Forests, Volume 11, Issue 2 (February 2020) – 128 articles

Background and Objectives: Studying responses in woody plants upon water limitation is gaining importance due to the predicted increase in frequency and intensity of droughts in Europe. We studied the variation in radial growth and in wood anatomical traits caused by water limited growth conditions in offspring from Quercus petraea (Matt.) Liebl., Q. robur L. and their morphological intermediates grown in the same environment. Materials and Methods: Cross sections were prepared from the stems of 210 three-year-old potted seedlings, comprising control plants and seedlings that experienced from late spring until early autumn of the first growing season two sequential periods of water with-holding each followed by plentiful re-watering. Pith radius, ring width of the three growing seasons and latewood vessel diameter in second and third growing season were measured. Presence of intra-annual density fluctuations, dendritic patterns of latewood vessels and the level of ring closure of earlywood vessels were observed. The traits were modelled to examine the explanatory power of the taxon of the mother tree and the drought treatment. Results: Most of the traits displayed significant differences between offspring from Q. petraea and Q. robur and offspring from the morphological intermediates behaved inconsistent among the traits. Most of the traits were significantly affected by the drought stress in the first growing season. Apart from radial growth, also latewood vessel size was reduced in the two growing seasons following the year in which drought was imposed on the seedlings, suggesting an adaptation to improve the tolerance to drought stress. We also found an indication for a compensation growth mechanism, counteracting the lost growing time during the drought stress, as the level of ring closure of the earlywood vessels in the year following the drought treatment was further advanced in the treated seedlings, an effect that disappeared in the subsequent year. Conclusion: Oaks exposed to drought adapt their growth and xylem structure to improve drought resistance. While youth growth of Q. robur is more competition-oriented, with a faster juvenile growth, Q. petraea seems to invest more in a precautious growth, being more prepared for stressful conditions. It is therefore possible that Q. robur seedlings may suffer more from intensified droughts than Q. petraea seedlings. Full article

Although professional chainsaws have come a long way regarding technical and ergonomic development since first introduced into forestry, they still remain a high-risk tool that can cause serious health problems. In this research, three types of used professional chainsaws were observed regarding harmful vibrations they emit and possible connection to years in use, chainsaw type, characteristics and level of vibrations. Measurements were performed in accordance with the recommendations of ISO 5349:2001. For the measurements, a measuring chain consisting of a triaxial accelerometer manufactured by Bruel & Kjaer and a vibrometer of the same manufacturer Type 4447. To evaluate the emitted vibrations, a daily exposure value A(8) was used. Exposure durations to predefined working operations were identical for every used chainsaw to enable the possibility of equal comparability. Obtained results indicate that the daily vibration exposure A(8) is not affected by the years in use of the chainsaw. Results also show that the power and chainsaw type have an influence on daily vibration exposure. The recommendation for the praxis is to use even lighter and smaller chainsaw wherever is possible. Full article

Plantations support local economies and rural livelihoods in many mountainous regions, where poverty and a fragile environment are often interlinked. Managing plantations sustainably and alleviating poverty is a major challenge. This study reports on the findings of a household livelihood survey in the central mountainous region of Hainan Island, a global biodiversity hotspot. The survey aimed to identify rural household livelihoods, strategies to lift rural households out of poverty and potential environmental consequences of different livelihood strategies. Households were divided into five groups based on their main source of income: plantations, crops, livestock, local off-farm income and remittances. Plantations were the main source of income for 74% of households and provided 46% of the total income. Plantation land area, planting diverse tree species and intercropping were significantly associated with higher income. Reallocating land by family size could increase the proportion of households above the poverty line in the plantation group from 51.3% to 85.3%, while making only 3.3% of households worse off. Lower income households tended to apply more chemicals to plantations, which suggests that they create more strain on the environment. Improving household income through dynamically allocating plantation land and diversifying planted species could therefore be beneficial both socially and environmentally. Our results emphasize the importance of dynamic plantation land allocation and diverse plantation planting in poverty alleviation and environmental sustainability. Full article

The development of plant and soil microbial communities is one of the basic preconditions for the restoration of functional ecosystems. However, nutrients are concurrently used by plants and microbes, and the dynamics of this interaction during ecosystem development have seldom been studied. The aim of our study, thus, was to describe the dynamics of nutrient availability in soil and, at the same time, the nutrient accumulation in plant and microbial biomass along an unassisted primary succession heading toward broadleaf forest. The growth of the understory plant Arrhenatherum elatius on soils originating from three (16, 22, and 45 years’ old) successional stages of a post-mining area and the development of the microbial community in the presence or absence of this plant were studied in a pot experiment. Both, the plant biomass and carbon (C) in microbial biomass in intermediate and late middle successional stages were higher than those in the early stage. In soil, extractable organic C, extractable organic nitrogen (N), and inorganic N increased with proceeding succession, but Olsen phosphorus (P) peaked in the intermediate successional stage. The amounts of N and P in plant and microbial biomass increased during succession. In the late middle successional stage, the amount of P in microbial biomass exceeded that of plant bound P approximately twice, and this increase was higher in pots with plants than without. The results imply that the competition between plants and microbes for available P may increase microbial P uptake and, thus, hinder plant growth in later successional stages. Full article

