Microclimate explains little variation in year-round decomposition
across an Arctic tundra landscape
Abstract
Litter decomposition represents a major path for atmospheric carbon
influx into Arctic soils, thereby controlling below-ground carbon
accumulation. Yet, little is known about how tundra litter decomposition
varies with microenvironmental conditions, hindering accurate
projections of tundra soil carbon dynamics with future climate change.
Over 14 months, we measured landscape-scale decomposition of two
contrasting standard litter types (Green Tea and Rooibos Tea) in 90
plots covering gradients of micro-climate and -topography, vegetation
cover and traits, and soil characteristics in Western Greenland. We used
the Tea Bag Index protocol to estimate relative variation in litter mass
loss, decomposition rate (k) and stabilisation factor (S) across space,
and Structural Equation Modelling to identify relationships among
environmental factors and decomposition. Contrasting our expectations,
microenvironmental factors explained little of the observed variation in
both litter mass loss, as well as k and S, suggesting that the variables
included in our study were not the major controls of decomposer activity
in the soil across the studied tundra landscape. We use these
shortcomings of our study combined with findings from the current
literature to discuss future avenues for improving our understanding of
the drivers of tundra decomposition and, ultimately, carbon cycling
across the warming Arctic.