Assessment of soil physical properties' statuses under different land covers within a landscape dominated by exotic industrial tree plantations in south-central Chile

Abstract

Land use and land cover changes (LULCC) within a highly anthropized Mediterranean landscape dominated by industrial tree plantation leads to degradation of soil physical properties. This process has been more intense in the coastal range of south-central Chile due to its soils, which are highly susceptible to erosion, combined with a long history of intensive land use changes during the last century, transitioning from native forest (NF) to agriculture and the more recent establishment of Pinus radiata and Eucalyptus spp. exotic tree plantations. In this context, the aim of this study was to assess the statuses of soil physical properties over different land cover situations. Historical land cover maps were determined via supervised classifications using the maximum likelihood classifier applied to satellite imagery. Five land use and land cover categories (LULC) were defined according to main land cover transitions associated with active and abandoned forestry operations that have been reported in the region: NF, pine plantation (P), eucalyptus plantation (Eu), early successional (E-S), and secondary successional (S-S). Successional stages were generated using change detection statistics considering changes between 2001 and 2014 maps. Soil samples were collected at three depths in 39 plots that describe the five LULC. High clay contents were found in all the LULC except Eu and P. These sites have shown more signs of degradation, with lower organic matter (SOM) and macropores and higher shear strength (ShS). Soil organic matter was consistent with litter contribution and quality, establishing lower bulk density (Db) for NF and S-S and higher values for Eu and E-S. ShS and dispersion rate (DR) exhibit a correlation with SOM with lower ShS and higher DR when SOM increased. Relevant differences were identified for structural stability index (SSI) between LULC depending on soil physical quality, besides a positive correlation with SOM. Those results show the need to generate appropriate conditions of vegetation cover in order to recover soils subjected to current forestry management of industrial plantations.