Container characteristics influence Pinus pinea seedling development in the nursery and field

The growth and development of Pinus pinea seedlings grown in different containers was followed through one growing season in the nursery and 3 years following outplanting in the field. The variables studied in the nursery were height, diameter, biomass of shoots and roots, nutrient uptake and root density. The measured field variables, height and diameter increment and survival, were correlated with the nursery variables. Container volume had the greatest influence on plant morphology. Containers with larger rooting volume had seedlings with larger height and diameter, greater nutrient content, and better field performance. Growing density was correlated with seedling morphology and nutrient concentration in the nursery. Among the variables that influenced container volume, the diameter of the container was the most important, while the depth of the container had a minor influence on seedling morphology.The best indicator of seedling development in the nursery was the ratio of container depth to container diameter, and the optimum ratio was 4. All containers produced seedlings with some root spiralling, including those containers with ribs. There was no relationship between either the number of spiralling roots or the angle of spiralling and container characteristics. Furthermore, root spiralling did not influence seedling performance following outplanting. Root density (root biomass/cm³) was inversely correlated with container volume but there was no correlation with either depth or growing density. The largest plants were produced with container volumes of 300–400 cm³, depth/diameter ratios of 4, and growing densities of 200–300 seedlings/m². These growing conditions will result in larger Pinus pinea seedlings coming out of the nursery, which will increase growth following outplanting.     

Quantifying economic losses from wildfires in black pine afforestations of northern Spain

We implemented a fire risk assessment framework that combines spatially-explicit burn probabilities, post-fire mortality models and public auction timber prices, to estimate expected economic losses from wildfires in 155 black pine stands covering about 450 ha in the Juslapeña Valley of central Navarra, northern Spain. A logit fire occurrence model was generated from observed historic fires to provide required fire ignition input data. Wildfire likelihood and intensity were estimated by modeling 50,000 fires with the minimum travel time algorithm (MTT) at 30 m resolution under 97^th percentile fire weather conditions. Post-fire tree mortality due to burning fire intensity at different successional stages ranged from 0.67% in the latest stages to 9.22% in the earliest. Stands showed a wide range of potential economic losses, and intermediate successional stage stands presented the highest values, with about 124 € ha^− 1 on average. A fire risk map of the target areas was provided for forest management and risk mitigation purposes at the individual stand level. The approach proposed in this work has a wide potential for decision support, policy making and risk mitigation in southern European commercial conifer forests where large wildfires are the main natural hazard.     

Short-term effects of fire on soil nitrogen availability in Mediterranean grasslands and shrublands growing in old fields

In three different plant communities growing in Mediterranean old fields we studied the short-term changes in soil nitrogen availability that occur after the fire. Two of these communities were grasslands with great capacity of resprouting and contrasted N availability, one dominated by Brachypodium retusum, and the second one dominated by B. retusum and the N fixing shrub Genista scorpius. The third community was an obligate seeder community (shrubland) with low N availability and was dominated by Rosmarinus officinalis. We selected six plots for each type of vegetation and therefore performed 18 experimental fires. During fires we measured temperatures at the soil surface. Maximum temperature recorded during fire and time–temperature integral were used as indexes of fire severity. During the 6 months following fires we measured Net N mineralization and plant uptake by field incubations using the resin-core technique in paired burnt and control plots.Fire severity increased with plant biomass. In grasslands heating of the soil surface increased with plant biomass up to a limit of 1 kg m⁻² of above-ground biomass. For high biomass a large proportion of heat released during fire was probably transmitted to the atmosphere or to the deeper soil horizons. The increase of soil mineral N was larger in fires of greater severity. Most mineral nitrogen released to the soil during fire was ammonia. Increases of ammonia post-fire depends on the temperatures measured on the soil surface while increases of the less volatile N form (nitrate) were related to the amount of burnt biomass and were highly dependent on the type of vegetation.The amount of nitrogen released to soil during fire represented a small proportion of the N mineralized during the 6 months following fire and thus the amount of nitrogen mineralized per unit of N released during fire was very different across the different types of vegetation. In grasslands fire induced changes in N mineralization decreased as fire severity increased. In contrast, in shrublands we observed the opposite trend. Differences in potentially mineralizable and in net mineralization N between unburnt grasslands and shrublands could account for this fact. Despite the depression in nitrification that we observed in grasslands between 40 and 80 days after the fire, high nitrate concentration in the soil during that period increased N leaching in burnt plots. No plant uptake was detected at that time. In grasslands the onset of plant uptake in burnt plots was delayed as compared to control. Cumulative changes in N did not depend on the burnt biomass in grassland communities, but it did in the seeder community. On the contrary, soil temperatures measured during fires related to changes in N observed in grasslands but not in the seeder community. It appears therefore, that post-fire N mineralization and leaching in grasslands may have been driven by the changes induced by heating the soil surface while in shrublands it may have been driven by the quantity of ash deposited on the soil surface.     

