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1.
Forest carbon storage in the northeastern United States: Net effects of harvesting frequency,post-harvest retention,and wood products 总被引：1，自引：0，他引：1
Temperate forests are an important carbon sink, yet there is debate regarding the net effect of forest management practices on carbon storage. Few studies have investigated the effects of different silvicultural systems on forest carbon stocks, and the relative strength of in situ forest carbon versus wood products pools remains in question. Our research describes (1) the impact of harvesting frequency and proportion of post-harvest structural retention on carbon storage in northern hardwood-conifer forests, and (2) tests the significance of including harvested wood products in carbon accounting at the stand scale. We stratified Forest Inventory and Analysis (FIA) plots to control for environmental, forest structural and compositional variables, resulting in 32 FIA plots distributed throughout the northeastern U.S. We used the USDA Forest Service's Forest Vegetation Simulator to project stand development over a 160 year period under nine different forest management scenarios. Simulated treatments represented a gradient of increasing structural retention and decreasing harvesting frequencies, including a “no harvest” scenario. The simulations incorporated carbon flux between aboveground forest biomass (dead and live pools) and harvested wood products. Mean carbon storage over the simulation period was calculated for each silvicultural scenario. We investigated tradeoffs among scenarios using a factorial treatment design and two-way ANOVA. Mean carbon sequestration was significantly (α = 0.05) greater for “no management” compared to any of the active management scenarios. Of the harvest treatments, those favoring high levels of structural retention and decreased harvesting frequency stored the greatest amounts of carbon. Classification and regression tree analysis showed that management scenario was the strongest predictor of total carbon storage, though site-specific variables were important secondary predictors. In order to isolate the effect of in situ forest carbon storage and harvested wood products, we did not include the emissions benefits associated with substituting wood fiber for other construction materials or energy sources. Modeling results from this study show that harvesting frequency and structural retention significantly affect mean carbon storage. Our results illustrate the importance of both post-harvest forest structure and harvesting frequency in carbon storage, and are valuable to land owners interested in managing forests for carbon sequestration. 相似文献
2.
Ferhat Kara 《Journal of Sustainable Forestry》2018,37(4):403-413
Stand density management tools help forest managers and landowners to more effectively allocate growing space so that specific silvicultural objectives can be met. Due to the economic importance of Oriental beech (Fagus orientalis Lipsky) forests in Turkey, a stand density management tool was developed for this species to optimize regeneration success rate and tree growth. For the development of this tool, named stand density management diagram (SDMD), we utilized forest inventory data from the Kastamonu Regional Forest Directorate in Turkey. Previously published forest management approaches and models were employed during the development of the tool. The SDMD illustrates the relation among four forest indexes: the basal area per hectare, number of trees per hectare, forest stand volume per hectare, and quadratic mean diameter of the beech stands. The stand stocking percent (SSP) can be determined based upon any two of these four measurements. The results suggest that SSP is a better predictor of tree growth than BA in Oriental beech forests. The newly developed SDMD allows for a more effective use of the growing space to achieve specific silvicultural objectives including tree regeneration, timber production, thinning planning, and wildlife protection in Oriental beech forests. 相似文献
3.
落叶松云冷杉林矩阵生长模型及多目标经营模拟 总被引：2，自引：0，他引：2
以吉林省汪清林业局金沟岭林场落叶松云冷杉林为研究对象,利用20块样地4次5年间隔的调查数据,建立多树种(组)非线性矩阵生长模型。结果表明:影响进阶、枯损和进界概率的变量包括径阶中值、林分断面积、树种多样性、最小径阶株数和海拔。采用普通最小二乘法和似不相关回归对3个子模型参数进行估计,发现二者无显著差异。采用分树种组不同径阶的预测值和实际值进行卡方检验,结果表明模型可以用于该林分的生长预测。选用木材产量、树种和大小多样性、树木地上碳贮量作为经营目标,按采伐周期和采伐强度设计13种经营方案,利用建立的矩阵生长模型模拟不同经营方案50年的经营效果,发现3个目标下的最优采伐方案并不一致,即相互冲突,需要进行折衷。以相同权重构造综合目标,结果表明13种经营方案中,长周期(15年)低强度(5%)为最优方案,即可以满足对木材生产、保护多样性和增加碳贮量多目标的需要,这说明合理的经营可以实现森林的多个目标。矩阵生长模型可作为多目标森林经营决策的工具,也为我国东北林区落叶松云冷杉林的多目标经营提供了决策依据。 相似文献
4.
