Since the rapid spread of the Asian chestnut gall wasp (ACGW) throughout south-east Europe in the last few years, the possibilities of its control have been increasingly investigated. Due to constraints in available suppression measures in forest stands, biological control is recognized as the most suitable action to lower the abundance of the new invasive pest. Torymus sinensis, as a specialized parasitoid chalcid wasp of ACGW, was introduced to suppress the pest in Italy in 2005, and later in Croatia, Hungary (2014) and Slovenia (2015). We investigated the native parasitoid complex associated with ACGW in Slovenia, Croatia and Hungary over 8 years of sampling. We found 41 species of native parasitoids, eight of which are the first records on ACGW in Europe, adding up to a total of 51 species known to parasitize ACGW. These findings represent a large complex of cynipid-parasitoid fauna. Moreover, the abundance of native parasitoid populations on ACGW have demonstrated a temporal surge between the invasion of a new alien host (ACGW) and the onset of its specialized parasitoid, T. sinensis. Our results indicate that the introduced parasitoid acts as a very successful biocontrol of ACGW, outcompeting native parasitoids. This outcome should be considered as beneficial through the maintenance of ecological balance in affected forest ecosystems.

We determined the response of tree community structure to logging disturbance and topography, and the patterns of tree-habitat associations in Tano Offin Forest Reserve, Ghana. We sampled trees in 27 20 m × 20 m plots randomly and equally distributed in three topographic habitats (slope, valley, and hilltop) in each of two forests: logged and unlogged. Two topographic features, altitude and degree of slope, were measured and related with species composition. Overall, there were significant effects of logging and topographic habitat and their interaction on species diversity and composition, with the unlogged forest and valley habitat supporting higher diversity. Tree diversity varied among the topographic habitats in the logged but not in the unlogged forest. There were topographic effects on abundance of individual species but not on tree community abundance and basal area. Logging and its interaction with topographic habitat showed significant effects on tree abundance and basal area. Some species were associated with specific topographic habitats or a combination in the logged and unlogged forests. However, the patterns of habitat associations of the species differed between the logged and unlogged forests.

The canopy of subtropical natural forests usually consists of several co-dominant populations (CDPs), which play a crucial role in forest structure, formation of the forest environment, and ecological function. However, little attention has been given to changes in spatial patterns in CDPs during natural succession. Cyclobalanopsis glauca (Thunb.) Oerst., Quercus variabilis Blume, and Pinus yunnanensis var. tenuifolia W.C. Cheng & Y.W. Law are canopy species that form CDPs in zonal forests along the Nanpan River in southwest China. We used the g(r) function and its bivariate distribution model, g ₁₂(r), which is based on distances between pairs of points, to explore the dynamics of the three CDP species with respect to distribution patterns and spatial correlations in two secondary forests (one 30-year-old forest [30-YF] and one 57-year-old forest [57-YF]). The following key results were obtained: (1) there was a clumped pattern in the 30-YF, but the intensity of aggregation varied among populations and life stages. The distribution pattern gradually shifted to become random with longer succession time (i.e., 30-YF vs. 57-YF), expansion of the observation scale (r = 0–20 m), and at later life stages. (2) Aside from the mid-sized C. glauca trees and large P. yunnanensis trees, the trees repulsed each other at certain scales (r = 0–2, 5–6, 11–12, 14–16 m) in the 30-YF. Almost all of the life stages in the CDPs were independently correlated. This independent correlation was exacerbated by a longer succession time. (3) An increase in life stages and longer succession also promoted independent changes in intraspecific correlations. (4) Intraspecific correlations were stronger than interspecific correlations. Our results showed that reducing exclusive competition is essential to coexistence in CDPs. Inter- and intra-specific repulsion may occur at the same time, but intraspecific repulsion was the main driving force behind the random distributions and independent correlations.

The development of the mining industry has led to the appearance in many parts of the world of vast technogenic territories from which toxic heavy metals enter the environment and food chains. Physical, chemical, and biological methods of cleaning industrial land due to technological complexity and high cost are relatively little used on a large scale. Natural forest overgrowth of mining sites and the removal of heavy metals by woody plants can be an effective form of recovery. Therefore, the study of this process is of significant scientific and practical interest. The analysis of the annual growth in height and width of the annual rings of the stem of Scots pine (Pinus sylvestris L.) in 2004–2019 was made on the territory of the Uchalinsky mining and processing plant (South Ural, Russia) contaminated with heavy metals. Relatively high concentrations of copper and zinc were found in soils, roots, bark, young shoots, comparable to exceeding the maximum allowable concentrations. Despite the spatial uniformity of the heavy metal content in the stands, the tree samples significantly differed in terms of annual growth. Results suggest that the lack of nutrients and not stress from exposure to heavy metals is the main reason for relatively low growth rates on slopes of industrial wastes. It was confirmed by studying the annual growth in height of the undergrowth in habitats with different soil cover conservation. The data prove the relatively high potential of Scots pine for the natural recovery of industrial lands polluted with heavy metals by mining enterprises.

Picea spp. are a prominent component of the boreal, montane, and sub-alpine forests in the Northern Hemisphere, and have substantial economic importance due to their high quality fibre. However, performance and wood properties of the genus have not been systematically evaluated in China. This study aimed to examine genetic variations in growth traits, phenology, and wood properties of 17 Picea species, (three from North America, two from Europe, and 12 from China), in response to specific climate factors using a randomized complete block design in a monsoonal, middle latitude area of China. Results show that all growth traits and wood properties significantly varied among species (P < 0.00). Of the 17 species examined, P. abies and P. pungens were the tallest with heights of 2.5 and 1.9 m at 9 years old, respectively, 90% and 50% greater than the average heights. Branch length, number, and angles of both P. abies and P. pungens were greater than those of the other species. Heights of P. glauca and P. omorika were 20–33% greater than the average. Fast-growing species had high quantities of first lateral branches and large top whorl branch lengths. The taller species exhibited greater tracheid lengths and average tracheid lengths to radial central diameter ratios (TL/R_D2), but smaller cell wall thicknesses to tracheid radial lumen diameter ratios (WT/R_D1), which is favorable for pulp production. Correlation analysis revealed that height and ring width had significant positive correlations with latitude but strongly negative correlations with longitude. Height was positively correlated with average annual rainfalls, but negative correlations with average yearly sunshine. Due to the increased average annual sunshine at the China test site relative to the seed source, species such as P. abies, P. pungens, P. glauca, and P. omorika from wet, humid areas performed better than native species. Considering similar temperatures, precipitation may be the main factor affecting growth, which is beneficial for predicting the extent of spruce expansion. These results should encourage further testing and provide reference information for future exotic species studies in this part of China.

