Intensive Silvicultural Treatments Research Articles

Efficient use of timber resources in Mexico: Historical development and current challenges

The use and consumption of wood has always captured the attention of forest researchers, mainly from the point of view of forest management and the sustainable processing of raw materials. For this reason, the wood industry has not only been concerned with the maintenance of forests, but also with efficient processing. The objective was to identify, analyse and discuss the main elements that influence the efficient use of natural timber resources at a global, regional and local level, providing a historical and current perspective of the industrial forestry sector in Mexico. Historically, the wood industries worldwide have been concerned with applying intensive silvicultural treatments in native and artificial forest stands, in search of satisfying the demand of a growing market. In this context, industries evolved as processes needed to be more efficient. Therefore, efforts were made to reduce and take advantage of forest residues, at the same time various historical events generated additional needs. At present, the integration of silviculture and forest transformation allow to increase and improve the quality of the products generated. Through the application of intensive silvicultural treatments, products of a single species are obtained. However, it is possible to direct production to a specific market as the forest mass develops. For its part, selective treatments in uneven-aged forests maintain a constant production of diverse products for different specialized markets. In Mexico, it is imperative to analyse and generate innovative or competitive products derived from wood to improve the efficiency of forest harvesting.

Production, tree size inequality and growth dominance in loblolly pine plantations under different silvicultural management regimes

Understanding stand structure and growth relationships and how they are influenced by silvicultural treatments can help us optimize forest management regimes. With two large long-term silvicultural research experiments in loblolly pine plantations, we examined the effects of planting density, silvicultural intensity (sustained competition control and repeated fertilization), and thinning treatments on temporal patterns of stand biomass, biomass growth, tree size inequality, growth dominance, and on stand growth-structure relationships. Results showed that more intensive silvicultural treatments decreased tree size inequality but increased growth dominance, while higher planting densities increased both tree size inequality and growth dominance in unthinned plots. Growth dominance increased from negative to positive with age. For a given silviculture and planting density, tree size inequality became stable after 15 years while growth dominance continued to change over time. Thinning treatments decreased both tree size inequality and growth dominance, and there were no effects of silviculture and planting density in thinned stands. Stand biomass growth was negatively related to tree size inequality and positively related to growth dominance, after accounting for the effects of silvicultural treatment and planting density.

Site quality and intensive early stand management practices affect growth dominance, structural complexity, and tree growth in ponderosa pine plantations

During stand initiation, the influences of silvicultural practices such as competing vegetation control and fertilization have been primarily examined in terms of stand-level growth rather than structural complexity. Understanding how intensive silvicultural treatments alter the long-term trajectory of stand development may be critical to meeting management objectives, such as habitat restoration, minimizing ladder fuels, or carbon sequestration. Previous studies have found mixed evidence for an effect of vegetation control and fertilization on structural complexity. Investigating how early pulse treatments drive tree size differentiation in young stands, as indicated by growth dominance (GD), could potentially allow managers to anticipate or design treatments to alter the development of structural complexity later in stand development. We reanalyzed data from the Garden of Eden experiment, a full-factorial study investigating how competing vegetation and nutrients impact ponderosa pine growth and yield over a gradient of site quality in northern California, USA. Our goals were to determine whether these silvicultural practices alter GD and structural complexity, and whether GD and structural complexity created potential feedbacks to alter stand productivity. We examined data for the first 20 years of stand development across 6 study sites. For each site and observation period, we calculated the growth dominance coefficient of total cubic volume to represent GD and the Gini coefficient of inequality in basal area distribution (GC) to represent structural complexity. We created a series of competing generalized additive mixed models (GAMMs) to disentangle the roles of site, stand age, and treatment on GD and GC. We created a set of competing individual-tree GAMMs at age 20 to isolate the influences of GC and GD on volume increment, controlling for the effects of competition, tree size, site, and treatment influences. In agreement with previous research, we found that GD deviated little from size-symmetry (tree growth being roughly proportional to tree size) and did not vary consistently with treatment. Competing vegetation control and higher site quality promoted lower GC, indicative of lower structural complexity. Fertilization increased structural complexity relative to other treatments on two sites in particular, which may reflect unintentional increases in drought stress from fertilization on sites with metasedimentary soils. While GD had limited influence on individual-tree growth, GC interacted with tree size such that small-medium sized trees grew more rapidly on structurally simple plots. Our results have implications for balancing objectives such as fire risk, carbon sequestration, and habitat during reforestation projects.

