Larger Diameter Classes Research Articles

The distribution and incidence of white pine blister rust in central and southeastern Wyoming and northern Colorado

A survey of limber pine ( Pinus flexilis James) to determine the geographic distribution, incidence, and severity of white pine blister rust (WPBR) throughout 13 study areas in central and southeastern Wyoming and northern Colorado was conducted from 2002 to 2004. The majority (81.1%) of the 18 719 surveyed limber pines >1.37 m tall were classified as healthy, 13.5% were declining or dying from various causes, and 5.4% were dead. WPBR was present on 278 (55%) of the 504 survey plots. Incidence of the disease ranged from 0% to 100% and averaged 15.5% over all the plots and 28.0% on the infested plots. Likelihood of infection by WPBR was significantly greater for limber pines in larger diameter classes. Incidence was negatively correlated with elevation and positively correlated with geographic position, with more northerly and easterly plots having higher incidences of WPBR. Incidence varied by slope position and did not vary by aspect, slope configuration, or degree of canopy closure. The current level of infestation in central and southeastern Wyoming and northern Colorado has been attained within the past two to four decades. With time, the pathogen may spread to currently uninfested white pine populations and intensify throughout its current distribution impacting valuable ecosystems.

The role of land tenure in conservation of tree and shrub species diversity in miombo woodlands of southern Malawi

Biodiversity is declining throughout southern African miombo woodlands due to poor land use practices that are detrimental to soil, vegetation and habitat. We aimed at examining tree and shrub species diversity and distribution in Uapaca kirkiana-dominated woodlands under three land tenure types; forest reserves, customary and leasehold land. The study was conducted at different forest sites within similar agroecological zone in southern Malawi. Study sites were located at a range of altitudes between 900 and 1,200 m a.s.l. Three circular plots each with 32.60 m radius were established at each study site to sample tree and shrub species composition, structure and distribution under three land tenure types. We found that forest reserves had higher species diversity with an average of 16 tree families, 27 genera and 34 species as compared to only 10 tree families, 6 genera and 6 species on customary forest lands. Comparisons of diameter at breast height size class distributions showed that customary land had significantly low numbers of small (5.0–10.0 cm) and very large (≥30 cm) diameter classes suggesting lower levels of regeneration and high rate of anthropogenic activities. The high species diversity and richness in forest reserves and leasehold land indicate high potential for protected lands to restore tree species diversity. It is concluded that levels of human activities as influenced by land tenure type reduce tree species diversity, composition and distribution at the different sites, and this confirms the hypothesis that open access lands are not compatible with conservation of tree and shrub species diversity because of high anthropogenic activities.

Dynamics of Species Composition and Importance from 1965–1998 in Baber Woods Nature Preserve, Edgar County, Illinois: Evidence of the Effects of Fire Suppression

ABSTRACT Presently Acer saccharum (sugar maple) dominates the overstory of Baber Woods Nature Preserve with an importance value (IV) of 75.4 (possible 200), more than half the total density (148.4 of 289.4 stems/ha), and numerous individuals in the smaller diameter classes. Second is Quercus alba (white oak) with an IV of 45.9, one-third of the basal area (9.28 of 26.95 m2/ha), which dominates the larger diameter classes, and averages 56.9 cm dbh. Total IV for all oaks combined was 64, and 30 for all hickories combined. Since Baber Woods was first surveyed in 1965, sugar maple has continued to increase in importance, with a corresponding decrease in the importance of oaks and hickories. Data suggest that this woodlot was an open white oak savanna in presettlement time. Fire suppression has resulted in canopy closure and an increase in shade-tolerant, fire-sensitive mesic species like sugar maple.

Landscape-Level Impact of Beech Bark Disease in Relation to Slope and Aspect in New York State

Abstract During the past 40 years, the beech bark disease complex has destabilized the beech component of New York State forests, but a selected portion of the American beech (Fagus grandifolia) population has attained a sustainable forest structure. The influence of slope and aspect in relation to beech bark disease on the sustainability of American beech populations was evaluated. There were differences in the proportion of American beech trees with signs of Neonectria spp. and beech scale (Cryptococcus fagisuga) on eastern and western aspects on slopes ≥16%. American beech populations on northern, northeastern, eastern, southeastern, and southern aspects on slopes ≥16% (23–29% of the sample) displayed diameter distributions that would sustain the current forest structure. In all other sites, observed percentage mortality in the large-diameter classes was higher than predicted, suggesting a future shift in forest structure toward lower densities of large trees in these sites.

