Post-fire salvage logging increases restoration costs in a Mediterranean mountain ecosystem

Post-fire salvage logging (i.e. felling and removing burnt trees, often eliminating the remaining woody debris) is a practice routinely performed by forest managers worldwide. In Mediterranean-type ecosystems, salvage logging is considered a measure to reduce future reforestation costs, but this assumption remains largely untested. We made a cost analysis of different management schemes, addressing the immediate post-fire burnt-wood management as well as the costs and success of subsequent reforestation efforts. Two experimental 25-ha plots were established in a burnt pine reforestation of SE Spain, in which three replicates of three post-fire treatments were applied: non-intervention (NI), partial cut plus lopping (PCL; felling and lopping off the branches from most of the trees, leaving all biomass in situ), and salvage logging (SL). After 4?years, a mechanised reforestation was undertaken, and seedling mortality was monitored for 2?years. The cost of all management operations was recorded in situ, and the cost of re-planting the dead seedlings was estimated according to the expenses of previous reforestation. Initial cost of wood management was greatest in SL and zero in NI. Reforestation cost was highest in NI and lowest in SL, and seedling-mortality rates proved lowest in PCL (43?% vs. 51?% and 52?% in SL and NI, respectively). Considering all the post-fire management operations, salvage logging did not provide particular economic advantages for forest restoration, and had an overall cost of 3,436?±?340?€/ha. By contrast, NI and PCL reduced total restoration costs by 50 and 35?%, respectively, and PCL indeed promoted restoration success. We suggest that the full cost of management operations needs to be considered when evaluating the economic implications of post-fire salvage logging.     

Management of burnt wood after fire affects post-dispersal acorn predation

The management of burnt wood after a fire may affect seed predation by vertebrates due to the change produced in habitat structure. We analyze the effect of burnt wood management on post-dispersal seed predation in the Holm oak. Three plots were established in a burnt forest, with three treatments per plot: (1) non-intervention (NI, all trees left standing), (2) “partial cut plus lopping” (PCL, felling 90% of trees, cutting their main branches, leaving all the biomass in situ), and (3) “salvage logging” (SL, felling the logs for their removal and masticating the woody debris). Acorns were buried to mimic dispersal by jays or rodents two and three years after fire, with two trials per year (7200 monitored acorns), and the predation rate was evaluated until the time of seedling emergence. The spatial patterns of acorn predation were assessed by computing a transformed-Ripley's K function and Moran's I correlograms. There was a large spatial and temporal variability in acorn predation, with differences among trials, plots, and replicates within treatments and plots. Overall, PCL showed the lowest predation values (83.0% versus 87.4 in NI and 88.0 in SL). Predator species (mice versus wild boar) also differed among treatments, wild boar having a negligible effect in PCL, presumably due to the physical barrier of felled logs and branches. The results support that: (1) salvage logging offers no advantage against predators and (2) that post-fire burnt wood management alters the guild of acorn predators and may reshape the pattern of seedling establishment.     

Post-fire soil respiration in relation to burnt wood management in a Mediterranean mountain ecosystem

After a wildfire, the management of burnt wood may determine microclimatic conditions and microbiological activity with the potential to affect soil respiration. To experimentally analyze the effect on soil respiration, we manipulated a recently burned pine forest in a Mediterranean mountain (Sierra Nevada National and Natural Park, SE Spain). Three representative treatments of post-fire burnt wood management were established at two elevations: (1) “salvage logging” (SL), where all trees were cut, trunks removed, and branches chipped; (2) “non-intervention” (NI), leaving all burnt trees standing; and (3) “cut plus lopping” (CL), a treatment where burnt trees were felled, with the main branches lopped off, but left in situ partially covering the ground surface. Seasonal measurements were carried out over the course of two years. In addition, we performed continuous diurnal campaigns and an irrigation experiment to ascertain the roles of soil temperature and moisture in determining CO₂ fluxes across treatments. Soil CO₂ fluxes were highest in CL (average of 3.34 ± 0.19 μmol m⁻² s⁻¹) and the lowest in SL (2.21 ± 0.11 μmol m⁻² s⁻¹). Across seasons, basal values were registered during summer (average of 1.46 ± 0.04 μmol m⁻² s⁻¹), but increased during the humid seasons (up to 10.07 ± 1.08 μmol m⁻² s⁻¹ in spring in CL). Seasonal and treatment patterns were consistent at the two elevations (1477 and 2317 m a.s.l.), although respiration was half as high at the higher altitude.Respiration was mainly controlled by soil moisture. Watering during the summer drought boosted CO₂ effluxes (up to 37 ± 6 μmol m⁻² s⁻¹ just after water addition), which then decreased to basal values as the soil dried. About 64% of CO₂ emissions during the first 24 h could be attributed to the degasification of soil pores, with the rest likely related to biological processes. The patterns of CO₂ effluxes under experimental watering were similar to the seasonal tendencies, with the highest pulse in CL. Temperature, however, had a weak effect on soil respiration, with Q₁₀ values of ca. 1 across seasons and soil moisture conditions. These results represent a first step towards illustrating the effects of post-fire burnt wood management on soil respiration, and eventually carbon sequestration.     

