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Lake Powell retains most of the phosphorus that it receives, leading to downstream phosphorus limitation. These data were compiled to examine controls on phosphorus cycling below Lake Powell in the Colorado River and from storm inputs from the Paria River. Objectives of our study were to determine how several forms of phosphorus, both organic and inorganic, were cycled under varying dissolved oxygen concentrations and pH, reflecting the range of values observed in the river over the years. These data represent nitrogen, phosphorus, calcium, and carbon concentrations, water quality parameters (pH, dissolved oxygen, temperature), sediment composition, total protein, and extracellular enzyme activity (alkaline phosphatase)....
Categories: Data; Tags: Aquatic Biology, Arizona, Colorado River, Ecology, Geochemistry, All tags...
In arid ecosystems, abiotic processes facilitate the physical and chemical degradation of plant litter to the extent that decomposition models that use climatic and litter composition variables as surrogates for microbial activity are not predictive. The purpose of this study was to estimate the potential contribution of photodegradation to the decomposition of plant litters that varies in architecture and chemical composition. Litter of Pinus edulis, Juniperus monosperma and Populus deltoides were exposed to ambient and attenuated sunlight, with and without supplemental water additions, at a riparian forest site along the Middle Rio Grande (New Mexico, USA). Mass loss, elemental composition, and microbial extracellular...
Current soil enzyme methods measure potential enzyme activities, which are indicative of overall enzyme concentrations. However, they do not provide insight in the actual rates of enzymatically catalyzed reactions under natural in situ conditions. The objectives of this review are to (1) clarify what is being measured by current standard soil enzymology methods; (2) present an overview of the factors that control in situ activities of soil enzymes; and (3) evaluate how emerging technologies and modeling approaches could enhance our understanding of in situ extracellular enzyme activity (EEA). Genomic studies targeting functional genes coding for extracellular enzymes can identify the genetic potential of microbial...
Plant roots and soil microorganisms contain significant quantities of low molecular weight (MW) phosphorylated nucleosides and sugars. Consequently, upon death these can represent a significant input of organic-P to the soil. Some of these organic-P substrates must first be dephosphorylated by phosphatases before being assimilated by the soil microbial community while others can be taken up directly from soil solution. To determine whether sorption or phosphatase activity was limiting the bioavailability of low MW organic-P in soil we compared the microbial uptake and C mineralization of a range of 14C-labeled organic-P substrates [glucose-6-phosphate, adenosine monophosphate (AMP), adenosine diphosphate (ADP) and...
In arid ecosystems, as much as 75% of solar radiation that penetrates the atmosphere hits the surface of the soil. The combination of high irradiance, high temperature, and low moisture puts constraints on the activity and organization of microbial communities. To separate the direct effects of UV absorbance on litter decomposition from the indirect effects of microbial selection, we placed mixed cohorts of senescent pi�on (Pinus edulis) and juniper (Juniperus monosperma) litter into triplicate microcosms assigned to four treatments: UV irradiated (0.6 mW/cm2 UV-A and UV-B for 12 h/day), with and without water additions, and non-irradiated with and without water additions. After 26 weeks, mass loss rates did not...
    map background search result map search result map Phosphorus, nitrogen, carbon, calcium, pH, and dissolved oxygen data from incubations of Colorado River water and sediment and associated ambient river water measurements Phosphorus, nitrogen, carbon, calcium, pH, and dissolved oxygen data from incubations of Colorado River water and sediment and associated ambient river water measurements