Slash Removal Research Articles

Influence of forest infrastructure on the responses of ecosystem services to climate extremes in the Midwest and Northeast United States from 1980 to 2019

Forests provide several critical ecosystem services that help to support human society. Alteration of forest infrastructure by changes in land use, atmospheric chemistry, and climate change influence the ability of forests to provide these ecosystem services and their sensitivity to existing and future extreme climate events. Here, we explore how the evolving forest infrastructure of the Midwest and Northeast United States influences carbon sequestration, biomass increment (i.e., change in vegetation carbon), biomass burning associated with fuelwood and slash removal, the creation of wood products, and runoff between 1980 and 2019 within the context of changing environmental conditions and extreme climate events using a coupled modeling and assessment framework. For the 40-year study period, the region’s forests functioned as a net atmospheric carbon sink of 687 Tg C with similar amounts of carbon sequestered in the Midwest and the Northeast. Most of the carbon has been sequestered in vegetation (+771 Tg C) with more carbon stored in Midwestern trees than in Northeastern trees to provide a larger resource for potential wood products in the future. Runoff from forests has also provided 4,651 billion m3of water for potential use by humans during the study period with the Northeastern forests providing about 2.4 times more water than the Midwestern forests. Our analyses indicate that climate variability, as particularly influenced by heat waves, has the dominant effect on the ability of forest ecosystems to sequester atmospheric CO2to mitigate climate change, create new wood biomass for future fuel and wood products, and provide runoff for potential human use. Forest carbon sequestration and biomass increment appear to be more sensitive to heat waves in the Midwest than the Northeast while forest runoff appears to be more sensitive in the Northeast than the Midwest. Land-use change, driven by expanding suburban areas and cropland abandonment, has enhanced the detrimental heat-wave effects in Midwestern forests over time, but moderated these effects in Northeastern forests. When developing climate stabilization, energy production and water security policies, it will be important to consider how evolving forest infrastructure modifies ecosystem services and their responses to extreme climate events over time.

Cumulative effects of salvage logging and slash removal on erosion, soil functioning indicators and vegetation in a severely burned area in NW Spain

Post-fire salvage logging, a common practice in productive forest stands, can lead to increased soil erosion and loss of soil quality. However, further field research is required to confirm and clarify these effects. This study was conducted in NW Spain, in productive mixed stands of P. sylvestris and P. pinaster affected in the summer of 2015 by a crown fire that caused a high level of soil burn severity. Salvage logging was carried out nine months after the fire, and the effects of logging slash retention and slash removal were compared after a further two years. The study objectives were: i) to assess soil loss in the pre-logging period and compare it with the soil losses accumulated during the two post-logging annual periods, ii) to determine whether logging slash can mitigate soil erosion after post-fire logging and iii) to compare the effects of slash cover and slash removal on soil physical, chemical and microbiological parameters and vegetation recovery and iv) to evaluate the short-term effect of salvage logging on soil functionality. Soil loss in the period between the wildfire and salvage logging (September-June) was 4.2 Mg ha−1. Soil loss was significantly lower (by 2.4 times) in the post-salvage logging period than in the pre-logging period. Slash cover significantly reduced soil loss (2.6 compared with 1.7 Mg ha−1), with no detrimental effect on soil properties and no effect on the recovery of natural vegetation cover.Around three years after a wildfire followed by logging, while soil physical parameters analyzed did not show values reflecting a severe impact, symptoms of delayed recovery of soil microbial and enzymatic attributes were detected. Our study also revealed a contrasting difference between the slow recovery of the soil physical and microbial properties and the rapid recovery of the vegetation. Further research will be needed to clarify that response.

Effects of forest harvesting and biomass removal on soil carbon and nitrogen: Two complementary meta-analyses

