对巩留林场东部林区采伐方式的看法

巩留林场东部林区,包括塔里木吉尔尕朗、卡西、莫合、奎登良、大吉尔尕朗五个施业区(其中奎登良已划作自然保护区)。林区总面积为45267公顷,其中有林地面积39394公顷,林分蓄积量为1852.4万立方米。成过熟林占有林地面积的93.7％,其蓄积占林分蓄积的95.2％;而中龄林仅占蓄积的4.8％和面积的6.3％;幼林极少,不能单独区划为小班。整个东部林区地形复杂,山势较陡,坡度变化较大,平均坡度在25—30度之间,也有一部分是25度以下的林区。坡向以北坡、东北、西北坡为最多。由于受北冰洋及中亚气候的     

嘉陵江中上游林地资源与地形因子时空变化研究——以四川省武胜县为例

嘉陵江中上游林地资源丰富,研究林地资源结构、分布与地形因子之间的关系,对嘉陵江生态保护具有重要意义。利用1998年、2018年Landsat TM遥感影像和DEM数据,采用最大似然分类法、DEM数据栅格表面分析、重分类处理与空间叠加进行林地资源空间演变受地形因子的影响研究。嘉陵江中上游林地资源面积以318.43 hm2·a-1的速度显著增加,林地资源类型中有林地平均增加速率最快,正向增加明显的有林地、宜林地和苗圃地与疏林地、未成林地和无林地速率大小不一;林地资源结构呈现出以水土保持林、水源涵养林的柏木(Cupressus funebris)和巨桉(Eucalyptus grandis)为主,经济林中的橙为辅的特征;林地资源主要集中在缓坡坡度、低海拔丘陵和下坡坡位上,无坡向分布区域极少;林地资源转移速率在下坡坡位、低海拔丘陵和西南、东南坡向正、负转移速率最快和最大;各林地类型分布指数在不同地形上差异较大,总体以斜坡、下坡位为绝对优势位,平坡、无坡向为相对劣势位;偏相关分析表明,坡度、海拔、坡向、坡位与林地资源总量分别为负相关、正相关、正负交替、负相关的关系,但与有林地、灌木林地、苗圃地正相关关系较明显。基于林地资源总量、结构与地形因子之间的空间关系,可较好地了解嘉陵江中上游林地资源分布情况,为后期生态修复、生态结构调整提供参考依据。     

古障林场:生态林为主的中型林场

国有西林县古障林场始建于1958年,隶属市、县两级管理,总面积24751.9公顷,经营面积13020.3公顷,有林地面积17241.4公顷,其中生态公益林面积14477.6公顷,占林地总面积的84%,森林覆盖率为82.6%,是一个以生态林为主的中型林场.     

基于“乡村绿化”数据的怒江州生态安全格局研究

基于Landsat遥感影像对怒江州进行土地利用类型解译,通过3S技术手段,叠加其他相关数据,对怒江州生态系统脆弱性进行评价,并进行生态系统适宜性分区。结果表明,怒江州林地与草地两项占比达86.46%,建设用地占比仅0.27%,怒江州自然环境受制于特殊地形,并未遭到大程度的破坏;怒江州生态系统总体表现为：轻微脆弱与轻度脆弱土地占比达52.34%,重度、中度脆弱土地主要集中在西北部较高海拔地区,生态系统总体保持在较好水平。基于MCR模型,以乡村绿化数据为生态源地,对怒江州绿地适宜性进行评价。结果表明,适宜生态用地拓展的土地面积总占比达90.83%,表明总体生态格局较为安全,在未来城镇化、生态格局建设中具有较大回旋余地。     

复杂地形约束下西昌市土地利用空间分布格局

以西昌市为研究区,基于DEM及遥感解译获取的土地利用数据,在GIS软件的支持下采用空间技术对提取的地形因子(高程、坡度、坡向、地形位)与土地利用现状图进行叠加处理,得到了4种地形因子影响下不同土地利用的分布特征,进一步分析土地利用空间分布与地形因子的耦合关系。结果表明:(1)西昌市土地利用类型以林地为主,占总面积的50.51%,草地、耕地、水田、建设用地面积接近,水体和其他用地类型所占比例较小;(2)各土地利用类型在不同高程、坡度、地形位分级上呈现出阶梯变化规律;阳坡、半阳坡土地利用程度高于阴坡、半阴坡,水体不受坡向影响;(3)西昌市土地利用类型受地形因素较严格限制,当前没有出现因强烈的人为扰动及地质灾害等导致的极端大规模分布情况。     

