Rottenburg University of Applied Forest Sciences

Wood ash from small-scale (<1 MW) wood-fired heating plants represents a valuable secondary resource containing essential plant nutrients such as Ca, K, and P, but may also harbor potentially hazardous elements. Its current utilization and disposal are typically based solely on total elemental composition, disregarding element mobility and environmental behavior. This study introduces element mobility as an additional criterion for assessing ash quality and suitability for recycling. Sequential extraction using a modified BCR (Community Bureau of Reference) protocol with four solvents (water, acetic acid, hydroxylamine hydrochloride, and ammonium acetate) was applied to evaluate the leachability of 26 elements. Results indicate high extractabilities for several potentially hazardous elements—Sr (54 %), B (48 %), V (44 %), Cd (38 %), and Tl (27 %)—suggesting potential environmental risks despite low total concentrations. In contrast, key plant nutrients, especially P (15 %) were less mobile but could be mobilized under oxidizing conditions. While dissolution of K (74 %) and Ca (12 %) in water and weak organic acid indicates partial plant-availability already in the untreated ash, 26 % resp. 88 % remained in the residual fraction, indicating only long-term plant availability through weathering. The findings demonstrate that both total concentrations and leaching behavior must be considered in environmental assessments. For fertilizer production, pretreatment to remove Tl and enhance P solubility is recommended. From a waste management perspective, controlled ash processing can promote nutrient recovery and support circular economy objectives. These insights contribute to optimizing wood ash management strategies and minimizing environmental risks associated with its reuse. • Element mobility as a new criterion for assessment of wood ash as fertilizer. • Sequential extraction reveals wide variation of element leachability from ash. • P becomes extractable via oxidation with hydrogen peroxide and ammonium acetate. • Only Tl exceeds limits among toxic elements but can be selectively removed.

Radio telemetry offers new opportunities for studying the movement of insects. One important prerequisite for using radio tags to study butterfly movement ecology is that tag weight and attachment do not significantly affect butterfly flight performance. Despite recent applications of telemetry in butterflies, a systematic evaluation of tag-to-body-weight thresholds for successful tagging has been lacking. We tested ultra-light radio tags (0.13g) on 117 individuals of 18 butterfly species under greenhouse and field conditions. Tag-to-body-weight ratios ranged from 5.6% to 77.8%. We used generalized linear mixed-effects models to identify predictors of flight success and used ROC analysis to determine the critical tag-to-body-weight threshold. Tag retention was also compared between thoracic and abdominal attachment sites. We found that a threshold of approximately 20% of body weight marks a critical point beyond which flight performance declines significantly. Abdominal tag attachment proved more reliable and stable than thoracic attachment, with lower detachment rates. This study presents the first comprehensive evaluation of tag-to-body-weight thresholds and attachment methods in butterfly telemetry. The results provide practical guidance for planning radio telemetry studies of butterflies and for conducting further methodological research, such as into the effects of tagging on butterfly behavior, body condition, survival, and reproduction.

The Triad framework seeks to balance the economic and ecological functions in forested landscapes by combining intensively, extensively, and unmanaged areas, assuming a higher support to biodiversity in extensively rather than in intensively managed forests. We quantified the effects of Triad zoning on biodiversity in (sub)montane eutrophic European beech forests. Using a European-wide multitaxon database and a "virtual" landscape approach (i.e., by resampling empirical data), we evaluated how the proportion of Triad management categories affected the landscape-level species diversity of birds, saproxylic beetles, vascular plants, epiphytic bryophytes, lichens, and wood-inhabiting fungi, as well as multitaxonomic diversity. The results varied greatly among taxonomic groups. Multitaxonomic diversity peaked in landscapes composed of 60% unmanaged and 40% intensively managed forests. While intensive management can benefit some taxa through the creation of open habitats, unmanaged forests are the backbone of biodiversity conservation, underlining the need to safeguard the remaining old-growth forests under natural dynamics, and to extend the current area of unmanaged forests in Europe. Extensive forest management, however, did not contribute to biodiversity conservation as expected. As withdrawing such a high proportion of European forest landscapes from management is unfeasible given the increasing demand for timber, efforts are needed to increase the presence of structural features supporting biodiversity into extensively managed forests.

