The species boundary may be ambiguous for the genetic admixture and similar morphology in incipient species. The features are resulted from recent gene flow and large amounts of ancestral polymorphisms and may further challenge the taxonomy. Cycas sect. Asiorientales, composed of Cycas taitungensis and C. revoluta, mainly distributed in Taiwan and the Ryukyu Archipelagos, have recently diverged with reciprocal paraphyletic relationships. Previous evolutionary inferences were based on few genetic markers and incomprehensive population samplings, and the morphological comparisons were incomplete due to long-term taxonomy misunderstanding of C. taitungensis. This calls into question the taxonomy and population genetics between these two species. Here, we used genome-wide SNPs with comprehensive population samplings to infer the geographic mode of speciation by approximate Bayesian computation (ABC) in two species. The individual tree was reconstructed for species delimitation and gene flow inferences. The morphometrics of diagnostic traits was incorporated for taxonomy reappraisal. Overlapped morphological variations and undistinguished genetic clusters by continuous gene flow rejected the allopatric speciation. The individual tree further implied asymmetric gene flow from Taiwan to northern Ryukyu islands, possibly due to the transoceanic vegetative dispersal by the northward Kuroshio Current and long-distance pollen flow. The above evidence suggests that neither C. taitungensis nor C. revoluta is an independent, monophyletic lineage. According to the principle of priority in nomenclature, C. taitungensis should be treated as a synonym of C. revoluta.

Water use, water use efficiency and water use sustainability are challenging issues for expansion of Eucalyptus plantations around the world but in particular where climate change scenarios are projecting droughts and water scarcity. The fast-growing species have been negatively related to reduce water availability by social and environmental groups but also forest industry wonders about the impact of drier climates on productivity and the water sustainability of forest plantations. We evaluated growth, water use and water use efficiency response at canopy closure (3 to 4 years of age) of eight selected E.globulus, E.nitens and E. nitens x globulus (E.gloni) genotypes at 4 sites of contrasting climate (temperature & dry season length) and soil water holding capacity. Across sites and genotypes growth rate and water use ranged 35-70- m3/ha/yr and 350 to 900 mm ha-1. Despite specific genotype cases, our results showed similar water use vs productivity relationships for a single taxon (90 m3 of water per m3 of wood) but suggested large differences among taxas across sites. Also, our results suggest that hybrids may provide large productivity benefits but may need a more precise understanding on their physiological mechanisms. These results suggest that interesting opportunities exist for matching genotypes to sites in order to reduce environmental concerns on water resources use of Eucalyptus intensively managed plantations.

The impact of fire on dominant tree stands in boreal forests of eastern Siberia was analyzed using the normalized burn ratio (NBR) and its pre- versus post-fire difference (dNBR) applied to Landsat-8 (OLI). We preprocessed satellite data on burned plots for 2015–2021. In result, we present the classification of fire impact in relation to dominant tree stands and vegetation types in boreal forests of eastern Siberia. The dNBR of post-fire plots ranged widely (0.30–0.60) in homogeneous larch (Larix sibirica, L. gmelinii) forests, pine (Pinus sylvestris) forests, dark coniferous stands (Pinus sibirica, Abies sibirica, Picea obovata), sparse larch stands, and Siberian dwarf pine (Pinus pumila) stands. We quantified the proportions of low, moderate, and high fire severity (37%, 39%, and 24% of the total area burned, respectively) in dense tree stands. The proportions were varied to 30%, 57%, and 13%, respectively, for sparse stands and tundra vegetation dominated in the north of eastern Siberia. We estimated proportion of stand-replacement fires in eastern Siberia by 12–33% of total burned areas, depending on vegetation type and tree density.

Next, for post-fire areas of different disturbance level, we evaluated the dynamics of restoration processes through the ranges of anomalies in the surface temperature and the Normalized Difference Vegetation Index (NDVI). It is shown that the long-term dynamics of NDVI anomalies and average surface temperatures can indirectly characterize the post-fire state of vegetation and recovery. At the same time, it is necessary to take into account both the degree of fire impact and the type of dominant tree stand.

