Effects of Non-Native Plants On Soil Microbial Communities.

If the litter of non-native, invasive plants differs in its chemical composition to native species, then invasion may irreparably alter the soil microbial community beneath them.  The objective of this study is to examine the impact invasive plants have on the soil environment by testing the effect various carbon (C) additions have on soil microorganisms and soil C quality.  In situ soil rings (8 cm in diameter) will be identified in a forest understory plot under native plant cover (e.g., Cornus sp. or Prunus virginiana).  Subsets of soil rings will receive the following aqueous treatments: deionized water, dextrose (i.e., a labile C source), cellulose (a moderately labile C source), an extract of native plant material, and an extract of invasive plant material (Rhamnus cathartica, a common exotic in Wisconsin forests; n = 24).  Soil cores (1.75 cm in diameter and 10 cm deep) from each subset (n = 6) will be collected prior to treatment and 2, 4, and 6 weeks after treatment and analyzed for soil physical/chemical properties, microbial biomass C (MBC),  labile C, recalcitrant C, and total C.  Plant litter from both native and invasive species will also be analyzed for lignin and cellulose content.  Results from this study will assess the impact litter from invasive species has on available carbon pools and in turn microorganism abundance.  We hypothesize that the dextrose and invasive plant treatments will have significantly higher MBC and that a correlation between labile C and MBC will be the main driver causing this increase.