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The article presents the discussion on Environmental Awareness in Mythology. Topics include whole environment and ecology consisting of earth, air, water, plants, and animals providing the necessary and sufficient conditions for sustaining human life; and natural imbalance caused by cutting trees and hunting wildlife for enjoyment and for luxurious skin coats having long term serious effects.

Understanding how evolutionary constraints shape the elevational distributions of tree lineages provides valuable insight into the future of tropical montane forests under global change. With narrow elevational ranges, high taxonomic turnover, frequent habitat specialization, and exceptional levels of endemism, tropical montane forests and trees are predicted to be highly sensitive to environmental change. Using plot census data from a gradient traversing > 3,000 m in elevation on the Amazonian flank of the Peruvian Andes, we employ phylogenetic approaches to assess the influence of evolutionary heritage on distribution trends of trees at the genus‐level. We find that closely related lineages tend to occur at similar mean elevations, with sister genera pairs occurring a mean 254 m in elevation closer to each other than the mean elevational difference between non‐sister genera pairs. We also demonstrate phylogenetic clustering both above and below 1,750 m a.s.l, corresponding roughly to the cloud‐base ecotone. Belying these general trends, some lineages occur across many different elevations. However, these highly plastic lineages are not phylogenetically clustered. Overall, our findings suggest that tropical montane forests are home to unique tree lineage diversity, constrained by their evolutionary heritage and vulnerable to substantial losses under environmental changes, such as rising temperatures or an upward shift of the cloud‐base. [ABSTRACT FROM AUTHOR]

Uncovering the genetic basis of local adaptation is a major goal of evolutionary biology and conservation science alike. In an era of climate change, an understanding of how environmental factors shape adaptive diversity is crucial to predicting species response and directing management. Here, we investigate patterns of genomic variation in giant sequoia, an iconic and ecologically important tree species, using 1,364 bi‐allelic single nucleotide polymorphisms (SNPs). We use an FST outlier test and two genotype–environment association methods, latent factor mixed models (LFMMs) and redundancy analysis (RDA), to detect complex signatures of local adaptation. Results indicate 79 genomic regions of potential adaptive importance, with limited overlap between the detection methods. Of the 58 loci detected by LFMM, 51 showed strong correlations to a precipitation‐driven composite variable and seven to a temperature‐related variable. RDA revealed 24 outlier loci with association to climate variables, all of which showed strongest relationship to summer precipitation. Nine candidate loci were indicated by two methods. After correcting for geographic distance, RDA models using climate predictors accounted for 49% of the explained variance and showed significant correlations between SNPs and climatic factors. Here, we present evidence of local adaptation in giant sequoia along gradients of precipitation and provide a first step toward identifying genomic regions of adaptive significance. The results of this study will provide information to guide management strategies that seek to maximize adaptive potential in the face of climate change. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata (Lamb) Hook.) in the Dagangshan region of Jiangxi Province in southern China was selected to explore the impact of climatic factors on tree ring width growth. Results showed that the signal-to-noise ratio (SNR) and mean sensitivity (MS) were large while the first order autocorrelation coefficient (FOAC) was small, and the chronology contains abundant climatic information. The tree ring width index of Chinese fir was significantly positively correlated with the precipitation in December of the previous year and June of the current year, and significantly negatively correlated with that in the current May and August. The tree ring width index was significantly positively correlated with the temperature in April and May of the current year, but significantly negatively correlated with that in July of the current year. The tree ring width index had a good change consistency with the warmth index (Wi ) and humidity index (Hi ). The response function of Chinese fir ring width analysis shows that the warmth index is the main factor affecting tree ring growth, followed by the humidity index, mean annual precipitation, and mean annual temperature. The comprehensive effect of temperature and precipitation factors have significant influence on the tree ring width growth of Chinese fr. Results can provide a scientific basis for studying the effect of climatic factors on tree growth in sub-tropical regions in China and many other parts of the world. [ABSTRACT FROM AUTHOR]

Aim: To determine the global position of tree line isotherms, compare it with observed local tree limits on islands and mainlands, and disentangle the potential drivers of a difference between tree line and local tree limit. Location: Global. Time period: 1979–2013. Major taxa studied: Trees. Methods: We modelled the potential climatic tree line based on monthly temperatures and precipitation for the period 1979–2013. We then compared the potential tree line based on climate to observed tree limits at 26 oceanic islands, 55 continental islands and 382 mainland locations. The differences between potential tree line and observed tree limits was then analysed by regression with the islands' maximum elevation, age, isolation, and area. Additionally, we estimated growing season temperature niches for 16,041 species known to occur in the vicinity of the studied tree lines, and compared them across mainlands, and islands of continental and oceanic origin. Results: Observed local tree limits differ up to 2,066 m from the potential tree line at the mainland on oceanic islands. Climatic effects are responsible for a difference of up to 1,296 m between tree lines of mainland regions and oceanic islands (but only for 756 m for continental islands). On oceanic islands, a remaining difference of up to 829 m correlates with the isolation and the maximum elevation of an island. Floras of oceanic islands are however depauperate with respect to potential tree line species and species show an affinity to higher growing season temperatures. Main conclusions: Climate can explain about half of the differences between observed local tree limits and potential tree lines between the mainland and continental and oceanic islands. The remaining difference can be attributed to the higher isolation of oceanic islands, especially in the tropics, and as a consequence, a more depauperate flora and a lack of tree species that are able to grow at the tree line. [ABSTRACT FROM AUTHOR]

Global climate is rapidly changing, and the ability for tree species to adapt is dependent on standing genomic variation; however, the distribution and abundance of functional and adaptive variants are poorly understood in natural systems. We test key hypotheses regarding the genetics of adaptive variation in a foundation tree: genomic variation is associated with climate, and genomic variation is more likely to be associated with temperature than precipitation or aridity. To test these hypotheses, we used 9,593 independent, genomic single‐nucleotide polymorphisms (SNPs) from 270 individuals sampled from Corymbia calophylla's entire distribution in south‐western Western Australia, spanning orthogonal temperature and precipitation gradients. Environmental association analyses returned 537 unique SNPs putatively adaptive to climate. We identified SNPs associated with climatic variation (i.e., temperature [458], precipitation [75] and aridity [78]) across the landscape. Of these, 78 SNPs were nonsynonymous (NS), while 26 SNPs were found within gene regulatory regions. The NS and regulatory candidate SNPs associated with temperature explained more deviance (27.35%) than precipitation (5.93%) and aridity (4.77%), suggesting that temperature provides stronger adaptive signals than precipitation. Genes associated with adaptive variants include functions important in stress responses to temperature and precipitation. Patterns of allelic turnover of NS and regulatory SNPs show small patterns of change through climate space with the exception of an aldehyde dehydrogenase gene variant with 80% allelic turnover with temperature. Together, these findings provide evidence for the presence of adaptive variation to climate in a foundation species and provide critical information to guide adaptive management practices. [ABSTRACT FROM AUTHOR]

