Forests, Volume 11, Issue 7 (July 2020) – 74 articles

Because they generate more wood per area and time, short rotation plantations are likely to play an increasing role in meeting the global increase in the demand for wood fiber. To be successful, high-yield plantations require costly intensive silviculture regimes to ensure the survival and maximize yields. While hybrid poplar (Populus spp.) is frequently used in intensive, short rotation forestry, it is particularly sensitive to competition and resource levels. Mechanical site preparation is thus of great importance to create microsites that provide sufficient light levels and adequate soil water and nutrient availability. We conducted an experiment in Québec (Canada) to compare two intensive site preparation treatments commonly used to establish hybrid poplar. We compared the effects of double-blade site preparation (V-blade), mounding and a control on hybrid poplar growth and nutritional status four growing seasons after planting on recently harvested forested sites. We also evaluated the effects of site preparation and planted poplar on inorganic soil N. Our results confirmed general positive effects of site preparation on the early growth of hybrid poplar clones. After four growing seasons, survival was higher in the mounding treatment (99%) than in the V-blade (91%) and the control (48%). Saplings planted in the V-blade and in the mounding treatments had mean diameters that were respectively 91% and 155% larger than saplings planted in the control plots. Saplings were 68% taller in the mounding treatment than the control plots, but differences between the V-blade and controls were not significant. We did not detect significant effects of site preparation or the presence of planted hybrid poplar on soil inorganic N. Sapling foliar nutrient concentrations were not influenced by the site preparation treatments. Based on these results, mounding appears to be a good management approach to establish hybrid poplar plantations under the ecological conditions we have studied, as it is less likely to cause erosion because of the localized nature of the treatment. However, these environmental benefits need to be balanced against economic and social considerations. Full article

Quantifying biomass is important for determining the carbon stores in land ecosystems. The objective of this study was to predict aboveground biomass (AGB) of Agave lechuguilla Torr., in the states of Coahuila (Coah), San Luis Potosí (SLP) and Zacatecas (Zac), Mexico. To quantify AGB, we applied the direct method, selecting and harvesting representative plants from 32 sampling sites. To predict AGB, the potential and the Schumacher–Hall equations were tested using the ordinary least squares method using the average crown diameter (Cd) and total plant height (Ht) as predictors. Selection of the best model was based on coefficient of determination (R² adj.), standard error (S_xy), and the Akaike information criterion (AIC). Studentized residues, atypical observations, influential data, normality, variance homogeneity, and independence of errors were also analyzed. To validate the models, the statistic prediction error sum of squares (PRESS) was used. Moreover, dummy variables were included to define the existence of a global model. A total of 533 A. lechuguilla plants were sampled. The highest AGB was 8.17 kg; the plant heights varied from 3.50 cm to 118.00 cm. The Schumacher–Hall equation had the best statistics (R² adj. = 0.77, Sxy = 0.418, PRESS = 102.25, AIC = 632.2), but the dummy variables revealed different populations of this species, that is, an equation for each state. Satisfying the regression model assumptions assures that the predictions of A. lechuguilla AGB are robust and efficient, and thus able to quantify carbon reserves of the arid and semiarid regions of Mexico. Full article

Environmental niche modeling is an increasingly common tool in conservation and management of non-timber species. In particular, models of species’ habitats have been aided by new advances in remote sensing and it is now possible to relate forest structure variables to understory species at a relatively high resolution over large spatial scales. Here, we model landscape responses for a culturally-valued keystone shrub, velvet-leaf blueberry (Vaccinium myrtilloides Michaux), in northeast Alberta, Canada, to better understand the environmental factors promoting or limiting its occurrence, abundance, and fruit production, and to guide regional planning. Occurrence and abundance were measured at 845 and 335 sites, respectively, with both strongly related to land cover type and topo-edaphic factors. However, their influence varied widely, reflecting differences in the processes affecting occurrence and abundance. We then used airborne laser scanning (ALS) to characterize horizontal forest canopy cover for the study area, and related this and other geospatial variables to patterns in fruit production where we demonstrated a five-fold increase in fruit production from closed to open forest stands. We then simulated forest canopy thinning across the study area to identify places where gains in fruit production would be greatest following natural disturbance or directed management (e.g., thinning, prescribed burning). Finally, we suggest this approach could be used to identify sites for habitat enhancements to offset direct (land use change) or indirect (access) losses of resources in areas impacted with resource extraction activities, or simply to increase a culturally-valued resource through management. Full article

