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A long-distance edge effect influences structure of species-rich plant communities in temperate forest fragments surrounded by an agricultural landscape in Central Europe. Though the edge effect may be an aggregate of many environmental conditions, the thermal gradient from the forest edge to the forest interior deserves particular attention due to increasing ambient air temperature over the past decades. With regard to ongoing climate change, any reliable information about magnitude and distance of thermal gradients in these forest fragments has become of great importance. Therefore, we carried out seasonal measurements of forest air and soil temperature at a total 40 sites in 14 forest fragments in central Bohemia with areas ranging between 0.3 and 255 ha. In addition, we assessed spatial and vertical air temperature variability at two sites, on both south and north facing slopes. We found that differences in daily mean air temperature in these forest fragments is significantly modified by slope aspect (and/or slope inclination) and distance to the forest edge. A negative monotonic edge-related thermal gradient was apparent up to 100 m towards the forest interior with differences in daily mean air temperatures of about 0.3 °C. The magnitude of this edge thermal gradient is comparable to the effect of slope aspect. In addition to mean air temperature, maximum and minimum daily temperatures as well as mean soil temperature inside forest fragments also showed impacts caused by the edge effect and other environmental conditions (e.g. forest structure, elevation). The edge-related area closer than 100 m from the forest edge represents the majority (78%) of forested land in the study area as well as a considerable part of temperate forests in Central Europe (40%), including less fragmented mountain forests. Hence, the edge alteration of forest microclimate should be taken into serious consideration when planning adaptation measures against the consequences of climate change in Central Europe. The edge influence could be partially mitigated by preventing further forest fragmentation and the adoption of timber harvesting methods that avoid creation of clearings, such as single-tree selection. Even if such forest management measures are implemented in the study area, spatial patterns and gradients of environmental heterogeneity may be gradually reduced in the forest fragments as a result of further exposure to the combined effects of climate change and edge influence.

Forest management, including setting aside non-intervention forests, is currently debated as a measure to efficiently mitigate climate change. Temperate, old-growth forests are rare and the long-term effect of setting aside forest reserves, e.g. for habitat conservation, on forest carbon stocks and carbon sequestration remains uncertain. In this study, we assessed the five principal forest carbon pools in a semi-natural, temperate forest in Denmark and evaluated the changes in biomass and dead wood carbon stocks over 20 years. We also benchmarked the current carbon stocks against those in managed beech-dominated forests in the same region. In the most recent inventory, carbon stocks totalled 395 Mg ha−1 of which 47% was in above-ground live biomass, 11% in below-ground biomass, 9% in dead wood, 2% in the forest floor, and 31% in the top 75 cm of the mineral soil. Compared to similar, but managed forests in the same region, carbon stocks in above- and below-ground biomass as well as in dead wood were notably larger. However, analyses of above- and below-ground biomass and dead wood carbon stocks showed remarkable stability during the past 20 years, despite major disturbances in terms of windthrows and various pathogens. Despite the overall stability of carbon stocks we observed some significant spatio-temporal changes. Notably, the observed dynamics illustrate a general retreat of Q. robur and increasing dominance of F. sylvatica under a small-scale disturbance regime. The forest floor and soil carbon stocks averaged 131 ± 4 Mg ha−1 and were very similar to those of managed beech-dominated forests, suggesting little potential for soil carbon sequestration from setting forests aside as unmanaged. Our study has implications for selection of adequate forest management strategies to efficiently mitigate climate change as it confirms the large and persistent carbon stocks in old-growth forests compared to managed forests, but offers no evidence of continued carbon sequestration in old-growth forests.

Aboveground biomass (AGB) plays an important role in carbon cycle. Assessment of AGB presents a challenge in forest management. Reported studies have explored the potential of synthetic aperture radar (SAR) and multispectral instrument (MSI) data using random forest (RF) approach in AGB mapping. However, how AGB prediction would be affected by using data from different sources based on random forest kriging (RFK), which integrates RF and estimates residuals by ordinary kriging (OK), deserves further exploration. This study reported an assessment of multisensor data from Advanced Land Observing Satellite 2 (ALOS-2) L band and Sentinel-1C band SAR, Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), and Sentinel-2 MSI for forest AGB mapping using RFK. The effectiveness of 97 predictor variables derived from multisensor data was evaluated for AGB prediction in a temperate continental forest site in northeastern China. The assessment was tested by field-measured data from 1167 forest plots in 2017. The results showed that the RFK model achieved the accuracy with mean error, mean absolute error, root mean square error and correlation coefficient in –0.11, 19.37, 28.15 Mg ha−1 and 0.98, respectively. The study revealed that backscatters and texture features from ALOS-2 L band SAR and vegetation indices from Sentinel-2 MSI were primary contributors for explaining the observed variability of AGB. Topographic indices from SRTM DEM were more important than C band SAR backscatters and texture features. The accuracy improvement on forest AGB mapping by RFK over RF was more distinguished in models using a single sensor than those using multisensors.

The impacts of forest-related land use and management on soil organic carbon (SOC) stocks have been investigated through years of primary research and review articles. This attention is justified given the importance of land use and management to greenhouse gas mitigation, soil and forest productivity, and other ecosystem services. However, there is a gap of scale and scope between site-level studies that control for sources of variation, producing high-confidence results for limited locations, and the broad reviews that offer more general conclusions. The present analysis is intended to fill that gap. Here, we focus on six ecoregions of the eastern United States, and integrate meta-analysis of published literature with synthesis of geo-referenced soil observations to: (1) test whether common land use and management practices quantitatively impact SOC; (2) identify key sources of variation in these effects; (3) assess how sources of variation translate to decisions about land use and management at ecoregional to landscape levels. Results corroborate general trends, such as O horizon SOC losses with harvesting and fire and SOC gains during reforestation, but provide greater detail about the influence of specific practices and site-level controls on SOC stocks and change in the study region. Results also show that: (1) harvest impacts depend upon landform and soil taxonomy; (2) harvesting forests that are recovering on previously cultivated lands decreases SOC; (3) tree biomass and SOC recovery increase concurrently during reforestation; (4) specific harvest, site preparation, and fire management practices affect the magnitude and variability of changes in SOC. Perhaps more importantly, ecoregional classification and soil taxonomy provide spatial frameworks for placing quantitative estimates of SOC stocks and changes in the geographic context of the study region, providing greater detail and specificity for individuals and institutions concerned with SOC management at more localized levels.

Coastal Alaska forests consist of 2.6 million hectares of productive timberland and constitute the largest terrestrial carbon reservoir in the state. It has become increasingly urgent to understand potential climate-induced changes in forest structural and species composition in this region. Based on in situ data from 544 permanent sample plots (PSPs) for calibration and 244 PSPs for validation, we developed a climate-sensitive density-dependent, species-, and size-specific matrix model (CSMatrix-AK), to predict fine-scale dynamics of coastal Alaska forests from the present to Year 2100 under three climate scenarios – Representative Concentration Pathway (RCP) 4.5, RCP6.0, and RCP8.5. With post-sample validation, we showed that the CSMatrix-AK model was more accurate than other existing models for the region. Under low-intensity and high-frequency stochastic shocks which represented natural disturbances typical for the region, we projected a gradual decline of Sitka spruce, a major commercial species in the region, and a significantly lower level of total stand basal area under all three climate scenarios. The results suggest that timber industry, landowners and managers, policymakers, and local communities will need to prepare for substantial impacts of climate change on Coastal Alaska forests and the regional forestry sector. Our CSMatrix-AK model provides a useful tool to better inform the stakeholders of such changes and lays the foundation for adaptive forest management to sustain forests and associated ecosystem services in the region.

Norway spruce (Picea abies), European beech (Fagus sylvatica), silver fir (Abies alba) and Scots pine (Pinus sylvestris) typically co-occur in European forests, but show contrasting response to climate and environmental change. Sustainable forest management therefore depends on species- and regional-specific information. Here, we use tree-ring width measurements of 334 beech, 280 fir, 144 spruce and 63 pine trees from 75 inventory plots in Slovakia to assess the predominant factors that control radial stem growth of Europe’s economically most important forest species. All four species exhibit significant shifts in stem growth over the past 100 years. Ring width patterns were, however, not significantly affected by tree species diversity and site elevation. The resistance, resilience and recovery of all species to the extreme summer droughts between 1950 and 2003 suggest that spruce is the species most unsuitable for the predicted warmer and drier future. Silver fir may benefit from warmer conditions, although we cannot conclude that it will not suffer from predicted increased frequency of climate extremes. Forest management in this locality should aim to avoid significant loss of forest cover by replacing Norway spruce monocultures with mixed stands of silver fir and European beech.

Wind is a natural disturbance factor in boreal and temperate forests having large ecological and economic consequences. We investigated recovery processes in forests severely damaged by windthrow, by conducting a systematic quantitative literature review of 34 case studies. We addressed three questions on forest ecosystem recovery: (1) Which forest regeneration processes dominate forest recovery after windthrow? (2) Which structures and processes enhance or impede forest recovery after windthrow? (3) Does salvage logging after windthrow influence forest recovery? Our analyses showed that the main focus of the reviewed studies was on post storm seedling regeneration and survival. Advanced regeneration from suppressed seedlings or saplings also played an important role in the studies, especially for shade tolerant species and in the boreal biome. Pits and mounds and coarse woody debris played an important role for the establishment of Picea sp., especially in the studies from the boreal biome, whereas in the temperate biome game interference and competition from ground vegetation seemed to be the most important influencing processes. Salvage logging mostly acted as a subsequent disturbance after the windthrow, pushing the forest ecosystem towards an earlier successional stage, hereby impeding recovery. In none of the studies however, did the windthrow nor the consequent salvaging halt recovery completely, confirming the resilience of forests as the dominant vegetation type in these biomes. Based on our results forest management implications are discussed.

