Patterns and dynamics of urban forests in relation to land use and development history in Guangzhou City, China

Trees in cities display a varied pattern that is often moulded by a city's physical fabric and its evolution through time. The town plan expressed in spatial dimension as land use, and in temporal sense as development history, furnishes a framework to evaluate the intricate association between city and trees. Guangzhou city, the premier metropolis of south China, has been established for 2800 years, and has a long history of urban greening and heterogeneous land use. Five urban districts, which represent old, middle-aged and young stages of development and cover the bulk of the city's built-up zones, form the study area. Interpretation of aerial photographs is used as a basis to classify the urban forest into three types, and to design a sampling scheme for studying trees in urban parks, institutional grounds and roadsides. District history has bequeathed a plethora of configurations in terms of buildings, roads and land uses, accompanied by plantable spaces of dissimilar dimensions, geometry and quality. The districts display diverse tree attributes such as frequency, density and species diversity. Young districts, with lower density, more institutional uses and wider roads, present more opportunities for greening. Recent shifts in landscape fashion have introduced a significantly different treescape. A few exceptionally large parks and institutional sites play a pivotal role in the city's tree assets. Parks, roadsides and institutional forests have different tree-stocking rates and species assemblages. Implications for future planting and management of urban trees in different situations, and for the greening of other cities in China, and other developing countries, are explored.     

Development of the 1990 Kalapana Flow Field,Kilauea Volcano,Hawaii

The 1990 Kalapana flow field is a complex patchwork of tube-fed pahoehoe flows erupted from the Kupaianaha vent at a low effusion rate (approximately 3.5 m³/s). These flows accumulated over an 11-month period on the coastal plain of Kilauea Volcano, where the pre-eruption slope angle was less than 2°. the composite field thickened by the addition of new flows to its surface, as well as by inflation of these flows and flows emplaced earlier. Two major flow types were identified during the development of the flow field: large primary flows and smaller breakouts that extruded from inflated primary flows. Primary flows advanced more quickly and covered new land at a much higher rate than breakouts. The cumulative area covered by breakouts exceeded that of primary flows, although breakouts frequently covered areas already buried by recent flows. Lava tubes established within primary flows were longer-lived than those formed within breakouts and were often reoccupied by lava after a brief hiatus in supply; tubes within breakouts were never reoccupied once the supply was interrupted. During intervals of steady supply from the vent, the daily areal coverage by lava in Kalapana was constant, whereas the forward advance of the flows was sporadic. This implies that planimetric area, rather than flow length, provides the best indicator of effusion rate for pahoehoe flow fields that form on lowangle slopes.     

青藏高原地区的大气浑浊度特征

本文通过比较Angstrom大气浑浊度系数的各种计算方法,得出了适合青藏高原地区的大气浑浊度系数的计算方法。据此利用1982年8月至1983年7月青藏高原地区部分观测站的太阳直接辐射资料计算了大气浑浊度系数,分析了它的变化特征。同时利用常规气象要素拟合得出了计算大气浑浊度系数的经验公式,计算和分析了青藏高原地区大气浑浊度系数的时间和空间分布。     

Effect of turbulence and inorganic carbon supply on growth ofDunaliella viridis Teodoresco

Turbulence is known to enhance growth in microalgae. We studied the possible effects of the extra inorganic carbon supplied to the cultures when air bubbling is the source of turbulence. A set of experiments was carried out to separate the effects of the subsidiary action of agitation on growth from those due to possible carbon enrichment from air CO₂ when air bubbling was the source of mixing. It was found that air bubbling does not induce an increase of the concentration of inorganic carbon in HCO ₃ ^– -enriched growth media, and that no differences appear between air-bubbled and CO₂-free air-bubbled cultures. On the other hand, photosynthetic O₂ was accumulated in the medium in non-mixed cultures, which showed higher respiration and lower photosynthetic rates, probably due to photoinhibition induced by oversaturation of O₂. Growth rate, maximal cell density and photosynthetic efficiency were higher in aerated cultures than in non-aerated ones.