This review on current biotechnological methods in forestry for in vitro tissue cultures to define the effect of stress conditions on trees, concentrates on somatic embryogenesis. Callus tissue, the key product of somatic embryogenesis, grows over a tree wound under ex vitro conditions. Callus tissue can be used in research in areas such as pathogenic susceptibility at the embryonic level, effect of heavy metals, influence of low temperatures (cryopreservation), production of secondary metabolites and transformation of plants. Callus of arborescent plants can be induced in vitro by fungal elicitors to produce secondary metabolites for pharmaceutical and cosmetic industries and are strongly repellant to herbivores and can thus act to protect forests. Analyses of dual cultures demonstrated that callus tissue exposed to a pathogenic fungus responds by synthesizing low-molecular-mass proteins belonging to an immune protein class. Cryopreservation of embryonic callus tissue also has broad applications, e.g., for valuable plant genotypes in gene banks. Without strategies to protect forests against stress factors, forest ecosystems will degrade to the detriment of all life, including humans. In vitro biotechnological research using callus tissue contributes to progress in forestry and the disciplines of ecology, physiology, phytopathology, culture and selection of plants.

We present stationarity criteria for forest stands, and establish embodiments using a Norwegian empirical stand development model. The natural stationary states only slightly differ from the outcome of long-term simulations previously implemented using the same empirical model. Human interference in terms of diameter-limit cutting is introduced. Consequently, stationary states differing from the natural one appear. Standing volume, growth and monetary value appear low but the financial return rate may be significant. Volume yield and financial return clearly contradict each other, the former arising from harvesting large trees, the latter from frequent removal of small trees. An exponential tree size distribution does not appear to comply with the stationarity criterion.

Santalum album L. is a commercially important tree that yields essential oil of high medicinal value. Regeneration research through organogenesis and embryogenesis has been documented but no report depicts comparative ontogeny of directly differentiating shoot buds (SB) and somatic embryos (SE). In the present study aseptic seedling derived hypocotyl segments (HC) and hypocotyl + root junction (HC + R) were used to induce SBs and SEs, respectively. Ontogenic differences between the structures were confirmed using scanning electron microscopy and histological analysis. MS medium containing 6-benzyladenine or BA (2.5 µM) produced highest number of direct SB, while MS + BA (7.5 µM) proved suitable for higher frequency of SE differentiation. The differentiating structures attained growth when transferred to MS medium containing a combination of BA and α-naphthalene acetic acid or silver nitrate (AgNO₃). A combination of indole-3-butyric acid and silver nitrate (AgNO₃) in half-strength woody plant medium and lesser osmotic concentration (2% sucrose), induced rhizogenesis.

Pollen and trichome morphology of the genus Betula were evaluated from three main habitats in Iran using light and electron microscopy. Pollen types were identical and tri-porate; however, in terms of quantitative data, some differences were observed in exine (outside) wall thickness, length of polar axis and length of equatorial axis, possibly due to the environment. Pollen alone is insufficient to separate species of Iranian birch. Investigation of the trichome trait (small hairs or other outgrowths) revealed that birch species in Iran belong to: (1) Betula litwinowii Doluch. according to the low density of trichomes on the adaxial surface of the leaves and the lack of trichomes on the abaxial surface and many trichomes on the petioles; (2) Betula pendula Roth. due to the absence of trichomes on the adaxial surface and the low density of trichomes on the abaxial surface; and, (3) in the adaxial and abaxial surfaces of leaves and petioles, the trichomes had different types of pilose (long, soft hairs), and this strengthens the possibility of a different species or more likely a hybrid of B. pendula.

Serendipita indica (formerly known as Piriformospora indica), a root endophytic fungus, exhibits multiple functions in some agricultural, horticultural, and medicinal plant species. We studied colonization of the roots of Platycladus orientalis, a forest tree species, by S. indica to improve the quality of the seedlings in seedbeds and survival rates in sylviculture. At 20 days after inoculation, S. indica colonized the root cortex of P. orientalis seedlings. Root colonization by S. indica significantly increased net CO₂ assimilation, light use efficiency, and biomass accumulation by both roots and shoots, whereas it did not affect the biomass allocation between roots and shoots. In addition, the symbiosis significantly increased root total length, surface area, and volume. In view of the two specific traits of S. indica, i.e., axenic culture and wide colonization in plants, the fungus might be used for improving quality of P. orientalis seedlings and increasing their survival after transplanting.

The solution culture method was used to study the effect of increasing nitrogen on the growth and photosynthesis of poplar seedlings under 100 mmol L⁻¹ NaCl stress. I Increase in nitrogen reduced stomatal limitation of leaves under NaCl stress, improved utilization of CO₂ by mesophyll cells, enhanced photosynthetic carbon assimilation capacity, significantly alleviated saline damage of NaCl, and promoted the accumulation of aboveground and root biomass. I Increased nitrogen enhanced photochemical efficiency (Ф _PSII) and electron transport rates, relieved the reduction of maximum photochemical efficiency (F _v/F _m) under NaCl, and reduced the degree of photoinhibition caused by NaCl stress. Increased nitrogen applications reduced the proportion of energy dissipating in the form of ineffective heat energy and hence a greater proportion of light energy absorbed by leaves was allocated to photochemical reactions. Under treatment with increased nitrogen, the synergistic effect of heat dissipation and the xanthophyll cycle in the leaves effectively protected photosynthetic PSII and enhanced light energy utilization of leaves under NaCl stress. The increased nitrogen promoted photosynthetic electron supply and transport ability under NaCl stress evident in enhanced functioning of the oxygen-evolving complex on the electron donor side of PS II. It increased the ability of the receptor pool to accept electrons on the PSII electron acceptor side and improved the stability of thylakoid membranes under NaCl stress. Therefore, increasing nitrogen applications under NaCl stress can promote poplar growth by improving the efficiency of light energy utilization.

