RELATIONSHIPS BETWEEN LARCH GROWTH AND FOREST SITE FACTORS

Dahurian larch (Larix gmelinii Rupr.) Rupr is one of the dominant species in bothnatural and man-made forests in northeast China.Effects of site factors,including topography,soilproperties and nutrient elements(P,Ca,K,Mg,Mn,Zn,Cu,Ag,Co and Ni)on the growth of larchwere analyzed in detail,qualitatively and quantitatively.The ordination technique was used to groupthe site factors and to classify sites for larch.Analysis indicated that height growth,diameter(DBH)and volume of the larch varied among site types and this will be of theoretical and practical signifi-canee in developing larch plantations.

Study on Mosuo's Sacred Natural Sites of Mountainous Forest and Protection of Biological Diversity in Yongning-Lugu Lake Area

With Mosuo's sacred natural sites of mountainous forest in Yongning-Lugu Lake area as the research subject,by using the method of ecology,the vegetation type in this area was initially identified.The control sample plot of the same vegetation type at similar altitude and in similar soil condition would be selected and compared with the sample plot in sacred natural sites at length,so as to quantitatively analyze the protection of biological diversity in the perspective of ecological system.It showed that under the circumstance of the damage of ecological environment,complete natural vertical pattern was preserved thanks to sacred natural sites of mountainous forest established by reason of traditional religion and culture.The results of research and quantitative analysis showed that compared with the control sample plot of the same vegetation type,sacred natural sites were high in biological diversity and the species composition of plant community in sacred natural sites was closer to that of primitive forest.The result of quantitative analysis also indicated that sacred natural sites played a remarkable role in protecting vegetation and this protective function became more remarkable if the altitude was higher.And human were reminded to pay close attention to the preservation and protection function of sacred natural sites to natural ecological system at high altitude.

Site Quality Evaluation for Mixed, Uneven-aged, Natural Forest Dominatedby Korean Pine in Northeast China

Six site types of Korean pine(Pinus koraiensis) forest, Mongolian oak type, Yezo spruce type, Korean spruce type, Amur linden type, Ribbed birch type and Manchurian ash type, are easily found on the south slope of Xiaoxing’an Mountains. The analysis results of H-A and H-Dbh relationships by site type showed that height growth of Korean pine dominant or codominant stems in natural stands is not directly related to its age but is directly related to its diameter, which closely accords with the Chapman-Richards equation(Relativity coefficients more than 0:8668). A method for evaluating site quality using height and diameter of dominant or codominant tree independent of tree age is examined. There are signifi-cantly differences in site quality of Korcan pine among six site types above. The site index was highest on Manchurian ash type, and lowest on Mongolian oak type. Differences of site index with a reference dbh of 40 cm between highest and lowest sites can reach 11 m in maximum., 7 m in average, respectively. Other rationales of the H-D method were discussed.

Site classification of the eastern forest region of Daxing'an Mountains

Based on the plot data from the investigation and the theory of forest ecology and ecological system,the site classification of the eastern forest region of Daxing’an Mountains was made by mean of mathematical method. The main factors were slope, thickness of soil layer, slope position and slope aspect. Grades of slope were used as the division standard for site type group. The slope aspect, slope position and thickness of soil layer were used as the division standards for site type. Altogether 7 site type groups and 15 main site types were determined the region. It provided reliable fundamental basis for the reasonable management and planting design in the area.

Growth models and site index table of natural Korean pine forests

According to the growth characteristics of natural Korean pine (Pinus Koraiensis) forests, 6 equations such as Chapman-Richards equation, Logistic equation, Power equation, and so on were selected to ftt for the growth modeIs for Korean pine forest. The growth models were developed based on 208 random trees and 24o dominant trees. Results show that the Chapman-Richards equation is the best model for estimating tree height by age and DBH, while the Parabola equation is fittest for predicting DBH by age or estimating age from DBH. The site index table of Korean pine forest was compiled by using the proportional method with the Chapman-Richards equation as the guide curve and vaIidated by accuracy test.