Forest residues and logging slash from pre-commercial forest thinning and regeneration harvests are a potential feedstock for bioenergy production but there has been a concern about the impact of residue removal on forest soil C and N. This study aimed to address such by conducting two meta-analyses using the data available from published literature and an independent dataset compiled from the North American Long-Term Soil Productivity (LTSP) study.For the meta-analysis using literature, we categorized forest harvesting and biomass removal into i) no harvest control, ii) bole-only (BO, partial or clearcut) regular harvests, iii) BO with partial removal of logging slash and/or O horizon (BO+Removal), iv) whole tree harvests (WTH), and v) WTH with slash and O horizon removal (WTH+Removal). Accordingly, we compiled soil C and N data and key statistics (e.g., standard deviation) from 142 scientific articles published since 1979. We compared the results from this meta-analysis with data from 22 installations of the LTSP study where three levels of organic matter removal - BO, WTH, and WTH plus forest floor (+FF, O horizon) removal - as well as an additional vegetation control (+VC) were measured for two decades in either completely randomized or randomized block design.In the literature meta-analysis, BO+Removal (-19.2%), WTH (-15.4%) and WTH+Removal (-24.9%) contained significantly less soil C than no-harvest controls across combined soil depths, while BO had no difference. Within individual mineral soil horizons, only BO+Removal and WTH+Removal treatments contained significantly less carbon than controls. There was a high degree of heterogeneity in treatment response between studies in the literature. The analyses from the LTSP dataset showed no significant difference in combined soil depths for WTH or WTH+VC relative to BO harvest, but there was significantly less soil C in BO+VC (-3.6%), WTH+FF (-8.5%) and WTH+FF+VC (-15.3%). These treatment effects declined over time since harvest, particularly the most intensive treatments. Soil N results largely mirrored soil C in both meta-analyses with smaller estimated effects for most treatments at equivalent depths (except for WTH+Removal and WTH+FF+VC, which remain about the same). There were no significant differences in soil N for combined soil depths between WTH and no-harvest control (in the literature analysis) or BO harvest (for both analyses).Since the most severe losses of soil C and N involved FF removal, WTH that accounts for modest removals (<80%) of harvesting residues may provide a sustainable source of biomass for bioenergy production without additional soil impacts compared to BO harvesting practices.

Soil respiration following Chinese fir plantation clear-cut: Comparison of two forest regeneration approaches

In response to ecological problems originating from long-term pure coniferous plantations, clear-cut, species mixing, and other forest regeneration practices have been proposed to develop into mixed conifer-broadleaved stand. However, the dynamic effects of these forest regeneration approaches on soil respiration have not been well investigated. In this study, we compared soil respiration for three continuous years from two completely different forest regeneration approaches in clear-cut areas with uncut as control in pure Chinese fir plantations in subtropical China. These two approaches were, I: ground vegetation cut and removal of slash in the first year followed by the second year's ground vegetation cut but retained on the site, and II: ground vegetation cut and slash burning in first year followed by second year's soil ploughing, replanting, ground vegetation cut but retained on the site. Soil respiration changed obviously as forest practices were applied in the both regeneration sites. Mean respiration rate for the first year was lower for the treatments of Approach I and Approach II than uncut control (−15.0% and −26.8%), indicating that soil respiration decreased with ground vegetation removal or slash burning after clear-cut. In contrast to the first year, mean respiration rate was higher for the treatments of Approach I and Approach II treatments than uncut control (+12.8% and +32.2% in the second year, 16.3% and 30.8% in the third year), indicating ground vegetation cut with retaining residuals or soil ploughing significantly increased soil respiration. These drastically changes were mainly due to the rapid growth of understory vegetation and new seedlings, the difference of species composition, the availability of respired organic matter and the intensity of soil disturbance induced by different specific forest practices of two regeneration approaches over time. In addition, the different species mixing and forest management practices enhance the uncertainty linked to the analyses of soil respiration. Our results suggest that high intensity forest regeneration approach has a higher soil CO2 emission and lower production of biomass. Forest regeneration approaches could decrease the temperature sensitivity of soil respiration. Our findings provide new insights into the effects of forest practices on soil CO2 flux following clear-cut.

Effects of mechanical site preparation and slash removal on long-term productivity of conifer plantations in Sweden

Mechanical site preparation is commonly used to increase survival and early growth of newly planted seedlings. Ideally, any early positive effects of site preparation should persist for a long time, but concerns have been raised as to whether intensive site preparation might have a negative effect on the long-term productivity of a stand. The present study was therefore designed to investigate the long-term effects of different site-preparation methods on productivity and determine any possible interactions with tree species and site fertility. In the 1980s, a randomized block experiment was established at sites throughout Sweden. Four site-preparation methods of various intensities were performed on different sites: (i) an untreated control, (ii) disc trenching, (iii) mounding, and (iv) ploughing. As a complementary treatment, slash was either retained or removed from some plots. Depending on soil moisture class, geographical position, and site index, Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), or lodgepole pine (Pinus contorta Douglas ex Loudon) were planted in pure stands. Growth variables such as height and diameter were measured during the first years after establishment. After about 30 years, these variables were remeasured at the level of individual trees. Overall, an increased production of the planted trees after site preparation was found. Neither intensive site preparation (such as ploughing) nor slash removal had any negative effect on the long-term productivity of these experimental stands.

