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.     

The essential oil components of Cinnamomum cassia: an analysis under different thinning models of plantation Pinus massoniana

Thinning is an important activity employed in forest management. To date, studies have mainly focused on the effects of thinning on the growth of trees during the same thinning period. In this study, plantation Pinus massoniana Lamb. near maturity were thinned at varying intensities and an economically important species, Cinnamomum cassia Presl., was planted beneath the thinned canopy. The aim of the study was to explore the effects of the extent of thinning on the essential oil content and its components of C. cassia in different parts of the plant, as well as the economic feasibility of the P. massoniana–C.cassia management model. Thinning significantly reduced the oil yield in the bark and branches of C. cassia, but hardly impacted the oil yield from C. cassia leaves compared with pure C. cassia forest(CK). Among the different thinning treatments, both light(T.4) and extensive(T.1)thinning reduced the oil yield of C. cassia bark and new branches. The concentrations of the main aldehydes differed in different parts of the plant and were affected by the extent of thinning. The influence on cinnamaldehyde in the bark was minor, but was much greater in the branches and leaves. Both the oil yield and content of cinnamaldehyde showed that moderate(T.3) thinning was more favorable than other thinning models. These results not only provide a potentially promising model for the transformation of low–yield artificial pure forests of P. massoniana in the future, but also offer a reference for the management of artificial mixed stands.     

Natural regeneration of oriental beech(Fagus orientalis Lipsky)trees in canopy gaps and under closed canopy in a forest in northern Iran

For developing nature-based silvicultural practices in a beech forest to promote, abundance, height,vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies.A systematic 50×50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies.Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps.Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy.Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps.Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured.The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration.The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.     

Effects of thinning on microsites and natural regeneration in a Larix olgensis plantation in mountainous regions of eastern Liaoning Province, China

In order to understand the effects of thinning on microsite conditions and natural regeneration in the larch plantation, thinning experiment was conducted in a 40-year-old Larix olgensis plantation in Qingyuan County in eastern Liaoning Province, China in 2003-2004 Five thinning treatments （0%, 10.2%, 19.8%, 29.7% and 40.3% thinned） were designed on the same site. After thinning, canopy openness and the microsite conditions such as photosynthetic photon flux density （PPFD）, soil moisture content, and soil temperature were measured in one growing season. Meanwhile, the investigation of natural regeneration was conducted at the end of the growing season. The results showed that the canopy openness increased with the increase of thinning intensities. PPFD and soil temperature and soil moisture content in different soil layers were positively relative with canopy openness after thinning. The richness of regenerating tree species did not significantly increase （p=0.30） after one growing season since thinning, but the regeneration density and frequency of tree species increased significantly （p〈0.05）. In addition, the number of regenerating tree species increased, and the increment was correlated with the characteristics of iudividual tree species. The increasing percentage of regenerating seedlings of the shade-intolerant tree species was more than that of shade-tolerant tree species. Among the investigated regeneration species, the biggest response of seedling emergency to the canopy openness was Phellodendron amurense. This paper confirmed the following conclusions： after thinning, the variety of regenerating tree species was correlative with the characteristics of regenerating tree species, and the distribution of unthinned trees and the site conditions in the investigated larch plantation were the additional factors influencing, the regeneration.     

Forest pasturing of livestock in Norway: effects on spruce regeneration

Forest pasturing of free-roaming livestock is a common practice in many parts of the world, but knowledge on how it affects tree regeneration in boreal forests is lacking. We mapped tree density, livestock site use and accumulated damage to young trees of commercial interest(Norway spruce, Picea abies L. Karst.) on 56 clearcuts inside and outside a fenced forest area used for livestock pasturing in Ringsaker, Norway. Inside the fence 56±1.8% of spruce trees were damaged compared to 37±3.4% outside. Proportion of damaged spruce trees was positively related to cattle use of the clearcut, but not so for sheep. On the most intensively used clearcuts, four out of five trees were damaged. The density of deciduous trees was five times lower inside compared to outside of the fence(varying with plant species). While livestock grazing may reduce resource competition in favour of spruce, the current animal density clearly is impeding forest regeneration in the study area.     