As large-scale forest plantations expand in developing countries, concerns are rising about their relation to and integration with adjacent local communities. In developing countries with weak enforcement of property rights, private plantations are more likely than state-owned plantations to involve villagers in plantation’s activities in order to secure and guarantee their access to land and labor resources. Certification standards of the Forest Stewardship Council (FSC) and adherence to responsible investment guidelines further strengthen this likelihood by requiring plantations to consult and engage local communities. Using household data from Tanzania, we assess households’ experiences with their participation in plantation activities by comparing the experiences of households in villages adjacent to private, FSC-certified plantations with those of households in villages adjacent to a non-certified, state-owned plantation. Our quantitative analyses show that households in the villages adjacent to the private, certified plantations are more likely to report to participate in plantation activities. Our results show that the certified plantations are more likely to respond to community complaints and grievances. We further find that male-headed households and households of plantation employees are more likely than female-headed households and households without plantation employees to participate in plantations’ activities. Our results imply that forest management certification can complement state policy approaches of sustainable forest management to enhance community participation in forest management. Full article

Phoebe bournei is a rare and endangered woody species and the success of its plantation development is dependent upon proper seedling cultivation. This study explored the regulation of N, P and K fertilizer and the interaction of these macronutrients on the growth of Phoebe bournei seedlings. To determine the optimum rate and ratio of N–P–K fertilizer in seedling cultivation, we used the unique “3414” incomplete orthogonal regression design to evaluate the effects of N–P–K fertilization on seedling morphological development. One-year-old Phoebe bournei bareroot seedlings were grown for one growing season under the defined fertilization regime, with their morphological development determined by measuring seedling attributes—root, stem, leaves and total biomass, root collar diameter and seedling height. These attributes were then combined to calculate the following indices: height-diameter ratio, shoot-root ratio and the seedling quality index (QI). Results showed that the N–P–K fertilizer had significant and beneficial effect on seedling cultivation. N effect was highest, followed by K and P. The three-way N×P×K interaction effect was strong, and the two-way interactions effect was highest for N×P, followed by P×K and N×K. At the “2” level of N (0.532 g·plant⁻¹), P (P₂O₅, 0.133 g·plant⁻¹), and K fertilizer (K₂O, 0.356 g·plant⁻¹), seedling growth and biomass accumulation were at their maximum. Unary, binary, and ternary quadratic fertilizer effect function equations of QI were established. Through comparative analysis, the ternary quadratic model was the optimal model and through a simulation–optimization, the optimal N–P–K fertilizer rates were 0.373~0.420 g·plant⁻¹ (N), 0.086~0.106 g·plant⁻¹ (P₂O₅), 0.243~0.280 g·plant⁻¹ (K₂O), with a N–P–K ratio of 1:0.20:0.43~1:0.65:0.75. Full article

Short-rotation forestry is of interest to provide biomass for bioenergy and act as a carbon sink to mitigate global warming. The Poplar tree (Populus × xiaohei) is a fast-growing and high-yielding tree species in Northeast China. In this study, a total of 128 Populus × xiaohei trees from the Songnen Plain, Heilongjiang Province, Northeastern China, were harvested. Several available independent variables, such as tree diameter at breast height (D), tree’s total height (H), crown width (CW), and crown length (CL), were differently combined to develop three additive biomass model systems and eight stem volume models for Populus × xiaohei tree. Variance explained within the three additive biomass model systems ranged from 83% to 98%, which was lowest for the foliage models, and highest for the stem biomass models. Similar findings were found in the stem volume models, in which the models explained more than 94% of the variance. The additional predictors, such as H, CL, or CW, evidently enhanced the model fitting and performance for the total and components biomass along with the stem volume models. Furthermore, the biomass conversion and expansion factors (BCEF_s) of the root (118.2 kg/m³), stem (380.2 kg/m³), branch (90.7 kg/m³), and foliage (31.2 kg/m³) were also calculated. The carbon concentrations of Populus × xiaohei in root, stem, branch, and foliage components were 45.98%, 47.74%, 48.32%, and 48.46%, respectively. Overall, the newly established models in this study provided complete and comprehensive tools for quantifying the biomass and stem volume of Populus × xiaohei, which might be essential to be specifically utilized in the Chinese National Forest Inventory. Full article

Globally, fire regimes are being altered by changing climatic conditions. New fire regimes have the potential to drive species extinctions and cause ecosystem state changes, with a range of consequences for ecosystem services. Despite the co-occurrence of forest fires with drought, current approaches to modelling flammability largely overlook the large body of research into plant vulnerability to drought. Here, we outline the mechanisms through which plant responses to drought may affect forest flammability, specifically fuel moisture and the ratio of dead to live fuels. We present a framework for modelling live fuel moisture content (moisture content of foliage and twigs) from soil water content and plant traits, including rooting patterns and leaf traits such as the turgor loss point, osmotic potential, elasticity and leaf mass per area. We also present evidence that physiological drought stress may contribute to previously observed fuel moisture thresholds in south-eastern Australia. Of particular relevance is leaf cavitation and subsequent shedding, which transforms live fuels into dead fuels, which are drier, and thus easier to ignite. We suggest that capitalising on drought research to inform wildfire research presents a major opportunity to develop new insights into wildfires, and new predictive models of seasonal fuel dynamics. Full article