We focused our attention on quantifying the factor complex of forest regeneration in 423 mature and old stands with contrasting
environmental conditions. We recorded the microhabitat selection of tree recruits, the frequency of tree seedlings, and evaluated
the drivers of sapling abundance and diversity. The majority of forest regeneration was established on undisturbed forest
floor. Dead wood was a frequent substrate in spruce-(co)dominated forests. Seedling frequency within a stand was related to
the site-type specific productivity gradient of stands—pine seedlings were common in low-productivity and spruce in high-productivity
boreal forests. Seedlings of temperate broad-leaved trees dominated in productive boreonemoral forests, except for oak, which
showed a uniform distribution of abundance in all forest site-types. Sapling abundance was dictated by forest site-type, and
facilitated by stand diversity, variability in stand closure, lying dead wood, abundant moss, and a thick organic layer. Only
in boreal forests was sapling abundance suppressed by the abundant spruce and younger trees. Upon considering the relationship
between sapling abundance and species richness, sapling diversity was dependent on forest site-type, suppressed by stand density
and dead wood (old gap) abundance, and facilitated by stand diversity. In addition, boreonemoral stands, competition from
herbs, and facilitation by mosses occurred. The observed pattern of tree recruitment points to the importance of top-down
effects of the overstory, competing or facilitating interactions with forest floor vegetation, and availability of regeneration
microhabitats, which in complex make their ecology comparable with forest herbs. Natural forest regeneration can be enhanced
if silvicultural methods support mixed stands and enhance field layer diversity. Oak can provide the universal tree species
to improve stand structure over a wide range of habitats. 相似文献
5.
Douglas-fir trees about 21 years old and growing on a poor site were thinned and fertilized causing accelerated growth. The characteristics of the wood across the 30-year age span were studied for 7 trees from the treated plot. Four trees of nearly uniform ring growth were also studied for some characteristics. Radial and tangential tracheid diameters, tracheid length and percent latewood were correlated quite well with log of age, coefficients ranged from 0.76 to 0.88 on pooled data. All tracheid dimensions when correlated with log of age gave high coefficients on a within-tree basis. The strongest relationship in all age-related factors was between 0 and 12 to 14 years. Specific gravity increased with age in all trees to about 16 to 18 years, then leveled off.Fertilization and thinning caused immediate production of lower density wood with somewhat lower percent latewood, a slight decrease in tracheid diameter tangentially but slightly greater radially, and a small decrease in tracheid length. The effects were mainly in the first 3 to 4 years after treatment, then there was recovery to normal wood density and cell dimensions. Wood from the trees of uniform growth showed no significant change over the same time period in percent latewood, specific gravity, and tracheid length.The research was financed by funds from State of Washington Initiative 171, Institute of Forest Products and the College of Forest Resources, University of Washington, Seattle. 相似文献
6.
The radial pattern of both maximum ring density and ring area of 36 black spruce trees were used to determine the transition age from juvenile wood to mature wood. The data were obtained by X-ray densitometry and both segmented linear and polynomial regressions were used to point out the age of the juvenile wood boundary. Three stand densities (1,790, 2,700 and 3,400 stems/ha) and three sampling heights (2.4, 5.1 and 7.8 m) were studied. Although maximum ring density and ring area presented similar radial patterns, they gave two significantly different results of transition ages. The maximum ring density over-estimated the transition age (17.6 years) in contrast to ring area (14 years). The results show that the transition from juvenile wood to mature wood occurred after 12 years at 7.8 m (versus 13.1 years at a height of 5.1 m, and 17.6 years at 2.4 m). Although transition age occurred later in the high stand density group (21 years), the difference was not significant between the three stand density groups. Nevertheless, transition age remains difficult to determine since no standard definition exists. The transition occurs over years, and most probably a transition wood exists between juvenile wood and mature wood. Estimation of the juvenile wood proportion in volume shows that it remains constant along the stem and it increases with stand density. 相似文献
7.
