海岸林风害危险率评价的理论推导

本文在对间伐和风害之间关系的讨论和以往有关研究结果的基础上,确定了一种林木风害危险率的估计方法,用于评价间伐对林木风害的影响。这种对单株黑松及整个黑松林分的风害危险率估计,是根据风速廓线、枝条分布和透光分层疏透度(OSP)系数推导出来的。结果表明:如果枝条分布模型中的参数β等于单株树冠中风速廓线模型的衰减系数αs,参数H/D1.33可用于比较和评价对单株树木的风害危险率。这一原理也同样适用于整个林分,即用林分内风速廓线衰减系数α和透光分层疏透度(OSP)的分布中的衰减系数ν,结合D1.33估计和比较林分风害危险率。文中对间伐与非间伐单株黑松风害危险率进行了估计,得出了间伐两年后可以降低单株黑松风害危险率的结论;同时给出了确定林分风害危险率估计的过程图。图3参45。     

黑河森林生态站林内外主要气象因子月变化规律研究

目的:本研究在黑龙江黑河森林生态系统国家定位观测研究站五大连池风景区分站(以下简称景区分站)采用连续长期定位观测的方法测定蒙古栎林内、林外气象因子动态变化分析其差异特征,旨在揭示森林内小气候的月变化规律及森林对小气候的影响。方法:选取2018年1月、5月、8月和11月四个月份的观测数据,分别从温度、湿度、太阳辐射、风速等主要气象因子来探讨森林小气候的月变化规律。结果:(1)林内、林外月均气温变化趋势基本一致,林外温度月均值均高于林内,8月温度最高,1月温度最低;(2)林内外月均湿度变化趋势基本一致,林内湿度月均值均高于林外,8月湿度最高,5月湿度最低;(3)林外太阳辐射强度月均值始终高于林内,5月太阳辐射最高,1月太阳辐射最低;(4)林外风速月均值远高于林内,5月风速最高,1月风速最低。森林可以通过调节小气候具有优化环境的多重功能。结论:由于森林树冠对太阳辐射的吸收可以显著降低林内温度。太阳辐射穿透树木冠层进入林内,冠层的枝条和叶片对太阳辐射都有一定程度的阻挡,使得林内太阳辐射明显低于林外。森林树冠对风能够起到显著的阻挡作用,从而使得林外风速明显高于林内。而森林林冠层对地面进行覆盖,使林内比林外保持了较高的湿度,因而林内湿度又显著高于林外。     

马尾松近熟林的间伐效应

利用16-21年生马尾松近熟林间伐密度试验林的观测资料,探讨了不同间伐强度对林分生长与效益的影响。结果表明,不同间伐保存密度(450、600、750、900、1 036株/hm2)对林分生长、林分结构及材种规格均有显著影响。其中林分胸径、单株材积、冠幅随密度增大而减小,密度对树高生长无显著影响;不同间伐密度的林分蓄积量与出材量随着时间推移差异变小;间伐有利于提高大径级林木株数比率从而提高材种规格与效益。根据21年生马尾松人工林生长规律与效益评价,16-21年生近熟林间伐密度保存在600-900株/hm2效益较好。     

风对林木的影响

风除对森林造成了危害外,还对树木的生长、形态以及森林生态等产生影响。随着全球气候变化的发展,更多和更强的暴风出现的危险性日益增加。为了更好地理解风害对树木、林分和森林生态系统的影响,为森林经营管理提供依据,本文对近10年来国际上有关风对林木影响内容进行归纳总结。结果表明,风对林木影响的研究主要在以下几个方面取得了重要的进展：1)风与林木的空气动力学关系;2)树木在风力荷载下其适应性的生长机理;3)树木对风的生理响应：4)森林风害的危险评估。所有这些研究大都在人工用材林中进行的。此外,本文还介绍了该研究领域需要开展的其它研究,如1)天然林或天然次生林的风害研究;2)风害形成的林窗和森林动态研究;3)风害对森林生态主要过程的影响研究;4)．风害与森林管理研究。图3参61。     

