Predicting breeding bird occurrence by stand- and microhabitat-scale features in even-aged stands in the Central Appalachians

Spatial scale is an important consideration when managing forest wildlife habitat, and models can be used to improve our understanding of these habitats at relevant scales. Our objectives were to determine whether stand- or microhabitat-scale variables better predicted bird metrics (diversity, species presence, and abundance) and to examine breeding bird response to clearcut size and age in a highly forested landscape. In 2004-2007, vegetation data were collected from 62 even-aged stands that were 3.6-34.6 ha in size and harvested in 1963-1990 on the Monongahela National Forest, WV, USA. In 2005-2007, we also surveyed birds at vegetation plots. We used classification and regression trees to model breeding bird habitat use with a suite of stand and microhabitat variables. Among stand variables, elevation, stand age, and stand size were most commonly retained as important variables in guild and species models. Among microhabitat variables, medium-sized tree density and tree species diversity most commonly predicted bird presence or abundance. Early successional and generalist bird presence, abundance, and diversity were better predicted by microhabitat variables than stand variables. Thus, more intensive field sampling may be required to predict habitat use for these species, and management may be needed at a finer scale. Conversely, stand-level variables had greater utility in predicting late-successional species occurrence and abundance; thus management decisions and modeling at this scale may be suitable in areas with a uniform landscape, such as our study area. Our study suggests that late-successional breeding bird diversity can be maximized long-term by including harvests >10 ha in size into our study area and by increasing tree diversity. Some harvesting will need to be incorporated regularly, because after 15 years, the study stands did not provide habitat for most early successional breeding specialists.     

Post-breeding bird responses to canopy tree retention, stand size, and edge in regenerating Appalachian hardwood stands

Avian use of even-aged timber harvests is likely affected by stand attributes such as size, amount of edge, and retained basal area, all characteristics that can easily be manipulated in timber harvesting plans. However, few studies have examined their effects during the post-breeding period. We studied the impacts of clearcut, low-leave two-age, and high-leave two-age harvesting on post-breeding birds using transect sampling and mist-netting in north-central West Virginia. In our approach, we studied the effects of these harvest types as well as stand size and edge on species characteristic of both early-successional and mature forest habitats. In 2005-2006, 13 stands ranging from 4 to 10 years post-harvest and 4-21 ha in size were sampled from late June through mid-August. Capture rates and relative abundance were similar among treatments for generalist birds. Early-successional birds had the lowest capture rates and fewer species (∼30% lower), and late-successional birds reached their highest abundance and species totals (double the other treatments) in high-leave two-age stands. Area sensitivity was evident for all breeding habitat groups. Both generalist and late-successional bird captures were negatively related to stand size, but these groups showed no clear edge effects. Mean relative abundance decreased to nearly zero for the latter group in the largest stands. In contrast, early-successional species tended to use stand interiors more often and responded positively to stand size. Capture rates for this group tripled as stand size increased from 4 to 21 ha. Few birds in the forest periphery responded to harvest edge types despite within-stand edge effects evident for several species. To create suitable habitat for early-successional birds, large, non-linear openings with a low retained basal area are ideal, while smaller harvests and increased residual tree retention would provide habitat for more late-successional birds post-breeding. Although our study has identified habitat use patterns for different species in timber harvests, understanding habitat-specific bird survival is needed to help determine the quality of silvicultural harvests for post-breeding birds.     

Market impacts of hypothetical fuel treatment thinning programs on federal lands in the western United States

This paper addresses the economics of forest fuel thinning programs on federal lands in the U.S. West, and presents a model of regional timber and product market impacts. The issue of economics is vital to the debate about fire management, and this paper presents market implications of two alternative silvicultural strategies, even-aged and uneven-aged thinning. Projections are based on a regional market model called FTM—West (Fuel Treatment Market model—West), which uses the method of price-endogenous linear programming to project annual market equilibria for softwood timber and wood products in the western United States from 1997 to 2020. The model takes into account variability in tree and log size, as well as economic effects of variable size class on harvest costs, log value, product recovery and mill capacity. Results show large potential market impacts from expanded thinning on federal lands, but impacts vary by silvicultural regime due to differences in size–class distributions of trees available under different thinning regimes. A hypothetical even-aged thinning program (“thin-from-below” strategy) results in net negative market welfare over the projection period (2005–2020), while a hypothetical uneven-aged thinning program (thinning based on stand density index) results in positive net market welfare. Net welfare results are the same over a range of different subsidy and administrative fee assumptions. An implication is that even-aged thinning regimes on federal lands in the U.S. West are less economical and therefore will be less effective.     

