Forest Tree Species Research Articles

Perceptions of commercial plants and tree nurseries in the use of native forest tree species for urban landscaping activities in municipalities of Los Baños and Bay, Philippines

Abstract Urban greening using native forest tree species (NFTs) has been increasingly recognized to achieve more livable, healthier, and resilient cities. However, despite having diverse genetic reserves, full utilization of NFTs in the country has not been fully realized. This restricts the mass production of seedlings for urban greening activities. As such, this study was carried out to determine the perceptions of commercial plants and tree nurseries in the use of NFTs for urban greening in municipalities of Los Baños and Bay, Philippines using the snowball sampling technique of Key Informant Interviews (KII). A total of 32 respondents were interviewed. Out of 85 species of trees identified, 51.16% (Los Baños) and 35.29% (Bay) were native. Most buyers planted their seedlings in private gardens (37.62%), subdivisions (12.38%), and private resorts (11.90%). About 18% of respondents sourced out their propagules from local sellers, followed by purchasing ready-to-plant seedlings from nearby towns (e.g. Talisay, Batangas) (14.11%) and Mt. Makiling Forest Reserve (10.58%). Unfamiliarity (21.69%) with the potential of native species seemingly impedes their popularity as urban trees. Over 23% of respondents believed that native trees help enhance the urban biodiversity and more than 43% have mentioned that buyers used leaves as the basis for species selection. Meanwhile, seedlings of seed origin are the most common (about 35%) mode of seedling production. Finally, the study revealed that Pterocarpus indicus is the topmost common native forest tree species being used for urban greening in the subject municipalities and therefore warranted to be used for further studies.

Variations in the leaf economics spectrum, anatomical, ultrastructural, and stomatal traits of five tree species in the urban-rural air pollution environment

Rapid urbanization has contributed to global increases in air pollution derived from urban areas. Unlike natural forests, urban forests are exposed to higher concentrations of airborne pollutants due to the strong urban-suburban-rural pollutant emission gradients. However, there remains a pressing lack of available information pertaining to the urban air pollution-related effects on the leaf economics spectrum, anatomical, ultrastructural, and stomatal traits of tree species along an urban-rural gradient. Here, the degree to which urban air pollution impacts the adaption of greening tree species and associated service functions was assessed by sampling five common tree species (Acer pictum, Fraxinus chinensis, Koelreuteria paniculata, Salix babylonica, Sophora japonica) along urban-rural-natural forests in the Beijing metropolitan region of China. These analyses revealed a significant reduction in leaf mass per unit area (–13.4 %), leaf thickness (–16.7 %), and stomatal area (–27.5 %) with increasing proximity to areas of greater air pollution that coincide with significant increases in leaf tissue density (+12.6 %), leaf nitrogen content (+10.1 %), relative chlorophyll content (+2.7 %), and stomatal density (+11.9 %). Higher air pollution levels were associated with organelle changes including gradual disintegration of chloroplasts, larger intercellular spaces and apparent starch and plastoglobuli deposition. Air pollution was conducive to the strengthening of the trade-off potential and adaptation strategies of trees in urban ecosystems, which are associated with trees with a rapid investment return strategy associated with thick leaves and strong photosynthetic capacity. These results provide strong empirical evidence of the profound air pollution-induced changes in leaf functional traits and adaption ability of urban forest tree species.