Potential knowledge gain in large-scale simulations of forest carbon fluxes from remotely sensed biomass and height

Global vegetation models (GVMs) simulate CO₂, water and energy fluxes at large scales, typically no smaller than 10 × 10 km. GVM simulations are thus expected to simulate the average functioning, but not the local variability. The two main limiting factors in refining this scale are (1) the scale at which the pedo-climatic inputs - temperature, precipitation, soil water reserve, etc. - are available to drive models and (2) the lack of geospatial information on the vegetation type and the age of forest stands. This study assesses how remotely sensed biomass or stand height could help the new generation of GVMs, which explicitly represent forest age structure and management, to better simulate this local variability. For the ORCHIDEE-FM model, we find that a simple assimilation of biomass or height brings down the root mean square error (RMSE) of some simulated carbon fluxes by 30-50%. Current error levels of remote sensing estimates do not impact this improvement for large gross fluxes (e.g. terrestrial ecosystem respiration), but they reduce the improvement of simulated net ecosystem productivity, adding 13.5-21% of RMSE to assimilations using the in situ estimates. The data assimilation under study is more effective to improve the simulation of respiration than the simulation of photosynthesis. The assimilation of height or biomass in ORCHIDEE-FM enables the correct retrieval of variables that are more difficult to measure over large areas, such as stand age. A combined assimilation of biomass and net ecosystem productivity could possibly enable the new generation of GVMs to retrieve other variables that are seldom measured, such as soil carbon content.     

Derivation of a spatially explicit 86-year retrospective carbon budget for a landscape undergoing conversion from old-growth to managed forests on Vancouver Island,BC

To understand the influence of disturbance, age–class structure, and land use on landscape-level carbon (C) budgets during conversion of old-growth forests to managed forests, a spatially explicit, retrospective C budget from 1920 through 2005 was developed for the 2500 ha Oyster River area of Fluxnet-Canada's coastal BC Station. We used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), an inventory-based model, to simulate forest C dynamics. A current (circa 1999) forest inventory for the area was compiled, then overlaid with digitized historic disturbance maps, a 1919 timber cruise map, and a series of historic orthophotographs to generate a GIS coverage of forest cover polygons with unique disturbance histories dating back to 1920. We used the combined data from the historic and current inventory and forest change data to first estimate initial ecosystem C stocks and then to simulate forest dynamics and C budgets for the 86-year period. In 1920, old-growth forest dominated the area and the long-term landscape-level net ecosystem C balance (net biome productivity, NBP) was a small sink (NBP 0.2 Mg C ha⁻¹ year⁻¹). From 1930 to 1945 fires, logging, and slash burning resulted in large losses of biomass C, emissions of C to the atmosphere, and transfers of C from biomass to detritus and wood products (NBP ranged from −3 to −56 Mg C ha⁻¹ year⁻¹). Live biomass C stocks slowly recovered following this period of high disturbance but the area remained a C source until the mid 1950s. From 1960 to 1987 disturbance was minimal and the area was a C sink (NBP ranged from 3 to 6 Mg C ha⁻¹ year⁻¹). As harvest of second-growth forest began in late 1980s, disturbances again dominated the area's C budget, partially offset by ongoing C uptake by biomass in recovering young forests such that the C balance varied from positive to negative depending upon the area disturbed that year (NBP from 6 to −15 Mg C ha⁻¹ year⁻¹). Despite their high productivity, the area's forests are not likely to attain C densities of the landscape prior to industrial logging because the stands will not reach pre-logging ages. Additional work is underway to examine the relative role historic climate variability has had on the landscape-level C budget.     