Patterns of lodgepole pine regeneration following the 1988 Yellowstone fires

In 1988, fires killed extensive lodgepole pine (Pinus contorta Dougl. ex. Loud) in Yellowstone National Park. This species bears both serotinous and non-serotinous cones, with the former most common in fire-origin stands of an even-aged character. Reconnaissance of burned stands indicated that former even-aged communities regenerated effectively. Others did not. The larger and more uniformly-sized seedling under formerly even-aged communities suggests primarily a single wave of regeneration there. Seedlings appeared to initiate to some degree over multiple years under other stands, but not sufficiently to make them well stocked. Four different regeneration pathways seem to characterize the natural reforestation of lodgepole pine following the 1988 fires. These include: (1) a dense, uniformly distributed cohort that will develop as a single-storied stand; (2) lodgepole pine islands that form over long periods around isolated seedlings; (3) a moderate to low density cohort that will gradually fill with multiple age classes over a protracted period; and (4) a cohort of only widely scattered single seedlings that initially form as small nearby tree islands, and may eventually converge into a more continuous stand with multiple age classes.     

Evaluation of forest management systems under risk of wildfire

We evaluate the economic efficiency of even- and uneven-aged management systems under risk of wildfire. The management problems are formulated for a mixed-conifer stand and approximations of the optimal solutions are obtained using simulation optimization. The Northern Idaho variant of the Forest Vegetation Simulator and its Fire and Fuels Extension is used to predict stand growth and fire effects. Interest rate and fire risk are found to be critical determinants of the superior stand management system and timber supply. Uneven-aged management is superior with higher interest rates with or without fire risk. Alterations in the interest rate affect optimal stocking levels of uneven-aged stands, but have only minor effects on the long-run timber supply. Higher interest rates reduce rotation length and regeneration investments of even-aged stands, which lead to markedly reduced timber supply. Increasing fire risk increases the relative efficiency of even-aged management because a single age cohort is less susceptible to fire damage over the course of the rotation than multiple cohorts in uneven-aged stands. Higher fire risk reduces optimal diameter limit under uneven-aged management and decreases optimal rotation length and planting density under even-aged management.     

Development of a stand density management diagram for even-aged pedunculate oak stands and its use in designing thinning schedules

Density management is the usual method used by silviculturiststo achieve a desired future stand condition, and one of themost effective methods of design, display and evaluation ofalternative density management regimes in even-aged stands isthe use of stand density management diagrams. In the presentstudy, we describe a method for developing thinning schedulesfor even-aged pedunculate oak (Quercus robur L.) stands in Galicia(north-western Spain), using a density management diagram. Thediagram integrates the relationships among stand density, dominantheight, quadratic mean diameter and stand volume in a singlegraph. The data used in its construction were obtained from172 sample plots located throughout Galicia. The diagram isbasically composed of two equations: the first relates the quadraticmean diameter to the stand density and dominant height; thesecond relates the stand volume to the quadratic mean diameter,stand density and dominant height. These equations were fittedsimultaneously using full information maximum likelihood. Therelative spacing index is used to characterize the growing stockand the diagram provides isolines for dominant height, numberof trees per hectare, quadratic mean diameter and stand volume.Dominant height isolines together with the site index curvesallow specification of the timing of thinnings while intermediateand final harvest volumes are calculated using the stand volumesisolines.     

