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.     

Necromass in undisturbed and logged forests in the Brazilian Amazon

Necromass is an important stock of carbon in tropical forests. We estimated volume, density, and mass of fallen and standing necromass in undisturbed and selectively logged forests at Juruena, Mato Grosso, Brazil (10.48°S, 58.47°W). We also measured standing dead trees at the Tapajos National Forest, Para, Brazil (3.08°S, 54.94°W) complementing our earlier study there on fallen necromass. We compared forest that was selectively logged using reduced-impact logging methods and undisturbed forest. We estimated necromass density accounting for void volume for necromass greater than 10 cm diameter at Juruena for five decay classes that ranged from freshly fallen (class 1) to highly decayed material (class 5). Average necromass density adjusted for void space (±S.E.) was 0.71 (0.02), 0.69 (0.04), 0.60 (0.04), 0.59 (0.06), and 0.33 (0.05) Mg m⁻³ for classes 1 through 5, respectively. Small (2–5 cm) and medium (5–10 cm) size classes had densities of 0.52 (0.02) and 0.50 (0.04) Mg m⁻³, respectively. The average dry mass (±S.E.) of fallen necromass at Juruena was 44.9 (0.2) and 67.0 (10.1) Mg ha⁻¹ for duplicate undisturbed and reduced impact logging sites, respectively. Small and medium sized material together accounted for 12–21% of the total fallen necromass at Juruena. At Juruena, the average mass of standing dead was 5.3 (1.0) Mg ha⁻¹ for undisturbed forest and 8.8 (2.3) Mg ha⁻¹ for forest logged with reduced impact methods. At Tapajos, standing dead average mass was 7.7 (2.0) Mg ha⁻¹ for undisturbed forest and 12.9 (4.6) Mg ha⁻¹ for logged forest. The proportion of standing dead to total fallen necromass was 12–17%. Even with reduced impact harvest management, logged forests had approximately 50% more total necromass than undisturbed forests.     

Stand dynamics in a logged and silviculturally treated Costa Rican rain forest, 1988–1996

The lowland rain forests of Central America are poorly known from the standpoint of management for timber production. We studied the stand dynamics of a logged Costa Rican rain forest under three different regimes of post-logging silvicultural treatment. The site was located on low hills with Ultisols in Holdridge's Tropical Wet Forest life zone. The Pentaclethra macroloba-dominated forest had been high graded before planned management began. Management of the 540 × 540 m (29.2 ha) experimental area began with a timber harvest in the whole area during 1989–1990, 4 trees ha⁻¹ being cut overall for 10.1 m³ ha⁻¹. The experimental plots were 180 × 180 m (3.24 ha), comprising a 100 × 100 m (1.0 ha) central permanent sample plot (PSP) with a 40-m wide buffer strip. Two types of post-harvest silvicultural treatment: liberation/refinement (in 1991) and shelterwood (in 1992) were applied under a complete randomized block design with three replicates, using logged but untreated plots as controls. PSP data reported are for the 1988–1996 period for individuals with ≥10 cm DBH. The most marked changes in forest structure were caused by silvicultural treatment, basal area under the liberation/refinement treatment being reduced to ca. 65% of its probable mature forest value. Recruitment exceeded mortality in the years following intervention under all three treatments, but forest structural recovery was slowest under the liberation/refinement treatment. Post-intervention mortality rates appeared higher under the liberation/refinement treatment than under the control or shelterwood treatments, though differences were not statistically significant. In relation to tree attributes, mortality rates increased with decreasing DBH increment, crown illumination and quality of crown form. Commercial DBH increments were higher under the liberation/refinement treatment than in control plots during the 1993–1996 period. On the basis of its response to intervention during the first seven years of management, the forest appears resilient and productive; trends over time in mortality rates under the most intense silvicultural regime require close attention however. Pentaclethra-dominated forests are important components of the productive forest resources of Costa Rica and Nicaragua and, given current deforestation rates in areas such as southern Nicaragua, it is now urgent that the existing biophysical knowledge of these forests be applied to forest conservation and management.     

