Forests — Open Access Forestry Journal

This paper investigates whether shocks to pulp for paper production for 17 Organisation for Economic Co-Operation and Development (OECD) members over the period 1980–2012 are transitory or permanent. A variety of univariate and panel data unit root tests are employed. The presence of structural breaks is taken into account when performing those tests. Based on the Narayan-Popp univariate unit root test, wood production series for approximately 64.71% of countries is found to follow a non-stationary process. However, univariate unit root tests tend to have low power when the time span is relatively short. Consequently, three generations of panel unit root tests are considered. Cross-sectional dependence is detected. The first generation of unit roots do not effectively control for cross-sectional dependence, while the second and third generations do. The third generation accounts mainly for cross-sectional co-integration. As a confirmatory analysis, both unit root tests that tests for the null of non-stationarity and stationarity are considered. Most of the panel unit root tests point towards a non-stationary process. Hence, while these shocks can be transmitted to other economic sectors, past behaviours of wood production cannot be used for forecasting purposes. Forest conservation policies can have a permanent impact on pulp for paper production. Full article

We explore the biophysical potential and economic attractiveness of black spruce (Picea mariana) regeneration in eastern Canada under the high greenhouse gas emission scenario (RCP 8.5) of the Intergovernmental Panel on Climate Change (IPCC). The study integrates net primary productivity and net ecosystem productivity estimates from three major global climate models (GCMs), growth and yield equations specific to black spruce, and economic analyses to determine spatially varying investment values of black spruce regeneration—both including and excluding carbon sequestration benefits. Net present value (NPV) was used to represent financial attractiveness. It was assumed that stands would not be harvested at volumes less than 80 m³·ha⁻¹. A baseline case with the stumpage price set to $20 m⁻³, stand establishment cost $500 ha⁻¹, and the discount rate 4%, was used with wide-ranging sensitivity analyses conducted around these assumptions. These values represent the wide range of choices and outcomes possible with black spruce regeneration investments. The results indicated a latitudinal gradient in economic attractiveness, with higher forest productivity and NPVs in the southern portion of the study area; however, black spruce regeneration was not economically attractive unless regeneration costs were very low (representing something closer to a natural regeneration type scenario) and/or carbon sequestration benefits of at least $5 ton⁻¹ CO₂ were realized. In general, the optimal harvest rotation age increased with increasing carbon price by approximately 9 to 18 years. Results of this study highlight the importance of future price and yield expectations and establishment costs in evaluating forest investments. Full article

The forests of North Mongolia are largely dominated either by larch (Larix sibirica Ledeb.) or birch (Betula platyphylla Sukaczev). The increasing demand for timber and firewood is currently met by removal of wood from these forest stands. Therefore, silvicultural approaches that account for both utilization and protection are needed. Thinning trials were established in the research area Altansumber, in the mountain forest steppe west of the town of Darkhan. We analyzed the response of non-spatial and spatial structure and growth of birch and larch stands on thinning. Before thinning, spatial tree distribution was largely clumped. Thinning promoted regular tree distribution. Ingrowth of new stems after thinning tended to redirect stand structure towards clumping. Both relative and absolute tree growth and competition were evaluated before, directly after, and three years after the thinning. Competition played a significant role in tree growth before thinning. A reduction in competition after thinning triggered significantly increased growth of both birch and larch. The observed positive growth response was valid in absolute and relative terms. A methodically based forest management strategy, including thinning operations and selective cuttings, could be established, even under the harsh Mongolian conditions. Our findings could initiate the development of broader forest management guidelines for the light-taiga dominated stands. Full article

Seedlings from four families of loblolly pine (Pinus taeda L.) were grown in capped open-top chambers and exposed to three different weekly moisture regimes for 13 weeks. Moisture regimes varied in intensity and frequency of simulated rainfall (irrigation) events; however, the total amounts were comparable. These simulated treatments were chosen to simulate expected changes in rainfall variability associated with climate change. Seedlings were inoculated with two root-infecting ophiostomatoid fungi associated with Southern Pine Decline. We found susceptibility of loblolly pine was not affected by water stress; however, one family that was most sensitive to inoculation was also most sensitive to changes in moisture availability. Many studies have examined the effects of drought (well-watered vs. dry conditions) on pine physiology and host-pathogen interactions but little is known about variability in moisture supply. This study aimed to elucidate the effects of variability in water availability, pathogen inoculation and their interaction on physiology of loblolly pine seedlings. Full article