Understanding the effects of disturbance on seed rain is critical to predict changes in forest species composition and diversity. Logging effects on seed rain in a mixed conifer-hardwood forest complex in southern Brazil were evaluated. One year of seed rain data were collected from a large-scale observational experiment in logged and protected forests and quantity and average seed size weighted by species abundance (CWM) were compared between old-growth and logged stands 55 years after logging activities. Using these data, variations in frequency of functional groups of species in the seed rain were examined to see if they could be attributed to logging. Results show that the number of seeds per trap was highly right-skewed, ranging from 13 to 12,788 seeds per trap in one year. Seed rain was affected by logging history, with seed traps in old-growth plots receiving significantly less seeds than traps in logged plots. All species included mean seed size weighted by species abundance were significantly smaller in logged than in old-growth forests. This difference persisted after the exclusion of Araucaria angustifolia, a large-seeded pioneer which was intensively logged, although the difference of seed size between the two forest classes was greatly reduced. Species abundance in the seed rain differed significantly from the established tree community, between logged and old-growth stands. The composition of the seed rain was much more variable than the composition of the established tree community and its points more scattered over the ordination space than the points corresponding to the protected forests. The number of collected seeds across different functional groups of species significantly differed between logged and old-growth plots. The seed rain of logged forests reflects their arrested succession as indicated by reduced abundance of functional groups such as pioneers, large seeded pioneers and Araucaria, as well as reduced functional diversity. Seed rain differences between logged and old- growth stands reflect the intensive logging of A. angustifolia.

Although important, phenological studies comparing congeneric species or the same species growing in different habitats are still scarce for the tropics. Herein, we integrate phylogeny, ecology and biometeorology to verify whether the phenophases of congeneric species Myrcia laruotteana and Myrcia amazonica or Clethra scabra differ when their populations inhabit wetland and drained habitats and to determine what abiotic factors affect the vegetative and reproductive phenophases of these species in distinct habitat patches. We collected data on phenological events of 80 trees for 1 year in Itacolomi State Park, Brazil, and related them to abiotic local factors. Contrary to our expectation, the phenophases of the congeneric species did not differ between habitats, but the reproductive phenophases of C. scabra did and was greater in drained soil. Phenophases of C. scabra were affected by the depth of the water table and maximum temperature in the wetland soil. Insolation, precipitation, maximum temperature and relative humidity influenced Myrcia and Clethra in the drained soil. The differences between C. scabra populations suggest that this species is phenotypically plastic and can present distinct phenophases depending on the habitat it inhabits. On the other hand, the congeneric Myrcia species may have similar phenophases in distinct habitats because of their shared similarities during their evolution. This study provides a better understanding of the ecology of these species and their adaptations to different abiotic conditions. Data of this nature are important in a changing world and can inform strategies for adaptive management.

Foliar C/N stoichiometry is an indicator of geochemical cycling in forest ecosystems, but the driving changes for its response to urbanization at the wide scale is not clear. In this study, data on tree-leaf C and N stoichiometry were collected in papers from across 105 tree species from 82 genera and 46 families. The foliar C/N of urban forest trees varied among different climate zones and tree taxonomic variation and tended to be higher in trees of urban forests near the equator and in eastern regions, mainly driven by lowered foliar N concentration. Neither the foliar C concentration nor foliar C/N for trees of urban forests was statistically higher than those of rural forests. For variation by taxonomic classification, C₄ species Amaranthus retroflexus and Chenopodium ambrosoides (Amaranthaceae) had lower foliar C/N than did other species and families. Myrsine guianensis (Primulaceae) and Myconia fallax (Asteraceae) had the highest foliar C/N. Therefore, urbanization has not caused a significant response in forest trees for foliar C/N. The change in foliar N concentration was globally the main force driving of the differences in foliar C/N for most tree species in urban forests. More work is needed on foliar C/N in trees at cities in polar regions and the Southern Hemisphere.

To explore differences in leaf morphology between Sapindus mukorossi and Sapindus delavayi, and how the environment might drive these differences, 80 germplasm samples from the Sapindus germplasm nursery in Fujian Province were selected. The study revealed a wide variation and diversity in 16 germplasm traits, both within and between species grown under the same conditions. On average, the relative contribution of intraspecific variability to total variability was more important (83%) than the relative contribution of interspecific variability (17%). PERMANOVA analysis showed differences in leaflet thickness, length, perimeter, length to width ratio, and leaf hairs or trichome density. Correlation analyses between leaf morphological traits and environmental variables indicated that leaves tended to be larger, longer, and thicker in wetter, warmer, and low-altitude conditions. Our analysis of the relationship between climate and leaf morphology revealed that S. mukorossi had a greater sensitivity to climate variation, particularly in response to mean temperatures of the coldest and warmest seasons, which led to differences in leaf traits and the distribution of the two species. These findings contribute to the understanding of leaf morphology variations in S. mukorossi and S. delavayi, and provide a basis for the collection of Sapindus germplasm resources, their cultivation and use to help address climate change.

The tropical arboreal species Brazilian mahogany (Swietenia macrophylla) is very important economically and ecologically, for which understanding ecophysiological variables such as sap flow will improve understanding of the species and its cultivation. This paper aims to measure uncertainties (U) involved in the application of the heat ratio method for determining sap flow in Brazilian mahogany using sets of heating probes and thermometers installed on plants of 18 months of age, cultivated in Yellow Latosol, under a weighing lysimeter and located in a protected environment. The uncertainty in sap flow was calculated as the combination of uncertainty in the thermal diffusivity (U _k), conductive section (U _Sc) and corrected sap velocity (U _Vc). U _k had greater weight in determining the flow of sap in Brazilian mahogany, when compared to U _Sc and U _Vc. The thermal diffusivity during the cycle, or period evaluated, must be adjusted to improve the accuracy of the heat ratio method because the sap flow overestimated transpiration by 15.0%. When soil water was optimal In addition, the vapor pressure deficit linearly and indirectly influenced the SF with a difference of 14.6%.

