树木、林内、林冠上与森林区风速廓线研究

One of the most important and frequently studied variable in forests and the most basic element in governing transport processes of airflow is wind speed. The study of wind profile, defined as the change of wind velocity with height, and wind velocity are important because of tree physiological and developmental responses. Generally, wind profiles above the ground or at a canopy surface follow classical logarithm law, but wind profiles in a single tree and in a forest stand are not logarithmic. This paper summarizes the results of wind profile studies within a single tree, in a forest stand, above the forest canopy and in a forest area from recent research in a coastal pine forest. The results demonstrate that: 1) wind profiles with in a single conifer tree crown showed an exponential function with height, 2) wind profiles in forest stands were able to be expressed by attenuation coefficient of wind, 3) wind profiles over a forest canopy could be determined using profile parameters (friction velocity, roughness length and displacement), and 4) for a forest area, the extreme wind speed could be predicted reasonably using the methods developed for the design of buildings. More research will be required to demonstrate: 1) relationships between wind profiles and tree or stand characteristics, 2) the simple methods for predicting wind profile parameters, and 3) the applications of wind profile in studies of tree physiology, forest ecology and management, and the detail ecological effects of wind on tree growth.     

迎风向防风林带宽对风速减弱的作用

通过在日本扎晃人学水压力工程实验室开展的埃菲尔型非循环风洞试验,研究了防风林阻尼变化及不同林带宽的整体阻力系数,阐明在迎风向上防风林带宽对风速减弱的作用.以二维雷诺时均N-S方程-k-ε吨扰动闭合模型数字地研究了不同防风林带宽的流量场变化.结果表明,防风林对风的阻力随林带宽增加而增加,但是整体阻尼系数略微降低.整体阻尼系数Cd、防风林带宽W和林高H之间满足方程Cd=kd(W/H)-b(kd,b:常数).数字模拟结果表明,防风林带宽度明显影响最小风速值及其位置.随着防风林带宽度的增加,风速下降15%-22%.     

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.     

间伐对黑松海岸林风害的影响——基于风害危险率评价的理论推导

本文在“海岸林风害危险率评价的理论推导”(Journal of Forestry Research, 2002, 13(4))一文的基础上,对1997年12月经四种间伐处理的黑松海岸林进行了连续四个生长季的风害调查,同时,对黑松海岸林内与林外风速廓线和林分透光分层疏透度的分布也分别进行了观测。应用在这些观测数据,依据“海岸林风害危险率评价的理论推导”文中获得的风害危险率评价方法,对单株树木及林分的风害风险率进行了评估,结果表明,单独依据平均直径与结合风速廓线和林分结构的风害风险率,构成了评价海岸森林风害的重要指标。不同间伐强度和风害发生率之间的关系表明,在间伐初期林分的稳定性有所下降,这可能是由于林冠粗糙度和风负载的增加及周围树木的保护效应的减少而引起的。然而,经过一段时间后,间伐处理能够促进林分生长,从而提高了林分的稳定性和对强风的抵抗力。在本试验观察过程中只发现了强风对林冠的损害,而即使是在间伐海岸林外风速达到30.2 m·s-1的条件下,也没有发现风倒或风折。本次研究中获得的结果表明,尽管在间伐之初风害的概率增加了,但是,间伐作为一种最为有效的林分管理方法,可以成为保持海岸林健康、稳定的一种长期经营管理策略。图3表4参19。     

Impact factors on fine root seasonal dynamics in Fraxinus mandshurica plantations

Fine root turnover plays important roles in carbon allocation and nutrient cycling in forest ecosystems. Seasonal dynamics of fine roots is critical for understanding the processes of fine root turnover. From May to October 2002, soil core method was used for estimating the seasonal pattern of fine root (diameter < 1 mm) parameters (biomass, specific root length (SRL) and root length density (RLD)) in a Manchurian ash (Fraxinus mandshurica) plantation located at the Maoershan Experiment Station, Heilongjiang Province, northeast of China. The relationships of fine root biomass, SRL and RLD with available nitrogen in soil, average soil temperature per month in 10 cm depth and soil moisture content were analyzed. Seasonal variation of fine root biomass was significant (P < 0.05). The peak values of fine root biomass were observed both in spring and in autumn, but SRL and RLD were the highest in spring and lowest in autumn. Specific root length and root length density were higher in spring and summer, which means that fine root diameter was thinner. In autumn, both parameters decreased significantly due to secondary incrassation of fine root diameter or the increase of tissue density. Seasonal dynamics of fine roots was associated with available nitrogen in soil, soil temperature in 10 cm depth and moisture content. Fine root biomass has a significant relationship with available NH₄ ⁺-N in soil. Available NO₃ ⁻-N in soil, soil temperature in 10-cm depth and moisture content have a positive correlation with fine root biomass, SRL and RLD, although these correlations are not significant (P > 0.05). But the compound effects of soil available N, soil temperature and soil moisture content are significant to every root parameter. The variations of these three root parameters in different seasons show different physiological and ecological functions in different growing periods. Translated from Scientia Silvae Sinicae, 2006, 42(9): 7–12 [译自: 林业科学]     

