共查询到20条相似文献,搜索用时 468 毫秒
1.
利用中国林科院热带林业实验研究中心2009年森林资源二类调查数据,分别利用目标线性规划与传统森林轮伐公式计算热林中心马尾松纯林和杉木纯林用材林年采伐量,比较分析同一个经理期(2009—2019年)两种计算方法的不同;结果表明:轮伐公式计算的采伐量一般偏大,且目标规划单位面积年经济收益是轮伐公式获得经济效益的10 20倍。利用目标规划法在同时实现材积收获量最大、出材量最大、净现值收益最大的目标前提下,对森林结构进行调整,使资源分布满足可持续经营的要求,即尽可能达到法正状态。 相似文献
2.
在对浙江省编制“八五”期间采伐限额的有关资料和采伐量计算公式进行广泛研究的基础上,采用技术创造中的经验方法——组合法,综合了常用的采伐量计算公式,即成熟度公式、第一林龄公式、第二林龄公式和面积轮伐公式,形成了新的采伐量计算公式,称采伐量计算通式。采伐量计算通式适合于不同林龄结构的森林经营单位计算合理的森林年伐量(或称采伐限额),保证计算得到的森林采伐量,既保持各龄级期森林采伐的均衡,又可实现森林结构的逐步调整,以达到永续利用的目的。计算通式使计算和判断一体化,解决了采伐量论证中,人为判断决策时可能存在的失误,确保了数据的合理性和准确性。亦可利用框图进行计算程序运算。 相似文献
3.
4.
5.
林木年伐量计算式,是计算年采伐量的公式.对编制森林经营方案和制定长远规划起到重要作用.所计算出的林木年伐量,对制定森林经营方针政策,乃至生产中的实施都有着重要意义. 相似文献
6.
在森林经营方案的编制工作中,关于合理年伐量的确定,除了用运筹学中线性规划原理和方法,分别对各森林经营类型建立森林收获调整模型,通过模型求解,得到合理的采伐面积,既可以改善年龄结构,达到调整的目的(法正状态),保证调整期(一个轮伐期)内最大的采伐收获,即利用线性规划调整森林收获量以外,一般常用公式有轮伐期公式、成熟度公式、第一林龄公式、第二林龄公式、平均生长量公式和蓄积量结合生长量公式进行计算。这六种计算公式,在具体工作中运用时,要在理解公式适应范围的基础上,根据各个经营单位(编案单位)林分结构特… 相似文献
7.
8.
9.
1990年4月15日由福建省林业厅主持,有福建林学院、省林科所、设计院等单位专家教授(林业部及省外知名专家寄来了书面评审意见)参加,通过了研究成果的鉴定。专家们认为:《森林年代量分期衡平法》在成熟度、林龄和轮伐期公式的基础上,,提出了初算选型、调整的一整套森林主伐量确定方法,其原则符合现行规定,所确定的采伐量符合森林资源的客观实际,配备的软件简易,大大减轻了计算和论证工作量。在省采伐限额确定中,应用该方法效果良好。 相似文献
10.
11.