Effects of even-aged and uneven-aged timber management on dung beetle community attributes in a Missouri Ozark forest

The goal of this study was to estimate the effects of even-aged, uneven-aged and no-harvest forest management on dung beetle community attributes at both landscape and local (either closed or open canopy within treatments) scales. We collected a total 2579 individuals of Scarabaeoidea with 72 baited pitfall traps in the Missouri Ozark Forest Ecosystem Project throughout the summer of 2003. Six species accounted for 81% of all individuals collected, with community composition changing over the summer. At the landscape scale, the effects of treatments on overall abundance and abundance of individual species varied geographically, with forest thinning reducing abundance compared to clear-cutting forest stands and no harvest but in only one of the three blocks. The effects were also dung beetle species-specific, as there were unique responses of abundances of individual beetle species to the treatments. Five species (Ateuchus histeroides, Deltochilum gibbosum, Onthophagus pennsylvanicus, O. taurus, and O. tuberculifrons) were affected by forest thinning. In contrast, at the local scale, canopy opening (through timber harvesting and natural tree falls) increased expected (rarefied) species richness. Ordination showed that community composition was uniquely different among the six harvest treatments by canopy openness combinations. Together these results demonstrate that timber extraction from a temperate forest ecosystem influenced community composition of dung beetles at the landscape level, but this impact varied with cutting treatment, geographically, and by dung beetle species.     

Exploring adaptation to climate change in the forests of central Nova Scotia, Canada

The threat of climate change is now recognized as an imminent issue at the forefront of the forest sector. Incorporating adaptation to climate change into forest management will be vital in the continual and sustainable provision of forest ecosystem services. The objective of this study is to investigate climate change adaptation in forest management using the landscape disturbance model LANDIS-II. The study area was comprised of 14,000 ha of forested watersheds in central Nova Scotia, Canada, managed by Halifax Water, the municipal water utility. Simulated climate change adaptation was directed towards three components of timber harvesting: the canopy-opening size of harvests, the age of harvested trees within a stand, and the species composition of harvested trees within a stand. These three adaptation treatments were simulated singly and in combination with each other in the modeling experiment. The timber supply was found to benefit from climate change in the absence of any adaptation treatment, though there was a loss of target tree species and old growth forest. In the age treatment, all trees in a harvested stand at or below the age of sexual maturity were exempt from harvesting. This was done to promote more-rapid succession to climax forest communities typical of the study area. It was the most effective in maintaining the timber supply, but least effective in promoting resistance to climate change at the prescribed harvest intensity. In the composition treatment, individual tree species were selected for harvest based on their response to climate change in previous research and on management values at Halifax Water to progressively facilitate forest transition under the altered climate. This proved the most effective treatment for maximizing forest age and old-growth area and for promoting stands composed of climatically suited target species. The size treatment was aimed towards building stand complexity and resilience to climate change, and was the most influential treatment on the response of timber supply, forest age, and forest composition to timber harvest when it was combined with other treatments. The combination of all three adaptation treatments yielded an adequate representation of target species and old forest without overly diminishing the timber supply, and was therefore the most effective in minimizing the trade-offs between management values and objectives. These findings support a diverse and multi-faceted approach to climate change adaptation.     

Comparison of tree size structure and growth for partially harvested and even-aged hemlock-spruce stands in southeast Alaska

The effects of partial cutting on tree size structure and stand growth were evaluated in 52 plots in 13 stands in southeast Alaska that were partially harvested 53–96 years ago and compared with 50-year-old even-aged stands that developed after clearcutting. The net basal-area growth was greater in the partially cut plots than in the uncut plots, and basal-area growth generally increased with increasing cutting intensity. However, the basal-area growth of all of the partially harvested stands was significantly less than the growth of 50-year-old even-aged stands, and net basal area growth over the 50 year period since partial harvesting was about 33–43% of the growth of the even-aged stands. Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effect on tree species composition. The tree size distribution of the partially harvested stands was far more complex and well distributed in comparison with the 50-year-old even-aged stands, and included the presence of several trees with diameters of more than 100 cm. These trees included both large-diameter spruce and hemlock trees and were a distinctive structural feature that was noticeably lacking in the even-aged stands.     

Snag density varies with intensity of timber harvest and human access

Many species of vertebrates depend on snags (standing dead trees) for persistence, and limited research suggests that snag density is lower in areas of intensive timber harvest and increased human access. While intensive timber harvest is one source of potential snag loss, ease of human access to forest stands may also facilitate loss via firewood cutting of snags. Accordingly, we hypothesized that density of snags (number of snags/ha) would decline in forest stands with increasing intensity of timber harvest and increasing ease of human access. We tested our hypothesis by sampling stands under varying levels of timber harvest and access on National Forest land in the northwestern United States. Stands with no history of timber harvest had 3 times the density of snags as stands selectively harvested, and 19 times the density as stands having undergone complete harvest. Stands not adjacent to roads had almost 3 times the density of snags as stands adjacent to roads. Unharvested stands adjacent to non-federal lands and closer to towns had lower snag density, as did stands with flat terrain in relation to nearest road. Our findings demonstrate that timber harvest and human access can have substantial effects on snag density. Meeting snag objectives for wildlife will require careful planning and effective mitigations as part of management of timber harvest and human access.     

