Do actively cycling C and N pools depend ultimately on soil P supply? Across-biome synthesis

In terrestrial systems the nitrogen cycle is more open than the phosphorus cycle. New N accumulates by biological N fixation and atmospheric deposition, and is readily lost from the system when N is in excess of biological demand. In contrast, available P is supplied from more slowly cycling soil pools already present in the system. Thus, long term rates of ecosystem N accumulation may be constrained by the rate at which available P is provided from stocks of slowly cycling P. In our ASM workshop, we found soil N to be positively correlated with both total and slowly available soil P within each of nine long-term research sites across North America, including six LTER sites. The proposed SPARC will be seeded by members of the ASM workshop and augmented with additional members. The objectives of this SPARC are to (1) produce a paper synthesizing the dependency of soil N accumulation on slowly cycling P within sites, based on the results of the ASM workshop, (2) compile a comprehensive database for soil P stocks across terrestrial LTER sites including information on the availability of related datasets on productivity and nutrient cycling, and (3) scope additional synthesis papers and potential proposals.