Discaria Toumatou Research Articles

Reproductive biology ofDiscaria toumatou(Rhamnaceae)

Abstract The flowers of Discaria toumatou (Rhamnaceae) at Cass, Canterbury, are visited by a wide range of nectar and pollen collecting insects. In flowers bagged to exclude insects, only cross-pollinated flowers set fruit, with no fruit set in self-pollinated or control flowers. Fruit set in flowers exposed to insect visits was 6.7% in control flowers and 3.3% in self-pollinated flowers, but increased to 15% in cross-pollinated flowers. Pollen transfer between plants is clearly needed for fruit production but insects do not transfer sufficient amounts of pollen for full fruit set. However, low fruit set even in cross-pollinated flowers and no fruit set on many individual plants indicate that other factors besides pollinator activity limit fruit production. The ability of the unbroken fruit to float in sea water and the self-infertility suggest that a fruit containing more than one seed is the unit of long-distance dispersal across oceans for the ancestor of this species.

Effects of grazing on indigenous shrubs in tussock grassland at Cass, Canterbury, New Zealand

Abstract When enclosures were contrasted with comparable control areas, the effects of grazing over a 17-year period on survival, establishment, and growth were determined for six montane shrub species—Discaria toumatou, Cassinia fulvida, Coprosma parviflora, Coprosma propinqua, Corokia cotoneaster, and Hymenanthera alpina. One exclosure was in open grassland whereas a second encompassed the grassland-beech forest boundary. The shrub populations in the exclosures generally showed greater height growth and lower recruitment rates, but no difference in survival rates, when compared with populations in control areas. These trends do not apply to every species and site. Cassinia fulvida in particular showed a dramatic decline in population size that is not related to grazing. For most species, high survival rates, low height growth rates, and constant recruitment contribute to the relative stability of shrub populations.

Correlation between tree-ring width and climate in two areas in New Zealand

Abstract Correlations between tree-ring width and monthly mean temperature, rainfall, and moisture surplus were investigated in two areas of contrasting rainfall. Species considered were: Podocarpus hallii, Phyllocladus alpinus, Discaria toumatou, and Pinus nigra from Lake Tekapo (annual rainfall range 57-104 cm); and Nothofagus solandri, Phyllocladus alpinus, and Pinus contorta from Mt Ruapehu (annual rainfall range 180-290 cm). The gross morphology of the growth rings is briefly described. Ring indices were derived by adjusting ring width measurements for the mean growth of the trees. Only 9 to 37 percent of the total variation in these ring indices could be attributed to differences in climate or other factors in the different years. Most species showed significant positive correlations between ring indices of successive years. Average ring sequences are given for each species and sequences suitable for cross-dating indicated. At Mt Ruapehu the ring indices were principally correlated with temperature,...

The biology of matagouri

The biology of matagouri

Fixation of Nitrogen-15 by Excised Nodules of Discaria toumatou

Discaria toumatou (Rhamnaceae) has previously been recorded as a nodulated plant in New Zealand1. The nitrogen-fixing ability of its nodules has now been studied experimentally.

Root Nodules in Discaria toumatou Raoul Choix

Discaria toumatou is a thorny shrub belonging to the Rhamnaceae. It is endemic in New Zealand and is common in mountain valleys on the eastern side of the Southern Alps. The root systems of plants growing in a number of widely separated localities in the South Island have been examined and all have been found to be nodulated.

Observations on the Vegetation of Screes in Canterbury, New Zealand

In the drier mountains of the eastern and north-eastern regions of the South Island of New Zealand, there occurs very commonly a type of scree inhabited by a community of plants rarely found in any other situation. Although belonging to several different families, these plants have many characters, in common which distinguish them from plants of other alpine associations. This paper deals mainly with observations made on a large scree near the Canterbury University College Mountain Biological Station at Cass, 70 miles inland on the midland railway from Christchurch, New Zealand. This particular scree forms the northern slope, from 3000 to 6000 ft. above sea-level, of Mount Bailey, the northernmost peak of the Craigieburn Range not far from the main ranges of the Southern Alps (P1. 13, phot. 1). During the summer in this region, fine days are common, and while the brilliant sunlight of the high clear atmosphere raises the stony surfaces of the screes to a temperature such that they are unbearable to touch, blustering hot dry winds frequently sweep across the slopes from the west. In winter, snow may cover the ground for several weeks at a time. The annual rainfall of the district is 50 in., distributed fairly evenly throughout the year. The vegetation of the region consists of a tussock grassland association dominated by Poa caespitosa and Festuca novae-zealandiae, modified in local areas by variations in conditions. In sheltered situations small stands of beech (Nothofagus cliffortioides) replace the tussocks, while a shrubland association (Cassinia fulvida, Discaria toumatou, Leptospermum scoparium, etc.) occurs in many exposed places. At higher altitudes (above 3500 ft.) the short-tussock association (Poa-Festuca) gives way to a narrow belt of the tall-tussock, Danthonia raoulii, which forms the uppermost border of the grassland vegetation. Other high-mountain plants are found on rocks and in other stable situations above this altitude, usually including species of Hebe and Celmisia. Around the edges of the screes several small-leaved shrubs are the first unspecialized plants to enter the partially stabilized debris, e.g. Podocarpus nivalis and various members of the Epacridaceae, including species of Dracophyllum. Vegetation of screes outside New Zealand appears to be of two kinds. On very unstable soils certain specialized plants sometimes occur, which can survive movements of the surrounding stones. On slightly less mobile soils, plants are recruited from the surrounding stable soil associations of heath or rock. Such vegetation is often in a state of flux, since large areas may be buried by scree movements (Schroeter, 1926; Harshberger, 1929; Tansley, 1939). Very few papers dealing with the ecology of unstable screes appear to have been published, and those dealing with screes in Britain, Europe and America are mainly concerned with the successive phases of vegetation as consolidation takes place