The numerous temperature and precipitation reconstructions in China based on tree-ring-width data have played significant roles in furthering the understanding of past climate changes. However, the geographical variability in the responses of trees to climate variations in China remains largely undetermined. Here, we describe an important spatial boundary in the response of trees to climate variations, namely the 600-mm annual precipitation isoline. We found that, to the north of this line, tree-ring widths are usually positively correlated with precipitation and negatively correlated with growing-season temperature. To the south of this line, the tree-ring widths respond positively to temperature, and winter half-year temperatures are the main reconstructed parameters, especially on the third topographical step of China. We also found that precipitation reconstructions based on tree-ring data and the Palmer Drought Severity Index almost exclusively fall in the region of the 200- to 600-mm annual precipitation isolines, not other regions. Our findings indicate that, when using multiple tree-ring-width chronologies for large-scale past climate reconstructions, the climatic signal of each tree-ring-width series should be carefully considered. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Climate influences species growth differently across altitudinal gradients. • Mixed-effects models can accurately predict tree growth. • Suitability maps are useful to design forest management actions. • Tree species could potentially extend their range. Abstract In the past few decades, temperate forests have been negatively altered by numerous anthropogenic activities and by the impact of ongoing climate change. These changes may require management actions to help preserve some forest tree species. In this sense, highly-detailed knowledge of tree growth and survival across territorial and climatic gradients will be important for forest conservation. We developed a novel approach to determine the optimal zones of forest growth and expansion through climate suitability maps, using a dense tree-ring network of four forest species in Moncayo Natural Park and high-resolution climate data. Our results showed that the mixed-effects models developed using climate data and tree size were able to predict between 65 and 80% of growth variability along the climatic gradient. All studied species were influenced by climate, and the relationship between growth and climate significantly differed along the prevailing climate gradient. Moreover, the suitability maps showed that the current species distribution is limited, and their application may serve as a tool for adaptive management in forests subjected to climate change. [ABSTRACT FROM AUTHOR]

Knowledge of tree-growth response to extreme climatic events, such as drought, is useful for forest managers to model the effects of future disturbances, and to develop management plans that mitigate the detrimental impacts. We analyzed the effects of an exceptional drought on Pinus palustris (Longleaf Pine) radial growth in the Alabama Fall Line Hills, based on site conditions and tree age. Results indicated that radial-growth response to drought was not influenced by site condition as we initially hypothesized, but was influenced by tree age. Management for resiliency to disturbance in Longleaf Pine ecosystems should consider the complexity of individual tree-growth response as a function of age and growing conditions. [ABSTRACT FROM AUTHOR]

Temperate fruit trees account for almost half of the worldwide fruit production, with Spain one of the largest world producers. Growing trees are quite vulnerable to cold temperatures. To minimise the effect of these cold temperatures, they stop their growth over the coldest months of the year, a state called dormancy. In particular, endodormancy, i.e. a dormancy related to the plant's inner physiological factors, requires accumulating cool temperatures to finish dormancy ("be broken"). The accumulation of cool temperatures according to specific rules is called chilling accumulation, and the chilling accumulation required to break dormancy is different for each tree crop and variety. There are several methods to calculate the chilling accumulation, all of them based on temperature only. Under global warming, it is expected that the fulfilment of the chilling requirements to break dormancy in temperate fruit trees could be compromised. In this study, the impact of climate change on the chilling accumulation over Peninsular Spain and the Balearic Islands was assessed. For this, bias-adjusted results of 10 Regional Climate Models (RCMs) under Representative Concentration Pathways (RCPs) RCP4.5 and RCP8.5 were used as inputs of four different methods for calculating chilling accumulation, and the results were compared for the near and far future under both RCPs. These results project a generalised reduction in chilling accumulation regardless of the RCP, future period or chilling calculation method used, with higher reductions for the far future and the RCP8.5 scenario. The projected winter chill decrease may threaten the viability of some tree crops and varieties in some areas, but also shows scope for varieties with lower chilling requirements. The results are relevant for planning future tree plantations under climate change, supporting adaptation of spatial distribution of tree crops and varieties in Spain. [ABSTRACT FROM AUTHOR]

"Warming hiatus" occurred in the Altay-Sayan Mountain Region, Siberia in c. 1997-2014. We analyzed evergreen conifer (EGC) stands area (satellite data) and trees (Siberian pine, Pinus sibirica Du Tour, Siberian fir, Abies sibirica Ledeb.) growth increment (dendrochronology data) response to climate variables before and during the hiatus. During the hiatus, EGC area increased in the highlands (>1000 m) (+30%), whereas at low and middle elevations (<1000 m. a.s.l.) the EGC area decreased (-7%). The EGC area increase was observed on the rain-ward northwest slopes mainly. In highlands, EGC area increase mainly correlated with summer air temperature, whereas at low and middle elevations EGC area decrease correlated with drought index SPEI and vapor pressure deficit (VPD). EGC mortality (fir and Siberian pine) in lowland was caused by the synergy of water stress (inciting factor) and barkbeetle attacks (contributing factor). Tree growth increment (GI) dynamics differs with respect to elevation. At high elevation (1700 m) GI permanently increased since warming onset, whereas at the middle (900 m) and low elevations (450 m) GI increased until c. 1983 yr. with followed depression. That GI "breakpoint" occurred about a decade before hiatus onset. In spite of growth depression, during hiatus GI was higher than that in pre-warming period. At high elevation, GI positively responded to elevated June temperatures and negatively to moisture increase (precipitation, root zone moisture content, VPD, and SPEI). At low elevation GI negatively responded to June temperatures and positively to moisture increase. For both, low and high elevation, these patterns persisted throughout the study period (1967-2014). On the contrary, at middle elevations GI dependence on climate variables switch after breakpoint year (1983). Before breakpoint, June air temperature (positive correlation) and moisture (negative correlations) controlled GI. Further temperature increase leads GI depression and switched correlation signs to opposite (from positive to negative with temperature, and from negative to positive with moisture variables). [ABSTRACT FROM AUTHOR]

Highlights • Use of outdoor microclimate maps to compare different design options at urban scale. • Tool to evaluate impact on urban comfort of the place/city garden design. • Decision-making tool to improve urban climate design considering outdoor comfort. Abstract The study is aimed at evaluating the potential effects of alternative design solutions with different green elements on outdoor microclimate with relation to a real case study application. The study has been commissioned in the framework of the follow up of a design competition, launched by the Municipality of Cesena to reshape a square in the historic city center, when a public debate raised around the arrangement of trees and green surfaces envisaged by the architectural layout. Different options were considered and the design team and the public authorities sought for evidences on the deriving benefits in the respective configurations in order to properly drive the process. Thus the scientific research approach was applied to investigate the potential impacts according to a microclimate oriented perspective. The outcomes showed that green surfaces significantly improved the outdoor comfort conditions compared to original paved ones and that a minor contribution derived by the trees arrangement. The paper reports the applied methodology according to the specific context, the interpretation of results and how they have been translated into user friendly visualizations in order to make them understandable to a broader and non technical audience. [ABSTRACT FROM AUTHOR]

