气象因子对山杏结实率影响研究

研究了温度、光照、空气湿度和风速对山杏结实的影响。结果表明:温度、光照、相对湿度及风速影响山杏结实率,各坡向坐果率差异较大,东北坡东坡下腹北坡东坡上腹南坡。东北坡坐果率最高,比坐果率最低的南坡高出了21.79个百分点,同一坡向的东坡下腹比东坡上腹亦高出了13.27个百分点。     

海南霸王岭坡垒分布格局初步研究

通过实地调查,对坡垒随地形因子(海拔、坡向、坡度)的分布规律进行了分析。结果表明,坡垒分布主要集中在中低海拔600~900 m,先随海拔增高而增加,海拔700~800m时候达到最高值,随后随海拔升高而减少;不同坡向对坡垒数量分布影响为:北坡西南坡东北坡南坡西北坡西坡东南坡东坡,阴坡上分布的坡垒数显著高于阳坡上的分布数量;坡垒集中分布在坡度20~25°范围内。可见坡垒的分布格局与海拔、坡向及坡度密切相关。     

利用粘虫板诱捕落叶松红腹叶蜂成虫效果初探

在宁夏六盘山国家级自然保护区利用绿色、黄绿色、土黄色、红色等不同颜色粘虫板,研究了羽化期内不同颜色粘虫板诱捕落叶松红腹叶峰成虫效果,结果为,4种颜色粘虫板中绿色效果最好,黄绿色、土黄色次之,红色最差;8个坡向南坡效果最好,西南坡、东南坡次之,东坡、西坡再次之,西北坡、东北坡、北坡较差;5月8-21日为诱捕最佳时段。利用粘虫板防治落叶松红腹叶蜂成虫应以5月8-21日将绿色粘虫板布置于南坡为佳。     

利用粘虫板诱捕落叶松红腹叶蜂成虫效果初探

在宁夏六盘山国家级自然保护区利用绿色、黄绿色、土黄色、红色等不同颜色粘虫板,研究了羽化期内不同颜色粘虫板诱捕落叶松红腹叶峰成虫效果,结果为,4种颜色粘虫板中绿色效果最好,黄绿色、土黄色次之,红色最差;8个坡向南坡效果最好,西南坡、东南坡次之,东坡、西坡再次之,西北坡、东北坡、北坡较差;5月8—21日为诱捕最佳时段,利用粘虫板防治落叶松红腹叶蜂成虫应以5月8—21日将绿色粘虫板布置于南坡为佳。     

半枫荷早期生长与林地不同坡向关系的探讨

通过对试验地5年生半枫荷8种坡向的幼树生长量调查,经方差分析,并进行了新复极差测验,结果表明:半枫荷北坡的平均树高为4.6m,极显著高于西北坡的3.40m、西坡的3.395m、东南坡的3.39m、西南坡的3.32 m和南坡的3.28 m;北坡的平均胸径为6.04cm,极显著大于东南坡的4.49cm、南坡的4.40cm、西南坡的4.48cm;北坡的平均保存率率为93.23%,极显著高于西坡的88.6%、东南坡的88.55%、西南坡的86.68%、南坡的86.45%,东北坡的平均保存率为92.28%、东坡的平均保存率为92.25%,极显著高于西南坡的86.68%和南坡的86.45%。经分析对比,半枫荷8种坡向造林其北坡的胸径和树高生长量最大,保存率也最高。     

