University of Göttingen

We describe the identification of an active Ti(salen) catalyst for the radical arylation of epoxides by a cyclic voltammetry study of mechanism‐based predictors, such as the redox potentials of the complexes and their EqCr‐equilibria, for the success of catalysis. Surprisingly, by far the most active catalyst features an uncommon tetrasubstituted ligand backbone, which renders chloride binding to the active Ti(III) species less favorable, thereby increasing catalyst activity due to improved substrate binding. Catalysis is most efficient in the “green” solvent ethyl acetate and can be initiated using base metals as well as electrochemical methods for the reduction of the Ti(salen)‐precatalyst. Compared to the commonly employed titanocene catalysis, the use of the newly developed Ti(salen) catalyst allows for the use of milder and more sustainable reactions conditions, a broader substrate scope, and facile modification of the catalyst's electronic and steric properties.

Since their invention in the early 1900s, synthetic polymers have experienced significant growth due to their lightweight nature, affordability, resistance to corrosion, durability, and chemical stability against certain reactions (Sharma et al. 2017). As a result, plastic polymers have replaced various traditional materials like wood, ceramic, glass, and metal. A 2018 report indicated that global plastic production reached 348 million tons (Plastics Europe 2018), with projections suggesting it could reach 33 billion tons by 2050 (Rochman et al. 2013). Due to inadequate waste management, a substantial amount of plastic ends up in terrestrial and aquatic environments, where it persists for long periods. Each year, over eight million tons of plastic debris pollutes both standing and flowing water systems (Choudhury et al. 2022; Liu et al. 2022).

In recent years, climate change has caused an unprecedented wave of tree mortality across Europe, reshaping forest canopy cover and deadwood structures. Nevertheless, the effects of tree mortality on species‐rich groups, such as insects are still unclear, mainly because few replicated disturbance experiments exist and most studies focus on small taxonomic subsets of the species‐rich class of insects, both of which prevent generalization. To disentangle the effects of canopy cover and deadwood on total above‐ground insect diversity collected with Malaise traps, we experimentally applied different disturbance treatments in 11 commercial forests throughout Germany. We quantified taxonomic (TD) and phylogenetic diversity (PD) among 22,889 operational taxonomic units from 362 insect families along Hill numbers (q = 0, 1, 2) using metabarcoding, and standardized diversities by sample coverage as an objective measure of sample completeness. Our results showed a systematically lower sample coverage in canopy gaps compared with closed canopy forests, highlighting that the true diversity in open forest habitats is underestimated in bulk samples if sample coverage is not considered. Controlled for sample coverage, TD increased by up to 47% in canopy gaps with deadwood, compared with controls under closed canopy and without deadwood. The increase in TD was accompanied by a similar increase in PD only in rare species (q = 0), underlining the gain in evolutionary diverse communities of rare species, but redundancy in dominant species (q = 2). Synthesis and applications. Our experiment provides strong evidence for the importance of clustered tree mortality for comprehensive insect diversity in temperate forests and highlights the potential of forest management to enhance insect diversity in homogeneous commercial forests, particularly through the creation of canopy gaps and the retention of deadwood. Both mimic natural dynamics and can support rare species along with the ecosystem functions they may provide.

Agricultural soils offer great potential for carbon sequestration through humus formation. One way to motivate farmers to build up humus is through humus programs. These are still at an early stage of development, poorly explored, and the number of participating farmers is low. Our aim is to explain the heterogeneity of farmers' willingness to participate in humus programs by typologizing them according to different design preferences and socioeconomic backgrounds. To this end, we conducted a survey with German farmers including a discrete choice experiment and questions about environmental awareness, profit orientation and farm characteristics. We summarized farmers' attitudes towards for example, climate change with a factor analysis and included the results into the latent class model we used to analyze the discrete choice experiment. The farmers surveyed can be divided into four classes. The results show that the classes differ in the farmers' preferences for the characteristics of a humus program, for example, type of reference value and program duration, and according to the factors of the factor analysis, for example, advocacy of humus programs. The classes distinguish between disinterested and motivated farmers, farmers focusing on safe money and farmers focusing on quick money. With this study, we improve the understanding of farmers' acceptance of humus programs, which is essential before starting targeted (political) efforts.