SITE CLASSIFICATION FOR PROTECTIVE FOREST AFFORESTATION ON THE COAST OF CHINA

Land for protective forest on the coast has special site conditions, and site classification is the scientific basis for seaboard afforestation. The site classification system on the coast zone and islands of China may be classified into five levels-site region (sub - region), district, class, group, and type. The land division for afforestation is carried out by the principle of enviornmental heterogeneity among regions, sub-region and district on large scale, according to the difference of air temperature, moisture and type of coast geomorphy. It may be classified into 7 regions, 12 sub-regions and 55 districts. The medium and small scaled division for site class, group and type, subdivided in a site district, are based on medium topography, topographic climate, micro - relief and soil conditions.

Application of site-specific biomass models to quantify spatial distribution of stocks and historical emissions from deforestation in a tropical forest ecosystem

Allometric equations developed for the Lama forest, located in southern Benin, West Africa, were applied to estimate carbon stocks of three vegetation types：undisturbed forest, degraded forest, and fallow. Carbon stock of the undisturbed forest was 2.7 times higher than that in the degraded forest and 3.4 times higher than that in fallow. The structure of the forest suggests that the individual species were generally concentrated in lower diameter classes. Carbon stock was positively correlated to basal area and negatively related to tree density, suggesting that trees in higher diameter classes contributed significantly to the total carbon stock. The study demonstrated that large trees constitute an important component to include in the sampling approach to achieve accurate carbon quantification in forestry. Historical emissions from deforestation that converted more than 30% of the Lama forest into cropland between the years 1946 and 1987 amounted to 260,563.17 tons of carbon per year（t CO2/year） for the biomass pool only. The study explained the application of biomass models and ground truth data to estimate reference carbon stock of forests.

Impact of site management on changes in soil carbon after afforestation:A review

Afforestation and forest management can increase carbon stocks and account for emission reduction according to the Kyoto Protocol. Site management has important effects on the accumulation of soil carbon after afforestation. This review examines the effects of site management, including soil disturbance, fertilization, thinning, weed control, harvesting and controlled burning, on soil carbon dynamics in plantations, based on recent published results. Soil disturbance can enhance soil carbon losses, with whole ploughing causing the most and disking the least loss of soil carbon. The effects of fertilization and thinning on soil carbon are in- conclusive. Weed control can prevent the carbon input from above-grotmd residue and root turnover and increase soil temperature and soil erosion, which in turn reduces the amount of carbon on the soil surface. Soil carbon decreases with the increase of harvest- ing intensity and the retention of harvest residue can significantly enhance the accumulation of carbon in the soil. Controlled burning before afforestation has a short-term benefit for soil carbon, but it is not beneficial to the sequestration of soil carbon over the long term. Future studies should focus on investigating the long-term impact of site management practices, especially soil fertilization and thinning, on carbon, identifying the response of major functional pools of soil carbon to management practices, understanding the dy- namics of soil nitrogen pools and their role in long-term soil carbon sequestration, as well as quantifying soil carbon processes under different climate conditions and site management scenarios using models.

Geostatistical Approach for Site Suitability Mapping of Degraded Mangrove Forest in the Mahakam Delta, Indonesia

As part of operational guidance of mangrove forest rehabilitation in the Mahakam delta, Indonesia, site suitability mapping for 14 species of mangrove was modelled by combining 4 underlying factors—clay, sand, salinity and tidal inundation. Semivariogram analysis and a geographic information system (GIS) were used to apply a site-suitability model, while kriging interpolation generated surface layers, based on sample point data collection. The tidal inundation map was derived from a tide table and a digital elevation model from topographic maps. The final site-suitability maps were produced using spatial analysis technique, by overlaying all surface layers. We used a Gaussian model to adjust a semivariogram graph in order to help to understand the variation of sample data values, and create a natural surface layer of data distribution over the area of study. By examining the statistical value and the visual inspection of surface layers, we saw that the models were consistent with the expected data behavior;therefore, we assumed that interpolation has been carried out appropriately. Our site-suitability map showed that Avicennia species was the most suitable species and matched with 50% of the study area, followed by Nypa fruticans, which occupied about 42%. These results were actually consistent with the mangrove zoning pattern in the region prior to deforestation and conversion.

