A systems approach to the description and interpretation of the landsurface of the northern half of the North Island, New Zealand

The paper examines a framework of approach within which landsurface analysis may be undertaken in the humid-temperate northern half of the North Island, New Zealand; an area exhibiting a wide range of lithologies and surface cover, with evidence of recent and current tectonic and volcanic activity, and undergoing active geomorphic processes'. The largely theoretical formulations of W. M. Davis, W. Penck and L. C. King are considered briefly and are rejected on both theoretical and practical grounds. General systems theory encompasses certain concepts and systems properties which have been applied by a number of geomorphologists. The open system property of dynamic equilibrium is examined, and is found to be inapplicable to the total landsurface of this region. The concepts of environment and sub-system are introduced and their relevance to the region illustrated by a physical hillslope model. Dynamic equilibrium is considered to be a possible state of certain hillslope sub-systems. Construction of a mathematical model to describe the total landsurface or the entire hillslope system is not feasible until hillslope sub-systems have been analysed. The form of a linear regression model applicable to hillslope sub-systems is introduced, and it is suggested that the pattern of the residuals from regression may be used as a statistical technique to assist in identifying .significant system boundary conditions, and to provide a quantitative indication of the influence of historical factors

The significance of vegetation, fire and man in the stabilisation of sand dunes near the Warburton Ranges, Central Australia

The vegetation cover of sand dunes and sandplain country in a part of Central Australia is aperiodically destroyed by fire, caused by lightning and Aboriginal activities. Subsequent mobilisation, transportation and redeposition of sand by wind suggests that these vegetated sand dunes are currently unstable

Soil macrofauna in agricultural landscapes dominated by the Quesungual Slash-and-Mulch agroforestry system, western Honduras

Smallholder agroforestry systems often incorporate features that are associated with abundant, diverse soil macrofauna populations. This study sampled soil macrofauna communities across four major land uses present within agricultural landscapes where the Quesungual Slash-and-Mulch Agroforestry System (QSMAS) has been increasingly adopted by smallholder farmers in western Honduras. The four land uses were: secondary forest (F), agroforestry plots of less than two years of age (AF 10), and silvipastoral fields (SP). Transect-based sampling of soil macrofauna using the standard Tropical Soil Biology and Fertility Institute (TSBF) method was employed in both the dry season and wet season. All four land uses sampled in this study harboured diverse, abundant and highly variable soil macrofauna populations. In the dry season, total density of soil macrofauna ranged from 1265 ± 308 individuals m?2 in F sites to 1924 ± 436 individuals m?2 in AF < 2 sites. In the wet season, total density ranged from 907 ± 294 individuals m?2 in F, to 1637 ± 358 individuals m?2 in AF < 2. Biomass values followed a similar pattern, ranging from 4.3 ± 1.1 g m?2 to 24.8 ± 8.2 g m?2 in the dry season and from 13.1 ± 3.0 g m?2 to 41.9 ± 11.1 g m?2 in the wet season. In order of decreasing strength of statistical relationship, soil depth, land use and season were all related to some aspects of soil macrofauna density, biomass and community composition. At a broad functional group level, soil macrofauna community composition was very similar across all four land uses. The results suggest that the agricultural practices associated with the Quesungual agroforestry system may promote a relatively abundant, diverse soil macrofauna community. The presence of an abundant soil macrofauna community may have important effects on aspects of soil quality that are particularly important to resource-limited smallholder farmers

A study of risk factors for acquisition of Epstein‐Barr virus and its subtypes

Background. Risk factors for primary infection with Epstein-Barr virus (EBV) and its subtypes have not been fully investigated. &lt;br/&gt; Methods. Questionnaires and serum samples from a total of 2006 students who entered Edinburgh University in 1999–2000 were analyzed to examine risk factors for EBV seropositivity, both overall and by EBV type. &lt;br/&gt; Results. The prevalence of EBV seropositivity was significantly increased among females, older students, those who had lived in tropical countries, those with siblings, and those who were sexually active, particularly if they had had numerous sex partners. Risk was lower (1) among students who always used a condom than among those who had sexual intercourse without one and (2) among female oral-contraceptive users than among sexually active nonusers. Risk factors for type 1 EBV infection were similar to those for EBV overall. No associations were found between nonsexual risk factors and type 2 infection. Sexual activity increased the risk of type 2 infection, but the increase in risk with number of sex partners was less consistent than for type 1 infections. Dual infection was uncommon, but the patterns of risk appeared to be similar to those of type 1 infection. &lt;br/&gt; Conclusion. This study provides further evidence that EBV may be sexually transmitted and some suggestion that the risk factors for type 1 and type 2 infection differ