Research

Increasingly frequent severe drought events are pushing Mediterranean forests to unprecedented responses. Lack of management leads to dense forests that are highly susceptible to water stress, potentially resulting in extensive dieback and increased vulnerability to other disturbances such as insect outbreaks and wildfires. Forest treatments such as thinning and prescribed fire can enhance tree growth and reduce tree vulnerability to severe disturbances. Here, we used tree rings to study growth and the physiological response of dominant black pine (Pinus nigra) forests to drought events in north-eastern Spain under different treatment combinations, including two thinning intensities (light and heavy, with 10% and 40% basal area reduction, respectively), two understory treatments (mechanical clearing and mechanical clearing plus prescribed burn of the debris), and an untreated control. Specifically, we studied basal area increment (BAI), resilience indices, and intrinsic water use efficiency (iWUE) using carbon and oxygen stable isotopes (δ13C and δ18O) before and after treatments. Our results showed that BAI and resistance to drought increased in the heavy-thin (burned and unburned) and light-thin burned units. Resilience increased in burned treatments regardless of the thinning intensity, while recovery was not affected by treatment. Within each thinning treatment, prescribed fire additionally increased BAI in the light-thin and resistance and resilience in the heavy-thin. The stable isotope analysis suggested that δ13C and iWUE were more influenced by year than treatment and that δ18O was positively correlated to growth during the drought after treatments. No change in iWUE among treatments was presumably linked to a proportional increase in both photosynthetic rate and stomatal conductance. These physiological processes were particularly enhanced in the heavy-thin (burned and unburned) and light-thin burned units, indicating that these trees were the least affected by drought after treatments. This study shows that management approaches primarily aimed at reducing wildfire hazard can also contribute to enhancing physiological activity of dominant trees under drought stress. By reducing competition both from the overstory and the understory, thinning and debris burning promote tree growth and vigour, and increase its resistance and resilience to drought. Active forest management should be encouraged to reduce vulnerability of sub-Mediterranean pine forests to severe and recurrent drought events in the face of climate change.

Wildfire CE’s primary objective is to enable border regions, the communities and landscapes within them, to prepare, respond and adapt to the increasing wildfire risk resulting from climate change. The project will change the way we assess and manage fire risk in the border regions and the wider territories. Through cooperation across borders, sharing knowledge and experience it will lead to a more integrated, targeted and inclusive approach in dealing with this increasing threat. Until now, the management of wildfire risk has been conducted at the territorial level, with mismatched approaches to fire warning levels, land management and communication of risk. The mapping of fuels and propagation potential is seldom conducted at the territorial level, let alone across borders. WildfireCE will map these fuels, fire behaviour and propagation potential across borders, it will identify where actions are necessary, what those actions are and it will implement those actions in Pilot Regions. In Work Package 1 the activities identifying risk, best practice and spatial information will lead to the creation of a manual for assessing wildfire risk in CE border areas. This solution to the problem of limited information at a strategic level in managing risk will benefit local/regional authorities, sectoral agencies, infrastructure providers and of course the public at large. Work Package 2 uses the information from WP1 alongside additional work to identify risk and priority areas, better access and resource mapping for use in an on-line platform, which enables planning authorities and emergency services amongst others to better target actions and resources to reduce risk. This output will be tested as a Pilot Action in the Pilot Regions. The data within the platform will be available to the territories’ for integration in existing regional /national platforms. Based on the findings of WP1 and WP2, WP3 alongside regional stakeholders, will develop and implement action plans for the Pilot Regions. Finally, a strategy will be produced aimed specifically at transferring the findings, lessons and approaches to other regions and territories.

The invasive Tree-of-Heaven (Ailanthus altissima) is increasingly migrating into habitat types worthy of protection, where, due to its rapid growth, its low soil, site and climate requirements, its high capability of reproduction via root suckers and stump sprouts, its strong vegetative reproduction and massive production of seeds and due to its allelopathic properties, it endangers rare plant species and associated animal species. In the present project, an attempt is being made to combat invasive Tree-of-Heaven on the dry grassland site Dürrham (Heißlände) in the Lower Lobau, which is worthy of protection, and in the FFH habitat types 91G0 (Pannonian oak-hornbeam forest), 91H0 (Pannonian downy oak forest) and in the FFH habitat type 6210 (Trespen-fescue-limestone dry grassland) on the Bisamberg, respectively. Furthermore, soil as well as potentially susceptible dicotyledonous plants will be sampled and screened for the agent V. nonalfalfae (see below) on both sites in spring 2024 and 2025. The control is to be carried out using the biological control method developed at the Institute of Forest Entomology, Forest Pathology and Forest Protection (BOKU University) in 2011 on the basis of the native wilt fungus Verticillium nonalfalfae, which has already proven to be sustainable, cost-efficient, but also quickly and specifically effective in numerous series of experiments. The control is therefore also in line with the biodiversity strategy Austria 2030+ of the BMK.