East European forests dominated by Norway spruce (Picea abies (L.) H. Karst.) in the broad-leaved–coniferous zone should be considered as secondary communities formed under the influence of centuries-long activities (logging, fires and planting) and extended outside their natural range. The study raises an issue—how stable is the current state of Norway spruce forests in the center of the Russian plain and what is the effect of silviculture on the forest cover of the large urban agglomeration—the Moscow Region? Current study is based on multidisciplinary research and consequently concerns the age dynamics of spruce plantation forests, the species and typological diversity of mature spruce forests and spatial pattern of spruce forests along the south edge of their range. The composition and structure of Norway spruce plantations have been studied for various age classes and compared with mature natural spruce forests and pine plantations on the basis of field data. Remote sensing data and modeling approach were applied to estimate the spatial structure of spruce forests. It is found that mature plantations (over 80 years) become similar to natural forests in terms of structure and composition. The relationship between the distribution of spruce formations and the climatic and geomorphological conditions are confirmed. The proportion of spruce and spruce–aspen/birch communities follows the pattern of zones—the transition from the coniferous and broad-leaved forest zone to the broad-leaved forest zone. Despite the significant anthropogenic impact and the high proportion of plantations in the composition of Norway spruce forests (about 60–80%), their floristic and typological diversities correspond to such properties of zonal broad-leaved–coniferous communities. Over-matured plantations can provide valuable habitats for the re-establishment of native typological diversity. This makes it possible to use silviculture stands as an accelerated alternative to the natural recovery of disturbed habitats. Full article

Teak (Tectona grandis Linn. f) is a globally valuable hardwood tree species whose growth performance and tree quality characteristics are controlled by various factors. Teak tree quality characteristics such as stem straightness, buttressing, and protuberant buds/knots are important in the sawing process, and directly affect timber yield, timber grade, recovery, and cost. In this study, we assessed the relationships among tree quality characteristics, stand characteristics, and site characteristics in plantation teak in the Luang Prabang province of the Lao PDR. We established 53 sample plots (20 × 20 m) and measured a total of 2149 sample trees. The stand-level tree age ranged from 10 to 31 years, and the trees were distributed in various modes of topography. The altitude ranged from 287 to 867 masl. The results of Spearman’s partial rank correlation analysis among the parameters revealed the present condition of the teak plantation forest in the region. The altitude was related to stand age and was correlated with tree quality characteristics such as epicormic shoots, mode of branching, and branch size. The correlation results suggest that higher-density plantation at the higher altitude sites might be suitable for teak plantations in this area. In addition, we found that a longer rotation in forest management might degrade tree quality. Full article

There is a need for new solutions in wood protection against marine wood borers and termites in Europe. A new solution could be the esterification of wood with sorbitol and citric acid (SCA) since these are inexpensive and readily available feedstock chemicals and have shown protective properties against fungal wood degradation in earlier studies and prevented macrobiological degradation, as shown in this study. Protection of wood products in the marine environment lacks available wood preservatives that are approved for marine applications. Termite infestation is opposed mainly by biocide treatments of wood. Several wood modification systems show high resistance against both marine borers and subterranean termites. However, the existing commercialized wood modification products are costly. Both macrobiological forms of degradation represent a great threat for most European wood species, which are rapidly and severely degraded if not properly treated. This study investigated esterified wood in standard field trials against marine wood borers, and against subterranean termites in laboratory trials in a no-choice and choice test. The treatment showed good resistance against wood borers in the marine environment after one season and against subterranean termites in the laboratory after eight weeks. The low termite survival rate (SR) in the no-choice test during the first week of testing indicates a mode of action that is incomparable to other wood modification treatments. Full article

Urban green infrastructure plays an increasingly significant role in sustainable urban development planning as it provides important regulating and cultural ecosystem services. Monitoring of such dynamic and complex systems requires technological solutions which provide easy data collection, processing, and utilization at affordable costs. To meet these challenges a pilot study was conducted using a network of wireless, low cost, and multiparameter monitoring devices, which operate using Internet of Things (IoT) technology, to provide real-time monitoring of regulatory ecosystem services in the form of meaningful indicators for both human health and environmental policies. The pilot study was set in a green area situated in the center of Moscow, which is exposed to the heat island effect as well as high levels of anthropogenic pressure. Sixteen IoT devices were installed on individual trees to monitor their ecophysiological parameters from 1 July to 31 November 2019 with a time resolution of 1.5 h. These parameters were used as input variables to quantify indicators of ecosystem services related to climate, air quality, and water regulation. Our results showed that the average tree in the study area during the investigated period reduced extreme heat by 2 °C via shading, cooled the surrounding area by transferring 2167 ± 181 KWh of incoming solar energy into latent heat, transpired 137 ± 49 mm of water, sequestered 8.61 ± 1.25 kg of atmospheric carbon, and removed 5.3 ± 0.8 kg of particulate matter (PM₁₀). The values of the monitored processes varied spatially and temporally when considering different tree species (up to five to ten times), local environmental conditions, and seasonal weather. Thus, it is important to use real-time monitoring data to deepen understandings of the processes of urban forests. There is a new opportunity of applying IoT technology not only to measure trees functionality through fluxes of water and carbon, but also to establish a smart urban green infrastructure operational system for management. Full article

