共查询到17条相似文献，搜索用时 265 毫秒
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以可变密度全林分预估模型理论为指导,探讨建立了樟子松人工林地位级指数和林分密度指数经验方程,结合林分密度动态预估模型,建立了樟子松人工林断面积预估模型和蓄积量预估模型。经检验模型预测值与实测值误差为3.64%,模型精度96.37%。 相似文献
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北京落叶松人工林全林分模型研建 总被引：2，自引：0，他引：2
以北京森林资源一类调查中侧柏的数据为基础,以Rechards方程为模版,通过spss统计建模工具进行拟合,建立了包括落叶松的树高模型、立地指数、林分密度、断面积指数、全林收获模型、林分生长模型在内的全林分模型。林分生长模型保持了与收获模型的相容性,在此基础上利用林分生长模型,可根据某一时期的林分收获量预知未来某一时期的林分蓄积。通过检验证明,此北京落叶松人工林全林分的林分生长模型有很强的适用性,为有关林业部门确定最优密度指数、立地指数等因子来改善落叶松的经营方式提供了依据。 相似文献
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以北京山区油松为研究对象,利用可变生长率法构造油松全林分年生长预测模型,并通过似乎不相关联立估计全林分生长模型的参数。研究结果表明:利用可变生长率法建立全林分年生长预测模型符合林分发展的规律,解决了林分生长预测的阶段无偏性,同时为林分经营者提供了林分年变化量,而且通过似乎不相关联立估计得到的全林分生长模型参数,没有明显的估计偏差,从而提高了参数估计的有效性。 相似文献
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杉木人工林可变密度收获表的编制 总被引：2，自引：0，他引：2
根据固定标准地的调查材料,并对林分的密度指数、相对植距指标、生长空间指标进行分析表明：以带密度指数的扩展Richards生长函数为基础模型编制杉木人工林可变密度收获表效果最佳。 相似文献
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利用杉木人工林现场实际造材样木以及木材价格、生产成本、税费等技术经济指标测算单木纯收益,并建立单木货币预估模型。以年龄、地位指数、林分密度为辅助变量,选择Korf理论生长方程构建杉木人工林全林分模型,结合单木货币预估模型按经营类型编制杉木人工林林分货币收获表。应用林分货币收获表,既可预估林分在各种年龄时的木材产量及与材积有关的林分因子,同时还体现了林分货币收获量,在森林资源经营、资产化管理和资产评估中有实际应用价值。 相似文献
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《中南林业科技大学学报(自然科学版)》2019,(8)
为解决给大面积林分生物量估算提供估算模型、减少外业工作量等问题,以黄山松为研究对象,构建了兼容性林分生物量模型及全林分收获模型,采用混合蛙跳算法结合交叉建模和检验技术求解林分生物量模型参数,并确定全林分收获模型参数。结果表明,建立的兼容性林分生物量模型的平均系统误差(2.381%)、平均相对误差绝对值(7.964%)均在在±10%内、拟合效果较好,基于立地质量等级为哑变量的地位指数曲线模型、断面积模型、林分蓄积量模型等拟合效果较好、适用。与常规全林分经验收获模型相比,研究先建立可变密度林分模型,再经相对密度模型确定林分平均收获量,并编制黄山松林分生物量经验收获表。研究内容在监测森林生物量和碳储量、制定节能减排和造林计划等方面具有重要的生态环境意义。 相似文献
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林分密度指数是基于林分层次,对于量化林分密度与生长情况所提出的一项指标,其研究的核心是掌握林分的自然稀疏规律。在森林决策经营问题上,林分生长收获预估研究是最重要的一环,但其中林分生长收获模型的建立及预测的准确性一直是个难题,考虑众多林分生长指标后,林分密度成为了林分生长预估模型的核心问题。对于多种多样的林木种类和复杂的林分立地条件,林分密度指数的应用范围也受到限制,本文将就林分密度指数研究现状展开论述。 相似文献
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间伐林分的断面积生长模型研究 总被引：3，自引：0，他引：3
利用Richards和Schumacher模型对人工落叶松和杉木林分进行断面积模型的拟合,结果表明:两种模型在同时选择单位面积株数或同时选择林分密度指数作为自变量时,Schumacher式都比Richards式拟合和预估效果好。Richards式用林分密度指数比用单位面积株数的拟合和预估效果明显要好,Schumacher式用林分密度指数比用单位面积株数拟合效果略好。在生产实践中,由于单位面积株数容易测定,而Schumacher形式比较简单,建议用来预估林分的断面积,并可作为间伐和未间伐林分的兼容模型。 相似文献
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On the basis of nine Norway spruce (Picea abies (L.) Karst.) and ten European beech (Fagus sylvatica L.) thinning experiments in Germany, for which both residual and removed stock had been registered first during 1870, I scrutinize
how moderate and heavy thinning from below (B-, C-grade) affects the production of merchantable volume compared with light
thinning (A-grade). In relation to A-grade, cumulative merchantable volume (CV) of B- and C-grade amounts in average to 103–107%
in juvenile and to 97–102% in mature Norway spruce stands. The corresponding findings for European beech are 101–106% and
94–102%. CV of individual stands varies between 89% and 130% for Norway spruce and 73% and 155% for European beech (CV of
A-grade = 100%). These findings are substantiated by the relation between stand density (SDI) and periodic annual increment
(PAI). On the B- and C-grade plots of spruce and beech, respectively, SDI was reduced down to 41–91% and 31–83% of the A-grade.