Carbon pools and productivity in a 1-km heterogeneous forest and peatland mosaic in Minnesota,USA

Determining the magnitude of carbon (C) storage in forests and peatlands is an important step towards predicting how regional carbon balance will respond to climate change. However, spatial heterogeneity of dominant forest and peatland cover types can inhibit accurate C storage estimates. We evaluated ecosystem C pools and productivity in the Marcell Experimental Forest (MEF), in northern Minnesota, USA, using a network of plots that were evenly spaced across a heterogeneous 1-km² mosaic composed of a mix of upland forests and peatlands. Using a nested plot design, we estimated the standing C stock of vegetation, coarse detrital wood and soil pools. We also estimated aboveground net primary production (ANPP) as well as coarse root production. Additionally we evaluated how vegetation cover types within the study area differed in C storage. The total ecosystem C pool did not vary significantly among upland areas dominated by aspen (160 ± 13 Mg C ha⁻¹), mixed hardwoods (153 ± 19 Mg C ha⁻¹), and conifers (197 ± 23 Mg C ha⁻¹). Live vegetation accounted for approximately 50% of the total ecosystem C pool in these upland areas, and soil (including forest floor) accounted for another 35–40%, with remaining C stored as detrital wood. Compared to upland areas, total C stored in peatlands was much greater, 1286 ± 125 Mg C ha⁻¹, with 90–99% of that C found in peat soils that ranged from 1 to 5 m in depth. Forested areas ranged from 2.6 to 2.9 Mg C ha⁻¹ in ANPP, which was highest in conifer-dominated upland areas. In alder-dominated and black spruce-dominated peatland areas, ANPP averaged 2.8 Mg C ha⁻¹, and in open peatlands, ANPP averaged 1.5 Mg C ha⁻¹. In treed areas of forest and peatlands, our estimates of coarse root production ranged from 0.1 to 0.2 Mg C ha⁻¹. Despite the lower production in open peatlands, all peatlands have acted as long-term C sinks over hundreds to thousands of years and store significantly more C per unit area than is stored in uplands. Despite occupying only 13% of our study area, peatlands store almost 50% of the C contained within it. Because C storage in peatlands depends largely on climatic drivers, the impact of climate changes on peatlands may have important ramifications for C budgets of the western Great Lakes region.     

Component carbon fluxes and their contribution to ecosystem carbon exchange in a pine forest: an assessment based on eddy covariance measurements and an integrated model

We used a combination of eddy flux, canopy, soil and environmental measurements with an integrated biophysical model to analyze the seasonality of component carbon (C) fluxes and their contribution to ecosystem C exchange in a 50-year-old Scots pine forest (Pinus sylvestris L.) in eastern Finland (62 degrees 47' N, 30 degrees 58' E) over three climatically contrasting years (2000-2002). Eddy flux measurements showed that the growing Scots pine forest was a sink for CO2, with annual net C uptakes of 131, 210 and 258 g C m-2> year-1 in 2000, 2001 and 2002, respectively. The integrated process model reproduced the annual course of daily C flux above the forest canopy as measured by the eddy covariance method once the site-specific component parameters were estimated. The model explained 72, 66 and 68% of the variation in daily net C flux in 2000, 2001 and 2002, respectively. Modeled annual C loss by respiration was 565, 629 and 640 g C m-2 year-1, accounting for 77, 77 and 65% of annual gross C uptake, respectively. Carbon fluxes from the forest floor were the dominant contributors to forest ecosystem respiration, with the fractions of annual respiration from the forest floor, foliage and wood being 46-62, 27-44 and 9-10%, respectively. The wide range in daily net C uptake during the growing season was largely attributable to day-to-day fluctuations in incident quantum irradiance. During just a few days in early spring and late autumn, ecosystem net C exchange varied between source and sink as a result of large daily changes in temperature. The forest showed a greater reduction in gross C uptake by photosynthesis than in C loss by respiration during the dry summer of 2000, indicating that interannual variability in ecosystem net C uptake at this site was modified mostly by summer rainfall and vapor pressure deficit.     

