Student-Faculty Collaborative Research Grant Report

Carbon and nutrients stored in fallen trees represent large pools of stored nutrients in forest ecosystems. These nutrients are slowly released to the forest system as the tree is decomposed. Understanding the process of decomposition would yield insights into how these nutrient pools behave and how they are maintained. The main decomposers are bacteria and fungi, but data on the specific species involved, the relative ratio of bacterial to fungal species, and the timing of invasion by these groups is largely unknown for specific forest types and specific tree species. Our plan is to use molecular techniques to identify all species involved in decomposition in a northern hardwood forest at the University of Michigan’s Biological Station. We collected samples across a series of trees representing the time course from standing dead trees to nearly completely decomposed trees on the forest floor. In this way we will learn about the process across a time sequence. We used a drill to core into the wood and collect samples; a total of 30 samples were collected including three from surrounding soil. From these samples we extracted total genomic DNA. This DNA was used as a substrate to amplify diagnostic regions of fungal and bacterial species. From the collected samples we had collaborators run C:N ratio analysis and enzyme analysis. Once we had amplified our target regions, samples were sent out for DNA sequencing; all sequencing is now complete. In late October our sequencing was complete and we have begun to analyze our now complete data sets. From our preliminary work it appears as if all samples were sequenced completely and at significant depth. A BLAST search of recovered sequences has identified over 7000 fungal species and over 4500 bacterial species present in these samples. These are not all decomposers and they are not all present in the same concentration. Our work is now to uncover which are the predominant decomposers and how frequent they are across each of the decay classes we sampled. Analysis is ongoing, but will pick up in the spring term