Effects of climate change on seed germination may contribute to habitat homogenization in freshwater forested wetlands

Climate changes in temperate regions are expected to result in warmer, shorter winters in temperate latitudes. These changes may have consequences for germination of plant species that require a period of physiological dormancy. The effect of cold duration on seed germination has been investigated in a number of plant taxa, but has not been well studied in wetland and bottomland forest tree species, an ecosystem that is threatened by habitat homogenization. Our work sought to test the role of changing winter temperatures on seed germination in specialist (Nyssa aquatica and Taxodium distichum) and generalist (Acer rubrum and Liquidambar styraciflua) tree species within forested wetlands throughout the eastern U.S. The experiment was conducted in an environmental chamber in Norfolk, VA, USA. Seeds of T. distichum, N. aquatica, A. rubrum, and L. styraciflua were exposed to each of seven pre-germination cold exposure durations (0, 15, 30, 45, 60, 75, and 90 days) and observed for germination for 30 days. Cold stratification duration positively impacted total percent germination in N. aquatica (p < 0.0001) as well as A. rubrum (p = 0.0008) and T. distichum (p = 0.05). Liquidambar styraciflua seeds exhibited more rapid rates of germination with increasing cold exposure duration and greater percent germination compared to the others regardless of cold stratification duration. Our results provide insight into how community dynamics and biodiversity of wetland and bottomland trees may shift with a changing climate. Further, this work emphasizes the importance of understanding the role of plant functional traits in early life stages in community dynamics and has implications for management practices.

Effects of drought and moisture stress on the growth and ecophysiological traits of Schima superba seedlings.

Changes in rainfall patterns are important environmental factors affecting plant growth, especially when larger precipitation events and prolonged drought periods occur in subtropical regions. There are many studies on how drought reduces plant biomass through drought-sensitive functional traits, but how excess water affects plant growth and ecophysiology is still poorly understood. Therefore, a greenhouse experiment was conducted on Schima superba (Theaceae), a dominant tree species in subtropical forests and commonly used in forestry, in a closed chamber under control (25% soil water content (SWC) as in local forests), drought stress (D, 15% SWC) and moisture stress (W, 35% SWC). Plant growth and ecophysiological traits related to morphology, leaf gas exchange, water potential and structural traits were measured. Compared to control, S. suberba under dry conditions significantly decreased its aboveground biomass, photosynthetic rate (A), leaf water potential and nitrogen use efficiency, but increased intrinsic water use efficiency, root to shoot ratio and specific root length. S. superba under wet conditions also significantly decreased its total biomass, aboveground biomass and specific root length, while W had no effect on A and leaf water potential. Our results indicate that S. superba shows a decrease in carbon gain under drought stress, but less response under wet conditions. This emphasizes the need to consider the strength and frequency of rainfall pattern changes in future studies because rainfall may either alleviate or intensify the effects of drought stress depending on the moisture level, thus suitable water conditions is important for better management of this tree species in subtropical China.

Comparison of Algorithms and Optimal Feature Combinations for Identifying Forest Type in Subtropical Forests Using GF-2 and UAV Multispectral Images

The composition and spatial distribution of tree species are pivotal for biodiversity conservation, ecosystem productivity, and carbon sequestration. However, the accurate classification of tree species in subtropical forests remains a formidable challenge due to their complex canopy structures and dense vegetation. This study addresses these challenges within the Jiangxi Lushan National Nature Reserve by leveraging high-resolution GF-2 remote sensing imagery and UAV multispectral images collected in 2018 and 2022. We extracted spectral, texture, vegetation indices, geometric, and topographic features to devise 12 classification schemes. Utilizing an object-oriented approach, we employed three machine learning algorithms—Random Forest (RF), k-Nearest Neighbor (KNN), and Classification and Regression Tree (CART)—to identify 12 forest types in these regions. Our findings indicate that all three algorithms were effective in identifying forest type in subtropical forests, and the optimal overall accuracy (OA) was more than 72%; RF outperformed KNN and CART; S12 based on feature selection was the optimal feature combination scheme; and the combination of RF and Scheme S12 (S12) yielded the highest classification accuracy, with OA and Kappa coefficients for 2018-RF-S12 of 90.33% and 0.82 and OA and Kappa coefficients for 2022-RF-S12 of 89.59% and 0.81. This study underscores the utility of combining multiple feature types and feature selection for enhanced forest type recognition, noting that topographic features significantly improved accuracy, whereas geometric features detracted from it. Altitude emerged as the most influential characteristic, alongside significant variables such as the Normalized Difference Greenness Index (NDVI) and the mean value of reflectance in the blue band of the GF-2 image (Mean_B). Species such as Masson pine, shrub, and moso bamboo were accurately classified, with the optimal F1-Scores surpassing 89.50%. Notably, a shift from single-species to mixed-species stands was observed over the study period, enhancing ecological diversity and stability. These results highlight the effectiveness of GF-2 imagery for refined, large-scale forest-type identification and dynamic diversity monitoring in complex subtropical forests.