Optimization models of stand structure and selective cutting cycle for large diameter trees of broadleaved forest in Changbai Mountain

The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the data from Hongshi Forestry Bureau, in Changbai Mountain region, Jilin Province, China. The data were measured in 232 permanent sample plots. With the data of permanent sample plots, the parameters of transition probability and ingrowth models were estimated, and some models were compared and partly modified. During the simulation of stand structure, four factors such as largest diameter residual tree (LDT), the ratio of the number of trees in a given diameter class to those in the next larger diameter class (q), residual basal area (RBA) and selective cutting cycle (C) were considered. The simulation results showed that the optimum stand structure parameters for large diameter trees are as follows: q is 1.2, LDT is 46cm, RBA is larger than 26 m2 and selective cutting cycle time (C) is between 10 and 20 years.

Woody debris in a 16-year old Pinus radiata plantation in Australia: Mass, carbon and nitrogen stocks, and turnover

Woody debris that is accumulated on the forest floor could potentially be a relatively long-term carbon (C) sink in forest ecosystems. For a 16-year old Pinus radiata D. Don. plantation in Australia, we quantified the dry mass, C and nitrogen (N) stored in woody debris (including dead logs, branches and twigs) relative to the loss of soil C that followed afforestation of the native pasture onto which the plantation had been established. This debris derived mainly from forest management (thinning and pruning) 8 years earlier. The line intersect technique was used on ten 10 m × 12 m plots to estimate the mass of woody debris on the forest floor in 10 diameter classes. There was 6.1 Mg ha −1 of oven dry woody debris, containing 3.1 Mg C ha −1 and 12.9 kg N ha −1, on the forest floor. The largest diameter class (>50 mm) contributed most of the debris’ mass. We also estimated rates of decomposition, and C and N release from the woody debris and calculated its half-life and “life time” (95% disappearance). The overall decay rate constant ( k) for all woody debris was 0.069 year −1. The overall half-life and lifetime was 10 and 43 years, respectively. Almost half (42%) of the original C in woody debris was released in the 8 years of decay, but only 12% of the original N was released. Decay rate varied with size class with the largest diameter (>50 mm) decaying the fastest, the smallest diameter class (<5 mm) decaying the second fastest, and the intermediate size-classes being the slowest to decay. Although N was slowly released from the woody debris, this pool was an effective C sink per unit-N involved because of its high C:N ratio. The C stored in the pool offset 22% of the observed soil C-stock reduction 16 years after land use change from pasture to pine plantation.

Characterisation of overstocked uneven-aged stands of Abies alba Mill. in the Val d’Aran (Spanish Pyrenees). Analysis of the selection cutting treatments applied.

Analysis of the selection cutting treatments applied We describe the structure of uneven-aged silver-fir stands with a growing stock in which large diameter classes initially had an excessive representation. Silvicultural treatments were applied to correct diameter distribution trends towards a regular structure. The initial state of the forest revealed a high density in mature individuals, but no regeneration problems were detected, neither mechanical stability difficulties, in any of the stands. The selective cutting treatments concentrated mainly on trees over the 30-cm diameter class, but all diameter classes were treated. As a result of these silvicultural management actions the polewood layer was released from vertical competition. Yet, stand structure is far from irregular, which precludes to consider these stands in an equilibrium state.