Long-term management impacts on carbon storage in Lake States forests

We examined carbon storage following 50+ years of forest management in two long-term silvicultural studies in red pine and northern hardwood ecosystems of North America’s Great Lakes region. The studies contrasted various thinning intensities (red pine) or selection cuttings, shelterwoods, and diameter-limit cuttings (northern hardwoods) to unmanaged controls of similar ages, providing a unique opportunity to evaluate long-term management impacts on carbon pools in two major North American forest types. Management resulted in total ecosystem carbon pools of 130-137 Mg ha⁻¹ in thinned red pine and 96-177 Mg ha⁻¹ in managed northern hardwoods compared to 195 Mg ha⁻¹ in unmanaged red pine and 224 Mg ha⁻¹ in unmanaged northern hardwoods. Managed stands had smaller tree and deadwood pools than unmanaged stands in both ecosystems, but management had limited impacts on understory, forest floor, and soil carbon pools. Total carbon storage and storage in individual pools varied little across thinning intensities in red pine. In northern hardwoods, selection cuttings stored more carbon than the diameter-limit treatment, and selection cuttings generally had larger tree carbon pools than the shelterwood or diameter-limit treatments. The proportion of total ecosystem carbon stored in mineral soil tended to increase with increasing treatment intensity in both ecosystems, while the proportion of total ecosystem carbon stored in the tree layer typically decreased with increasing treatment intensity. When carbon storage in harvested wood products was added to total ecosystem carbon, selection cuttings and unmanaged stands stored similar levels of carbon in northern hardwoods, but carbon storage in unmanaged stands was higher than that of thinned stands for red pine even after adding harvested wood product carbon to total ecosystem carbon. Our results indicate long-term management decreased on-site carbon storage in red pine and northern hardwood ecosystems, but thinning intensity had little impact on carbon storage in red pine while increasing management intensity greatly reduced carbon storage in northern hardwoods. These findings suggest thinning to produce different stand structures would have limited impacts on carbon storage in red pine, but selection cuttings likely offer the best carbon management options in northern hardwoods.     

Impacts of selective logging on above-ground forest biomass in the Monts de Cristal in Gabon

Selective logging is an important socio-economic activity in the Congo Basin but one with associated environmental costs, some of which are avoidable through the use of reduced-impact logging (RIL) practices. With increased global concerns about biodiversity losses and emissions of carbon from forest in the region, more information is needed about the effects of logging on forest structure, composition, and carbon balance. We assessed the consequences of low-intensity RIL on above-ground biomass and tree species richness in a 50 ha area in northwestern Gabon. We assessed logging impacts principally in 10 randomly located 1-ha plots in which all trees ?10 cm dbh were measured, identified to species, marked, and tagged prior to harvesting. After logging, damage to these trees was recorded as being due to felling or skidding (i.e., log yarding) and skid trails were mapped in the entire 50-ha study area. Allometric equations based on tree diameter and wood density were used to transform tree diameter into biomass.Logging was light with only 0.82 trees (8.11 m³) per hectare extracted. For each tree felled, an average of 11 trees ?10 cm dbh suffered crown, bole, or root damage. Skid trails covered 2.8% of the soil surface and skidding logs to the roadside caused damage to an average of 15.6 trees ?10 cm dbh per hectare. No effect of logging was observed on tree species richness and pre-logging above-ground forest biomass (420.4 Mg ha⁻¹) declined by only 8.1% (34.2 Mg ha⁻¹). We conclude from these data that with harvest planning, worker training in RIL techniques, and low logging intensities, substantial carbon stocks and tree species richness were retained in this selectively logged forest in Gabon.     