Soil respiration after slash and stump removal in three clear-cut areas with patch scarification and mounding

ABSTRACTWe studied the soil carbon dioxide respiration (Rs) at three clear-cut mesic forest sites in south, central and north central Finland, which had been treated with different intensities of stump lifting and slash removal and then patch mounded and planted with spruce. The follow-up period after the initial calibration lasted for five consecutive years. Throughout the study the Rs remained at fairly steady levels according to the study site and soil disturbance level. Based on a split-plot test using the general linear model there were no significant differences in the Rs between the different stump and slash removal treatments at the three study sites, but unaffected and moderately affected soil surfaces had significantly higher Rs than mounds and wheel ruts. We conclude that the removal of stumps and slash have minor direct effects on Rs, but large indirect effects through soil disturbance.

High-pruning of silver birch (Betula pendula Roth): work efficiency as a function of pruning method, pole saw type, slash removal, operator, pruning height and branch characteristics

ABSTRACT The objective of this study was to establish an operational model of work efficiency (net or productive work time per tree) for high-pruning of young silver birch depending on pruning method, pole saw type, operator, pruning height and branch characteristics. The final model included number of branches, cross-sectional area of the thickest branch at the cut, pruning height, pruning method (target or flush pruning) and operator as independent variables. Work time increased with increasing values of each of the three numeric variables. For a given pruning height the number of branches was for all practical purposes more influential than the size of the largest branch. Target pruning was significantly faster than flush pruning, all else being equal. The variation in work efficiency for the five operators in the study spanned a range almost twice as large as that attributed to pruning method. The mean work time for other activities during the pruning operation (supportive work time) was estimated at 17% of the productive work time for pruning.

The importance of harvest residue and fertiliser on productivity of Pinus patula across various sites in their first, second and third rotations, at Usutu Swaziland

BackgroundConcern is growing about the future of forestry productivity due to intensive nutrient removal, as a result of different harvesting operations. This study aimed to determine the effects on forest productivity when using different slash-retention scenarios with the recommended amounts of mineral fertiliser in Usutu forest. Usutu is a plantation forest that grows mostly softwood where the predominant species is Pinus patula Schiede ex Schltdl. & Cham.MethodsThe first trial series (F) comprised of one trial located in each of five forest blocks. It was established in 1971 and compared the effects of various site preparation scenarios (slash removal, slash retention and cultivation) on the early growth of Pinus patula for adjacent first (F1R) and second rotation (F2R) sites (i.e. grassveld and clearfelled first-rotation sites). The second (S) trial series was re-established in April 1991 on exactly the same position as the first trial series, and involved second (S2R) and third rotation (S3R) sites. Three main treatments, standard pitting through harvest residue (control); manual pitting after removal of harvest residue and forest floor (cleared); and manual pitting and broadcast application of dolomitic lime (2 t ha− 1) over the slash (lime), were undertaken in factorial combination with the application of phosphate and potassium fertiliser. The data reported here are for tree volume productivity across the five sites of the first trial series up to age 10 years and three of the five sites of the second trial series up to age 9 years.ResultsSlash removal decreased volume productivity by 9 and 13% in the F1R and F2R at 10 years of age and further by 21 and 33% in S2R and S3R, respectively at 9 years of age. However, fertiliser application increased volume productivity by 14 and 15% in the F1R and F2R at 10 years age and further by 18 and 10% in the S2R and S3R, respectively at 9 years of age.ConclusionsIn order to sustain or increase productivity, it is recommended that harvest residue slash should be conserved and fertiliser containing phosphate and potassium be applied at planting at Usutu.