We review the literature that led to clarifying the role of tropical forests in the global carbon cycle from a time when they were considered sources of atmospheric carbon to the time when they were found to be atmospheric carbon sinks. This literature originates from work conducted by US Forest Service scientists in Puerto Rico and their collaborators. It involves the classification of forests by life zones, estimation of carbon density by forest type, assessing carbon storage changes with ecological succession and land use/land cover type, describing the details of the carbon cycle of forests at stand and landscape levels, assessing global land cover by forest type and the complexity of land use change in tropical regions, and assessing the ecological fluxes and storages that contribute to net carbon accumulation in tropical forests. We also review recent work that couples field inventory data, remote sensing technology such as LIDAR, and GIS analysis in order to more accurately determine the role of tropical forests in the global carbon cycle and point out new avenues of carbon research that address the responses of tropical forests to environmental change. Full article

Forests in tropical and sub-tropical countries face severe pressures due to a combination of poverty and environment degradation. To be effective, measures to protect these forests must therefore consider both economic and ecological dimensions synergistically. The purpose of this paper was to synthesize our long-term work (1994–2015) on a Ginkgo (Ginkgo biloba L.) agroforestry system and demonstrate its potential for achieving both goals, and discuss its wider application in tropical and sub-tropical countries. The performance of various ecological, economic, and social indicators was compared among five Ginkgo agroforestry systems. Two additional indicators, Harmony Degree (HD) and Development Degree (DD), were also used to show the integrated performance of these indicators. Ginkgo-Wheat-Peanut (G+W+P) and Ginkgo-Rapeseed-Peanut (G+R+P) are the best systems when compared to pure and mixed Ginkgo plantations, or pure agricultural crops. Results demonstrate that it is possible to achieve both economic development and environmental protection through implementation of sustainable agroforestry systems in sub-tropical regions. Full article

Abstract: To better understand carbon (C) sequestration by Juglans regia L. plantations in karst regions of southwest China, this study examined biomass increment and C storage in four different-aged J. regia stands, as well as the distribution of carbon stock among the various ecosystem components. Tree and ecosystem biomass increased with stand age. Aboveground biomass (AGB) represented 64.79% of the total biomass, belowground tree biomass comprised 22.73%, and shrubs and herbs totaled 11.38%, whereas only a small amount (1.11%) was associated with soil litter. Soil organic C (SOC) content in the top soil of plantations aged 1, 5, 9, and 13 years was 33.37, 53.15, 33.56, and 49.78 mg ha⁻¹, respectively. SOC content decreased continually with increasing soil depth. Ecosystem C storage amounted to 33.49, 54.21, 46.40, and 65.34 mg ha⁻¹ for the 1-, 5-, 9-, and 13-year old plantations, respectively, with most (86.55%) of the ecosystem C being in the soil. Our results suggest that large-scale planting of J. regia has potential for not only vegetation restoration but also high C fixation capacity in the karst region of southwest China. Full article

Climate changes influencing forest ecosystems include increased air temperatures and CO₂ concentrations as well as droughts and decreased water availability. These changes in turn effect changes in species composition of both host plants and pathogens. In the case of Armillaria, climate changes cause an increase in the activity of individual species and modify the growth of rhizomorphs, increasing the susceptibility of trees. The relationship between climate changes and the biotic elements of Armillaria disease are discussed in overview. Full article

Reducing uncertainty in forest carbon estimates at local and regional scales has become increasingly important due to the centrality of the terrestrial carbon cycle in issues of climate change. In Victoria, Australia, public natural forests extend over 7.2 M ha and constitute a significant and important carbon stock. Recently, a wide range of approaches to estimate carbon stocks within these forests have been developed and applied. However, there are a number of data and estimation limitations associated with these studies. In response, over the last five years, the State of Victoria has implemented a pragmatic plot-based design consisting of pre-stratified permanent observational units located on a state-wide grid. Using the ground sampling grid, we estimated aboveground and belowground carbon stocks (including soil to 0.3 m depth) in both National Parks and State Forests, across a wide range of bioregions. Estimates of carbon stocks and associated uncertainty were conducted using simple design based estimators. We detected significantly more carbon in total aboveground and belowground components in State Forests (408.9 t ha⁻¹, 95% confidence interval 388.8–428.9 t ha⁻¹) than National Parks (267.6 t ha⁻¹, 251.9–283.3 t ha⁻¹). We were also able to estimate forest carbon stocks (and associated uncertainty) for 21 strata that represent all of Victoria’s bioregions and public tenures. It is anticipated that the lessons learnt from this study may support the discussion on planning and implementing low cost large area forest carbon stock sampling in other jurisdictions. Full article

