苏州地区10种常见园林树木光合特性研究

用LI-6400光合系统分析仪,测定10种苏州常见园林配置树木(香樟、玉兰、无患子、紫薇、桂花、紫荆、枫香树、杜鹃、海桐、红花檵木)的光合特性及固碳释氧能力。结果表明:10种树木夏季晴天均有明显的光合速率日变化。枫香树、无患子光合速率表现为单峰曲线,8:00其净光合速率就达到当天的最大值;其他8种植物净光合速率的日变化表现为双峰曲线的。10种植物中乔木的单位叶面积日固碳释氧量大小排序为香樟、玉兰、桂花、无患子、枫香树;灌木的单位叶面积日固碳释氧量大小排序为紫薇、紫荆、海桐、红花檵木、杜鹃。     

杭州市主城区道路绿化树种组成与VOCs成分分析

为分析杭州市主城区道路绿化树种叶表面区域的VOCs成分、研究VOCs与城市道路绿化的关系,文章对该地区道路绿化资源进行调查,并采用气相色谱质谱联用仪(GC/MS)对主要绿化树种叶表面区域的VOCs进行测定,结果显示,杭州主城区的主要乔木为香樟、悬铃木、朴树、无患子、栾树、枫杨、雪松、玉兰、银杏,主要灌木为红叶石楠、金森女贞、红花檵木、月季、无刺枸骨、紫薇、紫叶李、桂花、金边黄杨;在这些树种叶表面区域检测到的VOCs可分为卤烃类、芳烃类、醛类、烷烃类、酮类、酯类、烯烃类和其他类;在现有的主要树种中,挥发物质相对较少的是香樟、悬铃木、朴树、金森女贞、红花檵木、无刺枸骨、桂花,挥发物质相对较多的则是雪松、枫杨、紫叶李、金边黄杨等,研究结果对城市道路绿化植物的筛选具有重要指导意义。     

公路绿化主要树种滞尘潜力模拟试验研究

利用绿化植物滞尘已成为缓解大气颗粒污染的最有效途径,选择具有代表性的常见公路绿化树种,通过对其叶片滞尘潜力的探讨研究,以期筛选出滞尘能力强的植物,为公路交通环境的改善提供理论依据。结果表明,不同植物的滞尘潜力差异显著,阔叶乔木中二球悬铃木、杨树、国槐叶片的滞尘潜力最大,分别为6.495 9 g/m2,5.736 8 g/m2,4.791 9 g/m2;常绿乔木中,侧柏是较好的滞尘树种,最大滞尘量为7.568 8 g/m2;灌木植物以忍冬叶片的滞尘能力最强,其次为紫丁香及卫矛,最大滞尘量分别为7.084 7 g/m2,6.062 5 g/m2,5.878 9 g/m2.     

武汉城区道路绿化园林植物群落特征

采用典型样方法调查分析了武汉城区道路绿化植物群落特征,结果表明：植物群落结构以乔灌型为主,约占70％;群落的植被类型主要为常绿落叶阔叶混交林,占76.67％;出现频率最高的乔木是桂花,其次依次为樟树、白玉兰和广玉兰;灌木层中红枫、石楠、海桐和红叶李的频度位居前4位,草本层中鸢尾的频度最高.就植物多样性而言,群落的植物多样性水平总体不高,且乔木层的均匀度、丰富度、优势度和多样性均高于灌木层.     

长沙市行道树绿带植物组成及其健康状况调查

对长沙市23条主次干道行道树绿带的植物组成及其健康状况进行调查,结果表明:(1)长沙市行道树绿带常用植物种类约有96种,其中约占总数29%的为高大乔木,且常绿树种的应用比例约为4/5;出现频率超过45%的树种有7种,即香樟、广玉兰、桂花、金叶女贞、红檵木、四季桂等,但香樟、广玉兰、桂花、悬铃木等树种的均匀度相对较低;(2)长沙市行道树绿带中应用的灌木有40余种,山茶、栀子、杜鹃、月季、紫薇等观花灌木较多,特别是山茶所占的比例最大,占所调查全部灌木植物总数的22.5%;(3)长沙市行道树的胸径径级结构分布比较合理,但树高等级上的分布相对不合理,且长沙市行道树绿带中的植物的健康水平总体上属于中等偏上;(4)在长沙市行道树绿带中观花植物种类有20种,观果植物8种,观叶植物11种,观形植物11种,且长沙市城市道路绿化的主色调为绿色,常绿树种和落叶树种之比为4∶1。     

保定市几种常见绿化树种叶片滞尘能力研究

为了揭示保定市常见绿化树种的滞尘规律,选择校园和交通干道2个功能区的9种绿化树木进行叶片滞尘能力的研究,结果表明:不同树种的滞尘能力差异极显著,法桐、构树、大叶黄杨滞尘能力较高,12d的滞尘量分别为10.071 1g/m2、8.820 2g/m2、7.653 5g/m2,碧桃、紫荆、紫丁香滞尘能力居中;楸树、紫叶李、加杨的滞尘能力较低,加杨的滞尘量最小,仅为1.053 4g/m2;不同研究区植物滞尘能力也存在显著差异,南二环树木的滞尘量远高于校园内树木的滞尘量,法桐、大叶黄杨在南二环的滞尘量分别是校园的7.9倍和6.7倍,紫叶李在南二环滞尘量甚至是校园的14.9倍;比较不同树种在4d、7d、12d内的日均滞尘量发现,随着时间的推移,植物滞尘能力越来越小。总之,可以优先考虑选择法桐、构树、大叶黄杨作为保定市的绿化树种。     

