A Forest Succession in the Catlins Ecological Region, South-east Otago, New Zealand

Forest containing rata (Metrosideros umbellata) and kamahi (Weinmannia racemosa), with scattered trees of silver beech (Nothofagus menziesii), was sampled on Cedar Hill, Owaka Valley, Catlins Ecological Region. Diameter frequency distributions, age estimates, and basal area measurements show single cohort establishment of rata and kamahi, whereas three establishment phases of silver beech are evident. Tree population structures, the presence of many large dead and decaying manuka (Leptospermum scoparium) stems, and the absence of evidence of windthrow or landslip, suggest that the vegetation originated 250-300 years ago as a result of fire. Initially, manuka and a few silver beech established together. Natural opening of the manuka canopy 50-100 years later allowed invasion by rata, kamahi and a second cohort of beech. A third episode of beech establishment occurred about 70 years ago. Eventually forest structure will be similar to that of adjacent older, more diverse forest.