A protective forest, including shelterbelt, windbreak, and shelter forest as its synonyms, is characterized by the protective functions of various forest types distributed or planted on ecologically fragile areas or nearby the objects that need to be protected using the ecological effects of forests. Ecological mechanisms for management practices of protective forests is one of the disciplinary orientations in forest ecology and management. Most protective forest studies are dependent on forestry eco-engineering, such as the Great Plains Shelterbelt Project in the United States, the Great Plan for the Transformation of Nature in the Soviet Union, and the Three-North Afforestation Program in China. The development of sustainable management of protective forests has been given increasing attention by governments, scientists, and media due to their impacts on environment conservation and global change. We introduce forestry eco-engineering and provide a review of their main ecological mechanisms for management practices of protective forests. Ecological mechanisms for management systems currently applied are emphasized, i.e., the theory of protection maturity and phase-directional management; the relationship between structure and protective functions and structural optimization measures; and, the decline mechanism and ecological restoration strategies. In addition, several unresolved problems in management practices of protective forests are discussed as well as the prospects for ecological mechanisms for management practices of protective forests in the future, which include: (1) theories and technologies for management practices of protective forests at the landscape or regional scale; (2) the decline mechanisms and corresponding ecological restoration approaches across multiple scales; and, (3) the comprehensive assessment of forestry eco-engineering at large-scales based on ecosystem principles.

Tree species dominate many ecosystems throughout the world and their response to climate, in light of global warming, is a matter of primary concern. This review describes past and ongoing research in Rhododendron, an ecologically important and well-adapted genus of more than 1000 species, occupying diverse habitats. Research to date indicates survival ability and mechanisms, with an emphasis on cold tolerance. The capability of long-distance gene flow in these species increases their genetic variability which in turn enhances their adaptability to newer niches as well as to environmental gradients (mainly temperature). Attempts to explain the molecular basis of morphological and behavioural changes in Rhododendron against cold-induced damage has been made. Gradual advances in ‘omics’ have led to an enriched genomic resource dissecting the role and interaction of multiple molecular factors participating in cold adaptability. However, fewer genetic studies are available on species with an inherent or a default cold-tolerance ability. Considering this fact, understanding specific features of an adapted species can provide insights on overriding the effects of desiccation and determining phase transitions in other plants as well. We propose to integrate ecological and evolutionary studies with functional genomics to improve predictions of tree responses to their environment.

This study investigated the feasibility of hyperspectral imaging techniques to estimate the vigor of heat-damaged Quercus variabilis seeds. Four thermal damage grades were classified according to heat treatment duration (0, 2, 5, and 10 h). After obtaining hyperspectral images with a 370–1042 nm hyperspectral imager that included visible and near infrared light, germination was tested to confirm estimates. The Savitzky–Golay (SG) second derivative was used to preprocess the spectrum to reduce any noise impact. The successive projections algorithm (SPA), principal component analysis, and local linear embedding algorithm were used to extract the characteristic spectral bands related to seed vigor. Finally, a model for seed vigor classification of Q. variabilis based on partial least squares support vector machine (LS-SVM) with different spectral data sets was developed. The results show that the spectrum after SG second derivative preprocessing was better for developing the model, and SPA performed the best among the three feature band selection methods. The combination SG second derivative-LS-SVM provided the best classification model for Q. variabilis seed vigor, with the prediction set reaching 98.81%. This study provides an important basis for rapid and nondestructive assessment of the vigor of heat-damaged seeds using hyperspectral imaging techniques.

Acid rain has become a major concern due to increasing atmospheric pollution, particularly in China. We investigated whether acid rain inhibits the germination of seeds and subsequent emergence of seedling of four tree species from southern China: Cunninghamia lanceolata, Fokienia hodginisi, Pinus massoniana and Phoebe zhennan by simulating acid rain with pH of 2.5, 3.5, 4.5 and 5.5. We hypothesized that the inhibitory effect of acid rain on germination of seeds and emergence of seedling varies between species and the degree of acidity. A solution of 1 N H₂SO₄ and 1 N HNO₃ in the ratio of 10–1 was prepared and diluted to four pH levels, and seeds were supplied with solutions of these pH values and distilled water as control and tested for germination in a controlled growth chamber. The results revealed that simulated acid rain of pH 2.5 adversely affected the germination capacity of F. hodginisi and P. zhennan; while all acid solutions significantly increased germination of P. Massoniana; but had no effect on germination of C. Lanceolata seeds. Strong acid solution (pH of 2.5) adversely affected elongation of radicle and hypocotyl as well as fresh and dry weights of radicle and hypocotyl of tender seedlings. The result demonstrated that seedling emergence is more sensitive than seed germination to simulated acid rain, and germination of conifer species are less sensitive than broad leaved species to simulated acid rain. As a whole, acid rain of pH of 3.5 is the threshold level and acid rain below this value will have a detrimental effect on seed germination and seedling emergence.

The induction and proliferation of embryogenic callus are key steps for large-scale propagation of somatic embryogenesis pathway and long-term preservation of coniferous germplasm. Callus can be induced from immature embryos of Korean pine (Pinus koraiensis Sieb. et Zucc.; Pinaceae) as explants, but there are problems, such as low proliferation efficiency, loss of embryogenicity, poor vigor; thus, best conditions for proliferation and culture of immature embryos of Korean pine are not yet clear. To solve the problems with somatic embryogenesis of Korean pine and determine the best culture conditions for callus induction and proliferation, we varied hormone concentration, subculture cycle of proliferation and other plant growth regulators combinations in media to induce callus formation by megagametophytes of three Korean pine families at different developmental stages, then analyzed the effects on embryogenic callus retention and cell proliferation using a quadratic regression orthogonal rotation design. The results showed that the family origin and collection date of explants significantly affected callus induction (induction rate reached 1.67%). Embryogenic maintenance and callus proliferation were best on DCR medium supplemented with 0.25 mg L⁻¹ 6-benzyl adenine, 1 mg L⁻¹ naphthaleneacetic acid, 30 g L⁻¹ sucrose, 500 mg L⁻¹, l-glutamine, 500 mg L⁻¹ casein hydrolysis and 6.5 g L⁻¹ agar. In addition, the combination of 2,4-dichlorophenoxyacetic acid + 6-benzyl adenine also had a better proliferative effect on callus. The effects of different combinations of growth regulators on callus proliferation efficiency were significantly different. Transfer to new medium every 13–15 days not only maintained robust callus vigor, but also yielded a larger proliferation coefficient. The techniques and conditions for embryogenic callus induction and proliferation of Korean determined here will serve as a foundation for establishing a large-scale system for somatic embryogenesis and propagation of Korean pine.

