Influence of Phosphorus Loading on Organic Nitrogen Mineralization of Everglades Soils

Abstract

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|. 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|, 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 NHJ 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.

Mid-rotation response to fertilizer by Pinus radiata D. Don at three contrasting sites

“…Some authors have suggested that the inclusion of P in the fertilizer may stimulate N cycling (Bennett et al 2003) and increase rates of N mineralization (Côté et al 2000;White, Reddy 2000;Carlyle, Nambiar 2001). Our study showed that both N and P were necessary for the volume response observed at granitic and sandy sites.…”

Investigating the use of macrophyte stable C and N isotopic ratios as indicators of wetland eutrophication: Patterns in the P-affected Everglades

“…By this mechanism, isotopically light forms of organic N are preferentially mineralized, leaving the residual organic N in the soil system isotopically heavier (Fogel and Tuross 1999). If P loading of WCA-2A stimulated organic N mineralization and associated loss processes, this theory would predict that the d 15 N of soil organic matter would gradually increase near inflows, leading to a similar, gradual d 15 N increase in the macrophyte communities utilizing mineralized soil N. This may be the case in the Everglades where additions of P to the highly P-limited soil do stimulate microbial activities with a concomitant increase in both N mineralization and NH þ 4 flux (White and Reddy 2000). Despite the plausibility of this argument, however, such a mechanism fails to explain the different responses of Typha and Cladium growing along an identical eutrophication gradient.…”

Spatial variability of soil carbon, nitrogen, and phosphorus content and storage in an alpine wetland in the Qinghai - Tibet Plateau, China

“…Increasing interest has been focused on the role of freshwater wetlands, particularly northern peatlands, as C sinks (White and Reddy 2000;Clair et al 2002;Chmura et al 2003), because these wetlands store about one-third of the global terrestrial soil organic C (SOC) of 1395 Gt (Post et al 1982). Changes in N and P in wetland ecosystems have also received attention, since they are important nutrients for plant growth (Mitsch and Gosselink 2000).…”