Studies on the Population Dynamics of Typha at Lake Pukepuke

Harper (1977) has recently stressed the significance of the modular construction of plants. Plants respond to density not so much by changing the proportions of their parts, as by changing the number of basic modules of which they are composed. In the case of deciduous rhizomatous perennials, such as Typha orientalis, the basic module can be defined as a single above-ground shoot and its associated rhizome and adventitious roots. Although we may traditionally regard the expansion of clones of such species as being due to "vegetative reproduction" the process does not differ fundamentally from the growth of a new shoot on a tree; both are better regarded as the production of new modules vegetative growth. The shoot growth of stands of Typha orientalis was studied at Lake Pukepuke from 1968 to 1973. The lake is situated on coastal sand-dune country at approximate latitude 40°21' S, longitude 1 7 5 ° 16' E, in the Manawatu District of the North Island. It is currently managed as a Waterfowl Reserve by the Wildlife Service (Department of Internal Affairs) and monitored as a Representative Catchment by the hydrology section of the Ministry of Works and Development. The studies summarised here comprised part of a research programme covering the history of the lake ecosystem and the changes in energy flow patterns occurring in Typha stands during hydroseral development. These studies are being prepared for publication. This resume deals only with the population dynamics of the above-ground vegetative shoots of Typha.