Some forest formations have adapted to regular pyrogenic impacts and, if the impact of fire does not exceed a certain limit, it does not entail any serious consequences for ecosystems. As a possible criterion for evaluating the effectiveness of forest fire services, prevention of the level of burnout beyond a certain standard can act. The previously known methodology for assessing the annual rate of permissible forest burnout (developed within the framework of the FLEG II - ENPI Vostok regional program in 2016) requires a detailed consideration of each forest site. This requires detailed data on specific sites, which makes it impossible to use data from the State Forest Register of the Russian Federation. Within the framework of the proposed study, a modified version of this technique is proposed. In this variant, the data of areas and stands on these areas are used. The key approach has also been preserved, when the age of felling (for the corresponding forest-forming breed) is taken as the basis for the period of the forest-forming process, taking into account the precautionary factor. At the same time, the division of territories by forest fire zones was carried out according to a simplified (in comparison with the original methodology) algorithm with the division of forest-occupied lands into three zones (4 in the original methodology). All reserve forests and young trees in operational forests are assigned to zone A. Other operational forests are assigned to zone B. All protective forests are assigned to zone C. The data obtained during the calculations help to determine the approximate area of fires for each region of Russia. This area can be taken as "normal", and based on it, evaluate various activities in the forest, for example, such as extinguishing forest fires, reforestation and others.

Monitoring live and dead fuels moisture content (LFMC and DFMC) dynamics plays a crucial role in wildfire management and prevention actions. In this study we estimate LFMC and DFMC across the 21^st century, considering the meteorological conditions derived from medium and high greenhouse gas emission scenarios (RCP 4.5 and 8.5) by selecting a representative subset of global and regional climate models combination. A stable atmospheric CO₂ concentration was also considered to assess possible CO₂ mitigation effects. We applied semi-mechanistic models to infer moisture content dynamics across 36 study sites located in peninsular Spain, which corresponds with monospecific stands of twelve tree species. Overall, our results indicate that both, live and dead fuels moisture content dynamics, are going to experience generalized declining trends in the coming decades. Furthermore, increases in the number of days per year when fuels moisture content falls below wildfire occurrence thresholds is going to extend fire seasons lengths. Besides we observe a significative CO₂ mitigation effect, is not enough to offset LFMC declining trends induced by climate change. Finally, results suggest that, in ecosystems where plant biomass is abundant enough to sustain a fire, moisture content of live fuels is going to be the main limiting factor for future large wildfire occurrence.

Forest productivity is closely related to how effectively woody plants utilize the most important environmental factors - light and moisture. Assessment of ecological plasticity of structural and functional traits in woody plants is necessary to predict the dynamics of forest communities in the changing natural environment and climate. In this study, needle xylem anatomical and hydraulic traits and their relationships with leaf CO₂/H₂O-gas exchange parameters were investigated in Scots pine (Pinus sylvestris L.) trees during natural reforestation after clear-cutting of boreal pine forest in Eastern Fennoscandia. We analyzed the effect of shading on needle structural and functional traits in Scots pine trees of the same age in a clear-cut site and under bilberry-type pine forest canopy in the middle taiga. The highest values of tracheid lumen diameter (D₉₅), number of tracheids per needle (T_num) and xylem area per needle (A_x), theoretical needle hydraulic conductivity (K_{th_n}) and theoretical leaf-specific hydraulic conductivity(K_{s_leaf}), stomatal conductance (g_s), rates of photosynthesis (A) and transpiration (E), number of stomata per unit needle area (N_st) and, on the contrary, the lowest values of photosynthetic water use efficiency (WUE_i, WUE) and plasticity (PI) of all structural and functional traits were noted in Scots pine trees growing in the clear-cut and getting sufficient amounts of light. At the same time, the values of theoretical needle xylem-specific hydraulic conductivity (K_{s_xylem}) were similar in habitats with high (clear-cut site), medium (shading in the clear-cut), and low (forest canopy) light levels. The features of the relationship between the hydraulic structure, photosynthetic capacity, and water use efficiency in Scots pine trees under different habitat conditions are discussed.

