Species range limits are expected to be dramatically altered under future climate change and many species are predicted to shift their distribution upslope to track their suitable conditions (i.e. ...based on their niche). However, there might be large discrepancies between the speed of the upward shift of the climatic niche and the actual migration velocity of the species, especially in long‐lived organisms such as trees. In fact, most studies did not find any significant upward shift of the distributional limits of temperate forest trees over the last decades. It therefore beckons the questions why trees are moving upslope much slower than their bioclimatic envelope and what are the implications for ecosystem functioning.
Here, we compared the simulations of the upslope displacement of the bioclimatic envelope of 16 tree species inhabiting temperate mountain forests under ongoing and future climate change obtained by correlative species distribution models (SDMs) to those from a dynamic forest model accounting for dispersal, competition and demography. We then partitioned the discrepancy in upslope migration velocity between the SDMs and the dynamic forest model into different components by manipulating dispersal limitation, interspecific competition and demography.
Tree species in the dynamic forest model migrated only slowly upslope in contrast to the SDMs. Most of the difference in migration velocity can directly be attributed to tree's demography (long life cycle), followed by effects of competition and only a marginal contribution of dispersal limitation. Additionally, lower elevation species (‘non‐treeline’) shifted slower upslope than high elevation species (‘treeline’) indicating a strong effect of interspecific competition at their leading edge.
Synthesis. Forests have a high inertia to climate change because of their longevity and ability to acclimatize to high climatic fluctuations. Lower elevation tree species (deciduous) only slowly establish in stands at higher elevation where coniferous species dominate and likely profit from facilitation by disturbance events. Therefore, forest ecosystems seem to persist, even if climate becomes unfavourable, until they approach a tipping point at which an extreme event (e.g. drought, storm or insect attack) leads to a large dieback and resource change enabling new suitable species to spread and establish.
Forests have a high inertia to climate change because of their longevity and ability to acclimatize to high climatic fluctuations. Lower elevation tree species (deciduous) only slowly establish in stands at higher elevation where coniferous species dominate and likely profit from facilitation by disturbance events. Here, comparing predictions from bioclimatic envelopes to those of dynamic forest models, we show that the upper elevational limits of trees in the Alps moves much slower than their climatic potential as a result of demographic processes and inter‐specific competition at their leading edge rather than due to dispersal limitations.
Over the coming decades, the predicted increase in frequency and intensity of extreme events such as droughts is likely to have a strong effect on forest functioning. Recent studies have shown that ...species mixing may buffer the temporal variability of productivity. However, most studies have focused on temporal stability of productivity, while species mixing may also affect forest resilience to extreme events. Our understanding of mechanisms underlying species mixing effects on forest stability and resilience remains limited because we ignore how changes from intraspecific to interspecific interactions in the neighbourhood of a given tree might affect its stability and resilience to extreme drought (i.e. response during and after this drought). This is crucial to better understand forests’ response to climate change and how diversity may help maintain forest functioning.
Here we analysed how local intra‐ or interspecific interactions may affect the temporal stability and resilience to drought of individual trees in French mountain forests, using basal area increment data over the previous 20 years for Fagus sylvatica, Abies alba and Quercus pubescens. We analysed the effect of interspecific competition on (a) the temporal stability and (b) the resilience to drought (resistance and recovery) of individual tree radial growth.
We found no significant interspecific competition effect on temporal stability, but species‐specific effects on tree growth resilience to drought. There was a positive effect of heterospecific proportion on the drought resilience of Q. pubescens, a negative effect for A. alba and no effect for F. sylvatica. These differences may be related to interspecific differences in water use or rooting depth.
Synthesis: In this study, we showed that stand composition influences individual tree growth resilience to drought, but this effect varied depending on the species and its physiological responses. Our study also highlighted that a lack of biodiversity effect on long‐term stability might hide important effects on short‐term resilience to extreme climatic events. This may have important implications in the face of climate change.
Foreign Language Resume
Au cours des prochaines décennies, l'augmentation de la fréquence et de l'intensité des événements extrêmes, tels que les sécheresses, aura probablement un fort effet déstabilisateur sur les écosystèmes forestiers. Récemment, des études ont montré que le mélange d'espèces pourrait tamponner l'effet du stress sur les processus forestiers. La grande majorité des études mettent l'accent sur l'effet du mélange sur la stabilité temporelle des écosystèmes, mais le mélange pourrait également affecter la résilience des forêts aux sécheresses. De plus, notre compréhension des mécanismes sous‐jacents reste encore limitée et peu d’études permettent de les démêler. Pourtant cette compréhension est crucial pour mieux appréhender la réaction des forêts au changement climatique et comment la diversité peut aider à maintenir leur fonctionnement.