The article considers the Voronezh region climate dynamics over a 30-year period in comparison with the previous climate normal. Mathematical analysis of the relationships of cyclic changes in radial increment of native tree species of the south of the Russian Plain - Scots pine (Pinus sylvestris Linnaeus) and English oak (Quercus robur Linnaeus) - with climate factors (air temperature, amount of precipitation) is done. The greatest importance of April and, especially, May sums of precipitation for the formation of radial increment of native species (P. sylvestris and Q. robur) was confirmed. The forecast of changes in stand growth and productivity of the studied species is presented. [ABSTRACT FROM AUTHOR]

This paper assesses the effects of trees ( Platanus x hispanica ) of different leaf area density on ventilation, NO x and PM 2.5 concentrations across heights in Marylebone Rd street canyon in London (UK). Computational Fluid Dynamics steady state simulations are performed with OpenFOAM. The ventilation is evaluated through flow patterns and the analysis of the impact of trees on wind speed, turbulence kinetic energy, flow rates, mean and turbulent pollutant exchanges. Results show that the effects of trees are local. For parallel winds planting new trees is positive since flow channelling and turbulence distribute the pollutant over the height which is removed by both mean flow and turbulent fluctuations through the roof. Both areas close and far from the trees within the road have a beneficial effect, with pedestrian average concentration reductions up to 18% due to aerodynamic effects. For perpendicular winds recirculation zones diminish the dispersion of pollutants and the introduction of trees has an additional negative effect with local average concentration increase up to 108% close to trees. Overall, the positive deposition effects are larger for increased LAD and for perpendicular winds may counterbalance the negative aerodynamic effects at locations close to trees. [ABSTRACT FROM AUTHOR]

Southern African savannas are commonly polarised into two broad types based on plant functional types and defences; infertile savannas dominated by broad-leaved trees typically defended by nitrogen-free secondary compounds and fertile savannas dominated by fine-leaved trees defended by structural defences. In this study, we use trait and other data from 15 wooded savanna sites in Southern Africa and ask if broad-leaved and fine-leaved species dominate on nutrient-poor and nutrient-rich soils, respectively. We then test if there is there any evidence for trade-offs in chemical (i.e., condensed tannins and total polyphenols) vs. structural defences on different soil types. We did not find strong evidence for a general divide in fine- vs. broad-leaved savannas according to soil fertility, nor for a simple trade-off between chemical and structural defences. Instead, we found savanna species to cluster into three broad defence strategies: species were high in leaf N and either (A) highly defended by spines and chemicals or (B) only structurally defended, or (C) low in leaf N and chemically defended. Finally, we tested for differences in browser utilisation between soil types and among plant defence strategies and found that browsing by meso-herbivores was higher on nutrient-rich soils and targeted species from groups A and B and avoided C, while browsing by elephants was mostly not affected by soil type or defence strategy. We propose a framework that can be used as a basis for asking strategic questions that will help improve our understanding of plant defences in savannas. [ABSTRACT FROM AUTHOR]

Storms cause major forest disturbances in Europe. The aim of this study was to model tree-level storm damage probability based on the properties of a tree and its environment and to examine whether fine-scale topographic information is connected to the damage probability. We used data documenting effects of two autumn storms on over 17 000 trees on permanent Finnish National Forest Inventory plots. The first storm was associated with wet snowfall that damaged trees, while exceptionally strong winds and gusts characterized the second storm. During the storms, soils were unfrozen and deciduous trees were without leaves. Generalized linear mixed models were used to study how topographical variables calculated from digital elevation models (DEM) with resolutions of 2 and 10 m (TOPO2 and TOPO10, respectively) were related to damage probability, in addition to variable groups for tree (TREE) and stand (STAND) characteristics. We compared models containing different variable groups with Akaike information criteria. The best model contained the variable groups TREE, STAND, and TOPO2. Increase in slope steepness calculated from the high-resolution DEM decreased tree-level damage probability significantly in the model. This suggests that the local topography affects the tree-level damage probability and that high-resolution topographical data improves the tree-level damage probability models. [ABSTRACT FROM AUTHOR]

Radial tree stem growth of Norway spruce ( Picea abies (L.) H. Karst.), European beech ( Fagus sylvatica L.), Scots pine ( Pinus sylvestris L.), and stone pine ( Pinus cembra L.) was monitored from 2012 to 2015 across sites in Austria with high-resolution dendrometers. Seasonal cumulative diameter increment was modeled using a hierarchical nonlinear mixed-effects model framework based on a logistic growth curve. In the dry and warm year 2015, the average annual diameter increment of 0.30 cm decreased by 50% on lower elevation sites and by 10% on higher elevation sites. In the cool and moist year 2014, Norway spruce achieved a higher annual diameter increment than European beech, whereas the opposite occurred in the dry and warm years 2013 and 2015. In the mixed beech-spruce stand, beech's consumptive water-use strategy has obviously caused intensified stress for spruce in these drought periods. On higher elevation sites, Norway spruce reacted more sensitively to climate fluctuation compared with stone pine, but overall reactions were only weak. Productivity varied strongly depending on the social status of the tree, with dominant and intermediate trees suffering more from drought. As warming and drought lowers increment rates on lower elevation sites and as trees on higher elevation sites react less flexibly, productivity losses are expected for Austrian forests due to climate warming. [ABSTRACT FROM AUTHOR]

Climate refugia are locations where decoupled climate processes enable species to persist despite unfavorable climate changes in surrounding landscapes. Despite theoretic bases and paleo-ecological evidence, refugia have not been widely characterized under modern conditions in mountain regions. Conifers in the Great Basin, USA, provide an opportunity to evaluate the potential of low-elevation ravine and riparian (LERR) contexts to function as climate refugia. We provide evidence for significantly higher than expected occurrence of limber pine ( Pinus flexilis E. James) in LERR contexts (mean 64%) across 43 mountain ranges. We document with observed and modeled data that LERR contexts are cooler and wetter than expected for their elevations, have low solar radiation, and produce larger (more positive) lapse rates relative to upland slopes. Together these findings suggest that LERR contexts generate decoupled microclimates that provide climate refugia for limber pine. In that refugia management has been promoted as a contemporary climate adaptation strategy, our findings suggest that LERR contexts be further evaluated for their conservation potential. [ABSTRACT FROM AUTHOR]