Wind profiles in a coastal forest of Japanese black pine (Pinus thunbergii Parl.) with different thinning intensities

Simultaneous measurements of windspeed were made outside and inside a pine (Pinus thunbergii Parl.) coastal forest with different thinning intensities. Synchronously, optical stratification porosity (OSP), which is defined as vertical distribution of the proportion of sky hemisphere not obscured by tree elements inside a forest stand, was estimated using hemispherical silhouettes in each treatment area. Based on the observations, the frequency distribution of velocity, turbulence intensity, wind profile, and the corresponding relationships of these respective parameters with the vertical forest structure (OSP) were examined and compared among the treatment areas. A normal distribution of wind velocity was observed at the lower zone of the forest stand in all treatment areas. The turbulence intensity, the highest value of which was found near the canopy, changed greatly with height, wind velocity, and treatment, and decreased with windspeed and increased with the thinning intensity. It was found that the exponential relationship between windspeed and height could be used to describe the wind profiles within the canopy of the coastal forest. The results demonstrate that the attenuation coefficient of the wind profile corresponds to the grade of thinning intensities. The wind patterns in a coastal forest with different thinning intensities are related to the vertical forest structure, particularly, wind profiles within the canopy are closely correlated with the distribution of OSP. The results indicate that wind profiles can be estimated simply based on the measurement of OSP with a very high coefficient of determination. Reciprocally, the estimation of OSP can also be obtained from the measurement of wind profile. Portions of this paper were presented at the 111st Annual Meeting of the Japanese Forestry Society. Appreciation is due to Professor Masashi Yamamoto, Mr. Kenji Sakioka, Mr. Takahiro Yoshida, Mr. Hirotaka Yamazaki, Mr. Yasunori Hasegawa and the members of the Sabo Division of the Faculty of Agriculture of Niigata University for their help in collecting the field data and in constructing the observation towers.     

湖南省生态林业建设发展方向及特征展望

新世纪中国林业发展的总体战略思路——“三生态”道路，为湖南生态林业建设指明了方向。“贯彻科学发展观、实施人与自然协调的可持续发展战略，建设生态湖南”是贯穿湖南生态林业建设的主旨。在综合调研的基础上，对湖南生态林业发展走向进行了深入的分析，对其在发展过程中的特点作了创造性的展望，并从多个角度对生态林业建设的意义和成果作了积极的评价，认为湖南生态林业建设最终将促进生态与经济的协调发展，为繁荣湖南经济作出重要贡献。     

Consideration of strong winds, their directional distribution and snow loading in wind risk assessment related to landscape level forest planning

Forest planning needs to assess various risks that may cause economic or other losses to forest owners. This study aimed at developing a wind risk assessment method, which considers the occurrence and directional distribution of strong winds, and the effect of snow loads and support by neighbouring trees on the expected wind damage. For this purpose, regression models were developed for predicting the critical wind speeds needed to uproot Scots pine, Norway spruce and birch trees at the downwind stand edges in Finnish conditions under unfrozen soil conditions, based on the characteristics of both downwind and upwind stand, and additional snow load on tree crowns. Furthermore, a risk index was developed for the forest landscape, based on the critical wind speeds of stands, occurrence of strong winds and their directional distribution, and the prevailing snow loading in the region. Thereafter, the mean risk index was used as an objective variable in heuristic optimization in forest planning to demonstrate how the optimal cuttings and the spatial layout of the landscape may change depending on the wind and snow conditions and the support that trees provide to each other. Our results show that the directional distribution of strong winds shape the optimal forest landscape structure markedly. Consideration of snow loading in the calculation of critical wind speeds increased the mean risk clearly and produced slightly more aggregated landscape structures in terms of tree height. The consideration of support that neighbouring trees provide to each other had minor effects. To conclude, the consideration of risk of wind induced damages in forest planning calculations clearly affects the selected cutting strategies and impacts the spatial layout of the landscape.     