Surface wildfire in conifer broad-leaved forests of the Hyrcanian region of Iran: short-term effect on regeneration and damage to trees

Wildfires in recent years have resulted in degradation and damage to the Hyrcanian forest ecosystems in Northern Iran.This study was carried out to investigate fire damage to trees and changes in regeneration in early-season growth after wildfires in the Golestan Province.For this purpose,a random sampling plan was used,with 60 circular plots(each plot is 1000 m2) for each stand and 240 circular(25 m2) plots for regeneration within the burned and unburned areas,respectively.In each plot,habitat factors were recorded,including crown canopy percentage,forest stratum,herb-layer cover percentage,species,diameter at breast height,tree and regeneration quality,and quantity of seedlings and saplings.Our results showed that bark is an important factor for fire resistance in Hyrcanian forests.The Persian ironwood and European yew has the highest and lowest fire resistance;as broad leave species are more resistant than needle leaf species.Density of regeneration in unburned area was higher than burned area,and statistical analysis showed significant differences for all species between two areas.Fire effects on sapling were different among species which indicates sapling has different resistance to fire.Forest floor fuel,season,stand composition and microclimate have more effects on fire severity while environmental factors,regeneration and management practices shaping future composition stands.     

Estimating Pinus palustris tree diameter and stem volume from tree height,crown area and stand-level parameters

Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height （dbh） and merchantable stem volume （V） using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height （H） and crown area （CA）. Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predic- tions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.     

An impacts of logging operations on understory plants for the broadleaved／Korean pine mixed forest on Changbai Mountain, China

Natural regeneration of tree species is important to the sustainability of native forest ecosystems in the temperate zone of northeast China. This study compared the densities and heights of seedlings and the diversities of shrubs and herbs on three sites of logging operations: log-skidding trails (LST), logging gaps (LG) and log landing sites (LLS). Sites undisturbed by logging gaps operations were sampied as control. The species, counts and height of tree seedlings and the species, counts, height and percentage coverage of shrubs and herbs were recorded in the field. The highest density and greatest height of regeneration trees were observed at LG and LST. The effects of LST on the densities of broadleaved trees were greater than those of coniferous trees. The difference in seedling density between LLS and control was significant (p=0.05). There was no significant difference in average seedling height for all the tree species between the disturbed sites and control. There were more shrub and herb species at the disturbed sites than at control. The diversity of understory plants at LG was the highest among all the sites. LST and LLS were different in shrub diversity, so were LLS and control. Both LG and LLS were different from control in herb diversity. Active measures need to be taken on the operation sites to protect the coniferous trees and the diversities of understory plants for sustaining the structure and composition of the broadleaved-Korean pine mixed forest on Changbai Mountain of China.Since different operation sites have different effects on different tree species, site-dependent actions must be taken to assure the regeneration of ecologically important tree species.     

火干扰对天然红松林结构和演替过程的影响

Investigations on charcoal in the soil, fire-scarred trees, stand composition, forest structure as well as regeneration status were carried out in the natural broad-leaved/Korean pine (Pinus koraiensis) forest after fire disturbance at Liangshui Nature Reserve on the mid-north of Xiaoxing‘an Mountains from 1990 to 1992, and the ecological effects of fire disturbance on the formation and succession of this kind of forest were analyzed according to the survey results. The average depth of charcoal in the soil was related to the timing of the fire. According to the characteristic of fire-scarred trees, the dynamic map of the fire behavior was drawn onto the topographic map. It showed that the dimension and extent of the fire disturbance was closely related with site conditions. Fire disturbance only led to a significant difference in stand composition and diameter class structurefor the stands at different locations, rather than completely destroying the forest. After fire disturbance, the horizontal community structure was a mosaic of different patches, which were made up of different deciduous species or different sizes of Korean pines, and the succession trend of each patch was also different. In the sites with the heavy fire disturbance, the intolerant hardwood species were dominant, and there were a large number of regenerative Korean pine saplings under the canopy. In the moderate -disturbed sites, the tolerant hardwood species were dominant, and a small number of large size Korean pines still survived. In the light-disturbed sites, large size Korean pines were dominant.     

