Effects of afforestation on soil respiration in an arid shrubland in Chile

We studied the effects of afforestation on soil respiration (Rs) in an arid shrubland in northern Chile. We sampled Rs 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 (Ts) was a good predictor of Rs on certain periods of the year, although we could not relate this to specific levels of soil moisture (θ). Seasonal Rs variation related more to θ than to Ts, which could be explained by extremely low annual precipitation (138 mm), concentrated during winter months. The correlation between Ts and Rs was higher when measured under plants compared to bare ground. The afforested site had in average 17% lower annual Rs (p = 0.06) than the control site. During some months of the third year of measurements, the afforested site showed greater Rs than the control, suggesting that in the near future, Rs 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.

► Soil temperature was a good predictor of Rs on certain periods of the year.
► Soil water content was the most relevant driver of seasonal Rs variability.
► The relation Ts–Rs was higher when measured under plants compared to bare ground.
► The afforested site had annual Rs 17% lower than the natural condition.
► Soil respiration could become higher in afforested site depending on several factors.