B092-0006
Effects of genetic variation and disturbance legacy of trembling aspen on soil microbial function

Tuesday, 15 December 2020
Poster
Olivia Lopez1, Chase Scott Kasmerchak1, Erika Marin-Spiotta2, Richard Lindroth3, Eric L Kruger4, Nicholas Pomplun5 and Chastin Harlow6, (1)University of Wisconsin Madison, Geography, Madison, WI, United States, (2)University of Wisconsin Madison, Madison, WI, United States, (3)University of Wisconsin Madison, Department of Entomology, Madison, WI, United States, (4)University of Wisconsin-Madison, Department of Forest and Wildlife Ecology, Madison, WI, United States, (5)University of Wisconsin-Madison, Madison, United States, (6)University of Wisconsin Madison, Madison, United States
Abstract:
Effects of genetic variation and disturbance legacy of trembling aspen on soil microbial function

Forest fragmentation due to human activity has altered the genetic diversity of plants, both among and within species, by generating selective pressure or random changes in the frequency of different genotypes. Plant community composition plays an important role in ecosystem functions mediated by soil microorganisms, but little is known about how genetic variation within species affects these processes. This research examines how genetic variation in trembling aspen (Populus tremuloides) influences soil microbial activity and nutrient cycling in an experimental forest in southern Wisconsin. At our site, there are 14 genotypes represented within 18 populations. Previous research at these sites showed strong differences in secondary plant chemistry between the genotypes, particularly condensed tannin (CT) contents. Shortly after establishment, half of the sites were subjected to a thinning treatment to mimic an intermediate disturbance and decrease resource competition among trees. Since thinning, there has been a clear divergence in genotypic diversity, canopy chemistry, and tree growth rates between treatments. Our results show that thinned stands had ≈12-20% greater rates of nitrogen mineralization and nitrification than unthinned stands (both p < 0.05), although there was considerable variation among plots within the same treatment. A 11-day laboratory litter addition experiment showed that thinned stands had 22-27% greater cumulative microbial respiration than unthinned stands, with greater CO2 respired per gram of soil per day when high CT litter was added, although neither result is statistically significant. Our soil-only jars with no added litter showed the opposite, with unthinned soils respiring more than twice as much CO2 as thinned soils (p < 0.05). We expect a longer laboratory experiment and an upcoming 18-month field experiment to reveal significant effects of litter chemistry (high vs low CTs and C:N ratios) and soil disturbance legacy (thinned vs unthinned) on litter decomposition. Our results will provide insight on how ecosystem disturbance affects genetic diversity, microbially-mediated functions, and carbon storage in soils.

<< Previous Abstract | Next Abstract >>