Effect of Soil Fertility on the Growth Characteristics of Two Young Trees of the Neem Family

To select tree species suitable for growth under Chinese ephedra forests, this study set up three soil fertility treatments: pure sandy soil, V (sand): V (fertilizer) = 3:1, and V (sand): V (fertilizer) = 1:1, to investigate the effects of different soil fertility levels on the growth characteristics of two tree species, Azadirachta indica A. Juss (neem) and Melia azedarach (chinaberry). The results show that: (1) Under low light conditions and pure sandy soil, the height and basal diameter of neem significantly increased, while chinaberry showed a significant increase in height and basal diameter under the V (sand): V (fertilizer) = 1:1 condition. (2) Under the V (sand): V (fertilizer) = 1:1 condition, both neem and chinaberry exhibited maximum leaf growth characteristics, while there was a decreasing trend under the V (sand): V (fertilizer) = 3:1 condition. These results indicate that neem is more suitable for growth in pure sandy soil and is more tolerant to poor soil conditions, while chinaberry thrives under the V (sand): V (fertilizer) = 1:1 condition. This preliminary selection provides a theoretical basis for the initial screening of tree species for coastal defense forests.

Ubiquity of methanogenic archaea in the trunk of coniferous and broadleaved tree species in a mountain forest.

Wetwood of living trees is a habitat of methanogenic archaea, but the ubiquity of methanogenic archaea in the trunk of various trees has not been revealed. The present study analysed methanogenic archaeal communities inside coniferous and broadleaved trees in a cold temperate mountain forest by culture-dependent or independent techniques. Heartwood and sapwood segments were obtained from the trunk of seven tree species, Cryptomeria japonica, Quercus crispula, Fraxinus mandshurica, Acer pictum, Aesculus turbinata, Magnolia obovata, and Populus tremula. Amplicon sequencing analysis of 16S rRNA genes showed that Methanobacteriaceae predominated the archaeal communities and Methanomassiliicoccaceae also inhabited some trees. Real-time PCR analysis detected methanogenic archaeal mcrA genes from all the tree species, with a maximum of 107copiesg-1 dry wood. Digital PCR analysis also detected mcrA genes derived from Methanobacterium spp. and Methanobrevibacter spp. from several samples, with a maximum of 105 and 104copiesg-1 dry wood. The enumeration by the most probable number method demonstrated the inhabitation of viable methanogenic archaea inside the trees; 106cellsg-1 dry wood was enumerated from a heartwood sample of C. japonica. Methanogenic archaea related to Methanobacterium beijingense were cultivated from a heartwood sample of Q. crispula and F. mandshurica. The present study demonstrated that the inside of various trees is a common habitat for methanogenic archaeal communities and a potential source of methane in forest ecosystems.