Component-wise gradient boosting algorithms are popular for their intrinsic variable selection and implicit regularization, which can be especially beneficial for very flexible model classes. When estimating generalized additive models for location, scale and shape (GAMLSS) via a component-wise gradient boosting algorithm, an important part of the estimation procedure is to determine the relative complexity of the different submodels. Shrunk optimal step lengths have been suggested to replace small fixed step lengths for a non-cyclical boosting algorithm limited to a Gaussian response variable in order to achieve a similar degree of regularization in the submodels. In this article, we propose a new adaptive step length approach that accounts for the relative size of the fitted base-learners to ensure a natural balance between the different submodels. The new balanced boosting approach thus represents a computationally efficient and easily generalizable alternative to shrunk optimal step lengths. We implemented the balanced non-cyclical boosting algorithm for a Gaussian, a negative binomial as well as a Weibull distributed response variable and investigate the performance of the new approach in a simulation study, for count data of doctor’s visits as well as for survival data in an oncological trial. Both the simulation results and the applications show that the new approach yields similar results to shrunk optimal step lengths, especially with respect to the balance in the overall model. An improvement in the computational efficiency compared to numerically obtained shrunk optimal step lengths is especially evident for the Gaussian and negative binomial setting.

This study aims to identify the structural and compositional differences between native and exotic woodlands on Terceira Island, Azores. Based on landscape, habitat, and microhabitat analyses, remnants of native forests appeared to be associated with less accessible terrains. A more homogeneous structural complexity is exhibited, derived from the numerous branching patterns of the endemic vascular plant species. In contrast, exotic forests exhibit structural heterogeneity driven by mixed non-indigenous vascular plant species as a result of human actions such as afforestation and latter invasion of exotic tree species, after abandonment of the agricultural use. The ground and canopy layers in exotic forests were more invaded by non-indigenous species, while the understory demonstrated greater resilience by being mostly composed of indigenous species. Our findings highlight the structural and ecological differences between native and exotic woodlands, reflecting the historical transformation of forest cover in the Azores. These insights emphasize the importance of long-term monitoring and structural assessments in informing conservation efforts aimed at preserving native forests and managing invasive species in exotic woodlands.

Survival of multicellular organisms requires the coordinated interplay between networks regulating gene expression and controlled intracellular transport of respective regulators. Velvet domain proteins are fungal transcription factors, which form various heterodimers and play key roles in controlling early developmental decisions towards more either asexual or sexual differentiation. VeA is the central subunit of the trimeric velvet complex VelB-VeA-LaeA, which links transcriptional to epigenetic control for the coordination of fungal developmental programs to specific secondary metabolite synthesis. Nuclear localization of the VeA bridging factor is carefully controlled in fungi. In this work we demonstrate that VeA carries three nuclear localization signals NLS1, NLS2 and NLS3, which all contribute to nuclear import. We show that VeA has an additional nuclear export sequence (NES) which provides a shuttle function to allow the cell to relocate VeA to the cytoplasm. VeA is nuclear during vegetative growth, but has to be exported from the nucleus to allow and promote asexual development. In contrast, progression of the sexual pathway requires continuous nuclear VeA localization. Our work shows that an accurate nuclear import and export control of velvet proteins is further connected to specific stability control mechanism as prerequisites for fungal development and secondary metabolism. These results illustrate the various complex mutual dependencies of velvet regulatory proteins for coordinating fungal development and secondary metabolism.