The leaves of vines exhibit a high degree of variability in shape, from simple oval to highly dissected palmatifid leaves. However, little is known about the extent of leaf bilateral symmetry in vines, how leaf perimeter scales with leaf surface area, and how this relationship depends on leaf shape. We studied 15 species of vines and calculated (i) the areal ratio (AR) of both sides of the lamina per leaf, (ii) the standardized symmetry index (SI) to estimate the deviation from leaf bilateral symmetry, and (iii) the dissection index (DI) to measure leaf-shape complexity. In addition, we examined whether there is a scaling relationship between leaf perimeter and area for each species. A total of 14 out of 15 species had no significant differences in average ln(AR), and mean ln(AR) approximated zero, indicating that the areas of the two lamina sides tended to be equal. Nevertheless, SI values among the 15 species had significant differences. A statistically strong scaling relationship between leaf perimeter and area was observed for each species, and the scaling exponents of 12 out of 15 species fell in the range of 0.49−0.55. These data show that vines tend to generate a similar number of left- and right-skewed leaves, which might contribute to optimizing light interception. Weaker scaling relationships between leaf perimeter and area were associated with a greater DI and a greater variation in DI. Thus, DI provides a useful measure of the degree of the complexity of leaf outline. Full article

Auxins have long been implicated in many aspects of plant growth and development. Auxin response factors (ARFs) are important proteins in auxin-mediated pathways and they play key roles in plant physiological and biochemical processes, including flower development. Endogenous indoleacetic acid (IAA) levels were measured and ARFs were studied in the flowers during the developmental stages in order to further elucidate the role of auxin in flower development of Osmanthus fragrans. A systematic analysis of OfARFs was conducted by carrying out a genome-wide search of ARFs. A total of 50 ARF genes (OfARFs) were detected and validated from the Osmanthus fragrans genome. Furthermore, a comprehensive overview of the OfARFs was undertaken, including phylogenetic relationship, gene structures, conserved domains, motifs, promoters, chromosome locations, gene duplications, and subcellular locations of the gene product. Finally, expression profiling, while using transcriptome sequencing from a previous study and quantitative real-time PCR (qRT-PCR), revealed that many OfARF genes have different expression levels in various tissues and flower developmental stages. By comparing the expression profiles among the flower developmental stages, and the relationship between ARFs and endogenous IAA levels, it can be supposed that OfARFs function in flower development of O. fragrans in an auxin-mediated pathway. Full article

National forest inventories in many countries combine expensive ground plot data with remotely-sensed information to improve precision in estimators of forest parameters. A simple post-stratified estimator is often the tool of choice because it has known statistical properties, is easy to implement, and is intuitive to the many users of inventory data. Because of the increased availability of remotely-sensed data with improved spatial, temporal, and thematic resolutions, there is a need to equip the inventory community with a more diverse array of statistical estimators. Focusing on generalized regression estimators, we step the reader through seven estimators including: Horvitz Thompson, ratio, post-stratification, regression, lasso, ridge, and elastic net. Using forest inventory data from Daggett county in Utah, USA as an example, we illustrate how to construct, as well as compare the relative performance of, these estimators. Augmented by simulations, we also show how the standard variance estimator suffers from greater negative bias than the bootstrap variance estimator, especially as the size of the assisting model grows. Each estimator is made readily accessible through the new R package, mase. We conclude with guidelines in the form of a decision tree on when to use which an estimator in forest inventory applications. Full article

Chinese pine (Pinus tabuliformis Carr.) is the main forest species in northern China, with the potential to dramatically affect biotic and abiotic aspects of ecosystems in this region. To discover the rainfall partitioning patterns of different growth periods of Chinese pine forest, we studied the throughfall (Tf), stemflow (Sf) and canopy interception (I) in three stand ages (40-, 50-, 60-year-old) in Liaoheyuan Natural Reserve of Hebei Province during the growing seasons of 2013 and 2014, and analyzed effect of rainfall amount, rainfall intensity, and canopy structure on rainfall partitioning in Chinese pine forest. The results showed that throughfall decreased with the stand age, accounting for 78.8%, 74.1% and 66.7% of gross rainfall in 40-, 50- and 60-year-old Chinese pine forests, respectively. Canopy interception, on the other hand, increased with the stand age (20.4%, 24.8%, and 32.8%, respectively), while the pattern in stemflow was less clear (0.8%, 1.1%, and 0.6%, respectively). As rainfall intensity increased, the Tf and Sf increased and I declined. Additionally, our results showed that leaf area index (LAI) and the diameter at breast height (DBH) increased with age in Chinese pine stands, probably explaining the similar increase in canopy interception (I). On the other hand, the mean leaf angle, openness, gap fraction all decreased with the stand age. Stepwise regression analysis showed that the rainfall amount and LAI were the major determinants influencing the rainfall partition. Our study highlights the importance of stand age in shaping different forest canopy structures, and shows how age-related factors influence canopy rainfall partitioning. This study also significantly adds to our understanding the mechanisms of the hydrological cycle in coniferous forest ecosystems in northern China. Full article

