Production and fate of soluble organic carbon, nitrogen, and phosphorus during forest ecosystem development: Root versus leaf litter

Dissolved organic matter (DOM) plays several important roles in forest ecosystems. DOM contributes to soil organic matter (SOM) accumulation and provides a source of nutrients that may become available for vegetation through mineralization.; The research presented in this dissertation had the following objectives: (1) examine fine root production during forest succession, (2) quantify DOM production (as dissolved organic C, N, and P - DOC, DON, and DOP) from fine root litter, leaf and other aboveground litter, and throughfall during forest succession and ecosystem development, (3) assess the effect of litter type and species on DOM quality, and (4) compare the fate of DOC originating from root versus leaf litter.; To address these four objectives a field study was conducted on the Mt. Shasta Mudflows Research Natural Area in northern California, USA.; Total DOM production generally increased early in succession for DOC and DON, but not for DOP. DOC and DON production from root litter was less than or equal to that from leaf litter, but DOP production from root litter was greater than that from leaf litter. In general, DOM production was predominantly driven by changes in biomass production across the chronosequence, and changes in DOM content of litter had a smaller effect.; In terms of DOM quality, the fraction of refractory DOC increased, while the fraction of labile DOC decreased with ecosystem age.; Results from a 47 day-long column study using 14C labeled litter showed that 14C losses from leaf litter were greater than losses from root litter.; The results of this study show that roots are an important source of DOM. Roots play an increasingly important role in DOM production during ecosystem development and may significantly contribute to accumulation of SOM especially since DOC produced by roots was more refractory than leaf litter. In contrast, root litter produces more labile DON and DOP compounds which can provide nutrients to vegetation. (Abstract shortened by UMI.)...