Angst et al. 2024 Functional Ecology raw data

At the end of the vegetation season, temperate herbs start to senesce and gradually shed their dead biomass. However, surprisingly large amounts of dead biomass remain standing, i.e., marcescent. The consequences of this phenomenon for the decomposition of marcescent biomass once it finally reaches the soil are largely unknown. Here, we aimed to determine if the prolonged standing phase of dead biomass affects its subsequent decomposition in the organic layer to such an extent that its mass loss and chemistry are distinguishable from those of directly shed biomass. We further aimed to disentangle the role of plant functional traits and groups (forbs vs. grasses) in the effect of marcescence on decomposition. To this end, we sampled living, marcescent, and shed senescent biomass of 39 herbaceous plant species grown in a common garden experiment, determined plant functional traits, and incubated the marcescent and shed plant tissues in the field in an allochthonous organic layer for six months. We then determined the mass loss, C and N contents, and chemical and microbial community composition of the decomposed tissues. Our results show that marcescent tissues decomposed more slowly than directly shed tissues (mass loss <40 vs. ~60%, C content 44 vs. 40%, C:N 44 vs. 29), likely due to favourable conditions for decomposition in the organic layer. These were mirrored in a significantly higher microbial colonization of shed (~ 420 µg biomass C g-1) than marcescent tissue (~270 µg biomass C g-1) even after six months in the organic layer. Moreover, higher relative contributions of aliphatics and polyphenolics to shed tissues indicated a more advanced stage of decomposition. Notably, marcescent tissues of plants with a more complex growth architecture, i.e., forbs comprised of stems (marcescent) and leaves (shed), decomposed more slowly than directly shed litter (mass loss ~37 vs. ~63%), while such differences were absent for grasses, with a more uniform growth architecture. These findings highlight that marcescence in the temperate herbaceous flora can substantially affect litter decomposition, and thus C and nutrient cycling through temperate ecosystems. However, the extent to which marcescence affects decomposition depends on plant functional group.