杉木林间伐强度自然稀疏与结构规律研究

在杉木人工林抚育间伐强度试验20年中,研究不同间伐强度林分自然稀疏的变化,揭示自然稀疏株数与林分密度和立地条件的关系,对杉木林密度管理图自然稀疏线数学方程M=k1·k2作出检验,提出不同间伐强度林分直径、树高和林冠结构等.自然稀疏研究表明,CK和弱度间伐自然稀疏起始期高峰期早,稀疏量大,稀疏过程具连续性,按其稀疏量可分为轻微稀疏期、剧烈稀疏期和延续稀疏期等3个阶段,若不加以人为干预,自然稀疏将是一个漫长的过程.中度和强度间伐稀疏起始期和高峰期之间呈间歇性、稀疏阶段性不明显.研究发现,林分密度和立地条件对枯死木株数均有重要作用,但密度比立地条件更重要.杉木林密管图自然稀疏线数学方程经检验,相对误差3.91%,精度较高;对其用于不同间伐强度和不同地位指数林分的实用性检验结果,CK相对误差5.23%,其他检验项目相对误差均＜5%,为容许试验误差,实用性较强.研究揭示了不同间伐强度林分径级和树高级分布规律等.研究还得出不同间伐强度林分枝下高、林冠长度和林冠相对高度的生长差异、变化动态及其与林龄增长的各种相关规律,并分别提出其与林龄和单株材积定期生长量相关的数学模型.     

沙岸黑松海防林防护成熟期及更新年龄的研究

在对山东省黑松海防林进行全面踏查的基础上，应用典型调查和定位观测相结合的方法，开展了沙体岸黑松海防林的调查研究。采用数量化理论Ⅰ的方法，对黑松海防林立地质量进行了数量化评价，划分出11种立地类型；并采用系统聚类法，将研究区的黑松海防林划分为3种林分生长类型；其中生长类型Ⅰ的林分生长表现最好，生长类型Ⅱ的次之，生长类型Ⅲ的最差。在综合分析黑松海防林防护成熟和数量成熟的基础上，提出黑松海防林的防护成熟期；生长类型Ⅰ为33-57a，生长类型Ⅱ为14-32a，生长类型Ⅲ为13-28a；确定黑松海防林的更新期；生长类型I为33-57a，生长类型Ⅱ为23-32a，生长类型Ⅲ为21-28a；确定黑松海防林的合理更新年龄；生长类型Ⅱ为32a，生长类型Ⅲ为28a。     

海岸带木麻黄林窗套种巨尾桉生长与降风效果分析

以福建惠安县崇武半岛海岸木麻黄林带为研究对象,探讨木麻黄林内的林窗套种巨尾桉的林分生长效果,开展了复层林结构的林带防风效能观测。结果表明,块状套种巨尾桉后生长较快,4年树高平均可达8.75 m,胸径9.95 cm,并形成异龄复层林。该林分平均可降低风速81.35%,这对改善林带结构,提高林分防护效能十分有利。     

杉木林冠层的动力效应及动能传递规律的研究

根据连续定位测定数据,应用空气动力学和生态动力学原理探讨了杉木人工林林冠层的动力效应及动能的传输规律.结果表明:密度2000株/(104m2)、林分平均高度16 m、平均胸径15.5 cm、叶面积指数8、冠层厚度9 m、郁闭度0.9的杉木林,其零平面位移长度11.15~11.98 m,冠层粗糙度2.32~2.53 m,林冠上表面乱流切应力0.135 N·cm-2,枝叶阻力系数0.367,摩擦速度0.339m·s-1,冠内混合长度0.12 m,相对湍流强度0.7;由于林冠的存在,枝叶对气流的阻滞作用使风速廓线发生形变,在杉木林内离地面11.15 m高度上,风速随高度的变化呈对数规律,在此以下高度符合指数法则,林冠内风速削减因子1.98;乱流切应力和动能从林冠上表面传输到林冠下表面时,乱流切应力削弱70%,动能削弱90%.乱流切应力和动能在林冠内传递变化规律与林分结构特征有关,尤其与林冠内湍流性质和温度层结影响关系极大.     