Growth and mortality are related to adult tree size in a Malaysian mixed dipterocarp forest

Tree stature is an important ecological and silvicultural characteristic and the high diversity of many tropical forests is associated with a broad range in species stature. A measure of adult size, the 95th percentile of trunk diameter of all diameters ≥0.1 × maximum observed diameter ( D95 0.1) was found to be independent of species abundance and highly correlated with maximum height. D95 0.1 was determined for 573 species with at least 20 trees with diameters ≥0.1 × maximum observed diameter in old-growth, lowland evergreen forest on the 50-ha forest dynamics plot at Pasoh Forest Reserve, Malaysia. These species, comprising 98.3% of all trees ≥1 cm diameter in the plot, were then divided into five life forms of differing stature; shrubs ( D95 0.1 < 5 cm), treelets (5 cm ≤ D95 0.1 < 12 cm), understory trees (12 cm ≤ D95 0.1 < 25 cm), canopy trees (25 cm ≤ D95 0.1 < 60 cm) and emergents ( D95 0.1 ≥ 60 cm). Each life form showed a distinctive pattern of mortality versus trunk diameter, but all showed higher mortality in the largest diameter class per life form. Mean growth rates increased with trunk diameter within each life form, consistent with reported increases in irradiance with height at Pasoh. Among trees of similar diameter, growth rates increased across life forms from the smallest to largest. These differences in growth rate among life forms may be due to associated differences in allometry, photosynthetic capacity and reproductive allocation.

Calculation of uneven-aged stand structures with the negative exponential diameter distribution and Sterba's modified competition density rule

Depending on Sterba's modified Competition Density Rule [Sterba, H., 1975. Assmann's theorie der grundflächenhaltung die “Competition Density Rule” det Japaner Kira, Ando und Tadaki. Cbl. f.d. ges. Forstw. 92, 46–62], the maximum basal area ( G max), quadratic mean diameter ( d G max ), and stem numbers ( N G max ), for uneven-aged stands of Abies nordmanniana in the Black Sea Region in Turkey were calculated. Then, an exponential diameter distribution as a function of dominant height for these stands was obtained by solving nonlinear system of equations, which uses the maximum basal area ( G max) and the stem numbers ( N G max ) as input values, and gives diminution coefficient ( q) and the number of stems in the largest diameter class ( N 1) as outputs. The results are in accordance to Sterba and Monserud's findings [Sterba, H., Monserud, R.A., 1993. The maximum density concept applied to uneven-aged mixed species stands. For. Sci. 39 (3), 432–452] on the slope of the maximum density line, and with Susmel's [Susmel, L., 1956. Laws and the variation of the parameters in uneven-aged normal forests. L’Italia Forestale e Montana XI (3), 3–14] concept of decreasing q with increasing dominant height.

Determining the optimal selective harvest strategy for mixed-species stands with a transition matrix growth model

An optimization model was developed to determine the optimal harvesting strategy needed for uneven-aged mixed-species stands in the Changbai Mountain region of northeast of China. The model takes into account four variables including residual basal area (RBA), the diameter of the largest tree, harvest cycle and a constant representing the ratio of the number of trees in a given diameter class to those in the next larger diameter class (‘q’). According to model simulations, under the objective of maximizing net revenue, the optimal harvesting strategy is defined when the residual basal area equals to 19 m2 ha−1, the diameter of the largest tree equals to 44 cm, q 1.3 and the harvest cycle equals to 20 years. If the objective is to maximize the total volume yield, the optimal harvesting strategy is defined when RBA equals to 13 m2 ha−1, the diameter of the largest tree equals to 36 cm and the constant ‘q’ equals to 1.9 and the harvest cycle equals to 15 years.

The distribution and severity of beech bark disease in the Catskill Mountains, N.Y.

The distribution and severity of beech bark disease (BBD) in the Catskill Mountains of southeastern New York state, U.S.A., were measured between 1997 and 2000. Forest composition was measured using wedge prism surveys and fixed-area plot counts of canopy species. BBD severity on individual trees was ranked from 1 (no disease) to 5 (dead) based on bark health and canopy loss. These data were analyzed at multiple spatial scales to determine possible controls of disease distribution and severity. BBD was present on almost all Fagus grandifolia Ehrh. (American beech) individuals encountered &gt;10 cm diameter at breast height, but was most severe in larger diameter classes. Mortality due to BBD also increased with diameter class. A strong positive relationship was found between BBD severity and relative beech basal area at the tract (hundreds of hectares) and 100-m elevation band spatial scales, but not found at smaller scales. Successful long-range dispersal of the disease may therefore be dependent upon host density, while local conditions may control BBD severity within individual stands. The current status of BBD in the Catskills suggests these forests are entering the aftermath phase of the disease's progression and that BBD has become an endemic component of these forests.

