Predicting the impact of drought and increased temperatures on boreal forest ecosystems in Norway

Climate change can pose major challenges for Norwegian forests. Rising temperatures and a longer growing season can increase tree growth and productivity however, a more variable climate will mean that trees experience more frequent and extreme periods of drought, late spring frosts, heat waves and pathogens. Worryingly, we know very little about how our forests respond to these changes. To better understand how Norwegian forests respond to the warming climate, we need to monitor how individual trees react to changes in temperature and water availability in real-time. To do this, we will establish a long-term forest monitoring and research network on spruce forests across Norway. We will attach dendrometers to trees all over the country to measure tree growth and monitor drought stress. A dendrometer is a measuring device that is fixed around the tree and measures small changes in the diameter of the tree trunk as water availability, weather and other factors change throughout the day and season. Tree growth and climate data collected every 30 minutes from the monitoring sites, together with mapping data from drones and satellites, will enable us to create tools that automatically interpret changes in the spruce's health, growth and drought stress. The result is a near-real-time insight into what is happening in Norway’s forests. This real time tree information will be made publicly available through a website where the user can navigate on a map and follow spruce's growth and water intake "minute by minute", providing important information for researchers, forest managers and other decision-makers. In the short term, this can be used to predict risk of bark beetle attack or where it is necessary to thin to give more water to remaining trees. In the longer term, it will teach us which areas the trees cope well even in dry periods, or if the forest owner should invest in tree species that tolerate water shortages better.

The boreal zone is warming twice as fast as the global average due to climate change, but the ways in which forest ecosystems are responding to these rapidly changing conditions is poorly understood. On one hand, increases in mean temperatures and growing season length are expected to increase boreal forest growth and productivity. On the other hand, increased climate variability and extremes such as drought, late spring frosts, heat waves and pathogens have the potential to counteract such positive impacts of warming. The aim of PREDICT is to establish a state-of-the-art, long-term forest monitoring and research network for Norway. We will concentrate on spruce-dominated forests and on covering the climatical gradients of such ecosystems in Norway. At the core of this project is the creation of BorealNet, where autonomous, high frequency dendrometers will be installed at key sites across Norway, generating high temporal resolution datasets of tree growth, health, and tree water dynamics. Long-term trends as well as fine scale feedbacks between tree growth, climate, water balance and soil will be investigated to provide a mechanistic understanding and fill information gaps in the key drivers of spruce forest health. We will link individual tree growth data to entire landscapes through remotely sensed vegetation and climate data and in turn, the high-quality and long-term growth data sets obtained from BorealNet will form the basis of ground truthing and validation for remote sensing models and algorithms. Ultimately, we will create online-tools to automatically interpret stem radius fluctuations in terms of tree water deficit, wood growth and related indicators for forest ecosystem carbon sink and drought stress providing a wholistic and near-real time insight into forest ecosystem responses to climate change across Norway. This information will be made publicly available and will greatly benefit researchers, forest managers and other decision makers.