Reacción a "Extreme droughts slow the carbon storage capacity of scrublands and grasslands"

This study uses a large number of international drought simulation experiments involving rain exclusion covers in grasslands and scrub ecosystems. The aim of this work is to discern the impact that both the severity and duration of droughts have on the functioning of these ecosystems, particularly on their plant productivity. The study shows that, in general, there is a decrease in productivity during the first year of drought. However, it suggests that these ecosystems may acclimatise (i.e. maintain productivity similar to that observed during the first year of drought) if there are no extreme droughts in subsequent years. Conversely, it is observed that an increase in drought severity to historically extreme levels could result in a pattern of cumulative productivity loss over time.

The work is rigorous and incorporates a comprehensive database with robust analyses and interpretations. It is regrettable that experiments in critical regions (e.g., those with highly degraded soils that are widely distributed, such as the Sahel or the vast regions of Central Asia) are not included. On the other hand, as the authors explain, another clear limitation of this work lies in the lack of temperature manipulation in the experiments. This aspect is relevant since drought is associated with both higher temperatures and higher vapour pressure deficits, which have the potential to reduce photosynthesis and, therefore, productivity. Thus, it is possible that the study has minimised the impact of drought on the variable studied.

Nevertheless, it is (correctly) concluded that the productivity losses observed in the ecosystems studied could intensify due to the more than likely increase in extreme drought events projected in the current climate framework. Finally, it is very likely that the impact of extreme droughts will also result in a significant increase in plant mortality and a substantial degradation of ecosystem services.