A. Virzo De Santo

Suitability of two types of organic wastes for the growth of sclerophyllous shrubs on limestone debris: a mesocosm trial.

This study investigated whether overlaying organic wastes directly on limestone debris allowed the growth of sclerophyllous shrubs; the aim was to explore the feasibility of rehabilitation of sites destroyed by quarrying activity. In an open air mesocosm experiment two types of organic material were compared: compost from municipal wastes (C) and a mixture of compost and poultry manure added with wheat husk (C-PW). Mesocosms were pots (1m diameter, 60cm height) containing limestone debris covered by the organic material. Seven mesocosms with C and seven mesocosms with C-PW were planted with sclerophyllous shrubs (Laurus nobilis L., Phillyrea angustifolia L. and Quercus ilex L.). The substrates were characterised in terms of chemical and physical parameters, microbial activity and biomass, and total and active fungal biomass. Shrub photosynthetic performance and growth were evaluated. Over the whole experimental period, organic matter mineralization was higher in C-PW. Microbial biomass and respiration were higher in C-PW than in C but after one year no statistically significant difference between the two substrates occurred. Fungal mycelium was a minor fraction of the microbial community in both types of substrates and decreased dramatically after setting up the mesocosms. The metabolic quotient was higher in C suggesting more stressful conditions as compared to C-PW. Both substrates allowed shrub growth; however photosynthetic rates and the increase of plant size were higher on C-PW than on C. The results demonstrated that, as compared to only compost, the mixture of compost and poultry manure added with wheat husk is a substrate more suitable to both microbial processes and plant growth. Therefore a plan to revegetate quarries based on the use of organic wastes as a substrate for sclerophyllous shrubs could be feasible and, what is more, helpful to mitigate the environmental impact of organic wastes disposal.

Role of fire on soil organic matter turnover and microbial activity in a mediterranean burned area

Publisher Summary This chapter examines the effects of light, intense experimental fires, and of wildfire on the soil microbial biomass and activity and on organic carbon turnover in a coastal area of southern Italy. In the study discussed in the chapter, wildfire that mainly affected plant cover caused a rise in the input of organic matter to the soil but did not significantly influence total microbial biomass or fungal mycelia. In contrast, experimental fires developing on the soil surface caused a decrease in the organic carbon and in total microbial biomass and fungal mycelia. All types of fires resulted in an increased soil potential respiration and metabolic quotient. Moreover, increase in the coefficient of endogenous mineralization after experimental fires and increase in the soil CO 2 emission after wildfire were also observed. The data suggest that burned soils may be an important source of carbon for the atmosphere for several months after fire occurrence. In the case of wildfire, the increase of CO 2 emissions from burned soils depends mainly on the increase in soil microbial activity because of the increase in organic matter in the soil and to some degree on stress conditions. In the case of experimental fires, the increase of CO 2 emissions is because of stress conditions.