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With progressing climate change, increasing weather extremes will endanger tree regeneration. Canopy openings provide light for tree establishment, but also reduce the microclimatic buffering effect of forests. Thus, disturbances can have both positive and negative impacts on tree regeneration. In 2015, three years before an extreme drought episode hit Central Europe, we established a manipulation experiment with a factorial block design in European beech (Fagus sylvatica L.)-dominated forests. At five sites located in southeastern Germany, we conducted three censuses of tree regeneration after implementing two different canopy disturbances (aggregated and distributed canopy openings), and four deadwood treatments (retaining downed, standing, downed + standing deadwood and removing all deadwood), as well as in one untreated control plot. In addition, we measured understory light levels and recorded local air temperature and humidity over five years. We (i) tested the effects of experimental disturbance and deadwood treatments on regeneration and (ii) identified the drivers of regeneration density as well as seedling species and structural diversity. Regeneration density increased over time. Aggregated canopy openings supported species and structural diversity, but reduced regeneration density. Tree regeneration was positively associated with understory light levels, while maximum vapor pressure deficit influenced tree regeneration negatively. Deadwood and browsing impacts on regeneration varied and were inconclusive. Our study indicates that despite the drought episode regeneration in beech-dominated forests persisted under moderately disturbed canopies. However, the positive effect of increased light availability on tree regeneration might have been offset by harsher microclimate after canopies have been disturbed. [ABSTRACT FROM AUTHOR]

Key message: Authors have analyzed the possible correlation between measurements/indicators of forest structure and species richness of many taxonomic or functional groups over three regions of Germany. Results show the potential to use structural attributes as a surrogate for species richness of most of the analyzed taxonomic and functional groups. This information can be transferred to large-scale forest inventories to support biodiversity monitoring. Context: We are currently facing a dramatic loss in biodiversity worldwide and this initiated many monitoring programs aiming at documenting further trends. However, monitoring species diversity directly is very resource demanding, in particular in highly diverse forest ecosystems. Aims: We investigated whether variables applied in an index of stand structural diversity, which was developed based on forest attributes assessed in the German National Forest Inventory, can be calibrated against richness of forest-dwelling species within a wide range of taxonomic and functional groups. Methods: We used information on forest structure and species richness that has been comprehensively assessed on 150 forest plots of the German biodiversity exploratories project, comprising a large range of management intensities in three regions. We tested, whether the forest structure index calculated for these forest plots well correlate with the number of species across 29 taxonomic and functional groups, assuming that the structural attributes applied in the index represent their habitat requirements. Results: The strength of correlations between the structural variables applied in the index and number of species within taxonomic or functional groups was highly variable. For some groups such as Aves, Formicidae or vascular plants, structural variables had a high explanatory power for species richness across forest types. Species richness in other taxonomic and functional groups (e.g., soil and root-associated fungi) was not explained by individual structural attributes of the index. Results indicate that some taxonomic and functional groups depend on a high structural diversity, whereas others seem to be insensitive to it or even prefer structurally poor stands. Conclusion: Therefore, combinations of forest stands with different degrees of structural diversity most likely optimize taxonomic diversity at the landscape level. Our results can support biodiversity monitoring through quantification of forest structure in large-scale forest inventories. Changes in structural variables over inventory periods can indicate changes in habitat quality for individual taxonomic groups and thus points towards national forest inventories being an effective tool to detect unintended effects of changes in forest management on biodiversity. [ABSTRACT FROM AUTHOR]

Background: Forests perform various important ecosystem functions that contribute to ecosystem services. In many parts of the world, forest management has shifted from a focus on timber production to multi-purpose forestry, combining timber production with the supply of other forest ecosystem services. However, it is unclear which forest types provide which ecosystem services and to what extent forests primarily managed for timber already supply multiple ecosystem services. Based on a comprehensive dataset collected across 150 forest plots in three regions differing in management intensity and species composition, we develop models to predict the potential supply of 13 ecosystem services. We use those models to assess the level of multifunctionality of managed forests at the national level using national forest inventory data. Results: Looking at the potential supply of ecosystem services, we found trade-offs (e.g. between both bark beetle control or dung decomposition and both productivity or soil carbon stocks) as well as synergies (e.g. for temperature regulation, carbon storage and culturally interesting plants) across the 53 most dominant forest types in Germany. No single forest type provided all ecosystem services equally. Some ecosystem services showed comparable levels across forest types (e.g. decomposition or richness of saprotrophs), while others varied strongly, depending on forest structural attributes (e.g. phosphorous availability or cover of edible plants) or tree species composition (e.g. potential nitrification activity). Variability in potential supply of ecosystem services was only to a lesser extent driven by environmental conditions. However, the geographic variation in ecosystem function supply across Germany was closely linked with the distribution of main tree species. Conclusions: Our results show that forest multifunctionality is limited to subsets of ecosystem services. The importance of tree species composition highlights that a lack of multifunctionality at the stand level can be compensated by managing forests at the landscape level, when stands of complementary forest types are combined. These results imply that multi-purpose forestry should be based on a variety of forest types requiring coordinated planning across larger spatial scales. [ABSTRACT FROM AUTHOR]