Managing forests for wood yield and carbon storage: a theoretical study

Which forest management regimes best achieve the dual objectives of high sustained timber yield and high carbon storage, including the carbon stored in soil and wood products? A mechanistic forest ecosystem simulator, which couples carbon, nitrogen and water (Edinburgh Forest Model), was calibrated to mimic the growth of a pine plantation in a Scottish climate. The model was then run to equilibrium (1) as an undisturbed forest, (2) removing 2.5, 10, 20 or 40% of the woody biomass each year (3) removing 50% of the woody biomass every 20 years, and (4) clear-felling and replanting every 60 years as in conventional plantations in this climate. More carbon was stored in the undisturbed forest (35.2 kg C m(-2)) than in any regime in which wood was harvested. Plantation management gave moderate carbon storage (14.3 kg C m(-2)) and timber yield (15.6 m(3) ha(-1) year(-1)). Notably, annual removal of 10 or 20% of woody biomass per year gave both a high timber yield (25 m(3) ha(-1) year(-1)) and high carbon storage (20 to 24 kg C m(-2)). The efficiency of the latter regimes could be attributed (in the model) to high light interception and net primary productivity, but less evapotranspiration and summer water stress than in the undisturbed forest, high litter input to the soil giving high soil carbon and N(2) fixation, low maintenance respiration and low N leaching owing to soil mineral pool depletion. We conclude that there is no simple inverse relationship between the amount of timber harvested from a forest and the amount of carbon stored. Management regimes that maintain a continuous canopy cover and mimic, to some extent, regular natural forest disturbance are likely to achieve the best combination of high wood yield and carbon storage.     

Bottomland hardwood forest recovery following tornado disturbance and salvage logging

Catastrophic wind events, including tornado, hurricane, and linear winds, are significant disturbances in temperate forested wetlands. Information is lacking on how post-disturbance salvage logging may impact short and long-term objectives in conservation areas where natural stands are typically managed passively. Woody regeneration and herbaceous cover were assessed for three years in a bottomland hardwood forest across a gradient of damage from an F4 tornado, with and without subsequent salvage logging. Soil disturbance intensity and recovery associated with salvage logging within wind-disturbed sites were also assessed. Woody stem density and proportion of potential overstory species (species with the potential to occupy a position in the canopy) increased as a function of wind disturbance intensity. Stem density, proportion of overstory trees, or species diversity did not differ between wind + salvage and wind-disturbed-only plots. Significant dissimilarity occurred among soil disturbance classes within salvaged sites. By the third growing season, vegetation in soil disturbance classes in wind + salvage areas was converging toward undisturbed conditions and bottomland hardwood forest recovery was underway in all vegetation disturbance types and soil disturbance classes. Post-tornado salvage logging, applied judiciously, may contribute to microsite and vegetation diversity.     

The effects of wildfire, salvage logging, and post-fire N-fixation on the nutrient budgets of a Sierran forest

The effects of fire, post-fire salvage logging, and revegetation on nutrient budgets were estimated for a site in the eastern Sierra Nevada Mountains that burned in a wildfire in 1981. Approximately two decades after the fire, the shrub (former fire) ecosystem contained less C and more N than the adjacent forest ecosystem. Reconstruction of pre-fire nutrient budgets suggested that most C was exported in biomass during salvage logging and will not be recovered until forest vegetation occupies the site again. Salvage logging may have resulted in longer-term C sequestration in wood products than would have occurred had the logs been left in the field to decay, however. Reconstructed budgets suggested that most N was lost via volatilization during the fire rather than in post-fire salvage logging (assuming that foliage and O horizons were combusted). Comparisons of the pre-fire and present day N budgets also suggested that the lost N was rapidly replenished in O horizons and mineral soils, probably due to N-fixation by snowbush (Ceanothus velutinus Dougl.), the dominant shrub on the former fire site. There were no significant differences in ecosystem P, K, or S contents and no consistent, significant differences in soil extractable P or S between the shrub and forested plots. Exchangeable K⁺, Ca²⁺, and Mg²⁺ were consistently and significantly greater in shrub than in adjacent forested soils, however, and the differences were much larger than could be accounted for by estimated ash inputs. In the case of Ca, even the combustion of all aboveground organic matter could not account for more than a fraction of the difference in exchangeable pools. We speculate that the apparent large increased in soil and ecosystem Ca content resulted from either the release of Ca from non-exchangeable forms in the soil or the rapid uptake and recycling of Ca by post-fire vegetation.     