Wood volume yield and stand structure in Norway spruce understorey depending on birch shelterwood density

Wood volume yield and stand structure were investigated for Norway spruce understorey growing at 1500 trees ha⁻¹ under birch shelters of two different densities, 300 and 600 trees ha⁻¹, and Norway spruce growing without shelter, in a field trial in the boreal coniferous forest, 56 years after the establishment of the stand and 19 years after establishment of the trial.Wood volume yield in sheltered spruce (mean annual increments of 1.87 and 1.78 m³ ha⁻¹ year⁻¹ under the dense and sparse shelterwoods, respectively) was significantly lower than that of unsheltered spruce (mean annual increment 2.43 m³ ha⁻¹ year⁻¹). The loss in wood volume yield for sheltered spruce was more than compensated for by the additional wood volume yield in the shelterwoods (mean annual increments 3.26 and 1.88 m³ ha⁻¹ year⁻¹ for the dense and sparse shelterwood respectively).Shelterwood density did not produce any significant differences in inequality of the understorey stands, measured as skewness and the Gini coefficient for the wood volume distributions. This implies that two-sided competition for nutrients and water was more significant than competition for light.Immediately after trial establishment, trees in the no shelterwood treatment (i.e. where all overstory trees had been removed) showed a marked increase in diameter growth. Over time, the growth rate of unsheltered Norway spruce was reduced to a level comparable to that of sheltered spruce. The difference in average diameter has persisted during the trial period. There was no similar effect on height growth, resulting in an increased slenderness index (h/d) with increased shelterwood density for the understorey trees.     

Dead trees and protected polypores in unmanaged north-temperate forest stands of Lithuania

The availability of coarse woody debris (CWD) and distribution of dead trees into categories of mortality (dead standing, broken and uprooted) were investigated in north-temperate forests of central Europe (Lithuania). The studied area comprised 188.7 ha and included 18 different stands 40–130 years of age with a variety of tree species (spruce (Picea abies (L.) Karst.), pine (Pinus sylvestris L.), alder (Alnus glutinosa (L.) Gaertn.), birch (Betula pendula Roth and B. pubescens Ehrh.), aspen (Populus tremula L.), oak (Quercus robur L.), forest types (caricus-sphagnum, vaccinium-myrtillus, oxalis, myrtillus-oxalis, caricus-calamagrostis) and edaphic conditions (peaty, sandy, loamy soils of different moisture). The stands were excluded from wood harvesting for at least 30 years. A total of 11 365 dead trees (over 10 cm in DBH) or 6160.7 m³ of dead wood was found (60.2 trees/ha and 32.6 m³/ha). The volume of CWD per hectare was larger in older stands (r_S=0.78, P<0.01). Tree mortality during the last 2 years consisted of 482 trees and 381 m³, or 1.28 trees/ha×year and 1.01 m³/ha×year. In 25–33% of cases it was wind-related. Uprooted and broken trees were of larger DBH than dead standing. The distribution into the categories of mortality was strongly dependent on tree species (chi-square test, d.f.=10,P=0). Dead standing dominated in CWD of pine and alder. Broken trees comprised almost a half in CWD of aspen, and about one-third in birch, alder and oak. Uprooting most often occurred in spruce, aspen and birch. Edaphic conditions and stand age had a pronounced impact on distribution into mortality categories for spruce (chi-square test, d.f.=20, P<0.00001) and pine (d.f.=8, P≤0.0003). On peat soil, only a minority of trees of both pine and spruce was uprooted, and standing dead prevailed. In CWD of spruce and pine, the proportions of both dead standing and broken decreased and that of uprooted trees increased on mineral soils of higher moisture and bulk density in older stands. By contrast, uprooting in birch and alder occurred less often on more wet sites, where the proportions of standing snags were higher. A total of 41 species of wood-decomposing polypores were found in the study area. Among those, 10 (24%) were of conservation value.     

