Microclimate gradients across a forest edge

Despite the importance of forest edges in ecology, only one study has previ ously been carried out in New Zealand on the modification of climate across forest edges. We measured light exposure, wind speed, air and soil tempera ture, and vapour pressure deficit (VPD) perpendicular to a north-south alig ned, 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 w ind speed c. 20% of that in the open, and there was much less diurnal fluct uation in soil temperature, air temperature and VPD. The gradient of microc limate near the edge, as measured with a third (mobile) weather station, wa s 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 f or wind speed, air temperature and VPD, with at least 40 m being required t o stabilise these variables when wind was directed into the forest. These f indings suggest that forest buffers of at. least 40 m may be needed to prot ect forest reserves and streams from climatic exposure.