Partitioning of soil respiration into its autotrophic and heterotrophic components by means of tree-girdling in old boreal spruce forest

Forests accumulate much less carbon than the amount fixed through photosynthesis because of an almost equally large opposing flux of CO₂ from the ecosystem. Most of the return flux to the atmosphere is through soil respiration, which has two major sources, one heterotrophic (organisms decomposing organic matter) and one autotrophic (roots, mycorrhizal fungi and other root-associated microbes dependent on recent photosynthate). We used tree-girdling to stop the flow of photosynthate to the belowground system, hence, blocking autotrophic soil activity in a 120-yr-old boreal Picea abies forest. We found that at the end of the summer, two months after girdling, the treatment had reduced soil respiration by up to 53%. This figure adds to a growing body of evidence indicating (t-test, d.f. = 7, p < 0.05) that autotrophic respiration may contribute more to total soil respiration in boreal (mean 53 ± 2%) as compared to temperate forests (mean 44 ± 3%). Our data also suggests that there is a seasonal hysteresis in the response of total soil respiration to changes in temperature. We propose that this reflects seasonality in the tree below-ground carbon allocation.     

Impact of communal land use and conservation on woody vegetation structure in the Lowveld savannas of South Africa

Millions of people rely on savannas for ecosystem services, such as the provision of grazing and fuel wood, so it is important to determine the extent to which utilization affects woody vegetation resources. Using airborne LiDAR from the Carnegie Airborne Observatory (CAO), we quantified and compared tree canopy cover and height distributions between areas of contrasting management in the Lowveld savanna region of South Africa - a region connecting communal landscapes with heavy utilization (especially fuel wood harvesting) to fully protected public (Kruger National Park - KNP) and private reserves (SabiSand Game Reserve - SSGR) that conserve biodiversity. Differences in total woody vegetation cover and cover within functional height classes (1-2 m, 2-3 m, 3-5 m, 5-7 m and >7 m) were investigated between 7 sites located within (i) conservation areas (in KNP, SSGR), (ii) communal rangelands or (iii) cultivated fields in communal areas. The impact of human utilization on wood resources in the communal areas varied widely between sites. Heavy utilization on gabbro substrate greatly reduced total woody cover of the rangelands, while two other communal rangelands that were presumably less intensively utilised had double the total woody cover of conservation areas. Rangelands and fields in most of the communal sites had more vegetation cover in the 5-7 m and >7 m classes than most of the conservation sites, presumably due to the absence of elephants in communal rangelands and the active preservation of large fruiting trees. On granite substrates, which account for the majority of the study area, there was a 50% reduction in woody cover below 5 m in communal rangelands. Although large trees were clearly being conserved in communal rangelands and fields, there was a relatively low cover of vegetation below 5 m, which raise doubts about recruitment and long-term sustainability of the tree resources. These results in conjunction with other studies based on the CAO LiDAR data for experimental burn plots and large mammal exclosures in KNP, suggest that communal land use on granite substrates have a higher impact on the woody cover below 5 m than both elephants and fire.     

Singular and interactive effects of blowdown, salvage logging, and wildfire in sub-boreal pine systems

The role of disturbance in structuring vegetation is widely recognized; however, we are only beginning to understand the effects of multiple interacting disturbances on ecosystem recovery and development. Of particular interest is the impact of post-disturbance management interventions, particularly in light of the global controversy surrounding the effects of salvage logging on forest ecosystem recovery. Studies of salvage logging impacts have focused on the effects of post-disturbance salvage logging within the context of a single natural disturbance event. There have been no formal evaluations of how these effects may differ when followed in short sequence by a second, high severity natural disturbance. To evaluate the impact of this management practice within the context of multiple disturbances, we examined the structural and woody plant community responses of sub-boreal Pinus banksiana systems to a rapid sequence of disturbances. Specifically, we compared responses to Blowdown (B), Fire (F), Blowdown-Fire, and Blowdown-Salvage-Fire (BSF) and compared these to undisturbed control (C) stands. Comparisons between BF and BSF indicated that the primary effect of salvage logging was a decrease in the abundance of structural legacies, such as downed woody debris and snags. Both of these compound disturbance sequences (BF and BSF), resulted in similar woody plant communities, largely dominated by Populus tremuloides; however, there was greater homogeneity in community composition in salvage logged areas. Areas experiencing solely fire (F stands) were dominated by P. banksiana regeneration, and blowdown areas (B stands) were largely characterized by regeneration from shade tolerant conifer species. Our results suggest that salvage logging impacts on woody plant communities are diminished when followed by a second high severity disturbance; however, impacts on structural legacies persist. Provisions for the retention of snags, downed logs, and surviving trees as part of salvage logging operations will minimize these structural impacts and may allow for greater ecosystem recovery following these disturbance combinations.     

