How do land use and land cover changes affect soil properties and nutrients in abandoned agricultural terraces?

Agricultural terraces are very conspicuous features of many mountain landscapes in the world. In the Mediterranean region, rural depopulation and farmland abandonment has led to a process of vegetation expansion on former cultivated terraces, either by natural revegetation or afforestation programs. The main objectives of this study were i) to determine land use changes in a representative Mediterranean mountain area dominated by agricultural terraces in the past, and ii) investigate the effect of different land use and land cover (LULC) on soil properties, SOC and N stocks. For this purpose, five different LULCs (cultivated land, dense and sparse shrublands, old Q. ilex forest and P. sylvestris afforestation) were selected in terraced slopes in the Iberian range, in N. Spain. For each LULC, soil samples were collected every 10 cm down to 50 cm. The results showed that in the last 70 years, shrub cover has doubled (from 280 ha in 1957 to 430 ha in 2020) and forest cover has increased from 46 ha to 171 ha. SOC and N contents strongly decreased with depth, except for the cultivated plots, where the values remain similar through the soil profile. In the top layer, SOC contents were higher in Q. ilex, followed by afforested P. sylvestris, dense and sparse shrubland and cultivated plots. N contents presented a similar pattern except for afforested P. sylvestris, which presented the lowest values. SOC and N stocks were higher in Q. ilex, cultivated land, dense and sparse shrubs, and afforested P. sylvestris. Understanding the effects of LULCC on soil properties and nutrients is essential to assess land management practices after farmland abandonment on agricultural terraces.

Acknowledgements: This research was supported by the MANMOUNT project (PID2019-105983RB-100/AEI/10.13039/501100011033), funded by the MICINN-FEDER.