坡向、坡位对泡桐人工林土壤养分空间分布的影响

为选择适宜泡桐生长的坡向坡位,对湖北省咸宁市浅山丘陵区不同坡向和坡位的土壤养分空间分布差异进行了测定、比较和分析。结果表明:1坡位对有机质含量、全氮含量、有效钾含量和有效磷含量空间分布的影响均达显著及以上程度,坡向和坡向与坡位的交互作用对土壤有效P、有效K空间分布的影响多达极显著程度。2对4项养分指标在0~40 cm土层范围内的标准化数据进行聚类分析,可将12个坡向坡位划分为3类,其中第1类为东坡下部、南坡下部、西坡下部、北坡下部;第2类为北坡上部、北坡中部、东坡上部、东坡中部;第3类为南坡上部、西坡上部、南坡中部、西坡中部。3在此3类坡向坡位中,第1类与第2类相比较,土壤有机质含量高29.02%,全氮含量高28.77%,有效磷含量高257.37%,有效钾含量高23.69%,可视为最适宜的坡向坡位;第2类与第3类相比,有机质含量高7.84%,全氮含量高11.30%,有效磷含量低76.56%,有效钾含量低5.59%,整体较第1类坡向坡位差。     

基于机载高光谱的思茅松林光谱特征及其影响因子分析

[目的]以云南普洱菜阳河为例,基于机载遥感影像,探讨思茅松林冠层高光谱特征及坡向对其光谱反射率的影响。[方法]以2014年4月机载Li CHy系统获取的高光谱和激光雷达DEM提取的坡向数据,结合该地区二类调查数据,对不同坡向的思茅松林冠层光谱曲线特征值进行统计比较。[结果](1)思茅松冠层光谱反射特征与绿色植物光谱曲线总体相似,在0.74~1.0μm近红外波段冠层反射率较高,0.89μm最高;(2)阴坡思茅松冠层光谱反射率普遍高于阳坡,北坡、东北坡与南坡、东南坡的峰值波段反射率在0.05水平上差异显著;(3)根据太阳高度角,迎光面的东坡、东北坡、东南坡比背光面西坡、西北坡、西南坡光谱反射率在0.89μm波段增加了14%~23%。[结论](1)思茅松冠层光谱反射率表现出"两谷一峰"、"红边"等典型的植被光谱特征,反射率较高的0.74~1.0μm波段为思茅松的特征光谱段;(2)太阳高度角是影响不同坡向光谱反射率的主要因素,而坡向也是造成反射率差异的另一个重要原因。     

红松幼龄人工林套植辽东楤木的经营技术

在辽东山区经过4a的试验研究,开展了红松幼龄人工林套植辽东楤木经营技术的不同坡向和不同栽植密度的对比试验,旨在加快辽东楤木经济林建设,延伸了林业产业化的内涵,产生新的林业经济增长方式。结果表明,苗高和地径生长量大小顺序为东北坡>西北坡>北坡>西南坡>南坡,保存率大小顺序为东北坡(95.2%)>北坡(93.7%)>西北坡(89.5%)>南坡(83.3%)>西南坡(80.4%),嫩芽产量与栽植密度呈正相关关系。     

坡向与造林密度对刨花润楠幼林生长的影响

在福建省华安葛山国有林场,通过对不同坡向和2种造林密度的10年生刨花润楠林分生长量调查分析,结果表明:不同坡向对刨花润楠树高和胸径生长有显著影响,以东北坡的刨花润楠生长量最大,胸径达到8.1 cm,树高9.1 m;其次为西坡、北坡、南坡;东坡最小。种植密度对刨花润楠生长有显著影响,适当的提高造林密度能够促进刨花润楠的生长。     

坡向和坡度对土壤动物群落结构影响研究——以上海辰山植物园结缕草草坪为例

为了解不同坡向和坡度对土壤动物群落结构的影响,于2016年夏季在上海辰山植物园东南西北四个坡向以及7度和22度两类坡度结缕草草坪的坡上、坡中、坡底三个坡位进行了采样,对其中的土壤动物群落进行了调查。结果表明:土壤动物个体数为南坡(30.11%)西坡(26.96%)北坡(21.65%)东坡(21.28%)。不同坡向土壤动物群落多样性指数差异不显著。坡顶各多样性指数相对坡中和坡底较小,坡中和坡底差别不大。7度坡底显著低于坡顶,22度坡个体数为坡顶坡底坡中,均存在显著性差异。坡向对土壤动物群落结构的影响为间接影响,较大坡度对土壤动物群落的影响更明显。     

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.