The predicted climate change will affect the growth and secondary chemistry of plants, but most studies only include leaves and leave out the effects on the secondary chemistry of other plant parts. In a field experiment, we studied the stem phenolic chemistry, as well as the growth of male and female genotypes, of aspen ( Populus tremula L.) after three years under single (T, UVA, UVB) and combined (UVA + T, UVB + T) treatments at elevated temperature (T, +2 °C) and ultraviolet-B radiation (+30% UVB). In addition, bud mass and photosynthesis, as well as leaf rust attack and leaf herbivory, were measured. We found that elevated temperature markedly reduced concentrations of salicylates, which were the most abundant compounds among the low relative molecular mass phenolics in the stem. Elevated temperature also increased the biomass, height, and diameter of both males and females, as well as leaf area and herbivory damage in leaves. In combination with UVB, elevated temperature decreased the height of both males and females. Moreover, male buds were bigger than female buds, and females had higher chlorophyll content than males. To conclude, warming promoted growth and reduced phenolic concentration in stems of P. tremula with little difference between the sexes during the adult vegetative phase. UVB had no individual effects on any of the studied variables, implying that the plants were fairly tolerant to increased UVB levels. [ABSTRACT FROM AUTHOR]

Abstract: Aim: We investigate the effects of the environmental and geographical processes driving growth resilience and recovery in response to drought in Mediterranean Pinus pinaster forests. We explicitly consider how intraspecific variability modulates growth resilience to drought. Location: Western Mediterranean basin. Methods: We analysed tree rings from a large network of 48 forests (836 trees) encompassing wide ecological and climatic gradients, including six provenances. To characterize the major constraints of P. pinaster growth under extremely dry conditions, we simulated growth responses to temperature and soil moisture using a process‐based growth model coupled with the quantification of climate–growth relationships. Then, we related growth–resilience indices to provenance and site variables considering different drought events. Results: Pinus pinaster displayed strong variation in growth resilience across its distributional range, but common patterns were found within each provenance. Post‐drought resilience increased with elevation and drier conditions but decreased with spring precipitation. Trees from dry sites were less resistant to drought but recovered faster than trees from wet sites. Main conclusions: Resilience strategies differed among tree provenances: wet forests showed higher growth resistance to drought, while dry forests presented faster growth recovery, suggesting different impacts of climate warming on forest productivity. We detected geographically structured resilience patterns corresponding to different provenances, confirming high intraspecific variability in response to drought. This information should be included in species distribution models to simulate forest responses to climate warming and forecasted aridification. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Seasonally dry tropical forest (SDTF) of the Caribbean Islands (primarily West Indies) is floristically distinct from Neotropical SDTF in Central and South America. We evaluate whether tree species composition was associated with climatic gradients or geographical distance. Turnover (dissimilarity) in species composition of different islands or among more distant sites would suggest communities structured by speciation and dispersal limitations. A nested pattern would be consistent with a steep resource gradient. Correlation of species composition with climatic variation would suggest communities structured by broad‐scale environmental filtering. Location: The West Indies (The Bahamas, Cuba, Hispaniola, Jamaica, Puerto Rico, US Virgin Islands, Guadeloupe, Martinique, St. Lucia), Providencia (Colombia), south Florida (USA) and Florida Keys (USA). Taxon: Seed plants—woody taxa (primarily trees). Methods: We compiled 572 plots from 23 surveys conducted between 1969 and 2016. Hierarchical clustering of species in plots, and indicator species analysis for the resulting groups of sites, identified geographical patterns of turnover in species composition. Nonparametric analysis of variance, applied to principal components of bioclimatic variables, determined the degree of covariation in climate with location. Nestedness versus turnover in species composition was evaluated using beta diversity partitioning. Generalized dissimilarity modelling partitioned the effect of climate versus geographical distance on species composition. Results: Despite a set of commonly occurring species, SDTF tree community composition was distinct among islands and was characterized by spatial turnover on climatic gradients that covaried with geographical gradients. Greater Antillean islands were characterized by endemic indicator species. Northern subtropical areas supported distinct, rather than nested, SDTF communities in spite of low levels of endemism. Main conclusions: The SDTF species composition was correlated with climatic variation. SDTF on large Greater Antillean islands (Hispaniola, Jamaica and Cuba) was characterized by endemic species, consistent with their geological history and the biogeography of plant lineages. These results suggest that both environmental filtering and speciation shape Caribbean SDTF tree communities. [ABSTRACT FROM AUTHOR]

Trees serve as a valuable asset in the urban built environment. In an arid city like Phoenix, trees are one of the primary urban green infrastructures to ameliorate extreme heat stress. Because of the cost of water and space in the desert residential environment, designing the optimal tree arrangement to maximize overall thermal benefits for residential neighborhoods is important and necessary. In this research, we first simulated a real neighborhood with current tree arrangement in ENVI-met (a holistic three-dimensional model for the simulation of surface-plant-air interactions), and validated the reliability of ENVI-met models by comparing the simulated results with systematic temperature collection transects. Further, we evaluated and compared differences in outdoor microclimates and human thermal comfort by simulating different tree layouts (clustered, equal interval, or dispersed) in the same neighborhood. Tree benefits at individual building scale and neighborhood scale are also compared and discussed. Based on the simulation, an equal interval two trees arrangement provided the most microclimate and human thermal comfort benefits in the neighborhood due to the importance of shading in the hot arid desert environment, following by clustered tree arrangement without canopy overlap. These findings will help policy makers and urban planners offer better guidelines for planting and establishing residential trees to mitigate extreme heat in the hot arid residential environment. [ABSTRACT FROM AUTHOR]

