石竹出笋退笋规律研究

对石竹出笋退笋规律的研究表明 ,石竹出笋时间始于 5月 1日左右 ,历时约 36d ,出笋初期出笋少 (持续时间 12d左右 ,占 11 1% ) ,盛期出笋数较多 (持续时间 18d ,占 83 9% ) ,末期出笋数迅速下降 (持续时间 6d ,出笋占 5 0 % ) ,初期出土石竹笋退笋少 ,以后退笋率不断增加 ,但末期退笋率又有所下降。随着笋期的推移 ,退笋高度不断增加 ,退笋生长时间缩短。     

云南方竹出笋成竹规律

对云南省澜沧县境内分布的云南方竹出笋成竹规律进行了研究。结果表明：云南方竹出笋期为9月下旬至11月上旬,历时约40 d;初期笋的成竹率最高(达91.67%),末期笋的成竹率最低;新竹秆高、胸径分别集中在3.51～5.00 m和1.51～2.50 cm;末期笋退笋较多,退笋高度主要集中在40 cm以下;引起云南方竹退笋的主要原因是养分供给不足,其退笋数占退笋总数的73.33%;云南方竹的高生长持续70 d左右,呈现出“慢—快—慢”的生长规律。研究结果可为云南方竹的推广应用提供科学依据。     

寿竹出笋及竹笋-幼竹高生长规律

通过对寿竹出笋和幼竹高生长阶段的调查,研究了寿竹笋期的生长发育规律。结果表明,寿竹出笋从5月初开始,出笋盛期为5月8日到5月21日,盛期出笋数量占84.7%,出笋全部持续时间约30天。寿竹的高生长持续60天左右,高生长符合Logistic模型。引起寿竹退笋的主要原因是虫害,占退笋的比例74.7%,造成退笋的主要害虫是竹笋泉蝇。该地区寿竹整个出笋期平均成竹率仅为11.7%。     

江苏淡竹笋期生长规律的研究

经过３ａ观察研究，初步明确了江苏淡竹笋期生长规律：（１）出笋期为４月下旬到５月中旬，历时２５ｄ左右。（２）退笋数与出笋数的相关系数ｒ＝０．９７９，全林退笋率为８０％，且随时间和持续逐渐上升。退笋高度在５０ｃｍ以下均有发生，退笋原因主要是养分供应不足和虫害。（３）成竹数与出笋数变化趋势一致。（４）成竹高生长历时４５ｄ左右，总生长量，月平均生长量分别为９７５，２３．７８ｃｍ。     

黄甜竹生长发育规律初步研究

对黄甜竹生长发育规律进行了初步研究,结果表明:黄甜竹发笋期从4月中旬开始至5月上旬止,持续时间约25 d,出笋规律呈偏右正态分布。黄甜竹平均成竹率为61.36%,发笋前期和盛期成竹率相当。幼竹高生长历时45 d,高生长总量可达7～8 m。     

金佛山方竹无性系种群生长规律的研究

对镇雄县境内分布的金佛山方竹出笋规律进行了研究,结果表明:金佛山方竹出笋期在9月下旬至11月上旬左右;退笋多出现在出笋末期;平均出笋成竹率为76.92%;高生长遵循慢-快-慢的过程,持续时间约45d左右;昼夜总生长量达19.84cm,白天生长量是夜间生长量的1.04倍。     

北京地区早园竹高生长规律及出笋长竹期的养护技术

本文以北京地区生长的早园竹（Phyllostachys propinqua）为研究对象,调查了早园竹的高度生长及竹林出笋规律。结果表明：竹笋的出笋时间不同,其成竹率也不同。出笋早的竹笋的成竹率较高;出笋越晚,竹笋的成竹率越低。据此可将早园竹的出笋期分为3个阶段：前期,中期,后期。3个阶段的时间大致相等,约为6-7d。前期笋的高生长期长、后期笋的高生长期短,它们高生长期的结束时间基本一致。早园竹的高生长遵循“慢一快一慢”规律,竹笋破土后14d和36d左右是高生长期的2个转折点,由此可将早园竹的高生长分为始期、盛期、末期3个阶段。早园竹的日最大高度生长量为51～75cm,占成竹平均高度的6．96％～9．04％。同时对早园竹出笋长竹期的养护技术进行了探讨。     

吊丝单笋期生长特性研究

为探明夏秋季笋用良竹吊丝单的笋期生长特性和提高竹笋单产,通过多年的定时定位测试,系统研究了该竹的林分笋期.竹丛笋期、出笋数量的时间分布,发笋与母竹基础的关系,退笋规律。成竹规律、幼竹生长的季节变化和昼夜变化节律及其与气象因子的关系。结果表明:①笋期15/6～18/10,历时126天,其中大暑至立秋为出笋盛期,发笋量占总数的40％。发笋数量的时间分布为偏正态。②丛发笋数随竹丛的增大而增加,r=0.99;株母竹发笋数随竹丛的增大而减少,r=—0.711。以丛留母13～15株的竹笋最有利于竹笋单产的提高。全林的丛发笋数和株发笋数分别为6.21和0.79株。③湿笋数与出笋数的相关系数r=0.783;全林退笋率14％,其中以盛期为低;退笋高度60cm以下,多在10～20cm之间,占54.1％。④高生长历期113天,累积生长量、日均生长量分别为894.1、7.91cm,其中昼夜分别贡献77.6％、212.4％。生长以立秋至白露期间为快,在1/3生长期内,生长量占2/3。夜间生长速率是昼间的三倍多。⑤高生长量(y)与日均温(x1),日温差(x2)、降雨(x3)间的回归方程式为y=2.729+0.268x1—0.184x2+0.032x3,其中湿度的影响达显著水平。复相关R=0.463。     

糙花少穗竹发笋及幼竹高生长规律的研究

对糙花少穗竹发笋期及幼竹高生长的研究表明 :糙花少穗竹发笋期在 2月中旬至 5月上旬 ,发笋初期在 2月中旬至 3月上旬 ,出笋株数占整个生长期出笋总数的 17.6 % ,笋重占 14 .5 % ;发笋盛期在 3月中旬至 4月下旬 ,出笋株数占整个生长期出笋总数的 72 .1% ,笋重占 78.1% ;发笋末期在 5月 ,发笋株数占整个生长期出笋总数的 10 .3% ,重量占 7.4 % ;发笋初期平均单株笋重0 .378kg,盛期平均单株重笋 0 .4 97kg,末期平均单株笋重 0 .32 9kg,表现为 :盛期笋 >初期笋 >末期笋 ;糙花少穗竹幼竹高生长高峰在笋出土后第 3～ 33d,高生长初期平均生长量 7.93cm· d-1,后期平均生长 4 .4 4cm· d-1,最大日生长量为 2 4 cm,整个生长期平均日生长量 15 .13cm。     

金明竹在泰州地区发笋退笋规律研究

采用定点观测法,对金明竹在泰州市海陵区江苏农牧科技职业学院校内实训基地进行发笋和成竹规律进行了实测研究,结果显示:金明竹在泰州的出笋期开始于5月15日,结束于6月11日,出笋盛期约在5月23日~6月1日,盛期出笋量占笋期总出笋量的68.03%,出笋总时间约28 d。笋体高生长遵循慢—快—慢规律,早期出的笋所需时间较长,其高生长时间持续时间较长,晚期出的笋所需时间相对较短。金明竹退笋与出笋时间及笋体高度有关,随出笋时间推迟退笋率呈增大趋势,平均退笋率为45.15%;其中退笋高度主要集中在40 cm以下,以30 cm以下占比最多,达到77.61%。     

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.     

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.     

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.     

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.     

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。