Measurement of diurnal changes in stem and branch diameters using strain gauges

The applicability of a strain gauge for monitoring the diurnal changes of tree stem diameters and the differences in diurnal shrinkages between a stem and branches were investigated. Estimates of stem diameter changes obtained by a strain gauge were compared with changes obtained by a differential transformer. Patterns of strain changes obtained by a strain gauge were remarkably similar to the changes in the tree trunk diameter. This results demonstrated that a strain gauge is an effective technique for examining the behavior of changes in tree trunk diameter. Diurnal changes of diameter at various parts of the a tree were also measured with the help of several strain gauges. Diurnal strain changes of a stem and branches showed similar patterns of shrinkage during the day and swelling at night. However, the precise times at which the branches had their maximum and minimum strains differed from those observed in the stem, and the maximum rates of the strain changes lagged behind the stems in a day. These results lead us to believe that there is a time lag in the supply of water, which is required for compensating the water deficit between the stem and its branches. A part of this paper was presented at the 105th Annual Meeting of Japanese Forestry Society (1994).     

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.     

福建光泽九龙坑不同坡向天然次生林演替规律的研究

通过对福建光泽九龙坑不同坡向天然次生林的林分组成和生境的调查,研究主要乔灌木树种在不同坡向林分中的分布规律,分析出不同坡向林分的天然演替趋势,为人工促进天然更新提供科学依据。     

Response of vegetation and birds to severe wind disturbance and salvage logging in a southern boreal forest

Vegetation and birds were inventoried on the same plot before and after a severe windstorm in 1999 disturbed a mature black spruce (Picea mariana)–jack pine (Pinus banksiana) forest in northern Minnesota. Following the storm, another plot was established in an adjacent portion of the forest that was salvage-logged. Birds were inventoried on both plots through 2002. The original unsalvaged plot was prescribed-burned in 2004, but vegetation was surveyed through 2003, and through 2005 on the salvaged plot. We examined the effects of wind disturbance by comparing the pre-storm bird and vegetation communities with those developing afterwards through 2002 and 2003, respectively, and the effects of salvage logging by comparing vegetation and the bird community on the unsalvaged plot with those in the salvaged area. Wind reduced the canopy of the forest by over 90% with a temporary increase in the shrub layer, mostly resulting from tip-ups. Several plant species, including jack pine and beaked hazel (Corylus americana), appeared temporarily in the ground layer (<1 m height), but did not persist through 2003. Quaking aspen (Populus tremuloides) root sprouts were abundant in 2001, but decreased dramatically by 2003. Delayed mortality of tipped trees resulted in reduction of the shrub layer to pre-storm levels, and release of advanced regeneration black spruce and balsam fir (Abies balsamea). Bird species using the forest changed from dominance by canopy-foraging species to ground-brush foraging species, with an overall increase in bird diversity. Salvage logging resulted in significant reduction in coarse woody debris, and successful recruitment of jack pine seedlings. Quaking aspen sprouts were nearly 30 times more abundant in the salvage-logged area compared to the unsalvaged control. Ruderal species, especially red raspberry (Rubus ideaus), fringed bindweed (Polygonum cilinode), and several sedges (Carex spp.), were significantly more abundant after salvage logging. The bird community, on the other hand, was greatly diminished by salvage logging, with a reduction in diversity, density, and overall richness of species.     

略论平原农区高级林网化的几个问题

通过对平原农区多年来营造农田林网的试验研究和大量典型调查,结合本地科研成果及外地经验,提出了平原农区高级林网化的概念及标准,并总结出平原农区建立高级林网化应注意的几个关键问题,为平原农区营建高级农田林网提供了参考。     

植被类型变化对民勤地区土壤肥力的影响

民勤是受干旱,风沙威胁最为严重的地区之一,综合治沙是改变该区环境的重要手段之一,其中植物固沙是综合治沙的关键。文中就几种沙生植物群落对土壤肥力影响的研究结果表明：不同植被类型对土壤肥力的影响不同,Ｎ、Ｐ、Ｋ的转化速度也不同。     