R. W. Kennedy 《Wood Science and Technology》1995,29(5):321-338
Summary As the raw material base for forest products manufacturing shifts from old-growth to short-rotation plantation stock, the wood from these younger trees will contain larger proportions of juvenile wood. This in turn will influence the quality of forest products obtained. The pattern of specific gravity variation in these trees, which varies among the five most important Pacific Northwest species groups, is reviewed, and the nature of their differences is related to growth habit. The shade intolerance of some species is speculated to manifest itself in an early culmination of annual height inrement, after which specific gravity increases rapidly to a maximum. This is contrasted to shade-tolerant species, in which specific gravity may take several decades to attain a minimum value, followed by only moderate increases thereafter. In addition, faster growth rates in widely spaced plantation trees tend to depress specific gravity and advance the age at which these trees reach their minimum value, thereby compounding the overall wood density of deficit of short-rotation trees.Lower specific gravity, compounded with reduced lignin content in juvenile wood, negatively influences kraft pulp yield, but not pulp quality parameters such as sheet density, burst and tensile strength. Reduced wood density, coupled with larger fibril angles in juvenile wood, reduces average strength and stiffness of lumber from younger plantation trees. Mechanical stress rating needs to be adopted to segregate the strong, stiff material for engineered construction uses, because a large proportion of visually graded lumber from juvenile wood zones will not meet currently assigned stress values. Mechanical stress rating can ensure a continued stream of appropriate engineering grades from future tree supplies.I am indebted to Professor Simon Ellis of the Department of Wood Science, Faculty of Forestry, University of B.C., for providing data on mechanical tests of western hemlockAcademy Lecture presented at the 40th Anniversary Annual Meeting of the Japan Wood Research Society, April, 1995, in Tokyo 相似文献
8.
《Forest Ecology and Management》1999,123(1):81-90
We produced a map of the biomass density and pools, at the county scale of resolution, of all forests of the eastern US using new approaches for converting inventoried wood volume to estimates of above and belowground biomass. Maps provide a visual representation of the pattern of forest biomass densities and pools over space that are useful for forest managers and decision makers, and as databases for verification of vegetation models. We estimated biomass density and pools at the county level from the USDA Forest Service, Forest Inventory and Analysis database on growing stock volume by forest type and stand size-class, and mapped the results in a geographic information system. We converted stand volume to aboveground biomass with regression equations for biomass expansion factors (BEF; ratio of aboveground biomass density of all living trees to merchantable volume) versus stand volume. Belowground biomass was estimated as a function of aboveground biomass with regression equations. Total biomass density for hardwood forests ranged from 36 to 344 Mg ha−1, with an area-weighted mean of 159 Mg ha−1. About 50% of all counties had hardwood forests with biomass densities between 125 and 175 Mg ha−1. For softwood forests, biomass density ranged from 2 to 346 Mg ha−1, with an area-weighted mean of 110 Mg ha−1. Biomass densities were generally lower for softwoods than for hardwoods; ca. 40% of all counties had softwood forests with biomass densities between 75 and 125 Mg ha−1. Highest amounts of forest biomass were located in the Northern Lake states, mountain areas of the Mid-Atlantic states, and parts of New England, and lowest amounts in the Midwest states. The total biomass for all eastern forests for the late 1980s was estimated at 20.5 Pg, 80% of which was in hardwood forests. 相似文献
9.
