scrub

The vegetation of Campbell Island and its offshore islets was sampled quantitatively at 140 sites. Data from the 134 sites with more than one vascular plant species were subjected to multivariate analysis. Out of a total of 140 indigenous and widespread adventive species known from the island group, 124 vascular species were recorded; 85 non-vascular cryptogams or species aggregates play a major role in the vegetation. Up to 19 factors of the physical environment were recorded or derived for each site.

Vegetation on 5 km (c. 100 ha) of the braided bed of the Orongorongo River, Wellington, was sampled in March from 1973 to 1990. The riverbed has become aggraded since an earthquake in 1855. Surface water covered little of the riverbed; Callitriche stagnalis was the only common vascular aquatic plant. Most grasses and dicot herbs were adventive. The scabweed Raoulia tenuicaulis was the commonest dicot. The extent of plant cover was measured on 300 circular plots (radius 1.5 m); it ranged between years from 5% to 22%, depending on the severity of floods.

Hawthorn (Crataegus monogyna) is a naturalised tree that is classified as a noxious plant in several counties in the eastern South Island. It is locally abundant in lowland forest remnants, and with the indigenous spiny shrub matagouri (Discaria toumatou), on grazing land in Canterbury. Two scrub sites near Porters Pass, where the original hawthorn trees still existed, and a forest site near Kowai Bush were sampled by measuring stem diameters and counting growth rings, to determine the age structure and dynamics of hawthorn.