共查询到20条相似文献，搜索用时 31 毫秒
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Akio Inoue 《Journal of Forest Research》2009,14(5):268-275
An allometric model of the maximum size–density relationship between mean stem surface area and stand density is proposed,
and is fitted to data for even-aged pure stands of Japanese cedar (Cryptomeria japonica D. Don) and Japanese cypress (Chamaecyparis obtusa Endl.). To derive the model, the biomass density was defined as the ratio of the mean stem surface area to the side area
of an imaginary column, of which radius and height were equal to the radius of the mean area occupied by a tree and mean tree
height, respectively. According to the model, the slope of the maximum size–density relationship on logarithmic coordinates
can be estimated from the allometric power relationships of mean tree height and biomass density to mean stem surface area.
The resulting slope was −1.089 for the cedar and −0.974 for the cypress. The estimated maximum size–density relationship corresponded
well with the combinations of mean stem surface area and stand density for the overcrowded stands of cedar and cypress. The
steeper slope for cedar was attributed to the allocation of more resources to height growth compared to cypress. The maximum
total stem surface area was approximated to be 1.483 ha/ha for cedar and 0.949 ha/ha for cypress stands. The difference in
the maximum total stem surface area between the two species was produced by the characteristics related to tree height and
stem biomass packing into space already occupied. 相似文献
3.
《Forest Ecology and Management》2002,155(1-3):163-170
The maximum size–density relationships or self-thinning lines were developed for three mixed-softwood climax forest habitats (hemlock-red spruce, spruce-fir, and cedar-black spruce) in the northeastern USA. The plot data were collected from an extensive data base used in growth studies from 1950 to 1970, and represented a wide range of species compositions, sites, management options, and densities. Plots having late successional species compositions with relative density index higher than 0.7 were selected as the most fully-stocked plots for model development. Reduced major axis regression was used to fit the self-thinning lines to the data. The differences between the three forest habitats were tested using the 95% confidence intervals of the coefficients of the self-thinning lines. The results indicated that there were no differences between the hemlock-red spruce and spruce-fir habitats for both relationships of the mean tree volume versus number of trees, and the quadratic mean tree diameter versus number of trees. Thus, these two habitats were combined to develop a single self-thinning line. However, the cedar-black spruce forest habitat required a separate self-thinning line. These maximum size–density relationships can be readily used to construct stand density management diagrams. 相似文献
4.
A simultaneous estimation procedure for the parameters of two functions, i.e., the maximum size–density line and the self-thinning
curve, is presented to predict stand development for fast-growing tropical species. This procedure assumes that the rate of
periodic reduction in stand density with increasing quadratic mean diameter on a logarithmic scale (r) will increase inversely proportionally to the distance from the maximum size–density line and consequently equals the slope
of the line at distance 0. Under this assumption, the maximum size–density line can be incorporated into the self-thinning
curve to form an integrated equation with three parameters: k and m, the slope and constant of the maximum size–density line, and a, the rate of reduction of r of the self-thinning curve. These parameters are estimated simultaneously using measurement data on stand density, quadratic
mean diameter, and the corresponding r. This procedure was evaluated by application to two data sets: 186 measurements of Acacia mangium and 95 measurements of Paraserianthes falcataria, for which the parameters k and m have previously been calculated. The parameters estimated using this procedure were in good agreement with previous ones
based on the A. mangium data set, and the differences found for the P. falcataria data set were also small, within the error variances. Therefore, it is concluded that the proposed procedure would give almost
the same estimates from a single calculation step as the previous procedure that required two separate calculation steps. 相似文献
5.
Luciana Cavalcante Pereira-Rollo Demóstenes Ferreira da Silva Filho Mario Tomazello Filho Sergio de Oliveira Moraes Hilton Thadeu Zarate do Couto 《Wood Science and Technology》2014,48(4):689-701
Tomography is a wave-based technique used to depicture tree cross-sections; specifically, impulse tomography uses data given by the passage of impulse waves, which were primarily influenced by density, modulus of elasticity, and moisture content of wood. The influence of wood characteristics on various kinds of waves has been extensively studied, allowing the establishment of statistical correlations between wave behavior and wood properties. In this context, the relationship between impulse speed from cross-section tomography and conditioned density that was obtained on diametrical sample by X-ray densitometry was analyzed using logs of three tree species with different densities that were air dried to 12 % moisture content. For each species, means from 5 mm length intervals of conditioned density profile graph (ρ 12%) and impulse speed distribution graph (S 12%) on the same diametrical sample are used to fit models. Joining data from all species, the exponential model \( \ln \rho_{12\% } = - 4.32822 + 1.67894 *\ln S_{12\% } \) was obtained with correlation coefficient of 0.85 and highly significant parameters. The results indicate that conditioned density could be explained by impulse speed on the cross-section, but research is necessary to make a useful tool out of it. 相似文献
6.
