%0 Journal Article
%T Mapping Agricultural Frozen Soil on the Watershed Scale Using Remote Sensing Data
%A Jalal Khaldoune
%A Eric Van Bochove
%A Monique Bernier
%A Michel C. Nolin
%J Applied and Environmental Soil Science
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/193237
%X This paper presents an empirical model for classifying frozen/unfrozen soils in the entire Bras d¡¯Henri River watershed (167£¿km2) near Quebec City (Quebec, Canada). It was developed to produce frozen soil maps under snow cover using RADARSAT-1 fine mode images and in situ data during three winters. Twelve RADARSAT-1 images were analyzed from fall 2003 to spring 2006 to discern the intra- and interannual variability of frozen soil characteristics. Regression models were developed for each soil group (parent material-drainage-soil type) and land cover to establish a threshold for frozen soil from the backscattering coefficients (HH polarization). Tilled fields showed higher backscattering signal (+3£¿dB) than the untilled fields. The overall classification accuracy was 87% for frozen soils and 94% for unfrozen soils. With respect to land use, that is, tilled versus untilled fields, an overall accuracy of 89% was obtained for the tilled fields and 92% for the untilled fields. Results show that this new mapping approach using RADARSAT-1 images can provide estimates of surface soil status (frozen/unfrozen) at the watershed scale in agricultural areas. 1. Introduction Soil freezing is a critical attribute for sustaining agricultural production. It has a major impact on soil water erosion at snowmelt [1, 2] and causes winterkill of perennial crops [3]. Soil water erosion and surface runoff are major sources for transporting water from agricultural land to streams. Soil sediments adversely affect surface water quality and often carry phosphorus, ammonia, pathogens, trace elements, and other contaminants from agricultural sources [4]. In Eastern Canada, the extent of this diffuse pollution is exacerbated when significant snowmelt runoff occurs on bare and erodible frozen agricultural soils located on sloping fields [5]. Environmental conditions in spring can significantly affect water transport. Early snow accumulation on wet soils may result in more unfrozen soils [6], or shallowly frozen soils, that allow higher infiltration of water at spring melt which consequently decreases runoff [7, 8]. Late snow accumulation on relatively dry soils with cold air temperatures will allow frost to penetrate deeper below the soil surface. Soils frozen below a 15-cm depth can impede water infiltration [9] and generate a greater risk of erosion and snowmelt runoff at spring thaw. Despite the environmental impacts of frozen soils, soil temperature is poorly documented in Canada; agricultural lands are not systematically monitored by meteorological stations. Clearly, soil
%U http://www.hindawi.com/journals/aess/2011/193237/