混交对杉木和山杜英混交林生长、结构和生产力的影响

为探究杉木(Cunninghamia lanceolata)与山杜英(Elaeocarpus sylvestris)的混交效应,以景德镇枫树山林场20年生杉木纯林、山杜英纯林和杉木-山杜英混交林为研究对象,每种林分类型设置3种坡位(上坡、中坡和下坡),分析树种混交对林分生长的影响,并分别探究混交效应对立地条件和生境因子的响应。结果表明:混交林蓄积较预期蓄积增加5%,表现略微增产;混交林中杉木蓄积较杉木纯林增加15%,混交林中山杜英蓄积较山杜英纯林减少13%。相对于纯林,两树种直径分布特征对混交的响应呈相反趋势,混交林中杉木直径分布峰值向高阶移动,而混交林中山杜英直径分布峰值向低阶移动。混交林及其纯林粗根直径-胸径的异速生长分析表明,混交林中杉木生长侧重于树干生长,而山杜英生长侧重于根系生长;无论林型和树种,坡位由上到下,林木生长会侧重于树干生长。杉木-山杜英混交效应与地位指数呈显著负相关(P<0.05),土壤有效磷是混交林生长的主要限制因子。杉木与山杜英混交可促进林分生长,且混交林对较差立地条件有更好的适应性。

包含哑变量的大兴安岭天然白桦林碳密度模型

以内蒙古地区牙克石林业管理局的大兴安岭天然白桦林(Betula platyphylla)为研究对象,利用198块样地数据分析天然白桦林林分碳密度与各林分变量之间的关系,建立碳密度预测基础模型,同时将立地条件(草类白桦林、杜鹃-越桔白桦林、榛子白桦林)作为哑变量引入到预测模型中,对不同林型的林分碳密度进行预测,为林业研究中碳密度模型的构建以及森林碳汇工作提供思路和方法。结果表明,天然白桦林林分碳密度基础模型决定系数(R^(2))为0.703,均方根误差(RMSE)为8.615 t/hm^(2),赤池信息量(Akaike information criterion,AIC)为841.206,贝叶斯信息量(Bayesian Information Criterion,BIC)为851.071。引入立地条件哑变量后,R^(2)有所增大,最大达到0.818,RMSE均小于等于8.241 t/hm^(2),说明模型具有较好的稳定性,预估参数较为精确。哑变量模型的AIC均小于等于541.431,BIC均小于等于550.320。哑变量模型能够反映不同立地条件下碳密度的变化,在模型的拟合和检验方面都显示适合于研究地区林分碳密度的预测,为天然白桦林碳密度估算提供参考。

The composition and diversity of natural regeneration of tree species in gaps under different intensities of forest disturbance

The positive ecological interaction between gap formation and natural regeneration has been examined but little research has been carried out on the effects of gaps on natural regeneration in forests under different intensities of disturbance.This study evaluates the composition,diversity,regeneration density and abundance of natural regeneration of tree species in gaps in undisturbed,intermittently disturbed,and disturbed forest sites.Bia Tano Forest Reserve in Ghana was the study area and three gaps each were selected in the three forest site categories.Ten circular subsampling areas of 1 m2 were delineated at 2 m spacing along north,south,east,and west transects within individual gaps.Data on natural regeneration<350 cm height were gathered.The results show that the intensity of disturbance was disproportional to gap size.Species diversity differed significantly between undisturbed and disturbed sites and,also between intermittently disturbed and disturbed sites for Simpson’s(1-D),Equitability(J),and Berger-Parker(B-P)indices.However,there was no significant difference among forest sites for Shannon diversity(H)and Margalef richness(MI)indices.Tree species composition on the sites differed.Regeneration density on the disturbed site was significantly higher than on the two other sites.Greater abundance and density of shade-dependent species on all sites identified them as opportunistic replacements of gap-dependent pioneers.Pioneer species giving way to shade tolerant species is a natural process,thus make them worst variant in gap regeneration.

