干旱区生态环境知识资源中心

Hyperspectral imagery is used to map the various indicators of dryland salinity at Dicks Creek, a site in the Yass River catchment of New South Wales. These indicators include salt-source debris-flow deposits, degraded soil profiles, halophytic grasses and a closely associated drainage line community of grasses and reeds. No diagnostic evaporite minerals can be recognized but the high spectral resolution of HyMap allows non-saline fallow soils, rock outcrops and saline soils to be differentiated from one another. Mineral analysis using field spectrometry and X-Ray Diffraction (XRD) techniques confirms the likely presence of an aeolian, smectite day, component in certain horizons of the soil profile. This distinctive yellow clay allows these soils to be separately mapped with HyMap imagery. The soils within the region are considered to be combinations of the normal weathering products of the basement rocks and a salt-enhanced windblown dust that accumulated during cold and arid glacial periods. The soils have subsequently been redistributed from the valley sides to the valley floors as debris-flows. Integration of hyperspectral image products with a digital terrain model allows for the recognition of a close association of saline seeps with major geological structures. These structures include master joints, faults, rock unit boundaries and major quartz veins. A mechanism for salinity discharge is proposed which involves the elevation of water tables following land clearing; the interaction of non-saline groundwater with the salt-enhanced aeolian soils and finally the focusing of saline waters through preferred geological structures. An integrated approach for mapping and prediction of soil salinity using digital terrain data, hyperspectral imagery, radiometric and magnetic imagery is proposed.