Scenario analysis of the impacts of forest management and climate change on the European forest sector carbon budget

Analysis of the impacts of forest management and climate change on the European forest sector carbon budget between 1990 and 2050 are presented in this article. Forest inventory based carbon budgeting with large scale scenario modelling was used. Altogether 27 countries and 128.5 million hectare of forests are included in the analysis. Two forest management and climate scenarios were applied. In Business as Usual (BaU) scenario national fellings remained at the 1990 level while in Multifunctional (MultiF) scenario fellings increased 0.5–1% per year until 2020, 4 million hectare afforestation program took place between 1990 and 2020 and forest management paid more attention to current trends towards more nature oriented management. Mean annual temperature increased 2.5 °C and annual precipitation 5–15% between 1990 and 2050 in changing climate scenario. Total amount of carbon in 1990 was 12 869 Tg, of which 94% in tree biomass and forest soil, and 6% in wood products in use. In 1995–2000, when BaU scenario was applied under current climatic conditions, net primary production was 409 Tg C year⁻¹, net ecosystem production 164 Tg C year⁻¹, net biome production 84.5 Tg C year⁻¹, and net sequestration of the whole system 87.4 Tg C year⁻¹ which was equal to 7–8% of carbon emissions from fossil fuel combustion in 1990. Carbon stocks in tree biomass, soil and wood products increased in all applied management and climate scenarios, but slower after 2010–2020 than that before. This was due to ageing of forests and higher carbon densities per unit of forest land. Differences in carbon sequestration were very small between applied management scenarios, implying that forest management should be changed more than in this study if aim is to influence carbon sequestration. Applied climate scenarios increased carbon stocks and net carbon sequestration compared to current climatic conditions.     

A novel approach to optimize management strategies for carbon stored in both forests and wood products

We present a new approach to maximize carbon (C) storage in both forest and wood products using optimization within a forest management model (Remsoft Spatial Planning System). This method was used to evaluate four alternative objective functions, to maximize: (a) volume harvested, (b) wood product C storage, (c) forest C storage, and (d) C storage in the forest and products, over 300 years for a 30,000 ha hypothetical forest in New Brunswick, Canada. Effects of three initial forest age-structures and a range of product substitution rates were tested. Results showed that in many cases, C storage in product pools (especially in landfills) plus on-site forest C was equivalent to forest C storage resulting from reduced harvest. In other words, accounting for only forest, and not products and landfill C, underestimates true forest contributions to C sequestration, and may result in spurious C maximization strategies. The scenario to maximize harvest resulted in mean harvest for years 1–200 of 3.16 m³ ha⁻¹ yr⁻¹ and total C sequestration of 0.126 t ha⁻¹ yr⁻¹, versus 0.98 m³ ha⁻¹ yr⁻¹ and 0.228 t ha⁻¹ yr⁻¹ for a scenario to maximize forest C. When maximizing total (forest + products) C, mean harvest and total C storage for years 1–200 was 173% and 5% higher, respectively, than when maximizing forest C; and 218% and 6% higher, respectively, when maximizing substitution benefits (0.25 t of avoided C emissions per m³ of lumber used) in addition to total C. Initial forest age-structure affected harvest in years 1–50 < 34% among the four alternative management objective scenarios, and resulted in mean C sequestration rates of 0.31, 0.10, and −0.14 t ha⁻¹ yr⁻¹ when maximizing total C storage for young, even-aged, and old forests, respectively. Our results reinforce the importance of including products in forest-sector C budgets, and demonstrate how including product C in management can maximize forest contributions toward reduced atmospheric CO₂ at operational scales.     

Changes in forest structure of a mixed conifer forest, southwestern Colorado, USA

