Responses of the structure and function of the understory plant communities to precipitation reduction across forest ecosystems in Germany

Abstract

& Key message Understory plant communities are essential for the recruitment of trees making up future forests. Independent of plant diversity, the understory across different forest ecosystems shows considerable physiological acclimation and structural stability towards drought events, which are expected to occur more frequently in future. & Context Understory plant communities are essential for the recruitment of trees making up the future forest. It is so far poorly understood how climate change will affect understory in beech and conifer forests managed at different intensity levels. & Aims We hypothesized that drought would affect transpiration and carbon isotope discrimination but not species richness and diversity. Moreover, we assumed that forest management intensity will modify the responses to drought of the understory community. & Methods We set up roofs in forests with a gradient of management intensities (unmanaged beech-managed beech-intensively managed conifer forests) in three regions across Germany. A drought event close to the 2003 drought was imposed in two consecutive years. & Results After 2 years, the realized precipitation reduction was between 27% and 34%. The averaged water content in the top 20 cm of the soil under the roof was reduced by 2% to 8% compared with the control. In the 1st year, leaf level transpiration was reduced for different functional groups, which scaled to community transpiration modified by additional effects of drought on functional group leaf area. Acclimation effects in most functional groups were observed in the 2nd year. & Conclusion Forest understory shows high plasticity at the leaf and community level, and high structural stability to changing climate conditions with drought events.

Understorey changes after an extreme drought event are modulated by overstorey tree species mixtures in thermophilous deciduous forests

“…In the study by Ozolinčius et al (2009), loss of ground cover was associated with a 20% decrease in also the Shannon index, while we found that the negative impact was on plot species richness but not on Shannon-diversity. These results support Felsmann et al (2018) who found a tendency for lower species richness vs. considerable stability in the structure (diversity and composition) of understorey community of beech and conifer forests exposed to drought treatments for 18 months. In that experiment diversity was not affected thanks to the high plasticity of understorey plants to moderate reduction of soil water content (Felsmann et al, 2018).…”

“…Although the many drivers of global change are known to affect in multiple and interactive ways this forest layer, the potential impacts of extreme climate events have been overlooked in the recent literature. Frequency and duration of drought and heat episodes are indeed among the potential drivers of direct and overstorey-mediated changes in the structure of understorey communities (Archaux and Wolters, 2006;Felsmann, et al, 2018). Since current climate projections predict strong reductions of summer precipitation and an increase in the occurrence of drought periods all over Europe (IPCC, 2012;, there is a need for interdisciplinary research initiatives on the short-term consequences of such events on forest biodiversity (Archaux and Wolters, 2006;Felsmann et al, 2018).…”

“…Acquiring a better knowledge about the responses of the understorey in monospecific and mixed stands in the face of heat and drought periods can inform forest management aiming at preserving ecosystem functionality. In fact, drought susceptibility of the understorey community might be affected by silvicultural practices which usually impacts on the overstorey in terms of number and composition of tree species (Felsmann et al, 2018).…”

Global BROOK90 R Package: An Automatic Framework to Simulate the Water Balance at Any Location

“…Overall, hydrologists recognize BROOK90 as a useful tool for studies of the water balance for small plots in mainly forested regions (i.e., from the most recent studies [25][26][27][28][29]). Therefore, it has been used in research, teaching, and water management, and also because of its ability to gain reasonable results even under changing climate conditions [20].…”

Factors Affecting Natural Regeneration of Tropical Forests across a Precipitation Gradient in Myanmar

“…A reduction in precipitation, especially drought, can limit the regeneration potential and composition of plants because almost all species are very susceptible to environmental factors at the seedling stages [8,13,14]. Osem et al [12] reported that species composition at regeneration stages varied in regions with an annual rainfall of 300 to 900 mm.…”