This study evaluates the structure and regeneration status of woody species in the Munessa Forest, a dry Afromontane forest in southern Ethiopia. Vegetation data were collected using a systematic sampling method. Density and distribution of seedlings, saplings and mature trees were assessed along an altitudinal gradient using quadrats of different sizes. The number of individuals, frequencies, heights and DBH of species > 1 m and DBH > 2.5 cm were recorded in altitudinal bands of 100 m. Analysis of the vegetation structure shows that the density of woody species decreases as DBH and height class increases. Basal area of stems with DBH > 2.5 cm was 53.4 m² ha⁻¹. Population structure and regeneration patterns indicate a significant degradation of the forest due to anthropogenic disturbances. Regeneration was better for less valuable woody species than for species with economic and ecological value. This suggests a discontinuous recruitment of these species due to selective cutting of middle and higher diameter classes. Therefore, enrichment planting of high value, endangered species is necessary to maintain them as part of this forest. There is a need to develop and implement an effective forest management plan for sustainable use of these forest resources.

Insufficient knowledge on Ugandan grown Eucalyptus grandis W. Hill ex Maiden wood properties, high demand, and processing challenges led to a study into its physical properties. We obtained the variation of basic density (BD), calorific value (CV) and volumetric shrinkage (VS) within tree height and tree-age of E. grandis, and its appropriate use based on these properties. Trees with good boles were harvested from Kabarole District in western Uganda to produce specimens as prescribed by British Standards and ASTM standard wood testing procedures. Secondary data reviews and statistical analysis using ANOVA, Tukey’s test and multivariate analysis were done to obtain property estimates and their variation within trees and amongst tree ages. The mean BD of E. grandis is 413.6, 380.5, 471.0, and 501.1 kg m⁻³ at 3, 6, 9, and 12 years, respectively, showing significant increase with tree age (p = 0.003). The pattern of BD with tree height showed a reduction with tree height although with higher values in the middle portion of the tree. The CV increases (p = 0.014) with tree age and reduces with tree height with values of 14,560.32, 15,447.3, 16,079.11, and 16,932.6 kJ kg⁻¹ at 3, 6, 9, and 12 years, respectively. The percentage VS was 11.02, 9.84, 12.31, and 14.45 for 3-, 6-, 9-, and 12-year-old trees, respectively, and it did not vary significantly (p = 0.088) with tree height. Basing on these property values, E. grandis wood could be used for scaffolding, light constructions and fuel wood production. Its seasoning needs to be longer with well monitored drying schedules to reduce seasoning defects caused by the high VS. Further studies on strength properties, seasoning schedules, panel products properties and tree-age chemical variations would improve the knowledge about its wood quality and would enhance its efficient utilization.

Relationships between stem growth and climatic and edaphic factors, notably air temperatures and soil moisture for different slopes, are not completely understood. Stem radial variations were monitored at the bottom and top slope positions in a Larix principis-rupprechtii plantation during the 2017 and 2018 growing seasons. Total precipitation during the growing season in 2017 and 2018 was 566 mm and 728 mm, respectively. Stem contractions typically occurred after mid-morning followed by swelling in the late afternoon in both plots, reflecting the diurnal cycle of water uptake and loss. Trees at the two locations showed the same growth initiation (mid-May) because of the small differences in air and soil temperatures. There were no significant differences in cumulative stem radial growth between the bottom plot (1.57 ± 0.34 mm) and the top plot (1.55 ± 0.26 mm) in 2018. However, in 2017, the main growth period of the bottom plot ceased 17 days earlier than in the top plot, while cumulative seasonal growth of the bottom plot (1.08 ± 0.25 mm) was significantly less than the top plot (1.54 ± 0.43 mm). Maximum daily stem shrinkage was positively correlated with air and soil temperatures, solar radiation, vapor pressure deficits, and negatively correlated with volumetric soil moisture content. The maximum daily shrinkage reflected transpiration rates as affected by environmental factors. Daily radial stem increment was correlated with precipitation and volumetric soil moisture in both years, but with air temperatures only in 2017. The seasonal growth of L. principis-rupprechtii Mayr thus shows interannual dynamics, while precipitation constitutes a key driving factor.

Accurate prediction of stem diameter is an important prerequisite of forest management. In this study, an appropriate stem taper function was developed for upper stem diameter estimation of white birch (Betula platyphylla Sukaczev) in ten sub-regions of the Daxing’an Mountains, northeast China. Three commonly used taper functions were assessed using a diameter and height dataset comprising 1344 trees. A first-order continuous-time error structure accounted for the inherent autocorrelation. The segmented model of Max and Burkhart (For Sci 22:283–289, 1976. https://doi.org/10.1093/forestscience/22.3.283) and the variable exponent taper function of Kozak (For Chron 80:507–515, 2004. https://doi.org/10.5558/tfc80507-4) described the data accurately. Owing to its lower multicollinearity, the Max and Burkhart (1976) model is recommended for diameter estimation at specific heights along the stem for the ten sub-regions. After comparison, the Max and Burkhart (1976) model was refitted using nonlinear mixed-effects techniques. Mixed-effects models would be used only when additional upper stem diameter measurements are available for calibration. Differences in region-specific taper functions were indicated by the method of the non-linear extra sum of squares. Therefore, the particular taper function should be adjusted accordingly for each sub-region in the Daxing’an Mountains.

