Insect diversity in vineyards, almond orchards, olive orchards, alfalfa fields, and pastures in the San Joaquin Valley of California

摘要

For many agricultural systems, limited data is available on abundance and diversity of insects that are not crop pests or their natural enemies. As recent studies suggest that insect abundance and diversity is declining, there is a need to quantify insect diversity within crop fields to determine what role crop fields play in maintaining diversity. In this study, alfalfa fields, almond orchards, vineyards, olive orchards, and pastures located in the San Joaquin Valley of California were sampled. Ground sweep samples were collected from all five habitats. In addition, foliar beat samples were collected from almond orchards, vineyards, and olive orchards. In total, similar to 240,000 arthropods were collected with the majority identified to family. Across crops and sampling methods, 20 arthropod orders and 202 insect families were observed. Hemiptera was the most abundant order of insect collected, representing an average of 61% of all arthropods collected. Diptera was the most diverse order of insect collected, with a total of 59 dipteran families observed across crops. Of the 202 insect families observed, 85 were observed in all 5 habitats (42%), whereas 48 families were observed in only one habitat (24%). Families observed in a single habitat were often represented by only a few individuals. Principal component analysis indicated that the communities present in the understory of vine and tree crops were more similar to each other than to the communities observed in pastures or alfalfa fields. Much of the total insect biomass belonged to a few families that included known agricultural pests. In contrast, most of the diversity was made up of families present in low to moderate abundance.