Marked sites established around Port Ross in 1973 were re-examined in 1983 to measure changes in the vegetation and assess the impact of goats and pigs. Goats had not increased in numbers, nor extended beyond their earlier range, but they were seen higher on the Hooker Hills. Pigs were scarce, but their sign was seen throughout. Photopoints and numerical methods both showed that Chionochloa antarctica tussock was eliminated or greatly reduced where goats and pigs occurred together, and where only pigs were present it was reduced slightly.
An approach is outlined for synthesising current understanding of nitrogen dynamics in natural grasslands and extensively managed grassland systems. The increasing complexity of models is illustrated from recent literature, first conceptualising and eventually process-simulating the dynamics of nitrogen, especially in the soil sub-systems of grasslands. Some comparisons are made between New Zealand and North American grasslands in the magnitude of some N pools and fluxes and some of the principal features of soil biological studies are noted.