Prescribed burning has become more common for the management of eastern forests in North America, so understanding if and how foraging bats respond to structural changes generated by fire is of increasing importance. Our objective was to investigate the effects of post-fire landscape conditions on the occurrence of foraging bats in mixed forests of the Cumberland Plateau physiographic region. We deployed Anabat II bat detectors in 164 paired burned and unburned forest sites for ≥2 nights from mid-May through August 2014 and 2015 to monitor bat foraging and commuting habitat use. We conducted vegetation surveys to quantify site-specific structural characteristics, which indicated that measures of structure were significantly lower in burned sites than unburned sites. We used Program Presence to test a priori hypotheses of species-specific probability of detection and site occupancy related to weather, burn history (i.e., site burned within the past 10 years or unburned), and site and landscape characteristics. Bats were detected at 94% of burned sites and 83% of unburned sites. Probability of detection was affected by weather conditions, vegetative structure, and burn history for most species. Occupancy for all species/species groups examined was positively associated with burning and generally associated with lower vegetative structure. Although burn severity did not affect most species groups, occupancy of Myotis species and tri-colored bats (Perimyotis subflavus) was lower in sites that received moderate severity burns than in sites that received low severity burns. Therefore, while prescribed fire may provide vegetative structure conducive to efficient foraging for all bats of the Cumberland Plateau, our results demonstrate that retaining some unburned forests while creating mosaics of lower and higher severity burns across the landscape will result in favorable foraging conditions for all resident bat species.

Understory vegetation biomass (UVB) is necessary for forest stability and supply of numerous forest ecosystem services (FES). However, UVB is often ignored in traditionally managed overly dense plantations. A tradeoff approach between the overstory biomass (OB) and UVB, based on the quantitative evaluation of overstory stand structure effects on UVB, was examined using 82 sample plots of larch (Larix Principis-rupprechetii) plantation in the Liupan Mountains (LPM), northwest China. Results showed that with rising tree density at given age, the single tree biomass decreased, but the OB increased. The UVB decreased significantly with rising OB. The optimal canopy density of 0.7 was suggested to balance OB and UVB. The corresponding proper tree densities calculated using fitted model were about 2600, 2000, 1600, 1250, 1000 trees/ha for the ages of 15, 20, 25, 30, 35 years, respectively. These proper tree densities lead to an increase of single tree biomass by 0.8%, 4.1%, 3.9%, 4.1%, 5.5%, an increase of UVB by 0.9%, 10.1%, 16.1%, 32.2%, 88.5%, but a decrease of OB by 2.9%, 13.26%, 12.5%, 13.3%, 18.5%, compared with the stands having the maximum tree densities of 2700, 2400, 1900, 1500 and 1300 trees/ha. The study can help to guide the multifunctional forest management and to uplift FES of degraded plantation.

Forests in the interior of British Columbia, Canada have seen a substantial change in age class structure caused by a mountain pine beetle outbreak that instigated high tree mortality, and consequently, large scale salvage operations. The current age class structure in affected regions implies a midterm timber supply shortage that has the potential to negatively impact the forest industry in affected timber supply areas in the near future. A spatially explicit landscape level forest model for Bulkley timber supply area (TSA), a typical TSA facing these challenges, was developed. Using landscape level planning software we modelled future timber supply as well as age class structure over a 250-year planning horizon for (a) current single entry forest management practices focusing mainly on clearcutting; and (b) alternative management scenarios using multi-entry (thinning) approaches. Alternative scenarios were designed to determine economically viable forest management alternatives while mitigating midterm timber supply shortage, and converting the forest structure in the region towards a more even age-class distribution. Implementing commercial thinnings in stands located within 300 m of existing roads showed the highest potential to successfully mitigate midterm timber supply shortage if entries were scheduled based on culmination of mean annual increment rather than on a fixed minimum harvestable volume. The use of thinnings shortened the overall duration of the midterm timber supply shortage, reaching sustainable harvest levels sooner than if conventional approaches were used, and higher overall timber volumes available for harvest. Alternative approaches to current forest management practices in BC prove to be promising and should be considered where possible.

From a forest management stand point, it is crucial to know which ecological processes are most likely to drive changes in tree species distributions and abundance under warming climate conditions. In this study, we simulated forest dynamics in a 703,580 km2 territory that straddles the boreal and temperate broadleaved forest biomes in the province of Quebec (Canada), under a RCP 8.5 climate change scenario. The objective was to evaluate how future forest composition is sensitive to variation in four potential drivers: fire regimes, harvesting regimes, the capacity of tree species to persist under warmer climate conditions, and species capabilities for long-distance colonization. The results indicate that forest composition in 2100 is most sensitive to variation in the parameters controlling species persistence when conditions become warmer or dryer than the conditions found in their current range. Concretely, this points to avenues of research to improve the accuracy of our predictions regarding the impacts of climate change on forest composition. For instance, we should further investigate the underlying ecological (competition) or physiological (drought stresses) processes that influence tree species persistence at the receding edge of their current distributions.

Many long-term forestry water quality studies focus on the impact of the harvesting phase of forestry operations. As a result, the water quality impacts of other activities such as forest (re)planting, thinning and fertilising are less well understood. Here we report the results from 23 years of monthly water quality monitoring from a steep headwater catchment within the Waikato region, New Zealand. Three experimental sub-catchments were planted in different proportions of Pinus radiata (PW2 = 100%, K-Pine 57%; PW3 = 36%). PW2 and PW3 were historical pastoral sites in the first rotation of plantation forestry and K-Pine was harvested and subsequently planted in a second rotation of forestry. All sites underwent two phases of stand thinning six and eight years after planting. The most significant effect of forestry was the increase in nitrate-N (NO3-N) and total nitrogen (TN) concentrations in response to both stand planting and stand thinning operations. Planting resulted in significant increases in NO3-N, TN and DRP over a four-year planting period at PW2. Significant increases in NO3-N and TN were detected over a four-year thinning period, at all three experimental sites. We propose that stream NO3-N and TN concentrations increased in response to stand planting at PW2 because of the change in physical conditions (e.g. increased stream shading, proliferation of nitrogen fixing weeds and decreased spatial extent of seepage wetlands) caused by the change in land use. Increasing nitrogen concentrations due to decreasing stream runoff could also be contributing a factor. Any decrease in NO3-N and TN concentrations in response to increased uptake by the rapidly growing P. radiata appears to have been masked by these other factors. However, the increase in NO3-N and TN concentrations in response to stand thinning at all three experimental sites suggests that NO3-N uptake by growing trees is an important process. Over the entire forestry period, median NO3-N concentrations at PW2 (first rotation site) increased by a factor four (400–1590 µg l−1). The median NO3-N during the post-thinning period was also one order of magnitude higher than those measured at K-Pine (second rotation site) during the post-thinning period. We attribute these differences to the NO3-N legacy within soil and/or groundwater of the previous sheep and beef cattle grazing land use. Long-term use of the PW2 catchment for forestry may eventually reduce NO3-N concentrations to the lower levels measured at K-Pine. Therefore, while NO3-N concentrations and loads may increase in response to the establishment of plantation forestry we envisage that these will decline if plantation forestry continues beyond the first rotation. This research highlights: (i) the complex nature of the response of stream water quality to catchment land use changes, and (ii) the value of studies that monitor the impact of land use/cover change over the long-term.

Tree species mixing has become a crucial tool in European forest management as positive interactions between species have been found to promote the provision of multiple ecosystem services, while at the same time reducing the risks associated with climate change. However, mixing effects have proven to be strongly context-dependant and some species combinations have still not been studied in detail. Here we focus on mixed forests of Scots pine and oak, which are likely to become increasingly popular for balancing wood production and other ecosystem services under climate change. Using 20-year growth data from newly established triplets in Germany and Denmark, this study investigates how mean tree and stand characteristics as well as productivity in mixed Scots pine-oak stands compare with adjacent monocultures and how stable the observed productivity relation is, considering inter-annual variations in local climate. Species mixing on average resulted in 15% higher standing volume and 14% higher volume productivity compared with the weighted mean of the adjacent monocultures. Oak profited most in mixture, showing overyielding of 19%. Overyielding on the stand and species level increased in years with higher water supply. In mixture, standing volume of Scots pine was 25% higher than in monocultures. Both species were found to modify their morphology in mixture. Oak in mixture showed a significantly higher inequality in stem volume compared with monocultures. We hypothesise that the observed overyielding of Scots pine-oak mixtures mainly results from complementary light use, where differences in shade tolerance, crown architecture and leaf phenology may be contributing factors.