Worldwide tree mortality as induced by climate change presents a challenge to forest managers. To successfully manage vulnerable forests requires the capacity of regeneration to compensate for losses from tree mortality. We observed rapid regeneration and the growth release of young trees after warming-induced mortality in a David aspen-dominated (Populus davidiana) broad-leaved forest in Inner Mongolia, China, as based on individual tree measurements taken in 2012 and 2015 from a 6-ha permanent plot. Warming and drought stress killed large trees 10–15 m tall with a total number of 2881 trees during 2011–2012, and also thinned the upper crowns. David aspen recruitment increased 2 times during 2012–2015 and resulted in a high transition probability of David aspen replacing the same or other species, whereas the recruitment of Mongolian oak (Quercus mongolica) was much lower: it decreased from 2012 to 2015, indicating that rapid regeneration represented a regrowth phase for David aspen, and not succession to Mongolian oak. Further, we found that the recruitment density increased with canopy openness, thus implying that warming-induced mortality enhanced regeneration. Our results suggest that David aspen has a high regrowth ability to offset individual losses from warming-induced mortality. This important insight has implications for managing this vulnerable forest in the semi-arid region of northern China. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Vegetation is sensitive to mean annual precipitation (MAP), but the sensitivity of vegetation to precipitation variability (PV) is less clear. Tropical ecosystems are likely to experience increased PV in the future. Here we assessed the importance, magnitude and mechanism of PV effects on tree cover in the context of covarying environmental drivers such as fire, temperature and soil properties. Location: Tropical land. Time period: 2000–2010. Major taxa studied: Trees. Methods: We compiled climate, soil and remotely‐sensed tree cover data over tropical land. We then comprehensively assessed the contribution of PV at different time‐scales to tropical tree cover variations and estimated the sensitivity of tree cover to PV changes by conducting rolling‐window regression and variance decomposition analyses. We further adopted a mechanistic modelling approach to test whether water competition between trees and grasses can explain the observed effect of PV. Results: We find that PV contributes 33–56% to the total explained spatial variation (65–79%) in tree cover. The contribution of PV depends on MAP and is highest under intermediate MAP (500–1,500 mm). Tree cover generally increases with rainy day frequency and wet season length but shows mixed responses to inter‐annual PV. Based on the estimated sensitivity, tropical tree cover can decrease by 3–5% overall and by up to 20% in Amazonia under a 20% decrease in rainy days. Mechanistic modelling analysis reproduced the continental differences in tree cover along an MAP gradient. Main conclusions: Under intermediate rainfall regimes (500–1,500 mm), PV can be a more important determinant of tropical tree cover than conventionally proposed drivers such as MAP and fire. The effect of PV likely results from the sensitivity of tree–grass competition to the temporal distribution of water resources. These results show that climate variability can strongly shape the biosphere. [ABSTRACT FROM AUTHOR]

Abstract: In response to climate warming, subalpine treelines are expected to move up in elevation since treelines are generally controlled by growing season temperature. Where treeline is advancing, dispersal differences and early life stage environmental tolerances are likely to affect how species expand their ranges. Species with an establishment advantage will colonize newly available habitat first, potentially excluding species that have slower establishment rates. Using a network of plots across five mountain ranges, we described patterns of upslope elevational range shift for the two dominant Great Basin subalpine species, limber pine and Great Basin bristlecone pine. We found that the Great Basin treeline for these species is expanding upslope with a mean vertical elevation shift of 19.1 m since 1950, which is lower than what we might expect based on temperature increases alone. The largest advances were on limber pine‐dominated granitic soils, on west aspects, and at lower latitudes. Bristlecone pine juveniles establishing above treeline share some environmental associations with bristlecone adults. Limber pine above‐treeline juveniles, in contrast, are prevalent across environmental conditions and share few environmental associations with limber pine adults. Strikingly, limber pine is establishing above treeline throughout the region without regard to site characteristic such as soil type, slope, aspect, or soil texture. Although limber pine is often rare at treeline where it coexists with bristlecone pine, limber pine juveniles dominate above treeline even on calcareous soils that are core bristlecone pine habitat. Limber pine is successfully “leap‐frogging” over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment. This early‐stage dominance indicates the potential for the species composition of treeline to change in response to climate change. More broadly, it shows how species differences in dispersal and establishment may result in future communities with very different specific composition. [ABSTRACT FROM AUTHOR]

In order to anticipate the ecological impacts of climate change and model changes to forests, it is important to understand the factors controlling spring leaf out. Leaf out phenology in woody trees and shrubs is generally considered to be strongly controlled by a combination of spring warming, winter chilling requirement, and photoperiod. However, researchers have recently suggested that temperature-related air humidity, rather than temperature itself, might be the main trigger of the spring leaf-out of woody plants. Here, we sought to examine the relationship between air humidity and leaf-out across a range of humidities and plant functional groups. We did not find any consistent, measurable effect of high humidity advancing leaf-out in the 15 woody shrubs and trees examined in this study, and we did not see progressive patterns of earlier leaf-out in successively higher humidities. Our results indicate that more work must be done on this topic before researchers can properly determine the effect of humidity on the leafing out process for woody species. [ABSTRACT FROM AUTHOR]

The humid forests of Amazonia are experiencing longer and more intense dry seasons, which are predicted to intensify by the end of the 21st century. Although tree species often have long generation times, they may still have the capacity to rapidly respond to changing climatic conditions through adaptive phenotypic plasticity. We, therefore, predicted that Amazonian trees have shifted their leaf morphology in response to the recent drier climate. We tested this prediction by analysing historical herbarium specimens of six Amazonian tree species collected over a 60-year period and comparing changes in leaf morphology with historical precipitation data. Moreover, we explored spatial and temporal biases in herbarium specimens and accounted for their potentially confounding effect in our analysis. We found pronounced biases in herbarium specimens, with nearly 20% of specimens collected in close geographic proximity and around the 1975s. When accounting for such biases, our results indicate a trend of decreasing leaf size after the 1970s, which may have been spurred by an observed reduction in rainfall. Our findings support the hypothesis that (some) Amazonian trees have the capacity to adaptively change their leaf phenotypes in response to the recent drier climate. Nevertheless, the unavoidable spatial and temporal biases in herbarium specimens call for caution when generalizing our findings to all Amazonian trees. [ABSTRACT FROM AUTHOR]

Shoot flushes alternate with root flushes and the evergreen red milkwood (Mimusops zeyheriSond.) fruit tree has winter (May–July) and summer (October-December) shoot flushes in southern hemisphere. Fruit of this plant contain high vitamin C and the tree is being researched and bred for arid inland southern Africa regions. Climate change predictions suggested that by 2030 the regions would experience high temperatures (>45°C), recurrent floods and repeated droughts, which are associated with increased salinity challenges. The objective of this study was to determine the degree of salt tolerance inM. zeyheriseedlings to chloride and carbonate salinity during summer and winter shoot flushes under microplot conditions. Treatments, comprising untreated control, NaCl, KCl, CaCl2and Na2CO3each at 1.0 molar (M) solutions, were applied weekly for eight weeks. During both seasons, CaCl2and Na2CO3salinity had significant effects on soil pH and EC. During summer, salt types increased (106%–253%) dry shoot mass and reduced (53%–79%) root/shoot ratio. During winter, Na2CO3salinity increased (114%) dry shoot mass, but the effects were not different to those induced by NaCl and CaCl2salinity. All other plant growth variables were not affected by salt type. Salt type had significant effects on assimilation of selected nutrient elements in leaf tissues ofM. zeyheriseedlings during winter. Sodium chloride did not have significant effects on nutrient elements, whereas KCl, CaCl2and Na2CO3significantly affected selected macronutrient elements and Zn. In conclusion, effects of chloride and carbonate salinity onM. zeyheriseedlings were both season- and salt type-specific, with seedlings displaying some degree of salt tolerance to chloride and carbonate salinity. [ABSTRACT FROM AUTHOR]