Effects of intensive fertilization, complete competition control and site quality on aboveground net primary production (ANPP) dynamics of loblolly pine plantations

Changes in aboveground net primary production (ANPP) are relevant to forest management, ecosystem ecology and carbon budget. It is believed that ANPP reaches a maximum in young forest stands and then gradually declines as stands age. Intensive silvicultural treatments such as competing vegetation control and fertilization have been widely used in pine plantations in the southern US and have shown large early growth gains. The effects of site quality and silvicultural treatments on long-term patterns of ANPP in pine plantations remain to be studied. These effects were rigorously tested by examining their effects on the parameters of an ANPP-age model for loblolly pine, using 33-year data from a large field experiment containing a factorial arrangement of complete competition control (H) and intensive fertilization (annually until age 12 years and then biennially until age 28 years). Site quality and silvicultural treatments significantly affect the magnitude and timing of maximum ANPP; silvicultural treatments substantially alter the pattern of ANPP-age relationship, but site quality does not. Under better site conditions loblolly pine stands will reach a greater maximum ANPP at earlier ages. Non-fertilized stands achieve a smaller maximum ANPP and thereafter have no obvious decline in ANPP, while ANPP in intensively fertilized stands quickly reach a greater maximum and then sharply decline to a lower level than that of the non-fertilization stands. The early repeated fertilization enhances growth rates in young stands, but continuous application of fertilization at mid- or late-rotation reduces growth rates in older stands. Our results showed that nutrient limitations are not responsible for age-related declines in ANPP for loblolly pine plantations in the southern US.

Productivity gains from weed control and fertilization of short-rotation Eucalyptus plantations in the Venezuelan Western Llanos

Increasing forest site productivity is a need. Land use conflicts, high land prices, or owners’ objectives, have motivated forest managers to apply more intensive silvicultural treatments to increase forest site productivity. Understanding how intensive silvicultural practices such as weed control and fertilization + weed control affect productivity will permit managers to select the best treatment to increase it. Our objectives were: (1) to estimate the gap between current and attainable productivity of Eucalyptus plantations and (2) to determine the effect of treatment on light use and light use efficiency. To estimate the gap between current and attainable productivity, we established 53 pairs of plots, which were measured for two years. Each pair consisted of a control plot, which received the management regime that is regularly applied to the stands, and a treated plot, which received intensive silvicultural treatment (fertilization + weed control) in addition to the operational management applied to the control plots. At 25% of the sites, a third plot (weed control only) was established. Stem biomass growth in the control and treated plots was 12.4 and 14.8 Mg ha−1 yr−1, respectively. We found significant differences in light use between the control and treated plots, i.e., averages of 1344 MJ m−2 yr−1 and 1406 MJ m−2 yr−1, respectively, representing a 4.6% increase. The increase in light use efficiency (LUE) was higher and reached 20%. On average, the control plots had a LUE of 0.9 g of dry mass (DM)/MJ compared with 1.10 g DM/MJ for the treated plots. There is a considerable opportunity to increase forest productivity through fertilization, and it may be possible to obtain greater gains than those observed in this study. This information is important to estimate the expected responses to intensive silviculture and will help to decide where silvicultural treatments should be applied to maximize the gains obtained from the investment.