Subtropical forest in China has received much attention due to its complex geologic environment and bioclimatic heterogeneity. There have been very few studies addressing which climatic factors have shaped both distribution patterns and niche differentiation of species from this region. It also remains unclear whether phylogenetic niche conservatism retains in plant species from this biodiversity-rich subtropical region in China. In this study, we used geographic occurrence records and bioclimatic factors of Prunus dielsiana (Rosaceae), a wild cherry species, combined with the classical ENM-based DIVA-GIS software to access contemporary distribution and richness patterns of its natural populations. The current distribution of P. dielsiana occupied a relatively wide range but exhibited an uneven pattern eastward in general, and the core distribution zone of its populations are projected to concentrate in the Wushan and Wuling Mountain ranges of western China. Hydrothermic variables, particularly the Temperature Seasonality (bio4) are screened out quantitatively to be the most influential factors that have shaped the current geographical patterns of P. dielsiana. By comparison with other sympatric families, climatic niche at regional scale showed a pattern of phylogenetic niche conservatism within cherry species of Rosaceae. The effect of habitat filtering from altitude is more significant than those of longitude and latitude. We conclude that habitat filtering dominated by limiting hydrothermic factors is the primary driving process of the diversity pattern of P. dielsiana in subtropical China.

Forest recovery plays a critical role in regulating eco-hydrological processes in forested watersheds. However, characteristics of the intra-annual runoff variation associated with different forest recovery patterns remain poorly understood. In this study, three forest change periods were identified, the baseline period (1961–1985), reforestation period (1986 − 2000) and fruit tree planting period (2001–2016). We selected the magnitude of seasonal runoff (wet and dry seasons) and distribution characteristics, i.e., non-uniformity coefficient (C _v), complete accommodation coefficient (C _r), concentration ratio (C _n), concentration period (C _d), absolute variation ratio (ΔR) and relative variation ratio (C _max). The pair-wise approach evaluated the intra-annual runoff variation characteristics between forest change periods. Results indicate that reforestation decreased wet season runoff and increased dry season runoff. In contrast, fruit tree planting increased wet season runoff and had no significant effect on dry season runoff. For intra-annual runoff distribution characteristics, reforestation significantly reduced the C _v, C _r, C _n and C _max. Distribution of the intra-annual runoff in the fruit tree planting period was not significantly different from the baseline. We concluded that reforestation reduced the occurance of extreme water conditions in wet and dry seasons and effectively increased the stability of the intra-annual runoff. In contrast, fruit tree planting increased instability and fluctuation of the intra-annual runoff after reforestation. The characteristics of the intra-annual runoff to fruit tree planting was similar to those of the baseline. Therefore, adopting fruit tree planting practices to regulate intra-annual runoff characteristics may not be a practical approach, and impacts of different reforestation practices should be ascertained in our study region. The implications of this study should guide regional land–water management, and this study adds to the understanding of the impacts gained in forest cover on hydrology.

Chinese fir (Cunninghamia lanceolate [Lamb.] Hook.) is a fast-growing species which is not only important as a timber-supplier, but also as an available sink for carbon (C) storage in biomass. Stand age and density are two critical factors that can determine tree C sequestration as interrelated drivers through natural self-thinning. C. lanceolate were planted using 1-year-old bare-root seedlings at the initial density of 1800 stems ha⁻¹ in a 15-ha montane area of Hunan Province, China in 1987. The plantation was thinned twice 10 and 20 years after planting to leave trees of 437.5 ± 26.6, 675.0 ± 155.2 and 895.8 ± 60.1 stems ha⁻¹ as low, medium, and high densities, respectively. Tree height and diameter at breast height (DBH) were measured every 2 years beginning from 23 years (2009) to 31 years (2018) after establishment, timber volume (TV) and biomass C were estimated accordingly. We did not find any interactive effect of age and density on any variables except for height. Both TV and biomass C increased with stand age or decreased in higher densities. The allometric height-DBH relationship can be fitted by an exponential rising-to-maximum model with higher maximum value over time. The decline of biomass C along density fit with the inverse first-order polynomial model which indicated that at least 1300–1500 stems ha⁻¹ may be needed to maximize TV and biomass C for a longer term over 20 years. Therefore, to control the density to a reasonable level, over 1300 stems ha⁻¹ in a rotation over 20 years old will be practical for tree biomass C in Chinese fir plantations.

Sustainable forest management heavily relies on the accurate estimation of tree parameters. Among others, the diameter at breast height (DBH) is important for extracting the volume and mass of an individual tree. For systematically estimating the volume of entire plots, airborne laser scanning (ALS) data are used. The estimation model is frequently calibrated using manual DBH measurements or static terrestrial laser scans (STLS) of sample plots. Although reliable, this method is time-consuming, which greatly hampers its use. Here, a handheld mobile terrestrial laser scanning (HMTLS) was demonstrated to be a useful alternative technique to precisely and efficiently calculate DBH. Different data acquisition techniques were applied at a sample plot, then the resulting parameters were comparatively analysed. The calculated DBH values were comparable to the manual measurements for HMTLS, STLS, and ALS data sets. Given the comparability of the extracted parameters, with a reduced point density of HTMLS compared to STLS data, and the reasonable increase of performance, with a reduction of acquisition time with a factor of 5 compared to conventional STLS techniques and a factor of 3 compared to manual measurements, HMTLS is considered a useful alternative technique.

Stochastic frontier analysis and quantile regression are the two econometric approaches that have been commonly adopted in the determination of the self-thinning boundary line or surface in two and higher dimensions since their introduction to the field some 20 years ago. However, the rational for using one method over the other has, in most cases, not been clearly explained perhaps due to a lack of adequate appreciation of differences between the two approaches for delineating the self-thinning surface. Without an adequate understanding of such differences, the most informative analysis may become a missed opportunity, leading to an inefficient use of data, weak statistical inferences and a failure to gain greater insight into the dynamics of plant populations and forest stands that would otherwise be obtained. Using data from 170 plot measurements in even-aged Larix olgensis (A. Henry) plantations across a wide range of site qualities and with different abundances of woody weeds, i.e. naturally regenerated non-crop species, in northeast China, this study compared the two methods in determining the self-thinning surface across eight sample sizes from 30 to 170 with an even interval of 20 observations and also over a range of quantiles through repeated random sampling and estimation. Across all sample sizes and over the quantile range of 0.90 ≤  τ ≤ 0.99, the normal-half normal stochastic frontier estimation proved to be superior to quantile regression in statistical efficiency. Its parameter estimates had lower degrees of variability and correspondingly narrower confidence intervals. This greater efficiency would naturally be conducive to making statistical inferences. The estimated self-thinning surface using all 170 observations enveloped about 96.5% of the data points, a degree of envelopment equivalent to a regression quantile estimation with a τ of 0.965. The stochastic frontier estimation was also more objective because it did not involve the subjective selection of a particular value of τ for the favoured self-thinning surface from several mutually intersecting surfaces as in quantile regression. However, quantile regression could still provide a valuable complement to stochastic frontier analysis in the estimation of the self-thinning surface as it allows the examination of the impact of variables other than stand density on different quantiles of stand biomass.

