Key Tree Species Research Articles

Site-based climate-smart tree species selection for forestation under climate change

Global climate change threatens ecosystem functions and resilience, prompting large-scale planting initiatives to mitigate its impacts. To ensure new plantations are adaptive to future climates, it is crucial to consider climate mismatches resulting from climate change when selecting tree species. However, current research is all species-based, which is not effective for species selection across species at specific plantation sites. Our research developed a novel site-based approach that can identify optimal tree species for specific planting sites under projected future climates. We evaluated the feasibility and effectiveness of this method across 10 representative sites in diverse climatic zones in China based on climate niche projections for 100 key tree species. Our findings demonstrated the necessity and effectiveness of this approach, which can select a suit of suitable tree species tailored for any potential planting site across China under different climate change scenarios. For instance, at Tibet Dongjiu Forest farm, Aibes densa and Quercus pannosa currently showed high suitability scores above 0.8 (on a scale of 0–1). However, by the 2080s, Aibes densa's suitability was projected to drop to 0.25, while Quercus pannosa was expected to maintain its suitability. Conversely, Quercus aquifolioides currently had a low suitability of 0.08, but it was projected to increase to 0.74 by the 2080s. These findings demonstrate the importance of using this approach to avoid selecting the wrong species or overlooking potentially suitable species. In addition, our simulation analysis suggests that a dataset of 40–50 species is necessary to ensure that most planting sites can identify 2–3 suitable species. This advancement significantly enhances the precision and effectiveness of tree species selection strategies for local practitioners, offering vital insights for forestry, conservation, and ecological restoration projects. These results highlight the tremendous potential and practical applicability of our site-based approach in enhancing forestry adaptation and ecological functions in response to global climate change.

The linkage between functional traits and drone-derived phenology of 74 Northern Hemisphere tree species

Tree phenology is a major component of the global carbon and water cycle, serving as a fingerprint of climate change, and exhibiting significant variability both within and between species. In the emerging field of drone monitoring, it remains unclear whether this phenological variability can be effectively captured across numerous tree species. Additionally, the drivers behind interspecific variations in the phenology of deciduous trees are poorly understood, although they may be linked to plant functional traits. In this study, we derived the start of season (SOS), end of season (EOS), and length of season (LOS) for 3099 individuals from 74 deciduous tree species of the Northern Hemisphere at a unique study site in southeast Germany using drone imagery. We validated these phenological metrics with in-situ data and analyzed the interspecific variability in terms of plant functional traits. The drone-derived SOS and EOS showed high agreement with ground observations of leaf unfolding (R2 = 0.49) and leaf discoloration (R2 = 0.79), indicating that this methodology robustly captures phenology at the individual level with low temporal and human effort. Both intra- and interspecific phenological variability were high in spring and autumn, leading to differences in the LOS of up to two months under almost identical environmental conditions. Functional traits such as seed dry mass, chromosome number, and continent of origin played significant roles in explaining interspecific phenological differences in SOS, EOS, and LOS, respectively. In total, 55 %, 39 %, and 45 % of interspecific variation in SOS, EOS, and LOS could be explained by the Boosted Regression Tree (BRT) models based on functional traits. Our findings encourage new research avenues in tree phenology and advance our understanding of the growth strategies of key tree species in the Northern Hemisphere.

What we know about Turkey oak (Quercus cerris L.) — from evolutionary history to species ecology

Abstract Turkey oak (Quercus cerris L.) is a deciduous tree species of the genus Quercus section Cerris (Fagaceae), widely distributed in Europe and Asia Minor. Throughout its vast distribution range, the species carries high phenotypic and genetic variability. Due to its high drought tolerance, Turkey oak may have great potential to be a key tree species in Central and Western Europe under climate change conditions. However, more detailed information on its phylogeny, phylogeography, phenotypic, and genetic variability is still needed for a more careful and reliable assessment of the species’ adaptation potential. To this end, based on 41 reviewed articles, we collected detailed information to support the evaluation of Turkey oak’s adaptation potential under climate change. In the reviewed articles, we observed a significantly lower number of genetic studies of the members of the section Cerris (especially the Euro-Mediterranean species) relative to the subgenus Quercus. We also identified research gaps with respect to the functional and population genetics of the species that should be addressed in the future. Nevertheless, the different evolutionary background and adaptation strategies of Turkey oak as compared to Central European white oaks, as well as its high phenotypic and genetic variability, may indeed represent a great potential for this species to support the climate adaptation of forestry in Central and Western Europe.

