First application of the QBS-ar Index in South America for the assessment of the biological quality of soils in Chile

Abstract

The QBS-ar (Biological Quality of Soil, based on arthropods) index was applied in Coyhaique National Reserve (Chile). The aims of our research were to assess the abundance and diversity of soil microarthropods in different South American habitats, evaluating to what extent chemical parameters and seasonal changes of weather conditions can affect these organisms. Moreover we wanted to verify if the QBS-ar index was applicable in the Neotropical biogeographic region in order to distinguish between habitats subject to different levels and types of disturbance. Therefore, four habitats were investigated: primary native Nothofagus spp. forest (OG), native forest of secondary growth after fi res (SG), reforestation pine forest (PI) and anthropogenic grassland (PR). During each of seven sampling sessions (nearly one every 10 days) between October and December 2017, fi ve 1 liter soil cores were collected in each habitat. Microarthropods extracted by means of Berlese-Tullgren funnels were counted, identifi ed to the order level and evaluated based on their morphological adaptation to life in soil in order to assess QBS-ar values and related quality classes. Both microarthropod communities and QBS-ar values comparisons showed that OG and SG forests are close to each other, and the same is true for PI and PR. Soils of the former couple of habitats were characterized by a much higher biological quality level with QBS-ar values of 129.1 ± 20.2 and 111.8 ± 6.4, respectively, both corresponding to the quality class 6 (out of a maximum of 7). On the contrary, PI and PR scored QBS-ar values of 83 ± 13.5 and 80.3 ± 10.8, respectively, and quality classes ranged between 3 and 4. Relationships among dominant and subdominant microarthropod taxa and environmental variables were analysed. In particular some chemical properties of soils (pH, CaCO3, Nt, soluble P, exchangeable K, organic matter, C/N ratio) and weather variables (cumulated rainfalls and mean temperatures during the 7 days before each sampling session) were considered. This is the fi rst time the QBS-ar index has been applied in the Southern Hemisphere. Our results seem to indicate this index can be "exported"also to South America, resulting a useful tool for a user friendly assessment of the impact on terrestrial environments by different forms of disturbances and of habitat management.