基于"3S"技术的湖南省土壤侵蚀动态变化研究

利用“3S”技术对湖南省土壤侵蚀动态变化进行了研究,结果发现：①1995年和2000年的土壤侵蚀现状都表明,湖南省土壤侵蚀在空间分布上存在东西方向由东西两侧向中部呈马鞍状递降、南北方向由南向北呈长波式递降的规律;②1995年湖南省主要存在水力侵蚀、重力侵蚀和工程侵蚀3种侵蚀类型,以水力侵蚀为主．约占总侵蚀面积的98．85％,2000年湖南省基本上消灭了重力侵蚀和工程侵蚀,仅存水力侵蚀类型;③湖南省土壤侵蚀面积在时间序列上呈下降之势,2000年较1995年土壤侵蚀面积减少了728．55km^2。水力侵蚀类型中各侵蚀强度面积有增加的,也有减少的,部分侵蚀强度的面积增加是因为更严重一级或几级的水力侵蚀区、重力侵蚀区和工程侵蚀区经治理后形成的一种假象;④通过精度验证,判读准确率平均为89．83％,结果可信。     

干热河谷区冲沟侵蚀研究进展

指出了冲沟侵蚀是一种重要的土壤侵蚀方式,干热河谷区的冲沟侵蚀不仅吞噬宝贵的土地资源,还会对流域生态安全产生严重威胁,因此深入开展冲沟侵蚀研究对于区域水土保持与生态恢复重建具有重要意义。从干热河谷冲沟侵蚀研究方法、冲沟形态特征、冲沟侵蚀的影响因素等方面,探讨了干热河谷区冲沟侵蚀的研究进展,同时展望了今后干热河谷区冲沟侵蚀的研究方向与重点领域。     

湖南水府庙国家湿地公园生态修复效果分析

以湖南水府庙国家湿地公园恢复重建区为研究区,对比了湿地公园修复前(2017年)和修复后(2018、2019年)恢复重建区水质以及鸟类种类和数量的变化,并估算了其生态价值。研究结果表明,研究区湿地修复后出水口的水质得到了显著改善,水样中的悬浮物、化学需氧量含量、氨氮含量、总磷含量和总氮含量明显下降;修复后鸟类种类和数量都大幅度上升,夏季鸟类种类和数量比修复前增长了57.1%和446%;湖南水府庙国家湿地公园恢复重建区产生的生态价值约为2 577万元。     

南方山丘区困难立地植被恢复与重建研究

南方山丘区雨量充沛且分布不均,以及红壤的结构特性决定的生态脆弱性,使该区域成为仅次于黄土高原的严重水土流失区,其中的严重侵蚀红壤区和石灰岩分布区是该区域植被恢复与重建的困难立地区.本文针对该区域的生态环境特点,提出植被恢复与重建的原则,并从困难立地区的立地特点,提出恢复与重建的关键技术和应用模式.     

南岭森林的土壤保持功能

南岭山地是国家25个重点生态功能区之一,但其土壤保持功能较弱。本文以南岭国家级自然保护区及其周边地区为例,分析气候、土壤、地形、植被、人类活动等因素对土壤保持的影响。研究发现,该区域兼有水力侵蚀和冻融侵蚀;大东山花岗岩风化的南岭土壤易受流水侵蚀;山体高差较大、坡度较陡且水系发育,导致水流冲刷能力极强;因此该地非常容易诱发水土流失。而不合理的人类活动,已对局部造成严重的水土流失。保护区森林植被的水土保持生态效益,保存了原本易受侵蚀的南岭土壤,实现了南岭的生态功能和价值。因此,南岭的森林植被是控制水土流失的决定性因素,也是实现土壤保持功能最核心的因子。     

南岭森林的土壤保持功能

南岭山地是国家25个重点生态功能区之一,但其土壤保持功能较弱。文章以南岭国家级自然保护区及其周边地区为例,分析气候、土壤、地形、植被、人类活动等因素对土壤保持的影响。研究发现,该区域兼有水力侵蚀和冻融侵蚀;大东山花岗岩风化的南岭土壤易受流水侵蚀;山体高差较大、坡度较陡且水系发育,导致水流冲刷能力极强;因此该地非常容易诱发水土流失。而不合理的人类活动,已对局部造成严重的水土流失。保护区的森林植被使原本易受侵蚀的南岭土壤得到保护,使南岭的生态功能和价值得以体现。因此,南岭的森林植被是控制水土流失的决定性因素,也是实现土壤保持功能最核心的因子。     

林业生态体系分功能区域评价指标及标准研究--山川秀美评价指标与标准(续)

（上接２００２年第７期）四、水土保持区林业生态系统评价指标及其标准１．水土保持区的界定一般而言，凡是易于发生水土流失的地区，包括易于发生水土流失的山地、半山地、丘陵及河流源头和一些平原地区。在这些地区易于出现水力侵蚀而使土壤侵蚀，减少了土壤肥力；并使耕地受到侵蚀，减少耕地面积；由于水土流失的出现，致使土壤涵养水源能力减弱，易出现洪涝灾害、河流淤积等问题。就全国而言，土壤侵蚀可分为三大类型，即风力侵蚀类型、冻融侵蚀类型、水力侵蚀类型。在这部分主要研究的是水力侵蚀类型区的水土保持林业生态系统的评价。…     

隆化县植被覆盖对土壤水蚀的影响分析

植被是连结土壤、大气和水分等自然要素的纽带,能够在很大程度上代表一个地区的生态环境总体状况。隆化县地处燕山北部的冀北山区南麓,属半干旱区向半湿润区过渡地带,土壤侵蚀以水力侵蚀为主。该文通过在隆化县全境均匀布点详细调查植被覆盖度、森林覆盖率及森林群落结构,分析植被覆盖对水力侵蚀的影响,并提出增加植被覆盖及调整林分结构的建议,为隆化县可持续发展和生态环境建设提供科学的理论依据。     

地震扰动区生态修复的概念与四拗

分析提出地震扰动区生态修复的概念,就是在重力侵蚀造成的植被破损处打＂补丁＂。进而分析了植被重建的土、水、树木种苗和当地人四要素的基本特性,分别为土碎、水漫、籽拗、羊狠,均具有执拗特质,合称＂四拗＂,是生态修复的难点所在,均具成败与否的决定性作用。     

磨盘山国家森林公园基础设施建设可能产生的水土流失及防治措施

对云南磨盘山国家森林公园基础设施建设可能造成的水土流失进行预测,认为施工期和自然恢复期可能产生的水土流失总量为3663t,基础设施建设区平均侵蚀强度为955t／hm^2·a,属微度侵蚀区,新增水土流失量为2951t．旅游服务及生态展示区和道路区为水土流失防治的重点区域．提出以具有水土保持功能措施为基础的水土流失防治措施．     

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.     

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.     

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。