We selected a warm/dry mixed conifer forest (ponderosa pine, white fir, Douglas-fir, and aspen) in southwestern Colorado to reconstruct historical conditions of fire regime and forest structure in preparation for an experiment in ecological restoration. Although mixed conifer forests are of high ecological and social value in the Southwest, they have been less studied than ponderosa pine forests. Fire-scar analysis on a 150-ha area showed recurring fires at mean intervals of 24 years (all fires with minimum of 2 sample trees scarred) to 32 years (fire scarring 25% or more of sample trees) from the 16th century until the abrupt cessation of fire after 1868, concurrent with European settlement. There was no evidence in age or species-specific data of severe burning at the scale of the study blocks (approximately 200 ha). The forest remained unharvested throughout most of the 20th century, until a cut in the early 1990s removed approximately equal basal areas of ponderosa pine and white fir. Forest structure had already changed substantially, however. Total basal area increased from an average of 11 m² ha⁻¹ in 1870 to 27 m² ha⁻¹ in 2003, despite harvesting of at least 8.4 m² ha⁻¹. Ponderosa pine declined from representing nearly two-thirds of basal area in 1870 to one-third in 2003. The other species increased dramatically, especially white fir, which went from 12% to 35% of basal area and dominated stand density with an average of 392 trees ha⁻¹. Total tree density increased from 142 trees ha⁻¹ in 1870 to 677 trees ha⁻¹ in 2003. The ecological changes that occurred here since the 19th century have been in exactly the opposite direction considering the warm, fire-favoring climate expected in the 21st century. If warm/dry mixed conifer forests of southern Colorado are to have a reasonable chance for persistence under the future climate regime, restoring conditions more similar to the frequently burned, open forests of the past is likely to be a useful starting point.     

Uncertainty of 21st century growing stocks and GHG balance of forests in British Columbia, Canada resulting from potential climate change impacts on ecosystem processes

Over the coming decades, climate change will increasingly affect forest ecosystem processes, but the future magnitude and direction of these responses is uncertain. We designed 12 scenarios combining possible changes in tree growth rates, decay rates, and area burned by wildfire with forecasts of future harvest to quantify the uncertainty of future (2010-2080), timber growing stock, ecosystem C stock, and greenhouse gas (GHG) balance for 67 million ha of forest in British Columbia, Canada. Each scenario was simulated 100 times with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). Depending on the scenario, timber growing stock over the entire land-base may increase by 14% or decrease by 9% by 2080 (a range of 2.8 billion m³), relative to 2010. However, timber growing stock available for harvest was forecast to decline in all scenarios by 26-62% relative to 2010 (a range of 1.2 billion m³). Forests were an annual GHG source in 2010 due to an ongoing insect outbreak. If half of the C in harvested wood was assumed to be immediately emitted, then 0-95% of simulations returned to annual net sinks by 2040, depending on scenario, and the cumulative (2010-2080) GHG balance ranged from a sink of −4.5 Pg CO₂e (−67 Mg CO₂e ha⁻¹) for the most optimistic scenario, to a source of 4.5 Pg CO₂e (67 Mg CO₂e ha⁻¹) for the most pessimistic. The difference in total ecosystem carbon stocks between the most optimistic and pessimistic scenarios in 2080 was 2.4 Pg C (36 Mg C ha⁻¹), an average difference of 126 Tg CO₂e yr⁻¹ (2 Mg CO₂e yr⁻¹ ha⁻¹) over the 70-year simulation period, approximately double the total reported anthropogenic GHG emissions in British Columbia in 2008. Forests risk having reduced growing stock and being GHG sources under many foreseeable scenarios, thus providing further feedback to climate change. These results indicate the need for continued monitoring of forest responses to climatic and global change, the development of mitigation and adaptation strategies by forest managers, and global efforts to minimize climate change impacts on forests.     

Do restoration fellings in protected forests increase the risk of bark beetle damages in adjacent forests? A case study from Fennoscandian boreal forest

Gap fellings are used to promote multi-cohort structures and to restore other natural forest structures and processes in protected areas that have been altered by anthropogenic activities. Gaps and felled trees may also provide breeding material for species that in high numbers can cause significant tree mortality, growth reduction and consequent economic losses in surrounding production forests. In this study, the effect of restoration gap fellings on feeding intensity of Tomicus spp. (pine shoot beetles) was evaluated by counting fallen pine shoots at different distances from gaps in a protected area in eastern Finland. Gap fellings had a clear effect on the feeding intensity of the beetles. The average density of fallen shoots m⁻² was 17 within a 10-m distance from gaps but decreased rapidly to around 4 at the distance of 50 m and beyond. The distance decay in shoot feeding is described well by the negative exponential models. Our results suggest that gap fellings have only a localized effect on shoot feeding by Tomicus in the forests surrounding the restoration gaps. In practical restoration, a buffer zone of 100–200 m around the gap fellings, as implemented here, is enough to minimize economically significant growth reduction in surrounding production forests. As shown in this study, restoration of natural forest structures and dynamics to protect biodiversity is not necessarily in conflict with forest hygiene objectives in production forests.     

