N : P balance in wetland forests: Productivity across a biogeochemical continuum

The nature of and driving forces behind variation among wetland forests in terms of biogeochemistry and vegetation production are not well understood. We suggest that insight into biogeochemical and productivity differences m ay be gained by examining the degree to which nitrogen and phosphorus are b alanced within wetland vegetation, on the basis of examinations of data rel ated to N:P balance and nutrient use efficiencies, vegetation productivity in both depressional and riverine forests appears to be primarily N limited . In contrast to some current theories of wetland biogeochemistry, these da ta suggest that when P deficiency occurs at all, it represents a secondary productivity constraint in comparison to N. Similarly, a biogeochemical con tinuum is suggested for wetland forests based on the relationship between N :P ratios in senesced foliage vs. annual litterfall mass. We theorize that the position of a particular wetland forest on this continuum reflects the integration of its geomorphic position and biogeochemical history. In addit ion, the position of a particular system on the continuum may have predicti ve value with regard to net primary productivity and nutrient transformatio n capabilities.