Rapid recovery of thermal environment after selective logging in the Amazon

Abstract

Selective logging is one of the most widespread pattern of disturbance in tropical forests but has a much lower detrimental impact on forest structure than wildfires and conversion to farmland. Thus, logged tropical forest represents critical strongholds of global biodiversity. The ability of these forests to rapidly recover their baseline thermal environmental conditions will markedly influence their conservation value, particularly under global climate change. We investigated the impacts of commercial selective logging on the forest thermal environment in the Brazilian Amazon by relating canopy disturbance from logging to ambient understorey and ground surface temperatures. Specifically, we assessed the impact of selective logging on the forest thermal heterogeneity; how much post-harvest time is required for the thermal environment of logging gaps and logging roads return to unlogged primary forest levels; and the spatial availability of surface microclimates considering time of recovery since logging. Logging gaps following 1 year of recovery had a hotter understorey ambient than all other environments, especially during peak midday temperatures. Compared to the unlogged understorey, logging gaps after 3 years of recovery were only marginally warmer, and logging gaps after 5 years of recovery were slightly cooler. Older wide roads (5 years; 6 m) experienced very similar understorey thermal conditions than both narrow roads (3 m) after 1-5 years of recovery, and unlogged forest. Ground surface temperatures exhibited the largest discrepancies among all environments. The temperature range spanned by surface microclimates notably increased during peak midday heat in logging gaps following 1 year of recovery. Additionally, the proportion of cool area was smaller in younger logging gaps, but the average size of cool patches and their spatial aggregation was similar to that in unlogged forest. Although commercial selective logging can severely damage tropical forest structure, we found that the forest can fairly rapidly regain its thermal environment. Post-logging forest management should carefully focus on preventing fire incursions and illegal activities with special attention to those 3-5 years post-harvest. Thermal homeostasis in selectively logged tropical forests can be vital for long-term maintenance of global biodiversity under contemporary scenarios of climate change.