Pollinators face significant global decline due to agricultural intensification. Local conservation measures (CMs), such as an annual flower field, an organic crop field, or a perennial semi‐natural habitat (SNH), are implemented to counteract this negative trend, with variable success, as local CMs may not support ecological processes at spatially larger landscape scales. This can be achieved by planning CMs at the landscape level (landscape CMs), for example multiple fields with a specific CM or combinations of different types of CMs. However, interactive effects between combined landscape CMs may limit their efficacy. It remains unclear whether multiple combined landscape CMs can be more efficient than single landscape CMs (synergistic effect), reduce each other's effectiveness (antagonistic effect) or sum together (additive effect) to promote biodiversity. We assessed the interactive effects of three landscape CMs: organic crops, annual flower fields and perennial SNH, on wild bee species richness and densities at the landscape scale. We surveyed wild bees within multiple transects in 32 landscapes and upscaled bee densities to the landscape scale. We observed a synergistic effect between landscape‐scale organic crops and perennial SNH. Specifically, non‐Bombus wild bee densities increased with higher area shares of organic crops in landscapes with high area shares of perennial SNH. This is likely due to their provision of complementary resources. For bumblebees, we found an additive effect of organic crops and perennial SNH, suggesting that bumblebees benefit from both landscape CMs regardless of their respective availability. However, antagonistic effects were more common, for example between landscape‐scale annual flower fields and organic farming, both providing similar floral resources and disturbance regimes. Only in landscapes with a low area of annual flower fields did bee densities and species richness increase with area shares of organic crops. Synthesis and applications. Interactive effects of combined landscape CMs determine landscape‐scale bee densities and species richness. In particular, functionally different and complementary resources of landscape CMs can create synergistic effects while antagonistic effects occur when similar resources are provided in different landscape CMs. Hence, we recommend that future bee conservation schemes should use smart mixing of landscape CMs, based on judicious evaluation to maximize complementary benefits and reduce redundancy with respect to landscape‐scale floral resources and provision of nesting habitat, while considering the habitat requirements of different bee taxonomic groups.

The small-farm sector is home to many of the world's food-insecure and undernourished people. Strategies to make smallholder farming more nutrition-sensitive often focus on agricultural diversification. In addition, women's empowerment is widely considered useful to improve diets and nutrition. Many studies have analyzed the effects of farm production diversification and of women's empowerment on dietary outcomes, but mostly in separate strands of literature. Here, we connect these strands to contribute to a better understanding of the multifaceted links between farm production diversity, women's roles in decision-making, and household diets. Using primary data from Malawi, we show that women's decision-making is positively associated with farm production diversity and with household dietary diversity. Furthermore, women's decision-making increases the positive association between farm production diversity and dietary diversity. We also differentiate between different domains of decision-making, including agricultural production, market sales, cash income control, and food purchases. The results suggest that strengthening women's agency can make smallholder farming more nutrition-sensitive through multiple channels.

Hemp cultivation is experiencing a resurgence in Europe, with the European Commission identifying it as a strategic crop for achieving Green Deal objectives. This study investigates opportunities and challenges of hemp cultivation from German farmers' perspectives across all three sustainability pillars. We conducted qualitative interviews with 14 agricultural enterprises across northern Germany in 2024, analyzing data through deductive category formation. Economic findings reveal opportunities through diversified revenue streams and reduced input costs, though scale requirements and market uncertainties present challenges. Ecologically, farmers confirm hemp's benefits for soil health and reduced chemical inputs, while noting specific management requirements for water and soil conditions. Social acceptance is improving when hemp is effectively distinguished from the drug cannabis, though regulations and conservative attitudes remain barriers for adoption. Success in hemp cultivation requires establishing stable market structures, developing region-specific management practices, and implementing effective knowledge transfer programs. This study provides the first comprehensive analysis of European farmers' experiences with hemp cultivation and offers practical insights for policymakers, farmers, and industry stakeholders while connecting farmer perspectives with European Green Deal objectives.

