Effects of silvicultural treatments on summer forest microclimate in southeastern Missouri Ozarks

The effects of silvicultural treatments (e.g., even-aged management, EAM, and uneven-aged, UAM) on 4 microclimatic variables (air temperature, incoming solar radiation, humidity, and soil temperature) were examined in oak forests of southeastern Missouri Ozarks, USA. Nine mobile climatic stations were used to collect field data during the summers of 1995 (pre-harvest), and 1997 and 1998 (post-harvest). Spatial variation of air temperature at 2 m height increased 96 and 35% (2-year average) after harvest in UAM and EAM sites, respectively as quantified by 95 % confidence intervals (CI). UAM increased the variability of air temperature at the lower end of the daily range in the CI more than at the upper end, while EAM had a stronger effect on raising spatial variation at the upper end of the CI than at the lower end. Spatial variation of soil temperature within an 80 x 80 m grid increased significantly during daytime after harvest, especially at the surface, but did not change much during nighttime. EAM resulted in a larger increase of soil temperature variation than did UAM. Greater amplitudes of diurnal soil temperatures (especially at the surface) were observed at depths of 0, 5, and 10 cm and were more evident at the EAM site after harvest. The duration of variation in post-harvest soil surface temperature during daytime was about 3 times longer than pre-harvest at the EAM site. Spatial variation in radiation increased 56 and 128 % in UAM and EAM sites after harvest, respectively. Except for radiation, significance levels of differences in means of microclimatic variables were reduced after harvest among the 3 Ecological Land Types (ELTs); the spatial variation of microclimate was smaller among ELTs within the same treatment than between treatments. Our results suggested that, usually, EAM affected the microclimate more than UAM did, especially in raising soil temperatures on northeast slopes (ELT18).