We assessed the effectiveness of alternative forest management strategies for maintaining American martens (Martes americana) in a sub-boreal landscape subject to an extensive mountain pine beetle (Dendroctonus ponderosae) outbreak, associated salvage logging, and climate change in north-central British Columbia, Canada. We structured the analysis in a Bayesian network (BN) meta-model that incorporated the results of spatially explicit modelling of landscape conditions (natural and logging disturbance, habitat quality, number of potential territories, and connectedness of territories) with analytical population modelling. The BN meta-model was then used to examine habitat and population size responses (adult females only are presented) to management scenarios, in the context of uncertainty of model parameters, management objectives, and climate change. Status quo management is dominantly clear-cutting with 3–20% of each harvest unit retained as mature patches, with reforestation by planting in the remainder. Management options we examined were: (1) the status quo, (2) varying the total annual timber harvest on the landscape (100%, 80% or 50% of current long-term sustained yield estimates), (3) the protection of understory trees during logging, and (4) 30–70% retention of overstory (partial cutting in distinct patches <1 ha in size) in each harvest unit, for 33% or 50% of the annual timber harvest. We found that marten habitat and population size declined substantively with the beetle outbreak and associated salvage cutting. The choice of management strategy then had a long-term effect on the potential for marten recovery after the beetle outbreak. Partial cutting scenarios had the greatest average long-term marten population levels, followed in order by reduced harvest rates, understory protection, and the status quo. Management scenarios with the best chance of meeting conservation goals without over-protecting habitat (and thus unnecessarily constraining timber management) varied with the population objective chosen. The choice of management strategy will depend on the weighting of marten outcomes against the economic desirability of timber harvest strategies, willingness to gamble on climate change, and the time-frame of interest. 相似文献
12.
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. 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(2):120-127
Abstract This study quantified, across a landscape in Eastern Finland, the influence of administrative land-use and technical land-form constraints on timber production. Spatially explicit data about the nature conservation areas, land use plans and steep slopes were integrated with Multi-source National Forest Inventory (MS-NFI) data. The Finnish forestry model MELA was used in the calculations related to updating forest data and estimating different scenarios of timber production with and without constraints. In the study area, the annual volume of maximum sustainable cutting removal defined for the next 30 years was decreased by one-third due to restrictions. The presented approach could be used, for example, to assess timber availability at the landscape level. Future challenges include ensuring the compatibility of spatially explicit data obtained from different sources, identifying the feasibility of forest management operations in the restricted area, and incorporating near-nature forest management operations in the forest planning system in order to estimate the timber production. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1-4):134-143
This article demonstrates that the opportunity cost (return forgone) of cutting principles imposed by the Swedish forest policy is economically significant. The Swedish Forestry Act of 1979 recommends a management strategy for sustaining high yields of valuable timber referred to here as the Balance Strategy. However, the Forestry Act allows for a range of different forest management strategies. The Act establishes both a minimum cutting volume for a ten‐year‐period and a maximum final cut area referred to here as the Minimum and Maximum Strategies, respectively. These strategies were compared to a management plan, referred to as the Economic Strategy, for minimizing the opportunity cost for the forest owner. Based on data from a recent forest management plan, a simulation model was used to predict yields and economic returns for a period of one hundred years. The results show that at a 4% interest rate the Economic Strategy produces a gain of approximately 8200 SEK ha‐1. The Economic Strategy, however, emphasizes volume and its implementation results in a forest far different from that developed under the Balance Strategy, in which quality timber is also produced. The Economic Strategy may also have less favourable effects on biodiversity, conservation of the natural environment and the recreational value of the forest. 相似文献
15.
16.
17.
桉树工业原料林的投资经济效益与最佳经济轮伐期 总被引:4,自引:0,他引:4
在分析已有相关研究存在选取技术经济指标和利率随意性的基础上,运用经济效果评价动态分析法的净现值指标、内部收益率指标,对福建永安林业集团投资经营的巨尾桉工业原料林进行研究.结果显示:巨尾桉工业原料林最佳经济轮伐期为7年.7年主伐的巨尾桉工业原料林,净现值达到5 718.50元·hm-2,内部收益率达到18.09%,具有较好的经济效益.研究结果还表明投资桉树工业原料林的风险较高,影响桉树工业原料林经济效益最敏感的因子为木材价格和采伐成本:木材价格下降10%,内部收益率降低31.09%;采伐成本增加10%,内部收益率下降14.93%. 相似文献
18.
