Kauane Bordin, Universidade Federal do Rio Grande do Sul, Brazil, discusses her article: Growth–survival trade-off in temperate trees is weak and restricted to late-successional stages
Temperate forests, such as those in the U.S. and Europe, are a huge part of Earth’s lungs. They provide habitat for countless species, store massive amounts of carbon that help slow climate change, and keep ecosystems stable. Understanding how their trees “make decisions” is key to protecting both forests and the planet.
With finite resources, trees must make choices about how they use their energy. They can put more resources into growing taller and faster, or into living longer and surviving difficult times, but usually, they can’t do both. We call this the growth-survival trade-off. While we expect that these trade-offs are general and widespread, some recent studies have shown that disturbances may have a huge impact on how trees make their decisions. In tropical ecosystems, forests affected by disturbances do not show the growth-survival trade-off because the disturbed environment filters which species can arrive and establish in those conditions, allowing only fast-growing and low-survival species to occur.
In this study, we looked at forests across the eastern U.S. to see how disturbances – like severe storms, fires, or insect outbreaks – affect the growth-survival trade-off. We compared early successional forests (generally young forests, with lots of disturbance) and late successional forests (usually older and more stable). We used data from the U.S. National Forest Inventory, a large-scale and fundamental assessment of forest structure and dynamics, to answer these questions.
Surprisingly, we found that the trade-off between fast growth and long survival is pretty weak overall when we combine disturbed and older forests, and it really only shows up a little in older forests. In young, disturbed forests, it basically disappears. In addition, we found that the species in these disturbed environments exhibit faster growth than their conspecifics, but it does not lead to increased mortality. Therefore, differently from tropical forests, temperate tree species in disturbed environments show faster growth without a corresponding increase in mortality. This potentially determines the absence of the growth-survival trade-off across U.S. temperate forests.
Why does this matter? Because disturbances are becoming more common with climate change and human activity. If those disturbances disrupt how trees balance growth and survival, it could have broad and large-scale effects. Major disturbances may change which species dominate forests, how forests recover, and even how much carbon they store, which is directly related to climate change.
In short: forests don’t just grow randomly, and disturbances shape which trees arrive and thrive. If we want healthy forests and a stable climate, we need to understand how these hidden decisions of trees work and develop tools to minimise the consequences of those decisions.