Slash-and-burn is a farming practice of the indigenous communities in the Himalayan foothills of Nepal. The traditional land-tenure system is based on a customary oral tradition. However, the government’s persistent denial of land rights has fueled the indigenous conflicts in the last few decades. Deliverance of scientific evidence-based arguments may underpin the ongoing conflict-resolution dialogues between the authorities and the indigenous communities. Dating growth rings of trees in a slash-and-burn system might help the indigenous people to find evidence of their historic land uses in the mountainous landscape. In this pilot study, we examined the potential of Diploknema butyracea (Roxb.) H. J. Lam growth rings for documenting land use history of Nepalese indigenous farming practices, as this species is being preserved during the slash-and-burn practices. The species is an economically important and ecologically interesting (as it flushes leaves when everything is dry, and sheds leaves while everything is green) deciduous tree species belonging to Sapotaceae family and widely distributed in Sub-Himalayan tracts. Five stem discs were studied which were originated from the Kandrang valley of the Chitwan district, Nepal. For the first time, we revealed distinct growth rings in this species which are marked by fibers with thicker cell walls. Growth-ring anomalies, i.e., wedging and partially missing rings, were also found. Four out of five samples could be crossdated at a marginal level (GLK ≥ 60 and t ≥ 2.0) which is a confirmation of the annual nature of growth rings. One of the samples showed black spots of oxidized wood which are traces of fire, suggesting evidence of slash-and-burn practices in the study area since 1933. This study suggests a strong potential of D. butyracea for growth-ring analysis to reconstruct indigenous land use history in Nepal. Full article

Accurate measurement of the tree height and canopy cover density is important for forest biomass and management. Recently, Light Detection and Ranging (LIDAR) and Unmanned Aerial Vehicle (UAV) images have been used to estimate the tree height and canopy cover density for a forest stands. More so, UAV systems with autopilot functions, affordable Global Navigation Satellite System (GNSS) and Inertial Measurement Unit (IMU) have created new possibilities, aided by available photogrammetric programs. In this study, we investigated the possibility of data collection methods using an Aerial LIDAR Scanner (ALS) and an UAV together with a fieldworks to evaluate accurate the tree standard metrics in Singyeri, Gyeongjusi, and Gyeongsangbukdo province. The derived metrics via statistical analyses of the ALS and UAV data and validated by field measurements were compared to a published forest type map (scale 1:5000) by the Korea Forest Service; geared towards improving the forest attributes. We collected data and analyzed and compared them with existent the forest type map produced from an aerial photographs and a digital stereo plotter. The ALS data of around 19.5 points·m^–2 were collected by an airplane, then processed and classified using the LAStools; while about 362 images of the UAV were processed via Structure from Motion algorithm in the Agisoft Metashape Pro. Thus, we calculated the metrics using the point clouds of both an ALS and an UAV, and then verified their similarity. The fieldwork was manually done on 110 sampled trees. Calculated heights of the UAV were 3.8~5.8 m greater than those for the ALS; and when correlated with the fieldwork, the UAV data overestimated, while the maximum height of the ALS data was more accurate. For the canopy cover, the ALS computed canopy cover was 10%~30% less than that of the UAV. However, the canopy cover above 2 m by an UAV was the best measurement for a forest canopy. Therefore, these results assert that the examined techniques are robust and can significantly complement methods of the conventional data acquisition for the forest type map. Full article

Background and Objectives: The continuous increase in the amount of atmospheric CO₂ is a factor that significantly contributes to global warming. Forests can be used to mitigate climate change by absorbing carbon and storing it. Scots pine (Pinus sylvestris L.) is the most abundant tree species in Polish forests and can substantially aid carbon accumulation. The aim of the study was to determine the carbon content in the dry mass of various parts of Scots pine trees and to evaluate the relationship between the accumulation of carbon in aboveground tree biomass and some stand parameters. Materials and Methods: The research was carried out in 20 even-aged (81–90 years old) Scots pine stands in northwestern Poland (Drawno Forest District). The densities of these stands ranged from 476 to 836 trees per hectare. The aboveground biomass was calculated as the sum of the following tree compartments: stem (wood and bark), dead branches, thick branches, thin branches and needles. The carbon content and storage in these compartments was determined. Results: The mean carbon content was lowest in stem wood (47.0%) and highest in needles (50.3%). No correlation between the stand density and the level of carbon stored in the aboveground biomass of Scots pines was found. Full article

