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Historically, ecosystems in the southwestern United States derived much of their nitrogen (N) from N-fixation in biological soil crusts. Today, these regions have highly reduced crust cover, and atmospheric deposition may be the dominant source of N. This study investigates the effects of increased nitrogen deposition on nitrogen uptake, photosynthesis, and growth of the two main forage grasses on the Colorado Plateau, galleta (Hilaria jamesii [Torr.] Benth.) and Indian ricegrass (Oryzopsis hymenoides, [Roemer & J.S. Schultes] Ricker ex Piper). Plots were fertilized for 2 years with 0, 10, 20, and 40 kg nitrogen ha?1 annually, up to 4� the estimated current annual deposition rate, in 2 applications per year (spring...
A recently proposed meaning of pedoderm is more formally defined so as to contrast it with an older definition that is used infrequently in soil stratigraphy. It is defined here as the thin layer of soil at the interface with the atmosphere, a few millimetres to centimetres thick, within which certain properties may exhibit a marked vertical change in expression sometimes not readily detected through field observation. The function of this generic term is primarily to draw attention to the variation of soil surface characteristics on a micro-scale that might otherwise be overlooked. It has implications for understanding material fluxes and ecosystem function and the use of remote sensing for soil evaluation. Published...
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The Colorado Plateau is located in the interior, dry end of two moisture trajectories coming from opposite directions, which have made this region a target for unusual climate fluctuations. A multi-decadal drought event some 850 years ago may have eliminated maize cultivation by the first human settlers of the Colorado Plateau, the Fremont and Anasazi people, and contributed to the abandonment of their settlements. Even today, ranching and farming are vulnerable to drought and struggle to persist. The recent use of the Colorado Plateau primarily as rangeland has made this region less tolerant to drought due to unprecedented levels of surface disturbances that destroy biological crusts, reduce soil carbon and nitrogen...


    map background search result map search result map Effects of Nitrogen Deposition on an Arid Grassland in the Colorado Plateau Cold Desert Sensitivity of the Colorado Plateau to Change: Climate, Ecosystems, and Society Effects of Nitrogen Deposition on an Arid Grassland in the Colorado Plateau Cold Desert Sensitivity of the Colorado Plateau to Change: Climate, Ecosystems, and Society