Abstract. Maintaining or increasing forest carbon sinks is considered essential for mitigating the rise in atmospheric CO2 concentrations. In contrast, harvesting trees is perceived as having negative consequences for both the standing biomass stocks and the carbon sink strength. However, the forest carbon sink needs to be examined from a forest stand canopy perspective, where assimilation predominantly occurs in temperate forests. Here we show that a threshold of leaf area exists beyond which additional leaves do not contribute to CO2 uptake. The associated biomass can be harvested without affecting the forest carbon uptake. Based on eddy covariance measurements, we show that CO2 uptake (gross primary production – GPP) and net ecosystem exchange (NEE) in temperate forests are of a similar magnitude in both unmanaged and sustainably managed forests, on the order of 1500–1600 gCm-2yr-1 for GPP and 542–483 gCm-2yr-1 for NEE. A threshold located between 3 and 4.5 m2 m−2 LAI (leaf area index) can be used for sustainable harvesting with regard to CO2 uptake. Simulations based on the LPJ-GUESS (Lund–Potsdam–Jena General Ecosystem Simulator) model reproduce the saturation of GPP and NEP and the convergence on the LAI threshold range. Accordingly, in temperate managed forests, trees can be harvested while maintaining a high tree biomass and carbon sink of the remaining stand. In this case, competition between neighboring trees in unmanaged forests is replaced by harvest management and provision of wood products. No difference in the LAI productivity response was observed between managed and unmanaged sites.

Accelerated global change, including land use change, is altering plant community composition and challenging conservation in protected areas (PAs) worldwide. Vegetation resurveys of quasi-permanent plots provide insights into these shifts over decades. However, resurvey studies are scarce in the temperate forests of the Andes in northern Patagonia, leaving questions on temporal vegetation dynamics unanswered. We resurveyed vegetation plots of three different forest types (mixed evergreen, coniferous and subalpine) located in Nahuel Huapi National Park >50 years after the original survey, in an area with current minimal but moderate to intense land use in the past. We applied multivariate analyses to assess changes in plant community composition and fitted generalized linear mixed models to compare temporal changes of different life forms and origin groups. Species gains and losses were analyzed by resurvey location and “winner” and “loser” species were identified. Our results indicate biotic homogenization of montane mixed evergreen and coniferous forests, ongoing understory closure and an increasing dominance of non-native species. Conversely, subalpine forests showed a more stable composition over time. These findings underscore the significance of legacy effects, i.e., land-use practices occurring decades ago having residual influences on the current biological composition. We conclude that without conservation management following intensive land use, such as non-native species removal, neither local nor global biodiversity conservation goals are likely to be met. • Resurvey of temperate Patagonian forests shows major shifts in plant communities over 50 years. • Coniferous and mixed evergreen forests exhibit composition change and an increasing resemblance between the types. • In contrast, subalpine forests show a more stable composition and an increase in woody species • Non-native species have increased in frequency, becoming apparent winners under global change. • Legacy effects of past land use still shape forest dynamics and challenge conservation goals.

Hinweis des Verlags Der Verlag bleibt in Hinblick auf geografische Zuordnungen und Gebietsbezeichnungen in veröffentlichten Karten und Institutsadressen neutral.

In continuous cover forestry, plenter silviculture is regarded as an elaborated system for optimizing the sustainable production of high-quality timber maintaining a constant but heterogeneous canopy. Its complexity necessitates high silvicultural expertise and a detailed assessment of forest stand structural variables. Terrestrial laser scanning (TLS) can offer reliable techniques for long-term tree mapping, volume calculation, and stand variables assessment in complex forest structures. We conducted surveys using both automated TLS and conventional manual methods (CMM) on two plots with contrasting silvicultural regimes within the Black Forest, Germany. Variations in automated tree detection and stand variables were greater between different TLS surveys than with CMM. TLS detected an average of 523 tree stems per hectare, while CMM counted 516. Approximately 9.6% of trees identified with TLS were commission errors, with 6.5% of CMM trees being omitted using TLS. Basal area per hectare was slightly higher in TLS (38.9 m3) than in CMM (38.2 m3). However, CMM recorded a greater standing volume (492.7 m3) than TLS (440.5 m3). The discrepancy in stand volume between methods was primarily due to TLS underestimating tree height, especially for taller trees. DBH bias was minor at 1 cm between methods. Repeated TLS inventories successfully matched an average of 424 tree positions per hectare. While TLS adequately characterizes complex plenter forest structures, we propose enhancing this methodology with personal laser scanning to optimize crown coverage and efficiency and direct volume measurements for increased accuracy of wood volume estimations. Additionally, utilizing 3D point cloud data-derived metrics, such as structural complexity indices, can further enhance plenter forest management.