Leguminous seedling establishment in Tamaulipan thornscrub of northeastern Mexico

Due to extensive land clearing in northeastern Mexico, there is an increasing need for restoration for which knowledge on plant establishment biology becomes a priority, for restoration practices. In here we tested the influence of current environmental variation on the establishment biology of common woody species from Tamaulipan thornscrub. Seedling establishment was monitored; four native species (Acacia berlandieri Benth., Ebenopsis ebano (Benth.) Coult, Havardia pallens (Benth.) Brintton and Rose, Prosopis laevigata (Humb & Bonpl. ex. Wild.) M.C. Johston), and one exotic species (Leucaena leucocephala (Lam.) de Wit). Seedling emergence, seedling survivorship, length of stems and number of leaves were evaluated over 1 year in environments with different light regimes: (i) dense thornscrub; (ii) thornscrub edge; (iii) cleared thornscrub (direct sunlight). Ten plots of 4 m² (2 m × 2 m) were sampled in each environment. Seedling emergence occurred on spring and late summer and was greater on dense thornscrub for all species. Native species had higher survivorship and growth and had more leaves in dense thornscrub than in other environments. Exotic L. leucocephala had similar survivorship, shoot length and number of leaves across environments. All seedlings from all species died by late spring, possibly due to environmental stress. Seedling survival was longer for all native plants, as there were surviving seedlings in early spring for all species but not of exotic L. leucocephala. Perhaps mainly as a result of high temperature and low humidity. Additional watering, shading and moisture retaining gels should thus be considered when rehabilitation programs are made with seeds and seedlings in the region.     

Stand development and production dynamics of loblolly pine under a range of cultural treatments in north-central Florida USA

The objectives of this study were to examine the effects of stand development and soil nutrient supply on processes affecting the productivity of loblolly pine (Pinus taeda L.) over a period approximately equal to a pulpwood rotation (18 years). The experiment consisted of a 2×2 factorial combination of complete and sustained weed control and annual fertilization treatments (C: control treatment, F: fertilization, W: weed control, FW: combined fertilization and weed control), located on a Spodosol in north-central Florida, USA. The reduction of soil nutrient limitations through fertilization or control of competing vegetation resulted in dramatic increases in almost every measure of productivity investigated, including height (19.7 m in the FW treatment versus 12.5 m in the C treatment at age 18 years), basal area (FW=44.2 m² ha⁻¹, F=39.6 m² ha⁻¹, W=36.6 m² ha⁻¹, C=19.9 m² ha⁻¹ at age 16 years), stemwood biomass accumulation (114 Mg ha⁻¹ in FW versus 42.8 Mg ha⁻¹ in C at age 18 years), foliar nitrogen concentration (1.53% in plots receiving fertilization versus 1.06% in unfertilized plots at age 17 years) and leaf area index (age 16-year peak projected of approximately 3.3 at age 9–10 years in F and FW plots, 2.5 in the W treatment and 1.5 in the C plots). Cultural treatments also decreased the growth ring earlywood/latewood ratio, and accelerated the juvenile wood to mature wood transition. While soil nutrient supply was a major determinant of productivity, production changes that occurred within treatments over the course of stand development were equally dramatic. For example, between age 8 and 15 years, stemwood PAI in the FW treatment declined by 275%; similarly large reductions occurred in the F and W treatments over the same time period. The reductions in PAI in the treated plots were linearly related to stand BA, suggesting the decline in productivity was associated with the onset of inter-tree competition. Responses of stemwood PAI to re-fertilization treatments at age 15 years suggests that the declines in growth and growth efficiency with time were partially attributable to nutrient limitations.     