Shorea platyclados (Dark Red Meranti) is a commercially important timber tree species in Southeast Asia. However, its stocks have dramatically declined due, inter alia, to excessive logging, insufficient natural regeneration and a slow recovery rate. Thus, there is a need to promote enrichment planting and develop effective technique to support its rehabilitation and improve timber production through implementation of Genome-Wide Association Studies (GWAS) and Genomic Selection (GS). To assist such efforts, plant materials were collected from a half-sib progeny population in Sari Bumi Kusuma forest concession, Kalimantan, Indonesia. Using 5900 markers in sequences obtained from 356 individuals, we detected high linkage disequilibrium (LD) extending up to >145 kb, suggesting that associations between phenotypic traits and markers in LD can be more easily and feasibly detected with GWAS than with analysis of quantitative trait loci (QTLs). However, the detection power of GWAS seems low, since few single nucleotide polymorphisms linked to any focal traits were detected with a stringent false discovery rate, indicating that the species’ phenotypic traits are mostly under polygenic quantitative control. Furthermore, Machine Learning provided higher prediction accuracies than Bayesian methods. We also found that stem diameter, branch diameter ratio and wood density were more predictable than height, clear bole, branch angle and wood stiffness traits. Our study suggests that GS has potential for improving the productivity and quality of S. platyclados, and our genomic heritability estimates may improve the selection of traits to target in future breeding of this species. Full article

Although numerous studies have demonstrated the toxic effects of fine particulates less than 2.5 µm (PM_2.5) on the health of humans, little information is available on the ecotoxicity of PM_2.5. Water-soluble inorganic ions (WSII, including Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, NO₃⁻, and SO₄²⁻) can compose more than 60% of PM_2.5. To better understand the possible impacts of WSII-PM_2.5 on leaf litter decomposition, we conducted an experiment in which two leaf litters from oak (Quercus variabilis) and pine (Pinus massoniana) dominant forests in subtropical China were incubated in microcosms containing their respective forest soils and treated with WSII-PM_2.5. Our results showed that, after six-months of decomposition, the WSII-PM_2.5 treatments inhibited leaf litter decomposition rates, carbon and nitrogen loss, microbial biomass, and enzyme activities in the two forests. In addition, higher WSII-PM_2.5 concentration led to stronger negative effects. Comparative analysis showed that the negative effects of WSII-PM_2.5 on oak forest were greater than on pine forest, relating to the higher susceptibility to changes of soil microenvironment in oak forests. WSII-PM_2.5 may influence decomposition through soil acidification and salinization, which could also cause a sub-lethal depression in soil isopod activity. However, in the first month of decomposition, mass loss of the oak and pine leaf litters under the low concentration WSII-PM_2.5 were 21.63% and 35.64% higher than that under the control, respectively. This suggests that transitory low concentrations of WSII-PM_2.5 have a promoting effect on decomposition. Long-term PM_2.5 exposure, therefore, may have profound ecosystem consequences by altering the balance of ecosystem carbon flux, nutrient cycling, and humus formation in the future. Full article

Humid boreal forests are unique environments characterized by a cold climate, abundant precipitation, and high evapotranspiration. Transpiration ( $E_T$ ), as a component of evapotranspiration (E), behaves differently under wet and dry canopy conditions, yet very few studies have focused on the dynamics of transpiration to evapotranspiration ratio ( $E_T/E$ ) under transient canopy wetness states. This study presents field measurements of $E_T/E$ at the Montmorency Forest, Québec, Canada: a balsam fir boreal forest that receives $\sim 1600$ mm of precipitation annually (continental subarctic climate; Köppen classification subtype Dfc). Half-hourly observations of E and $E_T$ were obtained over two growing seasons using eddy-covariance and sap flow (Granier’s constant thermal dissipation) methods, respectively, under wet and dry canopy conditions. A series of calibration experiments were performed for sap flow, resulting in species-specific calibration coefficients that increased estimates of sap flux density by $34\%\pm 8\%$ , compared to Granier’s original coefficients. The uncertainties associated with the scaling of sap flow measurements to stand $E_T$ , especially circumferential and spatial variations, were also quantified. From 30 wetting–drying events recorded during the measurement period in summer 2018, variations in $E_T/E$ were analyzed under different stages of canopy wetness. A combination of low evaporative demand and the presence of water on the canopy from the rainfall led to small $E_T/E$ . During two growing seasons, the average $E_T/E$ ranged from $35\%\pm 2\%$ to $47\%\pm 3\%$ . The change in total precipitation was not the main driver of seasonal $E_T/E$ variation, therefore it is important to analyze the impact of rainfall at half-hourly intervals. Full article

This article is a broad review focused on dragon trees—one of the most famous groups of trees in the world, well known from ancient times. These tertiary relicts are severely endangered in most of the area where they grow. The characteristic features of the dragon tree group are described and the species belonging to this group are listed. This review gathers together current knowledge regarding the taxonomy, evolution, anatomy and morphology, physiology, and ontogeny of arborescent dragon tree species. Attention is also paid to the composition, harvesting, medicinal, and ethnobotanical use of the resin (dragons’ blood). An evaluation of population structure, distribution, ecology, threats, and nature conservation forms the final part of the review. In the conclusions we recommend further avenues of research that will be needed to effectively protect all dragon tree species. Full article