Burning intensity and low light availability reduce resprouting ability and vigor of Buxus sempervirens L. after clearing

Thinning and prescribed burning are two common operations for reducing fuel accumulation and decreasing the intensity and severity of wildfires. However, the resprouting response of understory species may reduce the effectiveness of fuel load treatments and thus negatively affect the cost-benefit ratio of these treatments. This study focuses on Buxus sempervirens, a slow-growing, multi-stemmed tree species, frequently dominant in the understory of temperate European forests, which resprouts strongly after clearing or burning. The aim was to assess how light availability and burning influence resprouting ability (resprouting or not) and vigor (i.e. the growth of resprouts) after clearing B. sempervirens in thinned stands without slash removal (unburned) or with burning of slash residues (burned), two years after the treatments. All individuals studied resprouted shortly after clearing in unburned stands, whereas almost ca. 40% never resprouted in the burned stands. Fire intensity, measured at the base of 49 individuals, contributed to explaining the likelihood of mortality. The number of resprouts was directly influenced by the pre-treatment size of individuals, but this relationship was lower in burned stands. Fire intensity, recorded in 29 resprouted individuals, also influenced the number of resprouts. Post-treatment light availability, in addition to pre-treatment size, contributed to explaining the volume of the ten largest resprouts and the length of the largest resprout. No tradeoffs between the resprout number and the volume of the ten largest resprouts or the maximum resprout length were found. Our study suggests that burning after clearing reduces the resprouting ability of B. sempervirens. Moreover, avoiding affecting the canopy cover reduces its resprouting vigor and, consequently, increases the effectiveness of understory fuel load treatments.

EFFECT OF FUEL TREATMENTS ON CROWN FIRE BEHAVIOR IN ALEPPO PINE FORESTS OF GREECE: A SIMULATION STUDY

This study models the potential effect of various fuel treatments on crown fire behavior by using two crown fire simulation models in Aleppo pine (Pinus halepensis Mill.) stands. Fuel complex characteristics that influence fire behavior were measured in a representative Aleppo pine stand in northern Greece, using standard surface and canopy fuel inventory methods. Nine different fuel treatments (control, prescribed burning, controlled grazing, thinning without slash removal, thinning with slash removal, thinning and prescribed burning with slash removal, thinning and controlled grazing with slash removal, thinning and prescribed burning without slash removal, thinning and controlled grazing without slash removal) were simulated by adjusting surface fuels (total load, load-by-size class, depth) and canopy fuels (available canopy fuel load, canopy base height, canopy bulk density) under dry and normal fuel moisture conditions. Under normal conditions, stand thinning followed by prescribed burning and/or controlled grazing with slash removal prevented crown fire initiation in most cases. Under dry fuel moisture conditions, the simulation showed that the proposed fuel treatments did not appear to be effective in averting crown fire initiation and spread. Combinations of prescribed fire and/or controlled grazing can be used to reduce wildfire hazard in Aleppo pine forests. Management of Aleppo pine forests should include an analysis of how the proposed actions (logging, thinning, etc.) may affect fuel complex properties. Fuel treatment plans should be an essential component of forest management in Aleppo pine forests in Greece, in order to reduce fire hazard.

A survey of the Finnish mechanized tree-planting industry in 2013 and its success factors

The aim of the study was to update the information pertaining to mechanized tree-planting activity in Finland in 2013 and its success factors. All businesses providing a mechanized tree-planting service were interviewed and asked to describe their equipment and activities, identify critical success factors (CSFs), and suggest areas for improvement. In 2013, 31 planting machines (18 Bracke P11.a, 11 M-Planter and 2 Risutec) operated by 22 businesses planted approximately 4.7 million seedlings on 2663 hectares. CSFs included expertise of planting machine operators, high quality planting, adequate amount of work, stoniness, and removal of slash. Based on the survey, some recommendations for improving mechanized planting work can be made. Firstly, improving the cost-efficiency of mechanized planting is necessary to enhance businesses’ profitability. Secondly, worksite selection is crucial as stoniness, stumps and slash debris diminish productivity. Lastly, the popularity of mechanized planting in the future will benefit from more marketing. Many businesses were unwilling to increase the area of service, invest in new equipment, or increase the volume of planting work but they believed that mechanized planting will become more popular in the near future.

