Limited direct effects of a massive wildfire on its sagebrush steppe bee community
2016
LOVE, BYRON G. | CANE, JAMES H.
1. Fire can affect bees directly through exposure to heat and smoke. Direct effects include mortality, injury, and displacement affecting at most two generations – adults and any immature progeny present during the fire. To study the direct effects of fire on bees, two criteria must be met. First, bees must be sampled soon after the fire event, before colonists arrive from outside the burn. Second, sampling locations must be far enough into the burned habitat to ensure that bees observed are survivors, and not foragers nesting outside the burn. 2. Bees were systematically sampled far inside (>7 km) and outside the burn perimeter immediately following a massive wildfire that burned primarily at night in sagebrush steppe habitat. Because adult females sleep in their nests, it was hypothesised that females of species with nests >10 cm underground would be safe from lethal heat, whereas females with shallow or above‐ground nests would be vulnerable. It was also hypothesised that fire would kill proportionately more males, as they typically sleep above ground. 3. Adult bees were present at all burned sample sites 14 and 21 days after the fire started. Many females were observed transporting pollen, indicative of active nest provisioning. Among the guild of bees surveyed at wild sunflowers (the only surviving flowering plant), fewer species were active within the burn. Guild composition was significantly altered, particularly by loss or depletion of several (but not all) sunflower specialists. Sex ratios did not shift, possibly due to surviving males aggregating in remaining patches of sunflowers.
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