Mapping the spatial distribution of shade provision of street trees in Boston using Google Street View panoramas

Street trees provide shade and increase human thermal comfort during hot summer. In this study, we investigated the spatial distribution of shade provision of street trees in Boston, Massachusetts. The sky view factor (SVF), which influences the solar radiation to the ground and affects human thermal comfort, was used to indicate the contribution of street trees on shade provision. Google Street View (GSV) panoramas were used to calculate the photographic method based SVF (SVF_P), with the consideration of all kinds of obstructions within street canyons. A building height model was used to calculate the simulation based SVF (SVFs), with consideration of obstruction of building blocks only. Considering the fact that street trees and building blocks are the two major obstructions of radiation within street canyons, therefore, the difference between the two SVF estimation results can be considered as the shade provision of street trees. The results show that street trees help to decrease the SVF by 24.61% in Boston, Massachusetts. The shading level varies spatially in the study area. Generally, the southwestern area has much higher shading level than the north and the east. We further explored the shading variation among different socioeconomic groups in the study area. Result shows that Hispanics tend to live in neighborhoods with lower shading level. This study can help to provide a reference for future urban greening projects for global climate change adaption.     

Effect of phytoplasmal infection on photosystem II efficiency and thylakoid membrane protein changes in field grown apple (Malus pumila) leaves

We have studied the effect of the apple proliferation phytoplasmal infection on some features of the thylakoids from field grown apple (Malus pumila) leaves. Changes in photosynthetic pigments, soluble proteins, ribulose-1,5-bisphosphate carboxylase, nitrate reductase, photosynthetic activities and thylakoid membrane proteins were investigated. The level of total chlorophyll and carotenoids were reduced in phytoplasma-infected leaves. Similar results were also observed for soluble proteins and ribulose- 1,5-bisphosphate carboxylase activity. The in vivo nitrate reductase activity was significantly reduced in infected leaves. When various photosynthetic activities were followed in isolated thylakoids, phytoplasmal infection caused marked inhibition of whole chain and photosystem II activity while the inhibition of photosystem I activity was only marginal. The artificial exogenous electron donors, diphenyl carbazide and hydroxylamine significantly restored the loss of photosystem II activity in infected leaves. The same results were obtained when F_v/F_m was evaluated by chlorophyll fluorescence measurements. The marked loss of photosystem II activity in infected leaves could be due to the loss of 47, 33, 28–25, 23 and 17 kDa polypeptides. It is concluded that phytoplasmal infection inactivates the donor side of photosystem II. This conclusion was confirmed by immunological studies showing that the content of the 33 kDa protein of the water-splitting complex was diminished significantly in infected leaves.     

微藻水热液化有机相最佳回收工艺研究

以微拟球藻为原料,研究微藻水热液化过程中多种参数对水热液化后有机物回收率的影响,包括温度、时间、溶剂比和pH等,从而获得微藻水热液化后有机物的最佳回收工艺条件。结果显示,在室温下进行有机相回收,保证回收溶剂比为20∶1(溶剂/水相不溶物;v/wt)、停留时间为10min、回收pH7,即可达到最佳回收效果。最佳条件下水热液化有机相的回收率为34%左右,且不同的回收温度和pH值对回收的有机相组分均会产生影响。     

界首市泉河小流域农业面源污染调查与评价

为了解界首市泉河小流域农业面源污染现状和特征，制定相应的农业面源防控措施，对流域内农业面源污染情况进行了调查分析和评价。通过对该典型小流域内陶庙镇、王集镇、代桥镇、泉阳镇4个乡镇的11个行政村的农田污染源、养殖污染源及人居生活污染源进行实地走访，调查数据应用等标污染负荷法进行评价分析。结果表明，界首市泉河小流域内4个乡镇的农业面源污染排放源中，农田污染源的污染物总量和污染负荷率分别是17.44 t和4.68％；养殖污染物排放总量和污染源负荷分别是99.31 t和26.63％；生活源污染物的排放量和污染负荷率最大，分别达到256.19 t和68.69％；在COD、TN、TP 3个主要评价因子中，污染负荷率最高的是COD，达80.22％，TN污染负荷率为9.22％，TP的污染负荷率为10.56％；养殖业污染和人居生活污染源是界首市泉河小流域农业面源污染的主要来源，也是该小流域农业面源污染防控的重点。在治理该小流域农业面源污染时，应大力发展绿色、生态、循环农业，严格控制畜禽养殖污染，加大农村人居环境整治，强化政府在农业面源污染治理中的统筹引导作用等。     

