Plant-soil interactions in degraded and remediated soils

Abstract

Increasing soil quality and C sequestration in degraded terrestrial ecosystems is one of the main current environmental challenges in the Mediterranean area. Plant species differ in their mechanisms of C-fixation, C allocation into different plant organs, and interaction with soil microorganisms, all these factors influencing the dynamics of soil functioning following the afforestation of degraded soils. In this presentation we summarize the results from different experiments aimed to study the influence of woody plant species on soil properties and functioning in degraded and remediated Mediterranean soils from SW Spain (Guadiamar Green Corridor, Seville). In a threeyear field experiment we tested whether the facilitation of the establishment of holm oak seedlings under the cover of pre-existing shrubs was mediated by improvements in soil quality and microbial activity. The facilitation of oak survival was mainly due to the improvement of light and temperature conditions, and not related to increases in microbial activity (soil extracellular enzymes) in the soils underneath shrubs. In another study we analyzed the effects of four afforested species on different soil C fractions, soil nutrient availability, microbial activity and soil CO2 fluxes 15 years after being planted in the remediated soils from former agricultural lands. The influence of the planted species was more pronounced in the more acidic and nutrient-poor soils. Changes in total soil C stocks after the afforestation of the soils were hardly detectable at that time-scale, although more dynamic variables (microbial biomass, CO2 fluxes) were influenced by the plant species.