Atmospheric nitrogen (N) and acid deposition have become global environmental issues and are likely to alter soil respiration (R_s); the largest CO₂ source is from soil to the atmosphere. However, to date, much less attention has been focused on the interactive effects and underlying mechanisms of N and acid deposition on R_s, especially for ecosystems that are simultaneously subjected to elevated levels of deposition of both N and acid. Here, to examine the effects of N addition, acid addition, and their interactions with R_s, we conducted a two-way factorial N addition (control, CK; 60 kg N ha⁻¹ a⁻¹, LN; 120 kg N ha⁻¹ a⁻¹, HN) and acid addition (control, CK; pH 4.5, LA; pH 2.5, HA) field experiment in a subtropical plantation in China. Our results showed the following: (1) During the one-year observation period, the seasonal dynamics of R_s presented a single peak curve model, which was closely related to the surface soil temperature. (2) The simulated N deposition and acid deposition significantly decreased the R_s in the subtropical plantation. Compared to the CK plots, the LN and HN treatments reduced the annual mean values of R_s by 41% and 56%, and the annual mean values of R_s were inhibited by 26% and 31% in the LA and HA plots. The inhibition of N application on R_s was stronger than that of the simulated acid deposition. (3) Significant interactions between N addition and acid addition on R_s were detected, and R_s was significantly inhibited under four co-addition treatments. (4) The underlying mechanism and main reason for the responses of R_s to simulated N and acid deposition in this study might be the inhibition of soil microbial biomass and soil enzyme activity due to soil acidification under increased N and acid input. Full article

This study investigates how certain forest soil properties influence the propensity of beech forests to windthrow disturbances. The field measurements of soil electrical resistivity were carried out in an old-growth natural beech forest where the soil has developed from Cainozoic sedimentary rock with mudstone–claystone stratigraphy. In 2014, the forest was hit by a severe windstorm, and dispersed windthrow occurred at certain plots. Apparent electrical resistivity measurements were performed to investigate whether some soil properties could influence the forest trees’ predisposition to windthrow. The increases in the clay content and soil bulk density below 30 cm were associated with weathered claystone and mudstone, which created a physiological barrier for deeper root penetration. The result of the ${\chi }^2$ test suggested that the windthrown spots were not distributed evenly over the entire study area. They were mainly concentrated over approximately 50% of the area, and their positions coincided with low resistivity values, indicating low soil skeleton content, high clay content and soil moisture. Therefore, electrical resistivity tomography could be considered a useful predictive tool for reducing the risk of natural disturbances by preventive forest management. Full article

Research Highlights: We detected the longitudinal gradients of genetic diversity parameters, such as the number of alleles, effective number of alleles, heterozygosity, and inbreeding coefficient, and found that these might be attributable to climatic conditions, such as temperature and snow depth. Background and Objectives: Genetic diversity among local populations of a plant species at its distributional margin has long been of interest in ecological genetics. Populations at the distribution center grow well in favorable conditions, but those at the range margins are exposed to unfavorable environments, and the environmental conditions at establishment sites might reflect the genetic diversity of local populations. This is known as the central-marginal hypothesis in which marginal populations show lower genetic variation and higher differentiation than in central populations. In addition, genetic variation in a local population is influenced by phylogenetic constraints and the population history of selection under environmental constraints. In this study, we investigated this hypothesis in relation to Abies sachalinensis, a major conifer species in Hokkaido. Materials and Methods: A total of 1189 trees from 25 natural populations were analyzed using 19 EST-SSR loci. Results: The eastern populations, namely, those in the species distribution center, showed greater genetic diversity than did the western peripheral populations. Another important finding is that the southwestern marginal populations were genetically differentiated from the other populations. Conclusions: These differences might be due to genetic drift in the small and isolated populations at the range margin. Therefore, our results indicated that the central-marginal hypothesis held true for the southernmost A. sachalinensis populations in Hokkaido. Full article

In recent decades, airborne allergens for allergic respiratory diseases have been found to increase significantly by a process of converting coniferous forests into broad-leaved forests in Korea. This study was conducted to evaluate factors, including airborne pollen counts, micromorphology, and flowering phenology, that can affect oak pollen-related allergic symptoms. The catkin of Mongolian oak (Quercus mongolica Fisch. ex Ledeb.) showed the most rapidly blooming catkin on Julian day 104 in flower development. Among six species, the last flowering was observed on Julian day 119 in Korean oak (Quercus dentata Thunb.). The pollen dispersal was persisted for about 32 days from Julian day 104 to Julian day 136. Airborne pollen was observed about 2 weeks after flowering phase H, the senescence phase. Pollen size varied by species, with the largest from Q. mongolica (polar axis length, PL = 31.72 µm, equatorial axis length, EL = 39.05 µm) and the smallest from Jolcham oak (Quercus serrata Murray) (PL = 26.47 µm, EL = 32.32 µm). Regarding pollen wall structure, endexine of Q. dentata was coarsely laminated or fragmented. The endexine thicknesses of Sawtooth oak (Quercus acutissima Carruth.) and Q. serrata were thick and stable, whereas Galcham oak (Quercus aliena Blume), Q. mongolica, and Oriental cork oak (Quercus variabilis Blume) had thinner endexines. The area occupied by pollenkitt of Q. variabilis was significantly larger than that of Q. acutissima. Importantly, Q. variabilis had a distinctly thick 17 kDa protein band, a presumed major allergen. Oak species differ in pollen protein composition, and thus there is a possibility that the allergenic activity of pollen proteins vary depending on oak species. This study highlights the fact that native oak species in Korea differ in flowering pattern of male flowers, pollen morphology, and pollen chemical constituents. These discrepancies in flowering and pollen properties imply variable allergic responses to oak pollen from different species. Full article

