Dr. Monica G.Turner
Department of Integrative Biology
University of Wisconsin
430 Lincoln Dr.
Madison, WI 53706
Ecosystem and
Landscape Ecology Lab
 

The influence of climate and logging on native forest herbs and their pollinators in the Southern Appalachians

Contacts

Michelle Jackson, Monica Turner, Scott Pearson

Project Summary

The conservation of biodiversity in the face of global change requires understanding the interactions among multiple drivers.  Land-use history and climate warming can both result in significant shifts in the distribution and performance of native plant populations and contribute to the current decline in their pollinators.  My research addresses the influence of clear-cut logging and climate variability on the distribution, performance, and pollination ecology of native forest herbs in the Southern Appalachians. To assess performance of forest herbs, we have taken measurements related to biomass and life history stage for individuals of 5 focal species in 20 plots across gradients of stand age (time since harvest) and elevation (proxy for climate) in 2009, 2010 and 2011.  We also sowed seeds in the same plots for 6 species of forest herbs in order to determine whether the same environmental and climate characteristics affect germination.

I am also studying pollination ecology of forest herbs using insect trapping (“bee bowls”) and pollen supplement experiments.  In summer 2010 and spring 2011, I collected forest insects in plastic bowls at different distances from logging roads in 16 sites spanning a gradient of elevation and stand age.  I hypothesize that the pollinator community will differ along an elevation gradient and in old versus recently-logged forests, and that pollinators will be more abundant closer to logging roads where the canopy is more open.  To assess the amount of pollen limitation experienced by two species of forest herbs, I have conducted a pollen supplement experiment with Trillium grandiflorum and Prosartes lanuginosum.  Within 12 sites (6 old and 6 recent), I identified populations of these species and 20 plants/site were supplemented with pollen, 20 were blocked from natural pollination using mesh bags, and 20 were left open to natural pollination.  If plants are pollen-limited and cannot self-fertilize, individuals in the blocked treatment should produce no seeds, and individuals supplemented with pollen should produce more seeds than those in the control and blocked treatments.  Results from this study will be useful for assessing the impacts of clear-cut logging on forest understory herbs and their pollinators in the face of a changing climate.

Key Findings

We are using mixed effects linear modeling, Redundancy Analysis (RDA), and Lefkovitch stage-based life table analyses to assess the effects of elevation, stand age, and other environmental variables on the performance and germination of these species. Preliminary analyses show that across years, young forests were associated with lower recruitment, higher within-plot variability in recruitment, higher mortality, and higher leaf area-to-stem ratios (three species), lower densities (two species), and reduced flowering (one species).  Growth varied among species and with stand age during the dry spring, but was unaffected by stand age during the wet spring, indicating that plant growth may be more sensitive to land-use history during periods of drought. Mortality was higher for all species following the dry year and at higher temperatures for three species across both stand ages.  Our results suggest that land-use legacies such as timber harvesting may negatively affect plant performance at various life-stages, and that performance measures can be valuable indicators of a population’s ability to persist and recover following disturbance.

Selected Publications

In preparation
Gooch, M.M., Turner, M.G., Ives, A.R., and S.M. Pearson. Seeing the forest and the trees:
multilevel models predict both species and community patterns.

Gooch, M.M., Turner, M.G., and S.M. Pearson. Climate and logging history influence native forest herb performance in the Southern Appalachians.

Acknowledgements

These studies are being funded by a grant from the Coweeta Long Term Ecological Research program (LTER) and supplemental grants from the Department of Zoology, University of Wisconsin-Madison.