Modification of an orchard climate with increasing shelter-belt height

Climatological differences accompanying changing land use from traditional pastoral farming to fruit orchards were measured over a 6-year period. During this time evergreen shelter belts, which subdivide orchards into 0.5-ha blocks, grew from establishment to an average final height of nearly 10 m. The main result was a progressive reduction in the relative wind run at 6 m which was linearly related to shelter height with a slope of -6% m^-1. In this humid coastal region, shelter did not appear to influence minimum air temperatures. On the other hand, significant increases in 09.00 h soil and maximum screen air temperatures amounting to around 1°C for 10-m-high shelter were measured. These modest temperature increases were also linearly related to shelter height.