Distribution of three Hieracium species in the Mt Possession area, mid Canterbury, New Zealand

The abundance of three Hieracium species was examined in the Mt Possession area in relation to soil and other site variables. For H. pilosella cover, total soil P and elevation were the most significant combined predictors, b ut together explained only 30% of the variation. H. pilosella had the highe st cover at relatively high P levels and at low elevation. The presence of H. praealtum was predicted by moisture index, while that of H. caespitosum was predicted by tussock height and C:N ratio in the soil. However, none of the measured site variables significantly predicted the cover of H. praeal tum and H. caespitosum. The present cover distributions of H. pilosella and H. praealtum were compared with a 1960s survey in the area. The distributi on of H. pilosella cover frequency had changed from being skewed with the s pecies absent or in low cover in 1960s, to becoming common and the cover fr equency for H. pilosella showing a normal distribution with the highest fre quency at cover class 2 (5-25% cover). H. praealtum was absent or in relati vely low cover in both surveys. The P response curve for H. pilosella contr adicts other studies, and shows the need for specificity about what environ ment and vegetation are studied. The differences in spatial and temporal va riation among the three Hieracium species also emphasise the need to consid er therm separately when discussing their ecology and management.