Fuels and fire behavior in chipped and unchipped plots: Implications for land management near the wildland/urban interface

Fire behavior was measured and modeled from eight 1 ha experimental plots located in the Francis Marion National Forest, South Carolina, during prescribed burns on February 12 and February 20, 2003. Four of the plots had been subjected to mechanical chipping during 2002 to remove woody understory growth and to reduce large downed woody debris from the aftermath of Hurricane Hugo in 1989. The remaining four (control) plots were left untreated. The burns were low intensity (mean flame length = 36.2 cm) and slow moving (mean spread rate = 1.18 m min⁻¹). Neither flame length nor rate of spread differed significantly between treatments (ANOVA F's < 0.5, P > 0.7, d.f. = 1,4). Post-burn observations provided somewhat more convincing evidence of treatment effects on fire behavior. According to transect data, only slightly more than half the area in the chip plots burned as compared to upwards of 80% in the burn-only plots. BehavePlus and Hough–Albini (HA) fire models correctly predicted the low intensity, slow moving fires given the observed wind and fuel moisture conditions. Accuracy of BehavePlus predictions depended on the value for fuel height entered in the model. Use of mean fuel height for the fuel depth parameter, as is typically recommended, somewhat overestimated fire hazard in the burn-only plots. However, limiting fuel height to the observed litter depth resulted in roughly accurate predictions. HA predictions for untreated fuels were close to correct even without adjusting fuel depth. When provided with two “high-risk” fuel and fire weather scenarios both models predicted more extreme fire behavior in the untreated fuels. In contrast, chipping appeared to protect against dangerous wildfires as long as fuel heights remained low. Smoke monitoring data from a companion study carried out in the same plots indicated a 60% reduction in smoke particulate production from chipped areas, roughly consistent with predictions of the fire effects model FOFEM. Mechanical chipping is apparently a useful method for limiting fire-hazard and smoke production in long-unburned fuels. However, questions remain concerning the long-term fate of heavy chip fuels and resultant effects on fire and smoke during severe drought.     

Developing general allometric relationships for regional estimates of carbon sequestration—an example using Eucalyptus pilularis from seven contrasting sites

General non-site-specific allometric relationships are required for the conversion of forest inventory measurements to regional scale estimates of forest carbon sequestration. To determine the most appropriate predictor variables to produce a general allometric relationship, we examined Eucalyptus pilularis aboveground biomass data from seven contrasting sites. Predictor variables included diameter at breast height (dbh), stem volume, dbh² × H, dbh × H and height (H). The data set contained 105 trees, ranging from 6 to over 20,000 kg tree⁻¹, with dbh ranging from 5 to 129 cm. We observed significant site differences in (1) partitioning of biomass between the stem, branch wood and foliage; (2) stem wood density and (3) relationship between dbh and height. For all predictor variables, site had a significant effect on the allometric relationships. Examination of the model residuals of the site-specific and general relationship indicated that using dbh alone as the predictor variable produced the most stable general relationship. Furthermore, the apparent site effect could be removed by the addition of a constant value to the measured diameter (dbh + 1), to account for the differing diameter distribution across the seven sites. Surprisingly, the inclusion of height as a second predictor variable decreased the performance of the general model. We have therefore demonstrated that for E. pilularis a general allometric relationship using dbh alone as the predictor variable can be as accurate as site-specific allometry, whilst being applicable to a wide range of environments, management regimes and ages. This simplifies regional estimates of aboveground biomass from inventory measurements, eliminating the need for site-specific allometric relationships or modifiers such as height, wood density or expansion factors.     

