Growth responses of five forest plant species to the soils formed beneath New Zealand kauri (Agathis australis)

The considerable influence kauri (Agathis australis) exerts on its soil environment has been implicated in explaining the floristic associations with kauri stands. Using a shadehouse experiment, this study assesses this hypothesis by comparing the influence of soils under kauri and adjacent broadleaved forest on the growth and nitrogen status of five forest plant species of varying levels of association with kauri. I found a negative effect of kauri soils on the growth of mahoe (Melicytus ramiflorus, typically absent beneath kauri) and rimu (Dacrydium cupressinum, distribution independent of kauri), compared with their growth in broadleaved forest soils, but a neutral effect of soil type on the growth of korokio (Corokia buddleioides, kauri associate species), kauri seedlings and hangehange (Geniostoma ligustrifolium var. ligustrifolium, kauri-independent species). There was no effect of soil type on leaf nitrogen concentration. The results are consistent with a link between kauri-induced soil conditions and plant community composition.