Impacts of Biological Soil Crust Disturbance and Composition on C and N Loss from Water Erosion |
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Authors: | Nichole N Barger Jeffrey E Herrick Justin Van Zee Jayne Belnap |
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Institution: | (1) The Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO, 80523;(2) USDA – ARS Jornada Experimental Range, Las Cruces, NM, 88003;(3) USGS – BRD Canyonlands Field Station, Moab, UT, 84532;(4) Present address: Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, 1560 30th St. RL-1 220, Boulder, CO, 80309 |
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Abstract: | In this study, we conducted rainfall simulation experiments in a cool desert ecosystem to examine the role of biological soil
crust disturbance and composition on dissolved and sediment C and N losses. We compared runoff and sediment C and N losses
from intact late-successional dark cyanolichen crusts (intact) to both trampled dark crusts (trampled) and dark crusts where
the top 1 cm of the soil surface was removed (scraped). In a second experiment, we compared C and N losses in runoff and sediments
in early-successional light cyanobacterial crusts (light) to that of intact late-successional dark cyanolichen crusts (dark).
A relatively high rainfall intensity of approximately 38 mm per 10-min period was used to ensure that at least some runoff
was generated from all plots. Losses of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and ammonium (NH4+ ) were significantly higher from trampled plots as compared to scraped and intact plots. Sediment C and N losses, which made
up more than 98% of total nutrient losses in all treatments, were more than 4-fold higher from trampled plots relative to
intact plots (sediment C g/m2, intact = 0.74, trampled = 3.47; sediment N g/m2, intact = 0.06, trampled = 0.28). In light crusts, DOC loss was higher relative to dark crusts, but no differences were observed
in dissolved N. Higher sediment loss in light crusts relative to dark crusts resulted in 5-fold higher loss of sediment-bound
C and N. Total C flux (sediment + dissolved) was on the order of 0.9 and 7.9 g/m2 for dark and light crusts, respectively. Sediment N concentration in the first minutes after runoff from light crusts was
3-fold higher than the percent N of the top 1 cm of soil, suggesting that even short-term runoff events may have a high potential
for N loss due to the movement of sediments highly enriched in N. Total N loss from dark crusts was an order of magnitude
lower than light crusts (dark = 0.06 g N/m2, light = 0.63 g/m2). Overall, our results from the small plot scale (0.5 m2) suggest that C and N losses are much lower from intact late-successional cyanolichen crusts as compared to recently disturbed
or early-successional light cyanobacterial crusts. |
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Keywords: | Biological soil crust Carbon Canyonlands National Park Colorado Plateau Disturbance Erosion Nitrogen Rainfall simulation Runoff |
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