Landscape‐scale vegetation homogenization in Central European sub‐montane forests over the past 50 years

Abstract

Questions: How did plant species richness and spatial heterogeneity of the vegetation change across sub-montane forests over the past 50 years? Did the vegetation changes reflect eutrophication, acidification and management changes, which the area underwent during the second half of the 20th century?Location: Ordinary managed forests sampled across 2500 km 2 of a typical Central European sub-montane landscape in the southern part of the Czech Republic. Methods:We resampled 156 quasi-permanent plots sampled in the 1950s-1970s and covering the whole range of forest vegetation in the region. We compared understorey plant species richness and community composition between the surveys and tested for temporal changes in the spatial heterogeneity (β-diversity) of vegetation.Results: Species richness and dissimilarity in species composition among plots decreased significantly between the surveys. The vegetation of the plots also changed significantly, but there were no clear directional changes across all plots. The vegetation homogenization was driven by local extinctions of specialist species, especially competitively weak species adapted to nutrient-poor conditions. Few generalist species expanded between the surveys. Conclusions:We found evidence of taxonomic homogenization of forest understoreys across a large sub-montane region. This vegetation homogenization was probably driven by complex landscape changes that took place in the last century. Varied traditional management regimes were replaced with largely uniform management, and the once spatially diverse landscape mosaic has become simpler. The resulting transition to species-poor and less variable vegetation was probably further accelerated by environmental eutrophication. Our results thus complement previous forest herb layer resurveys, which focused mostly on lowland forests and small nature reserves, and suggest that landscape-scale taxonomic homogenization is occurring across Central European forests. K E Y W O R D Sbeta diversity, biotic homogenization, eutrophication, forest understorey, landscape change, semi-permanent plots, species richness, temperate forests, vegetation resurvey 374 |

Historical charcoal burning and coppicing suppressed beech and increased forest vegetation heterogeneity

“…Indeed, our results support the hypothesis that the historical management created and maintained small-scale vegetation heterogeneity in temperate lowland forests (Kopecký et al, 2013). This small-scale heterogeneity was probably maintained by highly variable management, often applied with different intensity in space and time (Gimmi et al, 2008;Prach and Kopecký, 2018).…”

“…Spatial heterogeneity in understorey species composition significantly decreased between the surveys. This taxonomic homogenisation was reported also from other regions in temperate Europe (Keith et al, 2009;Heinrichs and Schmidt, 2017;Prach and Kopecký, 2018) and suggests a more general trend. Indeed, our results support the hypothesis that the historical management created and maintained small-scale vegetation heterogeneity in temperate lowland forests (Kopecký et al, 2013).…”

Site fertility drives temporal turnover of vegetation at high latitudes

“…We emphasize that changes in overstorey structure, insect outbreaks, or reindeer grazing likely underlie the observed local changes in communities and interplay with recent climatic changes. Essentially, as has been observed elsewhere (Bernhardt-Römermann et al, 2015;Hédl, Kopecký, & Komárek, 2010;Prach & Kopecký, 2018), these nonclimatic drivers may explain some of the most evident "anomalies" in vegetation changes. In addition, compositional shifts within vegetation types can be highly variable in different geographic contexts in general (see, for example, Maliniemi, Kapfer, Saccone, Skog, & Virtanen, 2018).…”

Taxonomic, phylogenetic and functional diversity of understorey plants respond differently to environmental conditions in European forest edges

“…During the past century, herbaceous understorey plant communities homogenised by an increasing presence of nutrient-demanding and shade-tolerant species (Keith et al, 2009;Naaf & Wulf, 2010;Prach & Kopecky, 2018;Staude et al, 2020;Van den Berge et al, 2019).…”

“…However, if a limited set of taxa replaces many different species across the forest biome, homogenisation can lead to losses of total biodiversity on the scale of the forest biome, even though locally no decline in species richness is registered (Staude et al., 2020). During the past century, herbaceous understorey plant communities homogenised by an increasing presence of nutrient‐demanding and shade‐tolerant species (Keith et al., 2009; Naaf & Wulf, 2010; Prach & Kopecky, 2018; Staude et al., 2020; Van den Berge et al., 2019). Simultaneously, climate change causes an increasing dominance of warm‐adapted species in understorey communities, a process referred to as thermophilisation (Bertrand et al., 2011; De Frenne et al., 2013; Zellweger et al., 2020).…”