To elucidate the potential and sensitivity of γ-irradiation in Pongamia pinnata, the present study has been done by irradiating the air-dried seeds to different γ-irradiation doses (100 Gy, 200 Gy, 400 Gy and 600 Gy), using ⁶⁰Co source. Significant increase (p ≤ 0.05) in the germination, growth, and vigor was recorded under the 100 Gy treatment than the control set. The chlorophylla and total chlorophyll content (mg g⁻¹ FW) in the leaves of P. pinnata showed a significant decrease under the higher irradiation treatments (200 Gy, 400 Gy and 600 Gy). In contrast, chlorophyllb showed a radio-resistance up to 200 Gy dose, and above which its concentration declined significantly (p ≤ 0.05). Photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, and transpiration rate were stimulated by 100 Gy irradiation treatment and the higher doses inhibited these parameters. Antioxidant activity in the leaves of P. pinnata tended to increase after irradiation in a dose-dependent manner. All the plants under different treatments of γ-irradiation showed stimulation in production of proline, flavonoid, and phenolic content in comparision to the control. The findings of the present study showed that γ-irradiation treatment stimulates the secondary metabolite production (proline, flavonoid and phenolic) and favours faster growth of P. pinnata.

Climate change necessitates research into interactions between elevated carbon dioxide (CO₂) concentrations and drought on plant photosynthetic physiology. This study describes the physiological properties of Platycladus orientalis (Chinese thuja) and Quercus variabilis (Chinese cork oak) saplings cultivated through orthogonal treatments of four CO₂ concentrations combined with five soil volumetric water contents (SWC). It highlights the differences between the interactive effects from the treatments. Water stress had little effect on photosynthetic traits until the soil volumetric water contents exceeded 70–80 or 100%. Similar variations in carbon-13 isotope abundance (δ¹³C) of water soluble compounds (δ¹³C_WSC) extracted from leaves of two species have been observed. Whether soil volumetric water contents exceeded or fell below the water threshold values (70–80% of field capacity for P. orientalis and 100% of field capacity for Q. variabilis), instantaneous water use efficiency decreased. Elevated carbon dioxide could increase iWUE and enhance drought tolerance, depending on stimulating net photosynthetic rates and declining stomatal conductance and transpiration rates. Augmenting either drought, excess water, or ambient carbon dioxide could alleviate the physiological inhibition caused by the stresses described above.

Mistletoes are parasite plants growing on various tree species, taking nutrients from the host. Beneficial compounds of mistletoe were used in medicine and these mistletoes were commonly collected from oak species that were not well identified. We analyzed the nutritional value by measuring proximate and mineral components of Korean mistletoe (Viscum album var. coloratum) from various host trees. Carbohydrate was the most proximate component in both leaves and twigs followed crude protein, crude fiber, crude ash and crude fat. While the contents of the proximate components and minerals varied among hosts and between plant parts, leaves contained higher crude protein and ash, and more minerals except for magnesium than twigs, although no significant difference was found in mistletoe grown on Prunus mandshurica. There were significant differences of proximate and mineral contents depending on the host species. Mistletoe grown on Chaenomeles sinensis contained higher levels of carbohydrates, crude fat, crude ash, magnesium, calcium, sodium, iron, and zinc than mistletoe grown on other species. Mistletoe grown on P. mandshurica contained high mineral levels of potassium, copper and phosphorous. The nutritional value of mistletoes were greatly influenced by the host species but among the hosts, specific nutrients accumulated in leaves more than in twigs, and vice versa. Based on the analysis, Korean mistletoe contains relatively good quality of nutrients and has high potential for dietary supplements as well as for medicinal compounds.

Although Pinus sibirica and Pinus koraiensis are resistant to cold or low temperatures in the cold temperate regions of the northern hemisphere, the former has a stronger cold resistance. Research has been limited to the comparison of physiological responses of the two species to cold stress. In this study, 5-year-old seedlings of P. sibirica and P. koraiensis were subjected to six temperature treatments, [20 °C (control), 0 °C, − 20 °C, − 40 °C, − 60 °C, and − 80 °C], under different stress periods (6, 12, 24, and 48 h). The results showed that differences in each physiological index were significant between P. sibirica and P. koraiensis, except for the permeability of cell membranes, reactive oxygen species, proline and soluble proteins. An ANOVA test indicated that there were extreme differences among the temperatures for each index, stress time and temperature × time for most indices. All indices showed a similar trend for P. sibirica and P. koraiensis with decreasing temperature or the extension of stress time. Soluble sugars and proline increased at 0 to − 20 °C and then remained unchanged with temperature decline. Other indices showed an increase from 20 to − 20 °C, stable from − 20 to − 40 °C and a decrease from − 40 to − 80 °C. All the indices increased and then declined along with the prolonged cold stress time, except for the control. From 0 to − 40 °C, the permeability of cell membranes, relative conductivity, reactive oxygen species and malonaldehyde of P. koraiensis seedlings were higher than in P. sibirica, but superoxide dismutase, peroxidase, catalase activity and soluble sugars, proline, and soluble proteins content emerged as opposite. This study compared the physiological mechanism responses to cold stress between P. sibirica and P. koraiensis to provide the basis for the introduction, distribution, and genetic improvement of these coniferous species.