兴安落叶松原始林、渐伐林降水截留特征对比分析

通过对大兴安岭北部地区兴安落叶松原始林和渐伐林降水截留特征的观测表明,兴安落叶松原始林和渐伐林的林冠截留量与林外降雨量均呈幂函数关系;两种林地对林外降雨量的截留能力基本相同;研究表明,兴安落叶松渐伐林在经过多年的自然恢复后,林冠对降水的截留作用可恢复到经营前水平。     

用林分生长过程表计算间伐重复期的理论分析——论雷林隆缘桉间伐重复期的方法

林分生长过程表是研究各项测树因子随年令变化的规律,不同林分类型的生长过程表,反映不同立地条件与营林措施情况下,林分自然发展的历史进程;间伐重复期是林分自疏密度 P>0.8,进行间伐后.至恢复到原来 P 所需要的年期。因此,在组织林业生产上,林分生长过程表为计算和确定间伐重复期提供理论根据。我们自1963年编制广州白云山马尾松林生长过程表,1975年编制汕头地区韩江林场杉木林生长过程表,1977年编制海南岛东木麻黄海岸防护林生长过程表以来,对简     

Integrating the risk of wind damage into forest planning

Wind is the major abiotic risk factor in Finnish forests. Therefore, tools that help managers to assess the risk of wind damage are required. This study developed simple regression models for predicting the critical wind speed needed to uproot Scots pine, Norway spruce and birch trees at the stand edges in Finnish conditions, using the characteristics of the retained forest both downwind and upwind stands as predictors. Using information on the prevailing wind conditions in the region, the critical wind speeds were converted into probabilities of wind damage, from which a mean risk index was calculated. The mean risk index was used as an objective variable in heuristic optimisation. The results of minimizing the mean risk index were compared to other objective variables such as minimal height differences between adjacent stands. The residuals of the regression models of critical wind speeds were small, especially in Scots pine and birch. Increasing tree height of the downwind stand or area of the upwind stand (gap size) decreased the critical wind speed regardless of tree species, whereas increases in the dbh/height ratio of the downwind stand increased the critical wind speed. The shelter effect of upwind stand height was stronger in Norway spruce than in other tree species, whereas the effect of tree height of the downwind stand was larger in Scots pine and birch. Minimization of the mean risk of wind damage within forest landscapes led to smooth and non-fragmented landscape structures in terms of tree height. Incorporating even-flow constraints into the planning model led to a slight increase in the mean risk of wind damage. Of the surrogate methods for risk assessment minimization of height differences between adjacent stands performed well but not equally well as minimization of the mean risk index.     

The effects of fragmentation on the susceptibility of a boreal forest ecosystem to wind damage

The clear cuts and seedling stands can speed up winds and may trigger blowdown at the edges of neighbour stands. Therefore, the height contrast of the neighbour stands and fragmentation at landscape level could be used to indicate the susceptibility of windthrow. In this study, we studied how forest fragmentation affects the susceptibility of a boreal forest ecosystem to wind damage, both at patch and landscape level based on theoretical computations. For this purpose we generated, based on real stand inventory data of a Finnish forest ecosystem, different landscape configurations of Scots pine and Norway spruce forests using Monte Carlo simulation. Thereafter, we applied a mechanistic wind damage model to predict the wind speeds needed for wind damage at forest edges. The fragmentation metrics of Contrast-Weighted Edge Density with three different height dissimilarity calculation methods were used to analyze the fragmentation at the landscape level.     

浅析北京延庆康庄风沙危害区造林技术

荒漠化已成为威胁人类生存与发展的主要问题之一。北京市延庆县康庄地区是风沙进入北京的咽喉要道之一,康庄风沙危害区治理工程取得了显著的成效。文章主要从整地、选择造林树种、栽植、先进技术的应用以及后期抚育管理等方面介绍了康庄风沙危害区的造林技术。     