Investigating Thresholds for Drought Resistance in Floodplain Forest Tree Species

Abstract Anthropogenic and climatic variables combine to alter river flow regimes worldwide, which can influence shifts in species composition. Exacerbation of drought events in southeastern United States floodplains may have varying impacts on survival and regeneration of high bottomland, low bottomland, and swamp forest species, causing distribution shifts between these forest types. We tested 7-month-old seedlings of the swamp species water tupelo (Nyssa aquatica), Ogeechee tupelo (Nyssa ogeche), and pop ash (Fraxinus caroliniana), and the low bottomland species overcup oak (Quercus lyrata) and water hickory (Carya aquatica) in a controlled experiment with increasing drought treatment. We compared timing to 95% mortality and determined lethal soil moisture thresholds for species. Swamp species were no more vulnerable to mortality under increasing drought than low bottomland hardwood species found in neighboring wet floodplain habitats, suggesting that duration of drought may not be a main driver of compositional shifts between these forests. Study Implications: Natural flows of river systems around the world have been altered by humans and a changing climate. Increased intensity of drought events can affect tree species growing adjacent to rivers and influence their ability to reproduce, thus changing the composition of floodplain forests. We tested the drought tolerance of three swamp species accustomed to frequent flooding and two low bottomland hardwood species accustomed to less frequent flooding to see which species might be more affected by drought. We observed no differences between these two groups, suggesting that greater flood tolerance may not imply greater drought intolerance.

Modern breeding methods in forestry aimed at preserving genetic diversity

This research is devoted to analysing the impact of modern breeding measures in forestry on the level of genetic diversity of forest tree species. It has been found that the main source of improved seed material for the genetic restoration of forests is base forest seed orchards. Aspects of the influence of determining factors – background pollination and the number of clones – on the indicators of genetic variability of progeny have been analysed in detail. The potential of background pollination in forest seed orchards in the context of a significant decrease in the effectiveness of breeding measures and a parallel increase in the level of genetic variability of progeny has been studied. An analysis of data on the minimum number of clones in seed orchards has been carried out based on the practical experience of other developed countries. The dynamics of clone variability in terms of fertility have been investigated. The potential impact of clonal selection on the genetic diversity of tree species, particularly in reducing it, has been identified. It has been confirmed that integrating the concept of family forestry, which involves the use of vegetative propagation techniques, into the breeding strategy significantly increases the level of genetic variability in progeny. The study has demonstrated that the multiple-population breeding system provides the optimal preconditions for synergising the process of long-term intensive breeding and preserving the gene pool of tree species. It has been determined that there is no negative impact on genetic diversity from implementing a complex of optimally planned breeding programs. At the same time, the potential for intensifying the quality of gene pool conservation in the process of forest ecosystem restoration through the use of improved seed material and clones in artificial orchards has been established. Special attention is given to the maintenance of ex situ – valuable genetic material in forest seed production facilities, including forest seed orchards, trial cultures, and clone archives of plus trees. Research has shown that the implementation of modern innovative solutions and scientific recommendations can minimise the loss of genetic diversity in forest tree species. The results can be applied in contemporary forestry breeding programs

Functional traits and ecological niches as correlates of the interspecific growth–mortality trade‐off among seedlings of 14 tropical tree species

Abstract The interspecific trade‐off between growth versus mortality rates of tree species is thought to be driven by functional biology and to contribute to species ecological niche differentiation. Yet, functional trait variation is often not strongly correlated with growth and mortality, and few studies have investigated the relationships of both traits and niches, specifically encompassing above and belowground resources, to the trade‐off itself. These relationships are particularly relevant for seedlings, which must often survive resource limitation to reach larger size classes. We investigated the functional basis of the interspecific growth–mortality trade‐off and its relationship with ecological niches for seedlings of 14 tree species in a tropical forest in southwest China. We found evidence for an interspecific growth–mortality trade‐off at the seedling stage using 15 functional traits and 15 ecological niche variables. None of the organ‐level traits correlated with growth, mortality, nor the trade‐off, whereas specific stem length (SSL), a biomass allocation trait, was the only trait to have a significant correlation (positive). Moreover, light‐defined niches were not correlated with growth, mortality or the trade‐off, but soil‐defined niches did. Species at the faster growth/higher mortality end of the trade‐off were associated with higher fertility defined by lower soil bulk density and slope, and higher soil organic matter concentration and soil total nitrogen. Our findings indicate the importance of stem elongation and soil fertility for growth, mortality and their trade‐off at the seedling stage in this Asian tropical forest. Our findings contrast with analogous studies in neotropical forests showing the importance of photosynthesis‐related leaf traits related to insolation. Therefore, the functional drivers of demographic rates and trade‐offs, as well as their consequences for ecological niches, can vary among forests, likely owing to differences in biogeography, canopy disturbance rates, topography and soil properties. Moreover, the effects of functional trait variation on demographic rates and trade‐offs may be better revealed when biomass allocation is accounted for in a whole‐plant context. Read the free Plain Language Summary for this article on the Journal blog.

