Effect of Plant Invasive Species on the Composition of Soil Organic Matter.

Invasive plants may cause significant alterations to many aspects of soil ecosystem functioning, including nutrient cycling and microbial community structure. The composition and stabilization of soil organic matter (SOM) may also be influenced by the invasion of exotic species, primarily due to the deposition of different amounts of chemically distinct litter compared to the host plant species. In this study, we will examine the effect of plant invasive species on the chemical speciation of SOM in a rough fescue (Festuca altaica Trin.) grassland invaded by smooth brome grass (Bromus inermis Leyss) in Central Saskatchewan, Canada. The stratified random sampling design was used to collect soil samples from 60 locations with different degrees of smooth brome grass abundance (0, >0-50, 51-85, and >85%) within the field site. Samples were collected from the A and B soil horizons, and composited, for a total of 550 samples collected over the 26-week period. Spectroscopic analysis of the finely-ground soil samples was performed using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to understand how soil organic matter changes upon brome invasion. The FTIR spectra will be deconvoluted by using the Gaussian curve fitting technique, to determine the functional group composition of SOM at varying degrees of smooth brome grass invasion. This study will provide an insight into the effect of plant invasive species on the molecular chemistry of SOM, and thus, their influence on the dynamics and stabilization of SOM in the invaded ecosystems.