Understanding the impacts of large-scale disturbances on forest conditions is necessary to support forest management, planning, and policy decision making. National forest inventories (NFIs) are an important information source that provide consistent data encompassing large areas, covering all ownerships, and extending through time. Here we compare how temporal aggregation approaches with NFI data affects estimates of standing dead trees as these respond to extreme disturbance events. East Texas was selected for this study owing to the occurrence of three significant disturbance events in a short span: Hurricane Rita in 2005, Hurricane Ike in 2008, and a historic drought in 2011. Wide-spread tree damage and mortality were reported after each disturbance and estimates of standing dead trees were used as the inventory variable for assessment. In the NFI of the US, the plot network is systematically divided into panels and one panel is measured each year. A measurement cycle is completed when all panels have been measured, which varies between 5 and 10 years depending on the region. Using the standard estimation approach of the US NFI, we computed population estimates using data from the full set of panels (FSP), multiple sets of panels (MSP), and single set of panels (SSP). For estimation, a single plot observation is computed from the most recent measurement of the plot that does not exceed the estimate year. Because one panel is measured per year, FSP and MSP estimates will necessarily consist of plot observations whose measurements were collected over a number of years. The SSP estimate is computed from one panel and thus all the plot observations are based on measurements collected over one year. We found that interpretations of disturbance event impacts varied depending on which sets of estimates were considered. All sets of estimates suggested a large and significant drought impact. However, differences existed among the estimates in the timing and magnitude of the impacts. The FSP estimates showed clear lag bias and smoothing of trends relative to the SSP estimates. MSP estimates were intermediate between FSP and SSP estimates. Differences in Hurricane Rita impacts were also observed between sets of estimates. Evidence of a net impact on standing dead trees following Hurricane Ike was weak among all sets of estimates. Given the potential for lag bias and smoothing, we recommend that SSP and MSP estimates be considered along with FSP estimates in assessments of large-scale disturbance impacts on forest conditions.

The use of tree height to estimate forest volume allows the calculation of forest biomass at large scales, and this calculation is of great importance in forest management and carbon accounting for temperate forests. Additionally, LiDAR (Light Detecting and Ranging) shows an increasing dependence on tree height in large-scale forest volume or biomass estimation and carbon accounting. However, the extent to which tree height determines forest volume remains controversial. Additionally, how the relationship between stand volume and tree height is modulated by canopy density has seldom been quantified at large scales across different forest types. This relationship may be important for improving large-scale forest volume or biomass estimations based on LiDAR technology. In this study, based on national forestry inventory data from China containing 34,130 forest plots, we examined the effect of canopy density on the relationship between tree height and stand volume across different forest types. The results showed forest height alone explained 72.9% of variation in stand volume across China and was far more powerful than canopy density (R2 = 49.7%). However, the relationship between stand volume and forest height was significantly affected by canopy density. When the effect of canopy density was included in the model, stand volume could be well predicted from forest height, with an R2 of 0.863. In closed-canopy stands, tree height could explain 91.5% of stand volume at a canopy density of 1.0. In conclusion, we provided the first national-scale model for estimating stand volume from forest height and canopy density across China with a large number of field-measured plots. The results were a robust predicted combination for forest volume, regardless of biotic and abiotic factors, in national scales across different forest types in China. Therefore, they can be utilized by LiDAR or other remote-sensing studies in the future.

To estimate carbon emissions from selective logging in Central Africa, we employed the reduced-impact logging for carbon emissions reductions (RIL-C) protocol to quantify baseline carbon emissions from legal timber harvests by source (i.e., hauling, skidding, and felling). We modeled the relationships between emissions and biophysical conditions, logging practices, and forest policies and then used these models to estimate potential emission reductions from full implementation of RIL-C practices. We applied the method in 8 forest management enterprises (FMEs; i.e., concessions) in the Democratic Republic of Congo (DRC), 9 in Gabon, and 6 in the Republic of Congo (RoC). Committed logging emissions expressed per cubic meter of timber harvested (to control for differences in logging intensities) ranged from 0.63 Mg C m−3 in a FME in RoC to 4.8 Mg C m−3 in a FME in Gabon, with an overall average of 2.1 Mg C m−3. Logging emissions were dominated by damage caused by road and log landing construction (i.e., hauling; 50%) and felling (43%; includes carbon in extracted logs). Total emissions represented only about 9% of unlogged forest biomass carbon stocks. Average emissions were highest in Gabon (2.65 Mg C m−3) followed by DRC (1.84 Mg C m−3) and RoC (1.54 Mg C m−3). Emissions from concessions certified by the Forest Stewardship Council (FSC, N = 6) and those that were not certified (N = 17) did not differ. Nearly half (51%) of logging emissions could be avoided without reducing timber yields if all best examples of RIL-C logging practices observed were applied in the same FME. At the country level, if all FMEs were to utilize these practices, emissions reductions would be 34% in RoC, 45% in DRC, and 62% in Gabon. When combined with country-level logging statistics, emissions from selective logging as currently practiced in the six countries of the Congo Basin are equivalent to 40% of the region’s total emissions from deforestation.

We followed how forest thinning, repeated twice during a period of 93 years, altered understorey plant community composition, affected the succession of forest understorey vegetation and the accumulation of logs in the long-term. The study was carried out in northern Finland by resampling 20 permanent experimental plots, established after a wildfire in 1920. Understorey vegetation was inventoried in 1961, 1986 and 2013 with forest thinning treatments done in 1953 and 1987, using four and three different harvesting intensities, respectively. We found succession to override the effects of forest logging until the latest study period (2013). We observed negligible long-term effects of logging on understorey communities during the two mid-successional stages (1961, 1986), when the forest was 41 and 66 years old respectively. The impacts of logging on understorey vegetation were strongest in the latest successional stage (2013), the forest being at the age of 93 years. In the latest successional stage (2013) logged plots had less coarse woody debris than unlogged plots. Forest management thus influenced the key feature for forest biodiversity and potential habitats for endangered species. These findings are of major interest since the studies of long-term impacts of less intensive forest management practices are scarce. Our results suggest that in addition to possible immediate impacts, harvesting treatments have legacy effects (subtle or delayed inherited effects of forestry in the past) that influence the forest understorey vegetation community composition and the amount of coarse woody debris. This finding deserves special attention when planning of species conservation, multiple use of forests and sustainable forestry.

Forest processes that play an essential role in carbon sequestration, such as light use efficiency, photosynthetic capacity, and trace gas exchange, are closely tied to the three-dimensional structure of forest canopies. However, the vertical distribution of leaf traits is not uniform; leaves at varying vertical positions within the canopy are physiologically unique due to differing light and environmental conditions, which leads to higher carbon storage than if light conditions were constant throughout the canopy. Due to this within-canopy variation, three-dimensional structural traits are critical to improving our estimates of global carbon cycling and storage by Earth system models and to better understanding the effects of disturbances on carbon sequestration in forested ecosystems. In this study, we describe a reproducible and open-source methodology using the R programming language for estimating leaf area density (LAD; the total leaf area per unit of volume) from airborne LiDAR. Using this approach, we compare LAD estimates at the Smithsonian Environmental Research Center in Maryland, USA, from two airborne LiDAR systems, NEON AOP and NASA G-LiHT, which differ in survey and instrument specifications, collections goals, and laser pulse densities. Furthermore, we address the impacts of the spatial scale of analysis as well as differences in canopy penetration and pulse density on LAD and leaf area index (LAI) estimates, while offering potential solutions to enhance the accuracy of these estimates. LAD estimates from airborne LiDAR can be used to describe the three-dimensional structure of forests across entire landscapes. This information can help inform forest management and conservation decisions related to the estimation of aboveground biomass and productivity, the response of forests to large-scale disturbances, the impacts of drought on forest health, the conservation of bird habitat, as well as a host of other important forest processes and responses.

Grizzly bears should benefit from forest harvesting strategies that emulate patterns of natural disturbance, such as wildfire, presumably because of increased foraging opportunities associated with open and edge habitats. Several studies have linked early seral habitats associated with natural and anthropogenic disturbances to increased food supply for grizzly bear. However, few have quantitatively evaluated whether food supply is higher along forest edges, particularly edges created by different forest harvesting strategies such as structure retention. Here we tested whether grizzly bear food supply was: 1) more common/abundant along forest harvest (cutblock) edges; 2) similar between undisturbed forest matrix (uncut) undisturbed forest remnants (i.e., retention patches) that were situated within forest harvests; and 3) similar in terms of responses relative to retention and forest harvest edges. To address these questions, we measured the distribution and abundance of plant-based food resources used by grizzly bears along edge distance gradients associated with to three forest treatments (cutblock, uncut forest, and retention patch) in Alberta, Canada. We then used information theory to compare models and evaluate support for factors. We found that blueberry (Vaccinium membranaceum, V. myrtilloides, and V. vitis-idaea.) shrubs, which are known to be sensitive to mechanical damage and soil disturbance from harvest and post-harvest site preparation, were more common/abundant near young ( ≤ 20 years) forest edges. Conversely, raspberry (Rubus idaeus) shrubs, horsetail (Equisetum arvense), and cow parsnip (Heracleum lanatum), which are known to be positively associated with soil disturbance, were generally more common/abundant away from forest edges. Blueberry, fruit production was highest at forest harvest edges and lowest in older cutblocks, as well as retention patches, which we showed contained fewer lodgepole pine (Pinus contorta) trees and more deciduous species. These results support the contention that understory disturbance, environmental conditions (e.g. light availability), and forest tree species composition could explain our research findings. As part of stand-level prescriptions, we recommend that forest managers consider maintaining uncut forest adjacent to cutblocks for up to 20 years post-harvest, and create more and smaller retention patches to increase the amount of forest edge. We also recommend that criteria be developed for selecting the spatial location of forest edges and retention patches such that blueberry shrubs are common/abundant in the undisturbed forest. This research demonstrated that forest harvesting strategies can increase food supply for grizzly bears and thus support recovery efforts of this provincially threatened species.