Response of the soil microbial community and soil nutrient bioavailability to biomass harvesting and reserve tree retention in northern Minnesota aspen-dominated forests

Intensive forest biomass harvesting, or the removal of harvesting slash (woody debris from tree branches and tops) for use as biofuel, has the potential to negatively affect the soil microbial community (SMC) due to loss of carbon and nutrient inputs from the slash, alteration of the soil microclimate, and increased nutrient leaching. These effects could result in lowered forest productivity and threaten the long-term sustainability of forest management. Retaining organic material post-harvest, including greater amounts of harvesting slash and live trees, within harvested areas may ameliorate some negative effects of biomass harvesting on soil processes. We evaluated the effects of biomass harvests with reserve tree and slash retention on the SMC and soil nutrient bioavailability (assessed using plant-root simulator probes) in trembling aspen (Populus tremuloides Michx.) forests in northern Minnesota during the spring and summer, 1–3 years after harvest. Variable biomass removal levels tested include complete removal (whole tree harvest of boles and branches), complete slash retention (bole only harvest), and 20% slash retention (amount suggested by regional biomass harvesting guidelines). Compared to the unharvested control, biomass harvests had no effect on the multivariate SMC composition or microbial biomass, but did result in a 1–4% increase in arbuscular mycorrhizal fungal abundance and reduced bacterial stress two and three years after harvest. Additionally, biomass harvesting increased NH4 bioavailability during year one, and reduced NO3 bioavailability during year two when compared to unharvested controls. Among the three biomass harvests with differing levels of slash removal there were few differences in overall SMC composition, microbial biomass, and soil nutrients; however, the abundance of arbuscular mycorrhizal fungi, gram positive and actinomycete bacteria were significantly higher in harvested treatments with more slash retained. These results are specific to single rotation biomass harvesting in aspen stands due to the unique relationships between plants and their associated SMCs, and may not be directly applicable to forest biomass harvesting of other commercial forest tree species, or multiple rotations.

Soil C and N storage and microbial biomass in US southern pine forests: Influence of forest management

Land management practices have strong potential to modify the biogeochemistry of forest soils, with implications for the long-term sustainability and productivity of forestlands. The Long-Term Soil Productivity (LTSP) program, a network of 62 sites across the USA and Canada, was initiated to address concerns over possible losses of soil productivity due to soil disturbance from forest management. Network sites employ an experimental design consisting of three harvest intensities (bole only, whole tree, whole tree+forest floor removal) in combination with three soil compaction intensities (none, intermediate, severe). Our purpose was to determine the impact of forest harvest intensity, soil compaction, and their interaction on soil organic carbon (SOC) and total nitrogen (TN) storage, and on soil microbial biomass C and N (MBC and MBN, respectively) in a Pinus taeda L. forest 15-years post-treatment at the Groveton LTSP site in eastern Texas, USA. Soils were sampled (0–10cm) five times during 2011–2012, and we quantified SOC and TN by dry combustion, and MBC and MBN by chloroform fumigation extraction. SOC and TN were both higher in the bole only treatment compared to the more severe harvest treatments; however, while TN was significantly impacted by harvest and varied seasonally, SOC varied only with season. MBC and MBN were impacted by harvest intensity and varied seasonally, and SMB-N had a harvest by time interaction. Generally, both microbial indices decreased in the order: bole only>whole tree>whole tree+forest floor. Temporal variations in MBN and TN were correlated with temperature. Soil compaction and the harvest intensity×soil compaction interaction had no effect on the measured soil properties. Since N limits tree growth in forest ecosystems, and because soil microbial biomass plays a key role in N mineralization, data suggest that harvest practices that minimize removal of litter and slash will favor soil N retention, maintain the size of the soil microbial biomass pool, and maximize the potential productivity of future rotations.

Soil carbon dynamics in aPinus massonianaplantation following clear-cutting and slash removal

Soil carbon dynamics in a<i>Pinus massoniana</i>plantation following clear-cutting and slash removal

Traditionally managed patch of Cladonia-Scots pine forest in the Biebrza valley – specifity of the protected forest community shaped by human activity

The path of Cladonia -Scots pine forest located on dune in Biebrza valley (NE Poland) was carefully studied in order to assess the influence of recently obsolescent selection cutting management on terrestrial lichen biota. Transect was located along the dune ridge crossing both lichen rich pine forests and other adjacent communities. Distinctive habitat patches were characterized by releve. Within the releve area measurements of cutting intensity and soil properties were carried out and soil samples were collected for laboratory analyses. It was found, that subsoil properties are rather similar on the whole dune, which indicates the main influence of management intensity on plant communities studied. All known development stages of Cladonio-Pinetum were observed. The characteristic lichen species preferred low organic horizon depth and low canopy closure. These factors are positively correlated with cutting intensity. The studied path was compared with other described patches of Cladonia -Scots pine in Poland and additional proposals of practices urgently needed to conserve these endangered habitat were given. In spite of already practiced slash removal, there are litter raking and complete cessation of clearcuts in favour of the selection cutting management are necessary for Cladonia -Scots pine forest conservation.

