Environmental thresholds for drought- and heat-related tree mortality

Introduction

One of the most pressing ecological questions is how trees and forests can survive in increasing intensity and frequency of droughts and extreme heat. Wide-spread drought-related tree mortality has been witnessed globally over the last decade, and in 2022, Europe suffered from the worst drought in 500 years. Understanding and predicting the impact of drought and heat on tree mortality is limited due to a lack of knowledge on the environmental conditions that lead to tree mortality.

Research Objectives

For the first time, it is feasible to quantify spatial and temporal tree mortality patterns and capture tree structure and species over large geographic regions at the individual tree level. This enables me to aim to uncover environmental thresholds and key environmental drivers of drought- and heat-related tree mortality at the species level for various forest biomes.

Methodology

The use of state-of-the-art remote sensing and deep learning methods allows me to capture where, when, and what kind of trees (species, structure) have died for tens of millions of trees to increase our understanding of spatial and temporal tree mortality patterns.

1. My approach uses laser scanning data to provide detailed tree 3D characterization.
2. It calculates tree position within the tree community (competition) and the landscape (water availability, microclimate).
3. Then, combining these variables with information on tree xylem vulnerability, pest insects, soil temperature, and climate, we can ultimately reveal species-specific environmental thresholds and key drivers of drought- and heat-related tree mortality.

Impact of Research

This research will open new horizons, bringing ecophysiology, remote sensing, forest ecology, and entomology together. It will develop methods to quantify drivers of tree mortality in much greater depth than has been possible to date.

From these findings, we will be able to inform forest managers and policymakers which forests are at risk, ultimately increasing the resilience of future forests.