Impacts of atmospheric deposition on New Jersey pine barrens forest soils and communities of ectomycorrhizae

A gradient of increasing N deposition was identified in a southwestern to northeastern transect through the New Jersey pine barrens. The effect of this change in N deposition rate on soil chemistry and ectomycorrhizal morphotype community of pitch pine was studied by sampling from the field under mature pine trees, by planting bait seedlings into the field and in a greenhouse study where seedlings were given differential rates of N applications (0, 35, 140 kg ha⁻¹ equivalent). The field transect showed a significant but small increase in N deposition from 0.35 to 0.72 kg N ha⁻¹ (during the ca. 6 months of the study) equating to 7.84 ± 0.50 kg ha⁻¹ year⁻¹ at the northernmost site, 5.31 ± 0.70 at the middle and 3.66 ± 0.61 kg ha⁻¹ year⁻¹ N at the southwestern most site. Along this transect the ectomycorrhizal morphotype abundance and richness declined significantly under pitch pine. The decline in richness was significantly correlated with the N deposition rate. Bait pitch pine seedlings planted into one of the field sites and fertilized with increasing levels of N showed a reduction in ectomycorrhizal morphotype richness with increased N addition. In a greenhouse study, pine seedling biomass was inversely related to N addition. Nitrogen content of plants increased with increasing N supply, but P content of plants decreased, suggesting that P is a limiting nutrient in this ecosystem. Extractable N from the upper soil horizons increased in cores to which tree seedlings had been added as N addition increased. This indicates an approach to a critical loading of N for these oligotrophic soils, where N supply exceeds seedling N demand. In treeless cores N supply appears to exceed microbial immobilization potential even when no exogenous N is applied. As N supply to greenhouse seedlings increased, ectomycorrhizal morphotype richness declined. By combining data from the field and greenhouse studies, specific ectomycorrhizal morphotype groups were identified by their response to added N. Cortinarius- and Lactarius-like morphotypes were restricted to low levels of N availability. Suilloid- and Ascomycete-like morphotypes were more abundant as soil N availability increases, whereas Russula-like types showed an inverse relationship to N availability. We discuss the results from these oligotrophic sandy soils in comparison with European data derived from richer soils, where mycorrhizal fungal community responses appear to occur only at much higher levels of exogenous N. We attribute these differences to the evolved adaptations of pitch pine and their symbionts to growth in highly oligotrophic environments.     

Nutrient uptake and growth of young trees in a P-deficient soil: Tree species and phosphorus effects

Phosphorus deficiency is widespread in the subhumid highlands of eastern Africa but there are few data on the effect of P deficiency on the growth of agroforestry tree species. We studied the effect of P application on growth, nutrient uptake and dry matter partitioning in young trees of Calliandra calothyrsus, Cedrela serrulata, Eucalyptus grandis, Grevillea robusta, Markhamia lutea, Senna spectabilis, and Sesbania sesban on a P-deficient soil (Kandiudalfic Eutrudox, bicarbonate-EDTA extractable P = 1 mg kg⁻¹) in western Kenya. The trees were grown at two P levels (control and 500 kg added P ha⁻¹) at 1 m² spacing in a randomized complete block design with three replications. Leaf K concentrations were in the low range for all species (5–9 mg g⁻¹) and K deficiency may have limited responses to P. Averaged over species, P addition increased aboveground shoot dry matter by a factor of 2.6 at 62 and 124 days, but the response decreased to 1.3 at 325 days. The increases at 62 days were large in sesbania (5.4) and eucalyptus (3.2) but small in calliandra (1.4) and markhamia (1.1). Relative response to P was more strongly correlated with shoot growth rate per unit root length among species than with shoot growth rate alone. Calliandra, which had high early growth rate but low response to added P, had an exceptionally high root length (6.0 km m⁻²) compared with the other species (0.3–2.1 km m⁻²). P addition increased N and P content but decreased final shoot K content in sesbania and calliandra, and had little effect on K content in the other species. The high-yielding species (eucalyptus, sesbania and calliandra) accumulated more than 30 g N and 2 g P m⁻² in shoots in 325 days of growth. The proportion of total shoot N in wood (branch + stem) was in a higher range (67–75%) in the shrubby species (sesbania, calliandra, senna) than in the upperstorey tree species (38–43%). Slow early shoot growth relative to total root length, and high specific root length (root length per unit root mass) are proposed as criteria for the selection of species and provenances that are well adapted to P deficient soils.     

