Soil microbial metabolism and nutrient status in a Mediterranean area as affected by plant cover

The Mediterranean area of Southern Italy is characterized by different natural plant covers that mainly reflect different successional stages (i.e. low maquis, high maquis, Quercus ilex wood) and managed areas with introduced plant species (such as Pinus species). Soil properties could be affected by plant cover types as well as by plant species. Our objective was to determine the relationships of plant cover types and plant species with the chemical and biological characteristics of the soil. In four neighbouring areas with different plant cover types (low maquis, pure high maquis, high maquis with pines and pinewood, with pines planted by foresters in both cases), soil samples were collected under different plant species in order to evaluate the effect of plant cover types and plant species on soil properties. Soil samples were analyzed for nutrient content, microbial biomass, soil potential respiration and enzymatic activity (phosphatase, arylsulphatase, β-glucosidase and hydrolase activities) as well as for pH, water holding capacity (WHC) and cation exchange capacity (CEC). Application of cluster analysis and principal component analysis to the data revealed that the plant cover type was the key factor influencing soil properties more than plant species. In fact, the largest differences were observed between pure high maquis soils and all other soils, with pure high maquis soils generally showing the highest values of WHC, CEC, nutrient content, organic and microbial C, soil respiration, phosphatase, arylsulphatase and β-glucosidase activities. The significantly lower values of these variables in the low maquis relative to the pure high maquis probably reflect the effect of ecological succession on soil. The high maquis with pine, differing from the pure high maquis only for the presence or absence of pine, showed values of soil physical, chemical and biological characteristics similar to those found in the low maquis, thus suggesting that the presence of pine retards soil development. © 2004 Elsevier Ltd. All rights reserved

Soil microbial community as influenced by experimental fires of different intensities

The effect of high- and low-intensity experimental fires on soil microorganisms and organic pool was investigated in a Mediterranean maquis area of Southern Italy. The study included evaluation of organic (Corg) and microbial (Cmic) carbon, total and active fungal mycelia, soil potential respiration and catabolic evenness (i.e., uniformity of substrate use) in burned and unburned soils over a 1-year period. The fungal fraction of microbial carbon, metabolic quotient (qCO2: mg CO2-C mg-1Cmic 10 d-1) and coefficient of endogenous mineralization (CEM: mg CO2-C g-1Corg 10 d-1) were also calculated. Organic and microbial C, soil potential respiration, qCO2 and CEM increased at least in the first 3 months after fire. The total and active mycelia and the fungal fraction of microbial carbon decreased throughout the first year after fires. Catabolic evenness decreased in the first week after fires. High-intensity fire produced larger effects on soil microorganisms than low-intensity fire at least in the first week after fire

Effects of fire on soil respiration, ATP content and enzyme activities in Mediterranean maquis

Question: Do low or high intensity fires affect micro-organism activity in the upper soil layer of Mediterranean maquis? Location: 600 m from the sea in the Nature Reserve of Castel Volturno (Campania, southern Italy, 40°57' N; 13°55' E). Methods: Soil respiration was measured in situ on intact soil; enzyme activity (cellulase, xylanase, invertase, trehalase and protease) and ATP content were measured on soil samples collected under three species of maquis vegetation: Phillyrea angustifolia L., Myrtus communis L. and Cistus incanus L. Results: Soil microbial respiration showed no significant differences in CO 2 flux in treated and untreated plots, but the ATP content in the soil under C. incanus and M. communis was lower in the treated plots for most of the study period. In the soil under Ph. angustifolia, ATP content was low only for one week after fire. The reduction was more marked in the samples from 'high fire intensity' than from 'low fire intensity' plots. Soil respiration and ATP content exhibited seasonal variations linked to soil water content. Among the enzyme activity measured in the soil under the three plant covers, only invertase declined in burned plots throughout the study period, particularly in the 'high fire intensity' plots. Activity of the enzymes cellulase, xylanase, trehalase and protease had a different sensitivity depending on the respective shrub cover. Conclusions: Impact of fire on soil microbial activity is largely dependent on vegetation mosaic and species identity. © IAVS; Opulus Press

Impact of river overflowing on trace element contamination of volcanic soils in South Italy: Part I. Trace element speciation in relation to soil properties

Volcanic soils affected by different numbers of polluted river flooding events were investigated. Chromium and Cu were the major soil contaminants. Nickel, Fe, Zn and Mn total content never exceeded the Italian mandatory limits. The distribution of Cr and Cu total contents among studied soils indicated that only Cr contamination was related to overflowing events. In polluted soils, sequential chemical extractions revealed a preferential association of Cr and Cu with organic forms. A progressive Cr insolubilization with ageing was observed. Significant amounts of Cr and Cu were extracted by NH4-oxalate, suggesting metals association with short-range-order aluminosilicates and organo-mineral complexes. Possible methodological drawbacks in the use of the EU-BCR chemical speciation protocol on volcanic soils are discussed. Micromorphology and SEM/WDS analyses revealed Cr and Cu enriched silt and clay coatings in surface and subsurface soil horizons, suggesting a transfer of metal-rich sediments along the soil pore network with water movement. © 2006 Elsevier Ltd. All rights reserved