Olli-Pekka Tikkanen Jukka Matero Mikko M?nkk?nen Artti Juutinen Jari Kouki 《European Journal of Forest Research》2012,131(5):1411-1422
Maintenance of biodiversity in commercial forests has become a main goal in forestry, and several new management principles to reach that goal have been introduced lately. For example, in even-aged forestry, tree retention (leaving a proportion of trees standing in clear-cut sites) is widely used to increase the structural diversity and the amount of dead wood in forests. However, the cost-efficiency of the new management principles is poorly studied. To increase the amount of dead wood, an alternative way could be a change in the thinning regime, so that the self-thinning builds up of woody debris of a growing stand. We used long-term (200?years) simulations to compare ecological and economical effects of the two alternative management practices to increase the amount of dead wood in forest stands: (1) green tree retention and (2) growing stands unthinned. We simulated stand growth and management of 12 pine and 12 spruce stands that represented sites in different parts of Finland. We found that growing stands unthinned produced about 5–6?times more dead wood than retention with 20 trees left per hectare. In terms of economical loss, leaving stands unthinned reduced the net present value of harvest revenues less than 20%. Consequently, leaving stands unthinned offers a cost-effective option to increase the amount of dead wood in commercial forests. The effects of unthinned management were, however, dependent on thermal sum and initial stand density, indicating that biodiversity-oriented management practices should be designed for local conditions. 相似文献
10.
根据人工用材林培育目标和对木材分级利用的观念,以黑龙江省佳木斯市孟家岗林场的落叶松人工林为研究对象．运用Weibull分布函数对林分的直径分布规律进行研究,通过模型预估得到各个径阶的详细收获量和各材种的出材量。由此得到不同利用方式的经营收入,结合生产投入,运用经济效果评价动态分析法中的效益成本比、净现值指标对落叶松人工林进行研究。结果显示：落叶松人工林的经济轮伐期为：13～18a。林分密度为1000株／hm^2时,效益成本比RBG最大值为3．8653,净现值胛矿最大值为9574．3元;l500株／hm^2时,RBC为4．2486,NPV为14408．6元;2000株/hm^2时,RBC为4．4937,NPV为16705．9元;2500株／hm^2时,RBC为4．685,NPV为19256．3元;3000株／hm^2时,RBC为4．8671,NPV为21749．7元;具有较好的经济效益。研究结果还表明落叶松人工林林分密度越大,经济轮伐期越大。 相似文献
11.
In densely populated regions, forests can help protect communities and infrastructures from natural hazards such as avalanches and rockfall. To promote the protective function, substantial efforts are made to actively manage forest stands. In 2009 alone the Swiss government invested more than 60 million sfr for the maintenance of protection forests. However, to date there has been no comprehensive evaluation of how the structural development of actively managed stands differs from that of passively managed stands in the Alps. Over the past century the structure of Norway-spruce dominated subalpine forests of the Swiss Alps has been changing and it is not clear how these changes affect the potential protective function of these forests, as well as other forest functions such as wildlife habitat. Furthermore, it is not clear how stand dynamics and structural changes differ between stands that are actively managed and those that are passively managed, and thus to what degree active efforts of forest management are contributing to stands that actually have a greater protective function than passively managed forests.In this study, we analyzed the dynamics of subalpine forests using time series of forest inventory data and examined the influence of active vs. passive management, exposition, distance to treeline, elevation and slope steepness on stand structure and dynamics. We analyzed data from 395 plots in dense, subalpine, spruce-dominated forests in the Swiss Alps. Data were collected during three distinct periods (1983-1985, 1993-1995 and 2004-2006) as part of the Swiss National Forest Inventory (NFI). Using regression trees and multivariate statistics, we investigated which factors have the most important influence on tree growth and stand development.Overall, forest density increased significantly over the last 20 years and the predominance of dense forests increased at higher elevations. However, forest density has not increased in actively managed forests over the past 10 years. In passively managed stands, density was higher on south-facing slopes than on north-facing slopes. The volume and density of dead wood has increased over the last 20 years in both actively managed and passively managed forests. Active management over the last 20 years has maintained forest conditions that adequately maintain stands’ protection functions in the Swiss Alps. However, stand development, especially increasing density, in the passively managed stands of the Swiss Alps suggests that the majority of passively managed stands also provide adequate protective functions against rock and avalanche hazards without the high costs of active management. 相似文献
12.