Future climate change will have serious impacts on species survival and distribution and will likely lead to the extinction of some species classified as endangered. Carpinus tientaiensis (Betulaceae), a unique and endangered species in China, has restricted distribution and a small population, indicating an urgent need for its protection. However, research on its current distribution or the influence that climate change will have on its future survival and distribution is limited. We used a MaxEnt model and ArcGIS software to predict the current and future niches of C. tientaiensis. The current suitable distribution area of C. tientaiensis is small, mainly in east China, south Zhejiang and Anhui, and central and southern mountainous areas of Taiwan province. The core suitable areas are concentrated in the Xianxialing and Kuocang mountains in south Zhejiang, the southern mountains of Taiwan, and the Dabie, Huangshan and Jiuhua mountains in south Anhui. Among the 15 BIOCLIM variables examined, the precipitation of the driest quarter (bio17) was found to be the most important factor limiting C. tientaiensis survival and distribution. Future field investigations will focus on the Xianxialing and Kuocang mountains, as they may have unidentified wild C. tientaiensis communities. In the future, the Kuocang, Dapan and Tiantai mountains in east Zhejiang, and the high-altitude areas of Dabie and Jiuhua mountains in south Anhui, will be suitable for C. tientaiensis ex situ conservation and cultivation. However, the suitable distribution and core suitable areas for C. tientaiensis will decrease sharply as they are susceptible to climate shocks. Moreover, the suitable distribution area of C. tientaiensis is predicted to move slightly north and obviously eastward. Therefore, we suggest that strengthen conservation and management efforts for C. tientaiensis in its original habitats, and actively carry out ex situ conservation and artificial breeding in botanical gardens. Full article

Recent changes in fire regimes, with more frequent, extensive, and severe fires, are modifying soil characteristics. The aim of this study was to evaluate the effect of burn severity on the resistance of some physical, chemical, and biochemical soil properties in three different forest ecosystems affected by a wildfire in the northwest of the Iberian Peninsula. We evaluated burn severity immediately after fire using the Composite Burn Index (CBI) in three different ecosystems: shrublands, heathlands, and oak forests. In the same field plots used to quantify CBI, we took a composite soil sample to analyse physical (mean weight diameter (MWD)), chemical (pH; total C; total organic C (TOC); total inorganic C (TIC); total N; available P; exchangeable cations Na⁺, K⁺, Mg²⁺, and Ca²⁺; and cation exchange capacity (CEC)), and biochemical (β-glucosidase, urease, and acid phosphatase enzyme activities) properties. The resistance index of each property was then calculated. Based on our results, the values of the soil chemical properties tended to increase immediately after fire. Among them, total C, TOC, and exchangeable Na⁺ showed higher resistance to change, with less variation concerning pre-fire status. The resistance of chemical properties was higher in the oak forest ecosystem. MWD decreased at high severity in all ecosystems, but soils in shrublands were more resistant. We found a high decrease in soil enzymatic activity with burn severity, with biochemical properties being the least resistant to change. Therefore, the enzymatic activity of soil could be a potential indicator of severity in forest ecosystems recently affected by wildfires. Full article

Microwave (MW) treatment is an effective method to increase refractory wood permeability, thereby reducing drying time and defects. The extent of modification depends on the damage extent of the wood microstructure. In this study, MW intensities of 43 kWh/m³ (low intensity) and 57 kWh/m³(high intensity) were adopted to treat Chinese fir lumber. Microstructural changes in wood samples were observed using scanning electron microscopy (SEM) and pore structure was characterized using mercury intrusion porosimetry (MIP). Results were as follows: After low-intensity MW treatment, parts of the bordered pit membranes in tracheids were damaged, and micro-fibrils on the margo were ruptured, while the torus basically remained intact. Micro-cracks were observed at both ends of the cross-field pit apertures, propagating to the cell walls of tracheids. The middle lamellar between ray parenchyma cells and longitudinal tracheids cracked, and the width of cracks was in the range of 1–25 μm. After high-intensity MW treatment, damage to the wood microstructure was more severe than that in the low-intensity MW treatment, with macro-cracks having a width range of 100–130 μm being generated. In addition, on the fracture surface of macro-cracks, the bordered pit membranes in tracheids fell off, cross-field pit membranes disappeared and the ray parenchyma cells were seriously damaged, exhibiting fracture of the tracheid walls. Both low-intensity and high-intensity MW treatment can increase the pore diameter corresponding to the margo capillaries (peak value increased from 674.7 nm to 831.8 nm and 1047.6 nm, respectively). The number of pores in the tracheid lumen diameter range also significantly increased. These results provide a theoretical support forMW treatment processes’ improvement and high-value utilization of Chinese fir. Full article

