Jane C Marks
Northern Arizona University, USA
More InfoRevisiting the Fate of Dead Leaves in Streams: Lessons from Stable Isotope Tracers
Respiration by stream microorganisms consumes most of the carbon entering from terrestrial landscapes. A small but vital flux of plant litter forms the base of the food web and shapes the ecology and biogeochemistry of streams. As terrestrial leaf litter decomposes in rivers, its constituent elements follow multiple pathways. Carbon leached as dissolved organic matter can be quickly taken up, then respired by microbes before it can be transferred to the macroscopic food web. Alternatively, this detrital carbon can be ingested and assimilated by aquatic invertebrates, so it is retained longer in the stream and transferred to higher trophic levels. Our research focuses on determining how litter traits influence pathways of element flow. We use leaves labeled with 15N and 13C to trace pathways of element flow from leaves to stream food webs and ecosystems. We incubated leaves from twelve species of riparian streams in Oak Creek (Arizona, USA) in the presence and absence of invertebrates. Results challenge the commonly held view that slowly decomposing leaves are “poor quality” by demonstrating that some traits that slow decomposition can disproportionately promote C and N transfer to higher trophic levels, whereas other traits associated with rapidly decomposing “high quality” litter supports microbial productivity. Our research highlights the complex ecological interactions between microbes and invertebrate shedders that encompass both competition and facilitation.