In Europe, tropospheric ozone pollution appears as a major air quality issue, and ozone concentrations remain potentially harmful to vegetation. In this study we compared the trends of two ozone metrics widely used for forests protection in Europe, the AOT40 (Accumulated Ozone over Threshold of 40 ppb) which only depends on surface air ozone concentrations, and the Phytotoxic Ozone Dose which is the accumulated ozone uptake through stomata over the growing season, and above a threshold Y of uptake (PODY). By using a chemistry transport model, we found that European-averaged ground-level ozone concentrations (− 2%) and AOT40 metric (− 26.5%) significantly declined from 2000 to 2014, due to successful control strategies to reduce the emission of ozone precursors in Europe since the early 1990s. In contrast, the stomatal ozone uptake by forests increased from 17.5 to 26.6 mmol O₃ m⁻² despite the reduction in ozone concentrations, leading to an increase of potential ozone damage on plants in Europe. In a climate change context, a biologically-sound stomatal flux-based standard (PODY) as new European legislative standard is needed.

The COVID-19 pandemic has resulted in over 33 million confirmed cases and over 1 million deaths globally, as of 1 October 2020. During the lockdown and restrictions placed on public activities and gatherings, green spaces have become one of the only sources of resilience amidst the coronavirus pandemic, in part because of their positive effects on psychological, physical and social cohesion and spiritual wellness. This study analyzes the impacts of COVID-19 and government response policies to the pandemic on park visitation at global, regional and national levels and assesses the importance of parks during this global pandemic. The data we collected primarily from Google’s Community Mobility Reports and the Oxford Coronavirus Government Response Tracker. The results for most countries included in the analysis show that park visitation has increased since February 16th, 2020 compared to visitor numbers prior to the COVID-19 pandemic. Restrictions on social gathering, movement, and the closure of workplace and indoor recreational places, are correlated with more visits to parks. Stay-at-home restrictions and government stringency index are negatively associated with park visits at a global scale. Demand from residents for parks and outdoor green spaces has increased since the outbreak began, and highlights the important role and benefits provided by parks, especially urban and community parks, under the COVID-19 pandemic. We provide recommendations for park managers and other decision-makers in terms of park management and planning during health crises, as well as for park design and development. In particular, parks could be utilized during pandemics to increase the physical and mental health and social well-being of individuals.

Spatial heterogeneity of fuel moisture content determines the spread rate and direction of a forest fire. Research on the spatial heterogeneity of the moisture content of dead fuel of Larix gmelinii Rupr. showed that: (1) fuel moisture content in litter layer < semi-humus layer < humus layer, and the coefficient of variation decreased with sampling depth; (2) the sill value of the semi-humus layer was highest, the humus layer moderate, the litter layer the smallest, overall, the spatial heterogeneity of the semi-humus layer was the highest. The humus layer in the slant direction and three layers in a vertical direction showed strong spatial correlation with the lowest nugget coefficient of 0.0968; (3) the fuel moisture content of the humus layer showed strong spatial anisotropy; and, (4) estimating the total moisture content of the sampling site by stimulated sampling reasonable control of the sampling interval, and increasing the sampling intensity can reduce the error. When the sampling intensity is increased to more than 16 and the sampling interval 3 m, the standard error is < 15%. The spatial heterogeneity of fuel moisture content is best revealed by increasing sampling density, sampling in different fire seasons, and in different slope directions and positions. The results can provide a scientific basis for forest fire prediction and prevention.

Effective disturbance indices for Hyrcanian forests in Kheyroud, Nowshahr, Iran were determined. The study area was divided into landscape mosaics based on ecosystem parameters including profile type, slope and elevation. Co-occurrence texture indices were derived as forest disturbance factors on the first five bands of Landsat TM, ETM+ and OLI images for the prevailing wood harvest disturbance regimes. These indices were screened using ten types of trend analyses and used for modeling disturbance of the harvesting regime through artificial neural networks. The results show that the selected indices can be useful in distinguishing areas with different disturbance intensities and as such, used in the context of health assessment through the health distance method. The accuracy of the health maps derived from the indices [increasing disturbance] led to give rise higher disturbance classification accuracy.

The determination of site productivity in forest ecosystems plays a crucial role in resource management. This study was carried out to identify relationships between site characteristics and height growth of Corsican maritime pine (Pinus pinaster Ait.) plantations in Turkey. Sixty-nine sample plots > 20 years of age were selected from locations with different inclinations, aspects, elevations, slope positions and site class. Soil samples were taken at various depths. Height and age were measured on a dominant tree after felling in each plot. Physical and chemical properties of the soil were determined. Relationships between site index (SI₂₅) and physiographic factors, climatic attributes as well as soil properties were evaluated using correlation analysis and multiple regression analysis. Site index was significantly related with annual precipitation, mean spring rainfall, rainfall June to September, rainfall of the driest month, length of the dry period, mean maximum temperature, mean temperature of the warmest month, stoniness of the soil, sand, silt, clay, pH, electrical conductivity, and available water capacity. Multiple regression accounted for 57.9% of variations in height growth. The models obtained can be used to determine the site index of potential areas in Turkey for maritime pine. It can be said that the productivity of maritime pine may decline in the future due to global climate change.

Capturing leaf color variances over space is important for diagnosing plant nutrient and health status, estimating water availability as well as improving ornamental and tourism values of plants. In this study, leaf color variances of the Eurasian smoke tree, Cotinus coggygria were estimated based on geographic and climate variables in a shrub community using generalized elastic net (GELnet) and support vector machine (SVM) algorithms. Results reveal that leaf color varied over space, and the variances were the result of geography due to its effect on solar radiation, temperature, illumination and moisture of the shrub environment, whereas the influence of climate were not obvious. The SVM and GELnet algorithm models were similar estimating leaf color indices based on geographic variables, and demonstrates that both techniques have the potential to estimate leaf color variances of C. coggygria in a shrubbery with a complex geographical environment in the absence of human activity.