Characteristics of subalpine fir susceptible to attack by western balsam bark beetle (Coleoptera: Scolytidae)

A diameter distribution survey at three sites in the interior of British Columbia revealed that the western balsam bark beetle (Dryocoetes confusus Swaine) predominately attacked trees from the three to four largest diameter classes at each site. However, the mean diameter of attacked trees was significantly different among sites, indicating that factors other than diameter contribute to the susceptibility of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) to the western balsam bark beetle. A number of tree characteristics, including measures of growth, age, crown size, and phloem thickness, were compared among a total of 22 successfully attacked, 26 unsuccessfully attacked, and 28 unattacked trees at three sites. Of the 12 tree characteristics measured, five showed significant differences between successfully attacked and unattacked trees. Successfully attacked trees had a lower percentage of the bole covered with constant crown, lower crown volume, lower radial growth in the last 5 years, and were older than unattacked trees. Successfully attacked trees also produced less induced resinosis than unsuccessfully attacked trees. The results of this study suggest that western balsam bark beetle mortality may be limited by the presence and distribution of susceptible hosts. The study also identifies a number of variables that could be used in a susceptibility and risk rating model for western balsam bark beetle.

Snag abundance 20, 30, and 40 years following fire and harvesting in boreal forests

The retention of standing dead trees (snags) has become an important conservation concern, especially when forest management efforts attempt to emulate natural disturbance. We investigate the abundance of snags within Ontario's boreal forest following 10–20, 21–30, and 31–40 years of both fire and forest harvest disturbance over a 24 000-km2 area. Fire frequency varied considerably, with 90% of the fires in the study area occurring in the 1970s. We did not detect differences in basal area of snags (m2/km2) between burned and harvested stands. However, differences occurred in dead-stem density (number/km2); the burned stands produced more snags in the 21- to 30-year post-disturbance class and the harvested stands produced more snags in the 31- to 40-year post-disturbance class. Similarly, the distribution of diameter classes of snags differed between the burned and harvested stands. In size classes greater than 32 cm (diameter at breast height), we found more snags in the harvested forests 21–40 years following disturbance. We did not find differences in the basal area of snags between disturbance types, whether they were hardwood or softwood. However, hardwood snags occurred in greater abundance in the larger diameter classes. Our findings are limited by the changing timber harvest treatments (selective harvest, clearcut, and ecological cut), the small number of disturbance events, and the variety of stand compositions. More research is required on the ecological factors influencing snag abundance to improve development of local forest management plans and to design landscapes that conserve forest structure and biodiversity. Key words: biodiversity, clearcut, conservation, coarse woody debris, dead trees, forest management, landscape, snags, wildlife

Effects of selective logging on tree diversity, composition and plant functional type patterns in a Bornean rain forest

Abstract. The effects of selective logging on tree diversity, changes in tree species composition and plant functional types were studied with the use of seven permanent plots in virgin and in logged forest. All plots were located in a lowland dipterocarp rain forest in East Kalimantan on the island of Borneo. Just after logging and during the following 20 yr tree diversity measured as Fishers’α was not significantly affected in logged forest plots. Temporal shifts in tree species composition were analysed with Principal Component Analysis (PCA). Logged forest plots had much larger changes over time than virgin forest plots. In the smallest diameter class, some logged forest plots showed a distinct trajectory in PCA space compared to virgin forest plots, while in larger diameter classes movement of logged plots in PCA space was random. This suggests that there is no predetermined community to which logged forest plots tend to shift when recovering from logging. We found a significant negative correlation between diameter increments and the species‐specific wood densities of tree species. Species‐specific wood density and potential tree height were used to assign species to five PFTs. As expected, logging increased the fraction of softwood stems in small diameter classes. In the largest diameter classes (≥ 50 cm DBH) a strong decrease of softwood emergent stems was found in logged forest plots. After more than 20 yr no recruitment was found of softwood emergent stems in selectively logged forest.

