New Zealand Journal of Ecology (2000) 24(2): 111- 121

Microclimate gradients across a forest edge

Research Article
R. J. Davies-Colley 1
G. W. Payne 1
M. van Elswijk 2
  1. National Institute of Water and Atmospheric Research Ltd, (NIWA), P.O. Box 11-115, Hamilton, New Zealand
  2. Institute for Inland Water Management and Wastewater Treatment, P.O. Box 17, 8200 AA Lelystad, The Netherlands

Despite the importance of forest edges in ecology, only one study has previously been carried out in New Zealand on the modification of climate across forest edges. We measured light exposure, wind speed, air and soil temperature, and vapour pressure deficit (VPD) perpendicular to a north-south aligned, mature, edge of native broadleaf rainforest adjoining grazed pasture. At a point 80 m into the forest from the edge, light was only c. 0.7% and wind speed c. 20% of that in the open, and there was much less diurnal fluctuation in soil temperature, air temperature and VPD. The gradient of microclimate near the edge, as measured with a third (mobile) weather station, was abrupt for soil temperature and similar to the pattern of light exposure, with almost complete change over about 10 m. The gradient was less steep for wind speed, air temperature and VPD, with at least 40 m being required to stabilise these variables when wind was directed into the forest. These findings suggest that forest buffers of at. least 40 m may be needed to protect forest reserves and streams from climatic exposure.