Does Surface-applied Biochar Alter Insect Utilization of Downed Ponderosa Pine (Pinus ponderosa) Bolts?

Biochar can be used as a soil amendment to restore degraded soils, sequester carbon, and increase soil water holding capacity and plant available water following harvest operations in a forest. On-site production and utilization of biochar is being explored as a forest management tactic. One benefit of the practice is the sequestration of carbon by using unmerchantable forest biomass to produce biochar. Forest insects may be exposed to biochar when the material is applied to surface organic horizons and downed trees. How biochar affects insects' ability to locate and utilize downed woody material in the forest is undetermined. Two field experiments with freshly downed sections (bolts) of ponderosa pine (Pinus ponderosa Lawson & C. Lawson) were conducted to determine the potential impact of applied biochar on insect communities utilizing the bolts. In the first experiment, bolts were baited with a pheromone lure and biochar was applied at a rate equivalent to 2,914 kg·ha-1 (1.30 tons·acre-1). The biochar treatment did not interfere with attack or emergence of the pine engraver Ips pini (Say) (Coleoptera: Curculionidae: Scolytinae) compared to untreated control bolts. In the second experiment, biochar applied at a rate equivalent to 5,604 kg·ha-1 (2.50 tons·acre-1) lowered insect species richness compared to non-treated bolts. In addition, one species, red turpentine beetle Dendroctonous valens (LeConte) (Coleoptera: Curculionidae: Scolytinae), was more abundant in non-treated bolts compared with biochar-treated bolts. Utilization of bolts by other insect taxa such as longhorn beetles (Coleoptera: Cerambycidae) was similar in non-treated and biochar-treated bolts.