Hillslope erosion two and three years after wildfire, skyline salvage logging, and site preparation in southern Oregon, USA

Harvest of dead timber following wildfire is contentious because of a perception that the benefits are outweighed by environmental costs. One primary concern is the potential for increased erosion susceptibility associated with timber extraction (i.e. salvage logging) and site preparation. We measured erosion at the Timbered Rock Fire in southwestern Oregon on replicated sites that were either salvage logged on private land or non-salvage logged on adjacent public lands. Sediment was collected from silt fences placed in locations with relatively uniform hillslope surface conditions beginning in 2004 (2years post fire) for a period of two years. Mean erosion was 0.02 and 0.05Mgha−1yr−1 for 2004–05, and 0.04 and 0.14Mgha−1yr−1 for 2005–06, for non-salvage and salvage-logged areas, respectively. Vegetation cover was much lower in the salvage-logged areas (5–20%) than the non-salvage areas (70–80%), and was negatively correlated with erosion in the first year of measurement (r=−0.58, p=0.02). Increased erosion at salvage-logged plots is most likely associated with competing vegetation control and slash removal, but may have also been caused by some other management factor or preexisting condition that differed between measurement locations on private and public land. Increased erosion in the second year of measurement at all sites was associated with increased rainfall and storm frequency. Although control of competing vegetation may be critical for successful tree establishment following wildfire, our results suggest that site preparation techniques which inhibit growth of vegetation may contribute to increased hillslope erosion in high-risk areas, especially when increased rainfall and storms occur.

Improving productivity and sustainability of successive rotations of Acacia auriculiformis plantations in South Vietnam

We studied the productivity of Acacia auriculiformis plantations in South Vietnam over three successive rotations covering 15 years. The focus of our study was on the effects of inter-rotation management on stand growth and soil properties. Contrastin g slash and litter management treatments were applied at the start of the sec ond rotation, and reapplied at the start of the third rotation with an additional phosphorus fertiliser treatment. There were improvements in the genetics of planting stock, weed control and stocking with each rotation. Average growth rates (mean annual increment) increased from 10.6 m3 ha−1 y−1 in the first rotation (age 7 years) to 28.3 m3 ha−1 y−1 in the second rotation (age 6 years) and to 33.9 m3 ha−1 y−1 at age 5 years in the third rotation. Removal of slash and litter after harvesting the first rotation removed 20.2 Mg ha−1 biomass, containing 169.6, 13.9, 76.3 and 25.1 kg ha−1 of nitrogen (N), phosphorus (P), potassium and calcium, respectively, from the site. Greater amounts were removed after the second rotation commensurate with higher amounts of biomass produced. Slash and litter removal reduced growth of the second rotation by 13% compared to their retention. Soil organic carbon (C) in the 0–10 cm soil layer increased from 16.7 g kg−1 at the end of the first rotation to 22.8 g kg−1 at the end of the second rotation with a corresponding increase in soil N from 1.2 g kg−1 to 1.7 g kg−1. Over the same time, soil organic C and N contents were 26% and 40% greater, respectively, in treatments with slash and litter retained compared to initial levels before treatment application. In the second rotation, extractable soil P declined and in the third rotation there was a response to added P. Overall results demonstrate that there is an opportunity to increase and sustain production of A. auriculiformis over at least three rotations by integrated management practices promoting better stocking, planting of genetically improved stock, organic matter and nutrient conservation, and judicious weed management.