Deadwood in New Zealand's indigenous forests

We present the results of a systematic, unbiased national survey of deadwood volume and biomass in New Zealand's remaining indigenous forests based on an 8-km grid of 894 permanent plots. New Zealand's old growth evergreen temperate forests are largely comprised of long-lived, slow-growing tree species typically growing in cool, humid conditions; collectively these conditions are thought to promote accumulation of high deadwood stocks. We estimated deadwood biomass and volume in New Zealand's forests and compared these stocks with published values from other broadleaved evergreen temperate forests. Mean deadwood biomass in New Zealand was 54 Mg ha⁻¹ but ranged across plots from 0 to 550 Mg ha⁻¹. Mean deadwood volume was 158 m³ ha⁻¹ and ranged across plots from 0 to 1890 m³ ha⁻¹. Fallen logs accounted for 63% of total deadwood volume and 65% of total deadwood biomass, with standing dead trees being the remainder. Each piece of deadwood was classified into one of three broad decay classes and >40% of deadwood was fallen logs of the intermediate decay class. Deadwood biomass and volume varied 1.8- and 1.9-fold, respectively, among forest types and was greatest in broadleaved forests, dominated by Weinmannia racemosa (Cunoniaceae), Metrosideros umbellata (Myrtaceae) and Metrosideros robusta, and broadleaf-Nothofagus (Nothofagaceae) forests supporting the large tree species Nothofagus fusca. Deadwood biomass and volume were least in broadleaf-conifer admixtures. We used structural equation models to determine whether deadwood biomass could be predicted from climate and environment (vapor pressure deficit, elevation and slope), live tree biomass, forest composition (captured by two ordination axes), wood density of live trees, and tree size (a proxy for stand age). The model that best fit the data retained only vapor pressure deficit, live tree biomass and the first ordination axis as predictors of deadwood biomass. However, this model predicted just 2.4% of the variation in deadwood biomass, suggesting that additional factors not captured by this dataset, such as disturbance dynamics, may control deadwood abundance. Comparisons with other temperate and tropical forests did not support the hypothesis that New Zealand's cool temperate rainforests support higher than expected biomass or volume of deadwood.     

Timber mobilization and habitat tree retention in low-elevation mixed forests in Switzerland: an inventory-based scenario analysis of opportunities and constraints

Timber use in central Europe is expected to increase in the future, in line with forest policy goals to strengthen local wood supply for CO₂-neutral energy production, construction and other uses. Growing stocks in low-elevation forests in Switzerland are currently high as exemplified by the Swiss canton of Aargau, for which an average volume of 346 ± 16 m³ ha⁻¹ was measured in the 3rd Swiss National forest inventory (NFI) in 2004–2006. While this may justify a reduction of growing stocks through increased timber harvesting, we asked whether such a strategy may conflict with the sustainability of timber production and conservation goals. We evaluated a range of operationally relevant forest management scenarios that varied with respect to rotation length, growing stock targets and the promotion of conifers in the regeneration. The scenarios aimed at increased production of softwood, energy wood, the retention of potential habitat trees (PHTs) and the conversion to a continuous cover management system. They were used to drive the inventory-based forest simulator MASSIMO for 100 years starting in 2007 using the NFI sampling plots in Aargau. We analyzed model outputs with respect to projected future growing stock, growth, timber and energy yield and harvesting costs. We found growing stock to drop to 192 m³ ha⁻¹ in 2106 if business-as-usual (BAU as observed between the 2nd and 3rd NFI) timber volumes were set as harvesting targets for the whole simulation period. The promotion of conifers and a reduction of rotation lengths in a softwood scenario yielded 25% more timber over the whole simulation period than BAU. An energy wood scenario that reduced growing stock to 200 m³ ha⁻¹ by 2056 and promoted the natural broadleaved regeneration yielded 9% more timber than BAU before 2056 and 30% less thereafter due to decreasing increments. The softwood scenario resulted in higher energy yield than the energy wood scenario despite the lower energy content of softwood. Retaining PHT resulted in a reduction of timber harvest (0.055 m³ ha⁻¹ yr⁻¹ per habitat tree) and higher harvesting costs. Continuous cover management yielded moderate timber amounts throughout the simulation period, yet sustainably. Considering climate change, we discuss the risks associated with favoring drought- and disturbance-susceptible conifers at low elevations and emphasize that continuous cover management must allow for the regeneration of drought-adapted tree species. In conclusion, our simulations show potential for short-term increases in timber mobilization but also that such increases need to be carefully balanced with future forest productivity and other forest ecosystem services.