Vegetation trends and dynamics in Shada Mountain, Saudi Arabia, (1984–2023): insights from Google Earth Engine and R analysis

This research analyses the long-term vegetation trends in Shada Mountain across six elevation zones, utilizing Landsat 5, 7, 8, and 9 imageries processed via Google Earth Engine and R. The study managed differences in images resolution through meticulous calibration and image processing techniques. The study is structured around two objectives: examining the relationship between vegetation and its proximity to streams and land surface temperature and analyzing trends in the Normalized Difference Vegetation Index (NDVI). Regression analysis revealed a negative correlation between vegetation and proximity to streams in lower zones (1–3), with no significant effect in higher zones (4–6). NDVI trend analysis indicated an overall increase in vegetation across most zones, with the exception of zone 5, which displayed a negative trend (slope −0.0025). The findings reveal that the decline is particularly pronounced among key tree species such as Ficus cordata subsp. salicifolia and Acacia asak, suggesting potential impacts from climate change and land use alterations. These zone-specific insights deepen our understanding of the dynamic ecological processes in semi-arid environments and guide targeted environmental management and conservation efforts.

Growth of Nordic container forest tree seedlings in some peatless and peat-reduced growing media

Carbon emissions and environmental concerns have led to the aspiration to reduce peat extraction and its use as a growing medium (GM). In Nordic Forest tree seedling production, Sphagnum peat has been almost exclusively used as a GM in seedling containers due to its good properties and availability. This study examined the feasibility of several peat-reduced and peat-free GM in container tree seedling production of the key tree species in Nordic forestry (Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. Karst.) and silver birch (Betula pendula Roth) as well as Russian larch (Larix archangelica P. Lawson & C. Lawson ex Trautv.) and common alder (Alnus glutinosa (L.) Gaertn.). Pure or mixed GM, consisting of low-humified Sphagnum peat (pure as a control), harvested Sphagnum moss, wood fiber, cow manure digestate from a biogas plant, and a common reed compost were tested. Seedlings were grown in controlled conditions in greenhouse experiments and also in larger-scale commercial tree nurseries. Peat-reduced media containing peat of at least 50 vol% provided growth that is similar to pure Sphagnum peat for the tested species and container types. All the studied alternative media can yield marketable seedlings, although commonly of reduced size and requiring special adjustments in growing management. The studied media have a potential to reduce or replace peat in seedling production, but adjustments of their physical and chemical properties, as well as of seedling fertigation and management procedures, are required. The economic feasibility and environmental sustainability of these GM, as well as the outplanting success of seedlings grown in these media, remain to be studied.

Climate-affected multi-decadal variations of biogenic volatile organic compounds in Pinus tabuliformis growth rings

Long-term dynamics of biogenic volatile organic compounds (BVOCs) in trees are rarely reported, despite environmental factors (such as climate change) influencing their growth and the subsequent chemical accumulation. For this, tree growth rings provide a promising biological proxy for the long-time variation and correlation with environmental changes. Therefore, tree rings from Pinus tabuliformis (two stem disks and 40 tree cores) were collected in the Taihang Mountain Macaque National Nature Reserve of China. These samples were divided into seven 5-year resolutions over the 34-year period 1985 to 2018. This enabled analysis of multi-decadal variations of compounds and their correlation with climate variability. A total of 292 BVOCs were detected; however, only 18 compounds were found together across all the 7 growth-periods. Temporal analyses showed decreasing trends for monoterpenes (0.026%/yr) and diterpenes (0.120%/yr), whereas alcohols and oxygenated monoterpenes showed increasing trends at 0.031%/yr and 0.042%/yr, respectively. Correlation analyses showed no obvious link to yearly precipitation, while seasonal temperature had a negative effect on monoterpenes and diterpenes but positive effects on alcohols and oxygenated monoterpenes (all P < 0.05). The present study showed that dendrochronology is a suitable method for re-establishing the biological effects from historical climate variability on key tree species.