Climate change and the probability of wind damage in two Swedish forests

We simulated how possible changes in wind and ground-frost climate and state of the forest due to changes in the future climate may affect the probability of exceeding critical wind speeds expected to cause wind damage within one northern and one southern study area in Sweden, respectively. The topography of the study areas was relatively gentle and the forests were dominated by Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.). Using estimated changes in the net primary production (NPP) due to climate change and assuming a relative change in the site productivity equal to a relative change in NPP, we simulated possible future states of the forest under gradual adjustment of the site index in response to climate change using the model The Forest Time Machine. Global climate change scenarios based on two emission scenarios and one general circulation model were downscaled to the regional level. The modified WINDA model was used to calculate the sensitivity of the forest to wind and the probability of wind damage for individual forest stands for the periods 2011–2041 and 2071–2100 and for a control period 1961–1990. This was done while taking into account effects on stability of the forest from expected changes in the occurrence of ground frost. Increasing sensitivity of the forest to wind was indicated for both study areas when adhering to recommended management rules of today. Adding also a changed wind climate further increased the probability of wind damage. Calculated probabilities of wind damage were generally higher in the southern study area than in the northern one and were explained by differences in wind climate and the state of the forests, for example with respect to tree species composition. The indicated increase in sensitivity of the forest to wind under the current management regime, and possibly increasing windiness, motivate further analysis of the effects of different management options on the probability of wind damage and what modifications of Swedish forest management are possibly warranted.     

Effect of wind damage on the habitat suitability of saproxylic species in a boreal forest landscape

Many forest-dwelling species are dependent on deadwood. Sources of deadwood include competition- and senescence-related mortality of trees, and various damages. This study described a methodology for predicting the effect of wind damage on the amount of deadwood and suitability of the forest for saproxylic species. The methodology was used in a forested boreal landscape of 360 ha to analyze the effects of wind damage on the habitat quality for 27 groups of saproxylic species differing in their requirements for the species, size and decay stage of deadwood objects. A reference plan maximized net present value (MaxNPV) while others either minimized or maximized height differences between adjacent stands. Maximization of height differences resulted in high amount of wind damage and deadwood while minimizing height differences minimized wind damage and the amount of damage-related deadwood. The fourth plan maximized the average habitat suitability index (HSI) of the 27 groups of saproxylic species. The plans were compiled with and without even-flow harvesting constraints for three 10-year periods. Maximization of height differences between adjacent stands resulted in higher HSI values than obtained in the MaxNPV plan or in the plan than minimized height differences between adjacent stands. The average HSI of shade-demanding species correlated negatively with the amount of harvested timber. No strong correlations were found for light-demanding and indifferent species.     

Stand-level wind damage can be assessed using diachronic photogrammetric canopy height models

Key message

Diachronic photogrammetric canopy height models can be used to quantify at a fine scale changes in dominant height and wood volume following storms. The regular renewal of aerial surveys makes this approach appealing for monitoring forest changes.

Context

The increasing availability of aerial photographs and the development of dense matching algorithms open up new possibilities to assess the effects of storm events on forest canopies.

Aims

The objective of this research is to assess the potential of diachronic canopy height models derived from photogrammetric point clouds (PCHM) to quantify changes in dominant height and wood volume of a broadleaved forest following a major storm.

Methods

PCHMs derived from aerial photographs acquired before and after a storm event were calibrated using 25 field plots to estimate dominant height and volume using various modeling approaches. The calibrated models were combined with a reference damage maps to estimate both the within-stand damage variability, and the amount of volume impacted.

Results

Dominant height was predicted with a root mean squared error (RMSE) of 4%, and volume with RMSEs ranging from 24 to 32% according to the type of model. The volume impacted by storm was in the range of 42–76%. Overall, the maps of dominant height changes provided more details about within-stand damage variability than conventional photointerpretation do.

Conclusion

The study suggests a promising potential for exploiting PCHM in pursuit of a rapid localization and quantification of wind-throw damages, given an adapted sampling design to calibrate models.

     

一次飑线对阔叶红松林危害的记录

红松(Pinus koraiensis)是我国东北林区的珍贵树种,2002年被正式列为黑龙江省二级保护植物,它的优异材质和独特的价值被世界所公认。红松是山地树种,在世界上分布不广,我国东北是其自然分布区的中心地带。阔叶红松林是小兴安岭南坡的地带性植被,是伊春林区的主要森林类型。2005