Initial impact of supervised logging and pre-logging climber cutting compared with conventional logging in a dipterocarp rainforest in Sabah,Malaysia

Pre-marked skid trails, directional felling and climber cutting when logging in tropical rainforests may be important ways of reducing damage to the forest, thus creating a healthier stand and improving future yields.This study, carried out in a virgin dipterocarp rainforest in the south of Sabah, Malaysia, compared two types of logging (both with and without pre-cutting climbers): conventional selective logging (CL) and supervised logging (SL). The latter is a selective logging system in which both pre-marked skid trails and directional felling were implemented. The pre-marked skid trails were aligned parallel to each other, spaced 62 m apart. A randomised complete block 2 × 2 factorial design was used in the experiment, consisting of 16 gross treatment plots, each of 5.76 ha with a 1 ha net plot in the centre.Fewer trees tended (0.050 < P ≤ 0.100) to be logged in SL plots than in CL plots (on average 9.4 and 13.0 trees ≥60 cm diameter breast height ha⁻¹). Pre-felling of climbers resulted in four more dipterocarp trees being logged ha⁻¹, compared with no climber cutting: a statistically significant difference (P ≤ 0.050). The basal areas lost of both large trees (≥ 60 cm dbh) and small dipterocarp trees (10–29 cm dbh) tended to differ between the logging systems, with CL leading to greater losses.There were significant differences in the residual stands left by the logging systems, with respect to the number of dipterocarps and their basal area in the diameter class 10–29 cm; ca 30% more stems being found after SL. No significant differences (or tendencies) in these variables were found in the residual stands in other diameter classes, or when trees of all species were considered.     

Harvesting intensity versus sustainability in Indonesia

In East Kalimantan (Indonesia), impacts of conventional (CNV) and reduced-impact logging (RIL) on forest ecosystems were compared on the basis of pre- and post-harvesting stand inventories. There was a positive and significant correlation between the proportion of trees damaged by felling and the density of trees felled. Logging intensity ranged from 1 to 17 trees ha⁻¹(9–247 m³ ha⁻¹) and averaged 9 trees ha⁻¹ (86.9 m³ ha⁻¹). The study has shown that with RIL techniques, logging damage on the original stand can be significantly reduced by 50% compared with conventional logging. However, this 50% reduction in logging damage, was dependent on the felling intensity. With a felling intensity of 8 stems ha⁻¹ or less, RIL techniques only damaged 25% of the original tree population whereas 48% were damaged with conventional techniques. Above this felling intensity (i.e. 8 stems ha⁻¹), the effectiveness of RIL in limiting forest damage was significantly reduced, mainly because of the increasing felling damage. Moreover, the removal of all harvestable timber trees, leaving only few potential crop trees, will result in a seriously depleted residual stand. Because of the high damage involved by high felling intensity, leaving few potential crop trees, and the yield capacity of the remaining stand, acceptable harvesting volume will not be reached within the felling rotation of 35 years. It is concluded that silvicultural system based on diameter limit alone, as is the Indonesian system (TPTI), cannot be compatible with sustainability and more sophisticated harvested-selection rules are needed.     

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.     

Diameter increment patterns among 106 tree species in a logged and silviculturally treated Costa Rican rain forest

Studies of growth rates of trees in managed neotropical forests have rarely employed complete botanical identification of all species, while published information for Central American lowland rain forests largely concerns forests free of recent disturbance. We studied diameter increments of trees in a managed Costa Rican rain forest. The Pentaclethra macroloba-dominated forest was located on low hills with Ultisols in Holdridge's Tropical Wet Forest life zone. The 540 m × 540 m (29.2 ha) experimental area was lightly logged during 1989–1990. The 180 m × 180 m (3.24 ha) experimental plots comprised a 100 m × 100 m (1.0 ha) central permanent sample plot (PSP) with a 40-m wide buffer strip. Post-harvest silvicultural treatments were liberation/refinement (in 1991) and shelterwood (in 1992), applied under a complete randomized block design with three replicates, using logged but untreated plots as controls. All live trees ≥10 cm DBH in the PSPs, were identified to species; data reported are for 1993–1996. Cluster analysis was used to group species on the basis of the median and quartiles of their diameter increment distributions, separating data by silvicultural treatments; five diameter increment groups were established and subdivided on the basis of the adult height of each species (four categories), giving 17 species groups in the final classification. Adult height and silvicultural treatment made a significant contribution to growth rate variation. Median annual increments of the slowest-growing species groups, which featured many under- and middle story species, were ca. 1 mm; those for the fastest growing species, which were mainly canopy and emergents, were ca. 16 mm. All species in the groups of very fast growth were pioneers, whether short or long-lived, though many other pioneer species did not show fast growth. The proportions of species found in groups of moderate, fast or very fast growth were greater in the silviculturally treated plots than in the controls, and one complete diameter increment group, of fast growth, was only represented in the treated plots. Crown form, crown illumination and presence of lianas in the crown, showed significant correlations with diameter increments, though the importance of these latter two variables varied with silvicultural treatment. The very fast growth groups differed from the others in having higher proportions of trees with well-formed, well-illuminated crowns and an irregular diameter distribution with relatively few individuals in the smallest DBH class. Comparison with data from other neotropical forest sites shows that long-lived pioneers such as Vochysia ferruginea and Jacaranda copaia grow fast or very fast at all sites, while non-commercial canopy and emergent species of Chrysobalanaceae and Sapotaceae appear to be uniformly slow-growing. Growth data for the majority of species are, however, published for the first time.     

