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.