Global change threatens the persistence of native forest ecosystems mainly by limiting the conditions for natural regeneration but also inducing tree mortality and increasing the risk of large wildfires. In this context, understanding the biotic and biotic factors that ultimately determine tree recruitment is of pivotal importance to implement adaptive forest management strategies. In this study we assess how multipurpose management strategies, including combinations of thinning intensities and prescribed burning, affect the seed emergence and seedling survival of Pinus nigra Arn. subsp. salzmannii in two different forest sites in NE Spain. We tested four overstorey and fuel treatments that combined heavy and light intensity thinnings from below with understorey clearing and two different treatments of the resulting slash: prescribed burning and lop and scatter. The results showed: (1) a lack of regeneration in control units, probably caused by the high density of canopy and understorey; (2) greater seedling recruitment in units treated with slash burning than in units treated with slash lop and scatter, probably due to the effects of prescribed burning on the herbaceous layer, soil organic layer, nutrient pools, and understorey; and (3) a different regeneration response between sites for treatments that included prescribed burning, probably due to microclimatic conditions during the experiment and differences in the characteristics of the prescribed burns. These findings indicate the potential effectiveness of combined treatments of thinning and slash burning in the context of the implementation of multipurpose management actions in endangered ecosystems adapted to low intensity fires.

Clear-cutting is a conventional method of forest management which significantly changes carbon (C) cycling at the ecosystem level for a long time. Estimation of the interim period during which the ecosystem turns from a C source to a C sink is crucial for clarifying the environmental effects of management on forest C cycling. The current study provided new knowledge of C cycling in young pine stand and demonstrated the recovery of C sequestration of the forest ecosystem during the post harvesting period. We estimated the C balance in a 6-year-old Scots pine stand by using two different methods: carbon budgeting, for estimating annual net ecosystem production (NEP), and eddy covariance (EC), for estimating net ecosystem exchange (NEE). For C budgeting, the above- and belowground biomass production of the ecosystem, as well as the soil heterotrophic respiration efflux at the studied site was estimated. Annual NEE at the studied young forest ecosystem was 1.19 ± 0.36 t C ha−1, gross primary ecosystem production was 9.87 and total ecosystem respiration was 11.06 t C ha−1. Estimated NEE was in good accordance with the results of NEP (1.37 t C ha−1), which confirms the relevance of the C budgeting method. Increased annual woody biomass production is the main factor which induced the young Scots pine ecosystem to act as a C sink: annual C accumulation in tree biomass in a 6-year-old stand was 1.0 t C ha−1 but reached already 2.4 t C ha−1 in the following year. Assuming that the annual Rh flux is of the same magnitude in the subsequent years, the ecosystem will become a C sink already during a short period after clear-cut. Annual soil respiration (Rs) and heterotrophic soil respiration (Rh) were 6.0 and 4.2 t C ha−1, respectively and the Rh/Rs ratio was 0.70. However, at this stage also the understorey vegetation contributed essentially to NEP, making up 56% of the annual C uptake accumulated in the plants. The methane flux and the leached C flux were negligible, 0.004 and 0.015 t C ha−1 yr−1, respectively. Our results demonstrate that well regenerated young Scots pine stand on a former clear-cut area will be able to turn into a C sequestering ecosystem already before ten years after cutting.

Tropical forests account for a substantial percentage of the world’s carbon stocks, but the consequences to carbon storage of the rapid invasiveness of the guava tree in these forests is not known. Two different forest management strategies are practiced in a tropical forest in western Kenya: (1) a protection strategy where human entry is prohibited except for minimalistic human presence (e.g., research activities); and (2) a conservation strategy where human access to the forest and its resources are permitted. We assessed the effects of these management strategies and different levels of disturbance caused by the legacy effects of legal logging activities and the contemporary effects of unauthorized harvesting of forest products on the abundance of guava and non-guava trees and carbon storage in both plant biomass and soil in this forest. We found that guava trees were less likely to thrive and carbon storage in plants and soils was similar in sites with minimal disturbance under both the protection and conservation strategies. However, as disturbance increased, whether by the historical or contemporary effects of human activities, guava trees were more likely to thrive and carbon storage in plants shifted from non-guava trees to guava trees, but without an effect on more stable soil carbon. We conclude that regulations should be strictly enforced to prevent all logging activity, but the conservation strategy would provide similar effects on both forest plant and soil carbon to the protection strategy, while providing benefits to the surrounding community who rely on the forest for cultural and spiritual nourishment.

Forest ecosystems act as a carbon sink and contribute to climate change mitigation. Research on the spatiotemporal patterns of C storage and density in forest ecosystems is essential to understand the role of forest ecosystems in the C sink and is helpful to select the efficient forest management practice to maximize the C sequestration potential. We quantified the C storage in forest ecosystems in Hunan Province in southern China over two decades by combining forest inventory data with field survey. The C storage in forest ecosystems in Hunan Province increased from 820.2 Tg to 1277.8 Tg over the two decades, with 457.6 Tg (134.4 Tg in vegetation and 323.2 Tg in soil) of C sequestration in the forest ecosystems. Forest C storage increased sharply from 1996 to 2007, but slowly from 2007 to 2015. The mean annual C sequestration was 25.8 Tg yr−1, with 19.0 Tg yr−1 in soil and 6.8 Tg yr−1 in vegetation. The C density in forest ecosystems increased from 110.3 Mg ha−1 in 1996 to 130.8 Mg ha−1 in 2013. C densities varied in forest types, with the highest value in evergreen broadleaved forest ecosystems. The uneven spatial distributions of forest C storage, density, and sequestration in Hunan Province exhibited similar pattern with the highest in the western Hunan and the lowest in the central Hunan. The forest ecosystems in Hunan Province present a significant C sequestration potential (1321.5 Tg, including 1029.2 Tg in biomass C and 292.3 Tg in soil C), given the proportion of the area of young and middle-aged forests (71.3%). To maximize the C sequestration potential of forest ecosystems in Hunan Province, future forest management should focus on the conversion of forest type, the selection of tree species in reforestation, and the prevention of adverse human disturbances in young and middle-aged forests.

Forest management is increasingly focused on enhancing native biodiversity. In temperate forests, a common goal is to increase native plant diversity of the ground flora and silvicultural treatments such as thinning and prescribed burning are often used alone or in combination to achieve this goal. These treatments often increase understory light availability, decrease litter depths, and increase nutrient availability. We examined the effects of thinning without fire and thinning with different fire frequencies (four burns on a three year return interval and two burns on a nine year return interval) to identify changes in community structure and species composition with a focus on taxonomic richness, diversity, and cover of ground flora in post-agricultural Pinus-hardwood stands on the Cumberland Plateau in Alabama, USA. This paper reports on one year of post-treatment data (two years post burn) within a longer-term study of thinning and repeated burns. Overstory basal area and density were lower with increased management intensity. Sapling density was substantially greater with increased management intensity; however, this did not affect ground flora richness, diversity, or cover. Ground flora richness, diversity, and cover were greatest in stands that were thinned and burned every three years, and these measures were negatively correlated with litter depth and positively correlated with exposed mineral soil in a non-metric multidimensional scaling (NMS) solution. Our results signify the need for a combination of thinning and burning in these systems. Forest managers that wish to promote native plant diversity in similar systems may consider thinning and frequent burning to increase light availability, decrease litter depth, and promote ground flora richness, diversity, and cover.

There is increasing concern, to what extent production forests in the Neotropics are sustainably managed. The implementation of effective forest management strategies that are ecologically beneficial plays thus a central role to prevent forest degradation. However, to identify effective forest management strategies, there is a need for methods supporting the decision-making process. The main objective of our study is to analyze the mid- and long-term impacts of different management intensities, such as varying the minimum stem diameter of harvestable commercial trees, on the dynamic and structure of a species-rich tropical lowland forest of French Guiana. Therefore, we have applied the management module of a dynamic forest model and analyzed simulation experiments for undisturbed forest growth and selective logging. For the first time we were able to quantify the mean recovery times of multiple ecosystem functions and properties (biomass, gross primary production, leaf area index, Shanon diversity, timber volume) after selective logging. Accordingly, we validated simulation results (biomass, number of trees harvested) of selective logging with forest inventory data from the last 32 years. The forest model reliably reproduces the observed pre-logging biomass, tree-size distribution, and logging intensity (10 trees/ha, 39 m3/ha). In addition, it became clear how strongly management with higher logging intensities influences the forest in the long term: (1) the mean recovery times of the investigated ecosystem functions were significantly extended. With very intensive logging (116 m3/ha), the average recovery time of forest biomass was almost twice as long as in a moderate simulation scenario (tint 138 a, tmod 77 a). Similar patterns were observed for other ecosystem functions, e.g. timber volume (tint 158 a, tmod 62 a). (2) Additionally, the functional composition shifted, as up to 30% pioneer tree species in particular invaded the forest. This innovative use of forest growth models may help in the development of ecologically reasonable forest management strategies.