The rhizosphere priming effects (RPE) influence soil organic carbon (SOC) decomposition at the root-soil interface. However, whether different tree species affect the direction and intensity of RPE has been rarely studied. The RPE was measured from the fine roots of three coniferous and four broadleaved trees with a mean age of 20 years by utilizing the ¹³C natural tracing technique after 135-day in situ incubation. The released carbon dioxide (CO2) from the root-soil system was trapped using an improved CO2 trapping system. The fine root RPE of broadleaved trees is negative, ranging from − 43% to − 21%. Conversely, the fine root RPE of coniferous trees is positive, ranging from 34% to 58%. The fine root non-structural carbohydrates, including soluble sugars, sucrose, and starch, in coniferous trees were all lower than in those of broadleaved trees. The non-structural carbohydrates, such as starch and soluble sugars, are the most critical factors driving the RPE of fine roots on SOC decomposition. Therefore, the direction and degree of the RPE from fine roots of tree species can be used as a reference index for selecting tree species in afforestation, especially under the broad context of carbon neutrality.

Objectives Lipomatous soft-tissue tumors present a diagnostic burden. The aim of this work was to compare standard operating procedures (SOPs) for the diagnostic management of lipomatous soft-tissue tumors among European academic centers. Methods Experts of the Soft Tissue and Bone Sarcoma Group of the European Organization for Research and Treatment of Cancer were asked for their SOPs in the diagnosis of adipocytic soft-tissue tumors in an otherwise healthy patient. The answers were converted to decision trees and subsequently compared using the objective consensus methodology. Mediastinal and retroperitoneal lipomatous tumors were excluded from the analysis. Results The highest consensus (93%) among fourteen institutions was noted for evaluation with core needle biopsy (CNB) as SOP for lipomatous tumors located deep in tissue exceeding 7 cm and tumor-associated symptoms. Evaluation of heterogeneous features on imaging by CNB usually showed a consensus rate of at least 75%. Consensus was less likely for lipomatous tumors without symptoms or heterogeneous features. In these settings, CNB and follow-up were almost equally recommended. For lipomatous tumors smaller than 3 cm, without growth or symptoms, no localization in the trunk, and homogeneous imaging features, a consensus rate of 71% was achieved for follow-up. Conclusions SOPs for diagnostic work-up of lipomatous tumors varied despite their geographical proximity. The highest consensus for biopsy was for deep large tumors with associated symptoms. For follow-up, consensus was shown for small homogenous tumors outside the trunk, without growth or symptoms. Consensus on resection involved homogeneous deeply located small tumors outside the trunk with growth and symptoms. Critical relevance statement This study identifies the decision-making criteria with the highest consensus rate among participating academic sarcoma centers in diagnosing lipomatous tumors: tumors located deep in the tissue, a tumor size exceeding 7 cm, and associated symptoms emerge as pivotal criteria. Key Points Standard operating procedures for diagnostic work-up of lipomatous tumors among fourteen sarcoma centers were analyzed. Identified diagnostic criteria are: imaging features, size, growth, symptoms, superficial and trunk location. The highest consensus concerned recommending biopsies for deep tumors > 7 cm with associated symptoms. Graphical Abstract

Mulching with plant residues is one of the most effective means to increase soil organic C (SOC) in croplands. The mechanisms through which microorganisms transform plant-derived C into SOC under mulching conditions remain unclear. Soil properties (contents of SOC, dissolved organic matter (DOM), and microbial necromass C (MNC)) without mulching were compared with those of soils after 12 years of mulching with perennial ryegrass (Ryegr) and crop straw (Straw). Mulching with Straw increased SOC content by 83% and MNC by 129% compared with the Control, due to the high input of organic matter. The content of stable DOM compounds increased, indicating that straw mulching decreased the availability of organic matter for microorganisms. Straw mulching increased the abundance of copiotrophic bacteria and Ascomycota compared with the Control. Over 12 years, Ryegr mulching increased SOC by 14% and MNC by 29% compared with the Control. The bioavailable DOM compounds under Ryegr mulching increased compared with the Control, but the bacterial community composition remained unchanged. As microorganisms preferentially decomposed and utilized C derived from straw residues, Straw mulching increased SOC content by raising biologically refractory DOM compounds and formation of stable microbial necromass. Ryegr mulching stimulated microbial in vivo turnover by increasing bioavailable DOM compounds, which in turn increased microbial necromass C and SOC accumulation. This was reflected by an increase in microbial functions related to the metabolism of carbohydrates and amino acids.