The selection of drought-tolerant plants is an important aspect of plant breeding. We studied physiological and biochemical mechanisms of different ploidies of Populus ussuriensis Kom. that relate to drought stress tolerance. We used a 5% (v/v) polyethylene glycol (PEG-6000) solution to simulate drought stress. We recorded leaf phenotypes including color, dry area and curl degree. We evaluated sequential variations in some drought stress tolerance-related physiological and biochemical indices and compared these among diploid clones (CK), triploid clones (T12) and tetraploid clones (F20). T12 leaves exhibited slightly more drought stress damage than CK and F20 leaves. CK leaves suffered the most severe drought stress damage. The physiological and biochemical indices of the different ploidies differed significantly 12 days after drought stress treatment. The activities of superoxide dismutase, peroxidase, catalase and proline in the triploid (T12) leaves were the highest. The relative electric conductivity and malondialdehyde content of T12 leaves were the lowest. The index values of F20 were between those of the diploid and triploid. In consideration of these results, the drought resistance of the three different ploidies of P. ussuriensis can be ranked as T12 > F20 > CK. We speculate that the gene expression patterns of polyploid clones of poplar will change after genome doubling and that some of the drought stress tolerance-related physiological and biochemical indices will be improved, resulting in greater drought tolerance of polyploid clones.

CBF/DREB proteins play a critical role in abiotic stress-mediated gene expression and represent attractive regulons for plant breeding programs. However, no study has been conducted for CBF/DREB protein-related genes in jujube (Ziziphus jujuba Mill.). In this study, twenty-five ZjDREB genes were identified and annotated from the jujube (Z. jujuba ‘Dongzao’) genome. Detailed analysis, including gene classification, annotation, phylogenetic evaluation, conserved motif determination and expression profiling were performed on all genes. Phylogenetic analysis showed that ZjDREB proteins were divided into five subgroups (A1–A5), but lacking a subgroup A6 corresponding to AtDREBs. The ZjDREB genes were distributed in nine of twelve chromosomes in the genome. Additionally, the expression patterns of the DREB genes under different abiotic stresses were investigated using qRT-PCR. Nineteen ZjDREB genes were down-regulated under low temperature, in contrast six ZjDREB genes (01, 03, 05, 11, 23 and 24) were up-regulated. Under drought, salinity and high temperature conditions, expression of ZjDREB03, 09, 10, 14, 15, 17 and 20 genes were induced and showed similar expression patterns, suggesting that various stress conditions share common elements in the signaling pathway. The results suggest that the family of DREB genes play an important role in abiotic stresses in jujube, and provide a foundation for further functional studies of this important class of transcriptional regulators.

RELATED TO AP2.12 (RAP2.12) is one of the Ethylene Response Factors (ERF) transcription factor and plays a key role in controlling plant root bending and responding to multiple abiotic stresses including hypoxia stress. In this study, FmRAP2.12 gene was isolated and characterized from Fraxinus mandshurica Rupr. The open reading frame (ORF) of FmRAP2.12 was 1170 bp and encoded a protein of 389 amino acids. The conserved domains, three-dimensional phylogenetic relationship of FmRAP2.12 was also investigated. Quantitative real-time (qRT-PCR) analyzed the expression of FmRAP2.12 in different tissues. The expression level of FmRAP2.12 was highest in roots followed by leaves, and lowest in male flowers. Abiotic stress and hormone signal-induced expression was established using qRT-PCR. Salt stress induced FmRAP2.12 to a double peak pattern: the first peak value was at 6 h and the second at 72 h. Drought stress also induced FmRAP2.12 to a double peak pattern: the first at 6 h and the second at 48 h. FmRAP2.12 was up-regulated after initiation of gibberellic acid (GA3) treatment, with a one peak pattern at 24 h. FmRAP2.12 may not respond to cold stress and Abscisic acid (ABA) treatment. The transient overexpression of FmRAP2.12 caused the up-expression of downstream key genes of abiotic stress response and gibberellin pathway. Our research reveals the molecular characteristic and expression patterns under abiotic stress and hormone condition of FmRAP2.12, providing support for the genetic improvement of F. mandshurica at a molecular level.

Syringa species are important ornamentals with strong floral scent, of which monoterpenes are the main component. In this study, a new monoterpene synthase gene, named SoLIM, was collected from the flowers of Syringa oblata and S. oblata var. alba using a homologous cloning method. The full-length cDNA of SoLIM was 1746 bp and encoded 581 amino acids. Sequence analysis showed that SoLIM contained the DDxxD and RRx₈W motifs, which are two typical conserved monoterpene synthase motifs, and was thus classified as belonging to the Tpsb subfamily. Using quantitative reverse-transcription PCR, SoLIM was significantly expressed in the petals and pistils of S. oblata and S. oblata var. alba, respectively. SoLIM expression peaked earlier than the D-limonene emissions in the diurnal experiments, but occurred later when D-limonene had peaked during the flowering phase, indicating that differences in SoLIM gene expression and D-limonene emissions existed. The synthesis of floral scent is thus associated with diverse regulatory mechanisms that require further investigation.