Scenario analyses for the effects of harvesting intensity on development of forest resources,timber supply,carbon balance and biodiversity of Finnish forestry

We used national scenario analyses to examine the effects of harvesting intensity on the development of forest resources, timber supply, carbon balance, and biodiversity indicators of Finnish forestry in nine 10-year simulation periods (90-year simulation period) under the current climate. Data from the 11th National Forest Inventory of Finland were used to develop five even-flow harvesting scenarios for non-protected forests with the annual harvest ranging from 40 to 100 million m³. The results show that the highest annual even-flow harvest level, which did not decrease the growing stock volume over the 90-year simulation period, was 73 million m³. The total 90-year timber production, consisting of harvested volume and change in growing stock volume, was maximized when the annual harvest was 60 million m³. Volume increment increased for several decades when harvested volume was less than the current volume increment. The total carbon balance of forestry was the highest with low volume of harvested wood. Low harvested volume increased the values of biodiversity indicators, namely volume of deciduous trees, amount of deadwood and area of old forest.     

Canopy dynamics in unlogged and logged forest stands in the eastern Amazon

Selective logging of tropical forests damages residual trees and creates canopy openings throughout the stand. In the Amazon, reduced-impact logging results in significantly less damage than conventional unplanned logging; yet either logging method leads to substantial fragmentation of the forest canopy. Increased mortality rates of trees damaged in logging have been documented. In this paper, we investigate the effect of logging disturbance on treefall rates.Using repeat inventories of canopy trees (≥35 cm dbh) in six large (≥50-ha) forest stands at two sites in the eastern Amazon, we measured mortality rates in three treatment classes: unlogged, conventionally logged (CL) and logged using reduced-impact methods (RIL). At least 3000 trees were mapped and inventoried per stand prior to timber harvests. In the second inventory, 3 years after harvests in the logged stands, all trees were located and scored as living, standing dead, uprooted or broken.We found significantly higher overall mortality rates for trees in logged forest (both CL and RIL stands) than in adjacent unlogged forest. This effect was largely due to higher rates of treefall (i.e., stems uprooted or broken from natural causes). Moreover, significantly higher treefall rates were recorded for trees in logged forest that were not damaged in the logging than for trees in unlogged stands. Treefall rates were nearly twice as high in conventionally logged forest as in forest logged using reduced-impact methods. We found indirect support for the hypothesis that increased treefall rates in logged forest are related to increased canopy opening and fragmentation through analysis of the locations of fallen trees in relation to canopy disturbance.     

Effects of uneven-aged management on diameter distribution and species composition of northern hardwoods in Upper Michigan

