Controls of Bedrock Geochemistry on Soil and Plant Nutrients in Southeastern Utah |
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Authors: | J C Neff R Reynolds R L Sanford Jr D Fernandez P Lamothe |
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Institution: | (1) Geological Sciences and Environmental Studies, University of Colorado at Boulder, CB 399, Boulder, Colorado 80309, USA;(2) U.S. Geological Survey, ms 980, Denver Federal Center, Denver, Colorado 80225, USA;(3) Biological Sciences Department, University of Denver, Denver, Colorado 80208, USA |
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Abstract: | The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types.
In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to
the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine
environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation
is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic
settings, appears closely related to variation of CaCO3 and Ca-phosphates in soils. However, the results of this study also indicate that P content is related to bedrock and soil
Fe and Al content suggesting that the deposition history of the bedrock and the presence of P-bearing Fe and Al minerals,
is important to contemporary P cycling in this region. The relation between bedrock type and exchangeable Mg and K is less
clear-cut, despite large variation in bedrock concentrations of these elements. We examined soil nutrient concentrations and
foliar nutrient concentration of grasses, shrubs, conifers, and forbs in four geochemically distinct field sites. All four
of the functional plant groups had similar proportional responses to variation in soil nutrient availability despite large
absolute differences in foliar nutrient concentrations and stoichiometry across species. Foliar P concentration (normalized
to N) in particular showed relatively small variation across different geochemical settings despite large variation in soil
P availability in these study sites. The limited foliar variation in bedrock-derived nutrients suggests that the dominant
plant species in this dryland setting have a remarkably strong capacity to maintain foliar chemistry ratios despite large
underlying differences in soil nutrient availability. |
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Keywords: | desert nutrient soil foliar stoichiometry bedrock |
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