     

EU-wide maps of growing stock and above-ground biomass in forests based on remote sensing and field measurements

The overall objective of this study was to combine national forest inventory data and remotely sensed data to produce pan-European maps on growing stock and above-ground woody biomass for the two species groups “broadleaves” and “conifers”. An automatic up-scaling approach making use of satellite remote sensing data and field measurement data was applied for EU-wide mapping of growing stock and above-ground biomass in forests. The approach is based on sampling and allows the direct combination of data with different measurement units such as forest inventory plot data and satellite remote sensing data. For the classification, data from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used. Comprehensive field measurement data from national forest inventories for 98,979 locations from 16 countries were used for which tree species and growing stock estimates were available. The classification results were evaluated by comparison with regional estimates derived independently from the classification from national forest inventories. The validation at the regional level shows a high correlation between the classification results and the field based estimates with correlation coefficient r = 0.96 for coniferous, r = 0.94 for broadleaved and r = 0.97 for total growing stock per hectare. The mean absolute error of the estimations is 25 m³/ha for coniferous, 20 m³/ha for broadleaved and 25 m³/ha for total growing stock per hectare. Biomass conversion and expansion factors were applied to convert the growing stock classification results to carbon stock in above-ground biomass. As results of the classification, coniferous and broadleaved growing stock as well as carbon stock of the above-ground biomass is mapped on a wall-to-wall basis with a spatial resolution of 500 m × 500 m per grid cell. The mapped area is 5 million km², of which 2 million km² are forests, and covers the whole European Union, the EFTA countries, the Balkans, Belarus, the Ukraine, Moldova, Armenia, Azerbaijan, Georgia and Turkey.     

A review of habitat thresholds for dead wood: a baseline for management recommendations in European forests

In contemporary forest management, also of commercial forests, threshold values are widely used for consideration of biodiversity conservation. Here, we present various aspects of dead-wood threshold values. We review published and unpublished dead-wood threshold data from European lowland beech–oak, mixed-montane, and boreo-alpine spruce–pine forests separately to provide managers of European forests with a baseline for management decisions for their specific forest type. Our review of dead-wood threshold data from European forests revealed 36 critical values with ranges of 10–80 m³ ha⁻¹ for boreal and lowland forests and 10–150 m³ ha⁻¹ for mixed-montane forests, with peak values at 20–30 m³ ha⁻¹ for boreal coniferous forests, 30–40 m³ ha⁻¹ for mixed-montane forests, and 30–50 m³ ha⁻¹ for lowland oak–beech forests. We then expand the focus of dead-wood threshold analyses to community composition. We exemplify the two major statistical methods applied in ecological threshold analysis to stimulate forest researchers to analyze more of their own data with a focus on thresholds. Finally, we discuss further directions of dead-wood threshold analysis. We anticipate that further investigations of threshold values will provide a more comprehensive picture of critical ranges for dead wood, which is urgently needed for an ecological and sustainable forestry.     

Evaluation of forest disturbance in south-west Zabaikalia （East Siberia）Evaluation of forest disturbance in south-west Zabaikalia （East Siberia）Evaluation of forest disturbance in south-west Zabaikalia （East Siberia）

The forest estate in south-west Zabaikalia, a territory included in the Lake Baikal catchment area, has been investigated. For this purpose we have used both data of our own studies and monitoring data of environmental protection bodies. It shows that in our study area, fires, fellings, entomo-parasites and air pollution are the major negative factors affecting the state of the forest. In the period from 2003 to 2008 fires were registered in the area of over 500 thousand ha, pest foci in the forests covering an area of over 330 thousand ha, where almost 5 million m3 wood was cut in an area of about 43 thousand ha. The total area of forests in our study affected by air pollution amounts to about 700 thousand ha. According to the results, forest pollution in the territory is concentrated in the vicinity of large-scale industrial complexes, for distances up to about 40 km. The total area of forests weakened by air pollution amounts to about 2 million ha.     

