Abstract
AbstractWoody plant encroachment affects dry grasslands globally. To predict changes in biodiversity and ecosystem processes, it is important to understand how this process affects the functional composition of grassland organism groups. In this context, seminatural wooded meadows represent a form of experimental manipulation—where open grassland and woody patches co‐occur in homogeneous environmental conditions due to human management decisions—which provides an opportunity to address the effect of woody plant encroachment on vegetation and soil biota. We used environmental DNA metabarcoding to address variation in plant, soil fungal, and soil animal communities in parallel. We also addressed functional groups of fungi—animal and plant pathogens, saprotrophs, decomposers, arbuscular mycorrhizal, ectomycorrhizal, endophytic, and other symbiotrophic fungi—and of soil animals—fungivores, bacterivores, litter feeders, root feeders, macro plant feeders, algal/lichen feeders, predators, and parasites. Co‐variation between communities was detected from aboveground vegetation plots and metabarcoding of soil DNA, in terms of estimated richness and compositional patterns. Differences between open and wooded patches were most pronounced among plants and symbiotic fungi, whereas soil animals exhibited less marked differences. For most organisms, mean richness, as well as total richness per habitat type, was higher in open than wooded patches, but ectomycorrhizal fungi exhibited the opposite pattern. The functional structure of the soil biotic community, as characterized by the proportion of DNA sequences attributed to different functional groups, differed significantly between open and wooded grassland patches, with symbiotic fungi (arbuscular mycorrhizal, ectomycorrhizal, and other symbiotrophic [mostly orchid mycorrhizal] fungi) contributing most to the difference. This study supports the notion that a soil DNA‐based metabarcoding approach can provide insights into the diversity and composition of multiple taxonomic groups in natural ecosystems. It also provides a first demonstration of the complex changes to the functional structure of the belowground community that accompany woody plant encroachment in grasslands.
Highlights
Increasing woody plant encroachment is occurring globally as a result of changing climate and land use (Eldridge et al 2011, Archer et al 2017)
For data aggregated to the functional group level, we used two parallel approaches for testing compositional differences: (1) using the number of sequences belonging to each functional group in a sample and (2) using the number of taxa belonging to a functional group in a sample
Using plant DNA sequences from soil, a similar pattern was detected, with wooded and open patches differing in mean richness and community composition (PERMANOVA R2 = 0.44, P = 0.002)
Summary
Increasing woody plant encroachment is occurring globally as a result of changing climate and land use (Eldridge et al 2011, Archer et al 2017). In central and northern Europe, woody encroachment is common in seminatural grasslands (Eriksson et al 2002). These grasslands represent ecosystems that have developed and persisted within a natural forest biome due to historical and continuing human activities, including animal husbandry, mowing, and collection of firewood (Poschlod and WallisDeVries 2002). Wooded meadows represent a specific type of seminatural grassland where groups of trees and shrubs have historically been retained, usually to provide a supply of firewood (Kukk and Kull 1997) Such meadows provide an anthropogenic experimental setting for studying the potential effects of woody plant encroachment on local biota, because the presence and location of woody plants have been determined by human management decisions in an otherwise largely uniform habitat
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