Carbon sources and sinks in high-elevation spruce–fir forests of the Southeastern US

This paper examines carbon (C) pools, fluxes, and net ecosystem balance for a high-elevation red spruce–Fraser fir forest [Picea rubens Sarg./Abies fraseri (Pursh.) Poir.] in the Great Smoky Mountains National Park (GSMNP), based on measurements in fifty-four 20 m × 20 m permanent plots located between 1525 and 1970 m elevation. Forest floor and mineral soil C was determined from destructive sampling of the O horizon and incremental soil cores (to a depth of 50 cm) in each plot. Overstory C pools and net C sequestration in live trees was estimated from periodic inventories between 1993 and 2003. The CO₂ release from standing and downed wood was based on biomass and C concentration estimates and published decomposition constants by decay class and species. Soil respiration was measured in situ between 2002 and 2004 in a subset of eight plots along an elevation gradient. Litterfall was collected from a total of 16 plots over a 2–5-year period.The forest contained on average 403 Mg C ha⁻¹, almost half of which stored belowground. Live trees, predominantly spruce, represented a large but highly variable C pool (mean: 126 Mg C ha⁻¹, CV = 39%); while dead wood (61 Mg C ha⁻¹), mostly fir, accounted for as much as 15% of total ecosystem C. The 10-year mean C sequestration in living trees was 2700 kg C ha⁻¹ year⁻¹, but increased from 2180 kg C ha⁻¹ year⁻¹ in 1993–1998 to 3110 kg C ha⁻¹ year⁻¹ in 1998–2003, especially at higher elevations. Dead wood also increased during that period, releasing on average 1600 kg C ha⁻¹ year⁻¹. Estimated net soil C efflux ranged between 1000 and 1450 kg C ha⁻¹ year⁻¹, depending on the calculation of total belowground C allocation. Based on current flux estimates, this old-growth system was close to C neutral.     

Logging activity and tree regeneration in an Amazonian forest

We studied the effect of experimental logging of 4 ha plots on the regeneration of tree species in a forest 90 km north of Manaus, Amazonas, Brazil. Logging resulted in a total reduction in live wood volume of 44–107 m³ ha⁻¹, although only 63% of this volume was felled, and only 43% removed from the plots. The density of established regeneration (trees and shrubs with diameter at breast height ≤10 cm, and height ≥200 cm) was greater in logged plots than in control plots when measured 3 and 7–8 years after logging. Species richness was also significantly higher in logged plots than in controls. We registered 139 species per 1000 stems, 7–8 years after logging, 143 species per 1000 stems, 3 years after logging, and 136 species per 1000 stems in control plots. Overall species composition was significantly affected by the intensity of logging damage in the plots after 7–8 years, and control plots were significantly different from plots logged 3 years previously. However, changes were not great in relation to natural variation within the forest. Most species increased in density after logging (mean=17%), and the number of individuals belonging to species with commercial value on the local market was 15% greater in logged plots than in control plots. The total potential value of the regeneration, based on the value of wood per m³ (when adult) of the individuals, was 23% higher in logged plots than in control plots, though this difference was not statistically significant. Therefore, enrichment planting is not necessary to maintain either the biodiversity, or potential economic value for wood production, of this forest.     

Genotypic variation in wood density and growth traits of poplar hybrids at four clonal trials

Wood density is considered as one of the most important wood properties which affects the properties and value of both fibrous and solid wood products. The present study was intended for evaluating the possibilities of improving wood quality and growth of poplar hybrids. Wood density components of individual growth rings (minimum and maximum wood density, average ring density) and growth traits (tree height, dbh, stem volume) were measured in four 10- and 12-year-old clonal trials of four poplar hybrids, Populus deltoides × P. nigra, P. trichocarpa × P. deltoides, P. maximowiczii × P. balsamifera, and P. balsamifera × P. nigra, as well as P. deltoides. Wood density components of individual growth rings were obtained from microdensitometeric profiles measured with a direct reading X-ray densitometer. Site had a moderately significant effect on wood density and a highly significant effect on tree growth. The hybrid effect was highly significant (P < 0.001) for most traits. Minimum, maximum and weighted wood densities were found to be under strong genetic control, with clonal repeatabilities varying between 0.45 and 0.81. The coefficient of genotypic variation (CV_G) for wood density at individual sites ranged from 4.0 to 6.8%, whereas CV_G for dry fiber weight (mass) reached 32.8% with repeatabilities of up to 0.67. A small but significant (P = 0.028) hybrid × environment interaction was found for dry fiber weight. The highest ecological sensitivity was found for P. deltoides × P. nigra, with ecovalence reaching 32.3%. Clonal × environment interaction was significant for weighted, average, and minimum wood density. Significant negative genotypic correlations between stem volume and wood density ranged from −0.39 to −0.74. One possible strategy in tree breeding would be to maximize wood fiber production through selection for dry fiber weight.     

