The Effects of Forest Operations and Silvicultural Treatments on Litter Decomposition Rate: a Meta-analysis

Abstract Purpose of Review As litter decomposition is a fundamental process in forest ecosystems, representing the link between aboveground and belowground biogeochemical processes, we developed an effect size summarisation of the implications of forest management on litter decomposition rate, by applying a multi-level meta-analysis and multivariate mixed-effects meta-analytic linear models. Our aim was to review the findings of the current literature and to understand how forest management, silvicultural treatment, and forest operations could affect litter decomposition rate. Furthermore, we investigated the effects of environmental variables that included stand type, climatic conditions, and the percentage of biomass removal on litter decomposition rate. Recent Findings We found a statistically significant reduction in litter decomposition rate associated with clear-cutting, and no statistically significant differences for the overall effects of retention forestry and logging activities (disturbed forest soil in the form of skid trails or strip roads). Concerning the sub-group analysis and multivariate meta-regression, there were no significant effects for stand type (broadleaf, coniferous, or mixed) or climatic conditions (mean annual temperature and annual precipitation). The percentage of biomass removal showed a significant positive correlation with the effect size, thus indicating that higher biomass removal in the framework of retention forestry leads to an increase in litter decomposition rate. Also, the mesh size of the litterbag showed a positive correlation with the effect size, suggesting that there is a probability of a factor of stronger disturbance to large-body decomposer organisms such as microarthropods. Summary Litter decomposition rate is related, among other factors, to soil microclimatic conditions and soil biota. Therefore, this process can be strongly influenced by active forest management, meant as a silvicultural treatment carried out by applying a given harvesting system. In the context of retention forestry, increased light availability seems to be the driving force in shaping increased litter decomposition rates with increasing biomass removal. On the other hand, when a clear-cut is applied, the stronger modification to the edaphic community leads to decreased litter decomposition rates. It is worth noting that the modification may also be related to soil manipulation to favour the establishment of artificial regeneration. The findings, however, showed very large variability, thus suggesting the need for further research on such a complex topic. Multidisciplinary studies that analyse the microclimate and the edaphic biological communities along with the litter decomposition are particularly recommended.