This study is aimed to address the issue of whether the volume loss in stands with partial cutting such as pre-commercial thinning ( PCT ) treatments could catch-up with the ones of unthinned stands, employing the lens of compensatory growth (CG) in plant ecology to ask the question of how long one could expect to see the complete CG to happen, if any. CG is the ability of plants or vegetation to vary their growth to offset damage caused by disturbances. Though it has been demonstrated in annual plants such as crops and grasslands, it has not been well studied in trees except Douglas-fir under different PCT regimes in the Swiss Central Plateau, trembling aspen seedlings under different fertilization regimes, and fast-growth willow coppice with clipping, etc. Our data from a long-term silvicultural trial (combined PCT and fertilization) near Shawnigan Lake, Vancouver Island, British Columbia, Canada, demonstrate complete CG in coastal Douglas-fir 40 years after treatments at both the tree and stand levels. We present a method of estimating the length of time required to achieve complete CG in stand volume. Our results also show that different patterns of complete CG could be expected under different site conditions differentiated by levels of fertilization. Without fertilization a long length of time would be required to reach complete CG, and the length of time could be reduced by increased fertilization application. Potential forest management implications are discussed including possible alternative shapes of yield curves for managed stands and hence the forecast of future wood supply, positive economic evaluation of PCT and fertilization, and contribution to regional carbon budget.

Windthrows are natural disturbances that influence the functioning and structure of forest ecosystems and the belowground components of an ecosystem. Soil processes such as the recycling of organic matter, energy and nutrients are controlled by soil fauna. However, little is still known about the post-disturbance recovery of soil microarthropod communities in forest stands exposed to windthrow of various severity and post-windthrow forest management over time. This study assessed soil Collembola community recovery in pine forest stands over the long-term (between 9 and 14 years after the disturbance event). We predicted that (1) different severity of windthrow disturbance in a pine forest has different effects on the recovery of Collembola community composition and functional structure, even after 10 years; (2) The recovery of Collembola communities is similar during regeneration of a forest disturbed by windthrow and in a pine plantation planted after clearing of a windthrown forest and subsequent soil preparation; (3) The changes in the Collembola community during forest regeneration after windthrow disturbance can be explained by selected environmental variables, especially the leaf area index LAI. As expected, regeneration processes within forest stands shifted the species composition of collembolan communities and changed their functional structure. The surface dwelling collembolan species (epigeic and atmobiotic life form) responded to regeneration processes mainly in pine stands, especially in a pine plantation established after a clearing of broken pines and subsequent soil preparation. Our results suggest different sensitivity of collembolan communities to environmental changes induced by various degrees of opening of the tree canopy by windthrow and to those caused by the post disturbance treatment. These findings confirm that collembolan community composition recovery is slow and divergent during natural regeneration of pine stands and regeneration by planting but does not differ between moderately and severely successional trajectories. Our results also confirm the importance of canopy closure for the possibility of Collembola community regeneration. If canopies were more closed (higher leaf area index, LAI index), the possibility of regeneration increased, especially in the young pine plantations, as seen in the final years of our study.

Forest management strongly influences the carbon (C) budget of boreal forests and their potential to mitigating greenhouse gas emissions. A better quantification of the net changes of carbon pools with time since harvesting is necessary to guide the development of climate-friendly forest management practices. The objective of this study was to assess the evolution of forest C pools, with a special focus on detrital biomass, in an 80-year post-harvesting chronosequence consisting of 36 very homogenous stem-only harvested plots from a humid boreal balsam fir forest of eastern Canada. Dead wood C stocks comprised of snags, stumps, downed woody debris and buried wood averaged 37 Mg C ha−1 and evolved according to an upward-facing «boomerang» shape pattern throughout the chronosequence (rapid decrease in the first years followed by a constant increase until the end of the time horizon). In contrast, soil C stocks (FH and mineral) averaged 156 Mg C ha−1 and remain constant through time. Stand C sequestration increased rapidly in the early stages up to age 50 when it reached about 250 Mg C ha−1, and then continued to accumulate at a slower rate. The temporal trends observed in C pools suggest that C originating from aboveground dead wood (snags, stumps, downed woody debris) is either leaving the system (respired or leached) or transferred into buried wood, and does not appear to influence the C stocks of the fine fraction of the organic and mineral soil horizons. However, the ultimate fate of dead wood C is still poorly understood and further research is needed in this field. We recommend fixing the length of harvest rotation at a minimum of 50 years for this ecosystem to allow the build-up of its dead wood capital, and to promote dead wood retention on site. We also recommend including buried wood in carbon inventories as this pool represents an important share of the detrital C stock in these humid boreal forests.

Longleaf pine (Pinus palustris Mill.) forests are historically and ecologically important and also endangered ecosystems in the southeastern United States. In addition to extensive exploitation and land use conversion, one characteristic which contributed to their dramatic decline and presents a continuing challenge to their future recovery is the sporadic timing of their seed production. In this study, about 60 years of cone production data for longleaf pine forests at four different sites were quantitatively characterized from different perspectives. Results indicated that longleaf pine was different from masting species and there was no general trend of increasing coefficient of variation (CV) in cone production through time. On a decade scale, there was a significantly positive correlation between the CV of cone production and CV of average annual air temperature, but the CV of annual precipitation was negatively correlated with the CV of cone production at the Escambia (AL) and Blackwater (FL) sites. Phase coupling of cone production with a strength of approximately 0.4 existed only between the Escambia and Blackwater sites and no significant phase coupling was found between other sites. The implications of these results for forest management are discussed from a perspective of spatial and temporal complexity.

The maintenance of old-growth stands is important for sustaining natural forest ecosystems, but fire disturbances and commonly-used timber harvest practices exert adverse impacts on the retention of old-growth forests. Forest management planning prescribes harvest levels based on the planning policy and models, but the impact of the management strategies on the retention of old-growth forests has not been well studied. The objectives of this study were to examine: a) the impact of implementing three different harvest policies on the retention of old-growth forest and b) the impact of implementing a policy of maintaining a targeted minimum of 20% old-growth area on the harvest revenue that would be generated over a long planning horizon. To simulate the implementation of these policies, we developed three strategic timber harvest-scheduling models. The first model (Model 1) maximizes harvest timber volume; Model 2 maximizes the net present value (NPV) of the timber harvested; and Model 3 maximizes the NPV of value-added products at the primary processing mills. The value-added products we considered were lumber, chips and sawdust. The models were solved for three forest management units with different fire regimes. Solutions to models that did not include a strict constraint on old-growth forest area retention did not retain the targeted level of old-growth forest over a 150-year planning horizon. When an old-growth constraint was implemented, Model 3 produced the greatest revenue with the least variation by 5-year period over the planning horizon. The probability of finding a feasible solution to our optimization Model 3 with an old-growth forest constraint increased to 0.87–1.0 compared with 0.71–0.83 using Model 1, and 0.78–0.87 using Model 2. We conclude that the value-added policy model increases the probability of sustaining the bioeconomy while preserving forest ecosystems initiated by disturbance.

Shelterwood is commonly assumed to be a more nature-friendly silvicultural system than clear-cutting. However, dead-wood pools – a key characteristic of natural forest – have been seldom compared between these systems. We investigated how shelterwood harvesting influences the dynamics of different dead-wood fractions in Estonia, where the predominant forestry model is clear-cutting based but ‘seminatural’ (using native tree species and, to a significant extent, natural regeneration). We measured dead-wood pools in 49 Scots pine-dominated stands (representing all shelterwood harvesting stages), and in 11 pine-dominated and 10 Norway spruce-dominated stands as before-after experiments (1st stage only). We analysed dead-wood amounts in relation to site conditions and the proportion of timber harvested, and we compared the shelterwood impacts with published estimates from Estonian clear-cuts. Fine woody debris (5–9.9 cm) increased with the harvest. The volume of coarse woody debris was 19–27 m3 ha−1 in uniform shelterwood stands in pine forest (0–25 years after the first harvest); 63 m3 ha−1 in strip shelterwood stands in spruce forest (immediately post harvest). In before-after experiments, post-harvest dead-wood amounts depended on fraction and harvesting intensity, which determines the balance between the input of new debris (logs; stumps) and the loss of pre-existing standing and downed dead trees. After the first shelterwood harvesting, dead-wood pools remained relatively stable, which contrasts with the large fluctuations after clear-cutting. In the long term, however, shelterwood did not sustain generally larger dead-wood pools than the clear-cutting system in seminatural forestry setting. The issue to be resolved in both types of regeneration cuttings is the near-complete loss of standing dead trees, which probably requires new harvesting techniques.

