Land-use change from Mediterranean forest to agriculture increases P stocks while reduces P-cycling enzyme activities

Over the past six decades, one-third of the world's territory has been affected by land-use changes, mainly driven by agricultural practices. For example, in Spain, large areas once covered by forests have been replaced by land for conventional cereal cultivation, leading to a loss of soil organic matter and consequently a decrease in soil microbial activity, which affects P cycling. Recently, management in some of these agricultural systems has shifted toward practices that prioritize soil quality and health, incorporating principles of organic and regenerative agriculture. This study examines a land use change from forest to conventional cereal cultivation and ultimately to organic vineyard management in the Spanish Central Plateau. Soil samples corresponding to four distinct land-use histories (forest, old vineyards, new vineyards, cereal) were analyzed, and the following properties were determined: activities of enzymes related to the P cycle, total P content, Olsen P, microbial biomass DNA, pH, electrical conductivity, and soil organic carbon (SOC). Soils were sampled both in the topsoil (0–20 cm) and in the subsoil (20–40 cm). All analyzed enzymes (acid phosphomonoesterase, alkaline phosphomonoesterase, phosphodiesterase and pyrophosphate-phosphodiesterase) showed the highest activities in the surface layer of forest soils, with the lowest levels observed in vineyard soils at both depths. Microbial biomass DNA was strongly correlated with enzyme activity and SOC ( p < 0.001). Conversely, total P concentrations were highest in the surface soils of agricultural lands, with average values of 154 mg kg⁻¹ in cereal fields, 130 mg kg⁻¹ in old vineyards, and 122 mg kg⁻¹ in new vineyards, while forest soils showed the lowest levels, reaching 98 mg kg⁻¹ . We can conclude that converting forest land to agricultural land increases total and available P at both soil depths. However, the decline in P-related enzymatic activities was restricted to the topsoil, as enzymatic activity in the forest subsoil was already low. • Land-use change alters phosphorus availability and related enzyme activities. • Transitioning from forest to agricultural land decreases P-related enzyme activities. • Agricultural soils show higher total and available P contents than forest soils. • Phosphatase enzyme activities positively correlate with soil organic carbon. • Olsen P negatively correlates with P-related enzyme activities.