Climate change refers to a paradigm shift in the climatic pattern of a location, region or planet which is linked with average weather components, such as temperature, wind patterns and precipitations. Climate change results in erratic events such as rising global temperature, intensified drought, flooding, cyclones, low or poor agricultural productivity, loss of biodiversity and shifting of seasons. Natural processes such as variations in the intensity of the sun, eruptions from volcanoes, very slow changes in ocean circulations and land surfaces can cause this global climate change but human activities are by far the major causes through the continuous release of greenhouse gases and aerosols into the atmosphere, by altering land surfaces, and or depleting the ozone layer. The most environmentally conservative response to climate change mitigation would be to stop the consumption of fossil fuels and production of methane and chlorofluorocarbons; but these options may not be feasible until alternative technologies emanate. Considering the large amounts of carbon accumulated as biomass in plantations, extensive planting of trees, which posses large canopies that are able to capture carbon dioxide (CO2) from the atmosphere, could help mitigate the rising atmospheric CO2 levels. The roles of plantations in mitigating global climate change are related, but not limited to the following: the influence of trees on the hydrologic cycle, the barrier against destructive windstorm and desertification, conservation of the soil surface against erosion and intense heat, binding action of the dense root system, sustainable biodiversity, provision of renewable and bioenergy, nutritious food, employment, and rural income, and the reservoir of sequestered carbon. There is an urgent need to properly integrate trees and plantations in our agricultural systems, homes, institutions, markets, parks and other public places. This would not only help to reduce the build-up of carbondioxide and other atmospheric impurities but also increase the produce from plantation crops in a locality thereby mitigating against food insecurity and poverty. [ABSTRACT FROM AUTHOR]

The relationship between climate and radial tree growth is traditionally used to reconstruct past climate conditions based on interannual tree-ring variations. However, few studies have used these climate-growth relationships to model the radial tree growth based on future climate projections. To detect the future forest dynamics, the climate-induced tree growth from 2006 to 2100 was projected using temperature changes under representative concentration pathway (RCP) 2.6 for the southeastern Tibetan Plateau. Radial tree growth was mainly controlled by annual mean temperature in this region. Based on the relationship between regional annual mean temperature and radial tree growth, a regression model was built that explained 62.5% of variance in the observed temperature record over the period 1911–2005. A period of unprecedented radial tree growth was found after 1998 when compared with the tree growth in the past 700 years. We found that radial tree growth would increase in the period 2006–2045 and decline after that period due to the projected temperature decrease. As forest productivity and biomass are expected to increase with the increased tree growth, these results suggest that temperature-limited systems could see future increases in productivity as growth limitations are lessened. The results of this research could be used to predict regional forest dynamics in the future. [ABSTRACT FROM AUTHOR]

Over 200 000 forest inventory and ecological ground plots representing North America north of 36 degrees latitude were used to develop a climate niche model predicting the current distribution of black spruce (Picea mariana (Mill.)) across its natural range. The resulting 8-variable Random Forest algorithm had a 4.4 per cent overall error rate. This error was primarily a function of errors of commission, i.e. predicting presence of black spruce for plots in which it was absent (error = 6 per cent). In contrast, errors of omission, predicting an absence of black spruce when it was present, was 0.1 per cent. Height growth data from four disparate provenance test series containing a total of 316 populations were analysed using linear mixed model procedures to model the pattern of ecological genetic variation. The resulting model accounted for 62 per cent of the observed variation among populations. Climatic surfaces for the IPCC RCP6.0 scenario at three time steps (decades centred on 2030, 2060 and 2090) projected early and sustained geographic shifts in the realized climatic niche. Approximately 56 per cent of the contemporary distribution is predicted to be lost or threatened habitat by 2060. Mapped projections indicate the shift in the trailing edge encompasses the entire managed boreal forest in Canada. Emergent suitable habitat totalled 28 per cent. Projections of the ecological genetic model into the climate of the decade centred on 2060 indicate the challenge for forest management is in assuring a timely transfer of trailing edge populations to the future location of the climates for which they are optimally suited. [ABSTRACT FROM AUTHOR]

Climate warming is expected to enhance productivity and growth of woody plants, particularly in temperature-limited environments at the northernmost or uppermost limits of their distribution. However, this warming is spatially uneven and temporally variable, and the rise in temperatures differently affects biomes and growth forms. Here, applying a dendroecological approach with generalized additive mixed models, we analysed how the growth of shrubby junipers and coexisting trees (larch and pine species) responds to rising temperatures along a 5000-km latitudinal range including sites from the Polar, Alpine to the Mediterranean biomes. We hypothesize that, being more coupled to ground microclimate, junipers will be less influenced by atmospheric conditions and will less respond to the post-1950 climate warming than coexisting standing trees. Unexpectedly, shrub and tree growth forms revealed divergent growth trends in all the three biomes, with juniper performing better than trees at Mediterranean than at Polar and Alpine sites. The post-1980s decline of tree growth in Mediterranean sites might be induced by drought stress amplified by climate warming and did not affect junipers. We conclude that different but coexisting long-living growth forms can respond differently to the same climate factor and that, even in temperature-limited area, other drivers like the duration of snow cover might locally play a fundamental role on woody plants growth across Europe. [ABSTRACT FROM AUTHOR]

The last resort for conservation of rare tree populations in refugial areas under high risk of climate driven extinction may be ex situ conservation and assisted translocation. Although such actions require detailed knowledge about the spatial scale and heterogeneity of the within-population distribution of genetic diversity, it is still unknown whether fine-scale spatial genetic structure (FSGS) is present in refugial populations of forest trees. In order to address this issue, we carried out the first whole-population genetic characterisation of a small and isolated refugial population of the IUCN red-listed Serbian spruce [ Picea omorika (Panč.) Purk.] from the Balkans. All 418 adult individuals were georeferenced and genotyped at nuclear EST-SSRs and at a mitochondrial (mtDNA) locus. Spatial autocorrelation analyses provided only a simplified description of FSGS, which is concordant with findings in wind-pollinated species with limited seed dispersal. However, Bayesian analysis revealed three heterogeneous, highly differentiated (pairwise G' > 0.3), and spatially localised sub-populations showing only partial overlap with the distribution of mtDNA haplotypes. Such complex structure in only 0.34 ha, resulting mainly from historical events, restrictions to gene flow and high local density, was undetected in previous work based on more traditional sampling schemes for population genetics surveys. We demonstrate the usefulness of sampling schemes leaning towards a whole-population genetic characterisation in mining the finest characteristics of FSGS, and argue that our understanding of genetic structuring in highly heterogeneous refugial regions at both macro- and micro-scales is still rather limited and often oversimplified. This has severe implications on conservation of plant biodiversity from these regions in terms of responses to global climate change. [ABSTRACT FROM AUTHOR]

