Seasonal changes in semi‐arid vegetation of Central Otago, New Zealand

Abstract

Seasonal changes in the semi‐arid grassland vegetation of Central Otago, New Zealand, are examined using data collected in nine pairs of spring and autumn sampling dates at five long‐term plots, and data from consecutive autumn, spring, and summer surveys across an environmental gradient. Seasonal changes are small in relation to those occurring in the vegetation from year to year, and to spatial differences in vegetation across the landscape. Seasonal changes in community characteristics and in the abundance of most species differ between years. Climatic control of seasonal change appears to be complex and site‐specific. Greater seasonal variation, in both species presence and species abundance, is found in shady sites and on deeper soils. Spring vegetation tends to be more variable and less well structured than autumn vegetation. It is suggested that the annual soil moisture cycle of winter recharge and summer depletion leads to a random element in the spring vegetation (i.e., the relatively widespread germination of distributed seed under temporarily favourable climatic conditions) and that, by autumn, species are more strongly confined to particular environments according to their tolerance of moisture stress.

Keywords:

• seasonal changes
• New Zealand
• Central Otago
• semi‐arid
• community structure
• moisture stress
• long‐term monitoring