用于立地质量评价的天然林生长模型构建方法

【目的】Fu等提出了一种基于立地生产潜力的天然林立地质量评价方法,该方法从理论上解决了如何结合环境和林分因子对不同立地类型及其生产力进行定量分析。本研究主要围绕该方法中的林分生长模型开展研究,以吉林省森林资源为研究对象,系统给出生长模型的建模方法,例如模型选型标准、模型参数化、参数估计和模型评价等。【方法】假定林分为等株生长,利用数学理论推导出林分断面积模型中直接或间接含有年龄情形时林分断面积连年生长量计算公式,并给出断面积连年生长量与林分断面积指数是否为单调函数的判别准则;基于哑变量方法分析不同分类变量对断面积生长的影响,即模型参数化;利用改进的最小二乘法求解参数化的林分断面积生长模型参数;以吉林省3634个面积为0.06 hm^(2)的固定样地的4次连续观测数据为实例,构建林分断面积生长模型。【结果】本研究提出的方法能有效判断断面积连年生长量与林分密度指数是否为单调函数,从而为断面积模型选型提供捷径;建模时考虑模型参数化既能有效解释变量各等级之间的差异程度,又能提高模型预测精度;提出的改进最小二乘法能有效求解含哑变量的模型参数。【结论】本研究所给出的生长模型构建方法可为Fu等提出的天然林立地质量评价方法提供技术支撑。

西北地区红桦天然次生林立地质量评价

在陕西、宁夏、甘肃、青海等地设置红桦天然次生林临时样地85块,以年龄-树高、胸径-树高数据为依据,选取常用的9个树木生长模型拟合导向曲线,采用相对优势高法编制立地指数表和立地形表,并采用2种方法对4个不同地区的立地质量进行比较,实现对西北地区红桦天然次生林立地质量的科学评价。结果表明,立地指数和立地形的最优导向曲线方程分别为H=18.073/{1+exp[-(A-22.571)/9.144]}、H=19.793/{1+exp[-(D-12.218)/6.588]};确定基准年龄为40 a,基准胸径为20 cm,指数级距为2 m,划定10~20 m共6个立地质量等级,编制立地指数表和立地形表。检验结果表明,两表的卡方值均小于临界值,落点检验精度分别为95%和97.5%,达到编表精度要求,均能够良好地反映红桦天然次生林立地质量。2种方法在对4个地区的立地质量评价中表现出较好的一致性,其中陕西火地塘林场立地质量最优,宁夏二龙河林场次之,青海北山林场和甘肃洮坪林场立地质量一般。

立地及密度对杉木林分生长及材种结构的影响

为探讨立地及密度对广西融江流域杉木人工林生长及材种结构的影响,以不同立地条件下的杉木人工林为研究对象开展间伐试验,于林分13年生时进行生长量调查和分析。结果表明:林分树高、胸径、蓄积量、中径材出材率、规格材出材量随地位指数提高而增加,且地位指数级越高时,地位指数提高一级所带来的树高和中径材出材率增幅越大;地位指数越高,大径材形成的时间越早,大径材出材率越高;该林龄阶段(13年生),林木主要分布于14、16、18 cm三个径阶内,且随林分密度减小,≤14 cm径阶林木株数占比减小,≥20 cm径阶林木株数占比增大,小径材出材率减小,中径材出材率增大;随林分密度减小林分蓄积量显著减少,但规格材出材量增加。

平原地区森林康养基地建设适宜性评价指标体系研究

随着人们生活水平的提高和健康观念的普及,森林康养已成为越来越多人追求的休闲方式。平原地区作为我国土地类型的一种,其特有的地理环境和生态资源为森林康养基地提供了独特的发展潜力。在实际开发过程中,如何科学评价平原地区森林康养基地建设适宜性对策划合理开发具有重要意义。本研究采用文献分析法作为主要研究方法。通过分析平原地区的特点,将平原地区的特点与森林康养基地建设相结合,并参考相关文献对比分析各类评价指标,提炼出适合平原地区的评价指标体系。共包含十个指标,覆盖了森林面积、地表水质量、森林选址等多个方面,能够全面反映平原地区森林康养基地建设的各个方面。