Uneven-aged management using single-tree or group selection has been in practice for many decades, especially in northern hardwood forests. Use of stocking regulation tools is thought to produce and maintain specific stand structures that upon regulation, are sustainable over time. We evaluated stand structures in northern hardwoods in Upper Michigan across three ownerships that practice different approaches toward uneven-aged management. Industry land (MeadWestvaco—MWV) uses primarily diameter limit cutting combined with a sawyer-select harvest method, retaining a maximum diameter of 45.7 cm (18 in.) with a residual basal area of 16.1 m²/ha (70 ft²/ac) and a cutting cycle of 10 years. The Michigan Department of Natural Resources (DNR) uses a crop tree release technique with a residual basal area of 18.4 m²/ha (80 ft²/ac) and a cutting cycle of 20 years. Both ownerships view regeneration of new cohorts as inevitable given the intensity of disturbance and the forest type. The third ownership (the Ford Forestry Center School Forest at Michigan Technological University—FFC) employs strict stocking regulation using the BDq method (residual basal area of 16.1 m²/ha (70 ft²/ac), maximum diameter of 50.8–55.9 cm (20–22 in.), and a q-ratio of 1.3) with a cutting cycle ranging from 12 to 15 years.Stand structure on a total of 25 stands was characterized for these ownerships to assess the impact of management strategy on stand structure and species composition. Differences in species composition and lower diversity indices were found where increasing sugar maple dominance was an objective (FFC ownership). All ownerships showed reduced relative importance values of mid-tolerant species such as yellow birch in their stands as compared to values reported for old-growth or unmanaged stands. Diameter distributions were classified into one of three shape categories (negative exponential, increasing q-ratio, and rotated sigmoid) using the regression of DBH, DBH², and DBH³ on the log₁₀ of trees per hectare. The best model in terms of adjusted-R² and root mean square error (RMSE) was selected for each stand. All management strategies resulted in similar occurrences of distribution shapes, despite some evidence of a trend toward a rotated sigmoid distribution. These trends suggest that several different diameter distribution shapes in uneven-aged northern hardwoods in the Lake States are possible following a variety of management approaches, with sugar maple increasing in dominance with strict adherence to certain stocking regulation guidelines.     

Biomass,harvestable area,and forest structure estimated from commercial timber inventories and remotely sensed imagery in southern Amazonia

The purpose of this study was to determine if spatially-explicit commercial timber inventories (CTI) could be used in conjunction with satellite imagery to improve timber assessments and forest biomass estimates in Amazonia. As part of a CTI, all commercial trees ≥45 cm DBH were measured and georeferenced in 3500 ha of a logging concession in NW Mato Grosso, Brazil. A scientific inventory was conducted of all trees and palms ≥10 cm DBH in 11.1 ha of this area. A total of >20,000 trees were sampled for both inventories. To characterize vegetation radiance and topographic features, regional LANDSAT TM and ASTER images were obtained. Using a stream network derived from the ASTER-based 30 m digital elevation model (DEM), a procedure was developed to predict areas excluded from logging based on reduced impact logging (RIL) criteria. A topographic index (TI) computed from the DEM was used to identify areas with similar hydrologic regimes and to distinguish upland and lowland areas. Some timber species were associated with convergent landscape positions (i.e., higher TI values). There were significant differences in timber density and aboveground biomass (AGB) in upland (6.0 stems ha⁻¹, 33 Mg ha⁻¹) versus lowland (5.4 stems ha⁻¹, 29 Mg ha⁻¹) areas. Upland and lowland, and timber and non-timber areas could be distinguished through single and principal component analysis of LANDSAT bands. However, radiance differences between areas with and without commercial timber on a sub-hectare scale were small, indicating LANDSAT images would have limited utility for assessing commercial timber distribution at this scale. Assuming a 50 m stream buffer, areas protected from logging ranged from 7% (third order streams and above) to 28% (first order and above) of the total area. There was a strong positive relationship between AGB based on the scientific inventory of all trees and from the commercial timber, indicating that the CTI could be used in conjunction with limited additional sampling to predict total AGB (276 Mg ha⁻¹). The methods developed in this study could be useful for facilitating commercial inventory practices, understanding the relationship of tree species distribution to landscape features, and improving the novel use of CTIs to estimate AGB.     

Riparian vegetation in the southern Appalachian mountains (USA) following chestnut blight