Riparian forest structure and succession in second-growth stands of the central Cascade Mountains,Washington, USA

We examined the relationship between landform types and riparian forest structure and succession in second-growth stands along mid order streams in the Cascade Mountains, Washington, USA. We sampled tree, sapling, seedling, and shrub characteristics across a range of fluvial geomorphic surfaces, which were classified into four landform classes, including low floodplain, high floodplain, terrace and hillslope. Landform classification was based on topographic characteristics, position relative to the stream channel, and estimated flood frequency. Statistical analyses using generalized estimating equations (GEE) showed that landform exerted a strong influence on the distribution and abundance of conifer and deciduous species and of different tree life stages. The floodplain landforms were characterized by initial disturbance from timber harvest, and ongoing fluvial disturbance, which favored the establishment of deciduous communities dominated by red alder (Alnus rubra) and maintenance of early successional riparian stands. In contrast, the terrace and hillslope landforms were also subject to timber harvest as the stand initiating agent but were unaffected by fluvial disturbance. However, based on differences in species distribution, we infer that forest structure on these two landforms differed from one another as a result of differences in soil moisture levels. Terraces and hillslopes were found to have high conifer tree abundance, but frequency of younger conifers was higher on hillslopes. Deciduous tree reproduction was very low on terraces and hillslopes. Our results also suggest that conifer recruitment in these second-growth riparian forests may be more successful on soil substrates than on coarse woody debris. We propose that the interplay between the disturbance regime (including type, frequency and intensity) and soil moisture conditions played an important role in influencing the course of riparian succession, present stand structure, and future successional trajectories and these were the primary mechanisms driving vegetation differences among landforms.     

Sustainability in multi-aged stands: an analysis of long-term plenter systems

Long-term research plots in multi-aged stands managed with theplenter system were assessed to evaluate sustainability of theplenter system in Central Europe. Plots primarily consistedof Norway spruce (Picea abies (L.) Karst., silver fir (Abiesalba Mill.) or European beech (Fagus sylvatica L.) and weremeasured for seven to 16 measurement intervals over 60–91years. Sustainability was assessed with four types of criteria:stand density, tree species diversity, basal area increment,and stand structure. Comparable even-aged stands were also analysedto compare and evaluate the performance of the measures of sustainability.Measures of species diversity, increment and stand structuraldiversity generally experienced increasing trends over timein these even-aged stands. Basal area generally increased andtrees ha^-1 decreased in multi-aged stands following similarpatterns as in even-aged stands. These results suggest thatthe plenter system is still evolving and is not the model ofsustainability often assumed. Many of the measures used havepotential as indicators of sustainability in multi-aged stands.     

丝栗栲林生长与生产力的研究

在福建省邵武市洪墩采育场，调查丝栗栲林标地１０块，做平均木、树干解析木９株，杉木人工林标地２块，研究丝栗栲的生长与生产力，结果表明：丝栗栲林的胸径、树高及单株材积总生长量，均随年龄的增加而增加；胸径２０ａ前生长最快；树高１６ａ前生长最快；材积３６ａ时尚未有下降的趋势。胸径、树高平均生长量，随年龄增加而增加，当生长量达高峰后，则随年龄的增加而下降；胸径生长高峰，好立地１２ａ，中、劣立地１５ａ；树高生长高峰，好立地１０ａ，中立地８ａ，劣立地１２ａ；材积平均生长量，随年龄增加而增加，好、劣立地３６ａ时仍未下降，中立地３４ａ时生长量最大。胸径、树高连年生长量随年龄增加而下降；材积连年生长量，随年龄增加而增加，当生长量达高峰后，则随年龄增加而下降，生长高峰出现的年龄，好立地２８ａ，中立地２２ａ，劣立地２６ａ。在相似的立地条件下，丝栗栲林的蓄积量比杉木人工林低，但乔木层总生物量比杉木林高。     

