Influence of Phosphorus Loading on Organic Nitrogen Mineralization of Everglades Soils

摘要

There have been recent concerns about the anthropogenic phosphorus (P) loading to the naturally oligotrophic Everglades ecosystem. We investigated the effect of P loading on the biogeochemical cycling of nitrogen (N). We investigated the distribution of the potentially mineralizable N (PMN) rate as an indicator of the influence of P loading on selected microbial activities in soil and detritus layers. Soil characteristics measured included bulk density; total C, N, and P; microbial biomass C; and N and extractable NH+₄. PMN rates ranged from 10.4 to 325 mg N kg-1 d-1. The highest values of microbial biomass C and N, total P, extractable NH+₄, and PMN were observed in the detrital layer, and rates decreased with increasing soil depth. An increase in the size of the microbial pool and heterotrophic activity (organic N mineralization) was found to be related to the P-loading rate and related to the distribution of total P content in the soil and detrital layers. Extractable NH+₄ was a good indicator of PMN rates and total P was found to be significantly correlated to microbial biomass C and N. The stimulatory effect of P enrichment on microbial activity, overall size of the microbial biomass pool, and the PMN rate has led to an increased availability of inorganic N, which could potentially affect macrophyte growth and water quality of the northern Everglades system.