Runs of homozygosity reveal contrasting histories of inbreeding across global lineages of the edible porcini mushroom, Boletus edulis.

Inbreeding, the mating of individuals that are related through common ancestry, is of central importance in evolutionary and conservation biology due to its impacts on individual fitness and population dynamics. However, while advanced genomic approaches have revolutionised the study of inbreeding in animals, genomic studies of inbreeding are rare in plants and lacking in fungi. We investigated global patterns of inbreeding in the prized edible porcini mushroom Boletus edulis using 225 whole genomes from seven lineages distributed across the northern hemisphere. Genomic inbreeding was quantified using runs of homozygosity (ROHs). We found appreciable variation both among and within lineages, with some individuals having over 20% of their genomes in ROHs. Much of this variation could be explained by a combination of elevation and latitude, and to a lesser extent by predicted habitat suitability during the last glacial maximum. In line with this, the majority of ROHs were short, reflecting ancient common ancestry dating back approximately 200-1700 generations ago, while longer ROHs indicative of recent common ancestry (less than approximately 50 generations ago) were infrequent. Our study reveals the inbreeding legacy of major climatic events in a widely distributed forest mutualist, aligning with prevailing theories and empirical studies of the impacts of historical glaciation events on the dominant forest tree species of the northern hemisphere.

Temporal Transferability of Tree Species Classification in Temperate Forests with Sentinel-2 Time Series

Detailed information on forest tree species is crucial to inform management and policy and support environmental and ecological research. Sentinel-2 imagery is useful for obtaining spatially explicit and frequent information on forest tree species due to its suitable spatial, spectral, and temporal resolutions. However, classification workflows often do not generalise well to time periods that are not seen by the model during the calibration phase. This study investigates the temporal transferability of dominant tree species classification. To this end, the Random Forest, Support Vector Machine, and Multilayer Perceptron algorithms were used to classify five tree species in Flanders (Belgium) with regularly spaced Sentinel-2 time series from 2018 to 2022. Cross-year single-year input scenarios were compared with same-year single-year input scenarios to quantify the temporal transferability of the five evaluated years. This resulted in a decrease in overall accuracy between 2.30 and 14.92 percentage points depending on the algorithm and evaluated year. Moreover, our results indicate that the cross-year classification performance could be improved by using multi-year training data, reducing the drop in overall accuracy. In some cases, gains in overall accuracy were even observed. This study highlights the importance of including interannual spectral variability during the training stage of tree species classification models to improve their ability to generalise in time.

Impact of extreme pre-monsoon drought on xylogenesis and intra-annual radial increments of two tree species in a tropical montane evergreen broad-leaved forest, southwest China.

