We studied the effects of afforestation on soil respiration (R-s) in an arid shrubland in northern Chile. We sampled R-s monthly for three years in two adjacent plots, one left as control in natural condition, and one afforested with Acacia saligna. Sampling occurred 3-6 years after afforestation. Soil temperature (T-s) was a good predictor of R-s on certain periods of the year, although we could not relate this to specific levels of soil moisture (theta). Seasonal R-s variation related more to theta than to T-s, which could be explained by extremely low annual precipitation (138 mm), concentrated during winter months. The correlation between T-s and R-s was higher when measured under plants compared to bare ground. The afforested site had in average 17% lower annual R-s (p = 0.06) than the control site. During some months of the third year of measurements, the afforested site showed greater R-s than the control, suggesting that in the near future, R-s might be higher for the afforested site than for the natural condition, depending on the effect that trees may have on soil carbon stability, temperature and hydrological conditions. (C) 2012 Elsevier Ltd. All rights reserved.