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。     

南宁市速生桉发展最大面积的论证研究

发展速生桉在一定程度上有效缓解了广西区乃至我国木材紧缺的局面。以南宁市林地布局及空间分析为基础,综合考虑扣除公益林后的林地面积以及速生桉生长的立地条件,确定全市发展速生桉的最大理论面积为38．46万hm^2。根据南宁市五大类培育树种的规划比例以及林地保护利用规划成果,提出速生按建议发展最大面积为31．92万hm^2。并提出合理调整林种、树种结构,增强森林的综合功能及效益等建议。     

Impacts of climate change on timber production and regional risks of wind-induced damage to forests in Finland

In this work, we studied the impacts of climate change on timber production and regional risks of wind-induced damage to forests in Finland. The work employed: (i) national level forest inventory data, (ii) current baseline climate (1961–1990) and changing climate scenario (FINADAPT A2, 2001–2099), (iii) a forest ecosystem model (SIMA), (iv) a mechanistic wind damage model (HWIND), and (v) currently applied forest management recommendations as a baseline. The results showed that the timber production will increase significantly towards the end of this century under the changing climate, and in a relative sense the most in Northern Finland. At the same time, the share of Norway spruce (Picea abies L. Karst.) is expected to decrease, especially in southernmost Finland, mainly favoring the presence of birch (Betula spp.), but also Scots pine (Pinus sylvestris L.), when no species preference is given in management. As a result, the proportion of forest area in the two lowest critical wind speed classes (i.e. winds of 11–14 and 14–17 m s⁻¹) will decrease in the autumn (birch without leaves) throughout Finland. However, in summertime (birch is in leaf) the proportion of forest area with such critical wind speeds will even increase in southernmost Finland. Even though, in summertime the risk of damage should be on average relatively low throughout Finland due to a lower occurrence of such wind speeds compared to the windiest time of the year (i.e. from autumn to early spring). The return period of critical wind speeds of 11–17 m s⁻¹ is today about every two years in southernmost Finland. In Northern Finland, the critical wind speeds needed for wind damage are, on average, higher due to the larger share of Scots pine and on average lower height to breast height diameter ratios of trees compared to the south. To conclude, the climate change will affect clearly the forest growth and dynamics and, thus increase the need to manage forests more often and/or heavily (e.g. thinning, final felling), which in addition to species preference, will affect the risks of damages. The consideration of the risk of wind damage is crucial especially in Southern Finland when adapting forest management to the changing climate. This is because the unfrozen soil period is expected to increase significantly in Finland, which decreases tree anchorage during the windiest time of year.     

林火火头前方气流温度场和速度场的测量、数据采集和处理系统的研究

该文介绍了一个用于一林业火头前方温度场和速度场的测量及数据采集和处理系统。该系统的主要特点是 :(1)可以同时测量多个点在同时刻的温度和风速 ;(2 )克服温度和风速波动的影响 ,误差小 ;(3)实时数据采集 ,便于监测 ;(4)数据后处理方便。实际使用说明 ,该系统测量准确可靠     

Acoustoelastic birefringence effect in wood II: influence of texture anisotropy on the polarization direction of shear wave in wood

Ultrasonic shear waves were propagated through the breadth direction of a wood beam which was subjected to a bending load such that it was in a plane-stress state. The oscillation direction of the shear waves with respect to the wood beam axis was varied by rotating an ultrasonic sensor, and the relationship between the shear wave velocity and the oscillation direction was examined. The results indicate that when the oscillation direction of the shear wave corresponds to the tangential direction of the wood beam, the shear wave velocity decreases sharply and the relationship between shear wave velocity and rotation angle tends to become discontinuous. When the oscillation of the shear waves occurs in the anisotropic direction of the wood beam instead of in the direction of principal stress, the shear wave velocity exhibits a peak value. In addition, the polarization direction was found to correspond to the direction of anisotropy of the wood beam according to the theory of acoustoelastic birefringence with respect to plane stress. This indicates that when the acoustoelastic birefringence method is applied to stress measurement of wood, it is appropriate to align the oscillation direction of the shear wave with the principal axial direction of anisotropy in order to carry out ultrasonic measurement.     

廉江次生季雨林群落类型与多样性研究

粤西廉江市谢鞋山的次生季雨林47种树种按其综合优势比值大小分类共计有16个植物各落类型，其中大多数是以荔枝为第一建群种的群丛组，受人为活动的频繁干扰，4种物种多样性指数值均较低，对这些群落加强就地保护具有重要的实现意义。