Stefania Papa

Soil microbial activity in three evergreen oak (Quercus ilex) woods in a Mediterranean area.

Publisher Summary This chapter reviews the study on soil respiration and enzyme activities—cellulase, xylanase, invertase, protease, and trealase—in three evergreen oak woods in Southern Italy (Campania). The experimental sites differed in chemical and physical characteristics and microclimatic conditions. The chapter evaluates whether differences in chemical and physical soil characteristics and in microclimatic conditions promote differences in the biological activity of microbial communities. The microbial activity was tested every three months for one year. Microbial respiration showed seasonal variations, with minimum levels in summer and maximum levels in wet seasons, and this pattern closely followed seasonal changes in moisture content. In absolute terms, the highest levels of microbial respiration were found in the Vesuvius soil, which also had the highest organic C content, whereas the lowest levels were found in the Castel Volturno soil. Seasonal variations in enzyme activities were also found with good correlation with soil moisture content. No significant differences in enzyme activity were found among the three studied woods.

Soil organic matter, nutrient distribution, fungal and microbial biomass and enzyme activities in a forest beech stand on the Apennines of southern Italy

The aim of this study was to analyse the amount and qualitative characteristics of organic matter (OM) in the litter horizon (considering leaf litter at different decomposition stages) and underlying soil to a 30-cm depth in a beech stand on the Apennines in southern Italy. Distribution of major nutrients as well as fungal and microbial biomass were also evaluated, in addition to beech leaf nutrient content monitor from full expansion to abscission in order to estimate annual nutrient input to soil from litterfall and nutrient retranslocation before abscission. OM was significantly higher in leaf litter. C/N ratio and the Na, Mn, Fe levels also decreased along the decomposition continuum, whereas N and S contents slowly decreased with soil depth. Generally, leaf nutrient content was also significantly lower in dead leaves, indicating efficient retranslocation to persistent organs. Fungal biomass was the highest in leaf layers, with no significant changes between spring and autumn samplings. Enzyme activities did not differ significantly along the decomposition continuum but marked decreases were found in the upper soil layer; these remained relatively constant, with the exception of laccase, at deeper soil depths. No seasonal effect on enzyme activities and OM content was found.

Crassulacean acid metabolism in Sedum dasyphyllum L.

Abstract Crassulacean Acid Metabolism (CAM) in Sedum dasyphyllum L. (Crassulaceae) was analysed by studying four ecotypes collected in sites at different altitudes in the Campania region (Italy), and grown in well‐watered conditions at the Botanical Garden of Naples. During the growth season, from winter to late spring, the overall malate content at dusk and at dawn declined strongly, thus showing a negative correlation with photoperiod. Overnight malate accumulation occurred even in plants kept in well‐watered conditions, but its extent varied with time and among the ecotypes. It was not related to photoperiod but to the daily temperature excursion which, when below a certain value, could prevent CAM activity. The specific activity of the enzymes involved in CAM also showed a seasonal pattern with a significant increase for phosphoenolpyruvate carboxylase, but a decrease for NAD‐dependent malate dehydrogenase and NADP‐dependent malic enzyme, at least in two ecotypes. Because phosphoenolpyruvate carboxyki...