To explore the influence of meteorological variables on the growth of Korean pine (Pinus koraiensis Sieb. et Zucc.) plantations and provide a scientific reference for the production and management of Korean pine, three approaches to interpolate meteorological variables during the growing season (i.e., May–September) were compared in Heilongjiang Province, China. Optimized meteorological variable interpolation results were then combined with stand and individual tree variables, based on data from 56 sample plots and 2886 sample trees from Korean pine plantations in two regions of the province to develop an individual-tree diameter growth model (Model I) and an individual-tree diameter growth model with meteorological variables (Model II) using a stepwise regression method. Moreover, an individual-tree diameter growth model with regional effects (Model III) was developed using dummy variables in the regression, and the significance of introducing these dummy variables was verified with an F-test statistical analysis. The models were validated using an independent data set, and the predictive performance of the three models was assessed via the adjusted coefficient of determination (

) and root mean square error (RMSE). The results suggest that the growth increment in tree diameter of Korean pine plantations was significantly correlated with the natural logarithm of initial diameter (ln D), stand basal area (BAS), logarithmic deformation of the stand density index (ln SDI), ratio of basal area of trees larger than the subject tree to their initial diameter at breast height (DBH) (BAL/D), and the maximum growing-season precipitation (Pgmax). The individual-tree diameter growth models of Korean pine plantations developed in this study will provide a good basis for estimating and predicting growth increments of Korean pine forests over larger areas.

Monitoring sample plots is important for the sustainable management of forest ecosystems. Acquiring resource data in the field is labor-intensive, time-consuming and expensive. With the rapid development of hardware technology and photogrammetry, forest researchers have turned two-dimensional images into three-dimensional point clouds to obtain resource information. This paper presents a method of sample plot analysis using two charge-coupled device (CCD) cameras based on video photography. A handheld CCD camera was used to shoot the sample plot by surrounding a central tree. Video-based point clouds were used to detect and model individual tree trunks in the sample plots and the DBH of each was estimated. The experimental results were compared with field measurement data. The results show that the relative root mean squared error (rRMSE) of the DBH estimates of individual trees was 2.1–5.7%, acceptable for practical applications in traditional forest inventories. The rRMSE of height estimates was 2.7–36.3%. Average DBH and heights, and tree density and volume were calculated. Video-based methods require compact observation instruments, involve low costs during field investigations, acquire data with high efficiency, and point cloud data can be processed automatically. Furthermore, this method can directly extract information on the relative position of trees, which is important to show distribution visually and provides a basis for researchers to regulate stand density. Additionally, video photography with its unique advantages is a technology warranting future attention for forest inventories and ecological construction.

Forest management may have significant effects on forest connectivity and natural population sizes. Harvesting old-growth single trees may also change natural patterns of genetic variation and spatial genetic structure. This study evaluated the impacts of forest management using a silvicultural system of seed trees on the genetic diversity and spatial genetic structure of Eremanthus erythropappus (DC.) MacLeish. A complete survey of 275 trees on four plots was undertaken out to compare the genetic variation of a managed stand with an unmanaged stand. We genotyped all adult and juvenile individuals 60 months after the management and compared the genetic diversity and the spatial genetic structure parameters. Genetic diversity was considered high because of an efficient gene flow between stands. There were no genetic differences between stands and no evidence of inbreeding. Genetic clustering identified a single population (K = 1), indicating no genetic differentiation between managed and unmanaged stands. Adult and juvenile individuals of the unmanaged stand were more geographically structured than individuals from the managed one. There was a tendency of coancestry among juveniles at the first class of distance of the managed stand, suggesting a drift of genetic structure possibly caused by management. Understanding early responses to management on genetic diversity and stand structure is a first step to ensuring the effectiveness of conservation practices of tree species. The sustainability of forest management of E. erythropappus on genetic diversity, and more accurately, on spatial genetic structure needs evaluation over time to promote effective conservation of the population size and genetic variability.

The parasitic plant dwarf mistletoe (Arceuthobium) is currently one of the most threatening infestations of coniferous forests worldwide, especially in Eurasia and North America, but its population dynamics in relation to one of its hosts (spruce) remain unclear. Here, toward understanding the population dynamics, differential equations were used to construct a life history model for the two populations, and two relatively independent subsystems, host and parasite, were generated from their symbiotic relationships. A suspected-infection model was used to couple them. The resulting models were used to analyze structural changes in the forest. When each infected spruce was assumed to support 1000 parasite shoots, the spruce population first increased rapidly, then slows. When 2000 parasite shoots were assumed, the forest declined dramatically, slipping to zero in the 10th year, and the spruce seedlings were unable to regenerate. Parasite shoot population curves transformed from exponential J-shapes to logistic S-shapes, reaching population limitations as germination rates changed. These results provide important clues to understanding developmental trends of the present parasite population and will assist in reconstructing invasion histories.

Hybrid combinations of Eucalyptus have increased due to expansion of plantations into unconventional areas and to the search for higher quality timber. However, most of these species have difficulties surviving in vitro cultivation. Active chlorine and sealing systems are often used to reduce contamination and increase gas exchange. The aim of the present study is to evaluate the establishment, multiplication, elongation and adventitious rooting of E. grandis ×  E. urophylla. Two clones (C1 and C2) and four active chlorine concentrations (0.000%, 0.001%, 0.003%, and 0.005%) were tested in the establishment and multiplication phases. Three sealing forms (W/M, 1/M and 3/M) and the same four active chlorine concentrations were applied to the elongation phase. Two luminosities (dark and light) and three sealings (W/M, 1/M and 3/M) were tested during adventitious rooting. Active chlorine concentration of 0.005% led to the lowest fungal contamination rate and to the highest in vitro establishment. Active chlorine concentration of 0.003% resulted in the greatest length and highest number of shoots per explant in the multiplication phase. There were no phytotoxicity problems and the quality of plants grown in an environment with active chlorine was maintained in comparison with those grown in an autoclave. The increase in gas exchange in ventilation systems had a positive impact on the in vitro growth and development of plants.

