DOI: 10.5061/dryad.jm63xsj71
title: Data from: Shifts in plant functional community composition under hydrological stress strongly decelerate litter decomposition

description: 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
 traits (CWM) 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,
 waterlogging) for two growing seasons. Species-level mean traits were
 obtained from trait data bases 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 data bases 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 shifts
 species´ abundances. The resulting functional community restructuring will
 decelerate decomposition under hydrological stress.
description: Most data were collected in an experimental mesocosm approach.
 Plant material of mesocosms was harvested, weighed and litter material was
 taken to study decomposition using the litter-bag and litterbed approach.
 Litter weight loss was quantified and calculated (%). Further, we used
 plant trait data bases to calculate community weighted mean traits and
 functional diversity, based on trait values and relative abunances of
 species within plant communities. Soil respiration, the decomposition of
 standard material and consumption of baits in lamina-bait sticks were
 assessed in pots within the communities, that contained bare soil only.
 The latter data are to be found mainly in the appendix.
description: Missing values are indicated with NA.
 Abbreviations: pot= pot number of respective
 turf piece or sown community cov2018=percent cover of
 species in turf pieces in May 2018 [%] water= water
 availability levels L= water logged
 W= wet M= mesic dry=
 dry PL= pulsed flooding weight [g]=
 species-specific biomass within sown communities rel.
 abundance [%]= relative abundance of species of sown communities in %,
 based on biomass data species=species within sown
 communities Am=Achillea millefolium
 Ap=Alopecurus pratensis Ae=Arrhenatherum
 elatius Bh=Bromus hordeaceus
 Bp=Bellis perennis Cb=Crepis biennis
 Cj=Centaure jacea Dg=Dactylis
 glomerata Fr=Festuca rubra
 Ga=Gallium mollugo agg. Pl=Plantago
 lanceolata Pp=Poa pratensis
 Td=Trifolium dubium Tp=Triflium
 pratense Vc=Vica cracca
 FDis=Functional dispersion, measure for functional
 diversity RaoQ=Rao´s quadratic entropy, measure for
 functional diversity SLA=specific leaf area (LEDA data
 base) [mm2mg-1] LDMC=leaf dry matter content (LEDA data
 base) [mg/g] N=leaf nitrogen content (TRY data base)
 [%] meadow origin= different sites, from which turf
 pieces were taken in November 2015 bait1-16=baits of
 lamina bait sticks froms upper (1) to lower (16), 1=eaten, 0=not
 eaten eaten=sum of eaten baits per stick
 not=non-eaten baits per stick pool=pool in
 which bare soil pots for soil respiration and lamina-bait testes were
 placed initial weight [g]=dry weight of litter that was
 placed in litter bags remaining weight [g]=dry weight
 of plant material that remained in litter bags after the decomposition
 period C=carbon in leaves, measured with elemental
 analyser [%] N=leaf nitrogen content, measured with
 elemental analyser [%9 CNratio=ratio between C and N in
 leaves, measured with elemental analyser system=plant
 system in pots: turf pieces=turf pieces dug out from
 natural meadows prior to experiment sown
 communities=communities sown with 15 different species and kept free from
 non-target species monocultures=monocultures consisting
 of one species, sown in the same density as sown communities
 single plants= pots with only one single plant in the
 middle