The effects of partial cutting on stand structure and growth of western hemlock–Sitka spruce stands in southeast Alaska

The effects of partial cutting on species composition, new and residual-tree cohorts, tree size distribution, and tree growth was evaluated on 73 plots in 18 stands throughout southeast Alaska. These partially cut stands were harvested 12–96 years ago, when 16–96% of the former stand basal area was removed.Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effects on tree species composition. The establishment of new-tree cohorts was positively related to the proportion of basal-area cut. The current stand basal area, tree species composition, and stand growth were significantly related to trees left after harvest (p<0.001). Trees that were 20–80 cm dbh at the time of cutting had the greatest tree-diameter and basal-area growth and contributed the most to stand growth. Diameter growth of Sitka spruce and western hemlock was similar, and the proportion of stand basal-area growth between species was consistent for different cutting intensities.Concerns about changing tree species composition, lack of spruce regeneration, and greatly reduced stand growth and vigor with partial cuts were largely unsubstantiated. Silvicultural systems based on partial cutting can provide rapidly growing trees for timber production while maintaining complex stand structures with mixtures of spruce and hemlock trees similar to old-growth stands.     

Spatial patterns in mixed coniferous even-aged,uneven-aged and conversion stands

Different methodological approaches from the field of spatial statistics, the index of cluster size (ICS) and quadrat methods such as the two-term and three-term local quadrat variance (TTLQV and 3TLQV) and the new local variance (NLV) were tested to find a simple spatial measure to classify mixed coniferous uneven-aged, even-aged and conversion stands in the central Black Forest area of Germany. Altogether six stands were analysed with regularly distributed sample plots of 0.25 ha (50×50 m), each subdivided into 25 quadrats of 10×10 m. In each of the quadrats, diameter at breast height (dbh) for trees of the overstory (dbh>7 cm) was assessed and classified into three diameter classes. Height measurements were used to develop specific stand height curves for each stand and to calculate the standing volume per tree and per quadrat. The even-aged stands showed a regular distribution of the standing volume, while the conversion and uneven-aged stands were more clustered. This was detected using ICS, which proved to be a simple but very efficient measure for stand structure. The ICS also showed a highly random distribution of small and medium trees and a regular distribution of large trees of the overstory in the uneven-aged stand. Large and medium trees of one even-aged stand were also regularly distributed while conversion stands showed a regular, random or slightly clustered distribution of these trees. The more uneven the ages in the stands were, the larger were the phases detected by the NLV. The findings of the ICS were generally supported by the TTLQV and 3TLQV. The more uneven the ages in a stand were, the less clustered were the trees of different sizes of the understory. Clustering also decreased with increasing height of understory trees. The patterns detected in the investigated stands were related to the effect of different management regimes. Implications for the management of conversions stands based on the findings of the study are given.     

A density management diagram for Norway spruce in the temperate European montane region

Norway spruce is one of the most important conifer tree species in Europe, paramount for timber provision, habitat, recreation, and protection of mountain roads and settlements from natural hazards. Although natural Norway spruce forests exhibit diverse structures, even-aged stands can arise after disturbance or as the result of common silvicultural practice, including off-site afforestation. Many even-aged Norway spruce forests face issues such as senescence, insufficient regeneration, mechanical stability, sensitivity to biotic disturbances, and restoration. We propose the use of Density Management Diagrams (DMD), stand-scale graphical models designed to project growth and yield of even-aged forests, as a heuristic tool for assessing the structure and development of even-aged Norway spruce stands. DMDs are predicated on basic tree allometry and the assumption that self-thinning occurs predictably in forest stands. We designed a DMD for Norway spruce in temperate Europe based on wide-ranging forest inventory data. Quantitative relationships between tree- and stand-level variables that describe resistance to selected natural disturbances were superimposed on the DMD. These susceptibility zones were used to demonstrate assessment and possible management actions related to, for example, windfirmness and effectiveness of the protective function against rockfall or avalanches. The Norway spruce DMD provides forest managers and silviculturists a simple, easy-to-use, tool for evaluating stand dynamics and scheduling needed density management actions.     

