Below ground CO2 efflux from cut blocks of varying ages in sub-boreal British Columbia

Abstract

Instantaneous measures of below ground CO2 fluxes were made in a mature stand and seven vegetated cut blocks 0, 2, 3, 5, 6, 9 and 10 years after harvest in sub-boreal forests of Central British Columbia, Canada from May to October, 2000. All cut blocks were replanted to hybrid spruce (Picea glauca x engelmannii) within 2 years of harvest and the natural vegetation on site was unmanaged. Instantaneous measures of soil temperature and moisture (each cut block) and continuous measures of soil temperature (one cut block) were made and later used in regression equations to predict below ground CO2 fluxes from 24 May to 20 September 2000. Instantaneous below ground CO2 fluxes ranged from between 2 μmol C m-2 s-1 in the Spring and highs of 10 μmol C m-2 s-1 during mid-Summer. Cumulative seasonal below ground CO2 flux totals ranged between 695 and 785 g C m-2 for the cut blocks aged 3 years or older, while the 0- and 2-year-old and cut blocks produced the low (560 g C m-2) and high (861 g C m-2) CO2 flux totals, respectively. Below ground CO2 fluxes in all cut blocks were positively correlated with soil temperature and the amount of biomass present on site. Only a few cut blocks demonstrated a significant relationship between soil moisture and instantaneous below ground CO2 fluxes. Conversely, a positive correlation was not found between mean soil temperature and cumulative below ground CO2 flux at all sites. The lack of correlation may indicate that soil temperature is not the main factor controlling below ground CO2 flux as cut blocks age. © 2002 Elsevier Science B.V. All rights reserved.