Little difference in importance of environmental variables among contrasting tea types
Although relative mass loss was higher in Green Tea than in Rooibos Tea (Figure S3), relationships of mass loss with plant traits, soil characteristics, and microclimate differed little between tea types (Figure 4a). This indicates that, overall, variation in environmental conditions did not selectively stimulate primary decomposer groups that prefer either labile or recalcitrant litter. Higher mass loss in Green Tea compared to Rooibos Tea reflected differences in substrate quality, as for instance nitrogen content and water-soluble fraction in Green Tea are two to three times higher than in Rooibos Tea, respectively (Keuskamp et al. 2013). This result corroborates the importance of litter identity in the light of tundra vegetation changes and increasingly recalcitrant litter (Cornelissen et al. 2007, Myers-Smith et al. 2011, Thomas et al. 2023). Yet, largely constant mass loss across environmental gradients suggests that both bacterial (main decomposers of labile litter) and fungal communities (main decomposers of recalcitrant litter) varied little among plots (Yang et al. 2021). The only relationships that differed slightly between tea types were those associated with microclimatic variables. For instance, we observed lower mass loss at warmer and drier conditions for Green Tea, but not for Rooibos Tea (Figure 4a). These differences could reflect the effect of warming-induced evaporation, which can reduce decomposer activity at suboptimal moisture conditions (Christiansen et al. 2017). Overall, our findings suggest that vegetation changes and reduced litter quality might be more important for future tundra decomposition than immediate microclimatic changes related to warming (Cornelissen et al. 2007, Cornwell et al. 2008, Thomas et al. 2023). However, more targeted sampling of decomposer communities could help to disentangle these relationships.