Forest site productivity, usually represented by site index (SI), is a fundamental resource variable in forest management planning as it is a quantitative measure of the production capacity of forest land. Site index is usually derived from estimates of dominant height (Hdom) at a given reference age using empirical age-height curves. However, it is commonly quantified with large uncertainty in forest management inventories, resulting in economic losses due to incorrect management decisions. In this study, we used bitemporal airborne laser scanner (ALS) data acquired for a study area in southeastern Norway with a time interval of 15 years to estimate SI by means of an area-based approach. We present two practical methods for SI determination, i.e., the (1) direct and (2) indirect method. With the direct method, we regressed field observations of age-height SI against canopy height metrics derived from ALS data from the first point in time and changes in ALS metrics reflecting canopy height growth during the observation period. With the indirect method, we first modelled Hdom for the two points in time using the respective ALS metrics as predictors. We then derived SI from the initial Hdom, the estimated Hdom increment, and the length of the observation period using empirical SI curves. We used bitemporal field data collected from 80 georeferenced sample plots of size 232.9 m2 to fit the species-specific regression models for SI and Hdom. We then applied the models to an independent dataset comprising 42 georeferenced validation plots of size ∼3700 m2, for which ground reference values were collected at both points in time, to assess the precision of both methods. Both the proposed methods produced SI estimates with satisfactory precision. For the direct method, the independent validation revealed root mean squared errors (RMSE) of 1.78 and 1.08 m for Norway spruce and Scots pine, respectively, compared to 1.82 m obtained for both tree species using the indirect method. The indirect method can provide a good alternative to the direct method as field observations of SI are not required to calibrate the regression models.

In this study we analysed a dataset of 8661 logs of silver fir (Abies alba Mill.) and Norway spruce (Picea abies L., Karst) in mixed fir-spruce-beech stands in primeval and natural forests in four sites separated into the two macroclimatic categories according to mean annual temperature (“cold” and “warmer”) and according to mean annual precipitation (“mesic” and “humid”). We used “Bayesian Survival Trajectory Analysis” on a more than 40-year long time series (1972–2015), focusing on differences in the residence time of deadwood in different macroclimatic categories and two DBH classes. We also evaluated two qualitative characteristics of the downed logs: mortality mode and log position during decomposition. We calculated residence time and the time needed to reach the advanced decay stage. Our analyses confirmed the influence temperature and precipitation on modelled residence time. The residence time for silver fir logs in the DBH class 55+ cm in the “cold” site was 106 years, while in the “warmer” sites was 78 years. The residence time in the “mesic” site was 57 years, while in the “humid” sites was 90 years. It took 81 years for Norway spruce logs in the DBH class 55+ cm to completely decompose in the “cold” site. Suspended logs 11 took years longer to decay than those in contact with the ground. The modelled residence time of logs on wet sites was the same as that of logs at sites unaffected by water. These results can be utilised in biodiversity oriented forest management, as well as in modelling future amounts of deadwood. In order to maintain the continuous presence of silver fir and Norway spruce deadwood for those organisms that depend on it, it is necessary to supply deadwood at least once every 25–40 years (depending on climatic category and DBH class). During this time, approximately 50% of logs become completely decomposed and 50% remain in the last decay stage.

Hurricanes are meteorological events with intense effects on coastal ecosystems where the change in wind kinetic energy is first concentrated. The quantification of forest change and the understanding of forest recovery trajectories after hurricane impact require a series of observations from before and after the event. Our objective was to quantify the immediate and delayed impacts of two successive large hurricanes, Jova (October 2011) and Patricia (October 2015) on the canopy structure and some ecosystem functions of the Chamela tropical dry forest on the Pacific coast of Mexico. This forest is not typically affected by large disturbance events, but has a background of extreme rainfall seasonality and corresponding phenological responses. We used a series of detailed historic and recent measurements of canopy structure and Photosynthetic Photon Flux Density (PPFD) coupled with a continuous series of remote sensing indices (NDVI) to help assemble a comprehensive view of the effects from hurricanes Jova and Patricia, category 2 and 4 in the Saffir-Simpson Hurricane Wind Scale, respectively. From ground-based LiDAR observations of canopy structure we estimated aboveground forest biomass at various times before and after the hurricanes. The net aboveground biomass loss from the two hurricanes combined (26.4 Mg ha−1) was about 33.7% of the pre-hurricane value of 78.4 Mg ha−1. Biomass loss from the first hurricane was about 8.6 Mg ha−1 (11.0% of the original). Damage from the second storm alone might have been as much as 22.7%, depending on the course of recovery between hurricanes. We also found a temporary decline in the fraction of Absorbed Photosynthetically Active Radiation (fAPAR). NDVI, well correlated to fAPAR, also showed this pattern after both hurricanes. Canopy structure was considerably altered by both hurricanes, including leaf area and persistent vertical and horizontal woody components. The effects of wind and precipitation differed in several ways: whereas biomass loss appears related to hurricane wind energy, the duration of extended greenness may be due to the extra aseasonal precipitation. Our data suggest that different aspects of ecosystem structure and function will recover at different time scales. The recovery of greenness occurs rapidly, on the order of weeks to months but canopy cover and production will recover more slowly. The re-establishment of persistent canopy structure and total biomass will likely take decades in the absence of other major disturbances or active forest management.

Finland has a long tradition of utilizing forest-based biomass for energy and industry purposes and the use has steadily increased in the past decade due to changes in international and regional energy policies. Intensive harvesting practices, in which a larger proportion of the woody biomass is removed from the forest stand, are becoming more common. The objectives of this study were (i) to evaluate the spatial and temporal extent of soil surface disturbance caused by stump-root system harvesting and (ii) to quantify how much biomass and nitrogen is removed from the stand in stump and coarse root harvesting. The extent of surface disturbance was assessed in three clear-cut Norway spruce ( Picea abies , (L . ) Karst.) stands in southern and central Finland, differing in time since harvest. To determine the biomass distribution of the stump-root system, stumps and coarse roots were excavated at one of the experimental stands. Across all age classes (time since harvest) less soil surface had remained undisturbed at the stump harvesting sites (52%) than at the sites where only mechanical site preparation (28%) had been carried out. Thus, the findings of this study indicate that soil disturbance caused by stump harvesting can exist on forest soil surface for more than a decade following harvest. The total biomass of the stump-root system in the stand was estimated to 39.3 Mg ha −1 and 79% of this biomass was removed during stump harvesting and consequently, 8.3 Mg ha −1 of stump-root biomass remained in soil. The stump-root system accounted for 17% of the whole-tree biomass, and coarse roots and fine coarse roots represented a significant portion of it (73%). Thus, the stump-root system represents a large biomass component in boreal forest stands. However, forest management utilizing stumps may result in carbon losses from the stand.

Recent trends in forest management promote the development of stands with a complex structure involving the use of partial cuts of various types. Partial cuts can increase the risk of wind damage but prior research on wind damage has largely focused on simple stand types and new modeling approaches are needed for these more complex stands. The present study looked at how the wind loading distribution in a naturally regenerated balsam fir (Abies balsamea (L.) Mill.) stand is modified by a local selective thinning. Two anemometers placed at canopy height and 2/3 canopy height, and strain gauges attached to the trunks of balsam fir trees allowed us to measure the wind-induced turning moments experienced by a sample of trees. A localized thinning was implemented around 2/3 of the sample trees in the second year of the experiment. Competing trees were removed within a 3.5 m radius of residual trees. Results show a dominant effect of the selective thinning at the tree scale but with an additional effect at the stand scale. The stand scale effect is likely linked to a change in wind profile within the canopy. A distance-independent competition index was useful in explaining the wind load distribution within the stand. Trees experiencing more competition were exposed to the largest increase of turning moment after the selective thinning. This study confirms the potential of competition indices for wind damage modeling in heterogeneous stands.

Remote sensing can provide useful explanatory variables for tree species distribution modeling, but only a few studies have explored this potential in Amazonia at local scales. Particularly for tropical forest management it would be useful to be able to predict the potential distribution of important tree taxa in areas where field data is as yet missing. Forest concessions produce valuable census data that cover large areas with high sampling effort and can be used as occurrence data in species distribution models (SDM). Nevertheless, these tree records are often spatially clumped and possibly only provide accurate predictions over areas close to where the training occurrence records are located. Here, we aim at investigating to what degree SDM performance and spatial predictions differ between models that have different spatial configurations of the occurrence data. For this, we divided the available occurrence data from a forest concession census in Peruvian Amazonia into different spatial configurations (narrow, elongated and compact), each of which contained approximately 20% of the full dataset. We then modelled the distributions of five tree taxa using Landsat data and elevation. More elongated configurations of the training data were more representative of the available environmental space, and also produced more robust SDMs. Average model performance (expressed as AUC) was 5% higher and variation in model performance 50% lower when elongated rather than compact configurations of training area were used. This confirms that covering only a small fraction of the environmental variability in the area of interest may lead to misleading SDM predictions, which needs to be taken into account when forest management decisions are based on SDMs.

Land use changes due to forestry activities can alter forest carbon (C) sequestration capacity by modifying vegetation structure and ecosystem functioning. The main objective of this study was to analyze aboveground net primary productivity (aNPP), through stem growth and litterfall production, and their feedback on soil C and nutrient contents, within a humid subtropical region. Two main forestry activities in NE Argentina were studied: selectively logged forests and Pinus taeda (loblolly pine) plantations for wood production. Well-preserved native forests were used as a control to compare the effects of interventions on the original subtropical forests. Despite differences in tree density and aboveground biomass among forests and pine plantation stands, the aNPP and total annual litterfall were similar across all ecosystems. However, litterfall quality and soil N content were substantially lower in pine plantations compared to both native forests. The labile soil C fractions were higher in pine plantations than native forests while no differences were observed in recalcitrant humic fractions across ecosystems. Overall, the results of this study suggest that man-made intervention in the structure of forest ecosystems does not necessarily result in degradation of aboveground ecosystem processes but had an impact on belowground processes and stocks in pine plantations, which has important implications for forest management.