Inter-provenance variability and phenotypic plasticity of wood and leaf traits related to hydraulic safety and efficiency in seven European beech (Fagus sylvatica L.) provenances differing in yield

Abstract Key message Seven European beech provenances differing largely in growth performance were grown at two common garden sites in Germany and Slovakia. The intra-specific variability of most traits was explained more by phenotypic plasticity than inter-provenance variability, and efficiency-related traits showed a higher phenotypic plasticity than safety-related traits. Context To maintain climate-resilient future forests, replicated common-garden experiments are suited for developing assisted migration strategies for key tree species. Aims We analysed the magnitude of inter-provenance variability and phenotypic plasticity for 12 functional traits of European beech (Fagus sylvatica L.) and analysed whether the climate at the place of origin left an imprint. Moreover, we asked whether growth is unrelated to xylem safety and to what extent the foliar, xylem and growth-related traits are coordinated. Methods Terminal branches were collected from 19-year-old and 22-year-old trees of seven European beech provenances planted at two common garden sites in Germany and Slovakia, respectively. Three hydraulic, three wood anatomical and four foliar traits were measured and related to two growth-related variables. Results At the two sites, the same pair of provenances showed the highest and lowest growth. Nevertheless, a high degree of phenotypic plasticity was observed, as all traits differed significantly between sites after accounting for provenance effects, with hydraulic safety-related traits showing the lowest and efficiency-related traits the highest plasticity. There was no evidence for inter-provenance variability in xylem embolism resistance (P50) or the foliar carbon isotope signature (δ13C), a proxy for intrinsic water use efficiency (iWUE), and both were unrelated to growth. P50 was positively correlated with the lumen-to-sapwood area ratio and vessel density. Conclusions Because of the lacking trade-off between embolism resistance and growth, highly productive provenances can be selected without reducing the drought tolerance of the branch xylem. However, as xylem safety is only one element of a trees’ drought response, it may be beneficial to select provenances with other more conservative drought adaptations such as smaller vessel lumen areas for increasing xylem safety and small supported total leaf areas for reduction of total transpiration.

Adaptation Strategies of Populus euphratica to Arid Environments Based on Leaf Trait Network Analysis in the Mainstream of the Tarim River

Populus euphratica, a key tree species in the ecologically fragile area of the Tarim River Basin, plays a crucial role in maintaining the ecological balance of the desert. In order to explore the response of Populus euphratica leaves to river water resources and drought climate change, the complex topological relationship between the leaf traits of Populus euphratica was comprehensively analyzed by establishing the leaf trait network of the mainstream of the Tarim River, and the central traits that play a key role in regulating the phenotype of Populus euphratica were identified. The adaptation strategies of Populus euphratica to different environments were clarified from the perspective of the overall leaf trait network. The results show that, with a decrease in river water flow, the internal coordination of the leaf traits weakened, forming a looser network structure. In the hyper-arid region, the leaf traits were more independent, the network was simpler, and it was easier for the leaf to coordinate the aggregation of specific traits. Leaf thickness and the related photosynthetic traits are the key to adaptive strategies, particularly the cuticle thickness and midvein vascular bundle area. Leaf anatomical traits are more critical than stoichiometry traits in drought resistance. Leaves tend to give priority to the relationship between structural traits. Populus euphratica leaves adjust their trait modularization through a trait substitution strategy to manage different drought conditions.

Potential of hydrogel treatment in forest regeneration: impact on growth and vitality of Central European tree species

IntroductionDrought negatively affects the growth and yield of plants. Several measures have been employed to improve the drought tolerance of plants, including the application of superabsorbent hydrogel (SAH) to soil. However, studies on the effect of SAH on trees in Central Europe, which has a temperate climate, are scarce.MethodsHere, the effects of SAH treatment on the cultivation of four key tree species in Central European forest ecosystems—European beech, sessile oak, Scots pine, and Norway spruce—were evaluated. Field and greenhouse experiments were conducted; the greenhouse conditions served as the reference for the absence of water stress.Results and DiscussionSAH treatment reduced seedling mortality by 1%–9% in the field experiment. The morphological parameters of the control and SAH-treated seedlings did not significantly differ. Among the tree species, oak seedlings exhibited a positive response to SAH treatment. Spruce, pine, and beech did not respond to SAH treatment; the proline content of SAH-treated conifer leaves was three times higher than that of oak leaves but still very low, revealing no drought stress. The results highlight the significance of employing an individual approach in the application of SAH in forestry, rather than relying on generic measures.

The breeding systems and floral visitors of two widespread African dry forest species of ethnobotanical significance.

