Age‐states, population structure, and seedling regeneration of Chionochloa pallens in Canterbury alpine grasslands, New Zealand

Abstract

Abstract. Age‐states, population structure, and seedling regeneration of the grass Chionochloa pallens were investigated in eight alpine grassland stands representing the range of canopy cover (ca. 5–75 %) and basal area (112 ‐ 3889 m2/ha‐1) in the headwaters of the Avoca catchment, Canterbury, New Zealand. In open‐canopy stands (< 50 % canopy cover, < 2000 m2/ha‐1 basal area) C. pallens individuals were clearly distinguishable. Rela‐tionshipsbetweenbasal diameter, number of tillers, height, and % crown death suggested four putative age‐states: ‘seedlings‘, ‘juvenile tussocks’, ‘mature tussocks’ and ‘senescent tussocks’. Four types of population structure were identified depending onthe proportions of seedlings and juvenile and mature tussocks. C. pallens seedlings were present in seven stands at densities ranging from 0.6 to 123.4 / m2. They were most frequent on microsites protected from frost‐heave by short herbaceous vegetation or litter, but with little competition from taller vegetation. Differences in seedling densities between stands partly reflected the proximity and abundance of seed sources and degree of protection from frost‐heave. C. pallens population structures appear to be influenced by the frequency and magnitude of geomorphic disturbances and browsing by introduced animals.