不同地形条件下群落物种多样性与胸高断面积的差异分析

以浙江天日山国家级自然保护区的常绿阔叶林为例,基于DEM在群落尺度上分析不同地形条件下群落物种多样性和胸高断面积的差异.对单一地形因子分析的结果表明:在常绿阔叶林群落中,坡度过大或过小均可引起常绿阔叶林物种多样性和胸高断面积下降,中等坡度时物种多样性和胸高断面积最高;胸高断面积随坡向的变化比物种多样性敏感,自东坡经南坡过渡到西坡,胸高断面积呈降低趋势,东坡的物种多样性和胸高断面积最高,西南坡最低;物种多样性和胸高断面积随地表粗糙度增加呈降低的趋势.对组合地形因子分析结果表明:坡向和坡度的不同组合,对物种多样性的影响不大,但与胸高断面积存在较大的相关性,各坡度级中,西南坡胸高断面积均最低;坡向和粗糙度的不同组合对物种多样性的影响不大,但与胸高断面积存在一定的相关性,在各粗糙度级中,西南坡均为最低;坡度和粗糙度组合对物种多样性和胸高断面积的影响均较大,同一粗糙度级中,物种数在各坡度级表现为坡度级2＞坡度级3＞坡度级1,除坡度级1外,各粗糙度级上的胸高断面积随坡度的增加而增加.     

陕西省森工集材方式成本分析

1 采育企业的地形特点及资源状况陕西森工采育企业全部分布在秦岭中、西段。该地段地形陡峭,森林资源可及度低,生产经营难度大,林区平均坡度35°。其中15°以下的林地面积仅为2642ha,占0.7%;16°～25°的林地面积31049ha,占8.1%;26°～35°的林地面积179331ha,占46.8%;36°～45°的林地面积117066ha,占30.5%;46°以上的林地面积53057ha,占13.9%。在247530ha 成熟林中,用材林面积为214381ha,主要分布在25°～45°的林地上。     

森林经理的中心环节是档案管理——湖北省国营林场森林经理工作刍议

<正> 湖北属南方集体林区省份之一。全省国有林地面积仅占林业用地总面积的7.1%。除神农架林区外,其余大都分布在153个国营林场中。这些林场主要是在五十年代中期至六十年代初期建立的,面积一般在3万亩     

科学明晰产权 努力放活经营 扎实稳妥推进集体林权制度改革

<正>山西省地处黄土高原、黄河中游,是全国重要的能源重化工基地,也是生态环境脆弱和农民收入较低的省份之一。全省国土总面积15.6万平方公里,其中林业用地面积1.14亿亩,森林面积3316万亩。林业用地中,集体林地8296万亩,其中公益林占89.1%。全省总人口3400万人,其中农业人口2200万人,2009年农民人均纯收入4244元。山西之长在于煤,山西之短在于水,发展之基在于林。山西煤炭储量占全国的1/3,水土流失面积占全省国土总面积的69%,森林覆盖率只有14.12%。脆弱的自然生态条件,加上多     

基于GIS的林地生态适宜性评价——以青藏高原东部迭部益哇沟林区为例

为改善林地生态环境,提高林地资源利用价值,以迭部县益哇沟林区为研究区,运用GIS软件进行信息分析与处理,对研究区林地生态适宜性的影响因子(海拔、坡度、坡向、土壤成分、土壤机械组成)进行等级分级并分配权重,综合对研究区的林地生态适宜性进行分析评价。结果表明:研究区树木生长状况较好,整体林地适宜性处于较优水平,属于Ⅰ等适宜性林地,适宜发展经济适用林以及快速丰产林。林地生态适宜性各等级所占面积比例排序为:Ⅱ等适宜性林地(42.39%)Ⅰ等适宜性林地(34.89%)Ⅲ等适宜性林地(15.71%)Ⅳ等适宜性林地(7.21%),林区以Ⅰ等Ⅱ等适宜性林地为主,主要集中在中部及东南部地区,面积约占总面积的77.28%。     

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.     

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.     

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.     

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。     

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.