Forest products derived from woody trees, such as fruits, seeds, honey, wood and others, are important resources for supporting rural livelihoods. However, little is known about the breeding systems or floral visitors of trees that provide these resources, often due to the difficulty of accessing tree canopies. This study addresses key knowledge gaps from a data poor region, providing information on the breeding systems and contribution of biotic pollination to two trees abundant in south-central Africa, that provide forest product supports for rural livelihoods: Julbernardia paniculata (Benth.) Troupin and Syzygium guineense (Willd.) subsp. barotsense F. White (Fabaceae and Myrtaceae respectively). The breeding systems of these species were assessed by conducting controlled pollination experiments, and then measuring the effects on reproductive success to determine the degree of self-compatibility and pollen limitation. Floral visitors and their behaviour were observed to provide preliminary information on possible pollinator groups. S. guineense appeared to be self-compatible, while J. paniculata showed signs of both self-incompatibility and pollen limitation. Floral visitors of both species were dominated by bees, with native honeybees (Apis mellifera) providing the highest visitation rates. These insights provide the first steps for understanding the reproductive ecology of these key tree species and can help to inform sustained management and conservation aimed at protecting forests and supporting rural livelihoods, as well as broaden the understanding of the floral visitors, and contribution of biotic pollination to forest tree reproductive success.

Future Reductions in Suitable Habitat for Key Tree Species Result in Declining Boreal Forest Aboveground Biomass Carbon in China

China’s forest ecosystem plays a crucial role in carbon sequestration, serving as a cornerstone in China’s journey toward achieving carbon neutrality by 2060. Yet, previous research primarily emphasized climate change’s influence on forest carbon sequestration, neglecting tree species’ suitable area changes. This study combinates the Lund–Potsdam–Jena model (LPJ) and the maximum entropy model (MaxENT) to reveal the coupling impacts of climate and tree species’ suitable area changes on forest aboveground biomass carbon (ABC) in China. Key findings include the following: (1) China’s forests are distributed unevenly, with the northeastern (temperate coniferous broad-leaved mixed forest, TCBMF), southwestern, and southeastern regions (subtropical evergreen broad-leaved forest, SEBF) as primary hubs. Notably, forest ABC rates in TCBMF exhibited a worrisome decline, whereas those in SEBF showed an increasing trend from 1993 to 2012 based on satellite observation and LPJ simulation. (2) Under different future scenarios, the forest ABC in TCBMF is projected to decline steadily from 2015 to 2060, with the SSP5-8.5 scenario recording the greatest decline (−4.6 Mg/ha/10a). Conversely, the forest ABC in SEBF is expected to increase under all scenarios (2015–2060), peaking at 1.3 Mg/ha/10a in SSP5-8.5. (3) Changes in forest ABC are highly attributed to climate and changes in tree species’ highly suitable area. By 2060, the suitable area for Larix gmelinii in TCBMF will significantly reduce to a peak of 65.71 × 104 km2 under SSP5-8.5, while Schima superba Gardner & Champ and Camphora officinarum in SEBF will expand to peaks of 94.07 × 104 km2 and 104.22 × 104 km2, respectively. The geographic detector’s results indicated that the climate and tree species’ suitable area changes showed bi-variate and nonlinear enhanced effects on forest ABC change. These findings would offer effective strategies for achieving carbon neutrality.

Effects of Douglas fir cultivation in German forests on soil seepage water quantity and quality

Norway spruce (Picea abies L.) has been a key tree species and timber source in European forests the last centuries and is increasingly suffering from drought and bark beetle infestations due to climate warming. Current management options include replacing of Norway spruce monocultures with pure and mixed stands of European beech (Fagus sylvatica) that is the naturally dominating tree species in Central Europe. Additionally, Douglas fir (Psudotsuga menziesii), a tree species with high water use efficiency and drought tolerance, is being increasingly cultivated to increase the resilience of European forests and meet the future demand of conifer timber in a warming climate. We studied the seepage water quantity and quality with a particular focus on the nitrate (NO3–) concentration and N leaching under pure and mixed stands of Douglas fir, Norway spruce, and European beech at seven sites in Germany. Additionally, we investigated seepage water concentrations of SO4-S, Ca, Mg, K, Al and hydrological variables (interception, canopy throughfall, transpiration). Looking at the seepage water quantity and quality, the best management option is the cultivation of pure beech stands. However, this is associated with the well-known risk of monocultures concerning ecosystem disturbance. Beech stands showed the highest seepage water quantities and the lowest seepage water concentrations of major cations and anions, including NO3–. Seepage water quantity was the smallest under pure Douglas fir compared to spruce and beech stands. The composition effects of stand tree species on seepage water quality and nutrient leaching were site-dependent. At N-rich sites, pure Douglas fir stands showed higher seepage water NO3– concentrations than spruce and beech stands, whereas the tree species effects were small at N-poor sites. With respect to seepage water quantity and quality, cultivation of mixed Douglas fir–beech stands is a promising option for producing conifer timber and at the same time avoiding increased disturbance risks of mono-species forests under a warmer climate. Our results support the recommendation of mixed Douglas fir–beech stands based on soil quality, ecosystem resilience, and forest economic studies.

