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1.
《森林与环境学报》2015,(2)
研究林隙结构对天然林更新演替具有重要意义,以闽北闽粤栲天然林林隙的基本特征及干扰状况为研究对象,通过对闽北闽粤栲天然林中的28个林隙进行调查,进而分析其林隙大小结构、年龄结构、形成方式、形成木特征及干扰规律。结果表明,在闽北闽粤栲天然林中,冠林隙中10-20 m2所占的数量比例和面积比例都是最大的。扩展林隙个数以50 m2所占的数量比例最大,以50-100 m2所占的面积比例最大。林隙年龄以10-15 a所占的数量比例最大。林隙形成方式主要是折干与掘根风倒共同作用,占总株数的57.14%。林隙多由1-4株形成木形成的,平均每个林隙有4.04株形成木,形成木的径级以10、20 cm为主,占82.30%。林隙的线状密度为12.84个·km-1,冠林隙和扩展林隙的形成速率分别为2.08和7.02 m·km-1·a-1。林隙干扰的周期为476.19 a。 相似文献
2.
海南岛热带山地雨林林隙及其自然干扰特征 总被引：26，自引：0，他引：26
通过对海南岛霸王岭原始热带山地雨林中５３个林隙的调查,研究了海南热带山地雨林林隙的基本特征和自然干扰规律。海南热带山地雨林林隙的形状近似于椭圆形,椭圆的长短轴比率不随林隙的大小而变化,基本上都在１４左右;扩展林隙（ＥＧ）和树冠空隙（ＣＧ）在热带山地雨林景观中的面积比例分别为５３５２％和２５２２％,干扰频率分别为１３４％·ａ－１和０６３％·ａ－１,林隙干扰的返回间隔期约为１６０ａ。海南热带山地雨林中ＥＧ的大小一般变化在３０～５００ｍ２左右,平均约为１６０ｍ２,大多数ＣＧ的大小一般都变化在１５～２００ｍ２左右,平均约为８０ｍ２。大多数的林隙是在４０ａ以前形成的,而１０～３０ａ之前形成的林隙最多。大多数林隙是由１～４株形成木创造的,而由２株形成木创造的林隙最多。林隙形成木通过掘根、枯立、干基折断和干中折断死亡的比例分别是１６８８％,１４２９％,３６３６％和３２４７％,在不同的林隙中可见到形成木这几种死亡形式的不同组合。海南热带山地雨林中的林隙主要是由２０余个树种创造的,其中不仅有第一层的树种,而且还有第二、三层的树种。文章最后以林隙动态理论为基础,对海南热带山地雨林的经营提出了几点建议。 相似文献
3.
林隙(GAP)干扰研究进展 总被引：76，自引：3，他引：76
本文系统地介绍了森林循环的理论、自然干扰的概念、林隙的一般特征和林隙干扰的时空格局。干扰是森林循环的驱动力,干扰形成的林隙是森林循环的起点。林隙的大小、形成年龄、形成方式以及形成木的特征是研究林隙特征的重要参数,虽然不同森林群落中,林隙干扰的频率和程度及其时空变化规律不同,但大多数森林的年平均干扰率是在１％左右。不同的森林类型中,大、小型干扰的比例不同。小型林隙干扰与大型灾难性干扰在不同时空条件下的组合,就形成了不同森林景观的时空变化格局。 相似文献
4.
不同经营模式对丹清河林场天然次生林植物群落结构及其多样性的影响 总被引：4，自引：0，他引：4
以黑龙江省哈尔滨市林业局丹清河林场的针叶林、阔叶林及针阔混交林3种天然次生林为对象,以无干扰模式为对照,研究粗放经营模式和目标树经营模式对植物群落结构及其多样性的影响。结果表明:1)在针叶林、阔叶林、针阔混交林中,相对于粗放经营模式和无干扰模式而言,目标树经营模式中以目标树为主的第1林层断面积值最大,占林分断面积百分比为95.00%,90.00%,87.00%,但第2,3林层断面积最小,形成了合理的林冠结构;2)目标树经营模式的林木平均密度(408～858株·hm-2)显著低于(P<0.05)粗放经营模式(992～1917株·hm-2),而平均胸高断面积(18.18～46.03m2·hm-2)与粗放经营模式(18.43～39.70m2·hm-2)无显著差异(P<0.05),平均树高(11.8～14.9m)和平均胸径(15.94～27.34cm)均显著高于(P<0.05)粗放经营模式(分别为7.1～11.0m和10.18～19.00cm);3)粗放经营模式和无干扰模式60%以上的林木为小径木(12cm以下),目标树经营模式60%以上为中径木(14～18cm)和大径木(20cm以上);4)粗放经营模式乔木层的多样性高于目标树经营模式;灌木层除阔叶林的多样性与目标树经营模式不可比外,其余林分的多样性均高于目标树经营模式;草本层的多样性则以目标树经营模式为最高;5)粗放经营模式只注重短期经济价值而忽略生态要求,无干扰模式只注重绝对生态保护而忽略人对森林资源的利用需求,二者都不符合人类经营森林的目标。目标树经营模式可改善群落和林冠结构,不仅能够获得较好的经济效益,还能平衡生态功能,符合人类经营森林的目标。 相似文献
5.
6.
