云南松母树林不同疏伐强度促进结实的效应

母树林结实量受控于树冠体积,而树冠发育状况为林分郁闭度所制约。单株结实量还与立木个体的生殖生长特性,生长发育状况(生长级)有关。疏伐是改建云南松母树林的关键技术措施,它对于促进母树树冠发育,提高单株及单位面积结实量具有明显的效应。试验研究表明,采用疏伐措施控制母树林分的郁闭度为0.3,可使单株及单位面积的结实量达高水平。     

生物农药用银杏优良无性系的选育

以40个20年生银杏无性系为研究对象,研究了外种皮酚酸含量、单株种实产量、出皮率和单株经济产量的变异规律.结果表明:不同无性系间的单株产量、酚酸含量、单株经济产量差异显著,出皮率达到显著性水平.结合银杏无性系的种实产量、出皮率、外种皮酚酸含量和单株经济产量,采用欧氏距离和最长距离法进行聚类,把40个无性系分成4大类.其中第四类(16号(南林外1)、38号(南林外2))无性系的外种皮酚酸含量高,单株种实产量高,外种皮出皮率中等偏高,单株经济产量最高,可以为新型生物农药银杏定向栽培提供材料,具有较高的引种试验和推广潜力.     

油橄榄高接换种经验小结

<正> 不同的油橄榄品种、类型或单株,有其不同的开花结实特性,有的结实年龄较早,有的结实年龄较晚;有的单株产量较高,有的单株结实较少.这种不平衡的现象,对提高单位面积产量具有一定的影响. 为此,我们从1979年开始进行了高接换种工作,以取代一部分在我所表现不太良好的品种、类型或单株,如实生爱桑、柳叶卡     

湖南不同板栗品种结实性研究初报

为了加快板栗良种的选育进程,了解湖南各地选育板栗良种的结实特性,将湖南省各地区选育出的板栗品种1~11号与湖南本地推广板栗良种铁粒头(作为对照CK)进行了品比试验,并就树体冠幅面积、单株果实个数、单位冠幅面积果实个数、单株产量、单株栗苞产量、单株坚果产量、出实率及板栗果实各项生长指标间的相关性进行了调查、观测与分析。结果表明:板栗品种5、7、9、11号在单位冠幅面积果实个数、单株果实产量及结实性等方面的表现均比CK突出,尤其是板栗品种7号,可作为下一步良种选育的研究对象;在板栗果实各项生长指标中,栗果长与栗果宽存在显著正相关,与栗果高存在极显著正相关,而栗果宽与坚果皮厚存在负相关;坚果长与坚果宽和坚果高均存在极显著的正相关,坚果宽与坚果皮厚存在负相关;平均单株产量与单株栗苞质量和单株坚果质量均存在极显著的正相关,而板栗果实的出实率与树体冠幅面积存在极显著的相关性。文中因此认为,合理控制冠幅,不仅可以提高单株产量,还可以提高板栗果实的出实率。     

银杏良种早实技术研究

在广西桂北银杏产区采用‘大佛手’、‘大马铃’、‘华口大白果’3个银杏良种营建矮化、密植、早实丰产示范林111.30 hm2,辐射林459.06 hm2,经过大耐性推广应用,达到了3～5年挂果,6～8年投产的目标.示范林和辐射林总产银杏142.22万kg,产值达2 275.5万元.经过试验分析,常规施肥的平均单株新梢量高于对照3.1倍,新梢长度高于对照的1.13倍,单株产量高于对照1.74倍;配方施肥的平均单株产量高于对照1.25倍,种实出核率高于对照15%;人工疏果的平均单抹新梢量高于对照3.11倍,新梢长度高于对照1.15倍;疏果的植株种实浮水率仅1%,而对照的种实浮水率达86.4%.对7～8年生的银杏示范园进行调查分析,采用早实良种建园的产量均优于常规品种,其中华口大白果品种平均单株产量高于常规品种4.2倍;大佛手品种平均单株产量高于常规品种2.0倍;大马铃品种平均单株产量高于常规品种3～4倍.     

嫁接方法对银杏丰产的影响研究

银杏因结果晚而俗称"公孙树",通过嫁接可提早结果。为探索不同的嫁接方法对银杏丰产的影响,对定植9 a的实生银杏树进行高接换冠,选用不同的接穗和嫁接方法进行试验,嫁接后第5年和第8年测定产量和树冠偏冠度。对单株产量和偏冠性进行方差分析和多重比较,结果表明:2a生和3 a生枝条高枝接换冠既能保证早期产量,又能解决银杏偏冠问题,后期丰产优势明显,可延长盛产期限。     

檫树优树选择和嫁接

一、优树选择1.优树的标准(1)优树应比同林分内五株优势木的平均单株材积大50%以上。(2)实生,树龄10年以上;(3)树干通直园满,树皮较薄而光滑;(4)树冠较窄,侧枝细,浓密,冠形呈园锥形;(5)长势旺盛,有良好的正常的结实性;(6)未遭受任何病虫危害。2.选择步骤     

橄榄优良品系“粤榄18”适应性试验

在高州市三个试点开展橄榄“粤榄18”品系适应性试验,结果如下：利用8～9年生橄榄改接第4年及1年生砧木嫁接后第9年, 其平均单株产果量达22.9kg,单株平均增产15.1kg,产量增益216.82%;平均单位树冠投影面积产果量达0.77kg/m2,平均增产200.01%;试点间单株产果量和单位树冠投影面积产果量的变异系数（CV）分别接近或小于试点内的CV;平均冠幅生长量改接株接近不改接的植株,但1年生砧木嫁接株的比对照大18.75%。“粤榄18”嫁接亲和性较好,生长较快,丰产性好,立地适应性强,是一个值得在生产上大力推广的优良品系。     

Nelder试验:大叶相思树冠生长、多干特征与密度的关系

运用Ｎｅｌｄｅｒ密度试验设计方法,研究了大叶相思林分的树冠生长以及多干现象与密度的关系。结果表明：１年生时各种密度林分均未郁闭,３年生、５年生、７年生时郁闭林分的单株面积上限分别为３．１５ ｍ ２·株－ １、６．２０ ｍ ２·株－ １、７．００ ｍ ２·株－ １。５年生以后,树冠趋于稳定,１～３年生时树冠生长最大的单株面积为５．６４～６．８８ ｍ ２·株－ １,５～７年生时树冠最大的单株面积为１５．５０～１８．６８ ｍ ２·株－ １。林分平均树干数与密度则呈现幂函数关系,林分单株面积小于１ ｍ ２·株－ １时,多干木比例在１０％ 以下;林分密度超过１２．５３ ｍ ２·株－ １以后,多干木比例为１００％ 。     

国外松母树林疏伐的探讨

我省营建国外松母树林从1974年开始,我场天洋工区国外松母树林自1974年建立,现保存面积530亩,其中湿地松413.5亩,火炬松116.5亩.根据我场母树林情况,第1次疏伐强度为25%(每亩保留68—80株)第2次疏伐强度为35—40%.疏伐使树冠之间保留一定距离,以树冠枝桠不重叠为宜,尽量使树冠扩大.增加结果面,有利于增加单株产量和单位面积产量,每亩最后保留母树12—15株.     

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.     

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.