Fuel mass and stand structure after post-fire logging of a severely burned ponderosa pine forest in northeastern Oregon

Stand structure and fuel mass were measured before and after a post-fire logging operation conducted 2 years after the 1996 Summit Wildfire (Malheur National Forest), in a ponderosa pine-dominated forest in northeastern Oregon. Variables were measured both pre- and post-logging in four replicate units for each of three treatments [un-logged control, commercial harvest (most dead merchantable trees removed), fuel reduction harvest (most dead merchantable trees removed plus most dead trees >10 cm diameter)]. Post-fire logging resulted in a significant decrease in mean basal area, down to 46% pre-treatment level in commercial units, and down to 25% in fuel reduction units. Logging significantly reduced tree density, especially for the smallest (<22 cm diameter) and intermediate (23–41 cm) diameter classes. Fuel reduction units also had significantly fewer snags (dead trees >30 cm diameter—4 ha⁻¹), compared to both commercial (23 ha⁻¹) units and to un-logged controls (64 ha⁻¹) in the year following timber harvest. Logging did not change ladder height or tree species composition (% ponderosa pine, Douglas-fir and grand fir). Total woody fuel mass increased significantly in fuel reduction units when compared to controls, with the greatest difference among treatments occurring in the slash fuel (<7.6 cm diameter) component (mean of 6.2 Mg/ha for fuel reduction stands versus 1.3 Mg/ha for un-logged stands). Logging activity caused no change in the mass of the forest floor (litter or duff). Model projections of the fuel bed using the fire and fuels extension of the forest vegetation simulator (FVS–FFE) indicate that the disparity in slash fuel mass between fuel reduction and un-logged units would be sustained until about 15 years post-logging, but a re-burn of moderate intensity occurring during this time would likely kill all young trees, even in un-logged units, because of the influence of other components of the fuel bed, such as grasses and shrubs. Model projections of 1000-h fuels (woody fuels >7.6 cm diameter) indicate that standing structure in all stands would collapse quickly, with the result that un-logged stands would contain two- or three-fold greater masses at 25 and 50 years post-logging, leading to much higher consumption rates of fuel in the event of a re-burn in the same place. Variation in dead tree fall and decay rates did not change the relationship among treatments in 1000-h fuel loads, but changed the time at which treatment differences were projected to disappear. Despite treatment differences in heavy fuel accumulations over time however, FVS–FFE predicts no differences among treatments in mortality of young trees due to either moderate or high intensity fire occurring in the same place at 25, 50, or 100 years post-fire logging. The lack of a re-burn effect is in part due to the reliance on flame length as the primary mechanism leading to tree death in the fire effect models used by FVS–FFE. If tree death turns out to be caused more by root burning or cambial heating, the observed variations in 1000-h fuel loadings among treatments could be significant in the event of a future re-burn.     

Can intensive management accelerate the restoration of Brazil's Atlantic forests?

Only 7% of the once extensive forest along the eastern coast of Brazil remains, and much of that is degraded and threatened by agricultural expansion and urbanization. We wondered if methods similar to those developed to establish fast-growing Eucalyptus plantations might also work to enhance survival and growth of rainforest species on degraded pastures composed of highly competitive C₄ grasses. An 8-factor experiment was laid out to contrast the value of different intensities of cultivation, application of fertilizer and weed control on the growth and survival of a mixture of 20 rainforest species planted at two densities: 3 m × 1 m, and 3 m × 2 m. Intensive management increased seedling survival from 90% to 98%, stemwood production and leaf area index (LAI) by ～4-fold, and stemwood production per unit of light absorbed by 30%. Annual growth in stem biomass was closely related to LAI alone (r² = 0.93, p < 0.0001), and the regression improved further in combination with canopy nitrogen content (r² = 0.99, p < 0.0001). Intensive management resulted in a nearly closed forest canopy in less than 4 years, and offers a practical means to establish functional forests on abandoned agricultural land.     