Micro-scale heterogeneity in urban forest soils affects fine root foraging by ornamental seedlings of Buddhist pine and Northeast yew

Urban soils are frequently characterized by a strong heterogeneity caused by intense anthropogenic activity and land use changes. Soil heterogeneity is commonly known to affect tree root development, but little has been detected concerning root foraging by ornamental trees in heterogeneous urban soils at micro-scale. In this study, Buddhist pine [Podocarpus macrophyllus (Thunb.) D. Don] and Northeast yew (Taxus cuspidata S. et Z.) were selected as ornamental tree species for a two-year study. In the first-year, seedlings were cultured under contrasting photoperiods to generate different morphologies. In the second year, seedlings were transplanted to pots filled with soils collected from an urban forest. Controlled-release fertilizers (N-P₂O₅-K₂O, 14-13-13) were evenly broadcasted to a half patch of the pot (heterogeneity) or to both halves (homogeneity) on the surface 5 cm beneath the pot-top at the rate of 0.135 g N seedling⁻¹. In the fertilized heterogeneous patch, larger Buddhist pine seedlings had greater dry weight, length, surface area, volume, number of tips, and morphological foraging-precision in fine roots. Compared to Northeast yew seedlings under natural photoperiod in the first year, those under the extended photoperiod had larger size, greater fine root biomass, and length but lower foraging-precision in the second year. N and P concentrations in second-year fine roots mainly increased with the availability of patches generated by fertilization for both species. In conclusion, the ability to forage for nutrients by ornamental tree seedlings in heterogeneous urban forest soils was species-specific. Buddhist pine seedlings had higher foraging precision in heterogeneous urban soils than Northeast yew seedlings due to their response to the extended photoperiod during culture.     

Radiation interception and radiation use efficiency of potato affected by different N fertigation and irrigation regimes

Three years of field experiments were carried out to explore the response of potato dry matter production, accumulated intercepted photosynthetic active radiation (Aipar) and radiation use efficiency (RUE) to five N levels providing 0, 60, 100, 140 and 180 kg N ha⁻¹ and three drip irrigation strategies, which were full, deficit and none irrigation. Results showed that, irrespective of years, dry matter production and Aipar were increased by prolonged N fertigation, even though N fertigation was carried out from middle to late growing season. The highest total and tuber dry matter and accumulated radiation interception in all three years were obtained when potatoes were provided with 180 kg N ha⁻¹. RUE on the other hand was not affected by N regime. Thus, increases in total dry matter production with increasing N levels were essentially caused by higher Aipar. The strongest response to N fertilization occurred when most N was applied early in the growing season and the latest N fertilization should be applied no later than 41–50 days after emergence. Deficit irrigation, which received ca.70% of irrigation applied to full irrigation, did not reduce radiation interception and radiation use efficiency.     

考虑地震载荷作用的水电机组转动部件强度分析

近年地震多发,震中地区的水电机组均受到不同程度的损坏。为研究地震后机组运行的可靠性,根据恢复运行后其运行条件和方式较灾前变化情况,把承受转动部件的上机架纳入分析对象,对应不同工况在上机架上采用应变片测试来验证计算分析的正确性。为了准确计算转动部件承受的载荷,采用CFD对水轮机内部流场进行三维数值模拟,将流场的计算结果作为结构场的初始条件。以地震力和地震加速度两种方式加载地震载荷,采用单向流固耦合方法对各部件进行地震载荷下的仿真计算与工程实测数据对比发现二者吻合较好。结果表明,文章采用的方法能正确评估水轮机结构强度,对机组灾后运行安全性分析有一定指导作用。     

Extended flowering and high weed resistance within two layer designed perennial “prairie-meadow” vegetation

Interactions between two canopy layers in a designed perennial herbaceous plant community were investigated over a period of four and a half years to see whether it was possible to create an urban landscape vegetation that was both flower rich for an extensive time period and resistant to weed colonization at very low levels of maintenance by sowing seed in situ. The ecologically novel plant community involved a tall over-canopy layer of 18 species of North American prairie and woodland edge forbs, and a shade tolerant under-canopy of eight European and North American, mainly woodland forbs. After 5 years the community was dominated by four over-canopy and two winter green under-canopy species. Interspecific competition generated by the sown biomass restricted weed colonization to very low levels, despite the experiment being surrounded by a weedy brownfield. The winter green canopies of the two dominant under-storey forbs closed down gaps within a winter deciduous, prairie-like vegetation, improving winter appearance and providing a major flowering display in spring. This vegetation is an attractive design model for more sustainable herbaceous planting in urban landscape space.