Tropical montane evergreen broad-leaved forests cover the majority of forest areas and have high carbon storage in Xishuangbanna, southwest China. However, stem radial growth dynamics and their correlations with climate factors have never been analyzed in this forest type. By combining bi-weekly microcoring and high-resolution dendrometer measurements, we monitored xylogenesis and stem radius variations of the deciduous species Betula alnoides Buch.-Ham. ex D. Don and the evergreen species Schima wallichii (DC.) Korth. We analyzed the relationships between weekly climate variables prior to sampling and the enlarging zone width or wall-thickening zone width, as well as weekly radial increments and climate factors during two consecutive years (2020 to 2021) showing contrasting hydrothermal conditions in the pre-monsoon season. In the year 2020, which was characterized by a warmer and drier pre-monsoon season, the onset of xylogenesis and radial increments of B. alnoides and S. wallichii were delayed by three months and one month, respectively, compared with the year 2021. In 2020, xylem formation and radial increments were significantly reduced for B. alnoides, but not for S. wallichii. The thickness of enlarging zone and wall-thickening zone in S. wallichii were positively correlated with relative humidity, and minimum and mean air temperature, but were negatively correlated with vapor pressure deficit during 2020 to 2021. The radial increments of both species showed significant positive correlations with precipitation and relative humidity, and negative correlations with vapor pressure deficit and maximum air temperature during two years. Our findings reveal that drier pre-monsoon conditions strongly delay growth initiation and reduce stem radial growth, providing deep insights to understand tree growth and carbon sequestration potential in tropical forests under a predicted increase in frequent drought events.

Possible changes of Pinus nigra distribution regions in Türkiye with the impacts of global climate change

Global climate change poses significant threats to ecosystems worldwide, particularly impacting long-lived forest tree species such as Pinus nigra. This study assessed the potential shifts in distribution areas for Pinus nigra, an important tree species, one highly vulnerable to global climate change, given its prevalence in continental climates, in Türkiye under different climate scenarios (SSPs 585 and 245). In this study, suitable distribution regions of Pinus nigra were evaluated based on SSPs 585 and SSPs 245 using nine different models. Results indicated potential losses in Pinus nigra distribution areas ranging from 15.0% to 43.5% (SSPs 245) and 19.7% to 48.9% (SSPs 585) by 2100. However, in 2100, new suitable distribution areas are expected to be formed at rates ranging from 13.8% to 32.1% and 15.1% to 34.4% according to the above scenarios. Because most of the newly formed suitable distribution regions are quite far from the areas where the species currently spreads, it seems necessary to provide the migration mechanism needed by the species by humans to prevent population losses in this process.

Balancing Risks and Benefits: Stakeholder Perspective on Managing Non-Native Tree Species in the European Alpine Space

For centuries, non-native tree (NNT) species have been planted throughout Europe for ecosystem services including timber and urban greenery. Public interest in NNTs has recently increased due to their potential role in climate change adaptation as alternatives to vulnerable native forest tree species. However, opinions regarding the benefits and risks of European NNTs differ. Understanding stakeholder perceptions is crucial for guiding adaptive forest management, especially in sensitive ecosystems like the European Alpine Space. To assess awareness and perception, a structured questionnaire was administered to 456 respondents from six countries in the European Alpine Space. Most respondents were aware of the origin of native and NNT species in their area. NNTs and invasive-NNTs were primarily found in urban regions, with a perceived increase in their occurrence over the past 25 years. With some exceptions, such as Pseudotsuga menziesii (Mirb.) Franco, the most common NNTs were generally perceived as potentially invasive. The perception of the invasiveness of NNTs correlated with their perceived risks and benefits on ecosystem services. The respondents who were unconcerned about invasiveness believed NNTs had a positive impact on provisioning services like timber, while those concerned about invasiveness perceived their negative effects on regulating cultural ecosystem services such as native biodiversity and landscape aesthetics. Overall, most respondents were conservative, opposing the promotion of NNTs, even in biodiversity-poor areas. Most stakeholders also believe that NNT regulations should prioritize their sustainable use and management rather than focusing solely on an invasive-centric narrative.