This study aimed to clarify the environmental factors limiting the height of aged Cryptomeria japonica trees. The study was conducted on C. japonica plantations of about 100 years old at the Boso Peninsula, Japan, where the climatic conditions are almost uniform. Twenty-eight plots measuring 10 × 10 m were established on ridges, and 40 plots were established on the middle or lower sections of slopes. The stand ages ranged from 93 to 115 years old. The height of the tallest tree and soil depth (SD) were measured in each plot, and the wetness index (WI) and openness (OP) of each plot were calculated using a digital elevation model. The tree height at the 100-year age (H₁₀₀) was estimated. The H₁₀₀ ranged from 16.2 to 44.9 m and was significantly correlated with the logWI (r = 0.78) and OP (r = −0.70). SD and H₁₀₀ were significantly correlated in the plots on the ridges but not in the plots on the middle or lower sections of slopes. It indicated that soil water retention capacity might limit tree height in the relatively dry soil conditions. The coefficient of determination adjusted by the number of parameters for H₁₀₀ predicted using multiple regression analysis with environmental factors of logWI, logWI and OP, or logWI, OP and SD were 0.60, 0.69, and 0.73, respectively. The inclusion of OP and SD in the model improved the prediction of H₁₀₀, suggesting that the wind and rooting depth could be the influencing factors in determining the height of aged trees. The findings of this study could be used in the planning and management of forestry plantations of long rotation system. Full article

Research Highlights: Our findings highlight that the contribution of carbon sequestration from plantations to REDD+ will remain limited, and that opportunity costs in Southeast Asia will likely increase, due to future oil palm expansion. Background and Objectives: Land use, land-use change, and forestry (LULUCF) are significant sources of carbon emissions. The United Nations Framework Convention on Climate Change (UNFCCC) agreed that the Reducing Emissions from Deforestation and Forest Degradation Plus program, also known as REDD+, could contribute to carbon sinks in tropical regions. These reductions could serve as carbon credits that offset emissions from other sources. Materials and Methods: This study uses the cellular automaton technique to simulate the business-as-usual (BAU) scenario and the gain-loss method, to measure carbon emissions resulting from forest conversion. The output of the integration of the models makes it possible to evaluate one of the most important financial costs: opportunity costs. Two scenarios (with and without consideration of carbon sequestration) in rubber and oil palm plantations are examined. Results: A sensitivity assessment in Kalimantan, Indonesia, shows that carbon sequestration from plantations affects value of opportunity costs less than social discount rates. Further analysis suggests that oil palm plantations have a greater impact than rubber plantations. Conclusions: Our study provides a case that can be applied to other regions for evaluating the impacts of plantation carbon sequestration, and insights that can help local policymakers design a financially attractive REDD+ program in other forest areas of the world. Full article

Canary Island pine (Pinus canariensis C.Sm. ex DC) is a species endemic to the Canary Islands (Spain) that was for centuries overexploited for its wood and resin. Due to the state of the pine forest, more than 10,000 hectares were reforested in the middle of the 20th century. Now, under the silvicultural management plan, thinning operations have allowed Canary Island pine wood to be mechanically characterised for the first time using large test pieces. In total, 1529 pieces measuring 2600 × 120 × 35 mm and visually graded according to Spanish standard UNE 56544 (Visual grading of large structural coniferous sawn timber) were assessed, resulting in 872 pieces in grades ME-1 and ME-2 and 657 rejects. After the characteristic values of density (479–453 kg∙m⁻³), modulus of elasticity (MOE) (14,023–11,276 N∙mm⁻²) and bending strength (MOR) (26–14 N∙mm⁻²) were determined for both grades (ME-1 and ME-2), strength class C24 was assigned to grade ME-1, with similar values to Pinus radiata D.Don and Pinus pinaster Aiton, and C14 was assigned to grade ME-2. Density, number of growth rings, growth ring width, and presence/absence of resinous wood have a significant influence on MOE and MOR, for a confidence level of 95%. Reforestation of Canary Island pine not only allows restoration of the forest cover, but also provides an opportunity, through thinning, to obtain quality wood, helping to create employment and associated industry. This local example with an endemic species can be extrapolated to other parts of the world. Full article

The impregnation of low-molecular-weight monomers prior to polymerize them inside the wood may be an efficient way to improve some important wood properties. This work aimed to determine some technological properties of wood-based composites (WPC) produced by in situ polymerization, using a pine wood (Pinus elliottii Engelm.) impregnated with methyl methacrylate (MMA). For that, samples taken from both juvenile (JV) and mature (MT) pine woods were treated with MMA. Physical, mechanical, chemical, thermal and morphological features were evaluated. MMA-treated woods from both juvenile and mature woods presented superior physical, mechanical (expect brittleness) and thermal properties when compared to pristine ones. The infrared spectra and morphological analysis by scanning electron microscopy (SEM) confirmed the presence of the monomer inside the pine wood. The juvenile wood presented higher treatability than the mature wood, due to its higher content of intra- and inter-cellular spaces. Full article