Crown physiological responses of loblolly pine clones and families to silvicultural intensity: Assessing the effect of crown ideotype

Clonal forestry must be linked with intensive silvicultural practices to increase forest productivity of loblolly pine (Pinus taeda L.) in the southern United States. Although the positive growth responses due to intensive silviculture have been reported extensively, much less is known about the physiological processes that drive these responses. This study assessed the responses of growth, leaf area, leaf-level gas exchange and foliage morphology of 4year-old loblolly pine clones and families to changes in silvicultural intensity on the Virginia Piedmont (VA) and North Carolina Coastal Plain (NC). Four clones (differing in crown ideotype), 1 control-mass-pollinated (CMP) and 1 open-pollinated (OP) family were evaluated in two levels of silviculture (operational and intensive). The operational silvicultural treatment included only banded weed control, whereas the operational silvicultural treatment included broadcast weed control, fertilization and tip moth control. The effect of genotype and silvicultural intensity were site-specific, and expressed mostly at VA. The intensive silvicultural treatment increased stem volume by 68% and 36% relative to the operational silvicultural treatment at VA and NC, respectively. At VA, the differences in the leaf area responses to the silvicultural treatment among genotypes differed between 60 and 146%, which suggested great differences in growth efficiency among the genotypes. These responses were not linked to changes in leaf physiology and morphology. The seasonal variation of gas exchange parameters was similar between sites, but significant differences in leaf physiology and morphology were found among the genotypes. However, this variation was neither attributed to the genetic source (clonal versus non-clonal) nor the crown ideotype (broad- versus narrow-crown) as hypothesized. Understanding the differences in the crown physiological processes among loblolly pine genotypes may be required to optimize the gains expected from clonal forestry.

Dynamics of ecosystem services in Pinus sylvestris stands under different managements and site quality classes

Timber and biodiversity are considered two antagonistic ecosystem services (ES), largely influenced by silviculture and site ecological conditions. In order to address the trade-offs between these two ES over time, we performed a retrospective study at compartment level in the Pinus sylvestris forests of the Spanish Central Mountain System. Archival data from Management Plans for eight forests with contrasting silvicultural systems (uniform shelterwood system, group shelterwood system, irregular shelterwood system,) and three different site quality classes were analysed. Timber production was assessed through stand volume, harvested timber volume and a stand volume index. Biodiversity was examined through structural diversity (Gini index, Shannon tree size diversity index, Simpson’s reciprocal index and evenness index, all applied to diameter classes) and the abundance of large living trees. For all silvicultural systems investigated, stand volume and harvested timber volume have grown since the beginning of the management plans (beginning of the twentieth century in some forests). The largest yields of timber corresponded to the best quality sites with more intensive silvicultural treatments (uniform and group shelterwood systems). The uniform shelterwood system showed lower figures for structural diversity, though not always significant. The best site qualities maintained notable structural diversity values, even under the most intensive management system. The application of the different management systems over decades has revealed a synergy between timber production and structural diversity, particularly in those systems maintaining more than one age class, although results are conditioned by forest harvesting history. The interaction between historical silvicultural treatment and site quality has been identified as an important source of information to understand forest dynamics and functioning of ES provision.

Does forest biomass harvesting for energy reduce fire hazard in the Mediterranean basin? a case study in the Caroig Massif (Eastern Spain)

