广州市不同绿地冬季温湿度差异性研究

热岛效应是城市化进程中不可忽视的一个环境问题,而城市绿地能够有效地缓解此效应。文章研究了绿化天桥、屋顶、住宅小区、道路、森林、公园等6种绿地类型的温湿度特征,分析了6种绿地类型对城市微气候的影响。分析表明,绿化天桥和屋顶的温度显著高于绿化小区、道路、森林和公园,而相对湿度则显著低于其他绿化类型的;森林的温度显著低于其他绿化类型的,森林的相对湿度则显著高于其他绿化类型的。除公园外,其他绿地类型的全日温差都较小。     

北京市3种园林绿地土壤碳排放浓度比较

对北京不同植被类型的园林绿地土壤CO2排放浓度和通量进行比较,通过利用AV-SFS土壤呼吸分析仪测量,于2010年9~12月测定并分析了北京朝阳区四环附近3种典型植被类型的土壤CO2排放日变化状况。结果显示,不同植被类型的土壤CO2排放变化都表现为单峰曲线;裸地和林下园地的土壤CO2排放单日日变化幅度都比草坪地的值低;两者日排放浓度最高值高于草坪地,最低值低于草坪地。不同植被类型土壤CO2排放通量的分析结果表明,研究地在实验状态下,草坪地的土壤碳通量日变化最高,平均值为-437.1g·m-2·s-1;裸地土壤碳通量日变化最低,且与林下园地两者之间的差异较小。     

不同城建绿地内PM2.5浓度季节变化及其与气象因子的关系

以杭州市临安区4种不同类型的城建绿地(居住区绿地、商业绿地、公共服务设施绿地和广场绿地)为研究对象,在2017年3月-2018年2月,采用实地测量法对绿地内的PM2.5浓度及气象因子(温度、相对湿度和风速)进行监测,研究城建绿地内PM2.5浓度的时空变化规律及其与气象因子的关系。结果表明,不同绿地的PM2.5浓度季节变化均表现为冬季>秋季>春季>夏季;春、夏和冬3个季节的PM2.5浓度依次为商业绿地>居住区绿地>公共服务设施绿地>广场绿地,秋季为商业绿地>居住区绿地>广场绿地>公共服务设施绿地;绿地内PM2.5浓度日变化受人为活动和交通排放影响较大,在下班高峰时段(17:00-20:00)表现尤为明显;气象因子对PM2.5浓度变化有重要影响,绿地内的PM2.5浓度与温度呈极显著负相关(P<0.01)、与相对湿度呈显著正相关(P<0.05)、与风速显著相关(P<0.05)。     

喀斯特多山城市植物群落物种多样性空间分异特征——以安顺市为例

为探析喀斯特山地城市生物多样性特征及其影响因素,以黔中典型多山城市——安顺市为研究对象,运用生物多样性相关理论与方法,分析了安顺市植物物种多样性特征及其影响因素。结果表明:(1)安顺市植物群落物种多样性指数偏低,不同空间区域中差异较大,西南片区和中心区域低而东北片区最高;(2)不同绿地类型中植物群落物种多样性指数由高到低的顺序为区域绿地、公园绿地、附属绿地、防护绿地、广场绿地;(3)在不同方位中较为发达的中心城区与西南方位上多样性较低,东北方位最高;(4)自然绿地的植物群落物种多样性高于人工绿地和半人工、半自然绿地;(5)海拔1400 m以上区域的多样性高于海拔1400 m以下的区域。城市内植物群落物种多样性受地形地貌和城市发展的影响表现出较大的差异性,通过采取相应措施来调节人类活动与自然环境之间的关系,合理构建生态廊道,加强不同类型生境间的内在联系,让城市内的生态得到更好的保护与发展。     

小五台山自然保护区气候特征初步分析

利用小五台山自然保护区山涧口沟山神庙滩自动气象站3a的观测资料,分析了该地区温度、湿度、雨量、大气压强和辐射等气象要素的季节变化特征。结果表明:该区具有气温日较差和年较差较大的气候特点,年均气温为7.87℃,气温季节变化中降温率高于升温率;年降水总量高,达728.48mm;平均相对湿度季节变化过程分布与年变化基本与气温的季节变化一致,与降水量分布一致;大气压强变化分布主要受季节变化过程影响,与相对湿度呈现反向关系;月均总辐射强度夏季明显高于冬季,5月出现最大值,与大气所含水汽、天空云量、下垫面性质等因素有关。     

“述古”与“言今”——谈城市园林绿地的人文化

园林绿地对城市生态平衡和可持续发展起着巨大作用，越来越成为城市发展过程中不可或缺的一种补偿。同时，人们也逐渐认识到城市园林绿地中人文内涵的重要意义，城市园林设计不能仅局限于某些特定的物质元素（如广场、林荫道、栽植等）的运用，而应提供一种可以供人体验和感知的文化氛围，创造隐含在物质形体环境中的风格特色。     

