Abstract
Forest litter decomposition is considered as an essential ecosystem
process affecting carbon and nutrient cycling in mountains. However,
there exists high uncertainty in accurately estimating the contribution
of litter decomposition to terrestrial ecosystems, largely due to the
incomparability of different studies and the data limitation in
microclimate and non-climatic factors at spatially matched scales. Here
we used the tea bag index (TBI) as a standardized protocol to evaluate
spatial variations in forest litter decomposition rate (k ) and
stabilization factor (S ) across 10 mountains spanning a wide
range of subtropical and tropical forests. Based on the coordinated
experiment of 6,864 teabags in 568 sampling sites along elevations, we
evaluated the importance of 10 environmental factors covering soil
microclimate, edaphic properties, plant diversity, and topography onk and S by using model averaging and linear-mixed effects
models. Of the 10 mountains, we found a consistently decreasing pattern
of k and an increasing pattern for S along elevations. And
the significant effect of k with elevation was mainly found in
the western and northmost mountains, while the effect of Soccurred in the western and southernmost mountains. For microclimate,
there was a general importance of soil temperature (coef. = 0.48)
and temperature variation in the growing season (coef. = 0.36) ink , and soil temperature (coef. = -0.46) and moisture
variation on S (coef. = -0.36). The dominant role of soil
microclimate was mainly found in western mountains with relatively cold
environments. For non-climatic drivers, a significant effect of tree
diversity on k and a negative correlation of edaphic and
topography with S in the western and southern mountains were
detected. These findings provide a general understanding of spatial
variations of driving factors in forest litter decomposition and
highlight a dominant control of soil microclimate in cold forests in
high elevations and latitudes.
Keywords: altitudinal gradient; climate change; experimental
macroecology; litter decay; microclimate