Additional informationReprints and permissions information is available online at www.nature.com/reprints. Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Competing financial interestsThe authors declare no competing financial interests. Europe PMC Funders GroupAuthor Manuscript Nat Clim Chang. Author manuscript; available in PMC 2017 December 01. Forest disturbances are sensitive to climate. However, our understanding of disturbance dynamics in response to climatic changes remains incomplete, particularly regarding large-scale patterns, interaction effects and dampening feedbacks. Here we provide a global synthesis of climate change effects on important abiotic (fire, drought, wind, snow and ice) and biotic (insects and pathogens) disturbance agents. Warmer and drier conditions particularly facilitate fire, drought and insect disturbances, while warmer and wetter conditions increase disturbances from wind and pathogens. Widespread interactions between agents are likely to amplify disturbances, while indirect climate effects such as vegetation changes can dampen long-term disturbance sensitivities to climate. Future changes in disturbance are likely to be most pronounced in coniferous forests and the boreal biome. We conclude that both ecosystems and society should be prepared for an increasingly disturbed future of forests.Natural disturbances, such as fires, insect outbreaks and windthrows, are an integral part of ecosystem dynamics in forests around the globe. They occur as relatively discrete events, and form characteristic regimes of typical disturbance frequencies, sizes and severities over extended spatial and temporal scales1,2. Disturbances disrupt the structure, composition and function of an ecosystem, community or population, and change resource availability or the physical environment3. In doing so, they create heterogeneity on the landscape4, foster diversity across a wide range of guilds and species5,6 and initiate ecosystem renewal or reorganization7,8.Disturbance regimes have changed profoundly in many forest ecosystems in recent years, with climate being a prominent driver of disturbance change9. An increase in disturbance occurrence and severity has been documented over large parts of the globe, for example, for fire10,11, insect outbreaks12,13 and drought14,15. Such alterations of disturbance regimes have the potential to strongly impact the ability of forests to provide ecosystem services to society6. Moreover, a climate-mediated increase in disturbances could exceed the ecological resilience of forests, resulting in lastingly altered ecosystems or shifts to non-forest ecosystems as tipping points are crossed16-18. Consequently, disturbance change is expected to be among the most profound impacts that climate change will have on forest ecosystems in the coming decades19.The ongoing changes in disturbance regimes in combination with their strong and lasting impacts on ecosystems have led to an in...

Mixing of complementary tree species may increase stand productivity, mitigate the effects of drought and other risks, and pave the way to forest production systems which may be more resource-use efficient and stable in the face of climate change. However, systematic empirical studies on mixing effects are still missing for many commercially important and widespread species combinations. Here we studied the growth of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in mixed versus pure stands on 32 triplets located along a productivity gradient through Europe, reaching from Sweden to Bulgaria and from Spain to the Ukraine. Stand inventory and taking increment cores on the mainly 60-80 year-old trees and 0.02-1.55 ha sized, fully stocked plots provided insight how species mixing modifies the structure, dynamics and productivity compared with neighbouring pure stands. In mixture standing volume (?12 %), stand density (?20 %), basal area growth (?12 %), and stand volume growth (?8 %) were higher Communicated by Peter Biber. than the weighted mean of the neighbouring pure stands. Scots pine and European beech contributed rather equally to the overyielding and overdensity. In mixed stands mean diameter (?20 %) and height (?6 %) of Scots pine was ahead, while both diameter and height growth of European beech were behind (-8 %). The overyielding and overdensity were independent of the site index, the stand growth and yield, and climatic variables despite the wide variation in precipitation (520-1175 mm year -1 ), mean annual temperature (6-10.5°C), and the drought index by de Martonne (28-61 mm°C -1 ) on the sites. Therefore, this species combination is potentially useful for increasing productivity across a wide range of site and climatic conditions. Given the significant overyielding of stand basal area growth but the absence of any relationship with site index and climatic variables, we hypothesize that the overyielding and overdensity results from several different types of interactions (light-, water-, and nutrient-related) that are all important in different circumstances. We discuss the relevance of the results for ecological theory and for the ongoing silvicultural transition from pure to mixed stands and their adaptation to climate change. Electronic supplementary material

