CAN TRACE FOSSILS OF ROCK-EATING FUNGI BE USED TO GUIDE FOREST RESTORATION IN CENTRAL APPALACHIA?

The existing habitat of red spruce (Picea rubens) within the high elevation mountains of West Virginia has been significantly reduced due to past intensive logging. Efforts are now being made to restore spruce habitat within its historic extent. Red spruce and other gymnosperms form symbiotic relationships with ecto-mycorrhizal fungus (EcM) species, enabling greater access to nutrients for the host plant. It has been documented that EcM can tunnel into sand- and silt-sized grains of feldspar, contributing to the weathering process and nutrient acquisition in a nutrient limited environment—and leaving behind distinctive micropores in the mineral grains. These trace fossils of past EcM tunneling may be useful as an indicator to identify and delineate historic red spruce habitat and, therefore, potential restoration sites. We looked for presence of EcM tunneling in the high elevation Spodosols of West Virginia and similar USDA-NRCS samples from around the United States for reference. Thin sections were made from eluvial horizons, representing Spodosols from various regions, and were examined with optical petrography to identify EcM fungi tunnels in feldspars. The tunnels created by EcM fungi are 5-15 μm wide, non-linear, branching, smooth, and ellipsoidal at the tip. Tunnels cross cleavage planes, and may run through the whole length of the feldspar grain. Photographs depicting tunneled minerals were taken for each thin section. The intensity of weathering and frequency of tunneling were compared to the soil and site characteristics of the sample locations to find possible relationships. Out of 18 total NRCS samples, eight pedons were found to exhibit mycorrhizal tunneling with various degrees of hyphal weathering. All pedons containing hyphal weathering were associated with coniferous and/or ericaceous vegetation, including red spruce. The West Virginia thin sections showed inconclusive results, displaying little feldspar and intensively weathered quartz. Continuing work is focusing on more analyses of West Virginia soils. The documented tunnels in feldspar from other samples suggest a trace fossil resulting from fungal processes unique to subalpine coniferous communities.