Eucalyptus is a fast-growing genus widely used in the forestry industry; however, in its early stages, plantations are susceptible to drought conditions, and it is common to find high mortality rates and loss of productivity. Therefore, the study analyzed the physiological response photosynthesis (An) and predawn leaf water potential (Ψ_PLWP)) and the change in carbon balance (C) in ten Eucalyptus genotypes exposed to different water deficits, with the hypothesis that it is possible to identify and differentiate genotypes with tolerance to drought. Therefore, ten one-year-old genotypes were used in greenhouse conditions and soil matric power (Ψs) was regulated in four levels: -0.03 MPa (control), -0.7 MPa (slight stress), - 1.5 MPa (moderate stress) and -2.5 MPa (chronic stress). In each Ψs, growth, An and Ψ_PLWP were considered, then Gross primary productivity (GPP) was estimated. We found a significant relationship between water deficit and physiological response (major deficit produced a reduction of An and Ψ_PLWP). E. nitens clones had a minor physiological variation and GPP maintained the same trend and proportionality between aerial and underground production. In contrast, two hybrids of E. nitens x E. globulus showed an immediate physiological change and variation of GPP, with increased underground production and stagnant aerial production. These results suggest that it is possible to differentiate genotypes with tolerance to water deficit early. This will allow genotype selection according to the climatic conditions of each site, minimizing mortality and optimizing the available water resource.

The argan tree (Argania spinosa (L.) Skeels) is an endemic species of Morocco, widely adapted to the arid and semi-arid climate of the southwest. Our research involves studying and characterizing some physiological and biochemical traits of argan tolerance to water stress. For this reason, we measured physiological parameters related to the water state (foliar water potential and relative water content of the leaves) and biochemical parameters involved in osmoregulation (proline, total proteins and total sugars) and photosynthesis (chlorophylls) in plants from four contrasting origins of argan tree (Bouizakarne, Agadir, Essaouira and Berkane) cultivated under water stress induced by cessation of irrigation. The results showed that the basic and minimal foliar water potential, relative water content as well as chlorophyll content significantly decreased in plants under severe water stress compared to control plants, whereas a significant accumulation of proline and total soluble sugars was noted in stressed plants. Nonetheless, inter-origin differences were recorded for some parameters studied. The study of water-stress-adaptive traits in argan tree can help to understand the tolerance mechanisms and discriminate between the most drought tolerant provenances in order to rehabilitate degraded argan forests.

Forest degradation has been accentuated in recent years by climate change and drought. This study consists of producing quality plants and understanding their ecophysiological behavior in the face of water stress. Plants of two broadleaves (Quercus suber, Ceratonia siliqua) and two conifers (Tetraclinis articulata, Cedrus atlantica) aged 6 months subjected to water stress. The basic (Ψb) and minimum (Ψm) leaf water potential ware measured and processed according to climatic factors for the 4 forest species. The results show that the leaf water potential in Quercus suber presents more negative values (-0.42 MPa) for basic leaf water potential and (-1.43 MPa) for minimum leaf water potential than the other forest species studied. While Cedrus atlantica presents the least negative values for minimum leaf water potential (-0.89 MPa). These results allowed us to define the species that is more resistant to water stress and climate change. However, they refer us to more general questions concerning the mechanisms of water use in forest plants.

Taxus baccata (European yew) is native to Greece, which hosts the most south-eastern populations of the species. It is a medically interesting conifer due to its tetracyclic diterpenes, the anti-cancer agent paclitaxel (taxol), being the most well-known. Yew trees with high content of paclitaxel (taxol) have been identified in the natural population of Mt. Cholomon in Greece. The micropropagation of these plus-trees is of high importance both for the establishment of future plantations and for the ex-situ conservation of this valuable germplasm. A total of 600 cuttings from top and side shoots were taken from 10 highly producing paclitaxel trees and treated with a rooting solution containing the plant hormone K-IBA at concentrations of 6000 ppm and 12000 ppm. Cuttings were placed in a greenhouse for rooting using a perlite and peat 2:1 rooting medium, under constant temperature and humidity conditions. After five months the evaluation of rooting success, showed that it varied between different genotypes (40%-100%), but was generally considerable (average success of 78.7%). The higher K-IBA concentration resulted in a better rooting success, only in 50% of the genotypes tested, however root length was deferentially affected, as use of the 12000 ppm concentration resulted in an average of 2.76 cm root length, compared to an average of 2.69 cm when the 6000 ppm concentration was used. Overall, high yielding paclitaxel (taxol) were successfully micropropagated and these results constitute to both ex-situ conservation and plantation establishment.