• Energy Research

Aboveground carbon (C) sequestration in trees is important in global C dynamics, but reliable techniques for its modeling in highly productive and heterogeneous ecosystems are limited. We applied an extended dendrochronological approach to disentangle the functioning of drivers from the atmosphere (temperature, precipitation), the lithosphere (sedimentation rate), the hydrosphere (groundwater table, river water level fluctuation), the biosphere (tree characteristics), and the anthroposphere (dike construction). Carbon sequestration in aboveground biomass of riparian Quercus robur L. and Fraxinus excelsior L. was modeled (1) over time using boosted regression tree analysis (BRT) on cross-datable trees characterized by equal annual growth ring patterns and (2) across space using a subsequent classification and regression tree analysis (CART) on cross-datable and not cross-datable trees. While C sequestration of cross-datable Q. robur responded to precipitation and temperature, cross-datable F. excelsior also responded to a low Danube river water level. However, CART revealed that C sequestration over time is governed by tree height and parameters that vary over space (magnitude of fluctuation in the groundwater table, vertical distance to mean river water level, and longitudinal distance to upstream end of the study area). Thus, a uniform response to climatic drivers of aboveground C sequestration in Q. robur was only detectable in trees of an intermediate height class and in taller trees (>21.8m) on sites where the groundwater table fluctuated little (≤0.9m). The detection of climatic drivers and the river water level in F. excelsior depended on sites at lower altitudes above the mean river water level (≤2.7m) and along a less dynamic downstream section of the study area. Our approach indicates unexploited opportunities of understanding the interplay of different environmental drivers in aboveground C sequestration. Results may support species-specific and locally adapted forest management plans to increase carbon dioxide sequestration from the atmosphere in trees.

The development of strategy and tactics for reforms in the energy industry involves the identification of benchmark countries whose experience can form the basis of a quantitative assessment of the main targets of the reforms. The basis for such decisions can be the results of the integrated assessment of energy reforms in the EU countries for 2010–2021. This study aims to cluster these countries according to the integral indicator and determine specific directions in which the respective country needs to make progress in moving to another cluster. Thus, based on a linear model, the Fishburn formula, and variance analysis, 10 energy development indicators were combined into a single indicator that characterizes the effectiveness of energy reforms (for example, in 2021, it was the highest in Austria (0.612), Germany (0.644), and France (0.620); the lowest – in Latvia (0.383) and Croatia (0.369)). Based on this indicator, countries were clustered using the k-means method. Four clusters were formed: representatives of the highest first (Austria, Germany, France, Spain, Sweden, and Luxembourg) are strategic benchmarks for all EU countries, and representatives of other clusters are tactical benchmarks for countries from lower clusters. The average values of all 10 indicators of energy development were calculated. Their low values are a sign that this direction should be a priority when carrying out reforms, and their quantitative estimates can be used as specific targets when setting strategic and tactical tasks (transition to a higher cluster or achieving average values in one’s cluster). AcknowledgmentThe research was funded by a Fellowship agreement for a research fellowship in the framework of the 11th funding round within the Philipp Schwartz Initiative of the Alexander von Humboldt Foundation.