Clearing of understory plants is a common management method in plantation forests, but its long-term impact on soil properties and understory plant diversity is still poorly understood. In order to uncover the potential relationship between understory diversity and soil properties, we categorized understory plants into herbs and shrubs, and took soil depth into consideration. We measured the soil variables and investigated the understory plant diversity in four stand age-classes (9-year-old for young, 18-year-old for intermediate, 28-year-old for near-mature, and 48-year-old for mature) in a Pinus massoniana plantation. We aimed to examine how the diversity of herbs and shrubs changed with stand succession and to determine which of the three soil depths (0–10 cm, 10–20 cm, 20–40 cm) had the strongest explanation for the understory plant diversity. Furthermore, structural equation modeling (SEM) was performed to assess the direct and indirect effect of understory clearing and stand age on understory diversity. We found that understory clearing influenced the trend of diversity of herbs and shrubs with stand age, and understory diversity showed a strong correlation with soil physical properties in all three soil layers. The soil properties in the 10–20 cm soil layer related with the diversity of herbs and shrubs most, while the 20–40 cm soil layer properties related with them the least. Understory clearing reduced soil available phosphorus (AP). Understory clearing and stand age were found to benefit understory plant diversity directly and decreased the understory diversity indirectly via AP. Consequently, to improve our understanding of the impact of understory clearing and stand age on biodiversity, we should take into account its direct and indirect effects. Full article

An object detection method of ground-penetrating radar (GPR) signals using empirical mode decomposition (EMD) and dynamic time warping (DTW) is proposed in this study. Two groups of timber specimens were examined. The first group comprised of Douglas fir (Pseudotsuga menziesii) timber sections prepared in the laboratory with inserts of known internal characteristics. The second group comprised of timber girders salvaged from the timber bridges on historic Route 66 over 80 years. A GSSI Subsurface Interface Radar (SIR) System 4000 with a 2 GHz palm antenna was used to scan these two groups of specimens. GPR sensed differences in dielectric constants (DC) along the scan path caused by the presence of water, metal, or air within the wood. This study focuses on the feature identification and defect classification. The results show that the processing methods were efficient for the illustration of GPR information. Full article

Albino tea mutants with specific shoot colors (white or yellow) have received increasing attention from researchers due to their unique phenotypes, beneficial metabolites, and special flavor. In this study, novel natural yellow leaf mutants of the same genetic background of “Rougui” were obtained, and the transcriptome and metabolite profiles of the yellow leaf mutant (YR) and original green cultivar (GR) were investigated. A total of 130 significantly changed metabolites (SCMs) and 55 differentially expressed genes (DEGs) were identified in YR compared to GR. The leaf coloration of YR was primarily affected by pigment metabolism including of chlorophyll, carotenoids, and flavonoids, and the co-expression of three heat shock proteins (HSPs) and four heat shock transcription factors (HSFs) may also regulate leaf coloration by affecting chloroplast biogenesis. Of the 130 SCMs, 103 showed clearly increased abundance in YR, especially nucleotides and amino acids and their derivatives and flavonoids, suggesting that YR may be an ideal albino tea germplasm for planting and breeding. Our results may help to characterize the leaf coloration and metabolic mechanism of albino tea germplasm. Full article

This paper is devoted to the application of the modelling approach, as one of the methods for the evaluation of thermal comfort, to neighborhoods located in two cities characterized by a different climate, i.e., a Mediterranean city in southern Italy (Lecce) and a northern European city in southern Finland (Lahti). The impact of the presence of vegetation in both places is evaluated and compared, further considering alternative scenarios for thermal comfort improvement. The thermal comfort condition is expressed in terms of indices (mean radiant temperature (MRT) and predicted mean vote (PMV)). Results show that at pedestrian level the presence of vegetation lead to an improvement of thermal comfort in summer of about 2 points in both neighborhoods. This improvement is also evident observing the spatial distribution of MRT with a difference of 7 °C in the Lecce neighborhood and 3 °C in Lahti. In winter, thermal discomfort is observed in the presence of vegetation with a difference of 1.3 °C in the Lecce neighborhood and 1.5 °C in Lahti in terms of MRT. However, trees and green cover have the important potential to offset climate change impact and to make urban environments less thermally stressful. This study aims to guide urban planners towards a motivated and necessary transaction towards new green infrastructure whose effect should, however, be analyzed and investigated case by case. Full article