Skidding operations are thought to have negative impacts on soil emergence because they may increase soil compaction and reduce vegetation cover and the soil’s organic matter content. We investigated whether and to what extent tree harvesting and subsequent skidding initially altered seedling emergence in two Mediterranean forests of Pinus nigra Arn. ssp. salzmannii (Spanish black pine) in the Cuenca Mountains (Spain). Our main objective was to compare the Spanish black pine seedling emergence rate among skid trails, soil areas scarified by felled trees, and areas undisturbed next to harvest operations. In addition, we selected an unmanaged stand as reference, in order to look for evidence of seedling emergence under natural conditions. We measured Spanish black pine seed fall and seedling emergence immediately after harvest operations in two locations in the Cuenca Mountains (Palancares and Majadas forests), which are typical forests in Cuenca Mountains. The results showed that the Palancares site presented higher seed fall in comparison to the Majadas site. In addition, seed fall was higher in the unmanaged stand, as we recorded a higher tree density in this site in comparison to harvested stands (Palancares and Majadas). Furthermore, our results demonstrated differences in seedling emergence between lower elevation drier Palancares and higher elevation wetter Majadas and relative differences in seedling emergence among skid trail, scarified, and undisturbed harvested areas. Finally, the unmanaged stand presented the highest seedling emergence in comparison to scarified, compacted, and non-disturbed harvested areas. Overall, the results suggest a short-term impact of skidding on seedling emergence, which should be considered for future management guidelines of Spanish black pine in the Mediterranean climate. Full article

Cryptomeria fortunei Hooibrenk (Chinese cedar) is a coniferous tree from southern China that has an important function in landscaping and timber production. Lignin is one of the key components of secondary cell walls, which have a crucial role in conducting water and providing mechanical support for the upward growth of plants. It is mainly biosynthesized via the phenylpropanoid metabolic pathway, of which the molecular mechanism remains so far unresolved in C. fortunei. In order to obtain further insight into this pathway, we performed transcriptome sequencing of the C. fortunei cambial zone at 5 successive growth stages. We generated 78,673 unigenes from transcriptome data, of which 45,214 (57.47%) were successfully annotated in the non-redundant protein database (NR). A total of 8975 unigenes were identified to be significantly differentially expressed between Sample_B and Sample_A after analyzing their expression profiles. Of the differentially expressed genes (DEGs), 6817 (75.96%) and 2158 (24.04%) were up- and down-regulated, respectively. 83 DEGs were involved in phenylpropanoid metabolism, 37 DEGs that encoded v-Myb avian myeloblastosis viral oncogene homolog (MYB) transcription factor (TF), and many candidates that encoded lignin synthesizing enzymes. These findings contribute to understanding the expression pattern of C. fortunei cambial zone transcriptome. Furthermore, our results provide additional insight towards understanding the molecular mechanisms of wood formation in C. fortunei. Full article

Stand density changes due to aging and thinning interventions. At the same time, the social status of trees develops and varies due to different genetic conditions as well as access to nutrients and light. Trees growing in diverse conditions gain their social status in the stand, which, in the end, influences their development and biomass allocation. The objective of this research was to discover if stand density or tree social status has an impact on a tree’s aboveground biomass allocation. The study was carried out in five premature and five mature pine stands, growing in the same soil conditions. The selected sample stands had a different growing density, from low to high. In each sample stand, 10 trees were selected to represent a different social status, according to the Schädelin classification. There were 100 trees felled in total (50 in the premature stands and 50 in the mature stands), for which the dry biomass of the stem, living and dead branches, needles, and cones was determined. The results showed that stand density only had an impact on the branches’ biomass fraction but not the stem and foliage fractions, while social status had an impact on all the fractions. Dominant and codominant trees, as well as those with developed crowns, had a smaller share of the stem and higher share of branches in comparison with trees of a lower social status. Full article

Ungulate browsing is a major factor influencing tree regeneration. However, it is unclear if the observed increase in ungulate abundance in Central Europe implies increased browsing, and which other factors influence the incidence of browsing. We investigated the impact of forty variables (site, climate, forest and ungulates) on the probability of leader shoot browsing of six tree species which are frequent in Switzerland. The analysis was based on a large dataset including 49 monitoring areas, each containing 25–64 circular plots, in which 10 to 130 cm tall seedlings were repeatedly assessed. Browsing probability was estimated for each plot and year by mixed effects logistic regression and used as a response in random forests to disentangle the influence of the explanatory variables. Browsing probability was positively correlated with ungulate density measures (number culled by hunting or found dead) for all six tree species. Where beyond roe deer, some red deer and/or chamois were present, the browsing probability was higher. Small timber tree stands had less browsing than young growth and thicket stands. Seedlings tended to be more frequently browsed in stands with >80% canopy shading. Browsing increased with increasing understory cover, independent of vegetation category. In conclusion, browsing is a multifactorial phenomenon and ungulate density estimates alone do not explain the whole browsing probability. Full article