The realisable potential supply of woody biomass from forests in the European Union

Forests are important for providing wood for products and energy and the demand for wood is expected to increase. Our aim was to estimate the potential supply of woody biomass for all uses from the forests in the European Union (EU), while considering multiple environmental, technical and social constraints.The potential woody biomass supply was estimated for the period 2010-2030 for stemwood, residues (branches and harvest losses), stumps and other biomass (woody biomass from early thinnings in young forests). We estimated the theoretical biomass potential from recent, detailed forest inventory data using the EFISCEN model. Constraints reducing the availability of woody biomass were defined and quantified for three mobilisation scenarios (high, medium, low). Finally, the theoretical potentials from EFISCEN were combined with the constraints to assess the realisable potential from EU forests.The realisable potential from stemwood, residues, stumps and other biomass was estimated at 744 million m³ yr⁻¹ overbark in 2010 and could range from 623 to 895 million m³ yr⁻¹ overbark in 2030, depending on the mobilisation scenario. These potentials represented 50-71% of the theoretical potential. Constraints thus significantly reduced the biomass potentials that could be mobilised. Soil productivity appeared to be an important environmental factor when considering the increased use of biomass from forests. Also the attitude of private forest owners towards increased use of forest biomass can have an important effect, although quantifying this is still rather difficult.The analysis showed that it is possible to increase the availability of forest biomass significantly beyond the current level of resource utilisation. Implementing these ambitious scenarios would imply quite drastic changes in forest resource management across Europe.     

Growing stock variation in different teak （Tectona grandis） forest stands of Mizoram,India

The growing stock assessment of three different teak forest stands （Tuirial： 500 m asl, Sairang： 200 m asl and Phunchawng： 550 m asl） was done in 2006 in Mizoram, India. Five diameter classes were arbitrarily established for knowing the volume attribute data and population structure, viz. a （10-20 cm）, b （20-30 cm）, c （30-40 cm）, d （40-50 cm）, and e （50-60 cm）. Results revealed that the density of the individuals among the studied stands varied from 280 stems/ha to 620 stems/ha. The average diameter of all the individuals ranged between 27.48 cm and 35.43 cm. Similarly, the average height was oscillated between 17.87 m and 22.24 m. The total basal area was recorded between 24.28 m2.ha-1 and 45.80 m2.ha＂l. The maximum and minimum values of total growing stock under all the diameter classes were 669.01 m3.ha-1 and 284.7 m3.ha-1, respectively. The representation of population structure of different stands explained that the perpetuation of this species was ensured for a quite long time.     

Estimating forest data for analyses of forest production and utilization possibilities at local level by means of multi-source National Forest Inventory

The sample plot data of National Forest Inventories (NFI) are widely used in the analysis of forest production and utilization possibilities to support national and regional forest policy. However, there is an increasing interest for similar impact and scenario analyses for strategic planning at the local level. As the fairly sparse network of field plots only provides calculations for large areas, satellite image data have been applied to produce forest information for smaller areas. The aim of this study was to test the feasibility of generating forest data for a Finnish forest analysis tool, the MELA system, by means of the Landsat satellite imagery and the NFI sample plot data. The study was part of the preparation of a local forestry programme, where a strategic scenario analysis for the forest area of two villages (ca 8000 ha) was carried out. Management units that approximate forest stands were delineated by image segmentation. Stand volume and other parameters for each forest segment were estimated from weighted means of the NFI sample plots, where the individual sample plot weights were estimated by the k nearest neighbour (kNN) method. Two different spectral features were tested: single pixel values and average pixel values within a segment. The estimated forest data were compared with the forest data based on independent stand-level field assessments in two subareas, a national park and an area of forest managed for timber production.In the national park, the estimated mean volume of the growing stock from both spectral feature sets (about 160 m³ ha⁻¹) was clearly lower than that obtained from stand-level field assessment (186 m³ ha⁻¹). Using average pixel values within a segment resulted in a higher proportion of pine and a lower proportion of spruce volume than using single pixel values. It also resulted in an estimated felling potential nearly 10% higher over the first 10-year period in the scenario analysis of the area dedicated to timber production. However, the maximum long-term sustainable removal was at the same level (about 30,000 m³ year⁻¹) for both feature sets over the simulated 30-year period. The resulting annual felling area in the first 10-year period was 12% lower when the segment averages were applied, but the difference subsequently levelled off. The kNN approach in estimating initial forest data for scenario analyses at the local level was found promising.     

