Butterfly response to microclimatic conditions following ponderosa pine restoration

Efforts to restore ponderosa pine ecosystems to open, park-like conditions that predominated prior to European-American settlement result in altered stand structure and increased landscape heterogeneity, potentially altering habitat suitability for invertebrates and other forest organisms. We examined the responses of two butterfly species, Colias eurytheme and Neophasia menapia, to microclimatic changes at structural edges created by experimental restoration treatments in northern Arizona. We monitores microclimate, including air temperature, light intensity, and vapor pressure deficit (VPD), on several mornings during butterfly releases. We placed adult butterflies at east- and west-facing edges approximately one half-hour before dawn to determine their behavioral response to microclimatic differences between east- and west-facing edges. After sunrise, all three microclimatic variables were higher at east-facing edges, and the differences in microclimate between the two edge orientations increased through early morning. For both species, butterflies placed at east-facing edges flew earlier than butterflies at west-facing edges. Colias eurytheme, an open-habitat species, tended to move toward the treated forest during initial flight, while movements of Neophasia menapia, a forest-dwelling species, did not differ from random flight. Our results indicate that butterflies respond to microclimatic factors associated with restoration treatments, while responses to structural changes in habitat vary among species, based on habitat and food plant preferences. These changes in forest structure and microclimate may affect the distribution of many mobile invertebrates in forested landscapes undergoing restoration treatments.