The Mediterranean basin is a fire-prone area and is expected to continue being so according to projected climate and socioeconomic changes. Sustainable exploitation of forest biomass could have a positive effect on wildfire hazard mitigation. A modelling approach was used to compare how four different Scenarios for biomass collection for energy use affect fire behaviour and potential burnt area at landscape level under extreme meteorological conditions in a typical Mediterranean Massif. A case study of Pinus halepensis stands in Valencia (Eastern Spain) was conducted. The FARSITE simulator was used to evaluate the burnt area and fire behaviour parameters. Simulations predicted a significant increase in the burnt area and the values of most fire behaviour parameters in a Scenario of rural abandonment, relative to the current situation. Biomass management through thinning reduced canopy bulk density; however, no differences in the values of the main fire behaviour parameters were detected. Thinning and understory clearing, including biomass collection in large shrub fuel model areas, significantly reduces fire hazard. Forest biomass sustainable harvesting for energy is expected to reduce fire hazard if management includes intense modification of fuel models, comprising management of shrub biomass at the landscape level. Strong modification of forest fuel models requires intensive silvicultural treatments. Therefore, forest biomass collection for energy in the Mediterranean basin reduces fire hazard only if both tree and shrub strata are managed at landscape level.

Low-density spruce plantations increase foraging by moose in a northeastern temperate forest

Several North American jurisdictions are adopting new forest management practices that favor sustainable development and biodiversity conservation, but that are also expected to reduce timber yield. In many regions, forest managers have identified areas of intensive timber production where spruce plantations and thinning treatments are to be used extensively. Concomitantly, wildlife managers are concerned that intensive silvicultural treatments will have a negative impact on sport hunting by modifying the behavior and abundance of game species. We evaluated whether an experimental low-density spruce plantation (1350stems/ha) could increase habitat suitability for moose Alces americanus compared to standard high-density plantations currently used throughout eastern Canada (∼2000stems/ha). We evaluated the effects of plantation type, pre-commercial thinning, and age class of plantations on proxies of habitat suitability and use by moose in a northeastern temperate forest of Bas-Saint-Laurent, Québec (Canada). We also considered various environmental characteristics measured locally and within 3.14-km2 landscape contexts to explain spatial variations in use by moose among 540 sampling plots. Our results show that the proportion of stems browsed by moose increased with the number of available stems and decreased with vertical cover. The number of moose feces, an index of time spent by moose in sampling plots, was similar in both plantation types, but was lower in thinned and young (5years old) stands as compared to unthinned and 15years old stands. Variations in the proportion of browsed stems and the number of feces were not explained by broad-scale indices of food availability, density of edges between stands offering good cover and foraging opportunities, road density, elevation, or the area occupied by plantations and naturally regenerated stands around sampling plots. Moose used low-density plantations significantly more than standard plantations for browsing, and these stands supported higher stem densities and vertical cover than standard high-density plantations on average. Low-density plantations offered good foraging opportunities for moose by allowing a large variety of palatable deciduous species to grow between planted coniferous stems. However, we found high inter-site variability in environmental characteristics following plantation, even among equivalent treatments. This suggests that forest managers should aim for particular stand characteristics (i.e. high availability of stems and low vertical cover) in situ rather than prescribing specific post-harvest silvicultural treatments (e.g., plantation types) to favor moose. We recommend the use of unthinned low-density plantations in northern temperate regions where the management objective is to maintain high moose hunting success.

Family, environment and silviculture effects in pure- and mixed-family stands of loblolly (Pinus taeda L.) and slash (P. elliottii Engelm. var. elliotttii) pine

Few studies have quantified the combined effects of environmental conditions, the planting of elite full-sib pine families, intra-specific competition, and intensive silvicultural treatment on unit area production of loblolly pine and slash pine. This study examined these factors at age 2 and 10years for factorial experiments in the Western Gulf (WG) area of the southeastern United States. The experiments consisted of seven pine families (five elite and one poor full-sib loblolly pine families, one elite full-sib slash pine family), two silvicultural intensities (high and low intensity), and three sites. Two deployment methods (mixed and pure-family plots) were used to examine crop and competition ideotypes from among the loblolly families deployed. Family and site were significant main effects at both ages for both individual tree (diameter, height) and stand growth (basal area, volume), and culture was only significant at age 2years. Significant interactions of culture×site and family×site for different growth metrics indicated varying cultural treatment and family performance effects at the different sites, but family response was consistent across cultural treatments. At age 2 and 10years, the deployment main effect was significant for tree height, and for stand basal area and volume. A deployment×site×family interaction for DBH identified a competition ideotype (fast grower) and crop ideotype (slow grower) at the better overall site. The competition ideotype that performed best was not from the WG region, while the slash pine families performed poorly and suffered high levels of storm damage. For loblolly pine, wind damage was the most severe for the plots with low silvicultural intensity. Overall, these results suggested that high performing loblolly pine families do well under a variety of conditions in the WG region and that the competition ideotype and stand uniformity may result in less mortality and greater resistance to wind damage.