The pale-winged gray moth, Iridopsis ephyraria (Walker), a native geometrid moth species found across eastern North America, has recently caused severe defoliation of eastern hemlock trees, Tsuga canadensis (L.) Carrière, in south-central Nova Scotia, Canada. Field studies were carried out to develop sampling techniques that could be used to predict subsequent defoliation of mature hemlocks, which are too large to sample by conventional methods. Densities of newly emerged, first-instar larvae, estimated by sticky tape traps, explained 77% of the subsequent current-year shoot defoliation by I. ephyraria. Egg densities from foam oviposition traps and mid-instar larval densities from beating sheets were weakly and usually non-significantly related to defoliation. Therefore, foam oviposition traps could be used to qualitatively estimate egg densities of I. ephyraria, but first-instar larvae must be sampled with sticky tape if accurate predictions of hemlock defoliation are desired. 相似文献
7.
Tree survival and maximum density of planted forests–Observations from South African spacing studies
Background:Among the most important aspects of risk and hazard studies relating to forest ecosystems are maximum forest density and density-dependent tree survival.Methods:Long-term observations about the maximum density of unthinned Pinus patula and P.elliottii field plots based on the Correlated Curve Trend(CCT)spacing studies which were established almost 8 decades ago by O’Connor(Forest Research with Special Reference to Planting Distances and Thinning,1935)in South Africa.Three specific approaches were introduced for analysing maximum density and tree survival,namely the‘limiting line’,Nilson’s sparsity and tree survival with the Weibull function.Results:The main results are:a)Maximum densities differ greatly among the two species grown on the same site and within the same species grown on different sites;it is possible to relate these differences to site index in both species.b)The relationship between the quadratic mean diameter and the minimum average spacing of surviving trees(known as Nilson’s Sparsity)appears to be surprisingly similar in both species.c)An analysis of tree survival in response to different initial planting espacements shows that the Weibull survival function parameters can be estimated if the initial planting density is known.This result is presented for each of the eight large experiments used in this study.Conclusions:This study contributes to a better understanding of tree survival and maximum density which are the key factors required for estimating risk and uncertainty.The risk of tree mortality is not constant,but varies with tree species,planting density,tree age and growing site.For estimating that risk,therefore,continuous long-term observation on different sites and with varying planting densities,as provided by the unthinned CCT series,are essential. 相似文献
8.
Key message
The carbon density was not different between natural and planted forests, while the biomass carbon density was greater in natural forests than in planted forests. The difference is due primarily to the larger carbon density in the standing trees in natural forests compared to planted forests (at an average age of 50.6 and 15.7 years, respectively).Context
Afforestation and reforestation programs might have noticeable effect on carbon stock. An integrated assessment of the forest carbon density in mountain regions is vital to evaluate the contribution of planted forests to carbon sequestration.Aims
We compared the carbon densities and carbon stocks between natural and planted forests in the Lüliang Mountains region where large-scale afforestation and reforestation programs have been implemented. The introduced peashrubs (Caragana spp.), poplars (Populus spp.), black locust (Robinia pseudoacacia), and native Chinese pine (Pinus tabulaeformis) were the four most common species in planted forests. In contrast, the deciduous oaks (Quercus spp.), Asia white birch (Betula platyphylla), wild poplar (Populus davidiana), and Chinese pine (Pinus tabulaeformis) dominated in natural forests.Methods
Based on the forest inventory data of 3768 sample plots, we estimated the values of carbon densities and carbon stocks of natural and planted forests, and analyzed the spatial patterns of carbon densities and the effects of various factors on carbon densities using semivariogram analysis and nested analysis of variance (nested ANOVA), respectively.Results
The carbon density was 123.7 and 119.7 Mg ha?1 for natural and planted forests respectively. Natural and planted forests accounted for 54.8% and 45.2% of the total carbon stock over the whole region, respectively. The biomass carbon density (the above- and belowground biomass plus dead wood and litter biomass carbon density) was greater in natural forests than in planted forests (22.5 versus 13.2 Mg ha?1). The higher (lower) spatial carbon density variability of natural (planted) forests was featured with a much smaller (larger) range value of 32.7 km (102.0 km) within which a strong (moderate) spatial autocorrelation could be observed. Stand age, stand density, annual mean temperature, and annual precipitation had statistically significant effects on the carbon density of all forests in the region.Conclusion
No significant difference was detected in the carbon densities between natural and planted forests, and planted forests have made a substantial contribution to the total carbon stock of the region due to the implementation of large-scale afforestation and reforestation programs. The spatial patterns of carbon densities were clearly different between natural and planted forests. Stand age, stand density, temperature, and precipitation were important factors influencing forest carbon density over the mountain region.9.
