Abstract:
Low lake levels temporarily reduced the proportion of native vascular plants by removing available shallow-water habitats through erosion, siltation or desiccation. High lake levels have allowed native vascular plants to re-establish from seed and rhizomes. Fluctuations in water level appear to have reduced the long-term replacement of native species by L. major, which has nevertheless spread progressively around the lake. Water-level fluctuations enhanced its rate of fragmentation, and thus its dispersal and establishment. The annual increase in the proportion of L. major has been primarily at the expense of the shallow-water Characeae but also partly by competitive displacement of native vascular plants. The SW inlet of Lake Rotoma had an exceptionally high plant density, with up to 3518 g/m2 dry weight of L. major (believed to be a world record for submerged plant biomass); this is attributed to local enrichment and protection from wave exposure. -
