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Sanford Jr, Robert L

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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...
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...
The two main objectives of this project were to: (1) review and summarize the various interactions that can occur between invasive plants and fire, and developed management recommendations based on what is currently known; and (2) conduct new research to evaluate the specific interactions between fire, soil nutrients, and dominance by invasive annual grasses in arid and semi-arid regions of western North America. This final report for JFSP project 00-1-2- 04 explains how we accomplished these two objectives.
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Dryland ecosystems have long been considered to have a highly heterogeneous distribution of nutrients and soil biota, with greater concentrations of both in soils under plants relative to interspace soils. We examined the distribution of soil resources in two plant communities (dominated by either the shrub Coleogyne ramosissima or the grass Stipa hymenoides) at two locations. Interspace soils were covered either by early successional biological soil crusts (BSCs) or by later successional BSCs (dominated by nitrogen (N)-fixing cyanobacteria and lichens). For each of the 8 plant type�crust type�locations, we sampled the stem, dripline, and 3 interspace distances around each of 3 plants. Soil analyses revealed that...
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Biological soil crusts, composed primarily of photosynthetic cyanobacteria, algae, lichens and mosses, play a key role in many ecosystem functions of semi-arid and arid ecosystems around the world (Belnap and Lange 2001). They often cover plant interspaces in undisturbed areas (Kleiner and Harper 1972) and thus can constitute 70% or more of the living ground cover (Belnap 1995). These soil crusts are critical in the stabilization of soils and reduce both wind and water erosion (Belnap and Gillette 1997, 1998). They influence many processes that determine soil fertility, including carbon and nitrogen fixation, dust capture, and mineral chelation. They are often the dominant source of nitrogen (N) in desert ecosystems...
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