During the 2013 drought, the most noticable impact on the kauri forest was the increase in litterfall. It’s well established that many tree species lose their leaves in response to drought, leading to decreased plant water loss. Deciduous trees may lose their leaves early while semi deciduous trees may lose more leaves in a dry year. By reducing leaf area, trees reduce the aarea of water-losing surfaces, thereby reducing overall water loss.
In a recently accepted paper in Plant Ecology, we report that litterfall increased 72% in 2013 compared to 2012 because of dry soil conditions (see figure). Most of the extra litter was kauri leaf and twig material.
Kauri are known to self-prune branches but the reason for branch abscission has been unclear. It may be that this costly process occurs to protect the highly vulnerable hydraulic system of these forest giants. During dry periods, trees through off twigs to prevent failure of the water conducting system of the plant.
We are doing ongoing monitoring to determine the lag impact of this massive biomass loss to the forest floor.