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1.
建阳区森林火灾与气象因子相关性研究 总被引：1，自引：0，他引：1
《内蒙古林业科技》2016,(1)
对建阳区历年来3次最大典型森林火灾与气象因子的相关性研究表明:气温较高、相对湿度较小、风速偏大时,火灾发生概率较大,且空气温度为最主要气象因子。根据3次森林火灾气象要素的日变化规律看,下午14时左右是森林火灾发生的重要时段。且火灾与其发生的前3 d气象要素相关,即前3 d气温越高、空气相对湿度越小、风速越大,火灾越容易发生,各F值均大于F0.01(F0.01=7.5910),达到极显著。风速不仅影响森林火灾的发生,还直接影响其蔓延。 相似文献
2.
雷击火是中国大兴安岭地区重要火源.根据1990-2006年研究区内10个气象站日观测数据包括最高气温、最小湿度、24 h降水、平均风速等指标计算每日FWI系统各指标,分析雷击火的发生与火险指数的关系.根据各气象站与研究区质心的距离确定各气象站的权重,计算研究区火险指数平均值.1990-2006年大兴安岭林区共发生森林火灾591起,其中雷击火359起,占60.7%.70%的雷击火分布在121°～125°E,51°～53°N,平均每起雷击火过火面积为797.37hm2,森林受害面积为581.67 hm2.71.9%、2.5%和17.3%的雷击火分别发生在落叶针叶林、落叶阔叶林和草地.雷击火发生在4-9月,5-8月是雷击火多发月份.1990-2006年雷击火发生时间段整体上有延长趋势.8月和9月发生的雷击火都发生在1998-2005年.雷击火的发生受气温与降水的影响,月均气温高、降水量少,雷击火次数明显多.发生雷击火日的平均可燃物湿度码FFMC、DMC、DC和FWI分别为90.3,69,6,287.4和24.7.雷击火发生日各火险成分指数平均值均高于1990-2006年4-9月总体平均值.根据雷击火发生概率和每日火险指数建立了雷击火发生概率预测模型. 相似文献
3.
我国大兴安岭地区夏季林火的火环境研究 总被引：1，自引：0，他引：1
利用Arcgis和SPSS软件对大兴安岭地区1967-2008年夏季火险期森林火灾发生当天的气象因子和火点位置的植被和地形因子进行了定性和定量分析,探讨了夏季火的火环境特征,以期为防火部门进行森林管理及政策制定提供依据。结果表明:近42年来,夏季火发生时的日平均气温和最高气温范围分别为15~25℃、24~34℃,而且平均气温和最高气温不同导致夏季火发生次数具有极显著差异性,P﹤0.01;夏季火发生时,降水量主要为0~1 mm,而且具有极显著差异,P﹤0.01;平均风速范围0.5~3 m/s,不同风速发生火灾次数具有显著性差异,P﹤0.05;平均气压集中在945~975 h Pa,P﹤0.05;平均空气相对湿度55%~70%,P﹤0.01。通过对地形和植被的相关因子进行分析可知,夏季火主要发生在中高等海拔的平坡或缓坡区域,植被类型以落叶针叶林为主,其次是草甸。 相似文献
4.
气象因子对云南大理森林火灾的影响 总被引：1，自引：0，他引：1
本文选用2001年-2010年大理州的森林火灾次数与对应的气象数据进行统计分析,通过分析大理州森林火灾的时间分布及对应的气候特征,得出了火灾次数与气温和风速呈正相关、与相对湿度呈负相关的结论。用森林火灾次数与气象因子进行相关分析,结果表明月平均最高气温、平均相对湿度和平均最大风速与月火灾次数显著相关;旬平均最高气温、平均相对湿度和平均最大风速以及前两旬的累计降水量与旬火灾次数显著相关;日最高气温、平均相对湿度、最大风速和前15日累计降水量与日火灾次数显著相关。综合分析表明气温、降水、相对湿度和风速与大理州森林火灾次数有明显的相关性,气温、风速与火灾次数呈正相关,降水、相对湿度与火灾次数呈负相关。 相似文献
5.
