The role of secondary succession and parent material as main drivers of soil bacterial community composition in terraced abandoned olive groves from a Mediterranean hyper-humid mountainous area

Abstract

[eng] Farmland abandonment and subsequent secondary succession processes in marginal areas are widespread phenomena in the European Mediterranean Region, triggering changes in soil properties and soil microorganisms. However, few studies have been focused on Mediterranean humid mountainous areas, being the first in assessing the influence of both ecological succession and parent lithologic material over soil properties and soil bacterial communities. To examine the effects of secondary succession and elucidate the role of parent material on soil bacterial communities, 6 soils plots were sampled from the combination of abandoned and rainfed olive groves, terraced or non-terraced, and over four parent lithologic materials in the Lluc Valley, Mallorca island, a Mediterranean hyper-humid mountainous area. Soil bacterial diversity and taxonomic composition at the phylum and family level in each field were analyzed by rRNA 16S amplicon sequencing. In addition, a series of soil physicochemical and other microbiological properties, and enzyme activities were assessed. Results showed that the secondary succession and the parent material significantly affected soil physicochemical and microbiological properties, soil enzyme activities and soil bacterial communities’ diversity and taxonomic composition. According to the redundancy analysis (db-RDA), specific surface area (SSA), total organic carbon (TOC), basal soil respiration (REB), microbial mass carbon (Cmic), urease activity (Ur) and alkaline phosphatase activity (Php) were the soil properties that contributed to significant changes on bacterial communities’ composition at the family level. TOC, Cmic and REB presented a positive correlation, being higher in abandoned fields compared to rainfed olive groves and in fields with Lias limestones. Xanthobacteraceae, Pirellulaceae, Nitrosomonadaceae and Reyranellaceae were more abundant in fields with higher TOC, Cmic and REB, following a copiotrophic behavior. Otherwise, Chitinophagaceae, Burkholderiaceae, WD2101 soil group and Beijerinckiaceae were more abundant in soils with lower resources, presenting an oligotrophic behavior. This study evidenced that farmland abandonment led to improve soil quality, with positive feedbacks provided by parent lithologic material.