611. There is increasing evidence that species diversity enhances the temporal stability of 62 community productivity in different ecosystems, although its effect at population and tree 63 levels seems to be negative or neutral. Asynchrony between species was found to be one of 64 the main drivers of this stabilizing process. However, scarce research in this area has been 65 undertaken in forest communities, so determining the effect of species mixing on the stability 66 of forest productivity as well as the identity of the main drivers involved still poses a 67 challenging task. 3. Mixed stands showed a higher temporal stability of basal area growth than monospecific 76 stands at community level, but not at population or individual tree levels. Asynchrony 77 between species growth in mixtures was related to temporal stability, but neither overyielding 78 nor asynchrony between species growth in monospecific stands were linked to temporal 79 stability. Therefore, species interactions modify between-species asynchrony in mixed stands. 80Accordingly, temporal shifts in species interactions were related to asynchrony and to the 81 mixing effect on temporal stability. 4. Synthesis. Our findings confirm that species mixing can stabilize productivity at 83 community level whereas there is a neutral or negative effect on stability at population and 84 individual tree level. The contrasting findings as regards the relationships between temporal 85 stability and species asynchrony in mixed and monospecific stands suggest that the main 86 driver in the stabilizing process is the temporal niche complementarity between species rather 87 than differences in species specific responses to environmental conditions. 89 Keywords 91Temporal variability; mixed-species forests; plant-plant interactions; overyielding; 92 asynchrony; niche complementarity; organizational levels; 93 94

a b s t r a c tThe mixing of tree species with complementary ecological traits may modify forest functioning regarding productivity, stability, or resilience against disturbances. This may be achieved by a higher heterogeneity in stand structure which is often addressed but rarely quantified. Here, we use 32 triplets of mature and fully stocked monocultures and mixed stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) located along a productivity and water availability gradient through Europe to examine how mixing modifies the stand structure in terms of stand density, horizontal tree distribution pattern, vertical stand structure, size distribution pattern, and variation in tree morphology. We further analyze how site conditions modify these aspects of stand structure. For this typical mixture of a light demanding and shade tolerant species we show that (i) mixing significantly increases many aspects of structural heterogeneity compared with monocultures, (ii) mixing effects such as an increase of stand density and diversification of vertical structure and tree morphology are caused by species identity (additive effects) but also by species interactions (multiplicative effects), and (iii) superior heterogeneity of mixed stands over monocultures can increase from dry to moist sites. We discuss the implications for analyzing the productivity, for modelling and for the management of mixed species stands.

We analysed climate change impacts on the growth and natural mortality of forest tree species and forest carbon (C) balance along an elevation gradient extending from the Pannonian lowland to the West Carpathian Mountains (Central Europe). Norway spruce Picea abies, European beech Fagus sylvatica, and oak Quercus sp. were investigated for 2 future time periods: 2021-2050 and 2071-2100. The period 1961-1990 was used as reference. Forest growth simulations were based on the SIBYLA tree growth simulator (an empirical model), and C cycle-related simulations were performed using BIOME-BGC (a process-based biogeochemical model). Growth simulations indicated that climate change will substantially affect the growth of spruce and beech, but not of oak, in Central Europe. Growth of spruce and beech in their upper distribution ranges was projected to improve, while drought-induced production decline was projected at the species' receding edges. Beech was the only species projected to decline critically at lower elevations. C cycle simulations performed for the zone of ecological optima of the 3 tree species indicated that these forests are likely to remain net carbon dioxide sinks in the future, although the magnitude of their sequestration capacity will differ. Increasing nitrogen deposition and atmospheric carbon dioxide concentration were projected to greatly affect the forest C cycle. A multi-model assessment based on SIBYLA and BIOME-BGC simulations performed for the zone of ecological optima suggested that oak production will either remain the same as in the reference period or will increase. Future production of beech seems uncertain and might decline, while spruce production is likely to increase. The results also confirmed the value of multi-model approaches for assessing future forest development under climate change.KEY WORDS: Norway spruce · European beech · Oak · Forest carbon cycle · Tree production · Tree mortality · BIOME-BGC model · SIBYLA tree growth simulator Resale or republication not permitted without written consent of the publisher