Prescribed Burning Effects on Jack Pine Seeds from High and Low Serotiny Regions: Microbial Interactions and Soil Properties.

Prescribed Burning Effects on Jack Pine Seeds from High and Low Serotiny Regions: Microbial Interactions and Soil Properties

Christina Kranz, Thea Whitman

            Wildfire has shaped Midwestern pine barren ecosystems for thousands of years. Midwestern pine barrens have undergone dramatic changes in land use and management practices, but the effects of burning on microbial populations and their interactions with the post-fire plant community are poorly understood. There is a known gradient of serotiny in Pinus banksiana Lamb. (Jack Pine) within the state of Wisconsin, where more serotinous trees are found in northern portions of the state and less serotinous trees are found in the central and southern portions of the state. This study investigated the effects of burning on P. banksiana germination, success, and associated soil microbial communities in a 6-month greenhouse trial. We asked: (1) How does burning affect P. banksiana seed germination rate and seedling success?  (2) Are the soil microbial communities associated with P. banksiana different in unburned soils vs. soils subjected to a prescribed burn vs. soils burned in the lab? The O and A horizons were collected from Coon Fork Barrens, Eau Claire County, WI before and after a prescribed fire, and used to pack pots for the greenhouse trial. Seeds were obtained from the state forester from northern (higher serotiny) and central (lower serotiny) regions of Wisconsin. We predicted that seeds from serotinous cones would have a higher germination rate and greater success in burned soils while the non-serotinous cones would have no preference for burned or unburned soil. Prescribed fires are generally lower severity, even compared to naturally occurring barrens fires. Thus, we expect that there will not be a significant change in the microbial community in unburned soils vs. those subjected to a prescribed burn; therefore, any effects on seedling success will not be driven by soil microbes. Collectively, our data will indicate how the biological and chemical properties of soils change after a prescribed fire and potential effects on pine barren P. banksiana re-establishment for future land management purposes.