Trees show limited ability to adapt to prolonged drought, study finds

An analysis of 40 forest drought experiments indicates that trees do not significantly adjust their physiology to cope with long-term water scarcity. The findings suggest that forests may be more vulnerable to climate-induced droughts than previously thought. This research highlights the limited acclimation capacity of trees under sustained stress.

The study analyzed 24 physiological traits across 40 throughfall reduction experiments in forests worldwide. Throughfall reduction uses gutters beneath the forest canopy to divert rainfall before it reaches the soil, allowing researchers to observe drought responses while trees remain in natural soil conditions. This method contrasts with potted-plant experiments or natural rainfall gradients, which may not accurately reflect real forest environments.

Despite prolonged water scarcity, trees maintained stable embolism resistance, hydraulic efficiency, leaf nutrient concentrations, and photosynthetic capacity. However, tissue water potentials declined, narrowing hydraulic safety margins and pushing trees closer to hydraulic failure. Interestingly, while net photosynthesis decreased due to stomatal closure, nonstructural carbohydrate levels remained stable, indicating reduced carbon uptake did not clearly deplete stored carbon reserves.