Variations in the phenotypic characteristics of conifer needles is a consequence of genetic evolution that has been widely used in geographic variation and ecological studies. Although many studies are based on an in situ sampling strategy and generally realize the contribution of environmental effects to variation in needle traits, it is still uncertain which needle traits are most influenced by genetic effects and which are most influenced by the environment. Using both a common garden experiment to eliminate environmental heterogeneity and an in situ sampling strategy, we compared 18 Pinus tabuliformis needle traits among 10 geographical populations. Using both sampling strategies, we found significant differences in needle traits among populations and among individuals within populations. Differences in the “among-population” variance component between the two sampling strategies revealed the environmental contribution among natural populations for each trait. The among-population variance in the following traits exceeded 8%: needle length, number of stomata within 2 mm (NS2), number of stomatal lines on the planar side, number of resin canals (RCN) and the resin canal area (RCA). For the stability of needle traits, NS2, RCN, RCA, ratio of the vascular bundle area to the RCA (VBA/RCA), and MA/RCA differed significantly in more than five provenance changes between the common garden populations and natural populations, which may be susceptible to environmental effects. Conversely, the cross-sectional area, mesophyll area (MA), MA/(VBA + RCA), and MA/VBA were phenotypically stable. Geographic variation patterns and systematic relation of needle traits differed between the two sampling strategies, suggesting that in situ sampling results may reflect environmental effects and deviate statistical parameters for genetic study. Future studies of genetic evolution in the context of geographic variation should be based on appropriate sampling strategies and stable phenotypic traits.

To achieve germplasm innovation and study genetic variation of important traits of bamboo plants, we used Bambusa multiplex, B. chungii, and Dendrocalamus latiflorus as parent materials for distant and inbred hybridizations. Two hybrid populations and three inbred populations were obtained: two populations consisted of 57 hybrid progenies from B. multiplex ×  B. chungii, 26 hybrid progenies from B. multiplex ×  D. latiflorus, and three inbred progenies were from B. multiplex, B. chungii, and D. latiflorus. Traits for growth, morphology, and fiber were examined from the five populations when plants were 3 years old. Two hybrid populations had significant growth advantages in terms of height, diameter at ground level and internodal length. In terms of variability in morphological traits, the two hybrid populations followed the same trend, namely, seven morphological traits showed phenotypes that were intermediate to those of their parents; three morphological traits showed strong maternal effects, and three other morphological traits showed strong paternal effects. Among the five populations, the two hybrid populations had high arithmetic average fiber length, length-weighted average fiber length and mass-weighted average fiber length, moreover, extensive variations of these three traits were observed within these two hybrid populations. The establishment of distant hybrid populations from these three bamboo species increased the genetic diversity more than in the other species examined. This work provides excellent materials for breeding new varieties and lays the foundation for understanding the genetics of important traits by analyzing related functional genes.

Eremanthus erythropappus (DC.) MacLeish is an important forest species native to the Brazilian savanna biome, an environment with well-defined rainy and dry seasons. Its seeds are desiccation tolerant, non-dormant and dispersed at the end of dry season. This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed. This study evaluates if the damages caused by drying of germinating E. erythropappus seeds, at the stage when they have lost desiccation tolerance, are lethal. The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated. Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion (approximately 72 h) when the radicle had root hairs, a possible indicator of sensitivity to desiccation. Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope. Root hairs disappeared after drying, reappearing after pre-humidification, possibly an attempt to increase the surface area of the radicle for water uptake. However, the hypocotyl-radicle axis became darkened, probably by antioxidant system failure, causing seed death.

Terminalia laxiflora Engl. & Diels. is an important indigenous and multi-purpose species in Ethiopia. However threatened due to low germination and its storage behavior is unknown. In this study, we aimed to (1) test pretreatments for breaking the dormancy of T. laxiflora seed and (2) determine its storage behavior. Seeds were subjected to four pretreatments such as soaking, scarification, high-temperature, and control. Experiments were done before storage and after 2 years of dry storage at cold temperature (− 10 °C) based on randomized design with four replicates. The first round of experimental results showed that T. laxiflora seeds with high temperature treatments at 78 °C for 10 min showed significantly higher germination percentage (80%). In the second round experiment, high-temperature treatment at 78 °C for 15 min, cold water soaking, high-temperature treatment at 78 °C for 10 min, hot water soaking, and high-temperature treatment at 78 °C for 5 min showed significantly higher germination percentage from the remaining treatments (75, 64, 58, 56, and 53%, respectively). To break the dormancy of T. laxiflora seed and attain good germination result, seeds should be pretreated with high-temperature at 78 °C for 10 min to test the initial germination before storage and should be pretreated with high-temperature (at 78 °C for 15, 10, or 5 min), soaked in cold, or hot water for 24 h to monitor the germination after storage. The two experiments show that T. laxiflora produces orthodox seed.

In tropical ecosystems, species with an impermeable seed coat, i.e. physical dormancy (PY), are large in number and their seed coat is considered to be an adaptive trait for species persistence and colonization. However, only little is known about their mechanisms for breaking dormancy. The objective of this study was to understand the importance of seed maturation site and burial location in determining the PY release of Senna auriculata. Freshly collected seeds of S. auriculata from Vellore and Coimbatore, Tamil Nadu, India, germinated to 11 ± 1.5% and 19 ± 2.5% respectively and remaining seeds did not imbibe water, thus had PY. Germination of seeds from both sites following hot-water treatment for 30 s and mechanical scarification increased significantly and seeds were able to germinate at a wide-range of temperatures (5–35 °C) both in light and darkness. When incubated at 15/60 °C for 3 months, dormancy release for seeds collected from Coimbatore (72%) was greater than seeds matured in Vellore (53%). Following 1 year of burial at three different locations, seeds from Coimbatore germinated to higher percentage than Vellore seeds at all locations. In particular, the higher temperature sites released dormancy to greater extent than the lower temperature site. Our results suggest that summer temperatures (> 60 °C) prevailing in the tropics provide appropriate cues for breaking PY, but this could be greatly affected by the initial state of seeds and the burial environment.