郑州市常见园林植物净碳汇及其经济价值

为了研究郑州市不同种类园林植物的净碳汇及其经济价值,选择了具有代表性的13种乔木树种,8种灌木树种,5种草本植物,调查计算了这些植物的碳投入量,测定了这些植物的净生产力和碳含量,计算其净碳汇,用碳税法计算不同植物种类固碳价值。结果表明,乔木树种净碳汇的价值由大到小的顺序为:法桐、银杏、国槐、雪松、旱柳、女贞、广玉兰、黄山栾、白蜡、垂柳、龙柏、侧柏、紫叶李;灌木树种净碳汇的价值由大到小的顺序为:红叶石楠、小叶女贞、法青、黄杨、千头柏、月季、紫叶小檗、紫薇;草本植物净碳汇的价值由大到小的顺序为:菊花、鸢尾、葱兰、麦冬、早熟禾;不同类型园林植物的净碳汇的价值,乔木树种最大,其后依次为灌木树种、草本植物。建议在园林绿化中选择净碳汇较高的园林植物,减少园林绿地管理中农药与肥料的使用量,降低其碳投入,不断提高园林绿地空气净化功能。     

5个园林树种滞尘能力与叶表形态及颗粒物粒径的关系

[目的 ]研究园林树种叶片滞尘能力与叶表结构及颗粒物特征的关系,为筛选优良园林绿化树种、提高植被的滞尘效应提供科学依据。[方法 ]以杭州市富阳区5个常见园林绿化树种(红花檵木、海桐、红叶石楠、桂花和香樟)为研究对象,分别在工业区、交通区和清洁区进行采样,采用质量差值法测定植物对不同粒径颗粒物的滞留能力,利用扫描电镜及能谱仪观测植物叶表面结构、颗粒物形貌特征及所含元素,分析叶片表面结构、颗粒物形态、粒径大小与植株滞尘能力的相互关系。[结果 ]在工业区中绿化树种对总颗粒物的滞留量大小为:红花檵木(7.36 g·m-2)桂花(6.53 g·m-2)海桐(6.44 g·m-2)红叶石楠(4.28 g·m-2)香樟(2.59 g·m-2),交通区和清洁区也呈现同样的规律。不同功能区绿化树种对PM10的总滞留量达11.34 g·m-2,不同树种的滞留能力依次为红花檵木、海桐、红叶石楠、桂花和香樟。不同功能区内绿化树种对颗粒物的滞留量呈现工业区交通区清洁区的趋势;植物叶片滞留的颗粒物形态可分为规则和不规则两类,常见球形、椭圆形、蓬松状聚合体、链状聚合体、不规则块状、不规则片状等。[结论 ]各功能区内,均以红花檵木的滞尘量最大,香樟的滞尘量最小;叶片滞留颗粒物中粗颗粒物占比大于细颗粒物;叶片滞留的颗粒物多为烟尘集合体和矿物颗粒。     

乌鲁木齐市绿化植物的固碳释氧及蒸腾耗水率比较

以乌鲁木齐市苹果、大叶榆、白榆、大叶白蜡、小叶白蜡等5种乔木和紫丁香、榆叶梅、紫穗槐等3种灌木绿化植物为研究对象,测定其叶片比叶重、叶片光合速率,计算出植物叶片固氮释氧量,监测其植物茎流,评估其蒸腾耗水速率。结果表明:白榆和榆叶梅的固碳释氧能力最强,其次依次为大叶白蜡紫穗槐小叶白蜡苹果大叶榆,最差为紫丁香。根据日均蒸腾耗水速率的大小将8种乔灌木植物分为4个级别:第一级别为蒸腾耗水速率极大的树种,包括大叶白蜡、大叶榆和紫丁香;第二级别为蒸腾耗水速率较大的树种,包括苹果和榆叶梅;第三级别为蒸腾耗水速率较小的树种,包括小叶白蜡和白榆;第四级别为蒸腾耗水速率极小的树种,包括紫穗槐。     

城市常见植被固碳与VOC排放的相关性及其应用潜力

以温州市区为研究区域,采用野外样方调查和实验室模拟相结合方法,研究常见绿化树种固碳能力和VOC的排放量及两者的相关性。结果表明:从单位土地面积日均固碳能力和VOC排放量上来看,灌木的VOC排放量相对较低且固碳能力较强。从整株水平上,固碳能力较好的树种VOC排放量也相对较高。植物固碳能力和VOC排放量具有种特异性,单位土地面积水平上固碳量高且VOC排放量较小的树种有:山茶、石楠、海桐、十大功劳、红花檵木、蚊母树、夹竹桃、白兰花、桂花和香叶树,可以作为城市绿化的推荐树种。     

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.