Most temperate forest tree species will suffer important environmental changes as result of the climate change. Adaptiveness to local conditions could change at different sites in the future. In this context, the study of intra-specific variability is important to clarify the singularity of different local populations. Phenotypic differentiation between three beech provenances covering a wide latitudinal range (Spain/ES, Germany/DE and Sweden/SE), was studied in a greenhouse experiment. Non-target leaf metabolite profiles and ecophysiological response was analyzed in well-watered and water stressed seedlings. There was a provenance-specific pattern in the relative concentrations of some leaf metabolites regardless watering treatment. The DE and SE from the center and north of the distribution area of the species showed a clear differentiation from the ES provenance in the relative concentration of some metabolites. Thus the ES provenance from the south maintained larger relative concentration of some organic and amino acids (e.g. fumaric and succinic acids or valine and isoleucine), and in some secondary metabolites (e.g. kaempferol, caffeic and ferulic acids). The ecophysiological response to mild water stress was similar among the three provenances as a consequence of the moderate water stress applied to seedlings, although leaf N isotope composition (δ 15 N) and leaf C:N ratio were higher and lower respectively in DE than in the other two provenances. This would suggest potential differences in the capacity to uptake and post-process nitrogen according to provenance. An important focus of the study was to address for the first time inter-provenance leaf metabolic diversity in beech from a non-targeted metabolic profiling approach that allowed differentiation of the three studied provenances. [ABSTRACT FROM AUTHOR]

The article focuses on the cork oak (Quercus suber), including the influence of human beings to the dissemination of tree species, phytotoponyms, and physical environment and distance from transhumance routes.

Defoliation is the main parameter for assessing tree crown conditions, and is the result of cumulative interactions among different types of stressors, including climate, air pollution, pests and diseases, and management systems. Here, we evaluated a long-term data series (1992-2013) provided by the ICP-Forests Level I monitoring network (16 x 16 km) in Romania. Specifically, we investigated how climate influences defoliation at different spatial and temporal levels using statistical analyses. Using periodic climatic data (mean temperature and precipitation) derived from a daily grid dataset (ROCADA) with a resolution of 0.1 x 0.1° (10 x 10 km), we quantified how climatic parameters were correlated with defoliation, which was expressed as the mean tree defoliation per plot (DEF), and the proportion of damaged trees (crown defoliation > 25% - fDEF). The cross-correlation (Spearman r) between defoliation indicators and temperature was positive and relatively constant over time for all broadleaves and conifers, combined and separately, except for Fagus sylvatica (European beech), which had a negative cross-correlation coefficient. The correlation obtained for precipitation was similar to that obtained for temperature; however, this relationship was negative (except, again, for beech). The temporal influence of temperature on defoliation was much lower than that of precipitation, which had the greatest influence in dry regions (south and southeast Romania), especially for Quercus species. Furthermore, precipitation had a positive influence in moderate climate regions for conifers that were situated outside their natural distribution ranges. For beech and conifers situated at the upper altitudinal limits, temperature was negatively correlated with defoliation, i.e., temperature had a positive influence on health status. [ABSTRACT FROM AUTHOR]

The aim of this study was to modify several existing biological models by including several predictive variables that take into account the effect of climatic factors on tree height growth. Tree height was measured from 2007 to 2014 on 18 trees for each of the following species: Eucalyptus urophylla x Eucalyptus grandis, Parapiptadenia rigida, Peltophorum dubium, Mimosa scabrella and Schizolobium parahybae. Different existing nonlinear models were fitted to the observed data, and the best fitting models were selected. The inclusion of climatic variables into the selected models (mainly minimum temperature and rainfall) improved their predictions of tree height growth with age, and provided more accurate estimates than those obtained by traditional nonlinear models. Simulations were carried out to explore the variation of tree height growth under different minimum temperature and precipitation regimes. The effects of frost and rainfall variation on height growth curves and their consequences for forest management are discussed. [ABSTRACT FROM AUTHOR]

The ability of plants to maintain an intact water transport system in leaves under drought conditions is intimately linked to survival and can been be seen as adaptive in shaping species climatic limits. Large differences in leaf hydraulic vulnerability to drought are known among species from contrasting climates, yet whether this trait varies among populations within a single species and, furthermore, whether it is altered by changes in growth conditions, remain unclear. We examined intraspecific variation in both leaf water transport capacity (Kleaf) and leaf hydraulic vulnerability to drought (P50leaf) among eight populations of Corymbia calophylla (R. Br.) K.D. Hill & L.A.S. Johnson (Myrtaceae) from both cool and warm climatic regions grown reciprocally under two temperature treatments representing the cool and warm edge of the species distribution. Kleaf did not vary between cool and warm-climate populations, nor was it affected by variable growth temperature. In contrast, population origin and growth temperature independently altered P50leaf. Using data pooled across growth temperatures, cool-climate populations showed significantly higher leaf hydraulic vulnerability (P50leaf = -3.55 ± 0.18 MPa) than warm-climate populations (P50leaf = -3.78 ± 0.08 MPa). Across populations, P50leaf decreased as population home-climate temperature increased, but was unrelated to rainfall and aridity. For populations from both cool and warm climatic regions, P50leaf was lower under the warmer growth conditions. These results provide evidence of trait plasticity in leaf hydraulic vulnerability to drought in response to variable growth temperature. Furthermore, they suggest that climate, and in particular temperature, may be a strong selective force in shaping intraspecific variation in leaf hydraulic vulnerability to drought. [ABSTRACT FROM AUTHOR]

Changes in the position of altitudinal treelines and timberlines are considered useful indicators of climatic changes on tree growth and forest dynamics. We sought to determine if recent warming is driving contrasting growth responses of Himalayan birch, at moist treeline (Lete Lekh) and semi-arid timberline (Chimang Lekh) sites in the Trans-Himalayan zone of central Nepal. We used dendrochronological techniques to measure tree ring width (TRW) and basal area increment (BAI) of birch trees from climatically contrasting but nearby sites. The TRW series were correlated with climate records from nearby meteorological stations, and BAI was compared between populations to explore growth trends over recent decades. We found contrasting precipitation trends between nearby sites such that the wet site (Lete) is getting warmer and wetter, and the dry site (Chimang) is getting warmer and drier in recent decades. The radial growth of birch in both moist and semi-arid sites are positively correlated to spring (March-May) rainfall, and negatively correlated to mean and maximum temperature for the same period. The growth climate analysis indicated that moisture availability in early growing season is crucial for birch growth at these locations. The BAI of birch is declining more rapidly at the dry timberline than at the moist treelines in the recent decades, indicating that climatic warming might negatively impact birch radial growth where warming interacts with increasing spring drought in the region. Our work highlights contrasting growth response of birch to climate change at moist and semi-arid forests indicating that local climatic variation must be accounted for when assessing and forecasting regional patterns of tree growth in topographically complex regions like Trans-Himalaya, in order to make accurate predictions of vegetation responses to climate change. [ABSTRACT FROM AUTHOR]

