Describing the role of leaves in aquatic ecosystems based on functional communities, rather than structural communities (e.g. presence/absence), provides a useful way of describing the community and how different leaf types function as food resources. This approach also allows one to determine how C and N function and flow through aquatic food webs.
Research conducted by the Marks Lab has found that different riparian leaf species function as substrate for specific microbes. Using Q-PCR methodology, we have found the microbes are keying in on the specific functions provided by each leaf species.
The research conducted by the Marks Lab challenges the notion that decomposition alone determines the leaf quality, suggesting instead that different leaf types benefit aquatic insects in different ways: some insects use slow-decomposing leaf litter for habitat and its temporal longevity, while others use fast-decomposing litter with more immediate nutrient release. This leaf litter paradigm is exemplified by the finding that up to 25% of the leaf litter from Fremont cottonwood is unavailable to microbes compared to that of narrowleaf cottonwood; the narrowleaf litter continues to hold C and N and provide resources to microbes for a much longer period of time. Further, the leaves of these two species leach at different rates and provide both immediate and longer-term food resources for aquatic insect communities.
This work is being conducted by Jane Marks.
Wymore AS, Compson ZG, McDowell WH, Potter JD, Hungate BA, Whitham TG, Marks JC. 2015. Leaf-litter leachate is distinct in optical properties and bioavailability to stream heterotrophs. Freshwater Science 34 (3), 857-866.
Compson Z, Hungate B, Koch G, Hart S, Maestas J, Adams K, Whitham T, Marks J, 2015. Closely Related Tree Species Differentially Influence the Transfer of Carbon and Nitrogen from Leaf Litter Up the Aquatic Food Web. Ecosystems, 18, 186-201.
LeRoy, Carri J., Wymore, Adam S., Davis, Rebecca, Marks, Jane C, 2014. Indirect influences of a major drought on leaf litter quality and decomposition in a southwestern stream. Fundamental and Applied Limnology / Archiv fur Hydrobiologie, Volume 184, Number 1.
Pastor, A., Compson, Z.G., Dijkstra, P., Riera, J.L., Marti, E. Sabater, F. Hungate, B.A., and Marks, J.C. 2014. Stream carbon and nitrogen supplements during leaf litter decomposition: contrasting patterns for two foundation species. Oecologia 176: 1111-1121.
Compson, Z.G., Adams, K.J., Edwards, J.A., Maestas, J.A., Whitham, T.G., and Marks, J.C. 2013. Leaf litter quality affects aquatic insect emergence: contrasting patterns from two foundation trees. Oecologia 173: 507-519.
Lamit, Louis J., Busby, P.E. Lau, M.K., Compson, Z.G. Wojtowicz, T., Keith, A.R., Zinkgraf, M.S., Schweitzer, J.A., Shuster, S.M., Gehring, C.A., and Whitham, T.G. (2015) Tree genotype mediates covariance among communities from microbes to lichens and arthropods. Journal of Ecology 103: 840–850.
Wojtowicz, T., Compson, Z.G., Lamit, L.J., Whitham, T. G., and Gehring, C.A. 2014. Plant genetic identity of foundation tree species and their hybrids affects a litter‑dwelling generalist predator. Oecologia 176:799–810.