Comparison of the interest of four types of organic mulches to reclaim degraded areas (Part 2): Microbial activities and abiotic factors

Abstract

A field experimentation conducted in a wooded degraded area and contaminated by metals, aimed to compare the effectiveness of four types of organic mulches: Ramial Chipped Wood (RCW), crushed Miscanthus, dead leaves and wheat straw regarding the ecosystem's functionality. We likewise tested the plastic sheeting regularly used to forestall weed development in green spaces as well as a negative control which consisted in soil without mulch. For this purpose, microbial activities (Fluorescein diacetate hydrolyzing activity, Laccases and Urease) and abiotic factors (moisture, temperature, metal concentrations, C/N rate and organic carbon content) were monitored in the organo-mineral horizon of soil surface for 13 months. The degradation rate of the different mulches has also been taken into account. The results revealed that the organic mulching technique could provide habitats for many organisms and micro-organisms of soil with favorable microclimate and/or alternative food source (fungi) in peri-urban and planted area, not only in agricultural areas. In the current context of climate change, the mulching technique could limit desiccation stress in terrestrial ecosystems by offering more favorable temperature conditions (≈2 °C lower on average than a surface soil without mulching) and this from the very first cm of the soil. In view of the indicators followed (high temperatures, low microbial activity and low biodiversity), the plastic sheeting present the most hostile reception conditions to the soil organisms. Every one of the organic mulch examined has its advantages and limitations and the decision of the kind of mulch to be utilized requires thinking as indicated by the fixed goals. However, Miscanthus seemed to be the most suitable compromise obtaining the higher score according to our evaluation criteria: it degraded slowly, it has low metal content and fungi were very active which is favorable to functionality of the ecosystem and to the soil organisms.