Disturbance is a critical ecological process in forested systems, and disturbance maps are important for understanding forest dynamics. Landsat data are a key remote sensing dataset for monitoring forest disturbance and there recently has been major growth in the development of disturbance mapping algorithms. Many of these algorithms take advantage of the high temporal data volume to mine subtle signals in Landsat time series, but as those signals become subtler, they are more likely to be mixed with noise in Landsat data. This study examines the similarity among seven different algorithms in their ability to map the full range of magnitudes of forest disturbance over six different Landsat scenes distributed across the conterminous US. The maps agreed very well in terms of the amount of undisturbed forest over time; however, for the ~30% of forest mapped as disturbed in a given year by at least one algorithm, there was little agreement about which pixels were affected. Algorithms that targeted higher-magnitude disturbances exhibited higher omission errors but lower commission errors than those targeting a broader range of disturbance magnitudes. These results suggest that a user of any given forest disturbance map should understand the map’s strengths and weaknesses (in terms of omission and commission error rates), with respect to the disturbance targets of interest. Full article

Tree breeders face the problem of negative correlations between wood properties and growth traits. It is necessary to overcome this difficulty in order to obtain promising genotypes. The selection index is one of the helpful tools in this process, because it allows multiple features of interest to be selected. In this study, a multiple trait selection index for Khasi pine (Pinus kesiya Royle ex Gordon) grown in Malawi was developed. Data on wood properties and growth traits were collected from six families of P. kesiya at the age of 30 years. The breeding objective was defined in terms of wood stiffness, wood strength and volume. Selection traits included in the index were wood stiffness (MoE), wood strength (MoR), volume (Vol.), wood density (WD), and diameter at breast height (DBH). The index was termed as $I_T=-80.36MoE-14.60MoR+132.07Vol.+4858.09WD-7.56DBH.$ The accuracy of the index was 98.8% and the correlation between the index and the aggregate breeding objective was 0.994. A genetic gain of 16.7% for volume, 14.8% for wood stiffness and 13.2% for wood strength would be expected from a standardized 10% selection intensity. Therefore, application of the developed selection index is necessary in order to increase the efficiency of the Pinus kesiya breeding programme in Malawi. Full article

Old-growth forests have become rare in North America but provide habitat for unique assemblages of species that often are rare in younger forests. Insects and related arthropods reach their highest diversity in old-growth forests because of their stable moderate temperature and relative humidity and the rich variety of resources represented by high plant species richness and structural complexity. Old-growth arthropod assemblages typically are distinct from those in younger, managed forests. Major subcommunities include the arboreal community that is composed of a rich assemblage of herbivores, fungivores, and their associated predators and parasitoids that function to regulate primary production and nutrient fluxes, the stem zone community that includes bark- and wood-boring species and their associated predators and parasitoids that initiate the decomposition of coarse woody debris, and the forest floor community composed of a variety of detritivores, fungivores, burrowers, and their associated predators and parasitoids that are instrumental in litter decomposition. Insect outbreaks are relatively rare in old-growth forests, where the diversity of resources and predators limit population growth. In turn, insects contribute to plant diversity and limit primary production of host plant species, thereby promoting development of old-growth forest characteristics. Arthropods also provide important functions in decomposition and nutrient cycling that may be lost in younger, managed forests with limited provision of coarse woody debris and accumulated litter. Protection of remnant old-growth forests within the forest matrix may be particularly valuable for maintaining the diversity of plant and arthropod predators that can minimize outbreaks, thereby contributing to resilience to changing environmental conditions. Full article

Mixed forest of Douglas-fir and beech has been suggested as one of the possible future forest types in Northwest Europe but the effects of this mixed forest on soil properties relative to monoculture stands are unknown. In a transboundary investigation of adjacent common garden Douglas-fir and beech stands, we determined the effects on topsoil properties. However, responses of C and N stocks, the C/N ratio and pH were site- and soil layer-specific and were mainly single-sided and without synergistic effects. Beech reduced the soil C and N stocks in Douglas-fir at the nutrient-poor site, caused an increase in the C/N ratio in the forest floor and mineral soil at both nutrient-poor and -rich sites, and reduced the acidifying effect of Douglas-fir at the nutrient-poor site. These results do not support the hypothesis that mixture effects would be consistent across sites and soil layers. The lack of synergistic effects may be attributed to the relatively similar litter quality or rooting depth that prevented any larger niche differentiation and complementarity. The results indicate that the transboundary approach within a mature common garden proved useful as a platform to test tree species interactions, and this approach could be explored in soil studies until dedicated mixed-species common gardens reach maturity. Full article

