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.