When conditions are similar, more water evaporates from forest plantations than herbaceous vegetation, thereby affecting hydrological fluxes and ion transport in the soil. The vertical distribution of CaCO₃ and Cl⁻ ions shifts due to afforestation. The effect of groundwater depth and clay content were studied in the Great Hungarian Plain where forest area has been increasing for decades by analyzing soil and groundwater samples from stands of black locust (Robinia pseudoacacia, 11 plots) and poplar (Populus spp., 11 plots). All study sites contained one herbaceous (control) and one or more forested plots. CaCO₃ and Cl⁻ ions accumulated in the soil profile in greater quantities under tree cover than in the controls. The scale of this process largely depended on the species and on soil and ion properties. Under black locust, Cl⁻ accumulated between 1.3 and 6.3 m, with a maximum difference of 0.3 pCl unit (pCl is Cl⁻ activity, the negative of the logarithm to base 10 of the concentration of the chloride ion, determined using an ion-selective electrode, it is a dimensionless quantity.), while the difference in CaCO₃ accumulation was at most 3.5% in some layers, compared to control plots. This result may be explained by the difference in the mobility of Ca⁺ and Cl⁻ ions. Different mechanisms were noticeable under poplar plantations due to their higher water uptake: Cl⁻ accumulation was detected below 0.9 m to the groundwater with a maximum difference of 0.5 pCl units, while CaCO₃ accumulation was continuous at depths of 2.3–6.8 m with a maximum difference of 8.4%, compared to the controls. With increasing clay content, there was a discernible effect on CaCO₃ and Cl⁻ accumulation under black locust, but not observed under poplars. These differences were explained by the differences in water uptake mechanisms and root patterns of the two species and the different mobility of Ca²⁺ and Cl⁻ ions.

The purpose of this study was to evaluate the effects of Broussonetia papyrifera (paper mulberry) invasion and land use on the floristic composition of a dry semi-deciduous forest in Ghana. Forty-five plots (25 m × 25 m each), distributed among three land uses—selectively logged (SL); abandoned farmlands (AF); and an undisturbed reference (RF)—were surveyed. Results showed lower tree species richness (S), diversity (H′), evenness (S) and basal area (BA) in the SL (46, 0.78, 0.32 and 269.12 m² ha⁻¹, respectively) and AF (40, 0.53, 0.45, and 131.16 m² ha⁻¹) sites compared to the RF site (79, 2.66, 0.87, 963.72 m² ha⁻¹). Similar patterns were found at the shrub layer, but no differences were observed at the herb layer. Non-metric multidimensional scaling ordination revealed distinct species composition among the land uses. The two disturbed habitats, SL and AF, were associated with increased B. papyrifera invasion particularly in the overstory, with importance value index and mean relative density of 45 and 65.03%, and 42 and 53.29%, correspondingly. However, the species was only sparsely represented in the RF site. Tree density of B. papyrifera correlated negatively with H′, S, E, BA, and native tree density and richness. These findings highlight the strong link between human land use (i.e., logging and slash-and-burn farming), invasion, and vegetation characteristics, and suggest the need to limit these disturbances to conserve biodiversity within tropical forest ecosystems.

China’s 13th 5-year forestry plan explicitly requires the end of commercial harvesting and the improved management of natural forests by means of adjusting and optimizing forest structure and developing high-quality forest production. This requires the quantification of stand structure and species diversity. In this study, species distribution, association and size differentiation in a mixed broad-leaved/Korean pine (Pinus koraiensis Siebold & Zucc.) forest in Mudanfeng National Nature Reserve were analyzed using three spatial structure indices: uniform angle index, complete mingling index, and size differentiation index. The results show that the species were randomly distributed, with a moderate size differentiation and high mixed structure. Three dominant species exhibited different patterns in terms of the three indices and their bivariate distribution. Overall, Korean pine showed an opposite trend to Manchurian maple (Acer mandshuricum Maxim.), whereas the distribution pattern of Manchurian linden (Tilia mandshurica Rupr. & Maxim.) was similar to that of the entire stand. Our work contributes to further the knowledge of population structure in order to optimize the structure of secondary forests and plantations.

Snow damage on natural stands is an important problem concerning mountainous forest management. In the present research, the frequency and intensity of heavy snow damage on natural stands and the relationship of damages with characteristics of trees, stand and topography were studied in mountainous forests of northern Iran. A systematic sampling design was applied to the study area (140 ha), with 122 circular plots. The grid dimension was 100 m and each plot area was 1000 m². The four types of snow damage to trees include: crown damage (8.6%), stem breakage (5.4%), uprooting (3.2%), and bending (1.4%). The frequency of crown damage grew with an increase in the diameter at breast height (DBH), while the frequency of stem breakage, uprooting and bending decreased with an increase the DBH. The frequency of crown damage, stem breakage, and total damages was related to tree species (p < 0.01). Not all tree species were equally susceptible to snow damage. The amount of damage grew with increasing elevation and slope angle and decreased with increasing soil depth. Young trees (DBH < 25 cm) were more susceptible to snow damage than other trees. Snow damage decreased by as the trees in the stand became more mixed in age. The susceptibility of trees to snow damage increased by height and slenderness coefficient. With adequate silvicultural operation, snow damage can be reduced to a minimum level in these natural forests.

