Response of grass species to soil salt content and coversoil depth on lands developed for coalbed methane
Mitchem, Melissa Deanne.
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In areas where land is disturbed to extract energy resources such as coalbed methane, improper soil management may result in soils impaired by elevated salinity. The objectives of this study were to evaluate the emergence and growth of three native grass species (Pseudorogeneria spicata, Hesperostipa comata, and Pascopyrum smithii) as a function of i) soil salt content and matric potential, and ii) coversoil depth overlying a saline substrate. The first study consisted of nine treatments, combining three soil salinity levels (0.80, 5.0 and 11.0 dS/m) and three matric potential ranges (-0.1 to -1.0, -1.0 to -7.0, and less than -7.0 bars). Seedling emergence, plant height, aboveground biomass, and belowground biomass were significantly decreased by increasing soil salinity and decreasing soil moisture. A correlation analysis showed matric potential to be more significantly correlated to seedling emergence and growth than soil salinity. This resulted in large reductions in growth when soil moisture was decreased within a salinity treatment. Emergence for plants grown in elevated salinity increased as much as 26.7 % when moisture was high. At low soil moisture, elevated salinity resulted in emergence losses as high as 88.3 %. Losses in aboveground biomass ranged from 23.0 to 97.9 % at moderate salinity and 27.3 to 98.5% at high salinity. Results indicate that the impacts of elevated soil salinity are highly influenced by soil moisture. Irrigation will be an important factor in revegetation of saline soils. Also, investigators studying plant growth on saline soils must closely consider the impact of soil moisture on study results. For the second study, a substrate consisting of a mixture of soil and geologic stratum was salinized to an EC of 11.0 dS/m. Non-saline coversoil was applied on top of the saline substrate at depths of 0, 5, 10, 15, 30 and 45 centimeters. Aboveground and belowground biomasses were significantly greater with increased coversoil depth, with depths of 15, 30 and 45 cm producing similar results. Results suggest that coversoil is necessary to improve plant growth on a saline substrate, but applications of less than 45 cm may be adequate.