Climate, topography, and tree structure have different effects on plant diversity that vary with spatial scale. In this study, we assessed the contribution of these drivers and how they affect the vascular plant richness of different functional groups in a temperate forest ecosystem in Northeast China. We investigated about 0.986 million plants from 3160 sites to quantify the impact of annual mean temperature, sunshine duration, annual precipitation, standard deviation of diameter at breast height, and forest type on richness of vascular plants (total species, tree, treelet, shrub, and herb, separately) using the gradient boosting model. The results show that annual mean temperature had the strongest impact on plant richness. The tree richness peaked at intermediate annual mean temperature and sunshine duration and increased with annual precipitation. The Shannon diversity index and Simpson dominance index increased with annual precipitation and standard deviation of diameter at breast height, decreased with sunshine duration, and peaked at intermediate annual mean temperature and forest type. The total richness and understory richness increased with annual mean temperature and standard deviation of diameter at breast height and peaked at intermediate sunshine duration and annual precipitation. A comprehensive mechanism was found to regulate the plant diversity in forest ecosystems. The relationship between tree richness and annual mean temperature with latitudinal effect could be affected by the differences in number and size of tree individuals, indicating that plant diversity varies with the utilization of energy. The force driving plant richness varied with the functional group due to the different environmental resource requirements and the life history strategies of plants layers. Full article

The weakness of the population matrix models is that they do not take into account the variation inside the class. In this study, we introduce an approach to add height variation of the trees to the diameter-structured matrix models. In this approach, a new sub-model that describes the height growth of the trees is included in the diameter-structured model. We used this height- and diameter-structured matrix model to maximize the net present value (NPV) for the remaining part of the ongoing rotation for Scots pine (Pinus sylvestris L.) stand and studied how the height variation affects to the results obtained through stand-level optimization. In the optimization, the height variation was taken into account by setting the lower saw-log price for the short trees. The results show that including the height variation into the optimization reduced the financial outcome by 16–18% and considerably changed the structure of optimal management (e.g., timings for thinnings, rotation period and intensity of thinnings). We introduced an approach that can be applied to include not only height variation but also variation of other tree properties (such as branchiness or the amount of heartwood and sapwood) into the matrix models. Full article

Tectona grandis is a valuable timber species with heartwood that is used worldwide. Most of the previous studies on its heartwood and sapwood have focused on dominant or mean trees, while trees with different social status might show different vertical and horizontal distributions of heartwood and sapwood. Studies on their heartwood and sapwood properties could be conducive to increasing heartwood yield at stand level. In 31-year-old plantations of T. grandis in southwest Guangxi, China, the trees were divided into three groups including dominant, mean and suppressed trees. Stem analysis was conducted for sampled trees in each of these groups to explore the differences in the horizontal and vertical distribution of their heartwood and sapwood. The results indicated that the heartwood radius, heartwood and sapwood areas of T. grandis showed significant differences in horizontal and vertical directions among trees of different social status. Heartwood began to form when xylem radius was 2–3 cm, and the heartwood radius ratio tended to be stable when the xylem radius reached about 8 cm. Heartwood radius and area, sapwood area and section heartwood volume all decreased with increasing tree height. The ratios of heartwood radius and area were relatively stable for sections under 50% of tree height. The sapwood width did not vary largely in horizontal and vertical directions among the three social status tree groups, which mainly fluctuated in the range of 1–4 cm. The heartwood volume proportions for dominant, mean and suppressed trees were 60%, 55% and 51%, respectively. There was a significant exponential relationship between heartwood volume and diameter at breast height (DBH) regardless of social status. The model HV = 0.000011 × DBH^2.9787 (R² = 0.8601) could accurately estimate heartwood volume for all T. grandis with different social statuses at this age. These findings could provide evidence for stand management and high-quality and large-sized timber production of T. grandis. Full article

Due to the long time horizon typically characterizing forest planning, uncertainty plays an important role when developing forest management plans. Especially important is the uncertainty related to recently human-induced global warming since it has a clear impact on forest capacity to contribute to biogenic and anthropogenic ecosystem services. If the forest manager ignores uncertainty, the resulting forest management plan may be sub-optimal, in the best case. This paper presents a methodology to incorporate uncertainty due to climate change into forest management planning. Specifically, this paper addresses the problem of harvest planning, i.e., defining which stands are to be cut in each planning period in order to maximize expected net revenues, considering several climate change scenarios. This study develops a solution approach for a planning problem for a eucalyptus forest with 1000 stands located in central Portugal where expected future conditions are anticipated by considering a set of climate scenarios. The model including all the constraints that link all the scenarios and spatial adjacency constraints leads to a very large problem that can only be solved by decomposing it into scenarios. For this purpose, we solve the problem using Progressive Hedging (PH) algorithm, which decomposes the problem into scenario sub-problems easier to solve. To analyze the performance of PH versus the use of the extensive form (EF), we solve several instances of the original problem using both approaches. Results show that PH outperforms the EF in both solving time and final optimality gap. In addition, the use of PH allows to solve the most difficult problems while the commercial solvers are not able to solve the EF. The approach presented allows the planner to develop more robust management plans that incorporate the uncertainty due to climate change in their plans. Full article