Nous analysons ici comment les interactions intra ou interspécifiques locales affectent la stabilité temporelle et la résilience à la sécheresse des arbres individuels dans les forêts de montagne avec des séries d'accroissement en surface terrière (BAI) de hêtres (Fagus sylvatica L.), de sapins (Abies alba L.) et de chênes (Quercus pubescens L.). Nous avons analysé l'effet de la compétition interspécifique sur la stabilité temporelle individuelle et les deux dimensions de la résilience à la sécheresse: la résistance et la récupération.
Nous n'avons trouvé aucun effet significatif de compétition interspécifique sur la stabilité temporelle. Par contre nous avons pu constater un effet positif de la compétition hétérospecifique sur la résilience du chêne, négatif sur celle du sapin et pas d'effet pour le hêtre. Les différences entre les espèces pourraient être dues à leurs différences de stratégies hydriques.
Dans cette étude, nous avons montré que la composition du peuplement influe sur la résilience de la croissance des arbres face à la sécheresse, et que cet effet varie avec l'espèce. Nous avons également mis en lumière le fait que l'absence d'effet de la biodiversité sur la stabilité à long terme pourrait masquer des effets importants sur la résilience à court terme aux événements climatiques extrêmes. Cela pourrait avoir des implications importantes face au changement climatique.
Here, we showed that stand composition influences individual tree growth resilience to drought, but this effect varied depending on the species and its physiological responses. Our study also highlighted that a lack of biodiversity effect on long‐term stability might hide important effects on short‐term resilience to extreme climatic events. This may have important implications in the face of climate change.
•Unmanaged forests supply high levels of climate regulation and erosion regulation.•Best practice management slightly improved water regulation.•Climate change was a stronger driver of ecosystem ...services than management.•Control of management on ecosystem services decreased with severe climate change.•Site and land-use legacies modulated the effect of management on ecosystem services.
Forest ecosystems provide a wide variety of ecosystem services to society. In harsh mountain environments, the regulating services of forests are of particular importance. Managing mountain forests for regulating services is a cost- and labor intensive endeavor. Yet, also unmanaged forests regulate the environment. In the context of evidence-based decision making it is thus important to scrutinize if current management recommendations improve the supply of regulating ecosystem services over unmanaged development trajectories. A further issue complicating decision making in the context of regulating ecosystem services is their high sensitivity to climate change. Climate-mediated increases in natural disturbances, for instance, could strongly reduce the supply of regulating services from forests in the future. Given the profound environmental changes expected for the coming decades it remains unclear whether forest management will still be able to significantly control the future trajectories of mountain forest development, or whether the management effect will be superseded by a much stronger climate and disturbance effect. Here, our objectives were (i) to quantify the future regulating service supply from a 6456 ha landscape in the Stubai valley in Tyrol, Austria, and (ii) to assess the relative importance of management, climate, and natural disturbances on the future supply of regulating ecosystem services. We focused our analysis on climate regulation, water regulation, and erosion regulation, and used the landscape simulation model iLand to quantify their development under different climate scenarios and management strategies. Our results show that unmanaged forests are efficient in providing regulating ecosystem services. Both climate regulation and erosion regulation were higher in unmanaged systems compared to managed systems, while water regulation was slightly enhanced by management. Overall, direct effects of climate change had a stronger influence on the future supply of regulating services than management and natural disturbances. The ability of management to control ecosystem service supply decreased sharply with the severity of future climate change. This finding highlights that forest management could be severely stymied in the future if climate change continues to proceed at its current rate. An improved quantitative understanding of the drivers of future ecosystem service supply is needed to more effectively combine targeted management efforts and natural ecosystem dynamics towards sustaining the benefits society derives from forests in a rapidly changing world.