基于竞争与立地效应的湖南栎类天然林冠幅模型

【目的】分析立地因子和竞争因子对冠幅生长的影响,构建含立地因子和竞争因子的混合效应湖南栎类天然林冠幅预测模型,为栎类天然林科学经营决策提供理论依据。【方法】以51块湖南栎类天然林样地的1 429株栎类林木为研究对象,筛选对冠幅影响显著的因子,将显著性因子按照标准分级、组合,构成竞争类型和立地类型;从10个基础模型中筛选出最优模型;应用k-means聚类方法将初始竞争类型聚类成竞争类型组;将立地类型和竞争类型组作为随机效应加入最优模型,构建含竞争和立地效应的湖南栎类天然林冠幅模型。【结果】对冠幅影响显著的因子包括海拔、坡度、坡位、坡向、土壤类型、相对断面积(R_(S))、简单竞争指数(C_(LH))和大于对象木断面积之和(B_(AL)),立地因子显著性顺序为海拔>坡度>坡向>坡位>土壤类型,竞争因子中R_(S)与冠幅呈正相关,而C_(LH)、B_(AL)与冠幅呈负相关;最优基础模型为异速生长模型(有截距),R^(2)为0.534 8;将筛选的3个竞争因子按照标准分级、组合构成竞争类型,加入基础模型构建含竞争类型的混合效应模型,R^(2)升至0.583 5;应用k-means聚类将初始竞争类型聚类成17个竞争类型组,作为随机效应加入基础模型,R^(2)升至0.749 2;将立地类型作为随机效应再加入模型,构建基于竞争和立地混合效应的冠幅模型,R^(2)升至0.841 6,相对基础模型提升了57.36%。【结论】含竞争因子和立地因子的湖南栎类天然林冠幅模型具有较好的拟合效果及预测精度。因此,本研究所构建的冠幅模型可以很好地预测湖南栎类天然林的冠幅,可为研究栎类天然林生长、经营管理以及更新森林资源调查数据库提供支持。

华北典型针叶混交林林下更新影响因素分析

天然更新在维持森林稳定性与森林群落动态变化方面发挥重要作用,探究其相关影响因素,为促进研究区林下更新提供科学依据。以庞泉沟自然保护区云杉华北落叶松混交林为对象,基于灰色关联度方法从林分结构、立地条件两方面探究影响混交林林下更新的关键因素。结果表明:1)华北落叶松与云杉的混交林中,云杉幼苗351株、幼树172株,华北落叶松仅有幼苗39株、幼树36株,云杉的更新能力较强;2)华北落叶松、云杉混交林天然更新的影响因子关联度排序为树种组成>海拔>大小比>角尺度>林分密度>林龄>坡向>郁闭度>混交度>坡度;整体上看,天然更新对林分结构和立地因子均有显著响应,其中树种组成是影响天然更新的最主要林分非空间结构因子,海拔是影响天然更新的最主要立地因子,大小比、角尺度是影响天然更新的主要林分空间结构因子。因此,在调整未来林分时,可通过优化林分结构来促使云杉、华北落叶松混交林天然更新,从而提高林分稳定性。

基于机器学习的厚覆盖土层建筑场地类别评价

针对因测量等误差对等效剪切波速计算的影响而造成的场地类别容易因单个因素稍有变化即发生的类别改变问题,从江苏省盐城地区收集了大量厚覆盖土层情况下的标准贯入值、深度、剪切波速等相关现场试验数据,利用机器学习方法进行训练建模,研究多特征值模型解决厚覆盖土层情况下场地分类问题的能力。结果表明:随机森林模型的分类精度在加入“等效变异系数”后可达97.7%,且其泛化能力以及对样本总体的判断能力均优于支持向量机模型,该模型为厚覆盖土层建筑场地类别的判断提供了一种新的方式。将二次判断结果与勘探报告结果对比,结果证明该随机森林模型可用于场地分类变化问题的二次判断,为避免工程现场在类似情况下出现过于保守的判断提供了可靠的依据。

湖南栎类天然林自稀疏边界线及影响因素研究

为确定湖南栎类天然林自稀疏边界线的最优统计方法以及影响栎类自稀疏的主要因素,以湖南省225块栎类天然林长期监测样地为研究对象,运用最小二乘法、分位数回归法和随机前沿方法拟合栎类天然林自稀疏边界线,采用现实林分死亡率对3种统计方法进行比较与验证,依据自稀疏边界线对现实林分的自稀疏状态进行判别,并对未稀疏和已稀疏样地的立地因素和森林结构因素进行方差分析。结果表明,基于分位数回归方法(分位数值等于0.95)拟合的自稀疏边界线更加接近于栎类天然林的最大密度临界值,其拟合效果优于最小二乘法和随机前沿方法;栎类自稀疏边界线的斜率为-1.063,截距为10.232;海拔、坡度、Pielous指数和高径比是影响栎类天然林自稀疏速率和起始时间的显著因素。构建的自稀疏边界线可以准确反映栎类天然林最大密度与林分平均直径的异速生长关系,可以为湖南栎类天然林生长演替和森林抚育研究提供参考。