OptFor-EU partners have just published three new scientific articles: Modelling branch surface area of Fagus sylvatica L., Early-successional species show higher tolerance of drought than late-successional species across Europe and Causes and Impacts of Flood Events in Emilia-Romagna (Italy) in May 2023. The three articles were mainly authored respectively by the OptFor-EU partners BOKU, INCDS and CNR and were published respectively on the Scandinavian Journal of Forest Research, Science of The Total Environment and in the Section Land Systems and Global Change in Land 2024. The full abstracts of the three articles is available below, together with their direct links.
Modelling branch surface area of Fagus sylvatica L.
Allometric models describe properties of trees that are difficult to measure. Here, we provide a set of allometric models for estimating branch properties for European beech (Fagus sylvatica L.). Branches affect rainfall and snow interception, provide habitat for other organisms and contribute to the economic and aesthetic value of trees. Using randomized branch sampling (RBS) of 27 beech trees in Austria we developed models for branch surface area, branch number, branch base diameter and branch length, depending on stem diameter, tree height and crown ratio. For individual branches, branch diameter was the best predictor of branch surface area while including branch length or position along the stem did not improve the models. For the entire tree, stem diameter was the most important predictor. Branch surface area (and in consequence also branch volume) assessed by RBS was greater than the branch surface area estimated as a cylinder from measurements of branch length and branch base diameter. Since the branch allometry of beech differs considerably from a previous study on branches of Picea abies, we conclude that assumptions and models derived from other tree species can lead to considerable biased results in assessing the functions of tree branches.
Early-successional species show higher tolerance of drought than late-successional species across Europe
Climate change is exacerbating forest disturbances through more frequent and more intense droughts and fires, undermining their ability to recover from such disturbances. The response of fast-growing early-successional species to drought is poorly understood, despite their key role in ecological succession and their ability to enhance ecosystem resilience. Here, we compared the growth responses to drought events of three early-successional species (silver birch, black poplar, and Scots pine) with that of one late-successional species (European beech) across their natural distribution ranges in Europe. We used tree-ring widths of 6340 trees from 109 forest sites to establish species-specific tree-ring chronologies. We then used multiple linear regression to analyze which climatic or growth variables (pre-drought growth and growth during drought) best explained the tree responses to drought. Silver birch, Scots pine, and black poplar showed superior drought tolerance, with a slight, non-significant growth reduction under drought, whereas European beech showed a significant decrease in growth. The variables that influenced growth during and after the drought were species-specific. Annual precipitation and growth variables were key predictors of post-drought growth for Scots pine, black poplar, and European beech. Scots pine and silver birch grew better with increasing latitude, i.e., in Northern Europe than in Central Europe, while European beech and black poplar showed more growth at sites with high precipitation during the vegetation and dormant period, respectively. This study provides insights into the drought tolerance of early-successional species and highlights their ability to promote ecological succession and facilitate the transition to drought-resistant, late-successional forest ecosystems.
Causes and Impacts of Flood Events in Emilia-Romagna (Italy) in May 2023
On 1–3 May 2023, severe hydro-meteorological events occurred in the Italian Emilia-Romagna region. Such events caused extensive flooding, landslides, isolation of many areas, evacuation of many families, and severe damage to infrastructure, agriculture, buildings, and essential services. Several municipalities were affected, thousands of civilians had to be evacuated, and losses of life occurred. The consequences beyond the recorded immediate impacts on infrastructure and life were impressive, and extended to the regional economy, specifically in the Fruit Valley, where, in addition to immediate yield losses, long-term damage to orchard production is expected due to persistent flooding. The civil and cultural building heritage has also been heavily affected, both in the countryside and in inhabited centers. Some of the damage, direct and indirect, caused by flooding on buildings will also see an evolution in the medium- to long-term that needs to be addressed. This paper analyzes the manifold aspects of such an atmospheric phenomenon and its impacts to understand the potential increasing occurrence of similar events in the climate change context.