FINANCIAL MANAGEMENT FOR PUBLIK, HEALTH, AND NOT FOR PROFIT ORGANIZATION

xxv, 635 hlm. ; 20 x 25,5 c

Financial Management For Public Health and Not-For-Profit Organizations

vii.636 hal.; 45 c

Budgeting concepts for nurse managers

xxi, 439 hl

Financial management : for nurse managers and executives, 3rd ed./ Finkler

xxii, p. 518.: ill.; 26 c

Agriculture influences ammonium and soluble reactive phosphorus retention in South American headwater streams

Agricultural activities can affect the delivery of nutrients to streams, riparian canopy cover, and the capacity of aquatic systems to process nutrients and sediments. There are few measures of nutrient uptake and metabolism from tropical or subtropical streams in general, and even fewer from tropical regions of South America. We examined ammonium (NH₄ ⁺) and soluble reactive phosphorus (SRP) retention in streams in Brazil and Argentina. We selected 12 streams with relatively little or extensive agricultural activity and conducted whole-stream nutrient additions and measurements of gross primary production and ecosystem respiration. We used multiple linear regression to determine potential drivers of nutrient uptake metrics across the streams. Nutrient concentrations and retention differed significantly between land use categories. Both NH₄ ⁺ and SRP concentrations were higher in the agricultural sites (means of 161 and 495 μg l⁻¹, respectively), whereas metabolic rates were slower and transient storage was smaller. Our analysis indicated that agriculture increased ambient uptake lengths and decreased uptake velocities. The regression models revealed that ambient SRP had a positive effect on NH₄ ⁺ uptake and vice versa, suggesting strong stoichiometric controls. Drivers for nutrient uptake in streams with low-intensity agriculture also included canopy cover, temperature, and ecosystem respiration rates. Nutrient assimilation in agricultural sites was influenced by a higher number of variables (gross primary production for SRP, discharge, and transient storage for both nutrients). Our results indicate agricultural activity changes both the magnitude of in-stream nutrient uptake and the mechanisms that control its variation, with important implications for South American streams under agricultural intensification.Instituto de Limnología "Dr. Raúl A. Ringuelet