Abstract
Plant opal analysis of A horizons of four Andisols (Tirau silt loam, Taupo sand, Egmont black loam and Patua loam) in North Island, New Zealand was made to reveal their vegetative histories. The plant opal composition of Tirau silt loam, Egmont black loam and Patua loam is dominated by phytoliths derived from broadleaved trees, Taupo sand being characterized by phytoliths from ferns. Although the present vegetation is mainly improved pastures, the previous vegetaion on Tirau silt loam, Egmont black loam and Patua loam, therefore, is presumed to have been forests, and on Taupo sand ferns. Grass opals such as Festucoid types, elongated types and point-shaped types derived probably from exotic grasses, members of Festucoideae, are also found in these four soils. In conclusion, the plant opal composition of the Andisols in New Zealand is very different from that of Kurobokudo (Ando soils) in Japan characterized by phytoliths from Gramineae.