Fixed physiological parameters in the 3-PG model produced accurate estimates of loblolly pine growth on sites in different geographic regions

The goal of this project was to determine if 3-PG could accurately predict growth of loblolly pine (Pinus taeda) plantations across a range of sites in the Piedmont and Coastal Plain provinces of Georgia using a fixed physiological parameter set. The model was slightly modified to improve predictions of volume, mortality and initial biomass growth. We hypothesized that because: (a) many physiological attributes of loblolly pine including rates of net photosynthesis, dark respiration, stomatal conductance and specific leaf area tend to be very similar across sites, and (b) leaf area is highly responsive to fertility but less so to water and other environmental factors, a single physiological parameter set would be suitable for predicting growth across a range of loblolly pine plantations which differed in soil type, climate, and silvicultural treatments. The parameter set was obtained from a combination of published values in the literature and model calibrations developed from a single highly productive stand in the Coastal Plain province in Georgia. Differences in potential productivity among sites were accounted for by only changing the value of the fertility rating and the soil type. The calibrated model was evaluated using observed growth data obtained from a slower growing stand at the same Coastal Plain site as the calibration stand, and three other sites, two in the Piedmont province and one in the Coastal Plain. At each of the four locations the model was evaluated using growth data from two plantations, one that received minimal silvicultural inputs and another that received a highly intensive silvicultural treatment, including complete and sustained competition control and annual fertilization.The model performed well on all stands and treatments, and accurately estimated stem biomass and diameter growth. The percent average deviation between predicted and observed values was less than 20% on most sites. The model did not accurately predict stand density in some cases and tended to overestimate volume on sites with low intensity silviculture. The inaccuracy in predicting volume was attributed to parameterization on a highly fertilized site and an inability to account for fertilization effects on wood density. Despite the discrepancies in measured and modeled stem density and volume it is our conclusion that, overall, the 3-PG model provided an accurate description of loblolly pine plantation growth and productivity and was a particularly good predictor of stand biomass in both the Piedmont and Coastal Plain provinces of the Southeastern US using a single set of physiological parameters.

Environmental and genetic effects on crown shape in young loblolly pine plantations

Tree crown shape is an important trait affecting the light environment in forest canopies. We examined genetic and environmental effects on outer crown shape of young single-family stands of loblolly pine ( Pinus taeda L.). Crown diameter profiles were measured after canopy closure at four experimental sites in the southeastern US. The two examined families of contrasting aboveground productivity differed in crown length but not in their outer crown shapes or crown shape ratios, defined as the ratio of crown diameter to crown length. Within each site, intensive silvicultural treatment, consisting of fertilization and control of competing vegetation, had little effect upon crown shape. A strongly significant effect of site on crown shape parameters was found in the family grown at all four experimental sites; however, density differences among the experimental series likely accounted for a part of the across-sites variation in crown shape. In contrast to other studies on crown shape in trees, and to findings at age 2 years in the same stands, we conclude that family effects on the outer crown shape were small compared with the environmental effects in these 5-year-old pine plantations, following canopy closure.