Windthrow and storm damage are crucial issues in practical forestry. We propose a method for rapid detection of windthrow hotspots in airborne digital orthophotos. Therefore, we apply Haralick’s texture features on 50 × 50 m cells of the orthophotos and classify the cells with a random forest algorithm. We apply the classification results from a training data set on a validation set. The overall classification accuracy of the proposed method varies between 76% for fine distinction of the cells and 96% for a distinction level that tried to detect only severe damaged cells. The proposed method enables the rapid detection of windthrow hotspots in forests immediately after their occurrence in single-date data. It is not adequate for the determination of areas with only single fallen trees. Future research will investigate the possibilities and limitations when applying the method on other data sources (e.g., optical satellite data). Full article

Artisanal and small-scale mining is a significant economic sector in Rwanda. Mining activities often use a watercourse, in which secondary extraction takes place and minerals are washed. Mining thus greatly affects the geomorphological conditions in the area. The aim of this paper is a digest of environmental impacts of alluvial artisanal and small-scale mining with a focus on anthropogenic influences on topography with regard to the methods used in raw material mining. The author draws on a case study from the mining site of Rutsiro district in Rwanda. Main findings of alluvial artisanal mining in a riverscape are changes in landscape structure, deforestation, intensification of geomorphological processes, new relief shapes (suffosion depressions, check dams, gravel benches, anthropogenic channels) and hydrological river regime, chemical pollution of soil and watercourses. Artisanal and small-scale mining may lead to a significant change and acceleration of fluvial processes. This paper covers a broad understanding of environmental impacts of alluvial artisanal and small-scale mining with a focus on anthropogenic influencing. Full article

Medicinal plants are used worldwide due to their lower risk of side effects and eco-friendly, cost-effective production when compared to chemical drugs, encouraging researchers to further exploit the therapeutic potential of the former. One of the most popular medicinal plants is Vitex agnus-castus L., grown in tropical and sub-tropical regions, to which different health benefits have already been attributed. In this perspective article, the in vitro and in vivo therapeutic properties of V. agnus-castus L. have been analyzed and reviewed with a special focus on its health-promoting effects and potential nutraceutical applications. Full article

Tree peony is a deciduous shrub endemic to China, and peony seed oil (PSO) is an important plant oil resource. However, at present, pruning and fruits harvesting of oil tree peony are mainly completed by manual work, which has seriously affected production efficiency. By the need to develop efficient pruning and harvesting equipment for oil tree peony, this study investigated the effect of cutting tool geometric parameters and cutting speed on cutting force and energy. A cutting device was set up, and six cutting tools with different blade angle and sliding-cutting angle were prepared for this research. Stems in different growth stages (anthesis and fructescence) were collected for cutting experiments. In this paper, four blade angles (25°, 30°, 35°, and 40°), three sliding-cutting angles (0°, 10°, and 20°), and four cutting speeds (25 mm/min, 50 mm/min, 100 mm/min, and 200 mm/min) were considered in the experiments. The results showed that cutting force and energy are positively related to blade angle, and the minimum cutting force and energy are required in cutting with 25° blade angle. Compared to straight cutting (sliding-cutting angle is 0°), sliding cutting can obviously reduce the cutting force and energy. Furthermore, the best sliding-cutting angles of cutting tools have discrepancies dependent on the stems in different growth stages. In fructescence, 10° sliding cutting required the lowest cutting force and energy. In contrast, the best sliding-cutting angle of stems in anthesis was 20°. On the other hand, the cutting force and energy were obviously proportional to the cutting speed, which increased by the cutting speed increasing. Therefore, under the condition of ensuring the cutting efficiency, reducing the cutting speed can effectively reduce the power consumption. These results are an important basis for pruning and harvesting machine development for oil tree peony. Full article

Research highlights: Moisture diffusion coefficients for stems and branches of degenerated Calluna vulgaris L. have been obtained and a mathematical model for the drying process has been developed and validated as an input to future fire danger modeling. Background and objectives: In Norway, several recent wildland–urban interface (WUI) fires have been attributed to climate changes and accumulation of elevated live and dead biomass in degenerated Calluna stands due to changes in agricultural activities, i.e., in particular abandonment of prescribed burning for sheep grazing. Prescribed burning is now being reintroduced in these currently fire prone landscapes. While available wildfire danger rating models fail to predict the rapidly changing fire hazard in such heathlands, there is an increasing need for an adapted fire danger model. The present study aims at determining water diffusion coefficients and develops a numerical model for the drying process, paving the road for future fire danger forecasts and prediction of safe and efficient conditions for prescribed burning. Materials and methods: Test specimens (3–6 mm diameter) of dead Calluna stems and branches were rain wetted 48 h and subsequently placed in a climate chamber at 20 °C and 50% relative humidity for mass loss recordings during natural convection drying. Based on the diameter and recorded mass versus time, diffusion coefficients were obtained. A numerical model was developed and verified against recoded mass loss. Results: Diffusion coefficients were obtained in the range 1.66–10.4 × 10⁻¹¹ m²/s. This is quite low and may be explained by the very hard Calluna “wood”. The large span may be explained by different growth conditions, insect attacks and a varying number of years of exposure to the elements after dying. The mathematical model described the drying process well for the specimens with known diffusion coefficient. Conclusions: The established range of diffusion coefficients and the developed model may likely be extended for forecasting moisture content of degenerated Calluna as a proxy for fire danger and/or conditions for efficient and safe prescribed burning. This may help mitigate the emerging fire risk associated with degenerated Calluna stands in a changing climate. Full article

