Direct vs. indirect controls of decomposition
How future warming and associated vegetation changes will impact decomposition rates in the tundra will also depend on the balance of microbial community priming by plant traits (Veen et al. 2015) and increases in decomposer activity with warming (Rijkers et al. 2023). The weak relationships between environmental controls and decomposition responses observed in our study suggest that neither the direct (traits) nor indirect (microclimatic) vegetation effects that we measured were particularly important for decomposition in our study system. Microclimate was associated with weak trends in Green Tea mass loss and stabilisation rates, while we did not find any link between plant community or soil traits and decomposition. These findings could point to a higher importance of abiotic conditions, for instance induced by shrub shading (Blok et al. 2010, Myers-Smith and Hik 2013), snow accumulation (Sturm et al. 2001) or bryophyte cooling (Blok et al. 2011), compared to substrate quality effects for controlling decomposers. This is also in line with earlier predictions that climate represents the dominant control on litter decomposition in harsh environments (Coûteaux et al. 1995). While our study was limited to certain predictors and gradients, follow-up studies explicitly stratifying across these microenvironmental factors might help elucidate this further.