西宁市城市典型绿地空气负氧离子浓度特征研究

为了解西宁市城市森林不同功能区的空气负氧离子浓度及其与环境质量的关系,笔者选择了西宁市5个典型绿地进行了全天和全年空气负氧离子浓度及环境条件的测定。结果表明:1)5个城市典型绿地空气负氧离子浓度有显著差异(F=66.47,Sig0.05),平均值为400.1个/cm3.其中,植物园、省委家属院和麒麟湾高出世界卫生组织(WHO)规定的清新空气负氧离子最低浓度需达到250个/cm3的标准;海湖大道和新宁广场的空气负氧离子浓度低于标准。2)植物园、麒麟湾和省委家属院的空气负氧离子浓度日变化呈双峰曲线,9:00和17:00为峰顶,7:00,15:00和19:00为峰谷,其中9:00为最高峰段。海湖大道和新宁广场空气负氧离子浓度日变化平缓。3)植物园、麒麟湾和省委家属院空气负氧离子浓度的年变化呈单峰曲线,高峰出现在7月至9月份。新宁广场年变化平缓,海湖大道年变化复杂。4)5个绿地的空气负氧离子浓度与绿地类型、温度和相对湿度呈正相关,与风速、PM2.5和PM10.0呈负相关。空气负氧离子浓度与环境因素间的曲线拟合以一次方程的拟合优度最好。     

城市绿地空间结构对空气负离子的影响与评价

城市绿地是空气负离子浓度变化的重要调节器,并为人类活动和游憩提供重要场所。选择广州市从化区具有代表性、空间结构异质性的城市绿地作为研究对象,在冬夏2个季节对6种绿地类型的空气负离子水平进行连续监测。结果表明：不同植被类型绿地空气负离子浓度差异显著,结构复杂、物种丰富的复层绿地高于结构简单、物种少的绿地;夏季和冬季不同地区负离子浓度最高的两个地区均为别墅区和公共服务区,最低的2个地区为小区道路和广场绿地;空气清洁度指标总体较好,夏季除小区道路（B级）和广场绿地（D级）外,其他地区均为A级,冬季广场绿地质量有所改善为B级,而其他均为A级。     

林网绿地抗污染功能探析

林网绿地在城市抗污染中的功能是多方面的,概括起来讲,主要体现在调节小气候,改善环境质量和美化景观方面。调节小气候小气候主要是指从地面到10余m至100m高度空间内的气候,这一层正是人类生活和植物生长的区域和空间。人类的生产和生活活动、植物的生长和发育都深刻影响着小气候。植物叶面的蒸腾作用能调节气温、调节湿度、吸收太阳辐射热,对改善城市小气候具有积极的作用。研究资料表明,当夏季城市气温为27.5℃时,草坪表面温度为20℃～24.5℃,比裸露地面低3℃～7℃,比柏油路面低8℃～20.5℃,而在冬季,铺有草坪的足球场表面温度则比裸露的球场表面温度提高4℃左右。绿色植物具有强大的蒸腾作用,不断向空气中输送水蒸气,可提高空气湿度。据观测,绿地的相对湿度比非绿化区高10%～20%,行道树也能提高相对湿度10%～20%。城市的林网绿地,如道路绿化与公园绿地是城市的绿色通风走廊,可以将城市郊区的自然气流引入城市内部,为炎夏城市的通风创造良好条件;而在冬季,则可减低风速,发挥防风作用。改善环境质量吸收二氧化碳,放出氧气,维持碳氧平衡。有关资料表明,每ha绿地每天能吸收900kgCO2,生产600kgO2,每ha阔叶林在生长季节...     

贵阳市常见园林绿化植物琴丝竹滞尘能力研究

以贵阳市常见园林绿化竹种琴丝竹为研究对象,应用空气气溶胶再发生器(QRJZFSQ-I)分季节测定了不同污染程度的4个地点(城市广场绿地、城市公园绿地、城郊绿地、城郊林区)的琴丝竹叶片对TSP、PM_(10)、PM_(2.5)、PM_1的吸附量,用扫描电镜观察比较了叶片上、下表面微形态,分析不同污染背景的琴丝竹叶片滞尘能力及其季节变化、叶表面微形态与滞尘量的关系。结果表明:不同污染背景下生长的琴丝竹叶片滞尘能力差异明显,依次表现为城市公园绿地城市广场绿地城郊林区城郊绿地;城区郊区。叶片对不同类别颗粒物的滞留能力也存在差异,4种粒径颗粒物的滞留量均表现出城市公园绿地和城郊绿地差异显著,PM_(2.5)和PM_1的滞留量在城市公园绿地与城郊林区也表现出显著差异;琴丝竹叶片滞留不同粒径空气颗粒物的季节变化在不同地点呈现不同的变化趋势:城郊(林区、绿地)季节变化趋势无明显规律,城区(公园绿地和广场绿地)则在冬季最高,春季或夏季最低;琴丝竹叶表面结构粗糙皱褶多,叶片分布条状突起,有深沟槽,被细柔毛,属于滞尘能力较强的树种,可广泛用于园林绿化。     

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.