Factors determining enzyme activities in soils under Pinus halepensis Mill. and Pinus sylvestris L. plantations in Spain: a contribution to sustainable forest management.

Key message Water availability and soil pH seem to be major constraints for enzyme activities in calcareous soils under Pinus halepensis and acidic soils under Pinus sylvestris plantations respectively. Proposals for improving enzyme activities may include the promotion of broadleaf species to increase soil pH and the modulation of stand density or the implementation of soil preparation techniques to facilitate water infiltration. Context Soil enzymes play a key role in nutrient turnover in forest ecosystems, as they are responsible for the transformation of organic matter into available nutrients for plants. Enzyme activities are commonly influenced by temperature, humidity, nutrient availability, pH, and organic matter content. Aims To assess the differences between enzyme activities in calcareous soils below Pinus halepensis and acidic soils below Pinus sylvestris plantations in Spain and to trace those differences back to edapho-climatic parameters to answer the questions: Which environmental factors drive enzyme activities in these soils? How can forest management improve them? Methods The differences in climatic, soil physical, chemical, and biochemical parameters and the correlations between these parameters and enzyme activities in soils were assessed. Results Low pH and high level of phenols in acidic soils under Pinus sylvestris and water deficit in calcareous soils under Pinus halepensis plantations appeared to be the most limiting factors for enzyme activities. Conclusion Options such as the promotion of native broadleaf species in the Pinus sylvestris stands and the modulation of Pinus halepensis stand density or the implementation of soil preparation techniques may improve enzyme activities and, therefore, nutrient availability.