Contrasting vegetation change (1974–2015) in hedgerows and forests in an intensively used agricultural landscape

Abstract

Questions: How did hedgerows and forests change in area between 1974 and 2015 and did hedgerows still show the same vegetation composition in 2015? To what degree did the vegetation change in hedgerows and how do these changes compare to changes in forests? What is the nature of the species that changed and, from these, can we make general inferences about possible drivers of change? Location: The countryside in the municipality of Turnhout, province of Antwerp, northern Belgium. Methods: Through a resurvey of 54 and 20 quasi-permanent plots in hedgerows and forests, respectively, we investigated shifts in the herb layer over the period 1974-2015. The plot-level mean Ellenberg Indicator Values (EIVs) were calculated and soil samples were taken in 2015. We compared diversity statistics and used used Generalized Linear Mixed-Effects Models (GLMMs) to detect trends in species richness (SR) and EIVs. Via a non-metric multidimensional scaling (NMDS) ordination based on the Sørensen dissimilarity, we compared shifts at the community level.Results: Our study shows severe, but opposite changes in SR in forests and hedgerows. In forests, SR declined and a homogenization occurred. The shifts in EIVs indicate that forest vegetation evolved to more shade-tolerant and nutrient-demanding species, likely due to eutrophication combined with natural forest succession. In hedgerows, SR significantly increased. The species pool became more diverse and more heterogeneous. Changes in EIVs suggest a change towards more lightdemanding species, possibly caused by fragmentation of the network, and towards species indicative for nutrient-rich habitats, benefiting from eutrophication. Conclusions:In general, SR in hedgerows is higher than in forests in our studied region, being a suitable habitat for a wide range of plant species in the countryside.However, the loss of almost 30% of the hedgerow habitat in 41 years confronts us with the challenge of protecting the hedgerow remnants, in the interest of agro-biodiversity. K E Y W O R D Sacidification, Ellenberg indicator values, eutrophication, hedgerows, historical plot data, resurvey, semi-permanent plots, small forests, species richness, temporal vegetation shift 270 | Applied Vegetation Science VAN DEN BERGE Et Al.

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).…”

“…Forest edges receive more atmospheric acidifying and eutrophying deposition (Devlaeminck et al., 2005; Wuyts et al., 2008) and have higher nitrogen and carbon stocks, compared to the interior (Meeussen et al., 2021; Remy et al., 2016). Therefore, the increasing proportion of forest edges might accelerate the current homogenisation of understorey plant communities, which is characterised by an increasing presence of nutrient‐demanding species (Staude et al., 2020; Van den Berge et al., 2019; Verheyen et al., 2012). Furthermore, forest edges are characterised by increased wind speeds and incoming solar radiation, resulting in more variable microclimates and drier soil conditions than forest interiors (Chen et al., 1999; Gehlhausen et al., 2000; Matlack, 1993).…”

Hedging against biodiversity loss: Forest herbs’ performance in hedgerows across temperate Europe

“…hedgerows and other linear woody habitats) are traditional components of agricultural landscapes across Europe (Baudry et al ., 2000), and have been repeatedly advocated as a tool for land managers to enhance habitat connectivity (Davies and Pullin, 2007). Indeed, a myriad of studies have shown that hedgerows may function as a refuge habitat or dispersal route for forest herbs among otherwise isolated forest fragments (Corbit et al ., 1999; Sitzia, 2007; Liira and Paal, 2013; Van Den Berge et al ., 2019). From this perspective, hedgerows may be crucial to the long‐term persistence of forest herbs in forest‐devoid agricultural landscapes.…”

Biomass increment and carbon sequestration in hedgerow-grown trees

“…They are subjected to more direct wind momentum load resulting in greater branch production (Zhou et al, 2011), wider anddeeper rooting (Cardinael et al, 2015;Gilman, 1989) and they benefit from agricultural residual inputs such as fertilizers, pesticides and irrigation (Cardinael et al, 2018). Moreover, the hedgerow microclimate is warmer and dryer during the growing season compared to a forest (Vanneste et al, 2020a;Wehling and Diekmann, 2009), and soils are often less acidic (Van Den Berge et al, 2019). And yet, to our knowledge, there is currently no study available on the trends in aboveground stem biomass increments and carbon storage of trees growing in hedgerow systems.…”