Respiration by unprocessed pine logs creates a severe hypoxic and hypercapnic atmosphere in enclosed spaces

Abstract

Wood products, particularly whole, unprocessed logs, are a significant risk pathway for forest insect pests. Freshly harvested logs continue to respire, creating a high carbon dioxide (CO2), and low oxygen (O2) atmosphere in enclosed spaces. Such modified atmospheres may reduce the effectiveness of insect control treatments applied during the transit of logs, making it important to accurately quantify how the atmosphere is modified. We used gas chromatography to measure the amount of CO2 and O2 respired by radiata pine (Pinus radiata D.Don) logs under three temperatures (10, 15 and 20 °C) in airtight containers for 14 days to simulate real world conditions in a ship’s hold. We repeated the experiment across all seasons (i.e. spring, summer, autumn and winter). The atmosphere in the containers became severely hypoxic/hypercapnic (low O2/high CO2) by day five, and our study confirmed that temperature, time and season were significant factors influencing log respiration. Our results suggest that the atmosphere in a ship’s hold during the export of unprocessed wood products changes rapidly to hypoxic/hypercapnic conditions that are then maintained for weeks. This highlights a potential challenge for the effectiveness of insect control treatments during transit of logs, particularly treatments that require respiratory uptake of a toxin by insects.