Light accelerates plant responses to warming

Abstract

Competition for light has profound effects on plant performance in virtually all terrestrial ecosystems. Nowhere is this more evident than in forests, where trees create environmental heterogeneity that shapes the dynamics of forest-floor communities(1-3). Observational evidence suggests that biotic responses to both anthropogenic global warming and nitrogen pollution may be attenuated by the shading effects of trees and shrubs(4-9). Here we show experimentally that tree shade is slowing down changes in below-canopy communities due to warming. We manipulated levels of photosynthetically active radiation, temperature and nitrogen, alone and in combination, in a temperate forest understorey over a 3-year period, and monitored the composition of the understorey community. Light addition, but not nitrogen enrichment, accelerated directional plant community responses to warming, increasing the dominance of warmth-preferring taxa over cold-tolerant plants (a process described as thermophilization(6,10-12)). Tall, competitive plants took greatest advantage of the combination of elevated temperature and light. Warming of the forest floor did not result in strong community thermophilization unless light was also increased. Our findings suggest that the maintenance of locally closed canopy conditions could reduce, at least temporarily, warming-induced changes in forest floor plant communities.

Cascading effects of canopy mortality drive long‐term changes in understorey diversity in temperate old‐growth forests of Europe

“…Long‐term nitrogen deposition and ongoing climate change may have also contributed to the diversity declines (Scheffers et al., ; Stevens, Dise, Mountford, & Gowing, ), but there was no clear pattern for these drivers based on the Ellenberg indicator values. Several other studies have documented that loss of light from canopy shading overrides the influence of nitrogen deposition and climate warming on understorey communities (De Frenne et al., , ; Helm, Essl, Mirtl, & Dirnböck, ; Verheyen et al., , ). We suspect that this has likely been the case in this study as well.…”

Ecosystem Services from Small Forest Patches in Agricultural Landscapes

“…vegetation-cover effect in [100]) may be partly responsible for the buffering effect on warming-induced community composition changes that have been reported in lowland forests [102,103]. Coherently, it has been demonstrated through a manipulative experiment that light accelerates warminginduced changes in understory plant communities [104]. Given these recent findings, we argue that SFP have a strong potential to provide climatic refugia (cf.…”

Drivers of treeline shift in different European mountains

“…This disparity is widely discussed and assigned to the great variety of non-climatic factors or even tree ontogeny (Grytnes et al 2014, Lenoir & Svenning 2015, Máliš et al 2016. Disturbances leading to tree mortality may also play an important role (Cudlín et al 2013); changes in tree canopy cover modify light availability and microclimate and can induce the thermophilization of forest vegetation (De Frenne et al 2015, Stevens et al 2015. The loss of this microclimate buffering effect of forests may induce a biotic homogenization of forests (Savage & Vellend 2015) or the creation of novel non-analogical communities, such as oak−pine forests (Urban et al 2012), which may be a new threat to forest biodiversity.…”