To analyze the degree and pattern of phenotypic variation in leaves of Tetracentron sinense Oliv from the perspective of genetic and environmental adaptation and thus contribute to effective evidence-based conservation and management strategies for germplasm resources, we measured 17 morphological and epidermal micromorphological leaf traits from 24 natural populations of T. sinense. Nested analysis of variance, multiple comparison, principal component analysis (PCA), cluster analysis, and correlation analysis were used to explore phenotypic leaf variation among and within populations and potential correlations with geographic and environmental factors. There were significant differences in 17 leaf phenotypic traits among and within populations. The mean phenotypic differentiation coefficient of the 17 traits was 56.34%, and the variation among populations (36.4%) was greater than that within populations (27.2%). The coefficient of variation (CV) of each trait ranged from 4.6 to 23.8%, and the mean was 11.8%. Phenotypic variation of leaves was related to environmental factors such as average annual sunshine hours, average July temperature, and average annual rainfall. The variation changed along gradients of longitude, latitude, and altitude. The PCA clustered the 24 natural populations into four groups. Our study suggests that phenotypic variation in T. sinense occurred primarily among populations, with moderate levels of phenotypic differentiation among populations and low levels of phenotypic variation within populations. The plant’s poor adaptability to the environment is likely an important contributor to its endangerment. Accordingly, conservation strategies are proposed to protect and manage the natural populations of T. sinense.

Cloud forest ecosystems of the Latin American tropics are highly threatened by changes in land-use such as expanding croplands and livestock pastures that promote shifts in the structure and composition of plant communities in these forests. However, shade coffee plantations represent a forest management alternative that has been shown to maintain biodiversity in these ecosystems. In this study, we evaluated changes in the composition, diversity, and structure of Mexican cloud-forest woody species for three land use categories: cattle pastures, shade coffee plantations and advanced succession forests. For each category, fifteen 0.28-ha plots were established and the composition and diversity of vegetation was noted. Composition of species was analyzed using ordination methods, and alpha diversity was compared using Hill numbers. Seventy-seven woody species belonging to 40 families were recorded. Species richness and diversity was high in both the advanced successional forest and coffee plantations compared to cattle pastures. Vegetation composition and structure was similar between late succession forests and coffee plantations with both land uses also being more structurally complex than cattle pastures. Our results show how shade coffee cultivation is a land-use activity that maintains woody plant communities in a manner that aligns with biodiversity conservation.

Understanding the environmental factors that influence tree species composition is essential for successful management of biodiversity and sustainable use of community forest resources. This study aims to assess tree species composition and distribution in the deciduous Ban Mae Chiang Rai Lum Community Forest in Northern Thailand and to analyze the influence of environmental factors on tree biodiversity in the forest. We conducted a stratified systematic sampling of the forest’s total area of 3925 ha, and twenty-five 0.16 ha survey plots were established in three different stands of the deciduous forests to estimate and characterize the difference in biological diversity among the stands. Canonical correspondence analysis (CCA) was used to investigate the environment factors affecting such differences in biodiversity of the stands. The results showed a high diversity of trees in the forest as 197 species, 144 genera, and 62 plant families were recorded. The CCA ordination identified the environmental factors—the most important of which were elevation, distance to streams, soil moisture, organic matter, and distance to communities—that significantly influenced the diversity and distribution of tree species (p < 0.05) in the community forest. Our findings indicate that the implementation of drought reduction measures such as building check dams, fire protection, and monitoring community forest-product usage would be recommended to further biodiversity conservation and the sustainable use of community forest resources.

Secondary tropical forests sequester atmospheric CO₂ at relatively faster rates in vegetation and in soil than old-growth primary forests. Spatial understanding of biomass and carbon stocks in different plant functional types of these forests is important. Structure, diversity, composition, soil features and carbon stocks in six distinct plant functional types, namely: Moist Mixed-Deciduous Forest, Peninsular Sal Forest (PSF), Semi-Evergreen Forest (SEF), Planted Teak Forest, Bamboo Brakes (BB), and Degraded Thorny Shrubby Forest were quantified as secondary tropical deciduous forests of the Chandaka Wildlife Sanctuary, Eastern Ghats of Odisha, India. Seventy-one species ≥ 10 cm Girth at breast height (GBH) were recorded, belonging to 38 families and 65 genera. Above- ground biomass carbon and soil organic carbon ranged from 2.1–72.7 Mg C ha⁻¹ and 20.6–67.1 Mg C ha⁻¹, respectively, among all plant functional types. Soil organic carbon and important value index were positively correlated with above- ground biomass carbon. Maximum carbon allocation was in SOC pool (51–91%), followed by the above- ground biomass pool (9–52%), indicating SOC is one of the major carbon sinks in secondary dry forests. The results highlight the importance of secondary tropical deciduous forests in biodiversity conservation and ecological importance in reducing greenhouse gases.

Kalapi (Kalappia celebica) is an endemic legume of Sulawesi and has been included in the endangered category since the early 1980s. Conservation of the species is possible through ex situ culture techniques. Arbuscular mycorrhizal fungi (AMF) can accelerate plant growth which in turn supports the conservation of endangered species. This study aimed to assess the efficacy of local AMF to accelerate the growth of kalapi and increase nutrient uptake in kalapi grown in gold mine tailing media. There were three AMF treatments, Glomus claroideum, Glomus coronatum, and a mixture of both, plus the control. Each treatment was replicated three times, each consisting of five plants. The results show that the highest AMF colony was obtained by kalapi seedlings inoculated with Glomus coronatum and the mixture of AMF. The range of mycorrhizae inoculation effect values was 59.7–71.3%. AMF inoculation increased growth and dry weight of 4-month-old seedlings compared to controls. Dry and total weights of kalapi inoculated with G. coronatum were significantly different from those inoculated with the AMF mixture. However, they are not significantly different from kalapi inoculated with G. claroideum. The results also show that AMF increased nitrogen and phosphorous uptake by the roots, as well as nitrogen, phosphorous, potassium, manganese and iron by the shoots. All AMF treatments decreased potassium uptake in the roots, except in kalapi inoculated with G. coronatum. The AMF mixture decreased iron contents the roots by 15%. AMF can be developed into biofertilizer to support the conservation of kalapi in tropical Indonesia.

