Provenances of naturalised plants in Australasia

In both Australia and New Zealand, numbers of naturalised flowering plant species have increased steadily since the start of European settlement, and this process shows no sign of abating. Plants native to Western Europe, the Mediterranean basin and the Middle East predominated during the mid‐nineteenth century, but in recent decades other geographical areas (notably the Western Hemisphere, Asia and Southern Africa) have become important sources of adventive plants. Today, the composition of ensembles of naturalised species more closely conforms to the diversity of physical environments in the host area. Species native to mediterranean‐type climates tend to dominate in Victoria, species from the Asian and American tropics are especially significant in Queensland, and species from cool temperate regions compose the bulk of the naturalised flora of south‐western New Zealand.     

Dryland salinity in a subcatchment at Glenthompson,Victoria

Dryland salinity is a widespread and serious environmental problem in western Victoria. As a result river environs and farmland have been seriously degraded with loss of habitat, reduced farm production and increased erosion. Until recently, the preferred method of salinity investigation was centred around expensive drilling programs to obtain information on groundwater provinces. More recently, electromagnetic surveys have provided the means of rapidly assessing the levels of soil and water salinities present within the landscape. At a site south of Glenthompson, Victoria, the results of an electromagnetic survey together with an investigation of relevant soil properties are being used to plan salinity control options. High recharge areas do not appear to be present in the study district. The effects of agronomic control options, such as the establishment of perennial grasses, can be predicted by the use of a monthly water balance whereby climatic factors and the crop's efficiency in plant water use can be related. The likely reduction in deep infiltration can then be estimated.     

CHILDREN'S PERCEPTION OF A DOWNTOWN SHOPPING CENTER

This paper offers an exploratory investigation of the effects of a child's age on three behavioral constructs (awareness space, activity space, and attitude) concerning a downtown shopping center in Bristol, England. The data are elicited from three samples of Bristol school children defined according to age and are analyzed using statistical inferential procedures. The results disclose that awareness space and activity space consistently increase with age. In addition, attitudinal responses to specific features of the shopping center exhibit a gradual change over a long-term period.     

Climatic deterioration and the end of the Gortian Interglacial in sediments from Derrynadivva and Burren Townland,near Castlebar,County Mayo,Ireland

Pollen and macrofossil analyses of two sequences of organic sediment in western Ireland have allowed the recognition of the latter parts of the Gortian Interglacial, a Middle Pleistocene temperate stage. The palaeobotanical information from the two sites identifies the preservation of partial sequences from the Gortian Interglacial (believed to be the equivalent of the Hoxnian Stage of Britain and the Holsteinian of Europe). The pollen and macrofossil data from one of the sites, Derrynadivva, span the middle and latter parts of the temperate stage. The results show that fire influenced the vegetation throughout the middle part of the temperate stage, and the termination of the organic depositional sequence appears to have been due to environmental deterioration. The former is identified through the abundant occurrence of charcoal in the sediments, whereas the latter is apparent in the sediment sequence and in the reworking of thermophilous pollen types into the upper part of the deposit. The second site, Burren Townland, records only part of the later zones of the interglacial, but the ericaceous assemblages of the latter part of the Gortian Interglacial are well developed and well preserved. Macrofossil analyses and scanning electron microscopy work on the pollen at the latter site has allowed the recognition of Rhododendron ponticum, adding to previous records of this species, which now has a very disjunct European distribution.     

Mercos — A simple Teflon sampler for ultratrace metal analysis in seawater

This paper describes an uncomplicated sampling technique for ultratrace element analysis of coastal and surface seawaters (maximum depth 100 m). The sampler system is very easy to operate. To prevent contamination problems, interchangeable 500-ml Teflon bottles are used as both sampling and storage vessels. The seawater samples are stabilized in situ by preacidifying the sampling bottles. For the determination of mercury in seawater the desired system has been developed: sampling bottle = storage bottle = reaction vessel.     

Water resource management in the USA: a case study of large dams

The construction of large dams in the USA reveals a rapid growth in activity in the post-Second World War period, with the largest number of dams being inaugurated in the mid-1960s. Texas, with 823 dams, is the state with the largest number, followed in turn by California, Oklahoma, Pennsylvania and Colorado. At the other extreme some states have fewer than a dozen dams. Although there are large variations in the number of dams between states nearly all of them record peak constructional activity between the late 1950s and early 1970s. Surprisingly, most dams have relatively small reservoirs with about 70 per cent of the total having capacities of less than 10⁶ m³. Over two-thirds of all dams have been constructed with a single aim in view, with flood control being the most important reason. Only 1.5 per cent of all dams are utilized for four or more purposes. The objectives behind dam construction reveal changes since the 19th century. In the early years of the 20th century irrigation, hydro-electric power generation and water supply were the most important reasons for dam construction, whereas in the post-1950 period flood control stands out as the dominant activity. Changing technology, the introduction of specific legislation and changing attitudes to the environment have been the major influences on dam-building activity over the period studied.     

Characteristics of VLF emissions manifested by their cross-spectral phase information

Natural VLF emissions received by a single antenna can be characterised at each point in the emissions' frequency-time domain by a power and a phase. Emissions received at a single point by two antennae with a fixed relative orientation in space can be similarly described by the cross-spectral power and relative phase. It is shown that the cross-spectral phase contains information on the propagation characteristics of the waves which is better utilised in wave analysis than the power. In fact, the phase information allows weak signals to be identified more readily than is possible from a power spectrogram. It also allows the recognition of waves propagating with different wave normal directions. Data from the Geos-1 electric and magnetic antennae, pre-processed by the on-board correlator, are used to study the cross-spectral characteristics of VLF hiss and chorus in the Earth's magnetosphere.