Ghosts of past droughts

With this post coming out on Halloween, I thought I’d search the word ghosts in Google Scholar and see what came up. To my surprise, one of the first articles related to sustainability, so, of course, I had to read it.

Kannenberg, Schwalm, and Anderegg (2020) published an article titled “Ghosts of the past: How drought legacy effects shape forest functioning and carbon cycling.” This is a known effect; a drought can impact a forest and individual trees multiple years later. For example, pests and pathogens tend to be more prevalent during droughts, structural damage can occur, and less reproduction happens. For some species, especially non-dominant ones, drought can have beneficial effects because the drought stresses the dominant species to the point that they can’t suppress other species as much. Also, as individual plants die, those nutrients can then be put back into the system for other individuals to use. At the forest level, there can be reduced leaf production overall due to the need to repair structural damage instead. This can, in turn, reduce the carbon uptake by the forest.

Water availability is expected to become more limited with global climate change. And extreme weather events, like drought, are expected to become more common. Therefore, it is important for researchers to identify and track forests in order to understand legacy drought effects, but how to do this is subject to significant variation. This was the main purpose of the article I looked at. They aimed to understand what is causing the legacy effects so that they could review the types of data that can be collected and identify what data points should be collected. This gets a little beyond the scope of this blog, but in summary, it is important to look not just at individuals but at whole sites. By collecting more data about the site, it will be easier to develop accurate models to “help improve predictions of the effects of climate change on the world’s forests” (p. 897).