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Showing papers by "Jane C. Marks published in 2014"


Journal ArticleDOI
TL;DR: The results indicate that biofilms on decomposing litter have specific element requirements driven by litter characteristics, which might have implications for whole-stream nutrient retention.
Abstract: Leaf litter decomposition plays a major role in nutrient dynamics in forested streams. The chemical composition of litter affects its processing by microorganisms, which obtain nutrients from litter and from the water column. The balance of these fluxes is not well known, because they occur simultaneously and thus are difficult to quantify separately. Here, we examined C and N flow from streamwater and leaf litter to microbial biofilms during decomposition. We used isotopically enriched leaves (13C and 15N) from two riparian foundation tree species: fast-decomposing Populus fremontii and slow-decomposing Populus angustifolia, which differed in their concentration of recalcitrant compounds. We adapted the isotope pool dilution method to estimate gross elemental fluxes into litter microbes. Three key findings emerged: litter type strongly affected biomass and stoichiometry of microbial assemblages growing on litter; the proportion of C and N in microorganisms derived from the streamwater, as opposed to the litter, did not differ between litter types, but increased throughout decomposition; gross immobilization of N from the streamwater was higher for P. fremontii compared to P. angustifolia, probably as a consequence of the higher microbial biomass on P. fremontii. In contrast, gross immobilization of C from the streamwater was higher for P. angustifolia, suggesting that dissolved organic C in streamwater was used as an additional energy source by microbial assemblages growing on slow-decomposing litter. These results indicate that biofilms on decomposing litter have specific element requirements driven by litter characteristics, which might have implications for whole-stream nutrient retention.

44 citations


Journal ArticleDOI
TL;DR: In this paper, the authors collected leaf litter from Populus fremontii, Alnus oblongifolia, and Platanus wrightii grown during an average precipitation year (2001) and a record drought year (2002) and performed an in-stream decomposition study using both litter types.
Abstract: Climate models predict that the southwestern United States will experience an increase in drought frequency and intensity with global climate change. We tested the hypothesis that leaf litter produced under natural drought conditions would have an altered litter chemistry profile and affect decomposition rates and macroinvertebrate colonization compared to non-drought conditions. To test this hypothesis we collected leaf litter from Populus fremontii, Alnus oblongifolia, and Platanus wrightii grown during an average precipitation year (2001) and a record drought year (2002) and performed an in-stream decomposition study using both litter types. Three major patterns emerged: 1) Drought conditions significantly altered litter chemistry for mature trees of three species; however, the direction and magnitude of change differed among species and litter chemicals; 2) Leaf litter mass loss was influenced by both differences among species and drought; yet, species effects were more pronounced over time than drought effects; and 3) After 69 days of decomposition, the structure of the macroinvertebrate community was uninfluenced by the drought effect on A. oblongifolia or P. wrightii litters, but there was a community-wide drought effect on macroinvertebrate communities colonizing P. fremontii litter. Many recent studies have explored the influence of drought on stream flow and water temperatures, but these results suggest that litter quality can change under different climatic conditions, but the overall decay of leaf material may not be dramatically altered by droughts. Understanding how forest-stream interactions may be altered by the various influences of climate change will allow for better predictions regarding how long-term disturbances may alter stream ecosystem functioning.

11 citations