Eucalyptus clones are selected according to productivity, wood quality, rooting capacity, and resistance to drought, frost and diseases. However, kinetic and morphological parameters that determine the absorption efficiency of nutrients such as nitrate (NO₃ ⁻) and ammonium (NH₄ ⁺) are often not considered in breeding programs. The objective of this study was to evaluate the morphological, physiological and kinetic parameters of nitrogen uptake by clones of Eucalyptus saligna (32,864) and Eucalyptus grandis (GPC 23). Morphological parameters in shoot and root systems, biomass and N concentrations in different organs, photosynthetic pigment concentrations, parameters of chlorophyll a fluorescence and photosynthetic rates were evaluated. Kinetic parameters, maximum absorption velocity (V _max), Michaelis–Menten constant (K _m), minimum concentration (C _min) and influx (I) were calculated for NO₃ ⁻ and NH₄ ⁺ in the two clones. E. grandis clone was more efficient in the uptake of NO₃ ⁻ and NH₄ ⁺, and showed lower K _m and C _min values, allowing for the absorption of nitrogen at low concentrations due to the high affinity of the absorption sites of clone roots to NO₃ ⁻ and NH₄ ⁺. Higher root lengths, area and volume helped the E. grandis clone in absorption efficiency and consequently, resulted in higher root and shoot biomass. The E. saligna clone had higher K _m and C _min for NO₃ ⁻ and NH₄ ⁺, indicating adaptation to environments with higher N availability. The results of NO₃ ⁻ and NH₄ ⁺ kinetic parameters indicate that they can be used in Eucalyptus clone selection and breeding programs as they can predict the ability of clones to absorb NO₃ ⁻ and NH₄ ⁺ at different concentrations.

Somatic embryogenesis of Fraxinus mandshurica has the problems of low somatic embryo (SE) yield, unsynchronized SE development, and a high percentage of deformed SEs. We aimed to improve F. mandshurica SE production by synchronizing SE development, improving SE quality, and inducing root formation to obtain complete regenerated plants. Cotyledons of immature zygotic embryos of F. mandshurica were induced to form callus and then SEs. The SE induction percentage from explants differed among 32 mother trees, and the one with the highest SE induction percentage (29.8%) was used for further experiments. The highest callus induction percentage was 94.2% on ½-strength Murashige and Skoog medium (MS½) supplemented with 0.15 mg·L⁻¹ naphthalene acetic acid. The highest callus proliferation coefficient (240.5) was obtained on McCown’s Woody Plant Medium containing 0.1 mg·L⁻¹ 6-benzyl adenine and 0.15 mg·L⁻¹ 2, 4-dichlorophenoxyacetic acid. The highest number of SEs (1020.5 g⁻¹ fresh weight) was obtained on MS½ medium supplemented with 1 mg·L⁻¹ 6-benzyladenine. The highest number of cotyledon embryos (397/g fresh weight) was obtained by incubating materials on medium containing 1 mg·L⁻¹ abscisic acid and then applying a drying treatment. The cotyledon embryos were milky white, uniformly sized (average length 4.7 mm), and 80% of them were normal. The SE rooting percentage on ½MS medium containing 0.01 mg·L⁻¹ NAA was 37.5%. Overall, the germination percentage of SEs was 26.4%, and complete regenerated plants were obtained after transplanting and acclimation. These results provide more possibilities for the preservation and breeding of F. mandshurica.

Chinquapin (Castanea henryi) is a dual-purpose tree species in China valued for as a source of timber and starch. We investigated the effect of four cutting mediums (pure vermiculite; peat:river sand at 3:1 v/v; peat:krasnozem at 1:1 v/v; and pure krasnozem) and three stem cutting periods (March, May, and July) on rooting performance of C. henryi cuttings. Different cutting periods and cutting mediums greatly influenced the rooting rate of C. henryi, ranging from 3.35 to 77.31%. Principal component analysis indicated that the best combination of cutting period and cutting medium was semi-hardwood cuttings (May cuttings) + krasnozem. Histological evidence indicated that adventitious root initials were present by week 5–6, and that the site of root primordia initiation was observed in the vascular cambium. Stem anatomical structures observed at different periods indicated that a xylem/radius ratio of 29.90–37.42% and a fractured phloem fiber ring are indicative of rooting success. The relational model between rooting index and medium properties indicated that nutrient content and porosity significantly influenced callus production. However, pH strongly affected C. henryi root formation, with the Pearson correlation coefficients for May and July cuttings of − 0.856 and − 0.947, respectively. Our protocol is helpful to achieve mass clone propagation of improved C. henryi genotypes, thus overcoming a common hurdle in chinquapin breeding programs.

Vegetation restoration is a main ecological remediation technology for greening saline and alkaline soils. The objectives of this study were to determine the effect of 1-aminobenzotriazole (ABT-1) on the growth and physiology of Tamarix chinensis under salt stress and to determine a suitable ABT-1 concentration and soil salinity (Sc) for propagating T. chinensis-cuttings. Cuttings were soaked in water and ABT-1 solutions at three concentrations(50, 100, and 200 mg L⁻¹) and propagated in pots containing four soil salinity levels, mild (0.3%), moderate (0.6%), and severe (0.9% and 1.2%), and compared with a control. The cuttings were measured to determine growth indices and physiological and biochemical indices (e.g., chlorophyll content, superoxide dismutase activity, peroxidase activity, and malondialdehyde content). ABT-1 was effective in improving survival, growth, and physiological processes of cuttings under salt stress. However, there was a threshold effect when using ABT-1 to facilitate propagation under salt stress. ABT-1 effects were insignificant when applied at low concentrations (< 100 mg L⁻¹). At a high concentration (> 100 mg L⁻¹), ABT-1 limited growth and physiological activities. Under a salt stress level (Sc ≤ 0.9%), ABT applied at a 100 mg L⁻¹ concentration increased chlorophyll content and superoxide dismutase and peroxidase activities in the leaves and reduced malondialdehyde accumulation and membrane lipid peroxidation effects. As a result, ABT-1 enhanced the resistance of T. chinensis to salt stress. However, under high salt stress (> 0.9%) and ABT-1 concentration (> 100 mg L⁻¹), the physiological regulatory ability of T. chinensis seedlings weakened. T. chinensis grew well at a salt stress ≤ 0.9% and ABT ≤ 100 mg L⁻¹ and exhibited relatively high physiological regulatory ability and high salt adaptability