Strategy for implementing silvicultural practices in Japanese plantation forests to meet a carbon sequestration goal

The strategy for implementing silvicultural practices in Japanese plantation forests was examined to achieve a carbon uptake of 13.0 Mt-C year^–1, which was capped by the Marrakesh Accords, during the first commitment period, 2008–2012. The plantation forests that implemented silvicultural practices in the period 1990–2012 (FM plantation forests) were identified in compliance with the hypothesized identification rules, and carbon uptake in the forests was estimated using a simple model composed of simulation and optimization components on the assumption that whole plantation forest is classified into only two groups. Furthermore, parametric analysis was conducted to investigate the relationships among three factors: (1) the average annual harvesting volume (including thinning) in plantation forests during the first commitment period, (2) the total area of FM plantation forests in 2012, and (3) the average annual amount of carbon to be sequestered in FM plantation forests during the first commitment period. The results imply that young stands have to be prioritized in implementing silvicultural practices under any harvesting plan and carbon sequestration goal, and that FM plantation forests sequestered 8.0–10.5 (Mt-C year^–1) carbon in inverse proportion to the harvesting volume of 21.0–14.0 million m³ year^–1 (log volume), assuming that most of the plantation forests were incorporated into them.     

Fine root dynamics in three central Himalayan high elevation forests ranging from closed canopied to open-canopied treeline vegetation

Fine root biomass, rates of dry matter production and nutrients dynamics were estimated for 1 year in three high elevation forests of the Indian central Himalaya. Fine root biomass and productivity were higher in closed canopied cappadocian maple forest (9.92 Mg ha⁻¹ and 6.34 Mg ha⁻¹ year⁻¹, respectively), followed by Himalayan birch forest (6.35 Mg ha⁻¹ and 4.44 Mg ha⁻¹ year⁻¹) and Bell rhododendron forest (6.23 Mg ha⁻¹ and 2.94 Mg ha⁻¹ year⁻¹). Both fine root biomass and productivity declined with an increase in elevation. Across the sites, fine root biomass was maximal in fall and minimal in summer. In all sites, maximum nutrient concentration in fine roots was in the rainy season and minimum in winter. Fine root biomass per unit basal area was positively related with elevation, Bell rhododendron forest having the largest fine root biomass per unit of basal area (0.53 Mg m⁻²) and cappadocian maple the least (0.18 Mg m⁻²). The production efficiency of fine roots per unit of leaf biomass also increased with elevation and ranged from 1.13 g g⁻¹ leaf mass year⁻¹ in cappadocian maple forest to 1.28 g g⁻¹ leaf mass year⁻¹ in Bell rhododendron forest. Present fine root turnover estimates showed a decline towards higher elevations (0.72 year⁻¹ in cappadocian maple and 0.58 year⁻¹ in Bell rhododendron forest) and are higher than global estimates (0.52).     

Relationships between nursery practices and field performance for Eucalyptus plantations in Brazil

The 3.5 million ha of Eucalyptus plantations in Brazil support many domestic and industrial activities. In the pulpwood sector, forest productivity has increased from 12 to 40 m³ ha^–1 year^–1 through breeding and silviculturalpractices. Nurseries have fostered thisevolution with changes in container/substratetypes, propagation methods and specificinfrastructure for each plant growth phase.Eucalyptus plants are mainly produced bycuttings, using rigid tube containers filledwith vermiculite-organic compound substrates.Stock quality is based on morphologicalcharacteristics of the plants, andenvironmental conditions are highly significantfor plant performance. Performance is dependenton physiological short-term effects related tosurvival and long-term effects of genotype/rootmorphology related to tree development. Currentsilvicultural trends are reducing establishmentcosts but increasing the risk of using lowquality plants. The development of fieldperformance models and nursery physiologicaltests is recommended for Eucalyptusplantations in Brazil. Improved experimentaldesigns are needed to capture the interactionbetween plant quality and field performance.     

Effect of tree species on carbon stocks in forest floor and mineral soil and implications for soil carbon inventories

Forest soil organic carbon (SOC) and forest floor carbon (FFC) stocks are highly variable. The sampling effort required to assess SOC and FFC stocks is therefore large, resulting in limited sampling and poor estimates of the size, spatial distribution, and changes in SOC and FFC stocks in many countries. Forest SOC and FFC stocks are influenced by tree species. Therefore, quantification of the effect of tree species on carbon stocks combined with spatial information on tree species distribution could improve insight into the spatial distribution of forest carbon stocks.We present a study on the effect of tree species on FFC and SOC stock for a forest in the Netherlands and evaluate how this information could be used for inventory improvement. We assessed FFC and SOC stocks in stands of beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii), Scots pine (Pinus sylvestris), oak (Quercus robur) and larch (Larix kaempferi).FFC and SOC stocks differed between a number of species. FFC stocks varied between 11.1 Mg C ha⁻¹ (beech) and 29.6 Mg C ha⁻¹ (larch). SOC stocks varied between 53.3 Mg C ha⁻¹ (beech) and 97.1 Mg C ha⁻¹ (larch). At managed locations, carbon stocks were lower than at unmanaged locations. The Dutch carbon inventory currently overestimates FFC stocks. Differences in carbon stocks between conifer and broadleaf forests were significant enough to consider them relevant for the Dutch system for carbon inventory.     