Carbon and biodiversity cobenefits of second-growth tropical forest: The role of leaf phenology

Second-growth tropical forests offer important carbon and biodiversity cobenefits, as well as different leaf functional types of tree species. Leaf deciduousness is an important functional trait that can contribute to seasonal and spatial changes in carbon balance. We investigated the distribution pattern of carbon stock, species richness, and functional dominance among trees with differing leaf phenology (evergreen, semideciduous and deciduous) as well as the carbon and biodiversity cobenefits of tree communities in contrasting topographical conditions in a second-growth tropical Atlantic forest. We tested the hypotheses that topographic conditions shape differences in species richness and aboveground carbon stock between leaf phenology groups, as well as the carbon-biodiversity cobenefits within the tree communities. We studied fourteen 20 m × 40 m plots established in the forest with contrasting topographical conditions. We selected the mean functional traits related to carbon stock capacity in tropical forest: wood density and maximum tree height and calculated community-weighted mean metrics based on these traits. Aboveground biomass of trees for each stem sampled was calculated from a combination of variables using the general allometric equation. We constructed linear mixed-effect models (LMMs, with random and fixed effects) to test the cobenefits between aboveground carbon stock and leaf phenology group (evergreen, semideciduous and deciduous species) on species richness at community level. Our results showed that evergreen species had a higher richness, while the deciduous species had a greater contribution to aboveground carbon stock. Thus, the leaf phenology groups can affect the relationships between species richness and aboveground carbon stock. The deciduous species are key to maintaining higher carbon stock with smaller numbers of species; meanwhile evergreen species are important to maintain a higher species richness. Leaf phenology groups could be responsible for important cobenefits (i.e. positive aboveground carbon stock and species richness relationship) in Atlantic forests. Therefore, this study showed a relevant result on the relative contribution of leaf phenology groups in the carbon and biodiversity cobenefits along topographic gradients. In addition, our results allow for the selection of key tree species to improve management, conservation and restoration practices in the Atlantic forest in order to protect threatened biodiversity as a cobenefit of maintaining forests and the carbon they store.

Litterfall and nutrient transfer dynamics in a successional gradient of tropical dry forest in Colombia

Introduction: The litterfall production, foliar nutrient dynamics and decomposition are essential to maintain nutrient cycling, soil fertility, and carbon regulation in terrestrial ecosystems. With several studies addressing the variation of these processes, their dynamics in tropical dry forests (TDFs) remain unclear, due to its complex interaction of biotic and abiotic factors. Objective: To evaluate litterfall, nutrient potential return and use efficiency, and decomposition variation in a TDF successional gradient in Tolima, Colombia. Methods: We quantified litterfall from November 2017 to October 2019 in 12 plots distributed in four successional stages: initial, early, intermediate, and late forests. We identified key tree species in foliar litter production and characterized the foliar decomposition of these species. At the community level, we quantified the C, N and P potential return, the N and P use efficiency, and the C:N and N:P ratio. Subsequently, we analyze relationships between vegetation characteristics and some soil chemical properties with these ecological processes. Results: We found that total litterfall in late forests (8.46 Mg ha-1 y-1) was double that found in initial forests (4.45 Mg ha-1 y-1). Decomposition was higher in initial (k = 1.28) compared to intermediate (k = 0.97) and late forests (k = 0.87). The nutrient potential return didn’t change along succession, but it did show differences between study sites. The structural development and species richness favored litterfall, while soil chemical conditions influenced nutrient returns and decomposition. Conclusions: TDFs could recover key ecosystem function related to litterfall and nutrient dynamics after disturbances cessation; however, the soil quality is fundamental in return and release of nutrients.