Arbuscular mycorrhizal fungi (AMF) form a near-ubiquitous mutualistic association with roots to help plants withstand harsh environments, and play a key role in the establishment of coastal beach plant communities. Yet little is known about the structure and composition of AMF communities on coastal beaches of eastern China. In this study, we investigated the occurrence, community composition and diversity of AMF associated with common wild plants on a coastal beach of North Jiangsu, China. Almost all of the local wild species were colonized by AMF except for Chenopodium album L. Thirty-seven AMF species were isolated from the rhizosphere belonging to 12 genera in seven families. Glomus was the dominant genus and Funneliformis mosseae the dominant species. The colonization, spore composition and diversity of AMF were strongly related to edaphic factors. Sodium (Na⁺) ions in the soil significantly and negatively affected the colonization rate by AMF and both soil Na⁺ levels and pH had a significant negative effect on AMF spore density and evenness. However, there was a significant positive correlation between species richness and total organic carbon. The results provide insights into soil factors affecting native AMF communities in coastal beach habitats which could benefit vegetation recovery and soil reclamation efforts.

Long-term natural vegetation succession plays a substantial role in the accumulation and distribution of plant and soil C:N:P stoichiometry. However, how plant and soil C:N:P relationships or ratios change along with successional stages over a century in the severely eroded areas remain unclear. These were measured over a 100-year natural succession in five successional stages from annual grasses to climax forests. The results show that natural succession had significant effects on carbon (C), nitrogen (N) and phosphorous (P) concentrations in leaf-litter-soil and their ratios in severely eroded areas. Nitrogen concentrations and N:P ratios in leaf and litter increased from annual grasses to the shrub stage and then decreased in the late successional forest stages. Leaf P levels decreased from annual grasses to shrub stages and did not significantly change during late successional stages. Litter P concentration decreased in the early successional stages and increased during late successional stages, with no overall significant change. Soil C and N concentrations and C:N, C:P and N:P ratios increased with successional stages. Soil C and N concentrations decreased with the increasing soil depth. Both were significantly different between any successional stages and controls (cropland) in the upper 10 cm and 10–20 cm soil layers. Leaf N:P ratios may be used to indicate nutrient limitations and this study suggests that plant growth during the grass stages was limited by N, during the shrub stage, by P, and during the forest stages, by both of N and P. In addition, there were close correlations between litter and leaf C:N:P ratios, soil and litter C and N levels, and C:P and N:P ratios. These results show that long-term natural vegetation succession is effective in restoring degraded soil properties and improving soil fertility, and provide insights into C:N:P relationships of leaf, litter and soil influenced by vegetation succession stage.

In terrestrial ecosystems, deep soils (below 30 cm) are major organic carbon (C) pools. The labile carbon input could alter soil organic carbon (SOC) mineralization, resulting in priming effect (PE), which could be modified by nitrogen (N) availability, however, the underlying mechanism is unclear for deep soils, which complicates the prediction of deep soil C cycling in response to N deposition. A series of N applications with ¹³C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization. Microbial biomass, functional community, metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE. During incubation, glucose addition promoted SOC mineralization, resulting in positive PE. The magnitude of PE decreased significantly with increasing N. The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient. Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels. These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth. Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE. The negative effect of additional N suggests that future N deposition could promote soil C sequestration.

The application of phosphorus (P) to soil can increase its availability to plants and alter P fractions in annual and perennial organs of Cordia trichotoma. If a portion of P accumulates in perennial organs in organic fractions it can be used in the next growth season, possibly decreasing plant dependence on P derived from soil fertilization. However, if P is preferentially accumulated in inorganic fractions in annual organs, plants will be more dependent on phosphate fertilization. This study aimed to evaluate the distribution of P fractions in organs of C. trichotoma grown on sandy soil treated with 120 and 360 kg P₂O₅ ha⁻¹. The control was a zero application. After 24 months following fertilization, C. trichotoma seedlings were cut and separated into leaves, branches, stems and roots, dried, ground and subjected to chemical fractionation of P, which estimates fractions of total soluble P, soluble inorganic and organic P, lipid P, P associated ribonucleic acid and deoxyribonucleic acid, and residual P. P in annual organs, as leaves, accumulated preferentially in the soluble inorganic fraction in both treatments. In perennial organs such as stems and branches, P accumulated preferentially in the soluble organic fraction. The application of 300% of the recommended dosage (360 kg P₂O₅ ha⁻¹) promoted the accumulation of P in soluble organic fractions which may contribute to annual growth the following season and be a strategy to reduce the dependence of 2-year-old stands on soil-derived P and on fertilizers.

Populus spp. have long been used as model woody plant species for molecular biology research. However, tissues of poplar are often recalcitrant to experimental procedures for molecular studies. We generated a hormone autotrophic poplar suspension cell line from a hybrid of Populus alba × P. berolinensis ‘Yinzhong’, named Qu-2. Qu-2 cells are suitable as a model biological system for studying woody plants. Qu-2 cells have many advantages over suspension cell lines derived so far from any other woody plants. Qu-2 cells are very easy to cultivate and can grow on several common plant culture media without the addition of any plant hormone. They show exceptionally high growth rates, reaching an approximately 150-fold increase in biomass after one week of culturing. Another important unique characteristic of Qu-2 cells is that they can be cryopreserved and readily reactivated. Qu-2 cells are suitable for molecular manipulations such as protoplast production, transient transformation, and RNA-seq analysis. Therefore, Qu-2 cells have the great potential to be an excellent model cell line in tree molecular biological research, ranging from physiology to gene function. The Qu-2 cells will be made available to the plant community for research.