Effect of forest thinning on hydrologic nitrate exports from a Nsaturated plantation

Although several studies have assessed the effects of thinning on water quality,including nitrogen(N)exports,few have examined N-saturated plantations.This study assessed the short-term effect of thinning on N exports from a N-saturated plantation forest in northern Kyushu,western Japan,that was thinned(43%of basal area)during January-March 2012.Water levels at the gauging station were continually measured,and streamwater baseflow and stormflow samples were collected before(2011)and after(2013)forest thinning.Annual precipitation before(2469 mm)and after(2418 mm)forest thinning differed little,and annual water discharge after thinning(1641 mm)was similar to that before thinning(1609 mm).However,direct flow during stormflow periods was higher after thinning(260 mm)than before(153 mm).The concentrations of major ions in stream water did not differ before and after thinning.As a result,the high annual dissolved inorganic N(DIN)exports differed little before(35.8 kg N ha^-1 a^-1)and after(36.5 kg N ha^-1 a^-1)forest thinning.DIN exports during stormflow periods were slightly higher after(12.2 kg N ha^-1 a^-1)than before thinning(10.5 kg N ha^-1 a^-1)and were proportional to the increased direct flow after thinning(561 mm after vs.470 mm before thinning).We concluded that thinning does not affect annual N exports from the N-saturated plantation forest,but it can increase the proportion of N exported during stormflow periods in proportion to increased water volume of direct flow after thinning.     

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。     

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。     

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.     

Natural regeneration characteristics of Pinus sylvestris var. mongolica forests on sandy land in Honghuaerji, China

Natural regeneration in Mongolian pine, Pinus sylvesttis var. mongolica, forest at Honghuaerji of China （the original of the natural Mongolian pine, forest on sandy land） was studied in 2004. The total mean values of regeneration indexes were higher in mature stands （more than 80% individual stems were older than 50 years）, the maximum of regeneration index reached 29 seedlings, m^ 2, with lowest values in the younger stand, e.g., in 32-year old and 43-year old stands. The stand age was an important factor determining the natural regeneration, which was the best in the older stands in this investigation （e.g. about 80-year old）. The regeneration index seemed not to be closely in relation to canopy openness although Mongolian pine is a photophilic tree species. In each type of gaps, natural regeneration was very well. Regeneration indexes were satisfactory at the south and east edges in the circle gaps; and at the east edge of the narrow-square gaps. Results indicated that Mongolian pine, seedlings could endure shading understory, but it would not enter the canopy layer without gap or large disturbance, e.g., fire, wind/snow damage or clear cutting etc. These results may provide potentially references to the management and afforestation of Mongolian pine, plantations on sandy land in arid and semi-arid areas. Researches such as the comprehensive comparisons on regeneration, structure and ecological conditions and so on between natural Mongolian pine, forests and plantations should be conducted in the future.     

Wind loading of trees: influence of tree size and competition

Wind damage to forests is an important ecological disturbance factor. At the same time, it can have serious economic consequences due to a reduction in timber production. Current models for predicting the risk of wind damage are useful, but generally only focus on the “mean” tree within uniform stands. This paper presents measurements made of wind loading on trees of different sizes within four forest stands of different structure and management history, but all well-acclimated to current wind conditions. Each tree demonstrated a linear relationship between the maximum hourly turning moment and the square of the average hourly wind speed at the canopy top; we defined this ratio (the gradient of the line M _max vs. u ²) as the turning moment coefficient (T _C). T _C was correlated with tree size, in a relationship that differed little between the four forest sites despite the differences between the stands. The relationship between T _C and individual tree competition within each stand was investigated, using both distance-independent and distance-dependent competition indices. All sites showed decreasing T _C with increasing competition. However, the relationships differed between sites and would also be expected to change through time for a single site. The distance-dependent indices offered no improvement over the simpler, non-spatial indices that required only a diameter distribution. We suggest how, subject to further work, the results presented could be applied to calculate the risk of wind damage to trees of different sizes within a forest stand, and how the risk of wind damage to individual trees might change in response to thinning.     

