双稠哌啶类生物碱分子结构与杀线活性间关系

使用培养基法和棉球法测定了苦豆碱、野靛碱、甲基野靛碱、苦参碱对松材线虫的杀线活性。两种生测方法测得的结果一致,表明苦豆碱的杀线活性最强,其ｌｏｇ（１／ＩＤ５０）（ｍｏｌ／棉球）＝８．６７,与文献中用同样方法测定的对松材线虫杀线活性的其它７种双稠哌啶类生物碱的杀线活性相比较,它也是最强。本文提出了双稠哌啶类生物碱对松材线虫的杀线活性强弱主要受其分子结构中官能团对的类型及其中的官能团的类型控制的假说。根据这一假说,推测了具高杀线活性的生物碱的分子结构。     

苦豆碱防治松材线虫病的林间试验

在国家自然科学基金的资助下，我们在筛选到天然化合物—苦豆碱具有对松材线虫极强的杀线活性［１］的基础上，进一步进行了用苦豆碱防治松材线虫病的多次林间试验，发现苦豆碱制剂具内吸性，能成功地控制松树中松材线虫的繁殖，使病松树得以康复。在林间试验证实苦豆碱剂...     

克线磷防治松材线虫病的研究

为防治松材线虫病，１９８８－１９９２年间，使用３种药剂对松材线虫（Ｂｕｒｓａｐｈｅｌｅｎｃｈｕｓｘｙｌｏｐｈｉｌｕｓ）进行室内毒性测定，并选用５％克线磷颗粒剂在林间、盆栽树苗上作防治试验．巴丹在１００×１０－６时，线虫仍可存活、繁殖；Ｆ—００１药剂在５０×１０－６以上时，灭虫率均可达９０％以上，克线磷浓度在６０×１０－６以上时，则可完全抑制线虫的生长繁殖．在林间，以克线磷处理的黑松（Ｐｉｎｕｓｔｈｕｎｂｅｒｇｉｉ）植株，均比对照株死亡率低．盆栽苗上的施药、接种试验，更进一步证实了该药剂的防病效果．     

嘧啶氧磷对松材线虫的有效杀线活性

通过24孔板测定了几种农药原药和乙醇对松材线虫的杀线活性。试验结果表明嘧啶氧磷杀线活性最高,它的致死中浓度LC50为32．65μg／mL,95％的置信区间为25．08～42．51μg/mL;体积分数为5％的乙醇在20min内使94．4％的松材线虫麻痹,体积分数为10％的乙醇在90S内将96．7％的线虫杀死。另外,松材线虫浸入供试药剂的时间越长,所测定的LC50的值越小,克百威、灭线磷、嘧啶氧磷的LC50值从24h到72h分别由448．47,51．96,94．54μg／mL降低至51．47,36．94,32.65μg／mL。     

几种物质对松材线虫的作用

松材线虫病是松树的一种毁灭性病害。本文选用了几种物质，采用浸泡生测法和棉球生测法测定了其对松材线虫的作用。结果表明，阿维菌素对松材线虫的杀线活性较强，米乐尔次之，狼牙刺种子粗提物和氯化铵的杀线活性均较弱，氯化钙则无杀线活性。阿维菌素和米乐尔对松材线虫繁殖均有较强的抑制作用，狼牙刺种子粗提物的抑制作用较弱，氯化铵无抑制作用，而氯化钙对松材线虫的繁殖具有促进作用。     

毛竹及浙江淡竹根际联合固氮的研究*

对毛竹和浙江淡竹利用Ｎ２回充法测定根系固氮活性，分别可达９．９和２．１ｎｍｏｌＣ２Ｈ４／（ｇ干根．ｈ）；用半固体培养基富集后的极系固氮活性范围在２０－１００ｎｍｏｌＣ２Ｈ４／（ｇ鲜根．ｈ）的占４０％以上。对浙江淡竹根据各部位固氮菌数采用乙炔还原－ＭＰＮ法计测结果是根际土壤３．４×１０＾５菌数／ｇ干土；根表、根内分别为２．２×１０＾５，３．０×１０＾４菌数／ｇ干根。采用划线法在浙江淡竹根际分离到３株     

8种化学药剂单独及两两联合染毒对松材线虫杀灭作用试验

8种药剂单个药剂的染毒结果表明，阿维菌材线虫即有较强的杀灭活性，其半数致死浓度（LC50）分别为0．0601mp／L和8.35mg／L，其LC50的95％可信区间（95％CI）分别为0．0416～0．0868mg／L和6．16～11．34mg／L。甲胺磷对松材线虫的毒性次之，其IC50为3282．46mg／L（95％CI为2779．71～3872．58mg／L），其它几种测试药剂（三邻甲苯基磷酸酯、甲醚菊酯、溴氰菊酯和吡虫啉）的杀线活性很弱。联合染毒测定的结果表明，阿维菌素与硫酸铜、溴氰菊酯与硫酸铜以及溴氰菊酯与涕灭威分别联合使用对松材线虫表现出毒性增强作用（P〈0．01），蜕明这几荆坝临嬉秭职抖燃虫的毒杀作用具有协同效应。     

松细枝+培养皿法分离镜检松材线虫试验

将松树上的1，2，3龄枯枝或萎枝条切成薄片，置培养皿分离线虫，镜检表明，枯萎松枝条上松材线虫检出率为52．4％，其中马尾松枝条检出率为75.0％，黑松枝条检出率为30．8％；1年生枝条检出率为37．5％，2年生枝条检出率为45．0％；针叶灰色样本检出率为33．3％，针叶枯黄样本检出率为57．1％。检出含有松材线虫的样本共重30．98g，共检出松材线虫39条，平均1．259条／g，其中马尾松样本平均1．093条／g，黑松样本平均1．508条／g。该法可用于松材线虫病的早期诊断和防治。     

一株具有杀松材线虫活性细菌的筛选和鉴定

为了筛选对松材线虫（Burrmphezen曲“5xylophilus）具有较高杀线活性的细菌,作者从腌制芥菜的表面分离出了一株对松材线虫具有较高杀灭活性的细菌,命名LZ～01。经形态学观察、生理生化分析及对该菌16SrDNA序列分析,将该茵鉴定为BacilluscereusLZ-01。利用该菌培养滤液对松材线虫的杀灭活性进行了检测,结果表明：处理10h时松材线虫的校正死亡率可达100％。     

绿僵菌Mf2菌株对松材线虫的毒力测定

为探索绿僵菌Metarhigium anisopliae Mf2菌株对松材线虫的毒杀效果,从4种常见培养基PDA,PPDA,SDAY,SMAY中选择一种最适于绿僵菌Mf2菌株营养生长及产孢的培养基,测定该菌株对松材线虫的毒杀活性。结果表明,Mf2菌株在PPDA培养基中生长速度最快,14 d后菌落直径大于其他3种培养基,为76.00 mm;培养14 d后PPDA培养基中菌株产孢量最高,为5.667×1010个孢子,显著高于其他培养基上的产孢量,约为处于第2位的PDA培养基上产孢量的2.5倍;绿僵菌Mf2菌株具有较高杀线虫活性,处理36 h后校正死亡率为98.52%。绿僵菌Mf2菌株对松材线虫毒力测定表明具有很高的毒性,有良好的应用前景。     

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.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.