Silvicultural treatments enhance growth rates of future crop trees in a tropical dry forest

Silvicultural treatments are often needed in selectively logged tropical forest to enhance the growth rates of many commercial tree species and, consequently, for recovering a larger proportion of the initial volume harvested over the next cutting cycle. The available data in the literature suggest, however, that the effect of silvicultural treatments on tree growth is smaller in dry forests than in humid forest tree species. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates of future crop trees (FCTs; i.e., trees of current and potentially commercial timber species with adequate form and apparent growth potential). The study was carried out in a tropical dry forest in Bolivia where a set of 21.25-ha plots were monitored for 4 years post-logging. Plots received one of four treatments that varied in intensity of both logging and silvicultural treatments as follows: normal (reduced-impact) logging; normal logging and low-intensity silviculture; increased logging intensity and high-intensity silviculture; and, unlogged controls. The silvicultural treatments applied to FCTs involved liberation from lianas and overtopping trees. Results showed that rates of FCT stem diameter growth increased with light availability, logging intensity, and intensity of silvicultural treatments, and decrease with liana infestation degree. Growth rate increment was larger in the light and intensive silvicultural treatment (22–27%). Long-lived pioneer species showed the strongest response to intensive silviculture (50% increase) followed by total shade-tolerant species (24%) and partial shade-tolerant species (10%). While reduced-impact logging is often not sufficient to guarantee the sustainability of timber yields, application of silvicultural treatments that substantially enhanced the growth rates of FCTs will help move the management of these forests closer to the goal of sustained yield.

Altering successional trends in oak forests: 19 year experimental results of low- and moderate-intensity silvicultural treatments

Intensive silvicultural treatments can sometimes prevent the conversion of an oak (Quercus spp.) forest to a forest composed of mesophytic competitors following harvest, but the required labor is a disincentive for many private landowners. In this study, shelterwood removal, commercial clear-cutting, understory control, and oak underplanting were conducted on mesic and dry–mesic sites in southwestern Wisconsin to evaluate the effect of these treatments on forest composition and to identify the least intensive combination needed for successful oak regeneration. Commercial clear-cutting, with or without prior herbicide spray of low vegetation and oak underplanting, resulted in nearly complete dominance by a wide array of non-oak species on both mesic and dry–mesic sites. In contrast, 153–903 ha–1of the oaks that were underplanted on shelterwood – understory removal plots successfully achieved dominant or codominant status by age 19. Control of tall understory saplings was essential for successful oak regeneration on both sites. On the mesic site, oak underplanting was an additional necessary treatment, whereas natural regeneration was adequate in shelterwood plots on the dry–mesic site. The study suggests that successful oak regeneration can be obtained on productive sites in this region after a single application of a moderately intense silvicultural treatment, although the effort required for understory control may still be an obstacle to widespread application without external incentives.

Regeneration of commercial tree species following silvicultural treatments in a moist tropical forest

Silvicultural treatments are generally performed to improve yields of commercially valuable tree species by increasing their recruitment and growth rates. In this study we analyze the effects of three different sets of silvicultural treatments on the densities and growth rates of seedlings, saplings and poles of 23 commercial tree species in a moist tropical forest in Bolivia. The treatments vary in intensity of logging and silviculture application, and are compared to a control treatment. Silvicultural treatments applied were liberation of future crop trees from lianas and neighboring competing trees, soil scarification and stand refinements. Treatments were applied to twelve 27-ha plots. In each plot 4 transects were established to assess the density and growth of the regeneration of the 23 commercial species. Effects were measured 1 and 4 years after treatment application and were described using three ecological guilds; shade-tolerant species, partially shade-tolerant species, and long-lived pioneers. We found that the intensive silviculture treatment had the largest impact on the density and growth rates of the regeneration of the commercial species. Overall, the density of regeneration of the commercial species was higher in the control treatment than in the logged treatments 1 year after treatment application, but 3 years later these differences had disappeared. Nevertheless, there were marked shifts in densities when different size classes were considered. In nearly all treatments, the number seedlings decreased over time, while the number of saplings and poles increased. Overall shade-tolerant species were more abundant than the other two ecological guilds. Treatment had a positive effect on density only for long-lived pioneers. Growth of commercial tree regeneration was strongly affected by treatment and was highest in the intensive silvicultural treatment plots where growth of long-lived pioneers was twice that of shade-tolerant species and partial shade-tolerant species. Apart from silvicultural treatments and ecological guild, light availability had the strongest effect on growth rates. These results show that different silvicultural treatments have different effects on the regeneration of commercial tree species and that ecological guilds-specific treatments should be considered in management plans for sustainable timber production in tropical lowland forests.