American chestnut is often listed as an important component of mesic midslopes and xeric ridges in pre-blight southern Appalachian forests, but its former importance in riparian forests has generally been considered minor. To document its importance in riparian forests, 589 American chestnut stumps were located on four sites (two previously logged, two unlogged) in the Blue Ridge physiographic province of the southern Appalachians. Diameters and basal areas of chestnut were calculated and compared among sites and to basal area (BA) of live trees. Chestnut BA ranged between 8.4 and 12.4 m²/ha (25 and 40% of current BA). Vegetative composition on 58 random plots suggests that three community types were represented on the four study sites: (1) old-growth forest with sparse rhododendron; (2) logged forest with sparse rhododendron; and (3) forest dominated by rhododendron which controlled vegetative composition regardless of logging status. Thickets of ericaceous shrubs that developed after the blight were significantly denser in logged forest than in old-growth. Only shade-tolerant herbs such as galax and partridge-berry, as well as a rare orchid, Appalachian twayblade, were found growing in rhododendron thickets. Results of our study suggest that the gap-phase hypothesis, where species diversity is maintained in cove forests of the southern Appalachians through gap-phase disturbance, should be modified to allow for dynamics influenced by rhododendron. The reintroduction of periodic fire into southern Appalachian riparian habitat may control rhododendron dominance and improve tree regeneration.     

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.     

Harvesting intensity affects forest structure and composition in an upland Amazonian forest

Forest structure and floristic composition were studied in a series of 0.5 ha natural forest plots at four sites near Porto Trombetas in Pará State, Brazil, 11–12 years after being subjected to differing levels of above-ground biomass harvest and removal. In addition to undisturbed control plots, experimental treatments included: removal of most trees ≥45 cm DBH (low intensity harvest); removal of trees <20 and ≥60 cm DBH (moderate intensity harvest); clear-cutting (100% above-ground biomass removal). Post-harvest basal area growth generally increased with harvest intensity, and total basal areas for trees ≥5 cm DBH were, at the time of our study, 60% (in the clear-cut) to about 80% of those in the control plots. Biomass harvests stimulated recruitment and growth of residual trees, particularly in the smaller diameter classes, but had little effect on species richness for small trees, seedlings, vine, herbs, and grasses. Species richness for trees ≥15 cm DBH was greater in the control and low-intensity (74–75 species) than in the moderate intensity (47 species) and clear-cut (26 species) treatment plots. While the tree flora within all harvest treatments was broadly similar to the undisturbed (control) plots and included similar numbers of species of the major plant families typical of the surrounding forests, the more intensive harvest treatments, especially the clear-cut, were dominated by a higher proportion of short-lived, early successional tree species.     

Influence of individual reserve trees on nearby reproduction in two-aged Appalachian hardwood stands

In the 1970s, public opposition to clearcut harvesting in hardwood forests of the eastern United States led forest managers and scientists to consider alternative practices that retain a low-density overstory forest cover. From 1979 to 1984, a form of clearcut-with-reserves harvesting was applied in 80-year-old Appalachian mixed-hardwoods to create four experimental stands with two-aged structures. The residual stand basal area averaged 5.3 m²/ha, comprising an average of 36 reserve trees/ha. The reserve trees were evenly distributed throughout the stand, initially with considerable space between their crowns, thus providing the sunlight and seedbed conditions needed to recruit desirable shade-intolerant reproduction after harvest. This study examined the response of the 100-year-old reserve trees and the development of the 20-year-old natural reproduction located in their immediate vicinity.Diameter at breast height (Dbh), height, and relative position were recorded for all reproduction ≥2.5 cm within transects adjacent to northern red oak (Quercus rubra L.) and yellow-poplar (Liriodendron tulipifera L.) reserve trees. Each transect was divided into five zones, which represented positions relative to the reserve tree crown edge, and basal area was computed for each of three shade tolerance classes within each zone. A repeated measures ANOVA was used to compare basal area of reproduction by tolerance classes and zone. In general, basal area of reproduction, particularly that of shade-intolerant species, increased with distance from the reserve tree. Regression analyses also indicated that dbh and height of reproduction was positively related to distance from the reserve trees. Although height growth of reserve trees was similar for both species, northern red oak exhibited significantly greater dbh and crown radial growth than yellow-poplar.The results indicated that reserve trees influence the growth rate and species composition of reproduction in their immediate vicinity. Basal area of reproduction increased from 10.1 to 17.7 m²/ha with increasing distance from the reserve trees. Basal area of intolerant species more than doubled along the same gradient. Basal area of reproduction in the two-age stands was 30–40% less than that observed in even-aged stands on similar growing sites, but the reduction was offset by growth of the reserve trees. The surface area covered by the reserve tree crowns increased approximately 88% for northern red oak and 44% for yellow-poplar. Since the sphere of influence of reserve trees increases over time, forest managers must consider their long-term impact on reproduction when prescribing clearcut-with-reserves harvests and other practices that involve retaining trees for many years.     