During the history of the Forest Service, human activity has been the dominant influence on climate and the environment; the time being called the Anthropocene. As we look ahead and strive to continue our mission of sustaining the health, diversity, and productivity of the Nation’s forests and grasslands to meet our current and future needs, we must be more flexible to focus our actions to better meet the contemporary conservation challenges now and ahead. During this era of intense human activity, a changing climate; development and loss of open space; resource consumption; destructive invasive species; and diversity in core beliefs and values will test our task relevant maturity—ability and willingness to meet the growing demands for services. The Forest Service is now on a transformative campaign to improve our abilities and meet these challenges, including forest resiliency through restorative actions. There are several things we must do to ensure we are brilliantly competitive to address the contemporary conservation needs along a complex rural to urban land gradient, now and ahead. The intent of this paper is to present one person’s view of what this “campaign of our campaign” should include. Full article

Multi-cohort stands are increasingly recognized and valued because of their biological functioning, biological diversity, and resistance and resiliency to perturbations. These forest ecosystems are epitomized by multiple age classes, and often contain multiple canopy layers, a range of tree size classes, and large amounts of woody debris. Disturbance history reconstructions in multi-cohort stands provide an understanding of the processes that create these systems. In this study, we documented structure and composition, and used dendroecological techniques to reconstruct disturbance history on a 1 ha plot in a multi-cohort hardwood stand in the Fall Line Hills of Alabama. The stand was dominated by Quercus alba L. and Liriodendron tulipifera L. Mingling index and stem maps indicated that most species were well dispersed throughout the stand, with the exception of L. tulipifera and Carya tomentosa (Poiret) Nuttal, which were relatively clustered. The oldest trees in the stand established in the 1770s, however, the largest recruitment event occurred ca. 1945 in conjunction with a stand-wide canopy disturbance. We posit that spatial heterogeneity of canopy removal during this event was largely responsible for the observed compositional and spatial complexity documented in the stand. In addition to the 1945 event, we recorded another stand-wide canopy disturbance in 1906 and 84 gap-scale disturbance events from 1802 to 2003. The conditions documented in the stand can be used as a benchmark to guide the creation and maintenance of complex multi-cohort stand characteristics, an increasingly popular management goal. Full article

Abstract: Climate and atmospheric changes affect forest ecosystems worldwide, but little is known about the interactive effects of global change drivers on tree growth. In the present study, we analyzed single and combined effects of nitrogen (N) fertilization and drought events (D) on the growth of European beech (Fagus sylvatica L.) saplings in a greenhouse experiment. We quantified morphological and physiological responses to treatments for one‐ and two‐year‐old plants. N fertilization increased the saplings’ aboveground biomass investments, making them more susceptible to D treatments. This was reflected by the highest tissue dieback in combined N and D treatments and a significant N × D interaction for leaf δ13C signatures. Thus, atmospheric N deposition can strengthen the drought sensitivity of beech saplings. One‐year‐old plants reacted more sensitively to D treatments than two‐year‐old plants (indicated by D‐induced shifts in leaf δ13C signatures of one‐year‐old and two‐year‐old plants by +0.5‰ and −0.2‰, respectively), attributable to their higher shoot:root‐ratios (1.8 and 1.2, respectively). In summary, the saplings’ treatment responses were determined by their phenotypic plasticity (shifts in shoot:root‐ratios), which in turn was a function of both the saplings’ age (effects of allometric growth trajectories = apparent plasticity) and environmental impacts (effects of N fertilization = plastic allometry). Full article