Li Zhou Limin Dai Shaoxian Wang Xiangtong Huang Xinchuang Wang Lin Qi Qingwei Wang Guowei Li Yawei Wei Guofan Shao 《Annals of Forest Science》2011,68(5):953-958
Introduction
The old-growth forests on Changbai Mountain have been well protected from human activities and provide a living laboratory for studying forest carbon sequestration under natural environmental conditions. 相似文献10.
The competition–density (C–D) effect for non-self-thinning Populus deltoides and Populus × euramericana plantations from 3 to 9 years was analyzed using the reciprocal equation of the C–D effect. The C–D effect was well described
by the reciprocal equation, and with the progress of time the C–D curve, on logarithmic coordinates, of the P. × euramericana plantations shifted upward faster than that of the P. deltoides plantations. With increasing physical time t, the biological time τ, i.e. the integral from zero to t of the coefficient of growth λ(t) in the general logistic curve with respect to t, increased rapidly during early growth stages and the increases in τ gradually became slow during later growth stages. This trend was more evident in the P. deltoides plantations than in the P. × euramericana plantations. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (=wρ) at a given growth stage, increased abruptly to a maximum value and then tended to decrease gradually to a constant level.
On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume at a given growth stage, decreased exponentially and tended
to be close to zero with increasing τ. The λ(t) decreased with increasing stand age, whereas the final yield Y(t) defined as W(t) ρ, where W(t) is the asymptote of w in the general logistic growth curve, increased gradually with increasing stand age. The differences in coefficients A, B, and λ(t) between the two species were reported. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1):71-80
Abstract This study examines price dynamics in roundwood exports from Russia to Finland, the largest international roundwood trade flow within Europe. The analysis covers six main timber assortments; sawlog and pulpwood dimensions of pine, spruce and birch. The study period, starting from the devaluation of the rouble in August 1998, was characterized by a drastic increase in the volumes of Russian roundwood imported into Finland, and a coinciding structural change in the timber assortment distribution of the Finnish roundwood imports. A basic hypothesis of economic theory, the law of one price, was tested by using quarterly time series and methods of cointegration analysis. According to the cointegration tests, the prices of Finnish and Russian spruce sawlogs have moved closely together. Furthermore, the changes in the prices of spruce sawlogs in the Finnish roundwood market are reflected in the Russian prices and not vice versa. Regarding other timber assortments, price co-movement and consequent market integration was not detected. 相似文献
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Boczoń Andrzej Hilszczańska Dorota Wrzosek Marta Szczepkowski Andrzej Sierota Zbigniew 《European Journal of Forest Research》2021,140(6):1301-1321
European Journal of Forest Research - Drought in the forest is not only a prolonged state of water shortage, but also an occasion where interactions between plants and fungi are affected. Water... 相似文献
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Over the last decade, researchers have developed a range of decision support systems (DSS) which seek to improve the evidence-base for decision-making in the forestry sector in Great Britain. Many are now integral to the systems of forest management and planning used. However, in some cases, levels of adoption have been lower than expected. This problem is neither unique to Great Britain nor to forestry, and increasingly it is being explained in terms of the quality of stakeholder engagement during DSS development and implementation. Thus, social research was undertaken to understand the factors affecting DSS uptake. The methods included an online survey completed by 81 members of the Institute of Chartered Foresters and Forestry Commission staff and 30 semi-structured interviews with stakeholders. Four sets of factors were seen to influence uptake: professional judgement and cultural resistance; communication and access; training, support and consolidation; and meeting user requirements. More generally, our conclusions highlight the need for a shift in the quality of interactions at the science–policy–practice interface: from knowledge-transfer (a unidirectional “bridging of gaps”) to knowledge-exchange (dialogue between collaborating partners) and knowledge-interaction (shared cultures and institutions). 相似文献
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? Context
There are many stand property–density relationships in ecology which represent emergent properties of plant populations. Examples include self-thinning, competition–density effect, constant final yield, and age-related decline in stand growth. We suggest that these relationships are different aspects of a general framework of stand property–density relationships.? Aims
We aim to illustrate the generalities and ecological implications of stand property–density relationships, and organize them in a comprehensive framework.? Methods
We illustrate relationships between stand property and density (1) at one point in time, (2) over time, and (3) independent of time. We review the consequences of considering different variables to characterize stand property (mean tree size, mean tree growth, stand growth, stand yield, stand leaf area).? Results
We provide a framework that integrates the broad categories of stand property–density relationships and individual expressions of these relationships. For example, we conclude that constant final yield is a special case of the growth–growing stock relationship for life forms were yield is a reasonable approximation of growth (non-woody plants).? Conclusion
There is support in the literature for leaf area being broadly integrative with respect to various expressions of stand property–density relationships. We show how this is and suggest implications for plant population ecology and forest management. 相似文献16.
