竹材的霉腐与霉腐真菌

本文依据作者对竹材化学成分、竹材霉腐真菌和竹材防霉防腐技术多年研究的结果,以及其他相关资料,探讨了竹材霉腐与真菌种类、竹材化学成分的关系。把真菌对竹材的危害主要分为霉变、色变和菌腐３个类型,相应地也就把这些真菌分为霉变真菌,变色真菌和腐朽真菌三大主要类型。初步认定霉变真菌多隶属于半知菌亚门（Ｄｅｕｔｅｒｏｍｙｃｏｔｉｎａ）,腐朽真菌多隶属于担子菌亚门（Ｂａｓｉｄｉｏｍｙｃｏｔｉｎａ）和子囊菌亚门（     

云南西盟龙竹制品开裂与霉变问题的探讨

西盟龙竹竹材的化学成分与木材相比,淀粉、糖类及蛋白质等有机物质含量较高,在贮存期间及竹产品使用过程中容易发生霉变和开裂变形等质量问题。本研究分析了西盟龙竹开裂与霉变的原因,并提出了控制西盟龙竹开裂与霉变的措施。研究表明:对竹材原料进行合理选择和干燥处理、对竹材加工过程进行技术处理和质量控制、改变竹材的内应力和含水率可以有效控制竹制品的开裂;对竹材进行高温蒸煮处理、加压除霉处理和硫磺及紫外线处理等方法可以达到对竹材的除霉和控霉效果,提高竹材制品的使用寿命。     

新型绿色竹材防腐防霉剂研究进展

竹材中存在较多的营养物质,致使竹材易发生菌腐和霉变等。传统的防腐防霉剂虽能有效延长竹材的使用寿命,但因其含有一些化学成分会对环境和人体等产生一定的不良影响,所以更加环保、高效、持久、低成本的防腐防霉剂已成为竹材保护领域的研究热点。重点阐述了国内外新型绿色竹材防腐防霉剂的研究进展及存在的问题,以期为新型竹材防腐防霉剂的开发提供理论依据。     

腐朽过程中毛竹主要化学成分的变化

以毛竹为原料,选择1种白腐菌和2种褐腐菌对竹材进行腐朽试验,利用X射线衍射和傅里叶红外光谱等手段,测定竹材的失重率、相对结晶度和化学官能团。结果表明,随腐朽时间的延长,竹材的失重率不断增加,结晶度不断下降。通过对腐朽竹材主要官能团的观察,发现白腐菌的侵蚀能造成竹材主成分的分解,其中对木质素的分解能力更强。褐腐菌的侵蚀主要破坏竹材综纤维素。     

不同药剂处理毛竹的室内耐腐性

选择ACQ、铜唑、CCA、有机酸四类13种防腐剂对毛竹材进行处理,研究竹材的室内耐腐性能.结果表明:随着吸药量的增加,药剂对腐朽菌的抑制效力明显增加.ACQ防腐剂中,综合抗菌性能依次为ACQ-B、ACQ-D,ACQ-C对白腐菌的毒性最差,失重率约6%;铜唑类防腐剂对白腐菌的抗菌性最好的是CuAz-1,最差的是CuAz-2;对褐腐菌的抗菌性相差不大.通过对比,ACQ和铜唑类防腐剂的抗菌性与CCA相当,明显优于有机酸类防腐剂.     

竹材霉变生物学的研究*Ⅱ.不同竹材基质的抗霉性

对11个竹种和不同竹龄、部位毛竹的竹材进行了自然和人工接种致霉菌试验。测定结果的方差分析和多重比较表明，竹种间的自然抗霉性顺序依次为：黄槽毛竹＞毛竹＞浙江淡竹＞刚竹和石竹＞红竹和毛金竹＞签篌竹＞苦竹＞黄古竹＞茶杆竹，前二种为抗霉竹种，后四种为霉竹种。竹材的抗霉性与竹材的预处理方法和贮存条件有相互作用，冬伐毛竹材的抗霉性随竹株年龄增长而增强，长至5－6度的毛竹，其竹材抗霉性极显著地高于2－4度的毛竹；毛竹杆材上部的抗霉性极显著地高于中、下部。     

竹材霉腐真菌研究

作者在多年竹材防护技术研究中,确认了引起竹材霉变腐朽的真菌５０多种,已鉴定５２种（个别只鉴定到属）,分属４亚门、６纲、１０目、１８科、３１属。其中２／３以上,作为竹材霉腐真菌,尚未见报道,尤其是竹材腐朽担子菌２纲、４目、９科、１４属１７种,属首次报道。     

竹材霉变生物学的研究 Ⅲ.环境条件对毛竹材霉变的影响*

用自然接种后套皿异温异湿培养法和人工接种毛竹材致霉菌混合液后同温异湿培养法,对4～5度的毛竹冬竹材和秋竹材进行霉变测定,结果表明:在温热条件下(26～32℃),毛竹材在饱和湿度时霉变最严重,霉变程度与湿度成正相关。用分月暴露后套皿保湿法对毛竹4度(8年生)冬竹材进行霉变测定,结果表明:全年12个月中,七月、二月和一月暴露的毛竹块材,霉变程度极显著地低于其他9个月份,分析系因该三月气温气湿不利于致霉菌在毛竹材上定殖繁育之故。提出两种用于竹材抗霉性快速测定及防霉处理效果评估的实验室方法和供目前生产上暂用的竹材霉变程度分级标准;并根据研究结果,提出了适于生产上采用的几点竹材防霉建议。     

草坪腐霉枯萎病防治措施

草坪腐霉枯萎病在气温高、雨水多、湿度大、土壤含氮量高或在碱性土壤中，易加重病害的发生，会危及整块草坪。从给草坪营造良好的立地条件，精心管护幼苗，合理施肥，浇水，及时喷药预防等方面提出了防治草坪腐霉枯萎病的关键措施。     

过氧化物和次氯酸盐对竹材除霉脱色效果的研究

用木材中广泛使用的过氧化物和次氯酸盐等漂白剂对竹材进行除霉脱色试验证实:过氧化物和次氯酸盐对此同样有效。其中过氧化氢处理效果好,工效高,操作手续简便,脱色均匀,对环境不产生污染;其次是过氧化钠,次氯酸钠效果较差。竹材和竹制品的除霉脱色宜以过氧化氢为主。     

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.     

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。