Seasonal comparison of soil temperature and moisture in pits and mounds under vine maple gaps and conifer canopy in a coastal western hemlock forest

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In this study we attempted to determine if vine maple priority gaps show similar trends in temperature and moisture status to those reported in the literature for treefall gaps and whether temperature and moisture status differed between microtopographic positions (pits and mounds). Biweekly measurements of mid-day soil and air temperature, moisture contents at 30-, 50- and 80-cm depths, and depths to the groundwater table were made in pit and mound locations within six vine maple priority gaps paired with six conifer canopy sites. Trends did not follow those found in treefall gaps: vine maple gaps had similar mid-day temperature and moisture status to the surrounding conifer forest. Larger gaps had higher mid-day air temperatures in the summer, higher mid-day soil temperatures in the spring and summer, and greater amounts of throughfall in the spring and summer than smaller gaps. Trends in mid-day soil temperature and moisture status for pit and mound microtopography followed those reported in the literature. Pits were significantly cooler in summer and warmer in winter than mounds and pits were wetter than mounds in all seasons. This study suggests that soil microtopography has an effect on soil climate that overwhelms the influence of vine maple gaps. Key words: Vine maple, canopy gap, soil moisture, soil temperature, microtopography, pits and mounds