Implications of afforestation vs. secondary succession for soil properties under a semiarid climate

Afforestation or secondary succession after cropland abandonment are different strategies to restore soil ecosystem services such as nutrient cycling, soil conservation, and carbon sequestration. However, the studies on the effects on soil-property dynamics after land-use changes are limited in semiarid regions. In this context, an experimental area with a semiarid climate allowed the assessment and comparison of physicochemical soil properties (soil organic C [SOC], soil total N [TN], available P [AP], available K [AK], cation-exchange capacity [CEC], bulk density [BD], pH, available water-holding capacity [AWHC], and C:N ratio) after Pinus halepensis afforestation and secondary succession following agriculture abandonment in 1994. The impact of 12 soil-preparation treatments for planting on soil properties was also evaluated. For this, soil samples (0-10 cm deep) from the afforestation were taken in 1998, 2002, 2007, 2010, 2013, and 2016, and from abandoned cropland in 2010, 2013, and 2016. In afforestation, soil-preparation treatments did not alter differentially the soil properties after 22 years. Significant differences among years were found in SOC, TN, AP, AK, CEC, pH, and C:N. BD changes were detected neither in afforestation nor in abandoned cropland. After 22 years, only SOC, AK and the C:N ratio proved significantly higher in afforestation than in abandoned cropland. In general, soil properties improvement (i.e. SOC, TN, AP, AK, and CEC) was slow after afforestation and abandoned cropland likely due to the legacy of the previous land use (cereal crops) and the semiarid climate influence.