To understand the decomposition characteristics of Pinus massoniana foliar litter and the degradation of its refractory compounds in plantations under five canopy densities, a litter bag experiment over a decomposition time of 392 days was carried out. The results show that canopy density significantly affected decomposition rates of litter and degradation rate of lignin and cellulose. Litter decomposition rates decreased significantly with decreasing canopy density. Both lignin and cellulose degradation rates were lower with canopy densities of 0.62 and 0.74 as compared with the three other densities. Lignin and cellulose losses were more rapid in the first 118 days. Soil fauna had significant impacts on litter decomposition and the degradation of refractory compounds. Canopy density had significant effects on factors such as soil properties and soil fauna community structure, which could be conducive to the decomposition of litter and the degradation of litter recalcitrant components. Canopy density between 0.6 and 0.7 might be a favorable management practice promoting litter decomposition and beneficial for the sustainable development of P. massoniana plantations.

Kalam Kohistan is a dry, temperate hilly region in the Hindu Raj Series of the Greater Hindu Kush Mountains with diverse forests. As plant distribution and composition is expression of a range of various environmental variables, ecological and floristic attributes of vegetation in the Laikot Forests were therefore evaluated via consecutive explorative trips. These forests have not been evaluated ecologically before due to harsh climatic conditions and issues of accessibility and the study in hand is one of the first in its nature. Quantitative ecological techniques were used to sample forest vegetation and identify species in quadrats of 2 m × 2 m for herbs, 5 m × 5 m for shrubs and 10 m × 10 m for trees. All the data of 195 plant species and environmental factors were analyzed via Two-way Cluster Analysis and Canonical Correspondence Analysis using PCORD and CANOCO software. Among 195 plant species from 63 families were 27 species of Asteraceae, the most-speciose family, followed by Poaceae (20 spp.). The dominant life form was therophyte (86 spp.; 44% share), followed by phanerophyte (41 spp.; 21% share). For the leaf size spectrum, most prevalent was nanophyll (73 spp.; 44%) followed by microphyll (66 spp., 34%) and mesophyll (44 spp.; 23%). Calcium carbonate, pH, potassium, sand, silt, organic matter, slope aspect and grazing significantly influenced species composition, distribution and habitat. The floristic variation in the region was diverse due to elevational and aspect gradients and thus devided into three zones. This vegetation zonation can be utilized for forest management, species and habitat conservation. Both in situ and ex situ conservation of threatened plant species may improve their conservation status in future if address properly.

To understand soil N₂O fluxes from temperate forests in a climate-sensitive transitional zone, N₂O emissions from three temperate forest types (Pinus tabulaeformis, PTT; Pinus armandii, PAT; and Quercus aliena var. acuteserrata, QAT) were monitored using the static closed-chamber method from June 2013 to May 2015 in the Huoditang Forest region of the Qinling Mountains, China. The results showed that these three forest types acted as N₂O sources, releasing a mean combined level of 1.35 ± 0.56 kg N₂O ha⁻¹ a⁻¹, ranging from 0.98 ± 0.37 kg N₂O ha⁻¹ a⁻¹ in PAT to 1.67 ± 0.41 kg N₂O ha⁻¹ a⁻¹ in QAT. N₂O emission fluctuated seasonally, with highest levels during the summer for all three forest types. N₂O flux had a significantly positive correlation with soil temperature at a depth of 5 cm or in the water-filled pore space, where the correlation was stronger for temperature than for the water-filled pore space. N₂O flux was positively correlated with available soil nitrogen in QAT and PAT. Our results indicate that N₂O flux is mainly controlled by soil temperature in the temperate forest in the Qinling Mountains.

Forest structure and function are subject to risks of growth declines from intensified drought and frequent extreme events related to climate warming. Knowledge of tree growth declines will help anticipate future responses of forests to climate change. In this study, we investigated tree growth declines over the last four centuries in a juniper forest on the eastern Tibetan Plateau. By analyzing the radial growth trajectories of individual trees, we identified two events of intense growth decline, one in 1817–1830 and the other in 1969–1999 over the past four centuries. The intensity of the recent decline was unprecedented in the period under study. Ring-width chronology showed a positive correlation with self-calibrating Palmer Drought Severity Indices and a negative correlation with mean monthly temperatures in May and June. The recent intensified growth decline may have been due to temperature-induced frequent droughts in the study area. Our findings suggest that trees in this juniper forest may face a higher risk of growth decline and even mortality under continued climate warming.

Atmospheric pollution is an important concern in urban environments. The impact of urban pollution on the physiological, biochemical and anatomical properties of leaves of oriental plane (Platanus orientalis L.) was studied. The leaves were collected from an urban site (Tehran, Iran) and a non-urban forest park (Chitgar Forest Park). Anatomical (stomata, parenchyma, and cuticle) and physiological (chlorophyll content, enzyme activities) properties were analyzed. The concentrations of Cd (cadmium), Pb (lead), Ni (nickel), and Cr (chromium) in leaves were significantly higher and Zn (zinc) lower at the urban site relative to the forest park. Chlorophyll a, total chlorophyll, and carotenoid content in leaves of the urban site were significantly less than those of the forest park, but there was no significant difference in chlorophyll b. In addition, the activities of superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase in urban leaves were significantly higher than in the leaves of the forest park. In the urban area, leaves experienced a significant decrease in leaf surface area, stomata density, stomata pore area, epidermis, and spongy mesophyll thickness, but a significant increase in cuticle and palisade thicknesses relative to forest park leaves. The increase in enzyme activities may indicate that the trees are attempting to cope with increased reactive oxygen species (ROS) because of pollution-induced stress. Our study suggests that oriental plane trees alter their physiological and anatomical properties when living in a polluted urban environment.

