太行山苹果生态经济型水土保持林空气负离子特征研究

利用空气负离子测定仪(TC-201A型)对太行山苹果生态经济型水土保持林的空气负离子浓度进行了测定,以期为本地区生态旅游空气质量评价提供依据。结果显示:空气负离子浓度早晨6:00-8:00时较高,平均为803个/cm3;中午12:00-14:00时降至低谷,平均为576个/cm3;下午又逐渐升高,到16:00-18:00达到851个/cm3;基本呈现出先降低再升高的日变化规律。2010年6月到10月份,5个月逐月的空气负离子平均浓度分别为928个/cm3、826个/cm3、433个/cm3、757个/cm3和396个/cm3,基本呈现逐月降低的趋势(9月份除外)。林分内空气负离子浓度垂直变化的规律为,在0.5m时达到最高520个/cm3,3.5m时达到最低301个/cm3,随着高度的增加空气负离子浓度逐渐降低;坡上林分的空气负离子浓度大于沟内,但二者差异不显著;不同林龄苹果林内的空气负离子浓度表现为林龄28a(592个/cm3)14a(463个/cm3)10a(384个/cm3);空气负离子浓度与温度呈负相关关系,与相对湿度呈正相关关系。     

神农谷国家森林公园空气负离子水平研究

采用FTP-2型大气离子测量仪对神农谷国家森林公园内的空气正、负离子进行了测量,并用统计工具对数据进行了处理分析.结果表明:(1)神农谷国家森林公园内珠帘瀑布空气负离子浓度年平均为4 555个/cm3,大于牛角垄的2 379个/cm3; (2)森林环境中水体对空气负离子水平的影响较大; (3)森林中空气负离子浓度还呈现出一定的日、月和季节变化规律.     

三叠井森林公园空气负离子的时空分布特征

对三叠井森林公园内10个具有代表性的景点7:00-18:00的空气正、负离子浓度、温度、相对湿度进行测定与分析,并以单极系数和空气离子评价指数为标准对其空气质量进行评价.结果表明:三叠井森林公园空气负离子浓度在7:00-18∶00时变化特征呈现出两头高、中间低的“V”字形形态;空气负离子浓度与温度呈线性负相关关系,而与空气湿度呈线性正相关关系;空气负离子浓度的空间分布特征为:鸳鸯瀑布＞坪溪＞奇树湾＞古槠亭＞竹柏林＞鳄鱼潭＞天籁谷＞状元帽＞熊面壁＞观景台;所有观测点的空气质量均达到了A级.     

湖南省森林植物园空气负离子浓度变化

于2011年9月至2012年8月应用FTP-2空气负离子测量仪对湖南省森林植物园3个生态区及全园的空气正、负离子浓度进行测量,并采用日本的空气质量评价指数(I C)对其空气质量作了评价。结果表明:(1)湖南省森林植物园空气负离子浓度垂直变化明显,园中高于园内其他地方。空气离子评价系数(I C)均大于0.93,属于清洁,空气质量很好。(2)从空旷地向水区空气负离子浓度和空气质量(I C)逐渐增加,有林地区空气负离子浓度明显高于无林地区;有瀑布和水流等动态水地区空气负离子浓度明显增加;园中不同功能区空气负离子浓度和空气质量差异显著,其大小依次为水边>林内>空旷地;(3)空气负离子浓度和空气质量的日变化规律曲线为双峰形,总的规律为上午高,下午低,一天中存在2个峰值,分别为上午7:00点(563.75个/cm3)和8:00点(789.67个/cm3),I C值为1.11和1.40,大于1,为清洁或最清洁。其它时间处于平稳趋势;(4)空气负离子浓度和空气质量的季节变化规律曲线为多峰形,1月最低,为256.20个/cm3,I C值为0.36;7月最高,为542.86个/cm3,I C值为1.06。总趋势为夏、秋季高,春季适中,冬季最低。     

龙岩国家森林公园云顶茶园空气负离子浓度的测定与评价

在介绍空气负离子产生、作用及评价方法的基础上,对龙岩国家森林公园云顶茶园空气负离子浓度进行测定、评价,结果表明,云顶茶园景区各景点空气负离子浓度平均值为60.7万个.cm-3,正离子浓度达到68.7万个.cm-3,CI值平均为539.1,q值平均为1.132;各景区空气负离子平均浓度是龙岩市区空气负离子浓度的100多倍。     

