Shifts in plant functional community composition under hydrological stress strongly decelerate litter decomposition. Issue 12 (29th April 2020)

• Record Type: Journal Article
• Authors: Walter, Julia; Buchmann, Carsten M.; Schurr, Frank M.
• Is Part Of: Ecology and evolution. Volume 10:Issue 12(2020)
• Page Start: 5712
• Page End: 5724
• Publication Date: 2020-04-29
• Subjects: biomass‐ratio hypothesis -- community‐weighted mean functional traits -- drought -- effect traits -- functional diversity -- litterbag -- niche‐complementarity hypothesis -- pulsed stress -- response; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.6310
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Litter decomposition is a key process of nutrient and carbon cycling in terrestrial ecosystems. The decomposition process will likely be altered under ongoing climate change, both through direct effects on decomposer activity and through indirect effects caused by changes in litter quality. We studied how hydrological change indirectly affects decomposition via plant functional community restructuring caused by changes in plant species' relative abundances (community‐weighted mean (CWM) traits and functional diversity). We further assessed how those indirect litter quality effects compare to direct effects. We set up a mesocosm experiment, in which sown grassland communities and natural turf pieces were subjected to different hydrological conditions (dryness and waterlogging) for two growing seasons. Species‐level mean traits were obtained from trait databases and combined with species' relative abundances to assess functional community restructuring. We studied decomposition of mixed litter from these communities in a common "litterbed." These indirect effects were compared to effects of different hydrological conditions on soil respiration and on decomposition of standard litter (direct effects). Dryness reduced biomass production in sown communities and natural turf pieces, while waterlogging only reduced biomass in sown communities. Hydrological stress caused profound shifts in species' abundances and consequently in plant functional community composition. Hydrologically stressed communities had higher CMW leaf dry matter content, lower CMW leaf nitrogen content, and lower functional diversity. Lower CWM leaf N content and functional diversity were strongly related to slower decomposition. These indirect effects paralleled direct effects, but were larger and longer‐lasting. Species mean traits from trait databases had therefore considerable predictive power for decomposition. Our results show that stressful soil moisture conditions, that are likely to occur more frequently in the future, quickly shift species' abundances. The resulting functional community restructuring will decelerate decomposition under hydrological stress. Abstract : We show for the first time not only that community‐weighted mean functional traits and functional diversity rapidly change under hydrological stress (dryness and waterlogging), but also that these shifts strongly decelerate litter decomposition. These indirect effects on litter decomposition via changes in litter quality parallel direct effects on decomposer activity, but are even larger in magnitude and last longer. To our knowledge, this is the first study showing a link between effects of hydrological conditions on functional community structure with consequences for an ecosystem process, such as litter decomposition.