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为探究冬、春两季不同植物群落的不同垂直高度处PM_(2.5)浓度的变化,运用垂直梯度法对北京奥林匹克森林公园碳通量塔、鹫峰国家森林公园气象观测塔及对照点(北京林业大学校内)共3处样地进行研究。结果表明:春季样地的PM_(2.5)浓度值呈现为冠层以上(塔上部,12 m处)冠层(塔中部,9 m处)冠层以下、地面以上(塔下部); PM_(2.5)浓度日变化基本呈现06∶00—10∶00早上高峰,10∶00—14∶00降低,18∶00—22∶00又呈现出升高的"倒N"型的变化规律;鹫峰国家森林公园气象观测塔3层PM_(2.5)浓度值表现为塔上层塔中层塔下层; 3处地点同一高度处的PM_(2.5)浓度值表现为北京林业大学奥林匹克森林公园鹫峰国家森林公园; 3处地点的PM_(2.5)值为冬季春季。 相似文献
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指出了原油装卸和储存过程的蒸发损耗主要是由饱和烃和芳烃的挥发而引起的,两者共含原油组份的17.4%～22.2%。根据公式计算,原油装船损耗介于0.017%～0.032%,由于装船过程需要伴热,因此按0.03%考虑较为合理,原油储运时的挥发损耗为0.078%～0.217%之间,该过程无需伴热,因此,按0.15%考虑较为合理。装船损耗的排放量明显小于储运工程的损耗量,但由于装船损耗在短时间内集中排放,因此,对下风向地面浓度的影响,装船废气明显大于储运废气。 相似文献
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以山葡萄籽为实验材料，通过单因素法提取葡萄籽中的多酚。根据不同浸提剂在540nm处可见光吸收情况的测定，确定70％甲醇溶液为最佳浸提剂。通过单因素试验确定了提取剂浓度、提取时间、提取温度、料液比的适用范围，再利用正交试验法进行工艺优化。确定最佳工艺条件为：体积分数70％的甲醇，料液比1：20（m／v），70℃水浴，浸提20min。山葡萄籽中多酚的含量可达18．981mg／g。 相似文献
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《绿色科技》2018,(24)
利用O_3及其前体物在线观测数据,对2016年夏季南京市城区O_3污染特征开展研究。结果表明:南京市城区O_3浓度呈显著单峰变化特征,与NO、NO_2、NOx、CO和VOCs呈负相关关系。白天高温有利于O_3的生成,而高湿环境则会抑制O_3的生成。夏季O_3高值易发生于西北和东北方向。在≤4m/s风速范围内,O_3浓度伴随风速的增加而上升。当风速4m/s时,O_3浓度由于大风扩散作用而降低。南京市大气VOCs中烷烃浓度最高,烯烃和芳香烃O_3生成潜势(OFP)较高。乙烯、丙烯、间/对-二甲苯、甲苯、异戊二烯、异戊烷、正丁烷、丙烷、邻二甲苯和反-2-丁烯是活性最高的VOCs物种。 相似文献
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为提高分析效率,对活性炭管对气体中苯的吸附和解吸情况进行了实验改进,结果显示：活性炭管在0．5L/min流量下,吸气10min ,A段吸附了约8mg苯后开始穿透,在满足标准方法要求的吸附效率下,A、B两段共吸附了约8．5mg苯,折算浓度为1700mg/m3,因此,以相同的采样流量和时间,在此浓度以下,可对活性炭管A、B两段合并解吸进行分析测定,若高于此浓度值再分别解吸以判断是否符合解吸效率。改进的解吸方式可减少操作步骤,节省时间和有毒的CS2试剂。 相似文献
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《福建林业科技》2022,(1)
采用固体发酵箱进行球孢白僵菌固体发酵中试试验，对菌丝不同生长阶段的温度、CO_2变化进行监测。结果表明，0～24 h为发酵准备期(延滞期),白僵菌菌丝生长慢，固体培养料温度呈小幅上升的趋势，维持在22℃左右，发酵箱内CO_2浓度则呈现逐渐升高的状态，从2000 mg·m(-3)逐渐上升到5000 mg·m(-3)逐渐上升到5000 mg·m(-3);24～48 h为菌丝初始生长期(升温期),菌丝逐步生长，固体培养料温度急剧上升，发酵箱内形成了明显的温度梯度和CO_2梯度，上层与下层温度差异可达5℃以上，上层CO_2浓度从5000 mg·m(-3);24～48 h为菌丝初始生长期(升温期),菌丝逐步生长，固体培养料温度急剧上升，发酵箱内形成了明显的温度梯度和CO_2梯度，上层与下层温度差异可达5℃以上，上层CO_2浓度从5000 mg·m(-3)上升至13000 mg·m(-3)上升至13000 mg·m(-3)左右，下层CO_2浓度从5000 mg·m(-3)左右，下层CO_2浓度从5000 mg·m(-3)升到6500 mg·m(-3)升到6500 mg·m(-3)左右；48～96 h为菌丝旺盛生长期(稳定期),菌丝大量生长，但固体培养料的发酵温度逐渐降低；96 h以后为产孢期，该阶段固体料温度依然呈现缓慢下降的趋势，逐渐下降接近或略高于室温。通过加入空气内循环系统，可消除发酵箱内温度梯度，并降低CO_2浓度梯度，促进发酵箱内菌丝生长均匀。研究结果可为白僵菌规模化生产提供技术参考。 相似文献
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研究了留叶片的数量、生根粉浓度、扦插时间等对巨尾桉（32～29）扦插生根率的影响，结果表明：生根粉的浓度对巨尾桉树（32～29）插条生根的影响很大，并且要达到较高的生根率，不同扦插时间要求生根粉的浓度不同，4月份扦插的插条生根粉浓度为800mg／L最佳，生根率为93．3％；6月份扦插的插条生根粉浓度为600mg／L较好，生根率就可以达到96．5％；留4对×1／2叶时，扦插条的生根率最高。 相似文献
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《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
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《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
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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
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《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
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《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
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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
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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
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《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
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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
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《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