Nonstructural carbon (NSC), which represents the relationship between the carbon source and carbon sink, is an important factor that reflects the functions and performance of a tree. However, little is known regarding the time-series responses of NSC storage in evergreen species to different nitrogen (N) fertilization regimes. This study, which was based on a pot experiment, examined the response of the NSC (soluble sugars and starch) storage to different N addition intensities [light N addition (LN): 6.5 g N m⁻² a⁻¹; moderate N addition (MN): 13.0 g N m⁻² a⁻¹; and heavy N addition (HN): 26.0 g N m⁻² a⁻¹)] in saplings of the evergreen species Podocarpus macrophyllus. Our results showed that the net photosynthetic rate (P _n) under MN was significantly higher than that under LN, but was comparable to that under HN. Moreover, saplings subject to MN had a significant higher leaf biomass than that to LN and HN. These results indicated that the C supply via photosynthesis under MN was greater than that under LN and HN. The NSCs reserve under MN was considerable with that under LN, which suggested that saplings in MN group consumed higher and stored lower properties of NSCs than those in LN group. However, saplings under HN stored higher properties of NSCs than those under MN considering that no difference in NSCs pools was found between the two treatments. The leaf N concentrations were found in the increasing sequence of LN < MN < HN, whilst the leaf chlorophyll concentration under HN was obviously lower than that under MN. The growth rate under MN was higher than that under LN and HN. We concluded that the NSCs allocation between consumption and reserve in P. macrophyllus saplings depended on soil N availability, and an excessive N addition to soil favors the storage rather than the consumption of NSCs by plants.

Populus alba ×  P. glandulosa clone 84 K, derived from South Korea, is widely cultivated in China and used as a model in the molecular research of woody plants because of high gene transformation efficiency. Here, we combined 63-fold coverage Illumina short reads and 126-fold coverage PacBio long reads to assemble the genome. Due to the high heterozygosity level at 2.1% estimated by k-mer analysis, we exploited TrioCanu for genome assembly. The PacBio clean subreads of P. alba ×  P. glandulosa were separated into two parts according to the similarities, compared with the parental genomes of P. alba and P. glandulosa. The two parts of the subreads were assembled to two sets of subgenomes comprising subgenome A (405.31 Mb, from P. alba) and subgenome G (376.05 Mb, from P. glandulosa) with the contig N50 size of 5.43 Mb and 2.15 Mb, respectively. A high-quality P. alba ×  P. glandulosa genome assembly was obtained. The genome size was 781.36 Mb with the contig N50 size of 3.66 Mb and the longest contig was 19.47 Mb. In addition, a total of 176.95 Mb (43.7%), 152.37 Mb (40.5%) of repetitive elements were identified and a total of 38,701 and 38,449 protein-coding genes were predicted in subgenomes A and G, respectively. For functional annotation, 96.98% of subgenome A and 96.96% of subgenome G genes were annotated with public databases. This de novo assembled genome will facilitate systematic and comprehensive study, such as multi-omics analysis, in the model tree P. alba ×  P. glandulosa.

Growth characteristics have complex inheritance patterns and genotype (G) by environment (E) interaction make predicting tree response to environmental changes difficult. In this study, the growth of seven poplar clones at three different sites was taken as the research focus, and heights and basal diameters were investigated in the second growing season. An ANOVA showed that all main effects, site, clone number and their interactions were highly significant in the overall F-tests. The coefficients of variation and repeatability of different traits ranged from 15.5 to 43.9% and from 0.549 to 0.912, respectively. AMMI (Additive Main Effects and Multiplicative Interaction) analysis results showed that genotype, environment and G × E interaction were significantly highly correlated. The stability analysis indicated that different clones showed different growth traits on different sites, which suggests that elite clones should be selected separately for different sites. Based on the growth traits, under a 10% selection rate, three clones were selected for different sites and the genetic gains of growth traits ranged from 4.7 to 11.2%. The three selected clones could be used to establish plantations in the future in different sites.

Development of strategies to deconstruct lignocellulosic biomass in tree species is essential for biofuels and biomaterials production. We applied a wood forming tissue-specific system in a hybrid poplar to express both PdSuSy (a sucrose synthase gene from Populus deltoides × P. euramericana that has not been functionally characterized) and HCHL (the hydroxycinnamoyl-CoA hydratase-lyase gene from Pseudomonas fluorescens, which inhibits lignin polymerization in Arabidopsis). The PdSuSy-HCHL overexpression poplars correspondingly driven by the promoters of Arabidopsis AtCesA7 and AtC4H resulted in a significant increase in cellulose (> 8%), xylan (> 12%) and glucose (> 29%) content, accompanying a reduction in galacturonic acid (> 36%) content, compared to control plants. The saccharification efficiency of these overexpression poplars was dramatically increased by up to 27%, but total lignin content was unaffected. These transgenic poplars showed inhibited growth characteristics, including > 16% reduced plant height, > 10% reduced number of internodes, and > 18% reduced fresh weight after growth of 4 months, possibly due to relatively low expression of HCHL in secondary xylem. Our results demonstrate the structural complexity and interaction of the cell wall polymers in wood tissue and outline a potential method to increase biomass saccharification in woody species.