Recent fires in Iran’s Zagros forests have inflicted heavy, extensive losses to the environment, forests, villages, and forest inhabitants, resulting in a huge financial loss to the country. With the increasing risk of fire and the resulting losses, it has become ever more necessary to design and develop efficient fire control and prediction procedures. The present study utilizes the Dong model to develop a map of areas vulnerable to fire in the Zarivar lake forests as a representative sample of Zagros forests. The model uses as its inputs some of the most significant factors (such as vegetation, physiographic features, and the human component) that affect the fire occurrence and spread. Having assigned weights to each factor based on the model, all maps were overlapped in the ArcMap and then the region was divided into five zones. The results showed that 74% of the region was located in three classes: highly vulnerable, vulnerable, and medially vulnerable. To validate the proposed zoning map it was compared with a map based on real data obtained from previous fires. The results showed that 81% of fire incidents were located in highly vulnerable, vulnerable and medially vulnerable zones. Furthermore, the findings indicated a medium to a high degree of fire vulnerability in Zarivar Lake forests.

Decreasing the forest ecosystem leaf-area index error (LAIe) helps accurately estimate the growth and light energy utilization of aboveground foliage. Analyzing light transmission in forest ecosystems can effectively determine LAIe. The LAI-2200 plant canopy analyzer (PCA) is used extensively for rapid field-effective LAI (LAIe) measurements and primarily to measure forest canopy LAIe values. However, sometimes this parameter must also be measured in forests with small clearings. In this study, we used the LAI-2200 PCA to obtain one A-value and four B-values each for the canopy, herbaceous layer, and forest ecosystem LAIe. Field measurements showed that the three LAIe types were obviously different. In certain quadrats, the average herbaceous layer (Dicranopteris dichotoma Bernh.) LAIe apparently exceeded that of the Pinus massoniana forest ecosystem. The sources of this error were measuring and recording A-value readings for small canopies and underestimating the ecosystem LAIe. We obtained similar coefficients of determination for both the pre-recomputation and post-recomputation of the canopy and forest ecosystem LAIe (R ² ≥ 0.96 and R ² ≥ 0.99, respectively); thus, the error was decreased. Measuring field LAIe with the LAI-2200 PCA and recomputation should compensate for LAIe underestimation in complex forest ecosystems.

We evaluated, for the first time in Turkey, the productivity of a feller buncher during clear-cut operations of two Brutian pine stands located in Canakkale, northwestern Turkey with different diameter classes and terrain conditions. In the first stand with 24.6 cm average DBH, the feller buncher cut full trees and moved them to roadside. In the second stand with 34.3 cm average DBH, the feller buncher cut trees in two stages due to their larger diameters and the relatively steep and rough terrain conditions of the site. The effects of specific stand features, DBH and tree height measurements were assessed through statistical analysis in relation to productivity. The results indicate that the average productivity for the first stand was about 118 m³ h⁻¹, while it was about 80 m³ h⁻¹ in the second stand. Even though tree diameter and volume were higher in the second stand, productivity decreased by 32.3% due to extra time spent on the two-stage cutting operation. The results revealed that harvesting operations should be planned carefully and the right equipment selected by accounting for different tree sizes, terrain conditions and machine specifications in order to better understand their effects on production.

To analyze the relationship between the management of three forest stand plantations and soil quality in the Dimapur district of the Northeastern Himalayan region, India, three forest soil profiles, covered by different species stands, at three depths were tested for 13 physical and chemical variables. Only four of these variables (electric conductivity, bulk density exchangeable Mg and available P) were included in a minimum data set, after using a varimax rotation algorithm in a principal component analysis, and subsequently used to calculate a soil quality index (SQI). Results showed higher SQIs in the surface layers (0–20 cm depth) than in the deeper ones. Average weighed SQI varied significantly (P < 0.05) through the three considered forest sites, with the lowest value at site FS3. These findings reveal that the approach used here is suitable for preliminary screening of the impact of a forestry species on soil, to aid in species selection and improve soil health for afforestation and reforestation projects.

Phyllostachys edulis plays an important role in maintaining carbon cycling. We examined the effects of soil properties on organic carbon content in a P. edulis forest on Dagang Mountain, Jiangxi Province, China. Based on correlation and stepwise multiple regression analyses, the effects of seven soil factors on organic carbon and their sensitivities to change were studied using path and sensitivity analyses. The results revealed differences in the interconnections and intensities of soil factors on organic carbon. Soil porosity, field capacity, and ammonium nitrogen levels were the main factors affecting organic carbon in the ecosystem. Soil porosity had a strong direct effect on organic carbon content and a strong indirect effect through field capacity. Field capacity and ammonium nitrogen levels mainly affected organic carbon directly. Field capacity, soil porosity, and ammonium nitrogen content, as well as bulk density, β-glucosidase activity, and invertase activity, were sensitive factors. Polyphenol oxidase activity was insensitive. Our study provides a theoretical basis for understanding the effects of soil factors on organic carbon, which can be utilised to improve P. edulis forest management strategies and promote carbon sequestration capacities.

Soil organic carbon (SOC) mineralization is closely related to carbon source or sink of terrestrial ecosystem. Natural stands of Larix olgensis on the Jincang forest farm, Jilin Province were selected to investigate the dynamics of SOC mineralization and its correlations with other soil properties in a young forest and mid-aged forest at soil depths of 0–10, > 10–20, > 20–40 and > 40–60 cm. The results showed that compared with a mid-aged forest, the SOC stock in the young forest was 32% higher. Potentially mineralizable soil carbon (C ₀) in the young forest was 1.1–2.5 g kg⁻¹, accounting for 5.5–8.1% of total SOC during the 105 days incubation period and 0.3–1.5 g kg⁻¹ in the mid-aged forest at different soil depths, occupying 2.8–3.4% of total SOC. There was a significant difference in C ₀ among the soil depths. The dynamics of the SOC mineralization was a good fit to a three-pool (labile, intermediate and stable) carbon decomposition kinetic model. The SOC decomposition rate for different stand ages and different soil depths reached high levels for the first 15 days. Correlation analysis revealed that the C ₀ was significantly positively related with SOC content, soil total N (TN) and readily available K (AK) concentration. The labile soil carbon pool was significantly related to SOC and TN concentration, and significantly negatively correlated with soil bulk density. The intermediate carbon pool was positively associated with TN and AK. The stable carbon pool had negative correlations with SOC, TN and AK.

