间伐林分的断面积生长模型研究

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。     

林分断面积生长模型研究评述

林分断面积生长模型是林分生长和收获预估模型的体系的主要组成部分。在对常用的新面积生长模型Ｒｉｃｈａｒｄｓ型和Ｓｃｈｕｍａｃｈｅｒ型分析的基础上,总结出断面积生长模型研究中应注意的４个问题;（１）选择的自变量应为３个,即立地质量指标、年龄和林分密度指标;（２）间伐林分模型应与未间伐林分模型同时考虑,进而详细介绍了用于间伐林分断面积预估的被压指数法;（３）间伐指标的构造需要伐前和后伐后的林分因子;（４     

长白落叶松林分断面积生长模型的研究

分析了理查德、逻辑斯蒂、单分子及冈珀斯生长方程之间的关系,以理查德方程为基础,研究了其它各方程的特点及性质。运用辽宁省长白落叶松林分观测数据,模拟了Richards等生长方程的林分断面积生长过程,以林分立地指数,疏密度为因变量,建立了多形长白落叶松林分断面积生长曲线模型。通过预测分析表明,Richards生长方程具有适应性强、精度高等特点。     

抚育间伐对人工落叶松断面积和蓄积生长的影响

以汪清林业局的20块人工落叶松为例,对间伐林分的断面积和蓄积进行生长趋势分析,用普雷斯勒公式计算林分的平均生长率,分析不同间伐强度对林分断面积和蓄积的影响,结果表明:间伐林分在间伐初期的断面积和蓄积小于未间伐林分,但随着林龄的增大,间伐林分断面积和蓄积向未间伐林分渐近;间伐强度越大,年平均生长率越大;方差分析表明,不同的间伐强度对林分断面积和蓄积生长的影响差异显著。     

思茅松人工林胸径断面积生长特点与初始抚育间伐期的确定

应用思茅松人工林解析木所获的基础数据,建立了其林木胸径断面积生长量的Logistic曲线回归方程:y=202.134/(1 45.92 e-0.5101 t),依据此回归方程的几何特征,对思茅松人工林取样林分的林木胸径断面积生长量、断面积连年生长量的变化特点作了分析。进而确立并论述了以林木胸径断面积连年生长量确定思茅松人工林初始抚育间伐期的方法。     

林分断面积生长模拟理论与技术研究

林分断面积是众多测树因子中的核心因子。文中对林分断面积生长规律及其模拟技术研究进展进行了综述, 分析了自然生长林分与间伐林分断面积生长的异同, 并重点从生长方程的选取、断面积模型的分类研制、研制途径及间伐指标、林分自变量及密度指标以及单木竞争指标等5个方面探讨了林分断面积模拟研究进展, 指出林分断面积生长模拟理论与技术领域存在的问题及未来研究重点, 以期为相关研究提供借鉴与参考。     

抚育间伐对辽东山区3种林型林分总断面积和总收获量的影响

利用几十年的定位观测数据,分析了抚育间伐对辽东山区红松人工林、天然次生蒙古栎林和人工诱导的阔叶红松林3种林型林分总断面积和总收获量的影响。结果表明:与对照区相比,抚育间伐没有提高红松人工林的林分断面积和蓄积总生长量,但极强度和强度间伐能提高红松人工林的林分断面积生长率。林分总断面积随着间伐强度的增加先升高后降低,各间伐强度均能提高林分总断面积,极强度间伐除外。抚育间伐能提高红松人工林林分蓄积生长率,弱度区除外;红松人工林林分总收获量随着间伐强度的增加先升高后降低,各间伐强度均能提高林分总收获量,中度间伐效果最好。抚育间伐能提高蒙古栎林林分断面积和蓄积总生长量、生长率以及林分总断面积和总收获量,各指标随着间伐强度的增加先升高后降低,中度间伐效果最好。抚育间伐能提高人工诱导的阔叶红松林林分断面积和蓄积总生长量、生长率以及林分总断面积和总收获量,林分断面积和蓄积总生长量、林分总断面积和林分总收获量随着间伐强度的增加而升高,林分断面积和蓄积生长率随着间伐强度的增加先升高后略有降低,强度间伐效果最好。可见,合理的间伐强度能够提高3种林型的林分总断面积和总收获量。     

基于非线性混合模型的落叶松云冷杉林分断面积模型

以吉林省汪清林业局金沟岭林场20块落叶松云冷杉样地为研究对象。首先选择传统的回归方法从4个常用的断面积模型中找出模拟精度最高的模型作为基础模型,利用基础模型及模拟数据构建非线性混合模型,考虑样地效应,采用SAS软件进行模拟,选择模型收敛及其对数似然值、AIC和BIC值最小的混合模型作为最优模型; 然后,在此基础上考虑断面积连续观测数据的时间序列相关性,并把间伐强度以哑变量形式考虑进去,再进行混合模型的模拟; 最后,利用验证数据对混合模型方法与传统的非线性回归模拟方法进行精度比较。结果表明： 林分密度指数作为自变量的Schumacher式的模拟精度最高,而考虑样地效应的混合模型模拟精度优于传统的回归模型方法; 一阶自回归误差结构矩阵模型在解释断面积的时间序列相关性时不仅提高了混合模型的模拟精度,而且能够很好地表达连续观测数据间误差分布情况; 同时考虑样地的随机效应、观测数据的时间序列相关性及间伐强度的混合模型模拟精度比传统的非线性回归方法模拟精度高。     