Change in land-use practices can result in major shifts in the cycling of various elements, particularly nitrogen (N), which is prone to anthropogenic perturbations. For quantifying these shifts, accurate measurements of rates of biogeochemical transformations of N are needed. We used the (¹⁵N) isotope dilution technique to understand the effects of the types of forest alteration on (N) transformation rates by comparing gross N mineralization and ammonium (NH₄ ⁺) consumption rates in soils of a managed forest, an unmanaged forest, and a rubber plantation in Kerala, India. Overall, nitrate (NO₃ ⁻) dominated soils of the managed and unmanaged forests, whereas soils in the rubber plantation showed relatively higher NH₄ ⁺ concentration. Total N (TN) and total organic carbon (TOC) concentrations were the highest under the rubber canopy (TN: 1.49 ± 0.02 mg N g⁻¹; TOC: 7.96  ± 0.86 mg C g⁻¹). In soils of all three forest types, gross N mineralization rates were higher compared to NH₄ ⁺ consumption rates. Despite high TN and TOC concentrations, the rates of gross N mineralization and NH₄ ⁺ consumption were considerably lower in the rubber plantation (mineralization: 1.08  ±  0.08 mg N kg⁻¹ d⁻¹; consumption: 0.85 ±  0.09 mg N kg⁻¹ d⁻) compared to the managed (mineralization: 3.71 ±  0.35 mg N kg⁻¹ d⁻¹; consumption: 2.20  ±  1.41 mg N kg⁻¹ d⁻¹) and unmanaged (mineralization: 2.20 ± 1.07 mg N kg⁻¹ d⁻¹; consumption: 1.39 ±  0.27 mg N kg⁻¹ d⁻¹) forests. The lower NH₄ ⁺ consumption rates in the rubber plantation led to significantly higher (p < 0.05) residence time of NH₄ ⁺ (~  4 days) compared to the managed and unmanaged forests (< 2 days), possibly contributing to acidification of rubber soils (pH ~ 4.8). These results together suggest that replacement of naturally grown forests with a mono-cropped plantation such as rubber negatively impact rates of N transformation processes in tropical soils and imply that change in tree species composition of naturally grown forests can adversely affect soil microbial activity. We recommend intercropping these plantations with commercial crops to maintain soil microbial diversity and biogeochemical cycling for sustainable forest management.

Graphene oxide (GO), a carbon nanomaterial that is widely used in the environment and other industries, may pose potential risks to ecosystems, especially the soil ecosystem. Some soils in Northeast China are frequently polluted with cadmium (Cd) metal. However, there is no study on the influence of GO on the Cd-contaminated soil microbial community and soil chemical properties. In this study, Cd (100 mg kg⁻¹)-polluted soils were treated with different concentrations of GO (0, 25, 50, 150, 250, and 500 mg L⁻¹, expressed as T1, T2, T3, T4, T5, and T6, respectively) for 40 days. The treatment without Cd pollution and GO served as the control (CK). Then, we investigated the influence of the GO concentrations on the bacterial community and chemical properties of Cd-polluted Haplic Cambisols, the zonal soil in Northeast China. After GO addition, the richness and diversity indexes of the bacterial community in Cd-contaminated Haplic Cambisols initially increased by 0.05–33.92% at 25 mg L⁻¹, then decreased by 0.07–2.37% at 50 mg L⁻¹, and then increased by 0.01–24.37% within 500 mg L⁻¹ again. The species and abundance of bacteria varied with GO concentration, and GO significantly increased bacterial growth at 25 and 250 mg L⁻¹. GO treatments influenced the bacterial community structure, and the order of similarity of the bacterial community structure was as follows: T4 = T5 > T1 = T6 > T2 > T3 > CK. Proteobacteria and Acidobacteria were the dominant bacteria, accounting for 36.0% and 26.2%, respectively, of soil bacteria. Different GO treatments also significantly affected the metabolic function of bacteria and further influenced the diversity of the bacterial community structure by affecting several key soil chemical properties: soil pH, organic matter and available potassium, phosphorus, and cadmium. Our results provide a theoretical basis for scientific and comprehensive evaluation of the environmental impacts of GO on the zonal forest soils of Northeast China.

Changbai Mountain, central in the distribution of Pinus koraiensis, supports a virgin Korean pine forest with vertical gradient distribution. Soil extracellular enzyme activity (EEA) and enzyme stoichiometry (ES) are reliable indicators of the energy and nutrients utilized by microbial communities and of soil nutrient changes. We measured four representative soil EEAs (sucrase, cellulase, urease, acid phosphatase) at two soil layers (A: 0–5 cm and B: 5–10 cm) beneath Korean pine forest at five elevations on Changbai Mountain during growing season. The vertical and seasonal variations of EEAs were analyzed by soil enzyme stoichiometry to quantify the role of soil microorganism in the nutrient cycling process. The activities of four soil extracellular enzymes and the ratios of enzyme activity to soil microbial biomass carbon (EA/ SMBC) did not vary with elevation. The first partition point of multiple regression trees was in September, and the second branch was split by elevation. Seasonal change had more influence on soil enzyme activity (A layer: 75.6%; B layer: 71.3%) than did change in elevation (A layer: 7.8%; B layer: 7.5%). Over one entire growing season, both vector length and vector angle were unchanged by elevation, but varied significantly by month. Among the soil physicochemical factors, available phosphorus and pH were the main factors affecting the four soil EEAs. The ratio of basal area of the coniferous tree to broad-leaved tree species (S_con/S_br), soil microbial biomass carbon (MBC) and nitrogen (MBN) influenced the four soil EEAs. The results of vector analysis revealed that C and N sources were generally sufficient, but P was limiting (vector angle > 45°). The vector angle for September was significantly higher than for other months. This result verified that phosphorus was the limiting factor affecting soil microorganism function in nutrient metabolism and cycling. Soil enzyme stoichiometry proved to be an efficient index for quantifying soil microorganism-mediated nutrient cycling in the Korean pine ecosystem.

