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.

在生长季末期，温带草本植物会逐步进入衰老阶段，并脱落死亡生物量。但令人意外的是，仍有大量死亡生物量保持直立状态，即枯立（marcescent）现象。目前，这类枯立生物量最终进入土壤后的分解过程及其相关影响机制仍不甚明确。
本研究旨在探明死亡生物量的长期直立留存阶段是否会对其在有机层中的后续分解产生显著影响，使其质量损失率与化学特征与直接脱落的生物量产生显著差异。我们还旨在厘清植物功能性状与功能群（双子叶草本与禾本科草本）在枯立现象对分解过程的影响中所扮演的角色。
为此，我们在同质园（common garden）试验中种植了39种草本植物，采集其活体组织、枯立组织以及自然脱落的衰老组织，测定了相关植物功能性状，并将枯立与脱落的植物组织置于异源有机层中开展为期6个月的野外培养试验。随后，我们测定了分解后组织的质量损失率、碳氮含量，以及化学组成与微生物群落结构。
研究结果显示，枯立组织的分解速率慢于直接脱落的组织：其质量损失率分别为<40%与约60%，碳含量分别为44%与40%，碳氮比分别为44与29，这一差异可能源于有机层内更适宜的分解环境。该结果同样体现在微生物定殖水平上：即使经过6个月的野外培养，脱落组织的微生物生物量碳（约420 µg biomass C g⁻¹）仍显著高于枯立组织（约270 µg biomass C g⁻¹）。此外，脱落组织中脂肪族化合物与多酚类物质的相对占比更高，表明其分解阶段更为先进。值得注意的是，具有更复杂生长结构的植物（即由茎（枯立）与叶（脱落）组成的双子叶草本），其枯立组织的分解速率慢于直接脱落的凋落物（质量损失率分别为约37%与约63%），而生长结构较为均一的禾本科草本则未出现此类差异。
本研究结果表明，温带草本植物的枯立现象可显著影响凋落物分解过程，进而影响温带生态系统的碳循环与养分循环。不过，枯立现象对分解过程的影响程度取决于植物功能群类型。