Comparison of energy fluxes between an undisturbed bog and an adjacent abandoned peatland pasture

摘要

This study compared the energy budget components of latent heat flux (LE), sensible heat flux (H), net radiation (Rn) and ground heat flux (G) between an undisturbed bog and an adjacent abandoned peatland pasture within the same peatland complex in western Newfoundland, Canada. The analysis was based on the period of April 2014 to August 2015 when measurements were concurrent at both sites, thus encompassing two growing seasons. The overall objective was to identify the impact of agricultural management and abandonment on peatland energy flux and partitioning. LE and H showed strong seasonal patterns for both sites. LE, which was higher at the pasture, peaked near the middle of the growing season. H at the bog was smaller than that at the pasture during the early growing season, but became larger during the middle and late growing seasons, with the maximum H occurring during the early growing season. G was the smallest flux in the energy budget at both sites, and it showed no obvious temporal pattern at either site. The variation in daytime average evapo-transpiration (ET) was related to net radiation and vapor pressure deficit (VPD) at both sites. However, it was more strongly related to Rn. ET at the pasture site exhibited greater sensitivity to changes in Rn and VPD. Daytime ET increased and decreased with water table depth (WTD) when WTD was above and below a threshold of -0.24 m at the bog and -0.46 m at the pasture. The between-site differences in growing season H and LE (Delta H and Delta LE) were mainly caused by their different vegetation conditions, and Delta H and Delta LE were negatively and positively related to Delta EVI (difference in enhanced vegetation index), respectively.