. 2002. Temporal trends in soil properties at a soil quality benchmark site in the Lower Fraser Valley, British Columbia. Can. J. Soil Sci. 82: 499-509. A national soil quality monitoring program was established in 1990 to address concerns that the quality of Canada's agricultural soils was in decline. The British Columbia benchmark site (01-BC) was established in 1991 and is located on the Pelly soil series (Orthic Humic Gleysol) supporting a corn-forage-pasture rotation in the Lower Mainland ecoregion. The objectives of this study were to report on the differences in: (1) the measured soil properties for the 5-yr period between baseline data collection in 1991 and resampling in 1996 and (2) the properties measured annually as indicators of soil compaction. A 25-m × 25-m grid was used at the site to locate sampling points for bulk density and collecting soil samples of the Ap, BCg, and Cg horizons, as well as the measurement locations for saturated hydraulic conductivity and penetration resistance. A 5-yr interval sampling regime was used to sample the Ap, BCg, and Cg horizons and bulk density. Saturated hydraulic conductivity and penetration resistance were sampled annually from 1992 to 1998. Between 1991 and 1996 in the A horizons, pH, available P, C:N ratio and bulk density increased by 4.6, 7.8, 2.5, and 8%, respectively, and available K, total C and total N decreased by 21, 16.5, and 18.3%, respectively. In the BCg horizon, pH, available P and C:N ratio increased by 5, 126, and 8%, respectively, and the available K and total N both decreased by 21%. Bulk density remained unchanged. The assumption that the soil chemical properties in the Cg horizon would remain stable during the study period did not hold. The trends detected for the Cg horizon were similar to those measured for the upper two horizons. However, only the reductions in available K and total N and increases in C:N were significant. The changes in the soil physical properties measured at this site indicate that some soil compaction has occurred. Both bulk density at 20 cm and penetration resistance increased at all depths between 1994 and 1998, which coincided with the time period that grazing was included in the crop rotation. Field saturated hydraulic conductivity at 25 cm (Ap2 horizon), although highly variable from year to year also tended to be lower during the pasture rotation. The penetration resistance measurements, which detected changes at all depths, appeared to be a more sensitive indicator of soil compaction than either bulk density or field saturated hydraulic conductivity.Key words: Soil quality, soil monitoring, soil properties, soil compaction, temporal change Kenney, E. A., Hall, J. W. et Wang, C. 2002. Évolution des propriétés pédologiques dans le temps à un site de contrôle de la qualité du sol dans la basse vallée du Fraser, en Colombie-Britannique. Can. J. Soil Sci. 82: 499-509. Face à la crainte d'une détérioration des sols agricoles au Canada, un programme national de contrôle de la qualité voyait le jour en 1990. L'année...
The land suitability rating system (LSRS) is a spatial modeling tool that generates a class rating for parcels of land for specific agricultural crops based on a soil-climate-landscape potential. We applied the LSRS module for corn suitability to the agricultural portion of the lower Fraser Valley of British Columbia (BC). We used data from six UN-IPCC AR4 projections covering a range of cold to hot and wet to dry scenarios for the time periods 2010-2039, 2040-2069, and 2070-2099 to assess the impacts of climate change on corn production. To obtain satisfactory spatial results, we linked high-resolution (400 m grid) monthly temperature and precipitation values to the individual polygons of a detailed (1 : 25 000 scale) soil map available for the study area. Of the six future climate scenarios evaluated, the Goddard Institute for Space Studies (GISS_EH-A1B/3) yielded the most favourable results whereby land suitability for corn without irrigation remained relatively stable through the 21st century. Conversely, the Hadley Centre Global Environmental Model (HadGEM-A1B/1) projected a large drop in land suitabililty for corn due to increased climatic and soil moisture deficits. The wide range of climate scenario inputs generated a similarly wide range of LSRS ratings. Most scenarios generated positive impacts for land suitability up to mid-century but negative impacts by late century. Overall, increased heat and aridity will produce earlier harvest dates for corn and likely mean significant changes to the types and timing of crop management practices in the region.Key words: land suitability, soil mapping, climate change.Résumé : Le Système de classification des terres selon leurs aptitudes pour les cultures (SCTAC) est un outil de modélisation spatiale permettant de classer les parcelles en fonction des cultures qu'elles peuvent supporter, compte tenu du type de sol, du climat et du relief. Les auteurs ont appliqué le module du SCTAC pour la culture du maïs à la zone agricole de la basse vallée du Fraser, en Colombie-Britannique. À cette fin, ils ont utilisé les données de six projections UN-IPCC AR4 couvrant une gamme de conditions allant de froid à chaud et d'humide à sec pour les périodes 2010-2039, 2040-2069 et 2070-2099. L'objectif était d'évaluer les répercussions du changement climatique sur la production du maïs. Pour obtenir des résultats spatiaux satisfaisants, les auteurs ont associé les valeurs mensuelles à haute résolution (mailles de 400 m) de la température et des précipitations à chaque polygone d'une carte détaillée (échelle 1 : 25 000) des sols de la région examinée. Parmi les six scénarios climatiques évalués, c'est celui du Goddard Institute for Space Studies (GISS_EH-A1B/3) qui restitue les résultats les plus favorables, à savoir un sol qui se prête relativement bien à une culture stable du maïs, même sans irrigation, durant tout le 21 e siècle. Le Hadley Centre Global Environmental Model (HadGEM-A1B/1), en revanche, prévoit une nette baisse des aptitudes du sol pour cette culture, en...
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