蒙古栎间伐林分和未间伐林分生长模型研究

以Richards和Schumacher模型为原型,利用地位级指数代替地位指数来反映林分的立地质量,通过选取不同的密度指标,分别拟合蒙古栎间伐、未间伐林分的断面积、蓄积量生长模型。结果表明:选用不同的密度指标直接影响着模型的预估效果,林分断面积生长模型选用林分密度指数作为密度指标时预估效果更好,且Schumacher模型要优于Richards模型;林分蓄积量生长模型选用林分断面积作为密度指标时预估效果更好,当认为模型中的渐近值参数只与立地质量相关、而与密度无关时,选用林分断面积作为密度指标的Richards模型要优于Schumacher模型,而在Schumacher模型渐近值参数中引入密度指标后,对林分蓄积量的预估精度又要略优于Richards模型。建议在研究蒙古栎断面积、蓄积量生长模型时,分别选用林分密度指数和林分断面积作为密度指标较好。     

福建柏林分断面积生长模型的研制

以福建柏林分为研究对象,以Korf理论生长方程为基础,根据非线性回归模型的特性,运用最优化理论的三大非经典算法之一的遗传算法来实现参数的求解,构建福建柏林分断面积生长模型。通过结果检验,其拟合效果的较好,理论值和实际值差异不显著,实际应用误差小,精度高,可运用于指导研究区福建柏林业生产实践。     

Dynamics of Crown Thinning and Mycobiota on Fallen Twigs of Mature Birches (Betula pendula) in Finland

The annual dynamics of birch crown thinning was studied by collecting fallen twigs monthly for two years. The detachment of birch twigs that had died during the summer was also followed. In addition, the fungi sporulating on the detached twigs were investigated by photomicroscopy to reveal morphological characters, and by DNA analyses to identify relationships between the fungi. The twigs that had died during the summer fell to the ground during the following winter and spring. Crown thinning, however, peaked in summer and early autumn. Altogether seven sporulating fungi were identified from the detached twigs. The most common fungus was Pleomassaria siparia (the teleomorph of both Prosthemium betulinum and P. asterosporum). The connection between crown thinning and fungi was not clear, but the results suggested that Pleomassaria siparia could be involved in the process.     

Accuracy and precision of crown profile,volume, and surface area measurements of 29-year-old Japanese cypress trees using a Spiegel relascope

The crown profile, volume, and surface area obtained from 25 trees in a stand of 29-year-old Japanese cypress (Chamaecyparis obtusa Endl.) using a Spiegel relascope were compared with those obtained by direct measurement after tree felling. In 17 of the 25 trees, the crown profile measured with the relascope was identical to the crown profile obtained by direct measurement. For the 17 trees, the mean relative errors of crown volume and surface area tended to be unbiased. On the other hand, the crown profiles obtained by the two methods were different in five of the 25 trees, while it could not been judged whether the crown profiles obtained by the two methods were identical or different in three of the 25 trees. However, for each group of five or three trees, the mean relative errors of crown volume and surface area were also unbiased. Moreover, for both crown volume and surface area, no significant differences were detected in variance of error among the groups of 17, five, and three trees. Therefore, the discrepancy between crown profiles obtained by the two methods for the five and three trees might be negligible in terms of the accuracy and precision of crown volume and surface area measurements. The standard errors for both crown volume and surface area were larger in each of the five and three trees than in the 17 trees. However, even for the five and three trees, the crown volume and surface area obtained using the relascope were more precise than those based on the assumption that crown form was a cone or paraboloid. We concluded that using a Spiegel relascope would enable us to obtain an accurate and precise crown profile, volume, and surface area of Japanese cypress trees for practical use, especially when the main objective of measurement is determining crown volume or surface area.     