Fires are an important factor impacting forest ecosystems of Daxing’anling and have a significant effect on soil microbial community structure. In this study, high-throughput sequencing for 16S rDNA and ITS rDNA were applied to analyze the changing characteristics and driving factors of bacterial and fungal community structures in burned areas with different fire severity. PICRUSt2 software was used to predict the functional characteristics of burned areas with different fire severity. The purpose was to unveil the responsive relationships among the structure and function of bacterial and fungal communities, fire severity, and post-disturbance restoration times. After high severity fires, the destruction of surface vegetation and loss of soil nutrients reduced the diversity and abundance of soil bacteria and fungi. The soil bacteria community structure, which was dominated by Acidobacteria, Proteobacteria, and Actinobacteria, changed to be dominated by Proteobacteria and Chloroflexi. As well, soil fungal community changed from domination by Helotiales, Eurotiales and Russulales to domination by Archaeorhizomycetales and Helotiales. Over time, soil bacterial community was gradually restored to pre-fire levels 30 years after the fire. Soil fungal community changed and failed to restore to pre-fire levels after 30 years. After low/intermediate severity fires, environmental factors were relatively unchanged so that soil bacteria diversity and abundance increased, optimizing community composition. The diversity and abundance of soil fungi decreased and the community structure changed slightly. Over time, both bacterial and fungal communities were gradually restored to pre-fire levels 30 years after the fire. After fire disturbance, with increasing severity, soil carbon fixation, lignin degradation, mineralization of organic nitrogen and hydrolysis of organic phosphorus are enhanced. Denitrification is weakened. Therefore, forest fires have certain positive effects on carbon, nitrogen and phosphorus cycles where soil bacteria and fungi are involved.

The bacteria, Serratia marcescens (SM1) was previously obtained from the black-winged termite, Odontotermes formosanus Shiraki. SM1 was highly toxic to O. formosanus, however, the mechanism of toxicity is unclear. In this study, toxicity test results showed that the main components that affected O. formosanus were in a supernatant and that the insecticidal protease in the supernatant resulted in the death of O. formosanus. In addition, zinc sulphate recovery experiments indicated that the metalloproteinases in the supernatant were more harmful. These results provide a theoretical foundation for the future biological control of termites, the basis for the development of pest control technology and the discovery of new pesticides.

In order to found new carriers of pine wood nematode (PWN), Bursaphelenchus xylophilus, beetles were collected from pine wilt disease-affected areas in six provinces in China. A total of 8830 beetles of 29 species was collected and examined to determine whether they were PWN carriers. Eight species were identified as carriers. Results included the first worldwide report of Monochamus nigromaculatus, Semanotus sinoauster, and Uraecha angusta being carriers of PWN, and the first report from China of Arhopalus rusticus carrying PWN. Monochamus alternatus was commonly collected in all six provinces and was the dominant species in four inland affected areas and A. rusticus was dominant in two coastal affected areas. The species varied between different neighboring regions in the same province. The distribution of the same species varied considerably over different regions.

The pine wood nematode (PWN), Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, is the pathogen of pine wilt disease (PWD) which can devastate forests. PWN can be of high or low severity and the mechanisms underlying the differences in virulence are unclear. Therefore, it is necessary to study the relationship between differentiation of PWN severity and its resistance to the main defensive substances of pine species (i.e., α-pinene and H₂O₂). The feeding rate and fecundity of PWN was examined at different levels of virulence under conditions of α-pinene and H₂O₂ stress. Moreover, the expression patterns of the main resistance genes of PWN with different virulence were determined under conditions of α-pinene and H₂O₂ stress. The feeding rate and fecundity of the high virulence strain AMA3 were higher than those of the low virulence strain YW4. The expression levels of the autophagy gene BxATG5, cytochrome P450 gene BxCYP33D3, and glutathione S-transferase genes BxGST1 and BxGST3 in AMA3 increased significantly upon exposure to α-pinene for 2 h, while these genes showed smaller degrees of upregulation in YW4. Under conditions of H₂O₂ stress, the expression levels of BxATG5, catalase genes Bxy-ctl-1and Bxy-ctl-2, and the 2-cysteine peroxiredoxin gene BxPrx in AMA3 were higher than those in YW4. These findings suggest that high virulence PWN has greater resistance to pine defensive substances α-pinene and H₂O₂ than low virulence PWN, and resistance genes mediate the differential resistance of PWN strains. This study will contribute to the clarification of the mechanism underlying virulence differentiation of PWN and will advance understanding of the pathogenic mechanism of PWD.

To understand and improve the stability of the insecticidal activity of tobacco extract, the 3rd instar larvae of Malacosoma neustria testacea was determined by the leaf film method. Spectrophotometry identified extract effects on activities of several enzymes. In addition, to improve the stability of the extract, microcapsules were prepared by complex coacervation and phase separation with the extract as core material, and gelatin and gum arabic as wall material. With the embedding rate as the evaluation index, the response surface method was used to optimize the preparation process of the microcapsules. The results show that the extract had a strong insecticidal activity on the larvae, with inhibitory effects on several enzymes examined of carboxylesterase, acetylcholinesterase, glutathione-S transferase, catalase, and superoxide dismutase. The inhibition rate increased with time. The best preparation process of tobacco extract microcapsules was 25% mass fraction of emulsifier, 2.05% mass fraction of gelatin, 3% mass fraction of gum arabic, 1.34 wall core ratio, 36 min of complex coacervation time. The embedding rate was 58.4% which is approximately the theoretical embedding rate (58.9%). The microcapsules prepared by this method have a smooth surface, good combining form and particle size distribution, and a median diameter of 8.6 μm. Infrared characteristic peaks of the extracts were preserved at 877.55 cm^‒1 and 2922.13 cm^‒1. Microencapsulation can improve the thermal stability of the tobacco extract. Indoor toxicity tests showed that LC₅₀ of extract microcapsules was 20.2 mg·mL^‒1, equivalent to the toxicity level of the tobacco extract itself, indicating that microencapsulation did not reduce extract insecticidal effects. This research may provide a reference for the optimization of the tobacco extract microcapsule preparation process.

Exoristobia sinica sp. nov. is described as new to science and a key is provided to the Chinese species based on females.

Transparent wood has potential application in intelligent building, solar cell, electronics, and other advanced materials, while its single functionability hinders its further development. Flexible transparent wood (FTW) was prepared by alkaline pretreatment and bleaching treatment of paulownia wood followed by impregnation of epoxy resin and ethylene glycol diglycidyl ether (EDGE). The effect of delignification degree on the optical and mechanical properties of FTW was studied, and the influence of the epoxy/EDGE ratio on the flexibility and mechanical properties of FTW was also investigated. The results showed that higher delignification degree resulted in higher transmittance of FTW. More EDGE addition led to better flexibility of FTW, while overmuch addition of EDGE will reduce the mechanical properties. The optimal FTW sample resulted in a high transmittance of 89% and an ultrahigh haze value of 97% with outstanding flexibility and excellent mechanical properties. The investigation of FTW broadens the research field of transparent wood, and provides great possibility for its application in flexible wearable devices and flexible materials.