Mapping Characteristics in Vaccinium uliginosum Populations Predicted Using Filtered Machine Learning Modeling

Bog bilberry (Vaccinium uliginosum L.) is considered a highly valued non-wood forest product (NWFP) species with edible and medicinal uses in East Asia. It grows in the northeastern forests of China, where stand attributes and structure jointly determine its population characteristics and individuals’ growth. Mapping the regional distributions of its population characteristics can be beneficial in the management of its natural resources, and this mapping should be predicted using machine learning modeling to obtain accurate results. In this study, a total of 60 stands were randomly chosen and screened to investigate natural bog bilberry populations in the eastern mountains of Heilongjiang and Jilin provinces in northeastern China. Individual height, canopy cover area, and fresh weight all increased in stands at higher latitudes, and shoot height was also higher in the eastern stands. The rootstock grove density showed a polynomial quadratic distribution pattern along increasing topographical gradients, resulting in a minimum density of 0.43–0.52 groves m−2 in stands in the southern part (44.3016° N, 129.4558° E) of Heilongjiang. Multivariate linear regression indicated that the bog bilberry density was depressed by host forest tree species diversity; this was assessed using both the Simpson and Shannon–Wiener indices, which also showed polynomial quadratic distribution patterns (with a modeling minimum of 0.27 and a maximum of 1.21, respectively) in response to the increase in latitude. Structural equation models identified positive contributions of tree diameter at breast height and latitude to shoot height and a negative contribution of longitude to the bog bilberry canopy area. Random forest modeling indicated that dense populations with heavy individuals were distributed in eastern Heilongjiang, and large-canopy individuals were distributed in Mudanjiang and Tonghua. In conclusion, bog bilberry populations showed better attributes in northeastern stands where host forest trees had low species diversity, but the dominant species had strong trunks.

Are plant traits drivers of endophytic communities in seasonally flooded tropical forests?

In the Amazon basin, seasonally flooded (SF) forests offer varying water constraints, providing an excellent way to investigate the role of habitat selection on microbial communities within plants. However, variations in the microbial community among host plants cannot solely be attributed to environmental factors, and how plant traits contribute to microbial assemblages remains an open question. We described leaf- and root-associated microbial communities using ITS2 and 16 S high-throughput sequencing and investigated the stochastic-deterministic balance shaping these community assemblies using two null models. Plant ecophysiological functioning was evaluated by focusing on 10 leaf and root traits in 72 seedlings, belonging to seven tropical SF tree species in French Guiana. We then analyzed how root and leaf traits drove the assembly of endophytic communities. While both stochastic and deterministic processes governed the endophyte assembly in the leaves and roots, stochasticity prevailed. Discrepancies were found between fungi and bacteria, highlighting that these microorganisms have distinct ecological strategies within plants. Traits, especially leaf traits, host species and spatial predictors better explained diversity than composition, but they were modest predictors overall. This study widens our knowledge about tree species in SF forests, a habitat sensitive to climate change, through the combined analyses of their associated microbial communities with functional traits. We emphasize the need to investigate other plant traits to better disentangle the drivers of the relationship between seedlings and their associated microbiomes, ultimately enhancing their adaptive capacities to climate change.

Photosynthetic Acclimation of Larch to the Coupled Effects of Light Intensity and Water Deficit in Regions with Changing Water Availability.

The impact of frequent water deficits on dominant tree species in boreal forests has received increased attention, particularly towards addressing the global climate change scenarios. However, the impacts of coupled light intensity and water deficit in the regeneration and growth of Larix gmelinii seedlings, a dominant species in China's boreal forests, are still unclear. We conducted a dual-factor controlled experiment with four light intensities (natural sunlight, 50% shading, 75% shading, and 90% shading) and three soil water conditions (80%, 60%, and 40% soil saturated water content). The results showed that the coupling of light and water has a significant effect on the growth and development of Larix gmelinii seedlings. In 40% of the saturated soil moisture content, net photosynthetic rate, transpiration rate, chlorophyll a, and total phenol-leaf were significantly lower than the same light conditions under 80% soil saturated water content. Under the coupling treatment of 60% soil saturated water content and 50% shading treatment, the plant height increment, net photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll a, and phenolic compound content were significantly higher than those of other coupling treatments; however, more than 75% shading inhibited photosynthetic parameters, chlorophyll a, total flavonoid-leaf, and total flavonoid-branch. Our results have important implications for forest management practices; they provide a scientific reference for the early growth of Larix gmelinii seedlings under the coupling of light and water and promote the survival and growth of seedlings.