Large areas of forests in the Pacific Northwest are being transformed to younger forests, yet little is known about the impact this may have on hydrological cycles. Previous work suggests that old trees use less water per unit leaf area or sapwood area than young mature trees of the same species in similar environments. Do old forests, therefore, use less water than young mature forests in similar environments, or are there other structural or compositional components in the forests that compensate for tree-level differences? We investigated the impacts of tree age, species composition and sapwood basal area on stand-level transpiration in adjacent watersheds at the H.J. Andrews Forest in the western Cascades of Oregon, one containing a young, mature (about 40 years since disturbance) conifer forest and the other an old growth (about 450 years since disturbance) forest. Sap flow measurements were used to evaluate the degree to which differences in age and species composition affect water use. Stand sapwood basal area was evaluated based on a vegetation survey for species, basal area and sapwood basal area in the riparian area of two watersheds. A simple scaling exercise derived from estimated differences in water use as a result of differences in age, species composition and stand sapwood area was used to estimate transpiration from late June through October within the entire riparian area of these watersheds. Transpiration was higher in the young stand because of greater sap flux density (sap flow per unit sapwood area) by age class and species, and greater total stand sapwood area. During the measurement period, mean daily sap flux density was 2.30 times higher in young compared with old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. Sap flux density was 1.41 times higher in young red alder (Alnus rubra Bong.) compared with young P. menziesii trees, and was 1.45 times higher in old P. menziesii compared with old western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees. Overall, sapwood basal area was 21% higher in the young stand than in the old stand. In the old forest, T. heterophylla is an important co-dominant, accounting for 58% of total sapwood basal area, whereas P. menziesii is the only dominant conifer in the young stand. Angiosperms accounted for 36% of total sapwood basal area in the young stand, but only 7% in the old stand. For all factors combined, we estimated 3.27 times more water use by vegetation in the riparian area of the young stand over the measurement period. Tree age had the greatest effect on stand differences in water use, followed by differences in sapwood basal area, and finally species composition. The large differences in transpiration provide further evidence that forest management alters site water balance via elevated transpiration in vigorous young stands. 相似文献
13.
利用林分特征因子预测森林地被可燃物载量的研究 总被引：13，自引：1，他引：12
对大兴安岭林区兴安落叶松林、樟子松林和白桦林3个可燃物类型的68块样地的郁闭度、胸径、树高、林龄等林分因子和地表可燃物（1h、10h、100h时滞可燃物和灌木）的载量进行了野外调查和室内实验分析与计算,应用Spss统计软件,对不同种类可燃物载量与林分因子进行回归分析,并建立了数学模型,利用林分因子来推算不同种类可燃物的载量,并取得较为满意的结果。 相似文献
14.
15.
马尾松木材性状的遗传变异及其在造纸工业中的应用 总被引：2，自引：1，他引：1
综述了马尾松木材比重，管胞长度、晚材率及它们的过渡年龄、浆纸性能等在种源、林分、林分内个体及株内的遗传变异，并对马尾松材性改良前景作了讨论。 相似文献
16.
Analyses of land snails and habitat factors in acid beech forests were conducted in southern Germany (northern Bavaria). The
objectives were to study the effects of habitat characteristics on snail density and species richness. Habitat structures
were determined for 37 plots in one big forest. We found a significant relationship between the number of snail species and
individuals and the following set of habitat factors coverage of herbaceous layer, growing stock, mean diameter at breast
height of the three largest trees (DBHmax), stand age, total dead wood volume per ha, and advanced decomposed dead wood volume
per ha. We use maximally selected rank statistics to estimate cutpoints separating stands with low densities, from stands
with high snail densities. Here, we define cutpoints for a significant higher snail density at a stand age of 187 years, 57 m3/ha dead wood, 40 m3/ha advanced decomposed dead wood, 63 cm DBHmax and more than 1% herbaceous layer. For species richness, cutpoints are estimated
at 338 m3/ha stand volume, 170 years stand age, 50 m3/ha total dead wood amount, 15 m3/ha advanced decomposed dead wood and 56 cm DBHmax. The microhabitat analysis shows a higher pH value and a higher Calcium
content at the bottom of large snags and under large lying dead wood pieces in comparison to litter, upper mineral soil and
at the bottom of vital living trees. Snail species and individual density are significantly linked to these patterns of chemical
parameters. The identified cutpoints are a good base for ecological management decisions in forest management. 相似文献
17.