Carbon budget of Ontario's managed forests and harvested wood products, 2001–2100

Forest and harvested wood products (HWP) carbon (C) stocks between 2001 and 2100 for Ontario's managed forests were projected using FORCARB-ON, an adaptation of the U.S. national forest C budget model known as FORCARB2. A fire disturbance module was introduced to FORCARB-ON to simulate the effects of wildfire on C, and some of the model's C pools were re-parameterized using data from Canadian forests. Forest C stocks were estimated using allometric equations that represent the relationships between C and net merchantable volume and forest age based on forest inventory statistics. Other pools were included using results from ecological studies related to forest inventory variables. Data from future forest development projections adopted in approved management plans were used as model input to produce forest C budgets for the province's Crown forest management units. The estimates were extended to other types of managed forests in Ontario: parks, measured fire management zones, and private forest lands. Carbon in HWP was estimated in four categories: wood in use, wood in landfill, wood burned for energy, and C emitted by wood decomposition or burning without energy generation. We projected that the C stocks in Ontario's managed forests and HWP (in use and in landfills) would increase by 465.3 Mt from 2001 to 2100, of which 47.9 Mt is from increases in forest C and 417.4 Mt is from HWP C.     

Wood density in forests of Brazil's ‘arc of deforestation’: Implications for biomass and flux of carbon from land-use change in Amazonia

Wood density is an important variable in estimates of forest biomass and greenhouse-gas emissions from land-use change. The mean wood density used in estimates of forest biomass in the Brazilian Amazon has heretofore been based on samples from outside the “arc of deforestation”, where most of the carbon flux from land-use change takes place. This paper presents new wood density estimates for the southern and southwest Brazilian Amazon (SSWA) portions of the arc of deforestation, using locally collected species weighted by their volume in large local inventories. Mean wood density was computed for the entire bole, including the bark, and taking into account radial and longitudinal variation. A total of 403 trees were sampled at 6 sites. In the southern Brazilian Amazon (SBA), 225 trees (119 species or morpho-species) were sampled at 4 sites. In eastern Acre state 178 trees (128 species or morpho-species) were sampled at breast height in 2 forest types. Mean basic density in the SBA sites was 0.593 ± 0.113 (mean ± 1 S.D.; n = 225; range 0.265–0.825). For the trees sampled in Acre the mean wood density at breast height was 0.540 ± 0.149 (n = 87) in open bamboo-dominated forest and 0.619 ± 0.149 (n = 91) in dense bamboo-free forest. Mean wood density in the SBA sites was significantly higher than in the bamboo dominated forest but not the dense forest at the Acre site. From commercial wood inventories by the RadamBrasil Project in the SSWA portion of the arc of deforestation, the wood volume and wood density of each species or genus were used to estimate average wood density of all wood volume in each vegetation unit. These units were defined by the intersection of mapped forest types and states. The area of each unit was then used to compute a mean wood density of 0.583 g cm⁻³ for all wood volume in the SSWA. This is 13.6% lower than the value applied to this region in previous estimates of mean wood density. When combined with the new estimates for the SSWA, this gave an average wood density of 0.642 g cm⁻³ for all the wood volume in the entire Brazilian Amazon, which is 7% less than a prior estimate of 0.69 g cm⁻³. These results suggest that current estimates of carbon emissions from land-use change in the Brazilian Amazon are too high. The impact on biomass estimates and carbon emissions is substantial because the downward adjustment is greater in forest types undergoing the most deforestation. For 1990, with 13.8 × 10³ km² of deforestation, emissions for the Brazilian Amazon would be reduced by 23.4–24.4 × 10⁶ Mg CO₂-equivalent C/year (for high- and low-trace gas scenarios), or 9.4–9.5% of the gross emission and 10.7% of the net committed emission, both excluding soils.     

