The importance of different traits
In general, the more diverse a forest how better it can deal with drought and heat. But the local effect of tree diversity is less clear. Now a group of international researchers show that for a tree the water use efficiency of its neighbours makes a big difference.
Globally the rule of the thumb is the more diverse the better. Although, locally the outcomes can be different. To investigate this in more detail, the researchers analysed data from the last 30 years from 15 sites in the Amazonian forest.
They checked: the growth of the trees, their water use, and how close by their neighbours were standing. In addition, they looked at how the weather had been, like how hot it was, and how wet or dry.
Diversity should also take in to account in how far the different traits overlap
In general, trees like to have enough space for themselves. When they are al huddled together, then they grow less quickly. Also trees with efficient water use and larger leaves than their neighbours did better.
But by higher temperatures and especially during drought a shift was observed. While during normal circumstances trees with efficient and non-efficient water use can perfectly live together, during a drought, this changes. During a drought water-spender trees are getting a lot of the sparse water. With as effect that during a drought especially the water efficient trees grow slower.
For diversity of forests, it is important that not only is taken into account the different species, but also to what extend their traits overlap. Or better, don’t overlap.
Literature
Nemetschek, D., Fortunel, C., Marcon, E., Auer, J., Badouard, V., Baraloto, C., Boisseaux, M., Bonal, D., Coste, S., Dardevet, E., Heuret, P., Hietz, P., Levionnois, S., Maréchaux, I., Stahl, C., Vleminckx, J., Wanek, W., Ziegler, C. and Derroire, G. (2025), Love Thy Neighbour? Tropical Tree Growth and Its Response to Climate Anomalies Is Mediated by Neighbourhood Hierarchy and Dissimilarity in Carbon- and Water-Related Traits. Ecology Letters, 28: e70028. https://doi.org/10.1111/ele.70028
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