从林隙大小和林隙年龄两个方面研究了以椴树、色木槭和蒙古栎为主的次生阔叶林经营采伐形成的林隙及其更新特征.结果表明:冠林隙面积＜20 m2的林隙占42.8%,20～40 m2的林隙占23.8%,40～60 m2的林隙占33.4%.38.1%的林隙呈圆形,61.9%的林隙呈椭圆形,其中38.5%为南-北方向,46.2%为东-西方向,15.3%为东北-西南方向.林隙一般由3～4株采伐木形成,采伐木主要由椴树、蒙古栎和山槐组成.非林隙林分更新中灌木占优势,林隙更新中乔木占优势,且随林隙面积和形成年龄增加而增强.林隙内的树种多样性和更新密度明显高于非林隙林分.综合多样性随林隙面积和年龄的增加而下降.不同大小级林隙内的优势种不同,以阳性树种占大多数. 相似文献
7.
林隙特征(gap characteristics)是研究林隙的作用、影响以及动态变化规律的基础。研究工作以燕山山地新丰林场油松人工林为研究对象,采用样带法进行野外调查,分析了林隙的形成方式、形状、大小、年龄结构、边缘木等特征。结果表明:人工近熟油松林林隙的形成主要为抚育间伐和择伐等人为因素形成,自然形成的较为罕见;形状为近椭圆形,且林隙的形状与面积并无相关性;林隙的面积多集中在40～60m~2,所占数量比例和面积比例均为最大,分别为33.33%和22.22%;以高度为14～16m的林隙居多,略低于林分的平均高;发育后期的林隙及前期的林隙居多,分别占到林隙总数的40.00%和31.11%。 相似文献
8.
雷州半岛高桥红树林内带林窗特征分析——以湛江市廉江高桥红树林保护小区为例 总被引：1，自引：0，他引：1
对红树林林窗特征研究,是研究退化红树林生态系统恢复与重建、对次生红树林进行改造、科学管理红树林生态系统的基础。对雷州半岛廉江高桥红树林保护小区内带林窗特征进行了调查,分析林窗大小结构、形成方式、形成木特征等。调查发现:高桥红树林内带林窗主要以小面积林窗为主,分布在实际面积1～10 m2之间和扩展面积1～50 m2之间;林窗主要形成方式是枯死,其次是侧枝损坏;林窗形成木数量范围在1～6株之间,平均每个林窗有2.3株形成木;形成木种类是红海榄、桐花树、木榄、秋茄,各占总比例的5.4%,8.9%,60.7%,25.0%;形成木腐烂等级较高。 相似文献
9.
从林隙大小和林隙年龄2个方面初步研究了杨桦次生林经营采伐形成的林隙及其更新特征.结果表明:冠林隙面积<50 m2占7%,50～100 m2占21%,100～150 m2占36%,150～200 m2占29%,>200 m2占7%.28.6%的林隙呈圆形,71.4%的林隙呈椭圆形.椭圆形林隙中55%为南-北方向,30%为东北-西南方向,15%为东南-西北方向.林隙一般由7～10株山杨、白桦或山槐被伐后形成.林隙内更新幼苗的密度和生长状况优于非林隙林分.在林隙形成初期,灌木幼苗在林隙更新中占绝对优势,但随着林隙形成年龄的增加,灌木将逐渐丧失其优势,乔木的优势则逐渐上升.除50～100 m2林隙外,乔木幼苗的平均高和平均基径均大于灌木,但都在100～200 m2林隙内最大.各大小级林隙内更新的主要乔木中阳性树种占大多数,但优势种各不相同. 相似文献
10.
应用传统踏查法对湛江高桥红树林高潮带林窗形成木展开种类、数量、地径、树高及形成方式等调查,分析其林窗特征结构。结果表明:高桥红树林林窗主要以小面积为主,实际面积分布在1~10m2,扩展面积分布在1~40m2,且实际林窗远小于扩展林窗,前者的平均面积仅约为后者的26.60%;林窗形成木数量范围在1~6株之间,林窗形成木的数量与林窗数量成反比例关系;林窗形成木的种类以优势种木榄为主,约占林窗形成木的60.71%;林窗形成木的地径以5~10cm和10~20cm为主,分别占总数的21.43%和62.50%;林窗的高度变化在2~4m。 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
13.
Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and
also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the
amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter
bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K
was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed
significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week−1 for leaves and from 0.0225 to 0.0633 week−1 for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed
during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly
between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species
provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient
enrichment capacity and slower decomposition rates which would minimize leaching losses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(2):118-130
The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions. 相似文献
15.
Steven Maranz Amadou Niang Antoine Kalinganire Djeneba Konaté Bocary Kaya 《Agroforestry Systems》2008,72(3):231-239
Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional
data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral
contents and B1 and B2 vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising
germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B1 88 mg 100 g−1, B2 187 mg 100 g−1, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal
diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties
to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations. 相似文献
16.
《Wood material science & engineering》2013,8(2):76-84
Abstract Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists. 相似文献
17.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
18.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
19.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
20.
Astra Zaluma Lauma Bruna Darta Klavina Natalija Burnevica Kristine Kenigsvalde Andis Lazdins Talis Gaitnieks 《Forest Pathology》2019,49(6)
Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered. 相似文献