Breaking out from a restricted range: Alternative habitat models to assess population perspectives

Habitat conservation for restricted-range species should also consider adjacent areas, but the analytical approaches for such assessments (particularly for a future perspective) are constrained by currently observed habitat relationships. We used two conceptually different habitat modelling approaches for analysing habitat distribution for the isolated Estonian population of a species of European conservation concern, the Siberian flying squirrel (Pteromys volans (Linnaeus, 1758)). We expected that the correlative (statistical) approaches based on current location data will increasingly deviate along with the distance from the current range, compared with a mechanistic approach based on limiting factors for the species. For conservation planning, we also investigated how the current protected area network covers quality habitats around the current range. We constructed three alternative correlative models (MaxEnt; Random forest; Generalized Boosted Regression) utilizing remote-sensing (Sentinel-2; LiDAR) and forest inventory data for 1299 occurrences in the currently occupied ca. 1400 km2 range. A mechanistic model was constructed as a decision tree that distinguished 11 quality classes of forest land based on the ecological prioritization of limiting factors: site type; forest cover; abundance of key tree species; stand age; patch size; and layer structure. Supporting our expectation, an overall good accordance of habitat predictions of all the correlative models and the mechanistic model (at 30 × 30 m pixel size) declined with the distance from the current range. The MaxEnt model most closely followed the full range of habitat quality classes of the mechanistic model, while the other correlative models emphasized the highest habitat-quality class. Within the current range, both MaxEnt and the mechanistic model similarly revealed habitat quality differences between occupied and unoccupied species protection areas. Delineation of habitat aggregations all over the country based on the mechanistic model revealed habitat loss both within and adjacent to the current range, which sets limits to local population recovery. For analysing wider options, we recommend complementing statistical spatial modelling of current conditions with ecologically sound mechanistic approaches. Based on our specific case, we outline how such model predictions can be assessed for management planning beyond current range.

Diurnal and nocturnal tree species selection by koalas demonstrates individual preferences in a peri-urban landscape

In New South Wales, legislation governing land clearing and development as it relates to koala conservation acts to prevent the destruction of habitat containing key tree species used by koalas. The identification of these key tree species is therefore critical to koala conservation. We aimed to compile a list of tree species used by koalas within the Wollondilly Shire region and investigate tree-use preferences. We radio-collared one female and four male koalas and tracked their movements over a period of 107–195 days. We conducted surveys within each koala’s home range to quantify the relative availability of each tree species, which we compared with their relative frequency of use. Koalas used 19 different tree species (17 during day, 12 during night), despite over 32 species being available. Eight species were preferentially used by one or more koalas; these were Eucalyptuts bosistoana, E. longifolia, E. puncata, E. crebra, E. globoidea, E. pilularis, E. tereticornis and Angophora floribunda. Two species were avoided: Corymbia gummifera and Acacia decurrens. Koalas consistently used larger trees relative to their availability, and we found a general but non-significant trend towards the use of larger trees at night compared with during the day. To achieve koala conservation, it will be necessary to preserve habitat patches comprising a diverse mixture of tree species and sizes, particularly trees >35 cm diameter at breast height (DBH), and to appropriately revegetate land with these criteria in mind.

Climate and fire drivers of forest composition and openness in the Changbai Mountains since the Late Glacial

Ongoing climate changes have a direct impact on forest growth; they also affect natural fire regimes, with further implications for forest composition. Understanding of how these will affect forests on decadal-to-centennial timescales is limited. Here we use reconstructions of past vegetation, fire regimes and climate during the Holocene to examine the relative importance of changes in climate and fire regimes for the abundance of key tree species in northeastern China. We reconstructed vegetation changes and fire regimes based on pollen and charcoal records from Gushantun peatland. We then used generalized linear modelling to investigate the impact of reconstructed changes in summer temperature, annual precipitation, background levels of fire, fire frequency and fire magnitude to identify the drivers of decadal-to-centennial changes in forest openness and composition. Changes in climate and fire regimes have independent impacts on the abundance of the key tree taxa. Climate variables are generally more important than fire variables in determining the abundance of individual taxa. Precipitation is the only determinant of forest openness, but summer temperature is more important than precipitation for individual tree taxa with warmer summers causing a decrease in cold-tolerant conifers and an increase in warmth-demanding broadleaved trees. Both background level and fire frequency have negative relationships with the abundance of most tree taxa; only Pinus increases as fire frequency increases. The magnitude of individual fires does not have a significant impact on species abundance on this timescale. Both climate and fire regime characteristics must be considered to understand changes in forest composition on the decadal-to-centennial timescale. There are differences, both in sign and magnitude, in the response of individual tree species to individual drivers.

