- E. Jong de (1)
- F. Jongbloed (1)
- S. Li (1)
- D.A. Lobb (1)
- R.A. MacMillan (1)
- B.G. McConkey (1)
- R.J. Meijer de (1)
- A. Moulin (1)
- D. Pennock (1)
- J.M. Schoorl (1)
- A. Uijl (1)
- A. Veldkamp (1)
- T. Yates (1)
Extracting topographic characteristics of landforms typical of Canadian agricultural landscapes for agri-environmental modeling. I. Methodology
Li, S. ; Lobb, D.A. ; McConkey, B.G. ; MacMillan, R.A. ; Moulin, A. ; Fraser, W.R. - \ 2011
Canadian Journal of Soil Science 91 (2011)2. - ISSN 0008-4271 - p. 251 - 266.
fuzzy-logic - classification - saskatchewan - terrain - erosion
Soil and topographic information are key inputs for many agri-environmental models and there are linkages between soil and topography at the Field scale. A major source of soil data is soil databases established based on field soil survey. Although both soil and topographic information are recorded in field soil surveys, the nominal nature of the topographic data has limited their use in agri-environmental models. in this study, we developed a methodology to extract various topographic derivatives and to classify the landscape into landform elements with distinctive topographic characteristics based on detailed analyses of fine resolution digital elevation models. Data obtained from these analyses were used to calculate a representative two-dimensional hillslope of five segments, each with a defined length and slope gradient. A set of modal hillslopes was developed to describe topographic variability. Additional topographic parameters, ratios and indices were calculated to reflect different aspects of topographic characteristics and also to build connections between different agri-environmental models. in particular, a topographic complexity index was developed as a quantitative measure of the degrees of divergence and convergence. This paper describes the methodology using one site as an example. Application of this methodology to other landforms in agricultural land of Canada is reported in a companion paper
The effects of erosional and management history on soil organic carbon stores in ephemeral wetlands of hummocky agricultural landscapes
Bedard-Haughn, A. ; Jongbloed, F. ; Akkennan, J. ; Uijl, A. ; Jong, E. de; Yates, T. ; Pennock, D. - \ 2006
Geoderma 135 (2006). - ISSN 0016-7061 - p. 296 - 306.
landform segmentation procedures - morainal landscape - saskatchewan - cultivation - deposition - storage - impact - redistribution - vegetation - canada
Carbon sequestration by agricultural soils has been widely promoted as a means of mitigating greenhouse gas emissions. In many regions agricultural fields are just one component of a complex landscape matrix and understanding the interactions between agricultural fields and other landscape components such as wetlands is crucial for comprehensive, whole-landscape accounting of soil organic carbon (SOC) change. Our objective was to assess the effects of management and erosional history on SOC storage in wetlands of a typical hummocky agricultural landscape in southern Saskatchewan. Wetlands were classed into three land management groups: native wetlands (i.e., within a native landscape), and uncultivated and cultivated wetlands within an agricultural landscape. Detailed topographic surveys were used to develop a digital elevation model of the sites and landform segmentation algorithms were used to delineate the topographic data into landform elements. SOC density to 45 cm was assessed at seven uncultivated wetlands, seven cultivated wetlands, and twelve native wetlands. Mean SOC density decreased from 175.1 mg ha¿ 1 to 30 cm (equivalent mass depth) for the native wetlands to 168.6 mg ha¿ 1 for the uncultivated wetlands and 87.2 mg ha¿ 1 for the cultivated wetlands in the agricultural field. The SOC density of sediment depositional fans in the uncultivated wetlands is high but the total SOC stored in the fans is low due to their small area. The uncultivated wetlands occupy only 11% of the site but account for approximately 23% of SOC stores. Re-establishing permanent vegetation in the cultivated wetlands could provide maximum C sequestration with minimum energy inputs and a minimum loss of productive acreage but the overall consequences for the gas emissions would have to be carefully assessed.
The 137Cs technique applied to steep Mediterranean slopes (Part I): the effects of lithology, slope morphology and land use
Schoorl, J.M. ; Boix Fayos, C. ; Meijer, R.J. de; Graaff, E.R. van der; Veldkamp, A. - \ 2004
Catena 57 (2004)1. - ISSN 0341-8162 - p. 15 - 34.
soil-erosion rates - cesium-137 measurements - natural radionuclides - drainage-basin - redistribution - saskatchewan - indicators - landscape - tillage - canada
Concentrations in the soil of anthropogenic and natural radionuclides have been investigated in order to assess the applicability of the Cs-137 technique in an area of typical Mediterranean steep slopes. This technique can be used to estimate net soil redistribution rates but its potential in areas with shallow and stony soils on hard rock lithology have not been evaluated so far. In this research, the validity of using this technique in stony shallow soils at very steep slopes is discussed together with the relations between radionuclide concentrations and other soil properties, lithology, slope morphology and land use in a Mediterranean environment. Both natural Potassium-40 (4 K), Uranium-238 (U-238), Thorium-232 (Th-212) and anthropogenic Caesium-137 (Cs-137) radionuclides have been determined in samples taken along slope transects on uncultivated serpentinite soils and cultivated gneiss soils. In addition to the radionuclide concentrations, parameters such as slope position, slope angle, aspect, soil depth, surface stone cover, moss, litter, vegetation cover, soil crust, stone content and bulk density have been quantified. All the natural radionuclides K-40, U-238, Th-232 show significantly higher concentrations in the gneiss than in the serpentinite soils, opposed to the Cs-137 concentration, which is found significantly higher in the serpentinite soils probably because of the difference in clay mineralogy. The exponential decreasing depth distribution of Cs-137 and its homogeneous spatial distribution emphasise the applicability of the Cs-137 technique in this ecosystem. Lithology determines the concentration of natural and anthropogenic radionuclides. Land use determines the relations between Cs-137 concentration/inventory and some soil characteristics. Higher Cs-137 concentration and inventory are associated with higher percentages of vegetation cover, higher percentage of stones in the soil and higher values of soil bulk density in cultivated gneiss soils. Slope morphology and land use influence the soil redistribution at slope, scale. The gneiss slopes show a zonation of four to five areas of differential erosion/accumulation processes corresponding with more regular slopes and soil redistribution due to water erosion and to tillage translocation and erosion. The serpentinites, as an example of a more unstable slope type, show more erosion areas with less accumulation downslope and soil redistribution due to water erosion. (C) 2003 Elsevier B.V. All rights reserved.