A new model has been developed for estimating density of plant or animal populations. For uniform, randomly-distributed or contagious populations which are distributed with one or two orders of aggregation, it employs the distance from each sample point to the nearest population member, from that individual to the nearest neighbour and from that neighbour to its nearest neighbour. The principle of the model is that an estimate of density is first obtained from the sample point-nearest population member distances.
Bushfires are common in Australia. They cause much damage and considerable loss annually. However, some use could be made of these wildfires for forest mapping if developments in colour and false-colour (colour infrared) aerial photography were more fully exploited. The advantages that colour and false-colour aerial photography have over pan-chromatic minus-blue aerial photography are analyzed for the Australian forest environment.
The forests and scrublands of the Taramakau catchment can be divided into six sub-climax associations and two seral associations. The sub-climax associations are subalpine scrub, bushline, rata-totara, red beech, silver beech and mountain beech forest. Except for silver beech forest and mountain beech forest, which are largely restricted to the Otehake tributary, site differentiation between these associations is generally altitudinal. These sub-climax associations appear to be regenerating satisfactorily except, perhaps, for red beech forest where there is a slight regeneration gap.
In the winters of 1968 and 1969 a survey was made of the growth and distribution of bryophyte and lichen species within communities on tree trunks, stone walls, non-metallic roofs and soil in Christchurch, New Zealand. The survey was stimulated by European and Scandinavian work which has shown that high levels of urban and industrial air pollution have caused severe reductions in the distribution of normally-abundant cryptogams. The present survey has demonstrated that a similar, but at present less severe, reduction in bryophyte and lichen flora occurs in Christchurch.
A brief outline of the history of air pollution measurements in Christchurch is given with an outline of the factors which influence them, such as climate, fuels used, topography, etc. A short discussion on the D.S.I.R. survey and other more recent work follows.
From the present data, it seems that sulphur dioxide levels have remained relatively constant and smoke in the central city area has decreased, whereas in the residential areas it has remained relatively constant. Levels in the months of June and July are now far removed from those in London.
SUMMARY: The vegetation of Whatupuke Island (240 acres, lat. 350 54' S., long. 174045' E.) is discussed under six headings: (I) Coastal herbs, grasses and shrubs; (2) Cordyline forest; (3)-(5) three phases in the succession after burning, with kanuka (Leptospermum ericoides) as a major species; and (6) puriri (Vitex lucens)-pohutukawa (Metrosideros excelsa) forest. Stands of the latter are probably the most mature to be found on the Chicken Islands.
A preliminary report is given of a survey, made in 1968, of various islands in the Chatham Group (240,000 acres, 440 S., 1760 30' W.). Regeneration of vegetation on South-East Island (540 acres) has been considerable since sheep were finally removed in 1961. Mangere Island (279 acres) was declared a reserve and all sheep destroyed in 1968. Recovery of its vegetation will provide increased habitat for the small populations of Forbes' parakeet and the Chatham Island robin, now found only on Little Mangere Island (10 acres).
Current surveys, encouraged by the New Zealand Ecological Society, are showing that a surprising number of native communities still survive on the Canterbury Plains. though in modified form. In 1969 a small area of scrub and grassland with undisturbed soils near Bankside was secured for a scientific reserve—the first of its kind on the Plains. A brief description is given.
The distribution and rates of spread of different growth forms of S. townsendii and of S. alterniflora in New Zealand are discussed and rates of sedimentation measured in Spartina plantations in Northland are compared with those recorded in Southland and in England.
Gross productivities of plantations in Northland are compared with English and American data and problems associated with foreshore protection are considered.
The Cockayne plots were sown in 1920 near Cromwell, Central Otago, on depleted country in a IS-inch rainfall zone. The initial growth of the sown species in the 13 enclosures showed that productive herbage species could be established, if not grazed. Pine and eucalypt species were also successfully grown.
The plots were opened to grazing in the 1930s, following which there was a change in plant composition from palatable to unpalatable species.