When SDI is reduced in young stands, PAI follows a unimodal curve. Norway spruce’s PAI culminates in 109% if SDI is reduced
to 59%; European beech’s PAI culminates in 123% when density is reduced to 50%. Whereas Norway spruce’s growth reacts most
positively on thinning under poor site conditions and with increment reduction on favourable sites, European beech behaves
oppositely. With stand development the culmination point of the unimodal relation moves towards maximum density, so that in
older stands PAI follows the increasing pattern, which is the left portion of a unimodal curve. A model is presented which
apparently unifies contradictory patterns of stand density–growth reactions by integrating relative stand density, average
tree size and site fertility effects, and makes the findings operable for forest management. 相似文献
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Li Xue 《Scandinavian Journal of Forest Research》2014,29(7):664-668
Most traditional studies of mean tree mass (MTM)– density relationships focus on crowded stands, without considering stands characterized with canopy gaps. We developed a model to estimate MTM of closed and unclosed forest stands based on stand density index (SDI). Data were obtained from eight forest stands in China to test the generality of this model. MTM was accurately expressed in terms of SDI by combining the equations for SDI and Yoda's model, and exponents of the MTM–SDI relationship ranged from –2.23 to 1.93. Compared with density, SDI is a better predictor of MTM, regardless of the degree of canopy closure in the stands. 相似文献
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We examined 5-year basal area growth of nearly 2600 trees in stem-mapped plots at five locations differing in site characteristics, species composition, and management history on the Olympic Peninsula in Western Washington, USA. Our objectives were to determine if internal edges, the boundaries within the stand between components of the variable-density thinning, influenced individual tree growth, and whether incorporation of individual tree local competition indices in growth prediction models could account for treatment and edge effects. Treatment significantly affected tree growth at all sites, with trees in the thinned matrix displaying on average over 25% greater basal area growth than trees in unthinned patches. Proximity to canopy gaps created as part of the variable-density thinning increased basal area growth of trees in the thinned matrix by nearly 11%. In addition, growth of trees close to skid trails was 11% greater than trees located away from the trails. Past thinning history, and its effect on initial stocking rate, appeared to affect the magnitude of the edge effects. Blocks that had received earlier commercial thinnings, and thus had lower stocking at the onset of the study, displayed lower growth responses than previously unthinned blocks. Including local competition indices in the models generally reduced growth prediction error; however, the indices examined did not fully account for treatment or edge effects. Our results suggest that not accounting for internal edges in spatially complex stands could result in errors in projected growth of trees, although these edge effects are highly variable. Failure to account for the effects of internal edges could affect not just estimates of future stand yield, but also projections of future stand structure. 相似文献
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油松人工林叶面积指数与其生物量及生长因子关系的研究 总被引：2，自引：1，他引：2
选取内蒙古大青山区30a生油松人工林作为标准地,研究了其叶面积指数与生物量之间的关系及叶面积指数与各相关生长因子之间的关系,结果表明:1)油松单株各龄叶的叶面积与其叶生物量均呈正相关直线;油松叶面积指数与单位样地面积叶生物量关系可模拟为:y=k-aEXP(-bx)。整个生长季叶生物量达到最大时的叶面积指数变动范围为10.75~16.19。2)油松单株各龄叶面积与总叶面积的关系可模拟为y=aEXP(-b^xk)。3)林分叶面积指数与其胸径的关系,经比较分析y=aEXP(-b/^xk)(x为平均胸径,y为叶面积指数)的模拟效果最好。叶面积指数随着平均胸径的增大而逐渐减小直至最后达到稳定。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(5):457-469
The efficiency gains when harvests are determined using the Faustmann approach instead of Maximum Sustained Yield (MSY), Forest Rent or some silvicultural rules were studies. The analysis was based on a variable-density stand growth model and computations over all admissible combinations of initial stand age and basal area for Finnish Norway spruce and Scots pine sites. Following MSY or Forest Rent led to a major reduction in the economic value of especially highly stocked stands. Finnish silvicultural recommendations (an example of silvicultural rules) encouraged production of higher than optimal quality timber. Applying Forest Rent, MSY or silvicultural recommendations led to respective reductions of 63%, 30% and 13% in the value of a typical conifer forest at a 4% rate of interest. The results also showed that an increase in the rate of interest may lengthen the ongoing rotation if the initial state falls outside the optimal path initiated at bare land. 相似文献