compared with bulk soil. This led to higher levels of available P, NH₄⁺-N and NO₃^--N concentrations in the rhizosphere soils. The magnitude of rhizosphere effects on N and P transformations were mostly greater in the Chinese fir plantation followed by the Chinese gugertree and Masson pine plantations. These findings implied that the three species had different capacities in terms of acquiring nutrients.