Effects of climate-change scenarios on the distribution patterns of Castanea henryi.

Castanea henryi, with edible nuts and timber value, is a key tree species playing essential roles in China's subtropical forest ecosystems. However, natural and human perturbations have nearly depleted its wild populations. The study identified the dominant environmental variables enabling and limiting its distribution and predicted its suitable habitats and distribution. The 212 occurrence records covering the whole distribution range of C. henryi in China and nine main bioclimatic variables were selected for detailed analysis. We applied the maximum entropy model (MaxEnt) and QGIS to predict potentially suitable habitats under the current and four future climate-change scenarios. The limiting factors for distribution were accessed by Jackknife, percent contribution, and permutation importance. We found that the current distribution areas were concentrated in the typical subtropical zone, mainly Central and South China provinces. The modeling results indicated temperature as the critical determinant of distribution patterns, including mean temperature of the coldest quarter, isothermality, and mean diurnal range. Winter low temperature imposed an effective constraint on its spread. Moisture served as a secondary factor in species distribution, involving precipitation seasonality and annual precipitation. Under future climate-change scenarios, excellent habitats would expand and shift northwards, whereas range contraction would occur on the southern edge. Extreme climate change could bring notable range shrinkage. This study provided a basis for protecting the species' germplasm resources. The findings could guide the management, cultivation, and conservation of C. henryi, assisted by a proposed three-domain operation framework: preservation areas, loss areas, and new areas, each to be implemented using tailor-made strategies.

Growth rates and ages of some key tree species from subantarctic Auckland and Campbell Islands

Interspecific variation in tree growth rate and maximum age is central to understanding and predicting the dynamics of forest ecosystems. While there are abundant sources of this information for economically important New Zealand timber species and other common tree species, data for trees from subantarctic environments are almost entirely lacking. Here we present measurements of growth from Auckland and Campbell Islands for three species: Metrosideros umbellata (southern rātā; Myrtaceae, n = 1 site), a canopy dominant; Dracophyllum sp.

The FraDiv experiment: Biodiversity-ecosystem functioning research meets reforestation practice

European ash-rich forest ecosystems are transforming rapidly under the influence of ash dieback, putting many associated species at risk. Forest managers face the urgent challenge to deal with the loss of European ash (Fraxinus excelsior L.) as a key tree species to maintain species richness and ecosystem functioning. The project FraDivexp, located in Schleswig-Holstein, Germany, aims at counteracting detrimental effects of progressive ash decline by testing alternative tree species in a Biodiversity-Ecosystem Functioning (BEF) experiment along a hydrological gradient. Here, we provide insight into how a BEF-approach can be combined with silvicultural management practice to meet the needs for both ecological research and reforestation. At the same time, we present first data on the survival of the planted saplings.In winter 2019/2020, FraDivexp was established with autochthonous tree species considered potential substitutes for the functioning of ash. At 12 sites, plantations including Fraxinus excelsior, Acer platanoides L., Carpinus betulus L., Tilia cordata Mill. and Ulmus laevis Pall. were planted directly underneath the remains of collapsing forest canopies involving all monocultures, and all combinations of 2-, 4- and 5-species mixtures. One year after planting of 25,200 trees, total mortality was at 5% with U. laevis showing lowest mortality while establishment of A.platanoides was least successful. In this early phase of FraDivexp tree mortality was species-specific and driven by initial individual tree size, pH-values in the topsoil and canopy openness, while there was no effect associated with tree diversity. Analysis of further biotic factors showed high mortality of A.platanoides in areas with a high cover of Rubus spp. in the herb layer, indicating species-specific susceptibility to different site conditions. Overall, low mortality (compared to other BEF experiments on arable land) suggests an advantage of establishing a BEF experiment within an existing forest matrix. Simultaneously, this study shows that differences in environmental context dependency among species need to be considered more explicitly, when recommending management strategies. To ensure successful establishment of reforestations with substitute tree species is the first step to efficiently counteract the massive loss of ash trees with the aim of maintaining biodiversity and ecosystem functioning.