Leaf surface is a multifunctional interface between a plant and its environment, which affects both ecological and biological processes. Leaf surface topography directly affects microhabitat availability and ability for deposition. In this study, atomic force microscopy (AFM) and the resuspended particulate matter method were applied to evaluate the adsorptive capacity of the leaf surface. Patterns of particulate‐capturing capacities in different tree species and the effect of leaf surface features on these capacities were explored. Results indicated the following: (1) more total suspended particles (TSP) per unit leaf area were captured by coniferous tree species than by broad‐leaved tree species in a particular order—i.e., Pinus tabuliformis > Pinus bungeana > Salix matsudana > Acer truncatum > Ginkgo biloba > Populus tomentosa; (2) Significant seasonal variation in particulate‐capturing capacities were determined. During the observation period, the broad‐leaved tree species capturing TSP and coarse particulate matter (PM10) clearly exhibited a ∩‐shape pattern— that is, increasing initially and later on decreasing; meanwhile, the ∩‐shape pattern was not clearly shown in P. tabuliformis and P. bungeana. However, no obvious patterns in the absorption of fine particulate matter (PM2.5) were found in the tested tree species; (3) The leaf surface topography, as observed by AFM and scanning electron microscopy, revealed that the broad‐leaved tree exhibits a good correlation between micro‐roughness of leaf surfaces and density of particles settling on leaf surfaces over time. However, the main factors affecting the adsorptive capacities of the leaves in coniferous trees are the number of stomata as well as the amount of epicuticular wax and the properties of the cuticle in different seasons. Full article

Tropical forests play an important role in regulating the global climate and the carbon cycle. With the changing temperature and moisture along the elevation gradient, the Luquillo Experimental Forest in Northeastern Puerto Rico provides a natural approach to understand tropical forest ecosystems under climate change. In this study, we conducted a soil translocation experiment along an elevation gradient with decreasing temperature but increasing moisture to study the impacts of climate change on soil organic carbon (SOC) and soil respiration. As the results showed, both soil carbon and the respiration rate were impacted by microclimate changes. The soils translocated from low elevation to high elevation showed an increased respiration rate with decreased SOC content at the end of the experiment, which indicated that the increased soil moisture and altered soil microbes might affect respiration rates. The soils translocated from high elevation to low elevation also showed an increased respiration rate with reduced SOC at the end of the experiment, indicating that increased temperature at low elevation enhanced decomposition rates. Temperature and initial soil source quality impacted soil respiration significantly. With the predicted warming climate in the Caribbean, these tropical soils at high elevations are at risk of releasing sequestered carbon into the atmosphere. Full article

Acute Oak Decline (AOD) is a new condition affecting both species of native oak, Quercus robur and Quercus petraea, in Great Britain. The decline is characterised by a distinctive set of externally visible stem symptoms; bark cracks that “weep” dark exudate are found above necrotic lesions in the inner bark. Emergence holes of the buprestid beetle, Agrilus biguttatus are often also seen on the stems of oak within affected woodlands. This investigation assesses the extent to which the external symptoms of these two agents co-occur and reveals the spatial and temporal patterns present in affected woodland. Annual monitoring in eight affected woodlands showed that stem bleeding and emergence holes frequently occur on the same trees, with new emergence holes significantly more likely to occur when trees already have stem bleeds. Trials with coloured prism traps confirm A. biguttatus was present at all experimental sites. Beetle emergence is linked primarily to a few heavily declining trees, indicating that susceptibility may vary between hosts and that those with reduced health may be predisposed to AOD. Stem bleeds occur on trees in close proximity to the locations of trees with exit holes. Full article

Recent methods for detailed and accurate biomass and carbon stock estimation of forests have been driven by advances in remote sensing technology. The conventional approach to biomass estimation heavily relies on the tree species and site-specific allometric equations, which are based on destructive methods. This paper introduces a non-destructive, laser-based approach (terrestrial laser scanner) for individual tree aboveground biomass estimation in the Royal Belum forest reserve, Perak, Malaysia. The study area is in the state park, and it is believed to be one of the oldest rainforests in the world. The point clouds generated for 35 forest plots, using the terrestrial laser scanner, were geo-rectified and cleaned to produce separate point clouds for individual trees. The volumes of tree trunks were estimated based on a cylinder model fitted to the point clouds. The biomasses of tree trunks were calculated by multiplying the volume and the species wood density. The biomasses of branches and leaves were also estimated based on the estimated volume and density values. Branch and leaf volumes were estimated based on the fitted point clouds using an alpha-shape approach. The estimated individual biomass and the total above ground biomass were compared with the aboveground biomass (AGB) value estimated using existing allometric equations and individual tree census data collected in the field. The results show that the combination of a simple single-tree stem reconstruction and wood density can be used to estimate stem biomass comparable to the results usually obtained through existing allometric equations. However, there are several issues associated with the data and method used for branch and leaf biomass estimations, which need further improvement. Full article