Effects of a stand-replacing fire on small-mammal communities in montane forest

Abstract

Wildfire, ubiquitous and recurring over thousands of years, is the most important natural disturbance in northern coniferous forest. Accordingly, forest fires may exert a strong influence on the structure and functioning of small-mammal communities. We compared the composition of rodent and shrew communities in burned and unburned patches of a Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco) – western larch ( Larix occidentalis Nutt.) forest in western Montana, USA. Trapping was conducted during two consecutive summers after a wildfire. Four trapping sites were sampled in areas that burned at high severity and two in unburned forest. Small-mammal communities in burned sites were characterized by strong numerical dominance of deer mice ( Peromyscus maniculatus (Wagner, 1845)) and greatly reduced proportion of southern red-backed voles ( Clethrionomys gapperi (Vigors, 1830)) and red-toothed shrews (genus Sorex L., 1758). Relatively rare species such as northern flying squirrels ( Glaucomys sabrinus (Shaw, 1801)) and bushy-tailed woodrats ( Neotoma cinerea (Ord, 1815)) were largely restricted to unburned areas. The numbers of chipmunks (genus Tamias Illiger, 1811) were similar in burned and unburned areas. Rodent diversity was higher in unburned forest, but only during the 1st year after fire. Overall, the fire shifted small-mammal communities away from more specialized red-backed voles and shrews and towards greater abundance of generalist deer mice.