Malonyl-CoA synthetases may modulate cell responses to abiotic stress by regulating stress-related signaling transduction pathways or activating expression of transcription factors. However, the molecular mechanism of cold stress tolerance enhanced by malonyl-CoA synthetase is not fully understood. Here, we report that overexpression of the Arabidopsis thaliana malonyl-CoA synthetase gene AAE13.1 resulted in increased cell viability and growth rate and decreased thiobarbituric acid reactive substances under cold stress in rice (Oryza sativa L.), tobacco (Nicotiana tabacum), and slash pine (Pinus elliottii Engelm.). AAE13.1 was associated with cold stress tolerance by increasing the activity of ascorbate peroxidase, catalase, polyphenol oxidase, and peroxidase and the accumulation of acid phosphatase and alkaline phosphatase. Among six rice mitogen-activated protein kinase (MAPK) genes examined, AAE13.1 overexpression increased the expression of OsMAPK genes during cold stress. AAE13.1 activated expression of stress-response genes OsMAPK1, OsMAPK2, and OsMAPK3, indicating that AAE13.1 enhances cold stress tolerance by regulating expression of MAPK genes in plant cells. These results increase our understanding of cold stress tolerance in species of monocotyledons, dicotyledons, and gymnosperms.

The Brazilian state of Acre has an extensive natural reserve of bamboo, making it one of the largest in loco gene banks. The aim of this study was to characterize the structure and genetic diversity of Guadua weberbaueri Pilg. in two populations, one native (FAPB) and the other anthropized (FAPBA), using ISSR markers. The results show that the FAPB population exhibited higher values for all estimates of population diversity. However, the FAPBA population also showed high heterozygosity, corroborated by estimated gene flow (Nm = 3.9) between the populations. The study of the association between Nei’s genetic distances and the geographic distances between the populations were significantly correlated (r = 0.45, p = 0.01), corroborated by the dendrogram revealing two distinct groups corresponding to the collection sites, without mixing classes between populations in the same group. As for the coancestry coefficient, pairs of individuals in the first distance class were positive and significant, indicating that plants that are geographically closer share common alleles with a frequency greater than by chance, which means that there is a tendency that geographically closer individuals are related. Individuals presented similar genetic structure when the geographical distance between them was up to 56 m for FAPB and up to 156 m for FAPBA. It was concluded that anthropized environments exhibit less genetic diversity than native environments, inferring risks for species conservation if appropriate and planned management techniques are not adopted.

Ginkgo biloba is a famous living “fossil” and has played an important role in the evolution of the Plant Kingdom. Here, the complete chloroplast genome of G. biloba was sequenced and analysed. The chloroplast genome was 156,990 bp long and predicted to encode 134 genes including 85 protein-coding genes, 41 tRNA genes and 8 rRNA genes. The chloroplast genome has a typical quadripartite structure with a pair of inverted repeat regions (IRa and IRb, 17,732 bp), a large (LSC, 99,259 bp) and small single (SSC, 22,267 bp) copy region. After an extensive comparison to previously published gymnosperm plastomes, the gene content and organisation of G. biloba showed high divergence, although part was relatively conserved. The two typical IR regions in the G. biloba chloroplast genome were relatively shorter because it the ycf2 gene. In addition, it was obvious that the IR regions and gene loss were responsible for changes in chloroplast genome size and structure stability, which influenced plastome evolution in different gymnosperms. Phylogenetic analysis revealed that G. biloba is sister to cycads rather than to gnetophytes, cupressophytes, and Pinaceae. Overall, the study showed that the genomic characteristics of G. biloba would be of great help in the further research on the taxonomy, species identification and evolutionary history of gymnosperms, especially for their position in plant systematics and evolution.

Genes homologous to members of the MRP gene family in Caenorhabditis elegans are important in drug resistance. To further explore the molecular mechanism of drug resistance in pine wood nematode (Bursaphelenchus xylophilus), we used bioinformatics approaches to analyze genomic data for B. xylophilus and identified Bx-MRP genes. We predicted the structure and function of the genes and encoded proteins. Using bioinformatics programs to predict and analyze various properties of the predicted proteins, including hydrophobicity, transmembrane regions, phosphorylation sites, and topologically isomeric structures, of these Bx-MRP genes, we determined that they function in transmembrane transport. From the results of RT-qPCR, the Bx-MRP family members confer significant differential resistance to different drug treatments. After treatment with different concentrations of emamectin benzoate, avermectin and matrine, the expression of each gene increased with increasing drug concentrations, indicating that the family members play a positive role in the regulation of multidrug resistance.

Eucalypts are important forest resources in southwestern China, and may be tolerant to elevated ground-level ozone (O₃) concentrations that can negatively affect plant growth. High CO₂ may offset O₃-induced effects by providing excess carbon to produce secondary metabolites or by inducing stomatal closure. Here, the effects of elevated CO₂ and O₃ on leaf secondary metabolites and other defense chemicals were studied by exposing seedlings of Eucalyptus globulus, E. grandis, and E. camaldulensis ×  E. deglupta to a factorial combination of two levels of O₃ (< 10 nmol mol⁻¹ and 60 nmol mol⁻¹) and CO₂ (ambient: 370 μmol mol⁻¹ and 600 μmol mol⁻¹) in open-top field chambers. GC-profiles of leaf extracts illustrated the effect of elevated O₃ and the countering effect of high CO₂ on compounds in leaf epicuticular wax and essential oils, i.e., n-icosane, geranyl acetate and elixene, compounds known as a first-line defense against insect herbivores. n-Icosane may be involved in tolerance mechanisms of E. grandis and the hybrid, while geranyl acetate and elixene in the tolerance of E. globulus. Elevated O₃ and CO₂, singly or in combination, affected only leaf physiology but not biomass of various organs. Elevated CO₂ impacted several leaf traits, including stomatal conductance, leaf mass per area, carbon, lignin, n-icosane, geranyl acetate and elixene. Limited effects of elevated O₃ on leaf physiology (nitrogen, n-icosane, geranyl acetate, elixene) were commonly offset by elevated CO₂. We conclude that E. globulus, E. grandis and the hybrid were tolerant to these O₃ and CO₂ treatments, and n-icosane, geranyl acetate and elixene may be major players in tolerance mechanisms of the tested species.

