Abiotic conditions are important determinants of insect biomass, which should vary predictably across macroecological gradients of temperature, precipitation, and productivity. Previous studies have focused on biomass within a taxonomic group, or within specific habitat such as forests or grasslands. However, the manner in which insect biomass varies in the aerosphere, the most universally used habitat for many insect taxa, has not yet been explored. Here, we use the national network of weather surveillance radar to map insect biomass in the air along dual axes of temperature and precipitation across the US, to identify drivers of spatial variation in biomass across biomes. Besides temperature and precipitation, we also explore how insect biomass varies with net primary productivity.
Temperature was the greatest driver of spatial patterns in insect biomass, with biomass increasing with local annual temperature. Biomass decreased at higher latitudes. While length of insect flight season decreased with latitude as well, higher daily mean biomass as well as total sum biomass indicated that increased temperature was the main driver of the latitudinal pattern. Insect biomass did not vary predictably with precipitation along our east-west precipitation gradient. Biomass was only slightly correlated with annual net primary productivity.
To our knowledge, this is the first study of the distribution of insect aerial biomass across broad abiotic gradients in the US. Identifying macroscale patterns in insect biomass aloft improves our understanding of the spatial distribution of insects, and can inform predictions of assemblage wide responses to global change.
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