Understanding mixed forest dynamics in a context of climate change
The frequency and severity of droughts are expected to increase in many regions of the world due to global climate change. Consequently, they become a major factor of widespread tree mortality, instigating a loss of carbon stored in forests that will feed back to exacerbate climate change. Modelling forest responses to drought is critical for predicting climate change socio-economic and ecological impacts and informing conservation strategies. Supported by the Marie Skłodowska-Curie Actions programme, the FORECAST project analysed the vulnerability of Hayedo de Montejo (Madrid, Spain) to climate change by combining field measurements with modelling.
Considering challenges in biodiverse ecosystems
Hayedo de Montejo is a mixed forest, located at the southern European limit for some iconic European tree species, such as beech and oaks. Notably, it is protected as a UNESCO World Heritage Site. “Natural variability in these mature mixed forests complicates model parameterisation, because inaccurate parameters result in incorrect model outputs, which do not represent plant responses adequately,” explains Marie Skłodowska-Curie research fellow, Martin Venturas. FORECAST found out that models generally perform similarly under unstressed conditions, but performance diverges under drought. This led the team to give a special focus on merging underutilised measurements with new analytical tools to evaluate the ecosystem’s functional response to drought stress. “A challenge that we are still trying to resolve is how long-lived organisms such as trees adapt to new environmental conditions and determining if they will be able to keep up with such rapid changes,” adds project coordinator Rosana López.
Understanding forest dynamics through plant water and carbon relations
The most innovative aspect of FORECAST is the application of hydraulic traits-based models to natural mixed forests for guiding their management. Due to climate change, Mediterranean forests are subject to a growing decrease in water. Hayedo de Montejo features the typical characteristics of the mixed Mediterranean forest and presents extreme vulnerability, comprising an ideal location for a case study on mixed forests. The developed model and measured tree traits by FORECAST are expected to allow forest managers to explore how different treatments will affect forest resilience. The researchers evaluated several model formulations for coupling plant hydraulic and stomatal response using functional performance metrics. Moreover, they took into consideration the structural differences among models reflected on the information from soil water potential and vapour pressure deficit to transpiration. FORECAST highlighted the need for further research on the role of parameters and more flexible representations of the broad spectrum of isohydric behaviours. Given the pivotal role of canopy temperature in simulating metabolic processes, more effective models that capture the divergence of canopy temperature from air temperature should be prioritised. “Ideally, we would like the developed model to apply to any mixed forest, especially in regions where water is the most limiting resource, such as the Mediterranean basin,” says López. “This model also has the potential to predict carbon sequestration and plant growth, which is particularly valuable for estimating forests’ carbon sink and productivity. This directly links our research to the European Green Deal.”
Keywords
FORECAST, mixed forest, forest management, climate change, Mediterranean, Marie Skłodowska-Curie Actions
