Early development of two savanna tree species under simulated dry spells

The seedling stage represents a bottleneck in plants' life cycle, particularly in savanna environments, where the rainy season is the major window of opportunity for seedling development and recruitment of new individuals. However, an increase in the duration and frequency of dry spells (days without rain during the rainy season) is expected due to climate change, which may affect species recruitment and establishment. The aim of this study was to examine the effect of simulated dry spells on the growth performance and biomass of Qualea grandiflora and Tabebuia aurea seedlings. Seedlings (60 days old) were exposed to three irrigation treatments (daily irri-gation, irrigation every 8 days, and irrigation every 15 days) for 130 days. We found no mortality in any of the irrigation treatments for both species. Although the growth parameters of Q. grandiflora were not significantly affected by the dry spells, the species invested more in shoot growth than in root growth. In contrast, there was a significant decrease in the root dry mass, root:shoot ratio, root biomass fraction, and relative growth rate of T. aurea seedlings exposed to dry spells of 15 days; but there was a significant increase in the specific taproot length and shoot biomass fraction. Overall, the plants showed species-specific responses to the dry spell treat-ments. Further, T. aurea seedlings invested more resources in taproot growth in response to dry spells. The development of deep-reaching taproots could be an effective physiological adaptation strategy for the survival and establishment of young plants and the resilience of native tree populations under future adverse climate scenarios.

Automated summary

The growth performance and biomass of Qualea grandiflora and Tabebuia aurea seedlings were examined under simulated dry spells. While Q. grandiflora showed no significant response, T. aurea invested more in taproot growth to cope with future adverse climate conditions, ensuring the survival and establishment of the seedlings.