What is the impact of logging on the physical environment in tropical forests? We just had a new study come out addressing this topic, as part of the Biodiversity and Land Use Impacts (BALI) project. The study is published in the new journal Frontiers in Forests and Global Change. You can download a PDF copy or read it at the journal (open-access).

Microclimate variation affects performance of organisms that live in a forest, e.g. new tree seedlings, insects, or animals. It also directly influences rates of ecosystem processes like respiration and decomposition that contribute carbon emissions to the atmosphere. How much does logging a forest change microclimate, and why? To find out, we made intensive measurements of temperatures near the forest floor using a distributed network of sensors.

Sites were located in Sabah, Borneo, at sites that ranged from old-growth forests to recently logged forests where most of the large canopy trees have been removed. Moving around in these logged sites can be challenging, with deep tangles of lianas and woody regrowth.

Here you can see some of the dataloggers we used, wrapped in waterproofing and then attached to stakes.

We placed the stakes in a gridded pattern across the landscape in order to provide high-resolution data for microclimate variation.

Below you can see the gridded results – each pixel is a one-meter square, and the running count indicates the number of days that have passed (0 = midnight of first day, 1.5 = noon on second day, etc.)

We showed that the logged forests experience much more extreme microclimates, and also have much more heterogeneity in microclimate – suggesting that life for organisms near the ground in logged forests is qualitatively much different than in old-growth forests.

Surprisingly, we did not find that there were a consistently strong set of factors (like canopy structure, or site topography) that could predict this variation across sites, despite having very good LiDAR canopy/elevation data and detailed stem maps. This runs contrary to prior studies of microclimate that have been conducted at larger spatial scales, and suggests that fine-scale variation in light transfer and understory vegetation are driving our results. The overall implication is that predicting microclimate within forests remains highly challenging, but critical for better understanding global change impacts on forests.

Please have a read – the study required a lot of hard work from an international team, and cost not a small amount of sweat. We are proud of the final result and hope it will stimulate some careful thought around the extreme conditions organisms experience in degraded environments.