Short communication Short-term temporal changes in the spatial variability model of CO 2 emissions from a Brazilian bare soil N. La Scala Jr.*, J. Marques Jr., G.T. Pereira, J.E. Cora FCAV-UNESP, Via de Acesso Prof. Paulo Donato Castellane s/n. 14870-000, Jaboticabal, SP, Brazil Received 6 September 1999; received in revised form 5 January 2000; accepted 23 February 2000 Abstract In this work, the spatial variability model of CO 2 emissions and soil properties of a Brazilian bare soil were investigated. Carbon dioxide emissions were measured on three dierent days at contrasted soil temperature and soil moisture conditions, and soil properties were investigated at the same points where emissions were measured. One spatial variability model of soil CO 2 emissions was found for each measurement day, and these models are similar to the ones of soil properties studied in an area of 100  100 m. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Soil CO 2 emission; Soil properties; Spatial variability The study of soil CO 2 emissions is a relevant task due to the fact that it is related to many environmental issues. In this work, we have studied the spatial varia- bility model of soil CO 2 emissions on bare soil, where microorganisms are the sole source of carbon dioxide. Studying an area of 100  100 m on three dierent days, we found average values of CO 2 emissions ran- ging from 1.26 to 2.48 mmol CO 2 m 2 s 1 (0.06±0.11 mg CO 2 m 2 s 1 ). By comparing these results with the literature, our emission values are within the same range as those reported in soils having vegetation cover (0.03±0.25 mg CO 2 m 2 s 1 ) (Fang et al., 1998; Rout and Gupta, 1989; Carlyle and Than, 1988). Also, we have found one spatial variability model of soil CO 2 emissions for each measurement day, and these models are similar to the ones of soil properties already studied. Other works in literature have also reported the complex nature of the spatial variability of soil CO 2 emissions (Fang et al., 1998; Dasselaar et al., 1998; Rochette et al., 1991). However, only a few have demonstrated short temporal changes and even fewer have compared the spatial variability patterns of CO 2 emissions with its possible controlling factors, the soil properties. The study was conducted on an acid bare oxisol (pH around 4.8) at FCAV-UNESP (21815 '220 South; 48818 '580 West) located at an altitude of 650 m, SaÄo Paulo State Ð Brazil. The climate of the area is classi- ®ed as Cwa, according to KoÈppen, subtropical with average annual temperature of 218C. The mean annual precipitation is around 1380 mm, with a rain distri- bution concentrated in the period from October to March, and a relatively dry period from April to Sep- tember. A grid containing 65 points was established on the experimental site (100  100 m) where the points were spaced at distances of 20 and 10 m. Measurements of CO 2 emissions were conducted at each point on three dierent days: 19, 25 and 27 November 1998. Soil tem- peratures at 20 cm depth were measured at each grid point using LI-6400 soil temperature probe (LI-COR, NE, USA) during the same period that CO 2 emission measurements were taken. Soil samples were obtained from 0 to 20 cm depths at each grid point on 27 November. On these 65 samples, cation exchange ca- pacity (CEC), total carbon, pH, the percentage of base Soil Biology & Biochemistry 32 (2000) 1459±1462 0038-0717/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S0038-0717(00)00051-1 www.elsevier.com/locate/soilbio * Corresponding author. Fax: +55-16-322-4275. E-mail address: lascala@fcav.unesp.br (N. La Scala Jr.).