Soil fungi and bacteria are the key players in the transformation and processing of carbon and nutrients in terrestrial ecosystems, yet controls on their abundance and activity are not well ...understood. Based on stoichiometric principles, soil microbial processes are expected to be limited by mineral nutrients, which are particularly scarce in often highly weathered tropical forest soils. Such limitation is directly relevant for the fate of soil carbon and global element cycles, but its extent and nature have never been assessed systematically across the tropical biome. Here, we address the relative importance of nitrogen, phosphorus, and other nutrients in limiting soil microbial biomass and process rates in tropical forests. We conducted an in-depth literature review and a meta-analysis of the available nutrient addition experiments in tropical forests worldwide. Our synthesis showed predominant and general phosphorus limitation of a variety of microbial processes across tropical forests, and additional nitrogen limitation in tropical montane forests. The apparent widespread microbial phosphorus limitation needs to be accounted for in the understanding and prediction of biogeochemical cycles in tropical forests and their future functioning. Other mineral nutrients or carbon may modify the importance of phosphorus, but more experimental studies are urgently needed.
•Mapping current and future geographical distributions of European yew.•Distance from river, Geology, Slope, and bio18 are most important variables in yew SDMs.•European yew will shift to high ...elevation under future climate change.•Climate change would reduce the habitat range of European yew.
Prioritizing new areas for conservation in the Hyrcanian mountain forests is important because future climate change is an immediate threat to endangered species in these areas. Taxus baccata L. (European yew) is one of the most important coniferous species of the Hyrcanian forests that is endangered today for various reasons; therefore, the conservation and restoration of this valuable species is essential. The present study was conducted in order to identify areas with high potential for restoration and conservation of yew with consideration of future climate change. Maximum Entropy (MaxEnt) was used to model the current and future distribution of yew in Hyrcanian forests of northern Iran. VIKOR fuzzy model applied to prioritize conservation and restoration areas. The results showed that MaxEnt model has high efficiency in modeling the distribution of yew with area under curve (AUC) = 0.98 in the study area. Importance analysis of explanatory variables showed that distance from rivers, geology, slope, precipitation of warmest quarter (bio18), and annual precipitation (bio12) were more important than other variables in the potential distribution of yew. The results showed that at current condition, suitable areas for yew in the Hyrcanian forests of Iran are distributed along an elevation gradient from sea level to 2600 m, and under the future climate change (2050 and 2070) this species will shift to higher elevations and lose the lower elevation habitats. The findings of this study predict that the desired habitats of yew in Hyrcanian forests will be severely affected by climate change. Given these cases, it is necessary to make management and conservation decisions in relation to this species, taking into account the effects of climate change and adaptation in the Hyrcanian forests.
1. The successional dynamics of forests—from canopy openings to regeneration, maturation, and decay—influence the amount and heterogeneity of resources available for forest-dwelling organisms. ...Conservation has largely focused only on selected stages of forest succession (e.g., late-seral stages). However, to develop comprehensive conservation strategies and to understand the impact of forest management on biodiversity, a quantitative understanding of how different trophic groups vary over the course of succession is needed. 2. We classified mixed mountain forests in Central Europe into nine successional stages using airborne LiDAR. We analysed α- and β-diversity of six trophic groups encompassing approximately 3,000 species from three kingdoms. We quantified the effect of successional stage on the number of species with and without controlling for species abundances and tested whether the data fit the more-individuals hypothesis or the habitat heterogeneity hypothesis. Furthermore, we analysed the similarity of assemblages along successional development. 3. The abundance of producers, first-order consumers, and saprotrophic species showed a U-shaped response to forest succession. The number of species of producer and consumer groups generally followed this U-shaped pattern. In contrast to our expectation, the number of saprotrophic species did not change along succession. When we controlled for the effect of abundance, the number of producer and saproxylic beetle species increased linearly with forest succession, whereas the U-shaped response of the number of consumer species persisted. The analysis of assemblages indicated a large contribution of succession-mediated β-diversity to regional γ-diversity. 4. Synthesis and applications. Depending on the species group, our data supported both the more-individuals hypothesis and the habitat heterogeneity hypothesis. Our results highlight the strong influence of forest succession on biodiversity and underline the importance of controlling for successional dynamics when assessing successional stages with highest diversity (early and late successional stages) are currently strongly underrepresented in the forests of Central Europe. We thus recommend that conservation strategies aim at a more balanced representation of all successional stages.