Matthias Schmidt Rainer Hurling 《中国林学(英文版)》2014,(4):185-200
Background： In this paper, a regression model for predicting the spatial distribution of forest cockchafer larvae in the Hessian Ried region （Germany） is presented. The forest cockchafer, a native biotic pest, is a major cause of damage in forests in this region particularly during the regeneration phase. The model developed in this study is based on a systematic sample inventory of forest cockchafer larvae by excavation across the Hessian Ried. These forest cockchafer larvae data were characterized by excess zeros and overdispersion. Methods： Using specific generalized additive regression models, different discrete distributions, including the Poisson, negative binomial and zero-inflated Poisson distributions, were compared. The methodology employed allowed the simultaneous estimation of non-linear model effects of causal covariates and, to account for spatial autocorrelation, of a 2-dimensional spatial trend function. In the validation of the models, both the Akaike information criterion （AIC） and more detailed graphical procedures based on randomized quantile residuals were used. Results： The negative binomial distribution was superior to the Poisson and the zero-inflated Poisson distributions, providing a near perfect fit to the data, which was proven in an extensive validation process. The causal predictors found to affect the density of larvae significantly were distance to water table and percentage of pure clay layer in the soil to a depth of I m. Model predictions showed that larva density increased with an increase in distance to the water table up to almost 4 m, after which it remained constant, and with a reduction in the percentage of pure clay layer. However this latter correlation was weak and requires further investigation. The 2-dimensional trend function indicated a strong spatial effect, and thus explained by far the highest proportion of variation in larva density. Conclusions： As such the model can be used to support forest practitioners in their decision making for regenerati 相似文献
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We investigated the correlation of large fires([300 ha) from 1992 to 2013 within the borders of the Antalya Regional Directorate of Forestry using the Keetch–Byram drought index(KBDI). Daily KBDI values were calculated for each year, and values for the period before the year 2000 differed significantly from those after2000. After 2000(large fires occurred in 2004, 2006, 2007,2008, 2010, and 2013), when KBDI values increased, the KBDI, but not the number of fires, was inversely correlated with the natural log of the burned area(NLBA). While there were both high and low KBDI values when the NLBA was small, only high KBDI values were associated with high NLBA values. Particularly for logarithmic values of 4 and higher, KBDI values increased in parallel with increases in NLBA values. On the basis of a Mann–Whitney U test done in addition to a Pearson correlation test, we found that when the burned areas were grouped according to small and large areas, the KBDI could be used to distinguish the two groups. Using a conditional probability analysis, we found that 4th, 5th and 6th class KBDI values may lead to large fires at the 60 % possibility.Similarly, the possibility of large fires greater than the median burned area in any given 6 years was found to be48 %. In addition, while the mean value of KBDI is 390.51 for the period from May to September for these 6 years, it is 359.93 for the other years. Consequently, the area burned also increased as the KBDI classes(Class 0: 0–99, Class 1:100–199, Class 2: 200–299, Class 3: 300–399, Class 4:400–499, Class 5: 500–599, Class 6: 600–699, and Class 7:700–800) increase. 相似文献
18.
Peter Cronkleton Anne M. Larson Laurène Feintrenie Claude Garcia Patrice Levang 《Small-Scale Forestry》2013,12(1):5-13
At the 2010 Montpellier conference on ‘Taking Stock of Smallholder and Community Forestry: Where do we go from here?’, researchers, policy-makers and practitioners came together to discuss historical trends and future directions for understanding and supporting forest sustainability and local livelihoods in forest-based communities. A consensus arising from these discussions was that there is a need to reframe and broaden approaches to understand forestry practised by smallholders and communities. The paper highlights three key topics from that discussion: (1) the need to reconsider definitions of community forestry, (2) the need to broaden understanding of rights surrounding forest resources and (3) the need to reframe research to focus on management of the forest–farm interface. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(2):140-148
Abstract This study describes forest landscape fragmentation and connectivity along the Finnish–Russian border near the Karelian Isthmus. The landscape pattern was analysed using classification data based on Landsat ETM+ and Landsat TM images in combination with systematic surveys in Finland (Finnish National Forest Inventory) (n=546) and the authors’ own fieldwork data in Russia (n=101). On the Finnish side the forest patches are significantly smaller than on the Russian side. In addition, the Finnish forests landscape is more scattered and distances between patches of the same forest type are longer. The Russian side is more dominated by broadleaved and mixed forest stands. The disparities are due to differences in forestry policy and traditions of forest practices. The growing conditions of the areas are similar. The habitat fragmentation and habitat connectivity are important issues because the Karelian Isthmus is one of three main corridors and migrating routes connecting large Russian boreal taiga forests and their fauna and flora with Finnish isolated boreal forests. 相似文献