应用遥感、人工神经网络叶面积模型和模拟过程模型估计湿地松人工林碳储量

全球气候变化引起人们对森林碳固定作用的关注。碳存储速率依赖于生态系统流通量(光合作用和生态系统呼吸),量化为净生态系统二氧化碳交换。在没有密集采样点的情况下,我们需要采用估测森林净生态系统交换的方法准确地估计林分水平和更大尺度的碳固定量。本文通过祸合遥感估算的叶面积指数和生长过程拟合模型,估计了佛罗里达州内9 770公顷湿地松人工林一年里净生态系统交换总量。地面图神经网络模型和陆地卫星数据估计的森林叶面积指数平均值是1.06(数值范围0-3.93,包括森林边界)。输入神经网络叶面积指数值,湿地松拟合模型(SPM2)估计的森林净生态交换值在-5.52 Mg·hm-2·a-1到11.06Mg·hm-2·a-1之间,平均值是3.47 Mg·hm-2·a-1。年总的碳储量是33920t,约合3.5 t/hm2。估计的叶面积指数和森林净生态交换均对对施肥高度敏感。图3表1参30。     

Increased coniferous needle inputs accelerate decomposition of soil carbon in an old-growth forest

Changes in temperature, precipitation, and atmospheric carbon dioxide (CO₂) concentration that are expected in the coming decades will have profound impacts on terrestrial ecosystem net primary production (NPP). Nearly all models linking forest NPP with soil carbon (C) predict that increased NPP will result in either unchanged or increased soil C storage, and that decreased NPP will result in decreased soil C storage. However, linkages between forest productivity and soil C storage may not be so simple and direct. In an old-growth coniferous forest located in the H.J. Andrews Experimental Forest, OR, USA, we experimentally doubled needle litter inputs, and found that actual soil respiration rates exceeded those expected due to the C added by the extra needles. Here, we estimated that this ‘priming effect’ accounted for 11.5–21.6% of annual CO₂ efflux from litter-amended plots, or an additional 137–256 g C m⁻² yr⁻¹ loss of stored C to the atmosphere. Soil priming was seasonal, with greatest amounts occurring in June–August coincident with peaks in temperature and dry summer conditions. As a result of priming, mineral soil was more resistant to further mineralization during laboratory incubations. Soil lignin-derived phenols in the Double Litter plots were more oxidized than in the control, suggesting that the soil residue was more degraded. Our hypothesis that excess dissolved organic C produced from the added litter provided the link between the forest floor and mineral soil and a substrate for soil priming was not supported. Instead, the rhizosphere, and associated mycorrhizal fungi, likely responded directly to the added aboveground litter inputs. Our results revealed that enhanced NPP may lead to accelerated processing of some stored soil C, but that the effects of increased NPP on ecosystem C storage will be based on a net balance among all ecosystem C pools and are likely to be ecosystem-dependant. Forest C models need to include these complex linkages between forest productivity and soil C storage.     

Land use change and net C flux in Indian forests

This paper reports on the net carbon flux caused by deforestation and afforestation in India over the period from 1982 to 2002, separately for two time periods, 1982–1992 (PI) and 1992–2002 (PII), using the IPCC 2006 guidelines for greenhouse gas inventories. The approach accounts for forest and soil C pool changes for (a) forest areas remaining as forests, (b) afforested areas and (c) deforested areas. The data set used were remote sensing based forest cover for three time periods (1982, 1992, 2002), biomass increments, biomass expansion factors and wood density. In addition a number of required coefficients and parameters from published literature were adopted. In the 1982–2002 period, the forest cover changed from 64.20 Mha in 1982 to 63.96 and 67.83 Mha in 1992 and 2002 respectively. During the PI and PII periods, plantations were also established of 0.2 and 0.5 Mha yr⁻¹, while the annual deforestation rate was about 0.22 and 0.07 Mha in these periods, respectively.