Effects of selective logging on tree diversity, composition and plant functional type patterns in a Bornean rain forest

Abstract. The effects of selective logging on tree diversity, changes in tree species composition and plant functional types were studied with the use of seven permanent plots in virgin and in logged forest. All plots were located in a lowland dipterocarp rain forest in East Kalimantan on the island of Borneo. Just after logging and during the following 20 yr tree diversity measured as Fishers’α was not significantly affected in logged forest plots. Temporal shifts in tree species composition were analysed with Principal Component Analysis (PCA). Logged forest plots had much larger changes over time than virgin forest plots. In the smallest diameter class, some logged forest plots showed a distinct trajectory in PCA space compared to virgin forest plots, while in larger diameter classes movement of logged plots in PCA space was random. This suggests that there is no predetermined community to which logged forest plots tend to shift when recovering from logging. We found a significant negative correlation between diameter increments and the species-specific wood densities of tree species. Species-specific wood density and potential tree height were used to assign species to five PFTs. As expected, logging increased the fraction of softwood stems in small diameter classes. In the largest diameter classes (≥ 50 cm DBH) a strong decrease of softwood emergent stems was found in logged forest plots. After more than 20 yr no recruitment was found of softwood emergent stems in selectively logged forest.

Spatial segregation of pines and oaks under different fire regimes in the Sierra Madre Occidental

Surface fire can modify spatial patterns and self-thinning in pine-oak ecosystems. Spatial pattern analyses were used to compare pattern development and interspecific spatial interactions in trees and seedlings in five Madrean pine-oak stands with different recent fire histories. Interspecific and intraspecific patterns were compared in small (< 15 cm dbh) and large (< 15 cm dbh) diameter classes of the pines (Pinus durangensis, P. teocote, and P. leiophylla) and oaks (Quercus sideroxylla, Q. crassifolia, and Q. laeta) that collectively dominated the five stands. Numbers of juvenile trees in 2.5 × 2.5 m subplots were correlated with cumulative distances to adult trees. Small pine and oak trees were intraspecifically clustered at all scales, irrespective of fire regime. Large pines were strongly clustered only in stands with longer fire-free intervals, and patterns of large versus small pine trees were regular or random in frequent fire stands. These patterns were consistent with fire-induced mortality of maturing trees under frequent fire. Large and small pines were segregated from small oaks at short and long distances in one stand with a 32-year fire-free interval, implying that two or more dynamic factors had produced regular patterns at different scales. Such regular spatial patterns at short distances were not seen in other stands. Therefore, there was little evidence for direct competition between oaks and pines. The results reported here are consistent with studies from other pine-oak ecosystems showing that different fire regime and site factors interact to influence stand development processes and relative dominance of pines and oaks. In some stands, the continued absence of fire could foster increasing tree densities and an intensification of local neighborhood effects, producing segregation of pine and oak species at longer distances.

Examination of stand structure on quail plantations in the Red Hills region of Georgia and Florida managed by the Stoddard-Neel system: an example for forest managers

Longleaf pine ( Pinus palustris Mill.) on quail hunting plantations in the Red Hills region of southern Georgia and northern Florida, USA, has been managed over the last 40 years by the ‘Stoddard–Neel’ system. Developed during World War II, the system focuses on stand structures with low densities and an open midstorey. These structures benefit both hunting and ecological concerns such as herbaceous diversity. We documented the forest stand structure on quail plantations in the Red Hills and compared it to the traditional ‘reverse‐J’ structure. We conducted a variable plot cruise of the study area at an intensity of one plot per 4 hectares. Using these preliminary cruise data, we selected 22 sets of 40‐ha measurement blocks. On the 40‐ha blocks, we measured tree size and location in fixed‐area plots on three randomly chosen transects in each block. The number of trees decreases rapidly as the diameter increases, up to a point. Next, there is a ‘bump’ or second mode in the larger diameter classes, after which the number of trees again decreases. Instead of the classic ‘reverse‐J’ diameter distribution of shade‐tolerant, uneven‐aged forests, this distribution is bimodal. This forestwide structure was observed at the plantation and block level, with observed variation greatly increasing at the transect and plot levels. The shape of the diameter distributions reflects a preferential removal of saplings and midstorey trees for understorey diversity, aesthetics and quail management. These data further suggest that uneven‐aged forests can be managed at the smaller scales as two‐aged (‘two‐sized’) stands. This method also has the advantage of concentrating growing space on larger, higher‐value trees.