Drought is a major factor limiting tree growth and plant vitality. In the Mediterranean region, the length and intensity of drought stress strongly varies with altitude and site conditions. We used electronic dendrometers to analyze the response of two native pine species to drought and precipitation events. The five study sites were located along an elevation gradient on the Mediterranean island of Corsica (France). Positive stem increment in the raw dendrometer measurements was separated into radial stem growth and stem swelling/shrinkage in order to determine which part of the trees’ response to climate signals can be attributed to growth. Precipitation events of at least 5 mm and dry periods of at least seven consecutive days without precipitation were determined over a period of two years. Seasonal dynamics of stem circumference changes were highly variable among the five study sites. At higher elevations, seasonal tree growth showed patterns characteristic for cold environments, while low-elevation sites showed bimodal growth patterns characteristic of drought prone areas. The response to precipitation events was uniform and occurred within the first six hours after the beginning of a precipitation event. The majority of stem circumference increases were caused by radial growth, not by stem swelling due to water uptake. Growth-induced stem circumference increase occurred at three of the five sites even during dry periods, which could be attributed to stored water reserves within the trees or the soils. Trees at sites with soils of low water-holding capacity were most vulnerable to dry periods. Full article

Vegetation phenology is a sensitive indicator of climate change. With the intensification of global warming, the changes in growing seasons of various vegetation types have been widely documented across the world. However, as one of the most vulnerable regions in response to the global climate change, the phenological responses and associated mechanisms in mid–high latitude forests are still not fully understood. In this study, long-term changes in forest phenology and the associated relationship with the temperature and snow water equivalent in the China–Mongolia–Russia International Economic Corridor were examined by analyzing the satellite-measured normalized difference vegetation index and the meteorological observation data during 1982 to 2015. The average start date of the growing season (SOS) of the forest ecosystem in our study area advanced at a rate of 2.5 days/decade, while the end date of the growing season (EOS) was delayed at a rate of 2.3 days/decade, contributing to a growing season that was approximately 15 days longer in the 2010s compared to that in 1980s. A higher April temperature is beneficial to the advance in the SOS, and a higher summer temperature has the potential to extend the EOS in the forest ecosystem. However, our results also suggest that a single temperature cannot fully explain the advance of the SOS, as well as the delay in the EOS. The preseason Snow Water Equivalent (SWE) is also an essential factor in influencing the growing season. A higher SWE in February and March and lower SWE in April tend to advance the SOS, while higher SWE in pre-year December and lower SWE in current year October are beneficial to the extension of the EOS. Full article

In Siberia, most boreal forests are located in an area with relatively moist forest soils, which makes logging activities possible exclusively during the frost period with a permanent snow cover and stable sub-zero temperatures. As the global climate is experiencing a trend towards warming, it is reasonable to suppose that the duration of the logging season might shorten over time, influencing the economic potential of Siberian forests. To test this hypothesis, we created a concept for calculating the duration of the logging season, taking into account the economic and climatic peculiarities of doing forest business in these territories. Using the long-run daily-observed climatic data, we calculated the duration of the logging season for eight representative stations in Krasnoyarsk Krai (Yeniseysk, Boguchany, Achinsk, and Minusinsk) and Irkutsk Oblast (Bratsk, Kirensk, Tulun, and Yerbogachen) in 1966–2018. We found strong evidence of logging season duration shortening for almost all considered stations, with an uneven effect on the start and end boundaries of the season. Climate warming has almost no effect on the start date of the season in winter, but it significantly shifts the boundaries of the season end in spring. Using the autoregressive-integrated-moving average modeling (ARIMA) models, we demonstrated that, in the near future, the trends of the gradual shortening of the logging season will hold for the most part of the considered stations. The most pronounced effect is observed for the Achinsk station, where the logging season will shorten from $148.4\pm 17.3$ days during the historical sample (1966–2018) to $136.2\pm 30$ days in 2028, which reflects global warming trend patterns. From an economic perspective, a shorter duration of the logging season means fewer wood stocks available for cutting, which would impact the ability of companies to enact their logging plans and lead them to suffer losses in the future. To avoid losses, Siberian forest firms will have to adapt to these changes by redefining their economic strategies in terms of intensifying logging operations. Full article