Performance of full-sib families of Douglas-fir in pure-family and mixed-family deployments

A major objective of tree improvement programs is to identify genotypes that will perform well in operational deployments. Relatively little is known, however, about how the competitive environment affects performance in different types of deployments. We tested whether the genetic composition and density of deployments affect the performance of full-sib families of Douglas-fir (Pseudotsuga meniziesii), and whether traits related to crown morphology could help to explain differences in family performance under competition. Seedlings from eight families were planted in pure-family and three mixed-family composition treatments at high, medium, and low densities (11,954, 2988, and 747 trees·ha⁻¹, respectively). Height (HT), diameter at breast height (DBH), and volume·ha⁻¹ (VOLHA) were measured at ages 8 and 15 years. Significant differences were found among composition treatments in all traits other than VOLHA8 and significant interactions between composition and density treatments were found for all traits at age 15 years. Family ranks for DBH15 and VOLHA15 in pure-family treatments changed considerably among densities, but ranks were more stable for HT15. The performance of two mixed-family treatments differed significantly from the average performances of the same families in pure-family treatments for several traits. Differences in DBH15 among families in high-density, pure-family treatments could be explained in part by differences in crown morphology, with better performance among families with relatively narrow crowns, stout branches, and high leaf area relative to branch length. Our results suggest that the competitive environment has a considerable effect on family performance, and that incorporating crown morphology traits into selection criteria in tree improvement programs may lead to greater productivity of Douglas-fir.     

Branch mortality and potential litterfall from Douglas-fir trees in stands of varying density

Forest floor characteristics influence nutrient cycling and energy flow properties of forest ecosystems, and determine quality of habitat for many forest plants and animals. Differential crown recession and crown development among stands of differing density suggest that an opportunity may exist to control the input of fine woody litter into the system by manipulating stand density. The objective was to measure the rate of branch mortality among stands of differing density and to estimate the range in total per hectare necromass inputs. Although litter traps are reliable for estimating per hectare rates of litterfall, branch mortality dating on sectioned stems uniquely allows assessment of several other litterfall components: (1) individual tree contributions to total litterfall; (2) the amount of branch material released by mortality, regardless of whether the branches are shed to the forest floor; (3) the distribution of basal diameters characterizing the litterfall from a given tree and stand. Twenty-four trees were felled and sectioned on permanent plots that were part of a silvicultural study of stand density regimes in Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco.). Whorl branches were dissected out of bole sections to determine the dates of mortality, and a branch biomass equation was applied to estimate potential rate of litterfall. Periodic annual rates were expressed in four ways: (1) number of branches per tree; (2) mass of branches per tree; (3) mass of branches per unit of crown projection area; (4) mass of branches per hectare. For the growth periods investigated, larger trees and trees growing on denser plots tended to release a greater necromass through branch mortality. Average branch basal diameter generally decreased with increasing stand density. Annual branch mortality ranged from 33 to 430 g m⁻² crown projection area for individual trees, and from 236 to 1035 kg ha⁻¹ for individual plots. These rates approached the low end of the range of previously published fine litterfall rates for Douglas-fir. Rates on these plots were relatively low owing to the temporary delay in crown recession imposed by artificial thinning. A conceptual model of branch litter dynamics is presented to depict consistencies with crown development among stands managed under different density regimes.     

马尾松纸浆原料林对不同间伐强度的生长反应

马尾松(ＰｉｎｕｓｍａｓｓｏｎｉａｎａＬａｍｂ)生长快、适应性强,木材纤维含量4551%～6192%,纤维长度达44～6.5ｍｍ(周政贤等,1989),是造纸工业原料林发展的主要树种之一。但由于湖北省本地种源的马尾松在干形、材性、速生丰产性、耐瘠薄和抗病虫害等方面均不如南方种源的高州马尾松(李传志,1983),因而湖北及其它省市已从广东大量引种高州马尾松。为更好地掌握高州马尾松的生长规律,确定其造纸工业原料林的合理密度和经营管理措施,笔者对高密度高州马尾松纸浆原料林对不同间伐强度的生长反应进行了试验研究。1　试验地点与材料高州马尾松…     

Fertilization of lodgepole pine trees increased diameter growth but reduced root carbohydrate concentrations

Tree growth variables and more complex derived variables such as vigor index have all been linked to the ability of lodgepole pine (Pinus contorta var latifolia) trees to defend against insect herbivores, particularly mountain pine beetle (Dendroctonus ponderosae Hopkins, Coleoptera: Curculionidae). These variables are considered indirect measures of carbohydrate reserves. Trees with high vigor index values have high growth rates and are assumed to have high carbohydrate reserves. However, this critical assumption was untested for lodgepole pine. In this paper we evaluated the relationship between carbohydrate concentration and tree characteristics. We measured concentrations of root starch in 10 pure lodgepole pine stands of different ages in the Canadian Rockies which had been fertilized, thinned, fertilized and thinned or left untreated in a 2 × 2 factorial design. Both fertilization and thinning increased basal area increment while only fertilization increased lateral branch growth in the crown. Contrary to expectations, fertilization decreased root starch reserves although it increased basal area increment; thinning had no effect on root carbohydrates. Root starch reserves were positively related to basal area increment and vigor index in both fertilized and unfertilized plots, however, the best predictors of starch reserves were height-to-live-crown and cambial surface area below the live crown; starch reserves declined as both of these variables increased. These data suggest that large carbon sinks associated with long boles below the crown, and rapid growth of the crown and stem as a result of fertilization are detrimental to building starch reserves in the roots.