Patterns of aerial arthropod biomass and diversity from three regions of boreal Alaska

Abstract

Abstract Multi‐decadal monitoring has revealed dramatic evidence of global decline in arthropod biomass and biodiversity, yet little baseline information exists for Alaska, a region 1/5th the size of the contiguous US states. We documented patterns of aerial arthropod biomass and diversity in a multi‐year investigation of three regions in boreal Alaska—two in central Alaska (Fairbanks and Tetlin) and one in southcentral Alaska (Anchorage). Sampling employed canopy Malaise and near‐ground pollinator traps as part of a parallel study of a steeply declining songbird. Traps yielded 115,078 specimens of 15 orders and 692 unique taxa with body sizes ≥3 mm. During peak summer (15 June–15 July), mean aerial arthropod biomass was more than three times higher in traps in Fairbanks (50.6 mg·d−1, confidence interval [CI]: 34.5–63.7) than Anchorage (15.8 mg·d−1, CI: 9.3–26.4). Tetlin exhibited an intermediate value (35.4 mg·d−1, CI: 18.4–67.4). Temperature correlated positively with captured biomass, whereas wind (above 1.5 m·s−1) correlated negatively. To obtain species‐level diversity data, we focused on beetles, representing a wide range of feeding guilds and taxa. Beetles accounted for 6229 adult specimens, 364 unique (mostly species‐level) taxa and 47 families. Trophic categorizations of beetles were similar for the central Alaskan sites; both had a greater proportion of wood‐feeding beetles than Anchorage. Ten species are potentially new to science and 49 are new state records for Alaska. Our work provides the first insight into regional differences and seasonal trends in aerial arthropod biomass and diversity in boreal Alaska, creating important baselines for the future.