Life cycle inventories of roundwood production in northern Wisconsin: Inputs into an industrial forest carbon budget

Carbon budgets are developed to understand ecosystem dynamics and are increasingly being used to develop global change policy. Traditionally, forest carbon budgets have focused on the biological carbon cycle; however, it is important to include the industrial forest carbon cycle as well. The overall objective of this study was to quantify the major carbon fluxes associated with the production of Wisconsin's industrial roundwood, by using life cycle inventory (LCI) methodology to produce an industrial forest carbon budget. To achieve this objective we (1) developed carbon LCIs for the harvest process for three major forest ownerships (state, national, and private non-industrial), (2) developed carbon LCIs for a dimensional lumber and two oriented strand board (OSB) mills and (3) completed a scaled version of 1 and 2 to include more Wisconsin forestlands and to incorporate the other major processes within the industrial forest carbon cycle (e.g. primary mill, secondary mill, product use and product disposal processes of the industrial forest carbon cycle). The carbon budgets for the harvesting process of the Chequamegon-Nicolet National Forest (CNNF), the Northern Highland American Legion State Forest (NHAL), and the non-industrial private forests that participated in the managed forest laws of Wisconsin (MFL-NIPF) were 0.10, 0.18 and 0.11 tonnes C ha⁻¹ year⁻¹), respectively. The dimensional lumber and OSB products were both net carbon sources, and released 0.05–0.09 tonnes C/tonnes C processed). More carbon is sequestered than released within the industrial forest carbon cycle of Wisconsin's national (6 g C m⁻² year⁻¹), state (12 g C m⁻² year⁻¹) and non-industrial private forests (7 g C m⁻² year⁻¹). Using published net ecosystem production data we estimate that the net forest carbon cycle budget (sum of the biological and industrial C cycle, [Gower, S.T., 2003. Patterns and mechanisms of the forest carbon cycle. Ann. Rev. Environ. Resour. 28, 169–204]) for the CNNF ranges between −897 and 348 g C m⁻² year⁻¹. Life cycle inventories of wood and paper products should be clear and explicitly state what processes are included, so that results can be used by policy makers and future researchers.     

Long-term growth and ecophysiological responses of a southeastern Oklahoma loblolly pine plantation to early rotation thinning

A thinning levels study was initiated in a 9-year-old loblolly pine (Pinus taeda L.) plantation containing 26.6 m² ha⁻¹ basal area during the spring of 1984 in southeastern Oklahoma. Thinning treatments consisted of (1) three control plots (BA100), (2) three plots thinned to approximately 50% of the original basal area (BA50) and (3) three plots that were thinned to 25% of the original basal area (BA25). In 1987 the BA50 and BA25 plots were both rethinned to a basal area of 12 m² ha⁻¹. No other thinnings were done through age 24.The control plots have attained a basal area of 45.3 m² ha⁻¹ and basal area is now starting to decline. The BA25 and BA50 plots have basal areas between 34 and 35 m² ha⁻¹. Mortality has averaged about 90 trees ha⁻¹ per year from age 10 to age 24 on the control plot, declining from 2078 trees ha⁻¹ at age 10 to 827 trees ha⁻¹ at age 24. Mortality losses in the BA25 and BA50 plots have been only 3.2–7.7 trees ha⁻¹ per year over the entire study period. Cumulative stem biomass lost to mortality was 10.5, 16.0 and 61 Mg ha⁻¹, respectively, for the BA25, BA50 and BA100 treatments. Cumulative standing live biomass at age 24 in the BA100 treatment is 132 Mg ha⁻¹. Cumulative standing live biomass in the BA25 and BA50 treatments at age 24 is 86 and 79%, respectively, of that observed in the BA100 treatment. These results suggest wide ranges of residual stand densities left after an early thinning will produce a high percentage of the potential total maximum standing stem biomass. Diameter distributions at age 24 show only 33% of the trees in the BA100 treatments have the dimensions to be sawtimber (≥30 cm) but 92 and 95% of the trees in the BA25 and BA50, respectively, are sawtimber dimension or larger. Mean annual stem biomass production (MAI) of the BA100 treatment is 7.5 Mg ha⁻¹ per year at age 24. MAI of the thinned treatments is about 5.1 Mg ha⁻¹ per year and is converging to that of the BA100 treatment. The basis for this convergence is not that the live trees in the BA100 treatment are producing live biomass less rapidly than the thinned plots, but that mortality losses in the BA100 plot are much higher. Current annual stemwood production in all treatments is often limited by the severe summer droughts that occur in this region. The wide variations in weather experienced at this site also result in variations in earlywood:latewood ratio and ring specific gravity.     

