Linear and non-linear impacts of a non-native plant invasion on soil microbial community structure and function

Abstract

Biological invasions can alter ecosystem functions such as litter decomposition and nutrient cycling, but little is known about how invader abundance influences the impact on the ecosystem. It is often assumed that impacts are proportional to invasion density, but this assumption has never been tested and has little justification. We tested the hypothesis that the microbial community structure and function of a mixed hardwood forest soil changed after invasion by Japanese barberry (Berberis thunbergii), an invasive shrub commonly found in eastern hardwood forests, and that changes were proportional to the density of invasion. We constructed microcosms with mixtures of native and invasive leaf litter, and measured microbial community structure (phospholipid fatty acids) and function (litter decomposition). Decomposition was linearly related to the degree of invasion (R 2 = 0.945), but the ratio of bacteria to fungi exhibited a strongly non-linear, threshold response (R 2 = 0.513). These results indicate that impacts of Japanese barberry invasion are not always proportional to invasion density. This finding has implications for the study of biological invasions as well as practical implications for the management of exotic invasive species.

Invasive N-fixer Impacts on Litter Decomposition Driven by Changes to Soil Properties Not Litter Quality

“…This may be because the additional inorganic N added to the soil at low broom density levels is rapidly acquired by co-occurring species. These findings imply that low levels of N-fixing invader density may have disproportionately large impacts on co-occurring species traits, in line with findings from other studies (Peltzer and others 2009;Elgersma and Ehrenfeld 2011). Native and exotic grass species responded in broadly similar ways to broom density, with the native grass P. colensoi showing a higher decomposition rate than the two exotic species in the reciprocal transplant experiment, contrary to our expectations.…”

“…Many of the relationships between invader density and various ecosystem properties were nonlinear, in line with other recent studies (Dickie and others 2011;Elgersma and Ehrenfeld 2011), strongly contradicting the current widespread assumption that invasive plant impacts are proportional to invader density (Parker and others 1999;Yokomizo and others 2009). This underlines the need to move away from end-point comparisons of invasive species abundance towards gradient analyses.…”

Gradualism in Acacia dealbata Link invasion: Impact on soil chemistry and microbial community over a chronological sequence

“…However, plant invasions can modify soil structure and chemical composition (Ehrenfeld, 2003;Reinhart and Callaway, 2006;Chac on et al, 2009;Yang et al, 2010;Castro-Díez et al, 2012;Novoa et al, 2014) and soil microorganism structure (Hawkes et al, 2006;Broz et al, 2007;Lorenzo et al, 2010a) and function Dasonville et al, 2011;Elgersma and Ehrenfeld, 2011). Recently, authors such as Dasonville et al (2011) asserted that alien plant species can create novel niches by modifying native conditions; mainly in the storage and release of C and N. The presence of plant invaders generally modifies ecosystem litter inputs, both quantitatively and qualitatively (Ehrenfeld, 2010).…”

Changes in soil microbial community and enzyme activity along an exotic plant Eupatorium adenophorum invasion in a Chinese secondary forest

“…An increasing number of studies have shown that exotic invasive plants can influence the abundance, composition and functioning of soil microbial communities [6][7][8][9][10][11][12][13]. Furthermore, these changes in soil communities usually promote the growth of invasive plants, yet inhibit native plant performance, mainly driven by the lack of soil pathogens to invasive plants in the new habitats [14,15], the preferential enrichment of microbial pathogens to native plants [16,17], or the inhibition of microbial mutualism with native plants [18][19][20].…”