太行山侧柏人工林林冠降雨截留及地表径流的研究

对侧柏人工林分的林冠降雨截留及地表径流进行观测，要冠降雨截留量与降雨量相关，截留量随降雨量的增加而增加，截留率则相反，年截留率３３％；地表径流量和土壤侵蚀量与降雨量正相关，年地表径流量和土壤侵蚀量分别为３９．５ｍｍ和１３２７ｋｇ／ｍｈ＾２。     

杉木幼林水土流失及养分损耗的研究

对设置于江西分宜县中国林科院亚林中心５组不同整地方式水土流失多年观测结果进行了综合分析。地表径流量从１４７～１３２２ｍｍ,平均为５４６ｍｍ。径流系数从００９８％～０８５２％,平均为０３６９％,年均土壤侵蚀量从０００５１～０２５１０ｔ／ｈｍ２,平均为０１００５ｔ／ｈｍ２。整个幼龄林阶段,地表径流量５４６０ｍ３／ｈｍ２,土壤侵蚀总量为１００５０ｋｇ／ｈｍ２;养分损失量：Ｎ１９５６０ｋｇ／ｈｍ２,Ｐ２２３７０ｋｇ／ｈｍ２,Ｋ２６７７７ｋｇ／ｈｍ２,有机质５００４９ｋｇ／ｈｍ２。分析认为在板、页岩风化物上发育的黄红壤,特别是腐植质层较厚结构良好的土壤,具有较强的抗腐蚀能力,不管采用哪种整地方式均无明显的水土流失和养分损失,但比较而言,以穴垦为最佳选择。水土流失还不是此种土壤上杉木人工林的地力退化的最主要的原因。     

哀牢山木果石栎林降雨过程中的养分循环

本文以云南哀牢山国家级自然保护区中山湿性常绿阔叶林的主要森林类型——木果石栎林为研究对象，分析了大气降雨对该生态系统的养分循环。结果表明，以大气降雨、穿透雨和树木干流为养分输入，以地表迳流和土壤渗漏为养分输出的养分循环过程中，Ｎ、Ｐ、Ｋ、Ｃａ等分别增加了１５．９４１ｋｇ／ｈｍ~２·ａ，０．３５３ｋｇ／ｈｍ~２·ａ，３．８３ｋｇ／ｈｍ２·ａ和１．２０１ｋｇ／ｈｍ~２·ａ，而Ｍｇ减少了０．６５４ｋｇ／ｈｍ~２·ａ。     

盆北山地严重侵蚀坡面几种人工林水文效应研究

森林在不同程度上对天然降雨起着截流，吸收的作用，本文系统的研究了桤木、湿地松、洋槐、桤木×湿地松混交林的冠层，凋落层及土壤层的水文效应，不同人工林类型在这三方面均同差异，林冠截留率１５．１％￣１９．３％，凋落层有效拦蓄量１．４３￣１７．８８ｔ／ｈｍ＾２，土壤０ｃｍ￣２０ｃｍ层贮水量３５．５￣１０７．５ｔ／ｈｍ＾２，森要的存在，改善了土壤的物理性质，从而改变了土壤的调蓄功能，严重侵蚀坡面自然条件恶劣     

杉木福建柏混交林效益研究

通过对杉木福建柏混交林中单株生物量组成、土壤团粒组成、土壤孔隙和水分状况的研究分析， 结果表明： 混交林中杉木每ｈｍ ２ 蓄积量是杉木纯林的１６９ 倍， 细根量是杉木纯林的１５ 倍； 与纯林相比， 混交林中０～２０ｃｍ 土层＞ ０２５ｍ ｍ 水稳性团聚体高出９０１％ ； 结构体破坏率低１５８２％ ； 有机质和水解性 Ｎ 含量分别高０２４５％ 和１３１×１０－ ６； 毛管孔隙、非毛管孔隙、总孔隙高００９％ 、０９１％ 、１００％ ， 土壤容重低００５７ｇｃｍ － ３； 最大持水量、最小持水量、毛管持水量分别高３００％ 、３５０％ 、２０４％ ； 混交林４０ｃｍ 土层含水量也比纯林大１５５ｔ·ｈｍ － ２。由于混交林的结构较为合理，能一定程度改善土壤理化性质、提高林分生产力，是一种值得推广的造林模式。     

锐齿栎林生态系统的地球化学循环规律研究

运用系统学的方法和小集水区技术，对秦岭山地的锐齿栎林生态系统的地球化学循环规律进行了定位研究。结果表明，大气降水向系统输入的养分总量为３３．２８９ｋｇ·ｈｍ－２ａ－１，通过迳流输出的养分量为１７．０１１ｋｇ·ｈｍ－２ａ－１，净累积养分１６．２７８ｋｇ·ｈｍ－２ａ－１，变化率为４８．９１％，表明锐齿栎林生态系统处于进展的变化过程中。同时，讨论了森林冠层对大气降水携带养分的再次分配规律。     

