VEGETATION AND ENVIRONMENTAL PATTERNS ON SOILS DERIVED FROM HAWKESBURY SANDSTONE AND NARRABEEN SUBSTRATA IN KU-RING-GAI-CHASE NATIONAL-PARK, NEW-SOUTH-WALES

The vegetation patterns in the Central Coast region of New South Wales have been extensively studied with respect to single environmental va riables, particularly soil nutrients. However, few data are available on the effects of multiple environmental variables. This study examine s the relationships between vegetation and multiple environmental vari ables in natural vegetation on two underlying rock types, Hawkesbury S andstone and Narrabeen Group shales and sandstones, in Ku-ring-gai Cha se National Park, Sydney. Floristic composition and 17 environmental f actors were characterized using duplicate 500 m(2) quadrats from 50 si tes representing a wide range of vegetation types. The patterns in veg etation and environmental factors were examined through multivariate a nalyses: indicator species analysis was used to provide an objective c lassification of plant community types, and the relationships between vegetation and environmental factors within the two soil types were ex amined through indirect and direct gradient analyses. Eleven plant com munities were identified, which showed strong agreement with previous studies. The measured environmental factors showed strong correlations with vegetation patterns: within both soil types, the measured enviro nmental variables explained approximately 32-35% of the variation in v egetation. No single measured environmental variable adequately descri bed the observed gradients in vegetation; rather, vegetation gradients showed strong correlations with complex environmental gradients. Thes e complex environmental gradients included nutrient, moisture, and soi l physical and site variables. These results suggest that a simple 'nu trient' hypothesis regarding vegetation patterns in the Central Coast region is inadequate to explain variation in vegetation within soil ty pes.