《Forest Ecology and Management》2007,238(1-3):280-292
We investigated the responses of forest birds to habitat changes following timber harvest by selection cutting in three northern tolerant hardwood forest stands using a before–after control-impact (BACI) type of experimental design. We observed only minor effects on the bird community associated with mature forests. Ovenbird (Seiurus aurocapilla) abundances declined by about 80–90% in two of the three harvested blocks. Black-throated blue warblers (Dendroica caerulescens) declined in abundance by about 70% on a single block 2 and 3 years post-harvest. Mechanical disturbance of the shrub layer [primarily Canada yew (Taxus canadensis)] was coincident to this decline. Several bird species that prefer early successional or shrubby habitats, such as veery (Catharus fuscescens), cedar waxwing (Bombycilla cedrorum), chestnut-sided warbler (Dendroica pensylvanica), magnolia warbler (Dendroica magnolia), American redstart (Setophaga ruticilla), mourning warbler (Oporornis philadelphia) and white-throated sparrow (Zonotrichia albicollis), benefited from selection cutting, with the timing of individual species’ responses related to changes in habitat structure and composition. Effects in one block were still evident 7 years after harvest. Guidelines that support a residual stocking target of 20 m2/ha should promote the retention of mature forest bird communities, including ovenbird, while still providing habitat for early successional bird species. 相似文献
19.
Ingolf Profft Martina Mund Georg-Ernst Weber Eberhard Weller Ernst-Detlef Schulze 《European Journal of Forest Research》2009,128(4):399-413
Wood products are considered to contribute to the mitigation of carbon dioxide emissions. A critical gap in the life cycle
of wood products is to transfer the raw timber from the forest to the processing wood industry and, thus, the primary wood
products. Therefore, often rough estimates are used for this step to obtain total forestry carbon balances. The objectives
of this study were (1) to examine the fate of timber harvested in Thuringian state forests (central Germany), representing
a large, intensively managed forested region, and (2) to quantify carbon stocks and the lifetime of primary wood products
made from this timber. The analyses were based on the amount and assortments of actually sold timber, and production parameters
of the companies that bought and processed this timber. In addition, for coniferous stands of a selected Thuringian forest
district, we calculated potential effects of management, as expressed by different thinning regimes on wood products and their
lifetimes. Total annual timber sale of soft- and hardwoods from Thuringian state forests (195,000 ha) increased from about
136,893 t C (~0.7 t C ha−1 year−1) in 1996 to 280,194 t C (~1.4 t C ha−1 year−1) in 2005. About 47% of annual total timber harvest went into short-lived wood products with a mean residence time (MRT) < 25
years. Thirty-one per cent of the total harvest went into wood products with an MRT of 25–43 years, and only 22% was used
as construction wood and glued wood, products with the longest MRT (50 years). The average MRT of carbon in harvested wood
products was 20 years. Thinning from above throughout the rotation of spruce forests would lead to an average MRT in harvested
wood products of about 23 years, thinning from below of about 18 years. A comparison of our calculations with estimates that
resulted from the products module of the CO2FIX model (Nabuurs et al. 2001) demonstrates the influence of regional differences in forest management and wood processing industry on the lifetime of
harvested wood products. To our knowledge, the present study provides for the first time real carbon inputs of a defined forest
management unit to the wood product sector by linking data on raw timber production, timber sales and wood processing. With
this new approach and using this data, it should be possible to substantially improve the net-carbon balance of the entire
forestry sector. 相似文献
20.
以吉林省三岔子林业局的森林资源为调查对象,针对限额采伐后近13 a的资源数据和森林资源变化状况进行分析,结果表明:实施限额采伐后,年采伐量与实施天保工程初期相比较下降了38.32%;森林覆盖率提高了2.04个百分点。幼龄林面积、蓄积比例分别下降了9.3和2.5个百分点;中龄林面积、蓄积比例分别增加了3.4和1.9个百分点;近熟林面积、蓄积比例分别增加了2.9和0.3个百分点;成熟林面积比例增加了1.5个百分点,蓄积比例下降了1.0个百分点;过熟林面积、蓄积比例分别增加了1.8和1.3个百分点。 相似文献