Cyclocarya paliurus is widely distributed in subtropical areas of China. Secondary metabolites in the leaves, including flavonoids and triterpenoids, provide protection against diseases such as hyperlipidemia, diabetes, hypertension, and hypoimmunity. In this study, 343 C. paliurus leaves were collected from 32 distinct populations covering most of the main distribution, to deduce the response of flavonoids and triterpenoids to seven environmental factors. Principal component analysis was performed using seven flavonoid and six triterpenoid compounds. The results show that altitude, latitude, and longitude significantly contributed to variations in total flavonoid and triterpenoid contents. In addition, the interaction of these metabolites was extensively correlated with environment changes, and therefore should be considered during selection and cultivation.

As the energizing and therapeutic effects of infusions of mate (Ilex paraguariensis A.St.-Hil) leaves are increasingly recognized, rising global consumption is also increasing the demand for plantlets with high genetic and morphological qualities. Mini-cuttings are an alternative for clonal plantlets; however, more details are needed on factors that affect the success of this technique. Here, toward maximizing production, we evaluated adventitious rooting competence of mini-cuttings of different sizes and the morphophysiological quality of the resultant plantlets. Small (one bud; length up to 2.5 cm), medium (multiple buds; length 2.6–5.0 cm), and large (multiple buds; length 5.1–10.0 cm) mini-cuttings were planted in a mixture of commercial substrate, vermiculite, and coarse sand (1:1:1 v:v:v), grown in a humidity chamber, then evaluated after 45, 60, 75, and 90 days for survival, percentage of callus and shoot formation, number and length of shoots, percentage of rooted cuttings, and number and length of roots. Any rooted mini-cuttings were then cultivated in commercial substrate and subsurface soil (2:1 v:v) and evaluated after 30, 60, 90 and 120 days of cultivation for morphophysiology of the plantlets, percentage of survival, number of leaves, shoot height, stem diameter, and ratio of shoot height to stem diameter. After 120 days, the plantlets were evaluated for the ratio of shoot and root dry mass, total length, surface area, total volume, and mean diameter of roots and Dickson quality index. Adventitious rooting of the mini-cuttings and the morphophysiological quality of the plantlets were not influenced by the size of the vegetative propagule. Therefore, single-bud mini-cuttings have similar adventitious rooting competence, and result in plantlets with adequate morphophysiological quality, based upon leaf development, shoot height, stem diameter and length, and surface area, volume and diameter of roots. Single-bud mini-cuttings up to 2.5 cm long can thus be used to maximize production of mate plantlets by mini-cuttings.

Although pruning is important to obtain high-quality, large-diameter timber, the effects of pruning on nonstructural carbohydrates (NSC) in aboveground organs of many timber species are not well understood. Three intensities of pruning (none, moderate and severe) were tested on poplars (Populus alba ×  P. talassica) in the arid desert region of northwest China to compare the concentrations of soluble sugar (SS), starch (ST) and total nonstructural carbohydrate (TNC) in leaves, branches and trunks during the growing season. The concentration of NSC components after different pruning intensities varied similarly in seasonal patterns, increasing slowly at the beginning of the growing season, continuously declining in the middle, then gradually recovering by the end of the growing season. The monthly mean NSC concentration in poplar differed significantly among the three pruning intensities (p < 0.05). The SS concentration in pruned trees was higher than in unpruned trees (p < 0.05). For moderately pruned trees, the concentrations of ST and TNC in trunks and branches were higher than in unpruned and in severely pruned trees (p < 0.05). Compared with no pruning, pruning changed the seasonal variation in NSC concentration. The orders of SS and TNC concentrations in aboveground organs were leaf > branch > trunk, while the order of ST concentration was trunk > leaf > branch, which was related to functional differences of plant organs. The annual average growth in height of unpruned, moderately pruned, and severely pruned poplars was 0.21 ± 0.06, 0.45 ± 0.09 and 0.24 ± 0.05 m, respectively, and the annual average growth in DBH were 0.92 ± 0.04, 1.27 ± 0.06 and 1.02 ± 0.05 cm, respectively. Our results demonstrate that moderate pruning may effectively increase the annual growth in tree height and DBH while avoiding damage caused by excessive pruning to the tree body. Therefore, moderate pruning may increase the NSC storage and improve the growth of timber species.

Because overexpression of Vitreoscilla hemoglobin gene (Vgb) gene in plants can enhance tolerance to waterlogging, here Vgb was inserted into Populus alba ×  glandulosa to investigate its expression and effects on growth and physiological responses to waterlogging stress in the transgenic poplars. Southern blotting and RT-PCR analysis of Vgb-transgenic P. alba ×  glandulosa showed that the Vgb gene was integrated into the genome of the V13-81 and V13-85 transgenic lines and expressed. In greenhouse waterlogging stress tests, mortality of the transgenic poplar was significant lower than that of nontransgenic plants with increasing treatment time from 2 to 22 days. The transgenic plants had higher chlorophyll content and less chloroplast damage than in the control plants. Additionally, starch accumulation increased, and growth was enhanced in the transgenic plants, suggesting that the Vgb-expressing lines had improved energy reserves. Field trials of the transgenic poplar suggested that Vgb expression promotes growth and influences wood quality. Taken together, our results suggest that the expression of Vgb can increase the accumulation of chlorophyll and starch in the transgenic poplar, improve its ability to endure flooding, and improve growth and wood quality of the transgenic plants.

