Invasive plants decrease soil microbial activity compared to native grassland communities
June 30, 2017 10:35 am Leave a Comment
Two invasive grasses reduce inorganic nitrate availability, active microbial biomass, and the potential for soil communities to nitrify and denitrify compared to native plant communities in California.
These results may help explain why it is difficult to establish native grasses on soils that have been invaded by invasive annual grasses.
, , , , Invasive plants decrease microbial capacity to nitrify and denitrify compared to native California grassland communities. Biol Invasions DOI 10.1007/s10530-017-1497-y Accepted: 26 June 2017
*Dr. Carey is a Point Blue Senior Soil Scientist
Abstract: Exotic plant inva sions are a major driver of global environmental change that can signi ﬁ ca ntly alter the availabili ty of limit ing nutrients such as nitrogen (N). Beginning with European colonization of California, native g rasslands were replace d almost entirely by annual exot ic grasses, many of which are now so ubiquitous that they are considered part of the regional ﬂ ora (‘ ‘naturalized’ ’). A new wav e of inva sive plants, such as Ae gilops triunci alis (Barb goatgrass) and Elymus caput – medusae (Med usahead), continue to spread throughout the state today. To determ ine whether these new -wave invasive plan ts alter soil N dynamics, we measured inorg anic N pools , nitri ﬁ cation and deni tri ﬁ cation potentials, and possible mediating factors such as microbial biomass and soil pH in experimental grasslands comprised of A. triuncial is and E. caput – medusae . We compared these measure-
ments with those from exper imental grasslands containing: (1) native annuals and perennials and (2) naturalized exotic annuals. We found that A. triun cialis and E. caput – medusae signi ﬁ cantly reduced ion- exchange resin estim ates of nitrate (N O3) availa bility as well as nitri ﬁ cat ion and denitri ﬁ cati on pote ntials compared to native communities. Active microbial biomass was als o lower in invaded soils. In contrast, potential measur ements of nitri ﬁ cation and denitr i ﬁ cation were similar between invaded and naturalized communitie s. These results suggest that invasion by A. triuncialis and E. caput – medusae may signi ﬁ ca ntly alter the capacity for soil microbial communities to nitrify or deni trify, and by extension alter soil N availability and rates of N transformat ions during
invasion of remnant native-dom inated sites.
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