The natural expansion of forestry trees into habitats outside plantations is a concern for managers and conservationists. We studied seedling emergence and survival of the two main forestry species in Portugal: Eucalyptus globulus (exotic) and Pinus pinaster (native); using a seed addition experiment. Our main objective was to evaluate the combined effects of climate (mild-summer and warm-summer climate), habitat (oak forest and shrubland), and disturbance (vegetation removal and non-disturbance) on the seedling establishment of species in semi- and natural habitats. Furthermore, we tested the effect of the 'sowing season' (autumn and spring) on seedling emergence and survival. Overall, seedling establishment of both species was enhanced by light and water. However, we found important interactions among climate, habitat, and disturbance on both species' emergence and survival. The differences between habitats were more evident in the mild-summer climate than in the warm-summer climate. Our results also suggested that seedling survival may be enhanced by shrub cover in drier conditions (warm-summer climate). Eucalyptus globulus appears more sensitive to drought and disturbance changes than P. pinaster. In shrublands and mild-summer climate conditions, disturbance especially promoted E. globulus seedling establishment, while the forest canopy and the shade appeared to control it in both climatic conditions. After the first summer life, very low seedling survival was observed in both species, although the colonization of new areas appeared to be more limited for E. globulus. Our study suggests that climate conditions influence the effect (direction and intensity) of habitat and disturbance (plant-plant interactions) on seedling survival. Thus, the effect of light availability (forest canopy) and disturbance (vegetation removal) on these species establishment is climate context-dependent. This study presents very useful information to understand future shifts in these species distribution and has direct applications for the management of natural establishment outside the planted areas, and the management of the understorey to favor forest regeneration or limit forest colonization. [ABSTRACT FROM AUTHOR]

Climate change has increased the need of information on amount of forest biomass. The biomass and carbon storage for larch ( Larix spp.) in large geographic regions in China were failed to be accurately estimated from current biomass equations, because they were usually based on a few sample trees on local sites, generally incompatible to volume estimation, and not additive between components and total biomass. China needs reliable biomass estimation of the important species in the whole country. This study was based on the mensuration data of above- and belowground biomass from 600 and 198 destructive sample trees of larch from four regions in China, respectively. The main purpose was to develop compatible individual tree equations on both national and regional levels for above- and belowground biomass, biomass conversion factor and root-to-shoot ratio, using the nonlinear error-in-variable simultaneous equation approach. In addition, diameter at breast height ( D) and tree height ( H) growth models were also developed, and effects of key climate variables on biomass variation and growth process were analyzed. The results showed that mean prediction errors (MPEs) of regional aboveground biomass models were from 3.86 to 7.52%, and total relative errors (TREs) are within ±3%; and for regional belowground biomass equations, the MPEs are from 9.91 to 28.85%, and the TREs are within ±4%. The above- and belowground biomass and D- and H-growth were significantly related to mean annual temperature and mean annual precipitation. The biomass equations and growth models developed in this paper will provide good basis for estimating and predicting biomass of larch forests in China. [ABSTRACT FROM AUTHOR]

We selected two sites dominated by the sub-Mediterranean oak Quercus pyrenaica Willd. close to its distribution boundary in northwestern Iberia, within a mountain region with a high winter precipitation. The sites differed in their soil water regime, corresponding to the edge of a peat bog, and to a moderate slope. We obtained tree-ring chronologies of total ring width (RW), and mean earlywood vessel area (MVA); their responses to climatic factors were compared for the period 1945-2002. RW presented a higher chronology quality than MVA, but was rather independent of climate, probably because of the presence of recurrent growth reductions. In contrast, MVA was closely related to precipitation during April and May, whereby a high water availability was coupled to smaller vessels. We found remarkable differences between the climatic signal of both stands, as trees growing on the peat soil responded later and with considerably lower intensity. We hypothesize that spring waterlogging causes that the response at the wettest site occurs only when soil desiccation begins, which results in a delayed climatic signal, and also lower intra- and inter-annual variation due to more homogeneous conditions. Climate-growth relationships at the driest site were mainly associated with the first row, whereas it is vessels expanding later in the season that show this relation for the moist site. Our results confirm that MVA chronologies are reliable proxies of both regional and local climatic conditions, but only a careful optimization by selecting vessel subsets does provide a complete view of their potential. [ABSTRACT FROM AUTHOR]

A better understanding of the ecophysiological basis of wood formation by monitoring radial growth over the whole vegetation period may help to explain possible discrepancies between long-term average climate-growth relationships and short-term climatic impacts on tree growth. To understand how growth-climate associations of Oriental beech vary throughout a vegetation period, we studied seasonal growth patterns of high-elevation beech trees growing in the north of Iran by collecting wood anatomical micro-cores in 10 to bi-weekly intervals and measuring stem increment with high-resolution electronic dendrometers. Wood formation was for two consecutive years with contrasting inter-annual climate conditions (2011 and 2012). We divided the growing period into three equal time phases and related daily climate variability to the cambial growth in each phase. The pattern of climate-growth relationships varies over a complete growing season and between years: in both study years, trees responded homogenously at the beginning and at the end of the growing season, but showed opposing influence of relative humidity during spring and early summer (June and July). Temperature as the main driver of xylogenesis had a stimulating effect on growth at the beginning of the growing season, but had negative effects on radial increment during late June and July mainly due to the excess of ambient temperatures over an optimum threshold. Higher temperature in late June and July 2011 compared with those of 2012 led to a significantly narrower tree ring in 2011, despite the similar sums/means of annual climate parameters in these two years. Since regional climate change scenarios expect higher temperature and reduced moisture conditions in future, radial growth of beech in the north of Iran may be adversely affected. [ABSTRACT FROM AUTHOR]

Contemporary forest inventory data are widely used to understand environmental controls on tree species distributions and to construct models to project forest responses to climate change, but the stability and representativeness of contemporary tree-climate relationships are poorly understood. We show that tree-climate relationships for 15 tree genera in the upper Midwestern US have significantly altered over the last two centuries due to historical land-use and climate change. Realised niches have shifted towards higher minimum temperatures and higher rainfall. A new attribution method implicates both historical climate change and land-use in these shifts, with the relative importance varying among genera and climate variables. Most climate/land-use interactions are compounding, in which historical land-use reinforces shifts in species-climate relationships toward wetter distributions, or confounding, in which land-use complicates shifts towards warmer distributions. Compounding interactions imply that contemporary-based models of species distributions may underestimate species resilience to climate change. [ABSTRACT FROM AUTHOR]