Improving our understanding of the potential of forest adaptation is an urgent task in the light of predicted climate change. Long‐term alternatives for susceptible yet economically important tree ...species such as Norway spruce (Picea abies) are required, if the frequency and intensity of summer droughts will continue to increase. Although Silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) have both been described as drought‐tolerant species, our understanding of their growth responses to drought extremes is still limited. Here, we use a dendroecological approach to assess the resistance, resilience, and recovery of these important central Europe to conifer species the exceptional droughts in 1976 and 2003. A total of 270 trees per species were sampled in 18 managed mixed‐species stands along an altitudinal gradient (400–1200 m a.s.l.) at the western slopes of the southern and central Black Forest in southwest Germany. While radial growth in all species responded similarly to the 1976 drought, Norway spruce was least resistant and resilient to the 2003 summer drought. Silver fir showed the overall highest resistance to drought, similarly to Douglas fir, which exhibited the widest growth rings. Silver fir trees from lower elevations were more drought prone than trees at higher elevations. Douglas fir and Norway spruce, however, revealed lower drought resilience at higher altitudes. Although the 1976 and 2003 drought extremes were quite different, Douglas fir maintained consistently the highest radial growth. Although our study did not examine population‐level responses, it clearly indicates that Silver fir and Douglas fir are generally more resistant and resilient to previous drought extremes and are therefore suitable alternatives to Norway spruce; Silver fir more so at higher altitudes. Cultivating these species instead of Norway spruce will contribute to maintaining a high level of productivity across many Central European mountain forests under future climate change.
The two extreme droughts in 1976 and 2003 affected negatively the radial growth response of Norway spruce, Silver and Douglas fir in the Black forest at all elevations. The 1976 drought had a less pronounced effect than the 2003 summer drought; however, firs were noticeably more resistant and resilient to extreme drought than spruce. Spruce was the most affected species when comparing performances of drought indices, and Silver fir the least affected. Douglas fir showed consistently the highest growth rates.
•Effects of weather, fuels and topography on impeding fire spread were studied.•Weather and fuels were most important in the Northern Rockies study areas.•Fuels and topography were highly influential ...in the Southwestern study area.•Key variables were: temperature, previous burns, valley bottoms and ridgetops.
As wildland fire activity continues to surge across the western US, it is increasingly important that we understand and quantify the environmental drivers of fire and how they vary across ecosystems. At daily to annual timescales, weather, fuels, and topography are known to influence characteristics such as area burned and fire severity. An understudied facet, however, concerns how these factors inhibit fire spread and thereby contribute to the formation of fire boundaries. We evaluated how weather, fuels, and topography impeded fire spread in four large study areas in the western US, three in the Northern Rockies and one in the Southwest. Weather and fuels were the most important factors in the Northern Rockies, whereas fuels and topography were dominant in the Southwest. Within the categories of weather, fuels, and topography, we also evaluated which specific variables were most influential in impeding fire spread. We explicitly accounted for the presence and age of previous burns within the fuels category. We found that: (1) temperature was the most influential weather variable in the Northern Rockies; (2) previous burns (particularly those that were ⩽5years old) were moderately to highly influential in all study areas; and (3) valley bottoms and ridgetops were moderately to highly associated with fire boundaries in all study areas. Our results elucidate the regionally varying roles of weather, fuels, and topography in impeding fire spread, emphasizing each ecosystem’s unique biophysical setting and fire regime.
Context
Varying altitudes and aspects within small distances are typically found in mountainous areas. Such a complex topography complicates the accurate quantification of forest C dynamics at larger ...scales.
Objectives
We determined the effects of altitude and aspect on forest C cycling in a typical, mountainous catchment in the Northern Limestone Alps.
Methods
Forest C pools and fluxes were measured along two altitudinal gradients (650–900 m a.s.l.) at south-west (SW) and north-east (NE) facing slopes. Net ecosystem production (NEP) was estimated using a biometric approach combining field measurements of aboveground biomass and soil CO
2
efflux (SR) with allometric functions, root:shoot ratios and empirical SR modeling.
Results
NEP was higher at the SW facing slope (6.60 ± 3.01 t C ha
−1
year
−1
), when compared to the NE facing slope (4.36 ± 2.61 t C ha
−1
year
−1
). SR was higher at the SW facing slope too, balancing out any difference in NEP between aspects (NE: 1.30 ± 3.23 t C ha
−1
year
−1
, SW: 1.65 ± 3.34 t C ha
−1
year
−1
). Soil organic C stocks significantly decreased with altitude. Forest NPP and NEP did not show clear altitudinal trends within the catchment.
Conclusions
Under current climate conditions, altitude and aspect adversely affect C sequestering and releasing processes, resulting in a relatively uniform forest NEP in the catchment. Hence, including detailed climatic and soil conditions, which are driven by altitude and aspect, will unlikely improve forest NEP estimates at the scale of the studied catchment. In a future climate, however, shifts in temperature and precipitation may disproportionally affect forest C cycling at the southward slopes through increased water limitation.
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