http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Characterization and erosion of andisols in Iceland
xiii, 179 leaves : illustrations ; 29 cm
The objectives of the research were to investigate eolian-andic soils in Iceland that are highly susceptible to soil erosion and characterize processes and soil properties that influence erosion with emphasis on wind. Four eolian-andic soils that formed in 1-3 m of tephra and eolian materials of various origin were studied. The soils have low bulk density (<0.7 g cm⁻³) and high 0.033 and 1.5-MPa water retention (27-118% and 17-85%, respectively, excluding tephra horizons). Soil reaction (H₂0) ranges between 5.6 and 6.7. Organic carbon contents are high but erratic; they range from 2.1-9.0% for eolian andic materials and 0.1-1.2% for weathered till materials. High ammonium oxalate extractable Al0, Fe0, and Si0 reflect clay composition dominated by allophane and ferrihydrate. Clay contents are strongly dependent on parent sediments and range from 15-50%. The CEC is generally high (22-46 cmol(subscript c) kg⁻¹) and is highly related to OC, Al(subscript O), Fe (subscript O)and 1.5-MPa water retention. The soils were classified as Typic Haplocryands, Typic Vitricryands and Vitric Haplocryands. Two pedons forming in glacial till were classified as Typic Vitricryands and have the same family classification as one of the highly contrasting eolian-andic soils. Icelandic soils have been subjected to severe degradation with loss of 35,000 km2 of vegetated areas. Total removal of the eolian-andic mantle characterizes erosion in Iceland. A classification of erosion forms is presented. Two forms dominate: erosion escarpment and advancing front. Escarpments develop because plant roots near the surface provide cohesion while less cohesive, underlying eolian-andic materials become undermined. Advancing fronts are the result of wind erosion when ample materials are available for saltation. Tongues of saltating materials move across and cover vegetated areas leaving barren surfaces behind. Soils most susceptible to wind erosion are dominated by sand-sized aggregates and tephra grains. Wind tunnel experiments indicate low threshold velocities for relatively coarse (>0.5 mm) tephra and aggregates. Heavy liquid separation suggests that the apparent density of porous tephra grains and aggregates ranges between 0.9 and 1.3 g cm⁻³. The research shows that aggregates are weak in areas where wind erosion is not widespread while strong, coarse tephra grains increase soil susceptibility to wind erosion.