四川松树、桉树外生菌根菌种类调查

对四川省马尾松、湿地松、火炬松、桉树等人工幼林及少数天然林的外生菌根菌进行了调查研究。研究表明,我省松树林下外生菌根真菌资源丰富,鉴定出9科18属50种,其中马尾松林下有40种,占80％,松、桉幼林下的种类单一、采色豆马勃、多根硬皮皮勃、黄色须腹菌为松类人工幼林下的优势菌根菌,随着树龄的增加,菌根种类也不断增加。桉树林下仅发现大孢硬皮马勃。     

真菌共生物——采色豆马勃

采色豆马勃(Pisolithustinctorius)是一种外生菌根真菌,能生存在树苗的根上,是松苗的一种有前途的外生菌根共生物。具有这种真菌的树苗能在恶劣的土壤条件下生长,而且比在良好生长条件下具有其他真菌外生菌根的树苗生长得快。1973年美国把在亚拉巴马、佐治亚和宾夕法尼亚松树下采集的采色豆马勃担孢子接种体和从佐治亚培养的营养接种体人工引入佐治亚、佛罗里达和北卡罗来纳州的三个苗圃的土壤中。经过一个生长季节后,在北卡罗来纳州的苗圃里,由营养接种体形成的采色豆马勃外生菌根使火炬松苗的生长增长了140%,而弗吉尼     

马尾松外生菌根菌的培养和育苗效应研究

对彩色豆马勃、厚环乳牛肝菌、血红铆钉菇等７株菌根菌株在４种培养基、３种温度梯度下的生长状况和马尾松苗期接种效果进行研究。结果表明：改良麦芽汁培养基是外生菌根菌的适宜培养基；彩色豆马勃适应力强，明显促进马尾松苗期生长，菌根感染率高，但各菌株之间存在差异；厚环乳牛肝菌不适宜马尾松的苗期生长。     

马占相思菌根调查及利用

马占相思菌根调查及人工接种结果表明 :马占相思在自然界能形成外生菌根及VA菌根。在贫瘠的立地条件下 ,外生菌根的子实体多 ;在较肥沃的立地条件下 ,外生菌根的子实体少 ,优势外生菌根菌是多根硬皮马勃菌 (Sclerioermapolyrhium)。马占相思对VA菌有较强的选择性和其特定的优势VA菌根菌 ,即从马占相思根部分离的VA菌。用优势外生菌根菌及优势VA菌根菌对马占相思苗木进行接种 ,都能形成菌根 ,且都能显著地提高马占相思的生长。马占相思优势VA菌接种效果优于多根硬皮马勃菌     

马占相思菌根调查及利用

马占相思菌根调查及人工接种结果表明：马占相思在自然界能形成外生菌根及VA菌根。在贫瘠的立地条件下，外生菌根的子实体多；在较肥沃的立地条件下，外生菌根的子实体少，优势外生菌根菌是多根硬皮马勃菌（Sclerioerma polyrhium)。马占相思对VA菌有较强的选择性和其特定的优势VA菌根菌，即从马占思根部分离的VA菌。用优势外生菌根菌 及优势VA菌根菌对马占相思苗木进行接种，都能形成菌根，且都能显著地提高马占思的生长。马占思优势VA菌接种效果优于多种硬皮马勃菌。     

外生菌根真菌菌剂的制备及其对松苗生长效果的研究*

从不同林型下分离获得的外生菌根真菌纯培养菌株中,选择了劣味乳菇、美味红茹、赭丝膜菌、彩色豆马勃四株菌根菌,进行菌剂制备及其对松苗生长效果的试验。结果表明,PDMA和PD培养基是培养外生菌根真菌较适合的培养基,木屑、麸皮、米糠、玉米粉、珍珠岩、蛭石等是培养菌根菌菌剂较适宜的基质。供试菌对油松、马尾松、落叶松、樟子松、红松苗都具促进生长作用,效果较明显的是丝膜菌,其次是劣味乳菇、美味红菇、彩色豆马勃;对促进火炬松苗生长效果最明显的是劣味乳菇,其次是美味红菇、彩色豆马勃。四种菌对湿地松苗生长效果均高于对照。     

毛白杨苗期VA菌根菌与外生菌根菌接种的研究

1998～1999年在田间条件下布置了毛白杨VA菌根(包括根内球囊霉菌和单孢球囊霉菌)与外生菌根硬皮马勃混合接种试验.结果表明接种菌根菌对毛白杨苗高生长量有促进作用,且以根内球囊霉菌作用最明显,单孢球囊霉菌处理次之,硬皮马勃处理最差.水涝大大降低人工接种菌根菌的效果,严重影响VA菌根和外生菌根菌单独接种及混合接种的效应,根内球囊霉菌甚至会抑制毛白杨苗木的高生长,VA菌根和外生菌根间的负交互作用也不对苗高生长产生影响.菌根真菌的感染率随时间变化出现较大的波动和变化.     

几种外生菌根菌对松苗抗非根部病害的影响

研究几种外生菌根真菌对松苗抗松枯梢病和抗松材线虫病的影响.结果表明:菌根菌增强了马尾松苗苗木对松枯梢病的抵抗力,其中华美牛肝菌(504)菌根苗的抗性最强,其次为黄豹斑鹅膏(EG)和彩色豆马勃Pt2菌根苗,彩色豆马勃Pt,和紫金蜡蘑(ZJ)菌根苗的抗性相对较弱;但外生菌根菌对湿地松苗苗木抗松枯梢病的能力未见提高.对黑松和马尾松菌根苗接种松材线虫后发现,菌根增强了黑松和马尾松对松材线虫病的抵抗力,延缓或减轻了苗木的死亡,以504、Pt2和EG的效果较好.黑松菌根苗接种松材线虫后各处理体内早期的PAL活性存在一定差异.对松材线虫抗性较强的菌根苗其体内PAL酶活也较高,反之亦然.供试外生菌根菌的促生作用以及菌根苗体内抗病代谢酶活性的变化与其抗病性有一定的相关性.     

落叶松外生菌根合成条件的研究

本文研究了厚环乳牛肝菌、赭丝膜菌、彩色豆马勃、血红铆钉菇 4种菌根菌 ,在纯培养条件下对土壤温度和含水量 2个生态因子的适应性 ,以及同日本落叶松和长白落叶松形成外生菌根的能力。结果表明 ,土壤温度和含水量对菌根生长、菌根侵染率具有很大影响。其中厚环乳牛肝菌和彩色豆马勃具有很强的耐温湿性 ,而赭丝膜菌和血红铆钉菇则稍差。在菌根纯培养合成中 ,供试菌株均与落叶松形成了外生菌根。接种后苗木的各项生长指标均比对照有所提高。     

东北主要用材树种外生菌根真菌资源调查研究

通过对我国东北地区主要用材树种外生菌根真菌资源、种类及分布进行详细调查研究，分析了树种、林龄与菌根真菌分布之间的相互关系；菌根真菌的分布、种类随林龄的增加而发生变化。结果表明，与落叶松、樟子松、油松、杨树等主要用材树种共生形成外生菌根的真菌共76种，8－20年生松林下多以牛肝菌类、乳菇类等伞菌目的菌根真菌为先锋种类；20年生以上的成熟林则以专一寄宿性的铆钉菇科和马勃目的菌根真菌为优势种群。为我国东北地区主要用材树种外生菌根真菌的采集、分离、培养，优良菌根真菌的筛选和菌根真菌资源的合理开发利用提供了理论基础。     

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.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

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.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.