A study was conducted on three species (Khaya senegalensis, Corymbia citriodora and Casuarina equisetifolia) planted in desert lands of Egypt and irrigated with basic treated municipal wastewater. Every single tree is permanently drip irrigated and at the same time fertilised by the nutrient-rich wastewater. Trees of different classes of the diameter at breast height (eight for each species) were felled to determine the form factor and stem volume, as well as the biomass and carbon sequestration of stem, crown and root of the individual trees. In addition, a scenario for the development of un-thinned stands from ages 5 to 35 years was constructed. The age of the sample trees at felling was: 128, 66 and 82 months for K. senegalensis, C. citriodora and C. equisetifolia, respectively. The vigorous sampled trees had a stem volume of 0.289, 0.162 and 0.229 m3 and an aboveground and belowground biomass of 451, 161 and 264 kg for K. senegalensis, C. citriodora and C. equisetifolia, respectively. Results of the scenario showed an unexpectedly high growth rate of afforestation in desert lands using municipal wastewater. At the age of 25, the stem volume for all three species exceeds 398 m3/ha. At the same age of 25 years, K. senegalensis, C. citriodora and C. equisetifolia sequester 1131, 1068 and 860 CO2 t/ha, respectively. Afforestation in desert areas presents a unique situation in forestry, as growth is stimulated by sufficient sunlight, water and nutrients. Competition for water and nutrients is strongly diminished. Self-thinning of stands under such conditions is expected to be much slower than in rain-fed plantation forests. On the other hand, tree maturity span is curtailed. This opens new possibilities for different forest management and practices towards resilient forest-based mitigation of climate change. For its unexpected role as an effective mitigation measure, afforestation in desert lands should be encouraged and further research conducted.

Since the industrial revolution, atmospheric nitrogen deposition has increased strongly and has been shown to alter nitrogen cycles, species composition and diversity in many ecosystems, including forests. At the same time, nitrogen removal from forests through biomass extraction via historical management techniques has decreased considerably. A proven tool to analyze the effects of long-term environmental changes are vegetation resurveys. In this study, we tested whether environmental changes resulting from atmospheric nitrogen deposition and altered forest management are reflected in the vegetation composition of temperate forest understories in six acidophilic and oligo-mesophilic forest types in south-western Germany. We compared historical surveys from 1950 to 1976 with surveys from 2017/18 and examined changes in the vegetation using NMDS ordinations and Ellenberg indicator values. While an increase in the number of nitrophilic species was detected in all forest types, only the acidophytic and oligotrophic Vaccinio-Abietetum and Luzulo-Quercetum forests (dominated by Abies alba (Mill.) and Quercus spec., respectively) exhibited a replacement of oligotrophic species by nitrophilic species, amounting to an overall trend of eutrophication. Despite the uncertainties resulting from different plot locations and the slow dynamics of forests, we demonstrate a significant trend in the understory vegetation composition, which is likely caused by atmospheric N deposition. Differences in the sensitivity of different forest types indicate an influence of geological and climatic site characteristics and historical land use on the effects of environmental changes.

Global trends in the demand for forest products, decreasing total area of actively managed forests, and pressures to increase profit margins suggest that forest management intensity will continue to increase in the future. These trends have typically led to shorter rotation lengths and increased utilization of forest biomass to supply the bio-economy with feedstocks for energy, novel bio-chemicals, traditional pulp and paper, panels and solid forest products. The combined influence of increased utilization and shortened rotation lengths have raised concerns regarding potential soil nutrient depletion and corresponding reductions in site productivity. In response to these concerns, the Weymouth Point Study Area (WPSA) in north-central Maine was established in a spruce-fir forest in 1979 to quantify the effects of whole-tree harvesting (WTH) and stem-only harvesting (SOH) on nutrient cycling and site productivity in adjacent, paired watersheds with large fixed-area plots. From 1979 to 2016, 49 permanent sample plots were established across three soil drainage classes to evaluate tree- and stand-level growth and nutrition response to harvest residue management and silviculture practices. Harvest treatments were implemented in 1981 with SOH simulated by returning delimbing residues after WTH, including chipped tops, branches and foliage (CHP), and lopped-and-scattered residues (LOP). The harvested watershed was aerially treated with triclopyr herbicide in the fourth growing season following WTH to release naturally regenerated conifers from herbaceous and woody weed competition. Response to silviculture practices were evaluated following pre-commercial thinning (PCT) and the addition of ammonium-nitrate fertilizer (FERT) treatments initiated 10 and 12 years following WTH, respectively. Thirty-five years post-harvest, tree growth and nutrient uptake have not been significantly affected by WTH at this location. Mean tree size was positively influenced by PCT; however, FERT did not significantly affect mean tree size. There were also no significant effects of treatments on aboveground biomass production and net nutrient uptake in trees. These results suggest that WTH at final felling for bio-economy feedstock production in spruce-fir forests similar to those at the WPSA (Chesuncook catena soils) is sustainable. However, this hypothesis is based on mid-rotation assessment of tree growth as an indicator of sustainable forest management. Further research is required to confirm the absence of negative impacts on tree- and stand-level growth and nutrition through the end of the current rotation.

Environmental and economic performance of forestry on drained peatlands was reviewed to consider whether continuous cover forestry (CCF) could be a feasible alternative to even-aged management (EM). CCF was regarded feasible particularly because continuously maintaining a tree stand with significant transpiration and interception capacity would decrease the need for ditch network maintenance. Managing CCF forests in such a way that the ground water levels are lower than in clear-cut EM forests but higher than in mature EM forests could decrease greenhouse gas emissions and negative water quality impacts caused both by anoxic redox reactions and oxidation and mineralization of deep peat layers. Regeneration studies indicated potential for satisfactory natural regeneration under CCF on drained peatlands. An economic advantage in CCF over EM is that fewer investments are needed to establish the forest stand and sustain its growth. Thus, even if the growth of trees in CCF forests were lower than in EM forests, CCF could at least in some peatland sites turn out to be a more profitable forest management regime. An advantage of CCF from the viewpoint of socially optimal forest management is that it plausibly reduces the negative externalities of management compared to EM. We propose that future research in drained peatland forests should focus on assessing the economic and environmental feasibility of CCF.

This study compared 141 ecologically relevant climate metrics to field assessments of sugar maple (Acer saccharum Marsh.) canopy condition across Vermont, USA from 1988 to 2012. After removing the influence of disturbance events during this time period to isolate the impact of climate, we identified five climate metrics that were significantly related to sugar maple crown condition. While three of these are monthly summary metrics commonly used in climate analyses (minimum April, August and October temperatures), two are novel metrics designed to capture extreme climate events (periods of unusual warmth in January and August). The proportion of climate-driven variability in canopy condition is comparable to the proportion accounted for by defoliating pests and other disturbance events. This indicates that climate conditions, though rarely included in sugar maple decline studies, may be of equal importance as more traditionally studied stress agents. Modeled across the state, results indicate that changes in historical climatic conditions have negatively impacted sugar maple health over the 25 year study period, and are likely to degrade further over time. Climate projections under a low emissions scenario indicated that by 2071 55% of sugar maple across the state would likely experience moderate to severe climate-driven stress relative to historic baselines, increasing to 84% under a high emissions scenario. However, geographic variability in projected climate impacts indicates that while conditions for sugar maple will likely deteriorate across the state, climate refugia should also be available to maintain sugar maple in spite of changing climatic conditions. Considering the predominant role of sugar maple in Vermont’s economy and culture, managing this resource into the future could pose a considerable challenge.

Mixed forest plantations now emerge as an alternative to traditional plantations in the tropics and represent ecological gains associated with production, wood quality and nutrient cycling. Mixed plantations with higher diversity may also be advantageous concerning their use of soil water. To shed light onto water-related issues of mixing Eucalyptus and a high diversity of tropical native trees, we explored the following questions: What is the impact of high diversity mixed plantations of Eucalyptus intercropped with native trees on soil water? How does the mixture affect the physiology of water use in native trees? Firstly, we tested the hypothesis that stands of Eucalyptus mixed with a high diversity of native trees consume less water compared to Eucalyptus monocultures, by measuring the temporal dynamics of soil water. Secondly, we tested how mixing with Eucalyptus affects the hydraulic performance of fast- and slow-growing native species in these forestry systems. This is the first time a large experiment has been implemented to compare the effects of monospecific Eucalyptus plantations, native species mixtures and mixed plantations of Eucalyptus and native species on soil water dynamics under controlled conditions in terms of site, age, soil type, topography and climate. We found that high diversity mixed plantations of Eucalyptus and native trees use less soil water, than Eucalyptus monocultures. However, the soil under the mixtures was drier than in native species stands. The mixing with Eucalyptus affected the hydraulic performance of native species by decreasing the leaf water potential and stomatal conductance of the fast-growing species, suggesting that fast-growing species performance may be especially constrained by competition for water from Eucalyptus. These findings have important implications for forest management and ecological restoration in the tropics. They will help to further develop silvicultural options to adapt to climate change and improve plantation forestry by using mixed plantations for production purposes or rehabilitation of degraded lands.