Future increases in temperature and changes in precipitation patterns may negatively affect the growth performance of economically important tree species such as Norway spruce, which in the past have often been established and managed in monocultures. Structural diversity has been advocated as a silvicultural approach to increase resistance and resilience of forests to climate change extremes. Whether it promotes growth stability during and following drought years has not yet been analyzed. We investigated stem growth reactions to the extreme drought of 2003 in 23 uneven-structured, mixed Norway spruce and Silver fir stands in southwestern Germany. Using linear mixed-effects models we analyzed the resistance and resilience of basal area increment in relation to species identity, drought intensity, tree size, competition, density and diversity. Structural diversity, measured as variation in tree diameter at breast height, had no influence on increment stability during the extreme summer drought of 2003. Likewise, the effect of species diversity was weak and inconclusive. However, a higher presence of Silver fir in the mixture appeared to reduce increment stability in 2003 for both fir and spruce. Reducing competition through thinning counteracted this effect and promoted increment stability. Our findings indicate that the species identity of competitors in mixtures is a better predictor of stem growth reactions to drought than diversity. They support the conclusion that diversity does not generally increase stability to drought stress. Silver fir consistently showed a substantially higher increment resistance and resilience than spruce. Its resistance increased with diminishing drought intensity, yet spruce reacted uniformly, manifesting a low resistance across the whole drought intensity gradient. Spruce did not regain pre-drought growth levels within the first three years after drought, whereas fir did. We conclude that fir may be able to act as a silvicultural alternative to spruce under changing climatic conditions, given appropriate sites and thinning regimes. Considering the expected increase in drought intensity and frequency in the 21 st century, understanding species interactions at the local scale emerges as an essential prerequisite for developing resilient forest stands. [ABSTRACT FROM AUTHOR]

• Share of maize area increase is driven by biogas plant capacity. • Field edge density decrease is associated with biogas production. • Field data and Landsat images, provide a means to study the effects of biogas production on agricultural land. With the subsidization of energy crops in Germany by the Renewable Energy Act, the production of biogas became increasingly dependent on agricultural land for biomass generation. The effects of increasing biogas plants' capacities on the increase of maize and other energy crops area over the years have raised sustainability concerns in the German society. A periodic assessment of the impacts of biomass production is necessary to determine efficient and environmentally sustainable recommendations for future planning processes. Previous studies have neglected the effects of biogas plant capacity, which is directly linked with the amount of biomass required and, thus, is supposed to be a driver for the impacts of biogas production on agricultural lands. Combining the Integrated Administration and Control System (IACS) and Landsat satellite data provides a means to study present and past agricultural landscape. The aim of the study was to map the agricultural lands of Northern Hesse from 2000 to 2015, evaluate the change in maize area and structural diversity (i.e. field edge density) of agricultural fields, and assess if biogas production is a major driver of possible changes. Northern Hesse was consciously chosen, as it represents a typical European low-mountain range region with substantial geographical and agricultural variability. Our results show that from 2000 to 2015 on average, the shares of grassland and summer crops areas decreased by 5.7 percentage points (p.p.) and 5.8 p.p., respectively, while the shares of winter crops and maize areas increased by 9.2 p.p. and 2.2 p.p., respectively. Potential drivers of the change in maize area and structural diversity of agricultural fields, such as the mean capacity of biogas plants (kW), and topographical attributes, such as mean elevation (m) and slope (%) were employed as explanatory variables on a municipality level in multiple linear regression models. The mean biogas capacity and elevation were the most significant drivers of change in maize area (p < 0.05), while biogas capacity and slope were the significant drivers of the change in structural diversity. Maize area increased with an increasing capacity of biogas plants at lower elevations of the study area (p < 0.05). A decrease in the structure of fields, which is an indicator for species and habitat diversity, was observed and this was very much associated with the extent of maize and winter crop production. However, the drivers of the changes in the maize area and structure of fields were of low dimensions with model R2 of 0.21 and 0.35 respectively. Overall, our study demonstrates the potential of spatial data from different origins in mapping land-cover over longer time periods for monitoring bio-economy effects on agricultural landscape. [ABSTRACT FROM AUTHOR]