Arbuscular mycorrhizal fungi (AMF) in the soil encompass a diversity of species and play an important role in maintaining ecosystem balance. However, little research has focused on the AMF diversity of Rosa acicularis Lindl. ‘Luhe’, which has been cultivated in northeastern saline areas, because of its strong salt tolerance and cold resistance. In the present study the AMF in the rhizosphere of R. acicularis Luhe were identified and AMF diversity and community composition were assessed using morphological and molecular techniques. Vesicles, hyphae, and arbuscular structures were observed in seedlings of different ages. Result shows that AMF established a good symbiotic relationship with R. acicularis Luhe. The colonization rate and spore density tended to increase over time. The AMF diversity in the rhizosphere of R. acicularis Luhe was low and four species of AMF were validated: Rhizophagus irregularis, Glomus aggregatum, Septoglomus furcatum, and Funneliformis mosseae. Of these, R. irregularis and G. aggregatum were dominant and have high salt tolerance. Determining the AMF diversity in the rhizosphere of R. acicularis Luhe will aid in screening AMF species with strong resistance and using mycorrhizas for plant establishment in breeding programs.

Arundinaria spanostachya is the main bamboo species on which giant pandas forage. Information on its regeneration capacity to meet the foraging demands of pandas is important to ensure the long-term survival of pandas. In 2014, 2 plot types (grazed versus control) were selected in the winter habitat used by one wild giant panda. Various morphological and regeneration characteristics of the bamboo were assessed in the respective plots during 2014 and 2015. The panda avoided feeding on bamboo with a basal diameter of < 6 mm, preferentially feeding on intermediate-sized bamboo. The density of new shoots and the recruitment rate of shoots were significantly higher in the grazed plots compared to the control plots. The annual recruitment rate of shoots was markedly higher than the annual mortality rate in the same plot type. After grazing, the basal diameter and height of new bamboo were similar between the 2 plots. In the grazed plots, the basal diameter of new bamboo was similar to that of the stumps. Innutrition and foraging by insects were the main factors influencing the survival of new shoots. Our results showed that grazing by giant pandas helped the clonal regeneration of A. spanostachya populations, with the basal diameter of new bamboo shoots meeting the foraging demand of pandas. However, information on the carrying capacity of A. spanostachya is necessary to ensure sufficient forage matter is available for reintroduced giant pandas. Furthermore, fertilization and insect control measures should be implemented during the shooting period to optimize A. spanostachya resources.

Glycerol stearate was synthesized by esterification with non-toxic, inexpensive glycerol and stearic acid. The composite of glycerol stearate and Pinus radiata wood was prepared by vacuum impregnation. By Fourier transform infrared (FTIR) analysis, there was the generation of new C=O stretching vibration band of glycerol stearate in comparison with stearic acid. This confirms that glycerol stearate was successfully synthesized. The weight gain, FTIR spectrum and morphological analyses of the composite indicate that glycerol stearate was impregnated into the interior lumina of the cells. Thermal analysis showed that the maximal degradation temperature of the composite was 42 °C higher than untreated wood. Contact angle images indicated that the value of the composite was 134.2°. Hydrophobicity (the repulsion of water) of the composite was stronger than glycerol stearate, which a large number of hydroxyl of wood reacted with the oxygen-containing groups of glycerol stearate, improved hydrophobicity and thermal stability, thereby enhancing the potential application of P. radiata wood.

In this study, an image binarization optimization algorithm, based on local threshold algorithms, is proposed because global and traditional local threshold segmentation algorithms cannot effectively address the problems of non-uniform backgrounds of wood defect images. The proposed algorithm calculates the threshold by the mean, standard deviation and the extreme value of the window. The results indicate that this modified algorithm enhances the image segmentation for wood defect images on a complex background, which is much superior to the global threshold algorithm and the Bernsen algorithm, and slightly better than the Niblack algorithm and Sauvola algorithm. Compared with similar models, the algorithm proposed in this paper has higher segmentation accuracy, as high as 92.6% for wood defect images with a complex background.

Pinus patula is a species commonly used for reforestation in Mexico. However, efficient methods for the mass production seedlings are required. Micropropagation particularly by somatic embryogenesis provides an option for the rapid multiplication of high-quality, genetically improved material. This study induces somatic embryogenesis in this species using the thin cell layer (TCL) technique. Two sources of explants (complete immature embryos; lTCL segments from immature embryos) were evaluated. The efficiency of TCL from longitudinal sections [lTCL] and transverse [tTCL] was evaluated. The results show using thin cell layers from immature embryos cultivated in 16 light/8 dark hours achieves induction of somatic embryos. A higher percentage of embryogenic callus was obtained when tTCL segments were used as an explant source. These results produced somatic embryos from tTCL segments of an immature embryo without germinating the seed, making the process more time efficient. In addition, this technique can be used to generate somatic embryogenesis in forest species that have low germination rates.

The article “Forest pasturing of livestock in Norway: effects on spruce regeneration” written by Olav Hjeljord, Trond Histøl and Hilde Karine Wam was originally published Online First without open access.