Concept: Decomposition rates are an important component of carbon sequestration rates in soils, potentially mitigating future climate change. Here we aim to better understand decomposition’s relationship with temperature in natural conditions.

Structure: In snow-tussock grassland dominated by Chionochloa rubra var. rubra on Mount Tongariro, Tongariro National Park, New Zealand, we measured decomposition of Chionochloa leaf litter along an ~ 700 m altitudinal gradient, as a space-for-temperature experiment, representing 4.2ºC of warming. For litter, we haphazardly collected attached, but achlorophyllous leaves, which were cut into 5 cm long segments and pooled per site. We examined decomposition rates in a full reciprocal translocation of litter bags between 8 plots as both the origin of 8 litter types and the 8 destinations of plating out of litter bags, over 4 years using 6 replicates. Litter decomposition bags, 20 cm x 25 cm in size, were of black nylon rectangular mesh with a pore size of 2 mm. We used 3.00 g of litter per bag, applied a wet/dry weight correction, and measured litter remaining after each time period. Bag recovery was 91 %. We went on to model decomposition's relationships to environmental variates.

Results: Litter decomposed progressively over time, but at the same rate along the altitudinal gradient. There was no home-field advantage. In terms of litter quality, decomposition rates were related only to litter lignin, or fibre or litter N. Only decomposition at Year 4, and that only when organised by litter destination, showed a relationship to mean annual temperature jointly with soil C, and this was only weak and implausible. When studied across the full reciprocal transplant, there were no significant interactions between Origin and Destination data with or without Years. Therefore litter from each plot decomposed at the same rate as other plots’ litter at all altitudes, allowing for small, often irregular differences in litter quality and micro-environment.  

 Decomposition is reported as change in dry weight of litter samples sampled from 8 sites (i.e., source), and plated out into each of the same 8 sites (i.e., destination), over one of 1 - 4 years, with 6 replicates.

Data are presented with source, destination and year codes.

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