Abstract
Lichens and bryophytes are abundant primary producers in high latitude and high elevation ecosystems, and they play an important role in ecosystem processes such as decomposition and nutrient cycling. Despite their importance, little is known about the decomposability of lichens and bryophytes either among or within species, at the whole community level, or how this decomposability is affected by their functional traits. Here, we studied decomposability of lichens and bryophytes at the community‐level and individual species‐level (using 21 species and genera) collected from an elevational gradient in alpine Norway. In order to isolate the elevation effect on litter quality, we used a standardized laboratory bioassay to measure decomposability. In contrast to our expectations, we found that community‐level decomposability of lichens and bryophytes increased with elevation and thus decreasing temperature. In contrast, phosphorus release from the litter decreased with elevation while nitrogen release was unresponsive. Decomposability was explained by nutrient concentrations, litter pH and primary producer group identity (lichens versus bryophytes) at both the individual species and community levels. Species turnover (changes in species composition and abundance) was the main driver of decomposability across elevation at the community level, despite some of the traits explaining decomposability showing high intraspecific variability. Our study highlights the importance of among‐species variation in determining lichen and bryophyte decomposability. Further, the higher decomposability that we found for higher elevations suggests that global warming might result in a shift towards slower decomposable lichen and bryophyte species.
Highlights
Decomposition, the decay of organic matter, is an important ecosystem process that drives carbon and nutrient cycling (Chapin et al 2011)
We investigated how the decomposability of non-vascular vegetation at the individual and whole community levels change along an alpine elevational gradient in southern Norway, by using a standardized laboratory bioassay
The variation in P release was mostly driven by species turnover effects, but intraspecific variation greatly improved the total variation explained by elevation because of its positive covariation with species turnover effects (Fig. 1c)
Summary
Decomposition, the decay of organic matter, is an important ecosystem process that drives carbon and nutrient cycling (Chapin et al 2011). The indirect effects of expected future climate change, as manifested through vegetation shifts, will likely have a larger impact on decomposition, by altering litter quality, than will the direct effects of increasing temperature on decomposer activity (Cornelissen et al 2007a, DeMarco et al 2014). In this light, it is important to isolate indirect climatic effects, i.e. how changes in community composition caused by climate alter litter quality, from more direct climatic effects on litter decomposition
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