Table 3.

Impact of selected environmental drivers on changes in ground layer species richness in temperate forests. Shown are exemplarily single-region studies and, per environmental driver, its estimated general importance based on multi-region resurvey studies.

Driver	Single-region vegetation resurveys (examples)	Direction of effect on species richness	Multi-region analyses
Increased forest management intensity	Økland et al. (2003) Li and Waller (2015) Kirby and Thomas (2000) Brunet et al. (1996) Decocq et al. (2004) Schmidt (2005) Van Calster et al. (2008) Hédl et al. (2010) Kopecký et al. (2013)	Negative Negative No effect Positive Positive Positive Positive Positive Positive	The most important factor driving understory vegetation composition (Paillet et al. 2010), may mask the effects of climate change (De Frenne et al. 2013), or nutrient deposition (Verheyen et al. 2012)
Increased N-deposition	Hédl (2004) Skrindo and Økland (2002) Bernhardt-Römermann et al. (2007)	Negative No effect Positive	Pre-survey levels of N deposition determine subsequent changes in biodiversity (Bernhardt-Römermann et al. 2015); actual N-deposition is less important than forest management (Verheyen et al. 2012); exceedance of critical loads favors N demanding species (Dirnböck et al. 2014)
Climate warming	Kirby et al. (2005) Heinrichs et al. (2012) Naaf and Wulf (2010, 2011) Savage and Vellend (2015)	Negative No effect Positive Positive	Buffering effects of canopy closure on increased dominance of warm-adapted species as a result of climate warming (De Frenne et al. 2013)