Trade-offs between seedling growth,thinning and stand stability in Sitka spruce stands: a modelling analysis

The forest industry is increasingly adopting alternative silvicultural systems, involving regeneration beneath an existing forest canopy, rather than clear-felling and replanting. To apply these silvicultural systems in windy regions such as Britain and Ireland, it is essential that the interactions between thinning intensity, stand stability and seedling growth are properly understood. Here, we present a modelling analysis of the three key relationships between: (i) stand density and the proportion of incident radiation transmitted through a forest canopy as a stand is thinned; (ii) transmitted radiation and seedling growth, and (iii) stand density and stand stability. These relationships were examined using separate models of radiative transfer (MAESTRO), seedling growth, and stand stability/wind risk (ForestGALES). Output from the three models was synthesised to calculate whether a given stand thinned to a pre-defined stability limit would allow sufficient light to penetrate the canopy for seedling growth. A minimum transmittance of 20% was identified as a requirement for seedling growth, which corresponds to removing 45% of stand basal area. A thinning of this intensity left some stands susceptible to unacceptable wind damage, especially in old or previously thinned stands on soils where rooting is impeded. The results emphasised the fact that rooting conditions, thinning history and age of intervention are major constraints on the silvicultural options. In general, older stands are not suitable for conversion to continuous cover forestry (CCF) systems, and the transformation process should begin at pole stage, when heavy thinning does not leave the stand unstable. The analysis approach used here illustrates the potential for combining models to address complex forest management issues.     

Survival,growth and reproduction by big-leaf mahogany (<Emphasis Type="Italic">Swietenia macrophylla</Emphasis>) in open clearing vs. forested conditions in Brazil

Big-leaf mahogany (Swietenia macrophylla) trees are often retained in agricultural fields and pastures for seed and timber production after selective logging and forest clearing in the Brazilian Amazon. At a forest management site in southeast Pará, we censused trees growing scattered across a large open clearing after forest removal and in heavily disturbed forest after selective logging and canopy thinning for survival, stem diameter growth, fruit production, and date of dry season flowering initiation annually during 1997–2003. Trees in the open clearing died at faster rates, grew more slowly, produced fewer fruit, and initiated flowering earlier, on average, than trees in logged and thinned forest during this period. The principal cause of mortality and stem damage in both environments was dry season groundfires. Mahogany trees in logged and thinned forest at the study site grew faster than mahogany trees at a selectively logged but otherwise undisturbed closed-canopy forest site in this region during the same period. This was likely due to vine elimination by groundfires, increased crown exposure after canopy thinning, and soil nutrient inputs due to groundfires. Without effective regulation and control of anthropogenic fires, attempts to manage remnant mahogany trees for future timber yields or to restore commercially viable populations in this region may prove futile.     

Wind and snow damage in a thinning and fertilization experiment in Picea abies in southern Sweden

Changes in susceptibility to wind and snow damage due to thinningand fertilization were examined in even aged Norway spruce (Piceaabies (L.) Karst.) stands in southern Sweden. The stands arepart of a nationwide experiment to investigate growth and yieldfollowing different thinning and fertilization regimes establishedbetween 1966 and 1983. The material used in this study included16 replications of seven treatments. The treatments were: threelevels of thinning from below (20–70 per cent); 20 percent thinning from above; thinning from below in combinationwith N and NP fertilization (thinning percentage 25–28per cent); and unthinned control. The stands have been censusedtwice for damage during an average period of 12 years. The degree of wind and snow induced damage varied between 9and 20 per cent of the basal area increment produced duringthe observation period. For treatments with high basal arearemoval, the highest relative number of trees damaged by windoccured during the first period after thinning. The denseststands (i.e. unthinned controls and stands thinned from above)showed a high proportion of snow damage throughout the observationperiod. The block effect was in general more significant thanthe effect of treatments on damage level. When analysing theinfluence of the block effect (i.e. of site and stand characteristics)on damage level, wind damage was best predicted by stand basalarea left after thinning and stand age, while snow damage wasbest predicted by latitude, altitude, site index, and standage. On average the tested site and stand characteristics explained17 per cent of the variation in wind damage and 36 per centin snow damage.     

Line thinning promotes stand growth and understory diversity in Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don) plantations

We studied the effects of line thinning on stand structure, microclimate and understory species diversity of two Cryptomeria japonica D. Don plantations in south-central Japan. In each of two study sites we compared stand structure between the thinned stand and an adjacent unthinned stand and found that line thinning increased the growth rate of residual trees such that stand basal area may recover within 10 years after thinning. In the thinned stand, more open canopy conditions resulted in higher maximum temperatures on the forest floor during the early growing season than in the unthinned stand. The thinned stand had greater understory plant species richness and biomass than the unthinned stand. This study suggested that line thinning could potentially enhance biodiversity while simultaneously increasing tree-growth rates in overstocked Cryptomeria japonica plantations.