Effects of the 1997–98 El Niño drought on rain forests of Mount Kinabalu, Borneo

We examined the effects of the 1997–98 El Niño drought on nine rain forests of Mount Kinabalu, Borneo, at four altitudes (700, 1700, 2700 and 3100 m) on contrasting geological substrata (ultrabasic versus non-ultrabasic). Measurements of rainfall and atmospheric aridity indicated that the departure from normal conditions during the drought became greater with increasing altitude. During 1997–99 (drought period) compared to 1995–97 (pre-drought period), median growth rates of stem diameter of trees decreased for both smaller (4.8–10 cm) and larger (≥ 10 cm) diameter classes in the six upland forests (≥ 2700 m on ultrabasic substrata and ≥ 1700 m on non-ultrabasic substrata), but for neither diameter class in the other forests. The majority of species decreased or did not change growth rates during 1997–99, whereas some did increase. Tree mortality increased during 1997–99, at the larger diameter class in the two lowland forests (700 m) on both substrata, and at least at the smaller diameter class in the four upland forests (≥ 1700 m) on non-ultrabasic substrata. In two of these upland forests, mortality was restricted to particular understorey species. Mortality did not significantly increase in the three upland forests (≥ 1700 m) on ultrabasic substrata; this suggests that the adaptation to nutrient-poor soils might have provided the resistance to drought.

Comparison of structural and compositional characteristics in old-growth and mature, managed hardwood forests of Minnesota, U.S.A.

Extended rotation of managed temperate hardwood forests is sometimes presumed to provide the important compositional and structural features of old-growth hardwood forests. However, the features of temperate hardwood old-growth and managed stands of extended rotation age have not been fully quantified and compared. This study compared quantitative parameters (density and volume of logs and snags, coarse woody debris volume (volume of logs + volume of snags), the proportion of hollow logs, basal area and tree, sapling, large seedling and small seedling densities), distributional patterns (diameter class and rot class of live trees, decay class of logs), and vascular plant species composition and diversity in old-growth and mature, managed sugar maple (Acer saccharum L.) - basswood (Tilia americana L.) and northern red oak (Quercus rubra L.) stands. Old-growth forests had higher coarse woody debris volumes and higher proportions of hollow logs, of live trees in large diameter classes, of logs in decay classes 1 and 2, and of live trees in rot classes 3-5 than the mature, managed forests. Old-growth and mature, managed forests did not differ significantly in plant species composition. These results indicate that, while older extended-rotation, managed stands can be very similar compositionally to old-growth forests, they differ quantitatively in structural features.

Assessing Scarcity of the North Central Veneer Log Resource

Abstract Forest industry professionals have expressed concern about physical scarcity and diminishing quality in veneer logs of the preferred species, contradicting USDA Forest Service inventory results that report an expanding resource base. This study examined factors, influencing economic supply of select white oak, select red oak, hard maple, ash, black cherry, and black walnut veneer logs in the Lake States, Illinois, and Indiana. Increased competition due to international demand is placing additional pressure on available inventory. Changing demographics are acting to reduce supply as nontimber land uses increase in importance. Industry professionals were queried to quantify their perception of scarcity and determine which factors they consider most important. The dominant perception is that quality is decreasing. Profitable architectural and panel grade veneer logs are perceived to be diminishing while furniture grade veneer logs are not. Quantity is perceived to be decreasing in the large and medium diameter classes but increasing in the small diameter classes. Expectation is for future real prices 10 yr hence to increase between 20-30%. Factors for the perceived scarcity ranking highest in importance were increased international demand, previous high grading, landowner mistrust of loggers, and increased environmental regulations. Respondents agreed that the world demand for eastern hardwoods is strong and will continue to grow. North.J. Appl. For. 16(3):160-166.