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).     

Nitrate concentrations in soil solutions below Danish forests

Nitrate in the soil water below the root zone is a pre-condition for nitrate leaching, and it indicates loss of nutrients from the forest ecosystem. Nitrate leaching may potentially cause eutrophication of surface water and contamination of ground water. In order to evaluate the extent of nitrate leaching in relation to land-use, a national monitoring programme has established sampling routines in a 7×7 km grid including 111 points in forests. During winters of 1986–1993, soil samples were obtained from a depth of 0–25, 25–50, 50–75 and 75–100 cm. Nitrate concentrations in soil solutions were determined by means of a 1 M KCl extraction. The influence of forest size, forest-type, soil-type, tree species and sampling time on the nitrate concentrations was analysed in a statistical model. The analysis focused on data from depth 75–100 cm, as nitrate is considered potentially lost from the ecosystem at this depth. The range of nitrate concentrations was 0–141 mg NO⁻₃–N dm⁻³ and the estimated mean value was 1.51 mg NO⁻₃–N dm⁻³. The concentration was influenced by (1) forest size (concentrations in forests <10 ha were higher than concentrations in forests >50 ha), (2) forest-type (afforested arable land had higher concentrations than forest-type `other woodland'), (3) soil-type (humus soils showed above average concentrations, and fine textured soils had higher concentrations than coarse textured soils), and (4) sampling time. Unlike other investigations, there was no significant effect of tree species. A few sites deviated radically from the general pattern of low concentrations. The elevated concentrations recorded there were probably caused by high levels of N deposition due to emission from local sources or temporal disruptions of the N cycle. The nitrate concentration in the soil solution below the root zone was mostly rather low, indicating that, generally, N saturation has not yet occurred in Danish forest ecosystems. However, median concentrations exceeding drinking water standards (11.3 mg NO⁻₃–N dm⁻³) were found at 7% of the sites. Furthermore, 30% of the sites had median concentrations above 2 mg NO⁻₃–N dm⁻³, suggested as an elevated level for Danish forest ecosystems, equalling annual N losses of more than 2–6 kg ha⁻¹ year⁻¹.     

Modelling coarse woody debris dynamics in even-aged Scots pine forests

Coarse woody debris (CWD) has become an important component in the study of forest ecosystems, being a key factor in the nutrient cycle as well as a habitat for many species. CWD dynamics varies greatly from primeval to managed forests. To assess the CWD dynamics, a chronosequence trial was established in two Scots pine forests in the Central mountain range in Spain. Although, the shelterwood system has been applied in both forests, one has received more intensive silviculture, whereas in the other, regeneration has been much more gradual and the thinning regime has not been so intensive. In order to inventory CWD, five decay classes and four categories according to size and CWD type (stumps and fallen logs or branches) were defined. The volume of branches and logs (estimated from length and mean diameter) and the number of stumps by size class and decay class are used to characterise the CWD. The most notable differences between the two silvicultural systems can be appreciated in the graph as peaks for temporary distribution of larger logs and stumps when intensive silviculture is applied. The CWD observed in the forests studied is mainly produced by logging. The maximum volume of logs and branches above 5 cm in diameter is 43.25 m³/ha after regeneration felling in the first forest, whereas in the other, a maximum of 16.30 m³/ha is reached at 60 years, just after thinning. Large stumps (diameter equal or greater than 30 cm) make up an important part of CWD biomass in these forests just after the regeneration felling. A model was developed to predict the changes in CWD quantity and quality distribution over time as well as predicting the effect of different silviculture options on CWD dynamics. The model integrates two different processes: the CWD inputs (which may be continuous or instant), and the decay process, modelled through a Richards–Chapman function. The average lifetime of CWD obtained ranges from 30 years for stumps over 30 cm in diameter to 8 years for logs with a diameter less than 10 cm.