Bat activity is low in thinned and unthinned stands of red pine
We investigated the use of red pine (Pinus resinosa Ait.) plantations by bats in the Manistee National Forest of Michigan. Using ultrasonic detectors, we compared the activity of bats in the interior of stands of red pine and in openings within the stands, both before and after thinning (mean time after thinning = 7 years). Bat activity was more than 20 times greater in small openings within thinned and unthinned stands than within the stands themselves, and bat activity was associated with greater insect abundance in openings. Thinning lead to a significant change in structural complexity, as shown by a 39% decrease in basal area and a 45% decline in tree density, although these changes did not lead to an increase in use of red pine stands by bats. Red pine plantations, even after thinning, most likely are too structurally complex and have low insect abundance, making them a largely unsuitable habitat for bats.