不同整地马尾松工程幼林地水土保持效益的研究

１９９１～１９９６年,通过建立径流小区的方法,对广西桂平市不同整地马尾松工程幼林地的水、土、肥进行了连续的定位观测。结果表明：不同整地马尾松工程幼林地的年平均液体径流量为全垦（１３４８５０ｔ／ｈｍ２）＞带垦（１１３８３９ｔ／ｈｍ２）＞穴垦（１０９４９１ｔ／ｈｍ２）;年土壤流失量为全垦（９３１３ｔ／ｈｍ２）＞带垦（４０９０ｔ／ｈｍ２）＞穴垦（１９１７ｔ／ｈｍ２）;年平均水土养分流失量为全垦（１６６１７ｋｇ／ｈｍ２）＞带垦（７６２７ｋｇ／ｈｍ２）＞穴垦（３９８２ｋｇ／ｈｍ２）,分别是灌草坡（２０１４ｋｇ／ｈｍ２）的８２５１％、３７８７％和１９７７％。不同整地造林后第６年时的土壤养分含量（有机质、全Ｎ、水解Ｎ、速效Ｋ）比造林前存在下降趋势,下降的总频率为全垦（２０４％）＞带垦（１０６％）＞穴垦（５３％）。结果表明,穴垦整地（４０ｃｍ×４０ｃｍ×３０ｃｍ）马尾松工程幼林地具有显著的水土保持效益。建议在我国南方推广应用。     

The Optimum Thinning Intensity and Water Productivity of Black Locust Forest on Loess Plateau

为了确定黄土高原地区现有刺槐林改造的最佳间伐强度,１９９５年秋季对密度为２２２０株／公顷的９年生刺槐林进行了三种不同强度的间伐．通过间伐,降低了群落密度,减少了林冠截留率,增加了植树带内的汇流量,根系层内的土壤水分条件得到明显的改善．当间伐后的林分密度为１１１０株／公顷时,生长季内植树带土壤水分提高约４０％．随着间伐强度的增大,林木的水分生产函数曲线由直线上升变为以对数曲线上升;当间伐强度达到某一值时（保留密度为１１１０株／公顷）,林木水分生产力随蒸腾量的变化曲线为抛物线．这表明此时水分已不再是林木生产的限制因子,在这种间伐强度条件下,单株林木和整个林分的水分生产力分别达到６０１７１ｇ·ｋｇ－１·ｍｍ－１和１４９７７７ｋｇ·ｈｍ－２·ｍｍ－１,因此将这一强度定为黄土高原地区刺槐林间伐的最佳强度．     

热带山地雨林生态系统水文化学循环规律的研究

根据５ａ定位观测，对尖峰岭热带山地雨林更新林生态系统的水文化学循环规律的数据分析表明，年均降雨量为２６６８．３ｍｍ，其中总径流量占４６．７％，蒸散量５３．３％，冠层截留量１４．０％。Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ的年均降雨输入量为７８．４ｋｇ／（ｈｍ２·ａ），总径流输出５６．７ｋｇ／（ｈｍ２·ａ），净积累２１．６ｋｇ／（ｈｍ２·ａ）；Ｓｉ、有机Ｃ、Ａｌ、Ｍｎ的年均降雨输入量为２５．０ｋｇ／（ｈｍ２·ａ），总径流输出为１１２．３ｋｇ／（ｈｍ２·ａ），净损失８７．３ｋｇ／（ｈｍ２·ａ），更新林系统仅处于更新进展过程中，同时证实了冠层对降水化学的淋溶效应，净淋溶系数达４．１１；提出了降雨、林内净降雨、总径流的各水化学物含量与其相应水量的回归模式     

造纸车间主要设备及工艺流程简介

方正林业造纸厂是我国林业系统最大的造纸厂，产品品种为挂面牛皮箱板纸，设计规模为３．４万ｔ／年。造纸车间原料为：以制浆车间来的阔叶材半化学浆为底浆，以针叶材化学浆为面浆。１打浆工段１．１主要设备①ＺＮＷ２１型圆网浓缩机面积５ｍ２；转鼓规格１５００ｍｍ×１０６５ｍｍ；生产能力３～３．５ｔ／ｍ２·ｄ；进浆浓度１％～２％，出浆浓度４％。②ＺＮＷ２３型圆网浓缩机面积１５ｍ２；转鼓规格１５００ｍｍ×３３３０ｍｍ；生产能力３～３．５ｔ／ｍ２·ｄ；进浆浓度１％～２％；出浆浓度４％。③４５０双盘磨ＺＤＰ-１１型，…     

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.     

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.     

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.     

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.     

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.     

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。