Direct and indirect effects of native range expansion on soil microbial community structure and function

Abstract

Summary1. Analogous to the spread of non-native species, shifts in native species' ranges resulting from climate and land use change are also creating new combinations of species in many ecosystems. These native range shifts may be facilitated by similar mechanisms that provide advantages for non-native species and may also have comparable impacts on the ecosystems they invade. 2. Soil biota, in particular bacteria and fungi, are important regulators of plant community composition and below-ground ecosystem function. Compared to non-native plant invasions, there have been relatively few studies examining how soil biota influence -or are influenced by -native species range shifts. 3. Here, we examined how a native range-expanding sagebrush species (Artemisia rothrockii) affects below-ground abiotic conditions and microbial community structure and function using next-generation sequencing coupled with other biotic and abiotic soil analyses. We utilized a range-expansion gradient, together with a shrub removal experiment and structural equation models, to determine the direct and indirect drivers of these interconnected processes. 4. Sagebrush colonization increased bacterial and archaeal richness and diversity and altered community composition across the expansion gradient. Soil organic C and N and soil moisture increased with sagebrush presence; however, results varied across the expansion gradient. We found no relationship between sagebrush and soil pH; however, pH strongly influenced microbial richness and diversity. Microbial (substrate-induced) respiration was influenced by soil organic N, as well as microbial diversity and functional group relative abundances, highlighting direct and indirect effects of sagebrush on microbial community structure and function. Microbial community composition of soils after 4 years of sagebrush removal was more similar to communities in shrub interspaces than underneath shrubs, suggesting microbial community resilience. 5. Synthesis. Our results suggest that native range expansions can have important impacts on soil biological communities, soil chemistry and hydrology which can further impact below-ground ecosystem processes such as nutrient cycling and litter decomposition. The combination of highthroughput sequencing and structural equation modelling used here offers an exciting yet underutilized approach to understanding how both native and non-native species' range expansions may affect the structure and function of soil ecosystems.

Plant-soil interactions of range-expanding plants

“…Many field studies on plant invasions and soil communities have shown that exotic plant species have distinct soil communities compared to native plants growing in adjacent areas (Kourtev et al 2002a, Kourtev et al 2002b, Scharfy et al 2009, Collins et al 2016, Stefanowicz et al 2016, Gibbons et al 2017. Consistent with these results, in our experiment we also observe that the composition of the rhizosphere bacterial community differed by plant origin in all four plant pairs when plants were grown in their own field soils ( Fig.…”

Soil microbial restoration strategies for promoting climate‐ready prairie ecosystems

“…Copiotrophic phyla adapted for rapid growth and higher potential for labile carbon metabolism in high nutrient conditions are Betaproteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. Oligotrophic phyla adapted for slow growth and higher potential for carbon storage are Acidobacteria and Verrucomicrobia (Fierer et al 2007, Collins et al 2016. Other phyla cannot be categorized into either group.…”

“…For example, nitrogen fertilization causes a consistent decrease in soil bacterial diversity and microbial biomass carbon, independent of nitrogen application rates or crop types (Dai et al 2018). Nitrogen fertilization is also related to increased relative abundances of Proteobacteria and Actinobacteria (Ramirez et al 2010, Zhou et al 2017, Dai et al 2018, which include taxa that are adapted to high nitrogen demand and labile carbon pool metabolism (Fierer et al 2007, Collins et al 2016. Conversely, in North American remnant prairies, where plant organic material inputs control the growth of these copiotrophic taxa, Verrucomicrobia, which are thought to specialize in recalcitrant carbon degradation, are more predominant members of the community (Fierer et al 2013).…”

Plant community response to Artemisia rothrockii (sagebrush) encroachment and removal along an arid elevational gradient

“…Consistent with Grime's (, ) concept that community biomass is inversely proportional to plant stress, intermediate elevations had the highest plant cover and biomass (Figure , Table ), and therefore the lowest net impact of abiotic and resource stress. However, high elevations also have higher soil moisture, soil organic C and N, as well as microbial biomass and activity than lower elevations (Collins, Carey, Aronson, Kopp, & Diez, ), suggesting higher resource stress at low elevations. Further, while Callaway et al.…”