Assemblages of wood-inhabiting fungi related to silvicultural management intensity in beech forests in southern Germany

Current silvicultural treatments in beech forests are aimed at achieving thick logs without discoloured hardwood. Therefore intensive thinning is applied already in younger stands with the objective of large-sized trunks at an age of 100 years. However, this approach bears the risk that dead wood structures and broken trees are completely removed from the forest. The impact of three different silvicultural management intensity levels on wood-inhabiting fungi over decades was investigated in a large beech forest (>10,000 ha) in southern Germany in 69 sampling plots: A Intensive Thinning and Logging with high-value trees, B Conservation-Oriented Logging with integration of special structures such as dead wood and broken trees and C Strict Forest Reserves with no logging for 30 years. The analysis of community showed marked differences in the fungus species composition of the three treatments, independent of stand age. The relative frequencies of species between treatments were statistically different. Indicator species for naturalness were more abundant at sites with low silvicultural management intensity. Fomes fomentarius, the most common fungus in virgin forests and strict forest reserves, is almost missing in forests with high-management intensity. The species richness seemed to be lower where intensive thinning was applied (P = 0.051). Species characteristic for coarse woody debris were associated to low management intensity, whereas species with a significant preference for stumps became more frequent with increasing management intensity. A total amount of dead wood higher than 60 m3/ha was found to enable significantly higher numbers of species indicators of naturalness (P = 0.013). In conclusion, when applying intensive silvicultural treatment, the role of dead wood needs to be actively considered in order to maintain the natural biocoenosis of beech forests.

Effects of silvicultural treatments on survival and growth of trees planted on reclaimed mine lands in the Appalachians

Reforestation of reclaimed surface mined lands in the Appalachian coal producing region is difficult because most sites have dense ground covers, compacted soils, and unfavorable soil chemical properties. This study evaluated the effects of a range of silvicultural treatments on the survival and growth of different tree species planted on reclaimed coal mines in the Appalachians. Three sites were selected for study, one each in Ohio (OH), West Virginia (WV), and Virginia (VA). At each site, plots were planted with three species: (1) hybrid poplar; (2) white pine; and (3) a native hardwood mix. A gradient of silvicultural treatments designed to improve survival and growth of seedlings was applied: (1) weed control only; (2) weed control plus tillage; and (3) weed control plus tillage plus fertilization. First year survival and growth varied among the three sites and the species planted. In Virginia where the minesoil was developed from oxidized sandstone, survival and growth was better than at the sites in West Virginia and Ohio where siltstone and shale derived minesoils dominated the sites. Hardwood survival across treatments was 80%, 85% and 50% for the sites in Virginia, West Virginia, and Ohio, while white pine survival was 27%, 41%, and 58%, and hybrid poplar survival was 37%, 41%, and 72%, respectively. Growth of hybrid poplar increased in response to increasing silvicultural inputs while growth of white pine and the native hardwoods were generally not affected by the silvicultural treatments applied. Hybrid poplar height and diameter growth were superior to the other species. Height growth of this species was 127 cm during the first year in the most intensive treatment at the site in Virginia. In comparison, the greatest height growth of white pine and hardwood was 9 cm and 8 cm, respectively. Detailed measurements of above- and below-ground biomass and tissue nutrient concentrations were made on the hybrid poplar at the site in West Virginia. Hybrid poplar biomass increased from 16 g to 104 g from the least intensive to the most intensive silvicultural treatment for this site. The weed control + tillage + fertilization treatment improved the foliar nutrition compared to the other treatments. The survival and growth of hybrid poplar on these sites suggest that this species may be well suited for reforesting reclaimed mined land in the Appalachians.

