雅鲁藏布大峡谷景区生态旅游环境容量研究

旅游环境容量是景区调控游客规模、实现景区健康发展必不可少的依据。以雅鲁藏布大峡谷景区为研究对象,依据旅游环境容量分为旅游空间环境容量、旅游生态环境容量、旅游设施环境容量和旅游社会环境容量4个分量指标,按这些指标对大峡谷景区的旅游环境容量进行评价。研究表明,雅鲁藏布大峡谷景区的日生态旅游环境容量为2 395人次;月生态旅游环境容量为71 850人次。空间环境容量是旅游发展中的主要限制因子,游客量随季节分布明显且存在较大差异。针对大峡谷景区的生态旅游环境容量问题提出具体的调控措施。     

尖峰岭国家森林公园旅游环境容量分析

在分析环境容量相关理论的基础上,针对尖峰岭国家森林公园分区采用面积法、游线法、卡口法估测景区旅游环境容量;经测算景区日环境容量为6705人次,年环境容量为1804000人次;为了确保景区生态环境质量不下降、旅游资源和环境不“超负荷”运转,实现旅游资源可持续利用和旅游业可持续发展,景区年游客容量以不超过180万人次为好;...     

猫儿山自然保护区老山界景区旅游环境容量分析

在分析生态旅游环境容量基本理论的基础上,针对猫儿山国家级自然保护区老山界景区进行生态旅游规划,分区采用面积法、游线法、卡口法估测景区旅游环境容量;经测算景区日环境容量为2 490人次,年环境容量为90.9万人次;为了确保景区生态环境质量不下降、旅游资源和环境不"超负荷"运转,实现旅游资源可持续利用和旅游业可持续发展,景区年游客容量以不超过59.5万人次为好;生态旅游开发必须根据旅游区旅游环境容量和游客容量控制建没与发展规模,确保旅游区生态环境良性发展,最大限度满足社会需求和收益最大化的需要.     

塞罕坝国家森林公园旅游环境容量研究

塞罕坝国家森林公园经过数年发展游客量不断增加,为了处理好森林旅游开发与保护之间的关系,为塞罕坝国家森林公园旅游资源开发、旅游结构调整、旅游环境保护提供科学依据,采用资源空间容量、生态环境容量、经济发展容量和当地居民心理容量4个子系统,对公园的旅游环境容量进行测定,结果得出塞罕坝国家森林公园资源空间容量为11 153人次/d,生态环境容量为50 911人次/d,经济发展容量为8 871人次/d,旅游环境容量综合值取最差限制因子8 871人次/d,年环境容量约为100万人次;分析认为经济发展容量中的供电能力是限制塞罕坝国家森林公园旅游环境容量发展的主要因子,公园存在周期性超载问题,对此提出加强基础设施建设、调控淡旺季游客量、进行日常监测等建议。     

三亚湾滨海浴场旅游环境容量研究

为探讨滨海浴场旅游环境容量,以三亚最大滨海浴场——三亚湾滨海浴场为研究对象,从沙滩和海水资源及基础设施等角度,定量研究了该滨海浴场的旅游环境容量。结果表明:三亚湾滨海浴场在满足游客舒适的空间使用面积的前提下,沙滩资源旅游环境容量为99000人/d,高峰时段(13:30～17:30)则为33000人,海水资源旅游环境容量为176000人/d,高峰时段则为58700人。2019年春节期间的统计数据表明,旺季高峰时段三亚滨海浴场瞬时游客数量预计约为2.72万人,考虑到游客在三亚湾滨海浴场为斑块式分布特征,局部沙滩和海水区域处于超载状态。此外,针对基础设施中公厕和垃圾桶等数量目前并不能满足游客的心理需求,提出了通过拓展沙滩外延休闲娱乐空间和开展有特色的海洋节庆活动来提高三亚湾滨海浴场的旅游环境容量的建议,以期解决旺季局部区域超载问题。     

海岛型旅游度假区旅游环境容量研究--以分界洲岛为例

指出了海南分界洲岛为典型的海岛型旅游度假区,以分界洲岛为例,探讨了分界洲岛的旅游环境容量情况,主要从该岛的生态环境容量、功能设施环境容量、旅游空间环境容量和旅游社会环境容量4个指标进行了测算和分析。结果表明:除旅游空间环境容量外,其余3项旅游生态环境容量、功能设施环境容量以及旅游社会环境容量均存在不同程度的超载。根据上述研究结果,提出了促进分界洲岛旅游环境容量建设的策略,并为分界洲岛旅游的开发和发展提供了一些措施和建议。     

武陵源风景名胜区核心景区环境容量研究

从交通环境容量、游客浏览心理容量等方面作了武陵源风景名胜区旅游环境容量调查与测算,探讨了武陵源风景名胜区环境承载状况,并提出了相应的环境容量合理利用对策.     

广西大明山生态旅游环境容量及客容量分析

通过调查测算表明：广西大明山国家级自然保护区内生态旅游区的生态环境容量为11213人次/d ,年生态环境容量为314万人/年,旅游环境容量为10789人次/d ,年旅游环境容量为302万人次/年。分析了生态旅游区的生态环境容量和旅游环境容量,得出了大明山生态旅游区年接待游客的合理容量不宜超过302万人次/年。     

河北木兰围场国家森林公园旅游环境容量研究

河北木兰围场国家森林公园经过数年的发展,游客量逐步增加。为了保护环境不受破坏,本文通过运用面积法、线路法等一系列测算方法,对该森林公园的旅游环境容量进行了详细计算,最终得出河北木兰围场国家森林公园日环境容量为1 091人,年游客容量为16.365万人次,为公园的管理提供依据。     

陕西佛坪国家级自然保护区生态旅游环境容量分析

通过对佛坪自然保护区生态旅游景区环境容量的调查分析,表明佛坪保护区生态旅游景区年环境容量为67 680人次,游客年容量为61 740人次,实际年游客量为1 500人次,为游客年容量的2.5%。并对佛坪自然保护区今后开发生态旅游提出了合理的建议和适当的生态旅游发展方向,从而使保护区的生态效益、经济效益、社会效益得到充分的发挥,生态旅游得到可持续发展。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

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.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

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.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

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.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

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.     

CAD与建筑设计的关系

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。     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

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.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

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.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

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.     

Modelling of adequate pretwist for obtaining straight timber

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.