Linkages between stem vulnerability curves and tree demography and their implications for plant physiological modeling.

Vulnerability curves (VCs) have been measured extensively to describe the differences in plant vulnerability to cavitation. Although the roles of hydraulic conductivity (Ks,max) and hydraulic safety (P50, embolism resistance), both of which are parameters of VCs ('sigmoidal' type), in tree demography have been evaluated across different forests, the direct linkages between VCs and tree demography are rarely explored. In this study, we combined measured VCs and plot data of 16 tree species in Panamanian seasonal tropical forests to investigate the connections between VCs and tree mortality, recruitment and growth. We found that the mortality and recruitment rates of evergreen species were most significantly positively correlated with P50. However, the mortality and recruitment rates of deciduous species only exhibited significant positive correlations with parameter a, which describes the steepness of VCs and indicates the sensitivity of conductivity loss with water potential decline, but is often neglected. These differences among evergreen and deciduous species may contribute to the poor performance of existing quantitative relationships (such as the fitting relationships for all 16 species) in capturing tree mortality and recruitment dynamics. Additionally, evergreen species presented a significant positive relationship between relative growth rate (RGR) and Ks,max, while deciduous species did not display such relationship. The RGR of both evergreen and deciduous species also displayed no significant correlations with P50 and a. Further analysis demonstrated that species with steeper VCs tended to have high mortality and recruitment rates, while species with flatter VCs were usually those with low mortality and recruitment rates. Our results highlight the important role of parameter a in tree demography, especially for deciduous species. Given that VC is a key component of plant hydraulic models, integrating measured VC rather than optimizing its parameters will help improve the ability to simulate and predict forest response to water availability.

The pivotal role of water potential in phenology and seed germination of Abies spectabilis in the western Himalayan treeline region

Abies spectabilis (East Himalayan Fir), a dominant timber-producing species in the Himalayas, plays a dynamic role in ecological balance and sustains various habitats across temperate to subalpine altitudes. Himalayan montane forests express signs of changes in the growth, regeneration, and population density of forest tree species due to ongoing climate change, including its upper distribution limit. The research was conducted at 30°11´02˝N and 79°39′36˝E, ranging from 3,100 to 3,500 m asl elevation in the treeline ecotone of western Himalaya. The study presents a comprehensive perspective on how water availability and its intricate interactions with climatic and ecological variables shape the dynamics of treeline ecosystems. The study’s phytosociological analysis of treeline sites revealed the complex interplay between species composition, adaptability, and regeneration potential. The eco-physiological aspects of water balance were thoroughly explored, underscoring how plants employ various strategies to cope with changing water availability. The soil moisture content ranged from 32.17 to 73.50%. The dynamic nature of water potential (pre-dawn (ΨPD) and mid-day (ΨMD)) across seasons and years reflects and varies between −0.13 and − 1.25 MPa, the species’ ability to adjust and manage water balance according to environmental shifts. Osmotic potential at full turgor varied from −0.72 to −1.77 MPa, these adjustments are crucial for key life cycle events of vegetative and reproductive phases of species. The strong correlation of water potential (Ψ) and phenophases emphasizes the importance of water status in regulating these vital processes. Furthermore, the study delved into the maturation and germination processes, highlighting the significance of Ψ and moisture content in seed development and germination success. The maximum germination of 46.33% was observed when the seed moisture content was 30.90 ± 3.11%. The observed correlations between cone characteristics and seed parameters indicate the existence of trade-offs that impact seed size, weight, and germination capacity, contributing to the overall fitness of the species.