Spatial coupling of plant recruitment processes : vegetation change and the regeneration ecology of Hoon Hay Valley, Port Hills, Canterbury, New Zealand
Thesis DisciplineEnvironmental Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Spatial coupling of plant recruitment processes was measured during 1996 in a dynamic post-agricultural successional environment on the Port Hills of Banks Peninsula. Steps along a conceptual vegetation→seed rain→seedlings recruitment continuum were measured, and the degree of spatial coupling (as measured by correlations of DCA ordination axis position) between each determined. Spatial coupling of recruitment processes provides a direct measure of potential vegetation change; tight coupling indicates vegetation is changing little as each recruitment step is spatially similar to the step previous, whereas weak coupling indicates dynamic change as steps are not spatially related. Coupling was weakest at the vegetation→seed rain and seed rain→seedlings stages, indicating that at these stages plant dispersal and vegetation change are most strongly expressed. Coupling was strongest at the vegetation→seedling stage, indicating that processes associated with seedling establishment and survival offer the strongest impediments to vegetation change. Coupling of all steps was weakest at the habitat-type level, with spatial patterns related to presumed successional age, indicating that vegetation change is proceeding in a process of within-valley succession and species migration. This result confirms those of previous studies which have investigated vegetation change on the Port Hills and Banks Peninsula. It indicates that with the removal of proximate causes of disturbance (fire, grazing, agriculture, etc.) the overwhelming trend of vegetation change in post-agricultural successional environments such as this is toward forest dominated by native species.