Coarse Woody Debris Improves Nutrient Cycling in a Rehabilitated Montane Forest

Abstract

The successful restoration of disturbed ecosystems depends on the ability of below-ground soil decomposer communities to cycle organic matter into soil stocks and available forms for above-ground producers. We investigated the interactions between forest disturbance history, coarse woody debris and leaf carbon-to-nitrogen ratio (C:N) and their impacts on biological activity in soil and litter within a rehabilitated rock spoil and adjacent undisturbed montane forest in Kosciuszko National Park, Australia. We measured rates of soil CO2 efflux and leaf decomposition, two key measures of soil function, to determine whether proximity to coarse woody debris improved soil function in rehabilitated sites. Coarse woody debris was associated with increased CO2 efflux and decomposition in the rehabilitated forest (28.1% and 12.6% increase, respectively), but not within nearby undisturbed forest. In the absence of coarse woody debris, leaf mass loss to decomposition was 84.2% lower in the rehabilitated forest compared to the reference forest. Leaf decomposition varied significantly depending on the species from which the litter derived and was greatest in green tea and eucalyptus litter, and least in rooibos tea, with the CWD and forest type effects being consistent among these. However, decomposition of leaf litter of native species did not conform to expectations; leaves with low C:N had lower, rather than higher, rates of decomposition. These findings highlight the positive effects of coarse woody debris addition on soil functioning within rehabilitated forests and its potential in reconstructing nutrient cycles following disturbance.