Temperature and relative humidity regimes in the stump habitat ofFomes annosuswere characterized in a red pine plantation in Pennsylvania. Data were taken automatically at 2-h intervals around several stumps. A portion of these data from several periods of the year is presented.The measurement of temperature at four levels (soil, litter, stump-top, and ambient at 2-ft above the litter) around stumps showed that important differences existed among the separate levels at one stump, as well as among identical levels at separate stumps.Relative humidity, measured at two levels (sporophore locations and 2ensp;ft above the litter) around stumps indicated that (i) a greater diurnal fluctuation and a generally lower relative humidity occurred at the 2-ft level, although few differences among stumps existed at this level; and (ii) the relative humidity at sporophore locations was comparatively high and varied with the position of the sporophore location on the stump, i.e., relative humidity adjacent to sporophores below the litter or in shaded niches was higher than those exposed to ambient conditions.Root and adjacent soil temperatures, measured at several levels beneath stumps, were similar for any one period except near the soil surface. Generally, the temperatures of the roots and soil increased with depth during outgoing radiation periods. However, the trend for incoming radiation periods varied with season, e.g., temperatures increased with depth in January and March and decreased with depth in July and October.The nature of these differences in fungus microclimate in the stump habitat varied with season, time of day, proximity of the soil surface, and the interaction of stand climate and vegetation. These differences indicate that temperature and relative humidity data intended for use in studies relating climatic factors and fungus activity should be measured as close to the site of interaction as possible.
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