High-value timber species such as monarch birch (Betula maximowicziana Regel), castor aralia (Kalopanax septemlobus (Thunb.) Koidz), and Japanese oak (Quercus crispula Blume) play important ecological and economic roles in forest management in the cool temperate mixed forests in northern Japan. The accurate measurement of their tree height is necessary for both practical management and scientific reasons such as estimation of biomass and site index. In this study, we investigated the similarity of individual tree heights derived from conventional field survey, digital aerial photographs derived from unmanned aerial vehicle (UAV-DAP) data and light detection and ranging (LiDAR) data. We aimed to assess the applicability of UAV-DAP in obtaining individual tree height information for large-sized high-value broadleaf species. The spatial position, tree height, and diameter at breast height (DBH) were measured in the field for 178 trees of high-value broadleaf species. In addition, we manually derived individual tree height information from UAV-DAP and LiDAR data with the aid of spatial position data and high resolution orthophotographs. Tree heights from three different sources were cross-compared statistically through paired sample t-test, correlation coefficient, and height-diameter model. We found that UAV-DAP derived tree heights were highly correlated with LiDAR tree height and field measured tree height. The performance of individual tree height measurement using traditional field survey is likely to be influenced by individual species. Overall mean height difference between LiDAR and UAV-DAP derived tree height indicates that UAV-DAP could underestimate individual tree height for target high-value timber species. The height-diameter models revealed that tree height derived from LiDAR and UAV-DAP could be better explained by DBH with lower prediction errors than field measured tree height. We confirmed the applicability of UAV-DAP data for obtaining the individual tree height of large-size high-value broadleaf species with comparable accuracy to LiDAR and field survey. The result of this study will be useful for the species-specific forest management of economically high-value timber species. Full article

Research Highlights: I sought to disentangle the influences of tree age, growth rate, and dwarf mistletoe infection on resin duct defenses in lodgepole pine, Pinus contorta Douglas ex Loudon, revealing the presence of direct positive and indirect negative effects of mistletoe on defenses. Background and Objectives: For protection against natural enemies, pines produce and store oleoresin (resin) in ‘resin ducts’ that occur throughout the tree. Dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm. (hereafter “mistletoe”), is a widespread parasitic plant affecting the pines of western North America. Infection by mistletoe can suppress pine growth and increase the probability of insect attack—possibly due to a reduction in resin duct defenses or in the potency of chemical defenses at higher levels of mistletoe infection, as reported in Pinus banksiana Lamb. However, the influence of mistletoe infection on defenses in other pine species remains unclear. I hypothesized that mistletoe infection would induce greater resin duct defenses in P. contorta while simultaneously suppressing annual growth, which was expected to reduce defenses. Materials and Methods: Using increment cores from P. contorta trees occurring in a subalpine forest of Colorado, USA, I quantified tree age, annual growth, annual resin duct production (#/annual ring), and cross-sectional area (mm² of resin ducts/annual ring). Results: Mistletoe infection increased with tree age and had a direct positive relationship with resin duct defenses. However, mistletoe infection also had an indirect negative influence on defenses via the suppression of annual growth. Conclusions: Through the combined direct and indirect effects, mistletoe infection had a net positive impact on resin duct production but a net negative impact on the total resin duct area. This finding highlights the complexity of pine defense responses to natural enemies and that future work is needed to understand how these responses influence overall levels of resistance and the risk of mortality. Full article

Research Highlights: Our study highlights a new, simple, and effective method for studying the habitat use by beavers in Canadian boreal forests. Information regarding the presence of beaver colonies and their habitat occupation is essential for proper forest management and damage prevention in the boreal forest. Background and Objectives: The North American beaver (Castor canadensis) is a major element of natural disturbance, altering the dynamics and structure of boreal forest landscapes. Beaver-related activities also affect human infrastructure, cause floods, and lead to important monetary losses for forestry industries. Our study aimed to determine the spatiotemporal patterns of beaver occupation of lodges over time. Materials and Methods: Using a dendroecological approach to date browsing activity, we studied the occupation of two lodges per water body for eight water bodies located in the boreal forest of Québec, Canada. Results: Three sites showed alternating patterns of lodge use (occupation) over time, three sites (37.5%) demonstrated no alternating patterns of use, and two sites (25%) presented unclear patterns of lodge use. Conclusions: Alternating patterns of lodge use can be linked to food depletion and the need to regenerate vegetation around lodges, while non-alternating patterns may be related to fluctuations in water levels, the specific shrub and tree species surrounding the lodges, the size of the beaver territory, and the number of lodges present on a water body. Full article