传统收获表是指某一树种在特定地区和管理体系下，以立地条件和年龄为变量描述林分平均生长过程的数表．林分密度管理图是根据林分密度效果编制的可预测林分平均收获的图．通过与传统收获表和林分密度管理图的概观比较和探讨，该文系统地阐述了系统收获表的概念和功能．系统收获表的基本特点是为预测现实林分在不同立地条件和管理体系下生长过程的计算机程序．因此，系统收获表能描述在多维变量（如年龄、立地条件、林分密度、胸径和树高）条件下的现实林分和单木的无数生长过程 相似文献
18.
This study examines the structural characteristics of the tree layer, dead wood, canopy openings, and regeneration patterns of a spruce old-growth forest in the Bohemian Forest, Czech Republic. An old-growth stand with minor human influence and a stand that was presumably logged about 200 years ago were analyzed and compared, as some forest managers considered the presumable human impact as a reason for salvage logging. Even though the stands differed in tree density, height and DBH structure, it was not possible to conclude whether it was due to management history or the environmental differences. The volume of dead wood also differed between the stands. There was about 142 and 83 m3 ha−1 of dead wood in the old-growth stand and presumably logged stand, respectively. The amount of dead wood found in the old-growth stand was comparable with values reported from spruce old-growth stands across Central Europe. In both stands, many canopy trees were arranged in linear patterns, which was a result of spruce regeneration on nurse logs. This suggests that the origin and development of the stands were characterized by natural processes and during the past 200 years typical old-growth structural characteristics have already evolved. 相似文献
19.
利用西藏自治区森林资源连续清查的天然林实测样地资料,研究建立了冷杉、云杉、柏木、松类、栎类、桦类、阔叶类、针阔类8个树种组的平均直径、平均树高和平均蓄积估测模型,为预估西藏天然林的有关林分因子提供参考依据。 相似文献
20.
Dana R. Warren Clifford E. Kraft William S. Keeton Jared S. Nunery Gene E. Likens 《Forest Ecology and Management》2009
Wood is an important component of forested stream ecosystems, and stream restoration efforts often incorporate large wood. In most cases, however, stream restoration projects are implemented without information regarding the amount of wood that historically occurred or the natural rates of wood recruitment. This study uses a space-for-time analysis to quantify large wood loading to 28 streams in the northeastern US with a range of in-stream and riparian forest characteristics. We document the current volume and frequency of occurrence of large wood in streams with riparian forests varying in their stage of stand development as well as stream size and gradient. Linear models relating stream wood characteristics to stream geomorphic and forest characteristics were compared using Akaike's Information Criterion (AIC) model selection. The AIC analysis indicated that the volume and frequency of large wood and wood accumulations (wood jams) in streams was most closely associated with the age of the dominant canopy trees in the riparian forest (best models: log10(large wood volume (m3 100 m−1)) = (0.0036 × stand age) − 0.2281, p < 0.001, r2 = 0.80; and large wood frequency (number per 100 m) = (0.1326 × stand age) + 7.3952, p < 001, r2 = 0.63). Bankfull width was an important factor accounting for wood volume per unit area (m3 ha−1) but not the volume of wood per length of stream (100 m−1). The empirical models developed in this study were unsuccessful in predicting wood loading in other regions, most likely due to difference in forest characteristics and the legacy of forest disturbance. However, these models may be applicable in other streams in the northeastern US or in streams with comparable riparian forests, underlying geology, and disturbance regimes—factors that could alter long-term wood loading dynamics. Our results highlight the importance of understanding region-specific processes when planning stream restoration and stream management projects. 相似文献