Stand structure, competition and growth of Scots pine (Pinus sylvestris L.) in a Mediterranean mountainous environment

The relationship between competition and tree growth was studied in four stands of Pinus sylvestris L. occurring in a continental Mediterranean mountain area (in the Guadarrama range, Spain), i.e., an uneven-aged stand, a stand with oak (Quercus pyrenaica Willd.) understorey, a plantation, and a mature even-aged stand. Competition was measured by a simple size-ratio distance-independent index and was negatively associated with tree diameter. This negative association was stronger in the uneven-aged, plantation and mature even-aged stands than in the stand with oak understorey. Competition was also negatively associated with current diameter increment. This relationship was moderately strong in the mature even-aged stand and weak in the uneven-aged stand and the plantation. In the uneven-aged and the mature even-aged stands, a weakly significant relationship was found between diameter growth and tree size, whereas these parameters were not associated in the stand with oak understorey. The competition index provided a better prediction of growth rate than the alternative use of diameter. Both diameter and basal area growth were greater in the uneven-aged than in the even-aged stands.     

Optimal management of a flammable multi-stand forest for timber production and maintenance of nesting sites for wildlife

Decline of cavity-using wildlife species is a major forest management issue. One of the causes of this problem is the loss in cavity tree abundance, resulting from short rotation silviculture, stand-replacing disturbance events and timber harvesting in disturbed stands. Cavity tree availability cannot be guaranteed due to the stochastic nature of disturbance events. We developed a Markov model to predict future cavity tree availability under alternative tree felling and fire protection strategies using information on cavity tree dynamics and fire history. Stochastic dynamic programming was used to find a strategy that maximizes timber revenues less forest management costs, including the cost of an artificial nest-box program that must be implemented whenever cavity trees become critically scarce. The requirement to implement a nest-box program in such circumstances strongly influenced the optimal tree felling strategy and resulted in a higher probability of having cavity trees in the future. This reflected an increase in the retention of old growth forest and stands with fire-killed cavity trees as well as stands of younger trees to provide a future source of cavities. These results demonstrate the need to consider the costs of artificial habitat enhancement and the risk of future cavity tree scarcity in multiple-use forest management planning.     

Development of a stand density management diagram for Santalum album plantations in Karnataka,India

Stand density management diagrams are average stand-level models that graphically display the relationship between stand yield, density, height and diameter throughout the various stages of forest development in even-aged stands. These are useful tools for designing, displaying and evaluating alternative density regimes in even-aged forest ecosystems to achieve a desired future condition. In this paper, we present a stand density management diagram constructed for sandalwood stands in Karnataka state of India. The relationship between stand density, dominant height, quadratic mean diameter, relative spacing and stand volume is exhibited in one graph. The relative spacing index was used to characterise the growing stock level. Two equations were fitted to the data collected from 19 sample plots measured annually for three years: one relates quadratic mean diameter with stand density and dominant height, whereas the other relates total stand volume with quadratic mean diameter, stand density and dominant height.     

Aboveground biomass and nutrient allocation in an age-sequence of <Emphasis Type="Italic">Larix olgensis</Emphasis> plantations

Biomass and nutrient (N, P, K, Ca, Mg) stock in various aboveground tree components (stemwood, stembark, branches and leaves) were quantified in an age sequence of pure Larix olgensis planta- tions (20, 35, 53 and 69 years old) in Northeast China. The results show that the aboveground biomass allocation in various tree components was in the order of stemwood (62%-83%), branches (9%-21%), stembark (7%-11%) and leaves (1%-6%) for all stands. The proportion of stemwood biomass to total aboveground biomass increased whereas that of other tree components decreased consistently with stand age from 20 to 53 years old, but kept relatively constant with stand age from 53 and 69 years old. The nutrient allocation in various tree components generally followed the same pattern as the biomass allocation (i.e. stemwood > branches > stembark > leaves). The proportion of nutrient stock in leaves to total aboveground nutrient stock decreased consistently with increasing stand age, while that in stemwood increased with stand age from 20 to 53 years old but then decreased from 53 to 69 years old. The rate of nutrient removal for stands was estimated at different stand ages under different logging schemes, showing that the rate of nutrient removal would be unchanged when the rotation length was shortened to 20 years by the harvest of stem only, but greatly increased by the harvest of total aboveground biomass. The rate of nutrient removal would be a considerable reduction for all elements by debarking, especially for Ca.