天宝岩国家级自然保护区生态旅游区域空气负离子特征研究

以天宝岩国家级自然保护区生态旅游区域为研究对象,测定空气离子浓度、海拔、温度、湿度等指标,计算空气质量指数,并进行分析评价。结果表明:保护区生态旅游区域10个监测点的负离子浓度值均高于1 000个/cm3,并在上午10∶00和下午16∶00左右出现峰值,中午时段为低谷;空气质量指数(CI)为11.301~51.863,单极系数(q)为0.045~0.336,达到评价A级标准(最清洁);评价区内的空气质量远高于市区内;空气负离子浓度随温度的升高而下降,随湿度的升高而升高。在此开展生态旅游活动对缓解久居城市人群的身心压力、改善健康水平具有积极作用,旅游开发价值较大。     

广州下半年负离子分布的时空特征

为研究广州市下半年空气负离子分布的时空特征,利用空气离子测量仪,在广州市选择典型的采集地,分析了空气负离子的月际变化、功能区类型、取样时段、典型环境对空气负离子浓度的影响。结果表明：（1）所测定的几种功能区空气负离子浓度大小顺序为：华南农业大学跃进南宿舍区〉广州市白云山〉华南农业大学树木园〉广州市天河区五山路;（2）月际变化：9月到11月负离子没有明显的变化,而12月负离子含量明显的减少;（3）负离子浓度最大值出现在晚上19：00～20：00,一天之内的负离子浓度变化呈早、晚较高,中午低的规律;（4）对广州几种典型环境进行测定,负离子浓度大小顺序为：近水区（林中（游憩区（道路;（5）广州市下半年负离子浓度最大值高达58 000个/cm^3,而最小值仅为1 000个/cm^3。     

北京市植物园空气负离子浓度测定及空气质量初步评价

用DLY-3G型空气离子测定仪对北京植物园热带温室、湖区和樱桃沟春、夏、秋、冬四个季节空气离子浓度进行测定,并以单极系数和安倍空气离子评价指数为标准对其空气质量进行评价。结果表明,北京市植物园的负离子浓度呈现季节变化,以夏季最高,平均为4097个/cm3;冬季最低,平均为867个/cm3;其次是秋季和春季,分别平均为2833个/cm3和2400个/cm3。年均负氧离子浓度2549个/cm3,约为市区年均负离子浓度的6倍。三个景点相比,空气负离子浓度以热带温室最高,其次是湖区,以樱桃沟最低。以单极系数和安倍空气离子评价指数为标准对其空气质量进行评价得出结论:空气质量春、夏、秋都属于最清洁,冬季空气质量稍差,但也处于清洁水平;三个景点相比,以热带温室空气质量最好,四季都属于最清洁。     

合肥大蜀山国家森林公园主要植物群落空气清洁度评价研究

以合肥市大蜀山森林公园3种典型植物群落的负离子时空分布为研究对象,利用空气离子评议系数(CI)对该区域春季的空气清洁度进行评价。结果表明,雪松群落白天的平均空气负离子浓度为1 100个/cm3,杨树群落为1 831个/cm3,竹林群落为1 498个/cm3。植物新叶量的多少是影响植物群落负离子产生能力的关键因素,杨树林在4月份新叶量最多,生理活性最旺盛,空气负离子产生能力最强;其次是竹林,雪松林最弱。根据空气评价系数,3种群落空气清洁度顺序为杨树林 > 竹林 > 雪松林。     

湖南两江峡谷国家森林公园区域环境质量监测与评价

经过取样对湖南两江峡谷国家森林公园大气、地表水、土壤质量、空气负离子含量和空气细菌含量等因子监测得知,该区域环境空气质量为一级;地表水达到I类水质标准;公园内土壤有机质含量丰富,无放射性污染物质;14个监测点空气负离子平均在11997个/cm3,空气清新;公园内3个取样点的细菌数147~445个/m3之间,离超标限（3700个/m3）距离都很远,卫生条件极好。森林公园总体环境质量优良,是人们休闲、度假、开展生态旅游的极佳场所。     

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.