RESUMO
Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope, and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.
RESUMO
Baseline values and ranges for 10 hematologic and 32 plasma chemistry parameters were analyzed for 36 free-ranging Sonoran desert tortoises (Gopherus agassizzi) collected in Yavapai and La Paz Counties (Arizona, USA) from 1990 to 1995. Tortoises were radio tagged from 1990 to 1994, and attempts were made to recapture them three times a year. Tortoises were weighed, measured, and chemically immobilized to collect blood for hematology and blood chemistry assessments. Tortoise biochemistry differed (P < 0.01) between sites and sexes and among seasons and years. Normal reference ranges for hematologic and plasma biochemistry parameters were determined. Seasonal and annual differences in hematology and blood chemistry were related to rainfall patterns, forage availability, and physiological condition.
