Tree community composition stabilizes ecosystem functions in response to drought

Abstract

In summer 2018, Central Europe was hit by an extreme drought event that widely impacted ecosystems and markedly increased tree mortality in forest ecosystems across the continent. As climate models predict an increase in frequency and severity of such events, there is an urgent need to adapt forests in order to maintain the diverse benefits they provide. Soil processes play an essential role in this context and are key for a plethora of terrestrial ecosystem functions, but they are strongly dependent on water availability. Here, we investigated how tree species richness (TSR), composition, and identity in a 13‐year‐old temperate tree diversity experiment influenced selected ecosystem functions (as important representatives of different ecosystem processes) during the 2018 summer drought. We focused on the stability of soil microbial biomass and standard litter decomposition, as well as tree species‐specific mortality rates. Contrary to our expectations, TSR did not generally increase the resistance of soil functions or decrease tree mortality rates. However, the resistance of these functions was determined by tree species identity and community composition. For the resistance of both soil functions (microbial biomass and litter decomposition), we found that TSR effects depended on the presence of certain tree species. Moreover, we found that the performance of a specific tree species in monoculture, Norway spruce, was a poor predictor of its response to drought in tree species mixtures. Taken together, the results of our study demonstrate that the species composition of tree stands determines tree mortality and the resistance of soil functions under drought. This indicates that enhancing multiple ecosystem functions under environmental disturbance requires maintaining diverse forests.

Seasonal shifts in plant diversity effects on aboveground-belowground phenological synchrony

“…Plant diversity continuously enhanced detritivore feeding activity during spring and summer, but only functional group effects were observed in winter. Altogether, these results demonstrate that an accurate depiction of winter activity is required for a mechanistic description of temporal niche dispersion and biodiversity effects on ecosystem functioning (Gottschall et al, 2022).…”

Field experiments have enhanced our understanding of drought impacts on terrestrial ecosystems—But where do we go from here?

“…Similarly, numerous studies show that drought alters plant community diversity in many ways (genetic, species, functional and growth form). These studies often infer that plant community attributes, before and after drought, mediate drought sensitivity (Batbaatar et al, 2022;Gottschall et al, 2023;Harrison et al, 2018;Korell et al, 2021;Liu, Wang, et al, 2022;Mackie et al, 2019;Peñuelas et al, 2007;Shaw et al, 2022;Tilman & El Haddi, 1992;Van Ruijven & Berendse, 2010). Some experiments have explicitly tested for interactions between various components of biodiversity and drought via the independent manipulation of both (e.g.…”