Influence of microclimate gradients on soil characteristics within tree-fall gaps in the Andrews Experimental Forest

Soil properties in eight, 7 year-old tree-fall gaps were compared with soils in the surrounding old-growth Douglas-fir forest. Soil characteristics were measured along two transects; one running north and south and the other east and west. This study was an extension of one done two years earlier by Shirley King (see Gap1). In that study, there were significant differences in soil properties not only between soils collected in and out of gaps but also by orientation within the gap. More specifically, soils in the north end of the larger gaps were significantly different from those in the south. This study was designed confirm the previous findings that soils within gaps were different than those in the surrounding forest. In addition, we wanted to determine if there were also E/W differences. If there were none, then we could conclude that microclimate gradients were effecting these soils because the microclimate gradient along E/W transects should be much less than that found along N/S transects. We chose to measure soil characteristics at 2-meter intervals using this same basic design used by Shirley King in the Gap1 study. E/W and N/S transects were established in all of the gaps that were studied in Gap1 with the transects extending one radius into the surrounding forest