Reforestation is widely promoted as a way to mitigate climate change by capturing carbon from the atmosphere. However, its real success depends on how trees invest (allocate) the carbon they capture, that is, how much they invest to grow leaves, stems or roots, particularly under warmer and drier conditions.
In this study, we analysed how climate affects carbon allocation in large-scale pine reforestations across the Mediterranean region. We combined satellite data with field measurements from tree rings to explore long-term changes in tree growth and carbon allocation. We studied four pine species differing in their tolerance to drought and evaluated how temperature and rainfall influence productivity and the carbon invested above and below ground.
We found that both forest productivity and the amount of carbon invested aboveground increased with water availability but declined with increasing temperature. Trees growing in cooler and wetter sites put more carbon into stems and branches, while those in hotter and drier sites invested more in roots. These results are consistent with the optimal carbon allocation theory, meaning that trees adjust growth to maximise survival under changing conditions.
Our results indicate that, with more frequent droughts, pine forests in dry and low-elevation sites may lose part of their capacity to store carbon, while cooler and wetter forests at higher elevations could become relatively more efficient carbon sinks. Understanding how tree species respond to climate is important to improve reforestation strategies, for example, by selecting species and sites more resilient to heat and water stress. This information can help to guide forest management and ensure that reforestation continues to contribute to both climate mitigation and the conservation of Mediterranean ecosystems.
This is a Plain Language Summary discussing a recently-published article in Journal of Applied Ecology. Find the full article here.
