DOI: 10.5061/dryad.6k23f
title: Data from: Plant species richness negatively affects root decomposition in grasslands

description: Plant diversity enhances many ecosystem functions, including root biomass
 production, which drives soil carbon input. Although root decomposition
 accounts for a large proportion of carbon input for soil, little is known
 about plant diversity effect on this process. Plant diversity may affect
 root decomposition in two non-exclusive ways: by providing roots of
 different substrate quality (e.g. root chemistry) and/or by altering the
 soil environment (e.g. microclimate). To disentangle these two pathways,
 we conducted three decomposition experiments using a litter-bag approach
 in a grassland biodiversity experiment. We hypothesized that: (i) plant
 species richness negatively affects substrate quality (indicated by
 increased C:N ratios), which we tested by decomposing roots collected from
 each experimental plot in one common plot; (ii) plant species richness
 positively affects soil environment (indicated by increased soil water
 content), which we tested by decomposing standardized roots in all
 experimental plots; (iii) the overall effect of plant species richness on
 root decomposition, due to the contrast between quality and environmental
 effects, is neutral, which we tested by decomposing community roots in
 their ‘home’ plots. Plant species richness negatively affected root
 decomposition in all three experiments. The negative effect of plant
 species richness on substrate quality was largely explained by increased
 root C:N ratios along the diversity gradient. Functional group presence
 explained more variance in substrate quality than species richness. Here,
 the presence of grasses negatively affected substrate quality and root C:N
 ratios, while the presence of legumes and small herbs had positive
 effects. Plant species richness had a negative effect on soil environment
 despite its positive effect on soil water content which is known to
 stimulate decomposition. We argue that – instead of soil water content – a
 combined effect of soil temperature and seasonality might drive
 environmental effect of plant diversity on decomposition in our plant
 communities, but this remains to be tested. Synthesis. Our results
 demonstrate that both substrate quality and soil environment contribute to
 the net negative effect of plant diversity on root decomposition. This
 study promotes our mechanistic understanding of increased soil carbon
 accumulation in more diverse grassland plant communities.
description: RootMassLoss_QualityExperiment_JenaExperiment (MainExperiment, 2014)This data set contains mass loss of community roots decomposing in the common plot in the Jena experiment in 2014. The Metadata contains the Dataset ID in the Jena Experiment database and detailed information of column: 'plotcode' is plot ID in the Jena Experiment; 'bag_ID' is the ID for litter bags within each decomposition experiment; 'root_type' is the type of roots in the litter bags where plot coded for community roots, lolium coded for standardized roots; 'site' is the location of where decomposition happened; 'sector' is the subplots in common plot; 'mass_initial' is root mass in the litter bags before buried in the field and handling loss is seduced already; 'mass_remain' is root mass in the litter bags at each retrieval; 'date_in' is the exact dates when the litter bags were buried. In the form of DD-MM-YY; 'date_out' is the exact dates when the litter bags were retrieved. In the form of DD-MM-YY; 'actual_decomptime' is the exact days litter bags were in the field; 'massloss' is actual mass loss =100 - mass_remain/mass_initial*100; 'std_decomptime' is standardized days litter bags were in the field; 'std_massloss' is stadardized mass loss = massloss/actual_decomp.time*std_decomp.time.100065_RootMassLoss_QuaExp.xlsxRootMassLoss_EnvironmentExperiment_JenaExperiment (MainExperiment, 2014)This data set contains mass loss of standardized roots decomposing in the experimental plots in the Jena Experiment in 2014. The Metadata contains the Dataset ID in the Jena Experiment database and detailed information of column: 'plotcode' is plot ID in the Jena Experiment; 'bag_ID' is the ID for litter bags within each decomposition experiment; 'root_type' is the type of roots in the litter bags where plot coded for community roots, lolium coded for standardized roots; 'site' is the location of where decomposition happened; 'sector' is the subplots in common plot; 'mass_initial' is root mass in the litter bags before buried in the field and handling loss is seduced already; 'mass_remain' is root mass in the litter bags at each retrieval; 'date_in' is the exact dates when the litter bags were buried. In the form of DD-MM-YY; 'date_out' is the exact dates when the litter bags were retrieved. In the form of DD-MM-YY; 'actual_decomptime' is the exact days litter bags were in the field; 'massloss' is actual mass loss =100 - mass_remain/mass_initial*100; 'std_decomptime' is standardized days litter bags were in the field; 'std_massloss' is stadardized mass loss = massloss/actual_decomp.time*std_decomp.time.100064_RootMassLoss_EnvExp.xlsxRootMassLoss_QualityEnvironmentExperiment_JenaExperiment (MainExperiment, 2014)This data set contains mass loss of community roots decomposing in their home plots in the Jena experiment in 2014. The Metadata contains the Dataset ID in the Jena Experiment database and detailed information of column: 'plotcode' is plot ID in the Jena Experiment; 'bag_ID' is the ID for litter bags within each decomposition experiment; 'root_type' is the type of roots in the litter bags where plot coded for community roots, lolium coded for standardized roots; 'site' is the location of where decomposition happened; 'sector' is the subplots in common plot; 'mass_initial' is root mass in the litter bags before buried in the field and handling loss is seduced already; 'mass_remain' is root mass in the litter bags at each retrieval; 'date_in' is the exact dates when the litter bags were buried. In the form of DD-MM-YY; 'date_out' is the exact dates when the litter bags were retrieved. In the form of DD-MM-YY; 'actual_decomptime' is the exact days litter bags were in the field; 'massloss' is actual mass loss =100 - mass_remain/mass_initial*100; 'std_decomptime' is standardized days litter bags were in the field; 'std_massloss' is stadardized mass loss = massloss/actual_decomp.time*std_decomp.time.100063_RootMassLoss_QuaEnvExp.xlsx100062_CN_Root_Ratio_JenaExperiment (MainExperiment, 2013)This data set contains C:N ratio of community roots used in the root decomposition experiment. Root samples were collected in 2013 in the Main Experiments. 'Plot' is plot ID in the Jena Experiment.100062_CN_Root_Ratio.xlsx58166_WaterContent_Soil_JenaExperiment (MainExperiment, 2014)This data set contains soil water content on litter subplots (SPx) with a Ml2x probe during the decomposition experiments. 'plotcode' is plot ID in the Jena Experiment; 'Date' is date of measurement; 'Sample' is replicate number; 'SWC' is soil water content; 'mV' is milli Volt. B3A14 is the plotcode of the common plot.58166_WaterContent_Soil.xlsxPlotInfo_JenaExperiment_MainExperimentThis data set contains plant diversity information of experimental plots in the Jena Experiment. 'plotcode' is the plot ID; 'block' is the block ID;'sowndiv' is plant species richness;'numfuncg'is number of functional groups;'numgrass' is number of grass species;'numsherb' is number of small herb species;'numtherb' is number of tall herb species;'numleg' is number of legume species; 'grass' is presence/absence of grasses;'sherb' is presence/absence of small herbs; 'therb' is presence/absence of tall herbs;'leg' is presence/absence of legumes. Code_treatment explains treatment applied to the plots.plotinfo.xlsx