一、森林火灾发生的原因①人为因素②腐殖质着火③泥炭自燃④旱雷和闪电二、火灾发展的条件温度、湿度条件森林火灾的发生和蔓延影响很大,当气温很高时,由于蒸发加速,森林中有机物质的湿度降低,因而容易着火,当气候较为干燥时,可燃性的有机物质的水份蒸发也同样加速,使火灾发生的机率增大.风速加速林地水分的蒸发,且给燃烧点供应大量的氧以促进燃烧,微小的火源在大风的作用下,酿成难以控制的特大火灾. 相似文献
6.
我国大兴安岭呼中林区雷击火发生火环境研究 总被引：19，自引：2，他引：19
雷击火作为天然火源是一种难以控制的自然现象 ,其形成机理极为复杂。我国大兴安岭林区是雷击火主要发生区 ,对雷击火的研究表明特殊可燃物、干雷暴的天气和较高的地形构成了雷击火发生的火环境。长期干旱 ,可燃物失水严重 ,森林中积累丰富的可燃物 ,雷暴发生后干燥的植被容易引火燃烧 ,起火之后 ,遇上盛行的大风将使火灾迅速蔓延。雷暴 ,特别是干雷暴出现时 ,遇到降水少、地面温度增加 ,相对湿度降低 ,可燃物干燥的情况 ,就很容易引起火灾。森林火灾多发地区 ,雷击火常常也多。大兴安岭纬度越高 ,雷击火越多 ,5 1°N以北海拔 80 0m以上山脉的腹部或山顶的落叶松 -偃松林、樟子松 -偃松林林区为该林区雷击火发生最集中区域。一次干雷暴天气过程 ,可以同时引起多起雷击火 ,它们之间的距离最远可达 1 5 0km。雷击火多发生在 6— 8月 ,雷击火的发生时段主要集中在下午的 1 4时到 1 7时。雷电作为一个随机干扰因子引发森林火灾 ,使得雷击火的预防与扑救变得更加困难。 相似文献
7.
森林火灾的发生和扩散与很多因素有关，如森林内的地被物的含水率、树种的组成、森林的林分郁闭度、地形、土壤、气象条件、人为因素等。而气象条件对森林火灾的影响特别要引起注意。气象条件主要指空气湿度、温度，降水、风等。空气湿度，是表示空气的干湿程度的物理量。空气的相对湿度，直接影响森林火灾的发生和发展。相对湿度大，空气中水分充足，树林中水分蒸发慢，森林火灾的危险性会减小。当空气相对湿度为100％时，也就是实际所含水蒸气密度等于饱和水蒸气密度，此时空气中的水蒸气就会凝结成需，如果这时温度在0℃以下，水蒸气会直… 相似文献
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10.
大兴安岭地区森林火险变化及FWI适用性评估 总被引：3，自引：0，他引：3
根据研究区内及附件气象站每日气温、相对湿度、24小时降水和风速计算1987—2006年大兴安岭每日的加拿大林火天气指数系统(FWI)各组分值。利用空间插值方法,获得1987—2006年所有森林火灾发生日的FWI系统各组分值。大兴安岭林区森林火灾主要发生在落叶针叶林(61.3%)、草地(23.9%)和落叶阔叶林(8.0%),主要火源是雷击火(占57.1%)。4—6月份森林火灾发生时的FWI、FFMC和ISI平均值高。根据1987—2006年FWI组分指数的分布和火发生情况,对森林火险指数进行了分级,低、中、高、很高和极高火险的FWI取值范围分别为0～2.5,2.6～10.0,10.1～18.0,18.1～31.0,≥31.1。FWI对大兴安岭地区森林火险有显著的指示意义,FFMC和ISI对预测火灾的发生与蔓延有较好的指示作用。1987—2001年每年明显有春季和秋季2个火险期,但2002—2006年火险期显著延长。春季火险严重度指数(SSR)波动幅度比较大,夏季SSR和春季SSR有相反的波动趋势,2000—2006年秋季火险严重度明显升高。 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.
《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
16.
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
17.
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
18.
《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
19.
《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
20.
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