Dielectric and hydraulic response of selected forest canopies at the BOREAS test sites in Canada

Abstract

The Boreal Ecosystem-Atmosphere Study (BOREAS) is a multidisciplinary field and remote sensing study the goal of which is to obtain an improved understanding of the interactions between the boreal forest biome and the atmosphere in order to clarify their roles in global change. The two principal BOREAS field sites, both located within Canada, are located in the southern boreal ecotone, encompassing Prince Albert National Park, Saskatchewan, and in the northern boreal ecotone near Thompson, Manitoba. This paper presents a very brief synopsis of measurements that were performed at the BOREAS experiment sites to examine the dielectric and hydraulic properties of several tree species within these sites. The authors installed instrumentation designed to allow characterization of the hydraulic response of the vegetation in five stands within the BOREAS area. The five selected stands were: (1) Old Black Spruce, (2) Old Black Spruce, (3) Old Aspen, (4) Old Jack Pine and (5) Young Jack Pine. Within each stand, xylem water flux and bole temperature were monitored in several trees. Microclimate and transpiration measurements were supplemented with mid-canopy air temperature and relative humidity observations to allow calculation of mid-canopy vapor pressure deficit. Also, soil temperature was monitored at various depths to obtain temperature profiles. These measurements were obtained continuously in most of the stands throughout most of 1994. Xylem water potential was also monitored at various times throughout the season. This work has especial importance for radar remote sensing.