Nutrient cycling and soil leaching in eighteen pure and mixed stands of beech (Fagus sylvatica) and spruce (Picea abies)

Studies on the combined effects of beech–spruce mixtures are very rare. Hence, forest nutrition (soil, foliage) and nutrient fluxes via throughfall and soil solution were measured in adjacent stands of pure spruce, mixed spruce–beech and pure beech on three nutrient rich sites (Flysch) and three nutrient poor sites (Molasse) over a 2-year period. At low deposition rates (highest throughfall fluxes: 17 kg N ha⁻¹ year⁻¹ and 5 kg S ha⁻¹ year⁻¹) there was hardly any linkage between nutrient inputs and outputs. Element outputs were rather driven by internal N (mineralization, nitrification) and S (net mineralization of organic S compounds, desorption of historically deposited S) sources. Nitrate and sulfate seepage losses of spruce–beech mixtures were higher than expected from the corresponding single-species stands due to an unfavorable combination of spruce-similar soil solution concentrations coupled with beech-similar water fluxes on Flysch, while most processes on Molasse showed linear responses. Our data show that nutrient leaching through the soil is not simply a “wash through” but is mediated by a complex set of reactions within the plant–soil system.     

Silvicultural strategies for increased timber harvesting in a Central European mountain landscape

The demand for wood as construction material, renewable source for energy and feedstock for chemicals is expected to increase. However, timber increments are currently only partly harvested in many European mountain regions, which may lead to supply shortages for local timber industries, decreases in forest resistance to disturbances and functioning as protection from gravitational hazards. Using an inventory-based forest simulator, we evaluated scenarios to increase wood mobilization in the 7105-km² Swiss canton of Grisons for the period 2007–2106. Scenarios varied with respect to landscape-scale harvesting amounts and silvicultural strategies (low vs. high stand-scale treatment intensity) and accounted for regulations and incentives for protection forest management. With 50 and 100% increases of harvests, the current average growing stock of 319 m³ ha^?1 was simulated to be reduced by 12 and 33%, respectively, until 2106 in protection forests of Northern Grisons, where management is prioritized due to subsidies. Outside protection forests and in Southern Grisons, growing stock was simulated to continually increase, which led to divergent developments in forest structure in- and outside protection forests and in the Northern and Southern Grisons. The effect of silvicultural strategies on simulated forest structure was small compared to the effect of future harvesting levels. We discuss opportunities and threats of decreasing management activities outside protection forests and advocate for incentives to promote natural regeneration also outside protection forests to safeguard long-term forest stability.     

Atmospheric deposition and leaching of nitrogen in Chinese forest ecosystems

Data have been compiled from published sources on nitrogen (N) fluxes in precipitation, throughfall, and leaching from 69 forest ecosystems at 50 sites throughout China, to examine at a national level: (1) N input in precipitation and throughfall, (2) how precipitation N changes after the interaction with canopy, and (3) whether N leaching increases with increasing N deposition and, if so, to what extent. The deposition of dissolved inorganic N (DIN) in precipitation ranged from 2.6 to 48.2 kg N ha⁻¹ year⁻¹, with an average of 16.6 kg N ha⁻¹ year⁻¹. Ammonium was the dominant form of N at most sites, accounting for, on average, 63% of total inorganic N deposition. Nitrate accounted for the remaining 37%. On average, DIN fluxes increased through forest canopies, by 40% and 34% in broad-leaved and coniferous forests, respectively. No significant difference in throughfall DIN inputs was found between the two forest types. Overall, 22% of the throughfall DIN input was leached from forest ecosystems in China, which is lower than the 50–59% observed for European forests. Simple calculations indicate that Chinese forests have great potential to absorb carbon dioxide from the atmosphere, because of the large forest area and high N deposition.