Effects of site preparation and slash management on growth and understory vegetation of Eucalyptus globulus plantations along a rotation time span in Portugal

The removal or maintenance of harvest residues in eucalypt plantations may influence site quality and productivity. Removal of slash from the site may facilitate further management operations and provide a valuable energy resource, but effects on site productivity and sustainability for a rotation time span were not yet assessed under Mediterranean conditions. Therefore, a study was carried out to assess the effects of slash (harvest residues plus forest floor litter) management and soil preparation options on stand productivity and understory vegetation dynamics, hypothesizing that those options influence tree growth, forest floor dynamics and understory biomass and diversity. An experiment was installed in West Central Portugal, consisting on: removal of slash without soil preparation (R); broadcast of harvest residues on the soil surface without soil disturbance (S); as in S, but concentrating the woody debris between tree rows (W); incorporation of slash into the soil by harrowing (I); removal of slash followed by harrowing (RH); and as in I followed by ripping (IS). The experiment was monitored for a rotation time span (140 months). Maintenance of slash followed by deep soil disturbance led to the highest wood production, but differences between treatments were not significant (p > 0.05). Forest floor load and understory biomass were also similar between treatments. Ground vegetation played an important role on nutrient cycling in early rotation stages, such effect being irrespective on slash management options. Incorporation of slash into the soil followed by ripping is probably the best option to match production and environmental sustainability of eucalypt plantations in Mediterranean conditions.

Productivity of successive rotations of Acacia mangium plantations in Sumatra, Indonesia: impacts of harvest and inter-rotation site management

The impacts of wood harvest, biomass removal and inter-rotation site management practices on productivity of Acacia mangium in South Sumatra were studied over 12 years across successive rotations. The productivity measured as MAI increased from 29.4 m3 ha−1 year−1 in the first to 48.0 m3 ha−1 year−1 in the second rotation. Whole tree harvesting (total stem, branches and leaves) caused a 21 % reduction in volume compared to harvesting merchantable wood alone in the next rotation. The rates of nutrients accumulation in trees were highest during the first year of growth, and declined from age 2 years. Significant amounts of nutrients were recycled through litter fall from 1 year after planting. Results highlight the importance of management which promotes nutrient supply on stand growth. Removal of slash and litter lowered soil pH, by about 0.1 unit. A small reduction was also found in soil organic carbon and nitrogen in the top soil during the first 3–4 years but values returned to pre-harvest levels by the end of the rotation. Extractable soil phosphorus and exchangeable cations decreased by the end of second rotation but these measures underestimate the nutrient pools available for A. mangium. These findings along with results from other studies have helped to implement operations which promote conservation of site resources for sustainable production in the region.

Influence of logging on the effects of wildfire in Siberia

The Russian boreal zone supports a huge terrestrial carbon pool. Moreover, it is a tremendous reservoir of wood products concentrated mainly in Siberia. The main natural disturbance in these forests is wildfire, which modifies the carbon budget and has potentially important climate feedbacks. In addition, both legal and illegal logging increase landscape complexity and affect burning conditions and fuel consumption. We investigated 100 individual sites with different histories of logging and fire on a total of 23 study areas in three different regions of Siberia to evaluate the impacts of fire and logging on fuel loads, carbon emissions, and tree regeneration in pine and larch forests. We found large variations of fire and logging effects among regions depending on growing conditions and type of logging activity. Logged areas in the Angara region had the highest surface and ground fuel loads (up to 135 t ha−1), mainly due to logging debris. This resulted in high carbon emissions where fires occurred on logged sites (up to 41 tC ha−1). The Shushenskoe/Minusinsk and Zabaikal regions are characterized by better slash removal and a smaller amount of carbon emitted to the atmosphere during fires. Illegal logging, which is widespread in the Zabaikal region, resulted in an increase in fire hazard and higher carbon emissions than legal logging. The highest fuel loads (on average 108 t ha−1) and carbon emissions (18–28 tC ha−1) in the Zabaikal region are on repeatedly burned unlogged sites where trees fell on the ground following the first fire event. Partial logging in the Shushenskoe/Minusinsk region has insufficient impact on stand density, tree mortality, and other forest conditions to substantially increase fire hazard or affect carbon stocks. Repeated fires on logged sites resulted in insufficient tree regeneration and transformation of forest to grasslands. We conclude that negative impacts of fire and logging on air quality, the carbon cycle, and ecosystem sustainability could be decreased by better slash removal in the Angara region, removal of trees killed by fire in the Zabaikal region, and tree planting after fires in drier conditions where natural regeneration is hampered by soil overheating and grass proliferation.