Variations in the tree-ring structure of Norway spruce ( Picea abies) under contrasting climates

Variations in tree-ring structure from pith to bark of mature Norway spruce ( Picea abies Karst. (L)) grown under contrasting climate conditions (warm-dry vs. cool-humid) in south-western Germany were investigated. Sample trees were from even-aged stands where no intensive silvicultural treatments had taken place. The cell number (CN), diameter (CD), lumen diameter (CL) and wall thickness (CW) were measured from stem cross-sections taken at breast height. A raw data chronology of each cell parameter was established for the whole annual ring (AR), earlywood (EW), latewood (LW), and transition wood (TW). The long-term trends of the cell parameters were generally non-linear, parameter-specific in AR and EW and similar over sites. Those in LW were site-specific and similar over cell parameters. The variation of the same parameter, expressed by the coefficient of variance (CV), tended to increase from EW towards LW and was clearly higher for CN than for other cell parameters of all tree-ring zones. Trees from the warm-dry site had more LW cells and substantially thicker CW, whereas those from the cool-humid site had larger EW cells. These observed differences are likely due to the hydraulic adaptation mechanisms of trees to different site conditions.

Differential responses of Bolivian timber species to prescribed fire and other gap treatments

We followed the establishment and growth response of 13 commercial tree species to canopy opening, above-ground biomass removal, and experimental burns of low and high intensities in a lowland dry forest in Bolivia. Three patterns of response to treatments were observed among the most abundant commercial tree species. (1) Shade-intolerant species regenerated mostly from seed and had the highest survival and growth rates following high-intensity burns. (2) Shade-tolerant species were abundant in gap control and plant removal treatments. Treatments had little effect on the height growth of these species. (3) Individuals of root sprouting species were most abundant following plant removal and low-intensity burn treatments. Treatments had little effect on the height growth of these species. The wide variation in species’ responses to gap treatments found in this study not only reinforces the concept that species are distributed along a continuum of shade-tolerance levels, but that other aspects of species’ biology, such as seed dispersal type or sprouting behavior, further differentiate regeneration strategies. The variety of regeneration strategies found among the species at this forest site will require a flexible management scheme that mixes more intensive silvicultural treatments such as prescribed burning with less intensive treatments.

English

Surface mined lands in the Appalachian coal producing region reclaimed after the passage of the Surface Mining Control and Reclamation Act of 1977 (SMCRA) have been found to have dense ground covers, compacted soil materials, and unfavorable soil chemical properties. To address these concerns three study sites, which had been reclaimed post-SMCRA, were located in Lawrence County, Ohio, Nicholas County, West Virginia, and Wise County, Virginia. At each site, three species assemblages were planted across a gradient of three levels of silvicultural intensity intended to alleviate the previously mentioned problems associated with post-SMCRA mined land. Response to treatment was variable by site with the site in Virginia having the best survival and greatest growth of the three sites. Hardwood species survived better at all sites than white pine or hybrid poplar. Hardwood survival across treatments was 80 and 85% for sites in Virginia and West Virginia respectively, while only 50% in Ohio. Hybrid poplar height and diameter growth were superior to other species with the height growth of this species reaching 126.6cm in the most intensive treatment at the site in Virginia. Hybrid poplar biomass increased from 15.7g to 104.5g from the least intensive to the most intensive silvicultural treatment for the site in Nicholas County, West Virginia. Hybrid poplar's excellent response to silvicultural treatment and adequate survival, especially at the site in Virginia, may give this species an advantage over the others tested in this experiment for reverting post-SMCRA reclaimed mined lands supporting grasses back to forests.