In tropical forests, selective logging generates a significant reduction of above-ground carbon stocks, due to direct removal of a few large merchantable individuals, and the death of smaller injured or smashed trees following harvesting. Several studies have shown a strong correlation between logging intensity and a reduction of biodiversity, wood production, and biomass stocks. However, little is known about the long-term effects of logging on the main forest carbon (C) stocks in above and below-ground tree biomass, deadwood, litter, and soil. In this study we quantified C stocks in 28 0.25-ha plots located in a mixed Dipterocarp forest, Borneo, Indonesia, logged 16 years ago at different intensities ranging from 0 to 57% of initial biomass removed. We investigated the effect of logging intensity, topography, and soil variables on each C stock using linear mixed models. Sixteen years after logging, total C stocks ranged from 218 to 554 Mg C ha−1 with an average of 314 ± 21 Mg C ha−1, of which more than 75% were found in live trees. Logging intensity was found to be the main factor explaining the variability in carbon stored in above- and below- ground biomass of tree DBH >20 cm and deadwood. Simultaneously, the proportion of deadwood increased with logging intensity reaching 13.5% of total C stocks in intensively logged plots (>20% removal of initial biomass). This study confirmed, therefore, the need to limit logging intensity to a threshold of 20% of initial biomass removal in order to limit the long-term accumulation of deadwood after logging, probably due to high post-logging mortality. With more than half of all Bornean forests already logged, accounting for total C post-logging is key to better assess the long-term carbon footprint of commercial logging in the region, and is a necessary step towards the development of C-oriented forest management in the tropics.

Contemporary forest management requires highly-detailed, spatially-contiguous, multi-temporal, and scenarios-comparable forest conditions. Field inventories and individual-tree models often contain highly-detailed data and allow for long-term complex scenarios comparison, but the information is only at sampled locations and lacks complete spatial coverage. Forest landscape models (FLMs) provide landscape-level spatiotemporal data, but the details that are important to land managers are often lost in the generalized outputs. We developed a modeling framework, F3, to integrate FIA (Forest Inventory and Analysis) plots, the Forest Vegetation Simulator (FVS), and FastEmap (Field And SatelliTe for Ecosystem MAPping) to simulate spatiotemporal forest change under natural succession and vegetation management. F3 extrapolates the details of forest inventory plots and individual-tree model outputs to a spatially-contiguous landscape by fusing tree-list field measurements, individual tree growth and yield models, remote sensing and environmental geospatial datasets. F3 allows for area-specific management action simulations. F3 compares FVS results with field measurements for temporal accuracy assessment and uses a leave-one-out cross-validation for spatial accuracy assessment. F3 adopts parallel computation techniques to implement the modeling in an automatic and efficient manner. The proof of concept of F3 was demonstrated in Tahoe National Forest (TNF) showing spatiotemporal changes on six forest structural metrics (quadratic mean diameter, basal area, biomass, habitat suitability index, canopy cover, and coarse woody debris) under natural succession, regeneration-cut, and thinning scenarios for the years 2014–2114 at a 30 m resolution. F3 can be used for initializing FLMs and for analyzing a wide range of ecosystem services; however, the under-representation of certain forest types in the FIA plot data set, the modeling bias from FVS, and choice of FastEmap covariates contribute to major uncertainties in the framework.

The practice of fire suppression across the western United States over the past century has led to dense forests, and when coupled with drought has contributed to an increase in large and destructive wildfires. Forest management efforts aimed at reducing flammable fuels through various fuel treatments can help to restore frequent fire regimes and increase forest resilience. Our research examines how different fuel treatments influenced burn severity and post-fire vegetative stand dynamics on the San Carlos Apache Reservation, in east-central Arizona, U.S.A. Our methods included the use of multitemporal remote sensing data and cloud computing to evaluate burn severity and post-fire vegetation conditions as well as statistical analyses. We investigated how forest thinning, commercial harvesting, prescribed burning, and resource benefit burning (managed wildfire) related to satellite measured burn severity (the difference Normalized Burn Ratio – dNBR) following the 2013 Creek Fire and used spectral measures of post-fire stand dynamics to track changes in land surface characteristics (i.e., brightness, greenness and wetness). We found strong negative relationships between dNBR and post-fire greenness and wetness, and a positive non-linear relationship between dNBR and brightness, with greater variability at higher severities. Fire severity and post-fire surface changes also differed by treatment type. Our results showed harvested and thinned sites that were not treated with prescribed fire had the highest severity fire. When harvesting was followed by a prescribed burn, the sites experienced lower burn severity and reduced post-fire changes in vegetation greenness and wetness. Areas that had previously experienced resource benefit burns had the lowest burn severities and the highest post-fire greenness measurements compared to all other treatments, except for where the prescribed burn had occurred. These results suggest that fire treatments may be most effective at reducing the probability of hazardous fire and increasing post-fire recovery. This research demonstrates the utility of remote sensing and spatial data to inform forest management, and how various fuel treatments can influence burn severity and post-fire vegetation response within ponderosa pine forests across the southwestern U.S.

Gap dynamics is the main process by which forest renewal happens in many forest biomes in the world. Under the classical gap dynamics model, only canopy gaps are considered as a dynamic zone. It is also assumed that gapless canopy height change is either uncommon or unimportant for forest dynamics, even though its frequency has never been quantified. In the temperate deciduous forest biome of Quebec, Canada, forest management uses selection cutting to emulate gap dynamics, but little is known about the differences in canopy dynamics between unmanaged and managed forests. Here, we investigated five canopy height change processes: three generating positive height change (canopy growth, gap closure and gap filling) and two generating negative height change (gap creation and canopy height erosion) using multi-temporal LiDAR data in unmanaged and managed (by partial cutting) forests at different periods during the last 24 years. Canopy height erosion, which is canopy height reduction without gap formation, was very common in all studied forests, whatever the gap detection height thresholds used. This canopy process was often more frequent than new canopy gaps and as important in terms of canopy volume reduction. Gap closure rates suggest that canopy gaps will remain more frequent in managed forests 30 years after cuts compared to unmanaged forests. Our results show that it will take at least 30 years after cuts for natural canopy dynamics to recover. We also show that measurements of canopy dynamics processes are sensitive to canopy gap detection height thresholds. This sensitivity is clearly limiting the reproducibility and the comparability of studies in gap ecology.

In many Central European areas, forests have been altered by century-long management practices, including grazing with domestic ungulates and litter harvesting. During the last century, most of these agro-forestry practices have been abandoned in many regions of Switzerland. As a consequence, stand density has increased, leading to higher competition for resources among trees, and particularly between overstory trees and understory vegetation. Only few studies investigated the effects of understory on the growth and physiology of overstory trees. We conducted an understory removal experiment at a xeric Scots pine (Pinus sylvestris L.) forest in an inner-Alpine valley of Switzerland over a period of 5 years and compared data of soil temperature and water content, needle and shoot length, and radial growth and sap flow. The removal of the understory increased soil temperature as well as soil water content at 5 to 60 cm soil depth, and led to a 4.6-fold higher mean annual radial growth and significantly longer needles and shoots. The removal of the understory further decreased tree water deficit and increased sap flow. We conclude that reduced competition for soil water after removal of the understory vegetation was the primary cause of the increased performance of the overstory trees since light was not a limiting factor already before the understory removal. Thus, increases in understory density due to altered forest management may have exacerbated observed drought-induced decline processes. Therefore, our study demonstrates the need for a careful disentangling of climate and land-use change processes as they may evolve in parallel and potentially intensify their impact on the ecosystems. In contrast, the findings suggest decreasing understory density as a suitable management practice to increase overstory tree growth and vigour, and hence reduce mortality risk for a species like Scots pine in a drought-prone environment.

Moso bamboo (Phyllostachys pubescens) is widely distributed in subtropical China and plays an important role in terrestrial carbon cycling. However, the capacity of Moso bamboo forests to sequester carbon and their long-term structural development in large regions remain poorly quantified. We used the national forest continuous inventory data to measure and quantify the carbon stock and structure change from 2004 to 2014. The results of kernel density estimation showed that the culm density and average DBH (diameter at breast height) of Moso bamboo forests had a tendency to increase in Zhejiang Province. However, the culm structure of the Moso bamboo forests in Zhejiang Province was not optimal for high bamboo productivity. The aboveground culm carbon stock increased from 2004 to 2014, indicating that the Moso bamboo forests acted as a carbon sink. The average change in the aboveground carbon stock over the study period was 0.94 Mg C ha−1 yr−1, smaller than the corresponding value for different forest types in the same region and for the Moso bamboo forests managed by farmers in the lower mountain areas of central Taiwan (8.13 Mg C ha−1 yr−1), indicating that Moso bamboo forests have a large carbon sequestration potential. Furthermore, age classes 2–4 contributed positively to changes in the total aboveground culm carbon stock by 23.07%, 36.35%, and 50.17%, respectively. The change in the carbon stock was not correlated with any environmental factors, but the carbon stock increased with increasing culm density, average DBH (diameter at breast height), and culm age. Our results suggest that the Moso bamboo forests of Zhejiang Province have a large carbon sequestration potential if the structure and management strategies of the forests are optimized. This study improves our understanding of the carbon dynamics and structural development in Moso bamboo forests, which could help guide the future forest management strategies.