Stand development after different thinnings in two uneven-aged Picea abies forests in Sweden

Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3 × 2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25 ha. Volume increment was 0.5–6.8 m³ ha⁻¹ year⁻¹ for the plots, and significantly positively (p < 0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33 stems ha⁻¹ year⁻¹, with an average of 14 and 21 stems ha⁻¹ year⁻¹ at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p < 0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7 stems ha⁻¹ year⁻¹at the northern and southern site, respectively.     

A comparison of harvesting productivity and costs in thinning operations with and without midfield

Mechanised thinning operations can be carried out in the forest where skid roads are provided on which harvesters and forwarders can move. In the transition to continuous cover forestry (CCF) it is better to keep a thinner network of skid roads in the forest. Instead of tracks for harvesters and forwarders, these areas can be used for younger generations of trees. Moreover, fewer skid roads in the forest environment make the stand more natural. Fewer skid roads were introduced in this research as an alternative thinning operation with midfield¹ (MF) to the most popular mechanised thinning operation with skid roads² (SR). The aim of this paper is to analyse the productivity and economic aspects of thinning operations based on harvesters and forwarders, where there are different distances between skid roads. In both of the operations, harvesters and forwarders were used, but in the MF operation a chainsaw was additionally used to cut trees beyond the reach of the harvester boom. The distances between skid roads in the MF operation were 35–38 m, while in the other they were 18–20 m. The research was carried out in premature pine stands in a flat terrain in Poland. Bigger productivity and lower costs were found in the MF thinning operations. In the younger 44-year-old stand, the average harvester (Timberjack 770) productivity (in operational time) in the MF operation was 5.87 m³h⁻¹ and in the SR operation 4.52 m³h⁻¹; forwarding provided by the Vimek 606 6WD achieved a productivity of 5.03 and 4.52 m³h⁻¹, respectively. In the older 72-year-old stand, the Timberjack 1270B productivity was 11.53 m³h⁻¹ in MF and 8.70 m³h⁻¹ in SR; the Timberjack 1010B forwarder achieved 11.22 m³h⁻¹ (MF) and 8.84 m³h⁻¹(SR).The costs of harvesting and forwarding 1 m³ of wood were lower in the MF operations. In the younger stand, harvesting costs were 5.78 €/m³ (MF) and 6.72 €/m³ (SR) while forwarding costs were 1.94 and 2.18 €/m³ respectively. In the older stand, harvesting costs were 5.58 €/m³ (MF) and 6.78 €/m³ (SR); the forwarding costs were 2.65 €/m³ (MF) and 3.41 €/m³ (SR).     

A comprehensive analysis of teak plantation investment in Colombia

A financial assessment of forest investments is comprehensive if the analysis includes reliable yield estimates, land expectation value (LEV) and risk calculation. All of these aspects were considered and applied to teak plantations in Colombia, an emergent economy where high forest productivity, low opportunity cost of land, and decreased financial/economic risk have substantially contributed to promote forest investments. The von Bertalanffy non-linear mixed effect model was used to estimate forest yields using data collected from 31 permanent sample plots, measured over a 17 year period. A stochastic version of LEV along with other financial criteria was calculated by using a computer algorithm and Monte Carlo simulation. Finally, probabilities obtained from stochastic financial calculations were used in logistic models to estimate probabilities of success for a forest plantation project, a measure of risk assessment, after changing land prices. Results suggest that the potential forest productivity (i.e., the biological asymptote) ranges from 93 to 372 m³ ha^− 1. The mean annual increment is 27.8 m³ ha^− 1 year^− 1, which is attained 6 years after the forest plantation is established. Profitability analyses for teak plantations in Colombia suggest a LEV of US$7000 ha^− 1. The risk analyses indicate negligible financial risk for forestlands whose prices are lower than US$2000 ha^− 1.