Populus euphratica Oliv., the Euphrates poplar, is the tallest tree species in the arid desert areas of Northwest China. Investigation of its drought-resistance genes is valuable to increase understanding of drought resistance mechanisms. RNA-seq of leaves and roots under drought simulation by 25% polyethylene glycol-6000 (PEG 6000) were performed at 0, 4, and 12 h. Leaves and roots responded differently to drought via differentially upregulated and downregulated genes; more genes were downregulated than upregulated in both leaves and roots. Additionally, these differentially expressed genes were enriched in different GO terms and KEGG pathways. For example, GO term ‘response to organic substance’ and KEGG pathway ‘nitrogen metabolism’ were enriched for drought-stressed leaves, while GO term ‘cell wall organization or biogenesis’ and KEGG pathway ‘zeatin biosynthesis’ were enriched for drought-stressed roots. The enrichment of the GO term ‘enzyme linked receptor protein signalling pathway’ in both leaf and root drought responses suggests that these tissues may also have similar mechanisms. However, roots under drought stress for four hs responded by activating programed cell death. The KEGG pathway ‘plant hormone signal transduction’ was detected for 4- and 12-h drought-stressed leaves and 12-h drought-stressed roots, suggesting that plant hormone signal transduction plays an important role in both roots and leaves. GO enrichment of upregulated and downregulated genes for leaves and roots reflect differentially regulatory mechanisms of response to drought stress via different biological processes such as the regulation of photosynthesis and auxin signalling pathway in leaves, and the regulation of defence response and water homeostasis in roots. Fifteen candidate genes, including transcription factors, protein kinase, transporter, late embryogenesis abundant protein and mannitol dehydrogenase, were further selected to determine their response to drought using qRT-PCR. The results show that the expression patterns of 13 of the 15 genes correspond to the RNA-seq results. This study provides new insights into the drought response mechanism of P. euphratica and suggests new candidate gene resources.

The application of phosphorus (P) and a water-retaining polymer to the soil can increase the availability of P for Cordia trichotoma, having a positive effect on the plants. The objective of this study was to evaluate the morphological, physiological and biochemical characteristics of C. trichotoma plants were cultivated in a red argisol and treated with 120, 240 and 360 kg P₂O₅ ha⁻¹ and no phosphorous addition as a control, in the presence (5 g L⁻¹ per seedling) and absence of a water-retaining polymer. Twenty-four months after planting, survival, height, stem diameter, shoot and root dry matter, leaf area, photosynthetic pigment concentration, chlorophyll a fluorescence, acid phosphatase enzyme activity (APase) and P in tissues and soil were determined. The polymer had no effect on survival and the other parameters. The addition of P increased growth, dry matter production, photosynthetic pigment concentrations, the use of light energy and maximum quantum yield of photosystem II. Plants cultivated in soil with 240 kg P₂O₅ ha⁻¹ application had 4.7 and 5.4 times more shoot and root dry matter, respectively, than control plants. This dosage also showed 52.1% greater photochemical energy use than the control plants. Plants cultivated without the addition of P showed higher activity of the APase enzyme.

A wood-based X-type lattice sandwich structure was manufactured by insertion-glue method. The birch was used as core, and Oriented Strand Board was used as panel of the sandwich structure. The short beam shear properties and the failure modes of the wood-based X-type lattice sandwich structure with different core direction (vertical and parallel), unit specification (120 mm × 60 mm and 60 mm × 60 mm), core size (50 mm and 60 mm), and drilling depth (9 mm and 12 mm) were investigated by a short beam shear test and the establishment of a theoretical model to study the equivalent shear modulus and deflection response of the X-type lattice sandwich structure. Results from the short beam shear test and the theoretical model showed that the failure modes of the wood-based X-type lattice sandwich structure were mainly the wrinkling and crushing of the panels under three-point bending load. The experimental values of deflection response of various type specimens were higher than the theoretical values of them. For the core direction of parallel, the smaller the unit specification is, the shorter the core size is, and the deeper the drilling depth is, the greater the short beam shear properties of the wood-based X-type lattice sandwich structure is.

The recent recognition that low doses of herbicides, human and veterinary antibiotics, metallic elements, micro/nano-plastics, and various other types of environmental pollutants widely enhance chlorophylls in the framework of hormesis created the need to further evaluate the response of photosynthetic pigments and gas exchange to low doses of stresses. An analysis of about 370 values of maximum stimulatory response (MAX; percentage of control response, %) of chlorophylls in higher plants, algae and duckweeds, and other photosynthesizing organisms, mined from published literatures, revealed a greater MAX for higher plants (median = 139.2%) compared to algae and duckweeds (median = 119.6%). However, an analysis of about 50 mined values of MAX of carotenoids revealed no significant difference in the median MAX between higher plants (median = 133.0%) and algae-duckweeds (median = 138.1%). About 70 mined values of MAX were also concentrated for photosynthetic rate (median MAX = 129.2%) and stomatal conductance (median MAX = 124.7%) in higher plants. Within higher plants, there was no significant difference in the median MAX among chlorophylls, carotenoids, photosynthetic rate, and stomatal conductance. Similarly, there was no significant difference in the median MAX between chlorophylls and carotenoids of pooled algae and duckweeds. The results suggest that the MAX is typically below 160% and as a rule below 200% of control response, and does not differ among chlorophylls, carotenoids, photosynthetic rate, and stomatal conductance. New research programs with improved experimental designs, in terms of number and spacing of doses within the “low-dose zone” of the hormetic dose–response relationship, are needed to study the molecular/genetic mechanisms underpinning the low-dose stimulation of photosynthesis and its ecological implications.