Abstract
Forests provide important ecosystem services but are being affected by climate change, not only changes in temperature and precipitation but potentially also directly through the plant-physiological effects of increases in atmospheric CO2. We applied a tree-species-based dynamic model (LPJ-GUESS) at a high 5-km spatial resolution to project climate and CO2 impacts on tree species and thus forests in Great Britain. Climatic inputs consisted of a novel large climate scenario ensemble derived from a regional climate model (RCM) under an RCP 8.5 emission scenario. The climate change impacts were assessed using leaf area index (LAI) and net primary productivity (NPP) for the 2030s and the 2080s compared to baseline (1975–2004). The potential CO2 effects, which are highly uncertain, were examined using a constant CO2 level scenario for comparison. Also, a climate vulnerability index was developed to assess the potential drought impact on modeled tree species. In spite of substantial future reductions in rainfall, the mean projected LAI and NPP generally showed an increase over Britain, with a larger increment in Scotland, northwest England, and west Wales. The CO2 increase led to higher projected LAI and NPP, especially in northern Britain, but with little effect on overall geographical patterns. However, without accounting for plant-physiological effects of elevated CO2, NPP in Southern and Central Britain and easternmost parts of Wales showed a decrease relative to 2011, implying less ecosystem service provisioning, e.g., in terms of timber yields and carbon storage. The projected change of LAI and NPP varied from 5 to 100% of the mean change, due to the uncertainty arising from natural weather-induced variability, with Southeast England being most sensitive to this. It was also the most susceptible to climate change and drought, with reduced suitability for broad-leaved trees such as beech, small-leaved lime, and hornbeam. These could lead to important changes in woodland composition across Great Britain.
Highlights
Forest ecosystems play a critical role in global carbon cycling and ecosystem service provision (Seddon et al, 2019)
The projected mean change in leaf area index (LAI) summed across all tree species and plant functional types (PFTs) over Britain ranged from 0.25 to 2.24 in the 2030s and from 0.9 to 4.2 in the 2080s (Figures 2A,B)
In both CO2 settings, the simulated areas of greatest LAI change occur in Scotland and northern England, as conditions become more suitable for deciduous tree species to grow under the warming climate
Summary
Forest ecosystems play a critical role in global carbon cycling and ecosystem service provision (Seddon et al, 2019). Extreme events are of particular interest as they can help improve the understanding of phenological and physiological responses of tree species for better planning of management options. These studies are based on the observed stress signs of plant species, such as canopy dieback (Carnicer et al, 2011), growth condition (Van der Werf et al, 2007; Hogg et al, 2008; Pasho et al, 2011; Eilmann and Rigling, 2012), leaf coloring and decline (Leuzinger et al, 2005), and mortality (Bigler et al, 2006, 2007; Senf et al, 2018). In the United Kingdom, there are some observations of climate change impacts and especially drought on forests and tree species (e.g., Peterken and Mountford, 1996; Mountford et al, 1999; Green et al, 2008; Cavin et al, 2013), while a few studies have investigated impacts on tree growth, but they have been limited to a few species (Petr et al, 2014)
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