F. A. Rutigliano

Factors regulating early-stage decomposition of needle litters in five different coniferous forests

The decomposition dynamics of needle litter of Stone pine (Pinus pinea), Corsican pine (Pinus laricio), Scots pine (Pinus sylvestris) and Silver fir (Abies alba) were investigated in a comparative study including five coniferous forest sites. Initial chemical composition, mass-loss rates, and the water-holding capacities of the litters were determined in the early stages of decomposition. Water-holding capacity differed among the fresh litters but increased in linear proportion to litter mass both over each species and over all species combined in a linear regression (r = 0.708; n = 45; P < 0.001). At the early decomposition stages the daily mass-loss rate of Scots pine needles in two dry sites was positively related to (1) the measured litter water content at sampling (r = 0.727; n = 16; P < 0.0025), (2) mean daily precipitation in the period of measurement (r =0.909; n = 16; P < 0.0001). These models could explain water as a rate-limiting factor to the extent of 49 and 81% respectively. A significant linear relationship was also found between decay rate during a moist period and accumulated mass loss (r = 0.771; n = 8; P < 0.05) which has been suggested to be due to the increase of litter water-holding capacity with increasing accumulated mass loss. Three types of decay curve are described and the pattern of decomposition at dry sites has been found to be influenced by moisture variations more than by litter quality.

Functional diversity of the microbial community in Mediterranean maquis soils as affected by fires

Fire is a disturbance in the Mediterranean region associated with frequent drought periods, and can affect the soil microbial community, which plays a fundamental role in nutrient cycling. In the present study the effect of low- and high-severity experimental fires on the soil microbial community was evaluated in an Italian Mediterranean maquis. Burned and unburned soils were compared for functional diversity, specific activities, microbial biomass, fungal mycelia and fungal fraction of microbial carbon, during the first year after fire. In the first week after fire, changes in the functional diversity were observed in burned soils, differing also between low- and high-severity fires. Respiration responses to specific organic compounds were generally lower in burned soils during the whole study period, with a percentage of changed responses from 2 to 70%. The general reduction in burned soils of the fungal fraction of microbial carbon (19–61%) and active mycelia (16–55%), together with the increase in microbial biomass carbon (29–42%) during the first 3 months after fire, suggest a larger and longer effect of fire on fungi than on bacteria. The results indicate a rapid recovery of functional diversity in soil after burning despite the persistent reduction of microbial community activity and the change in its structure.

Lignin decomposition in decaying leaves of Fagus sylvatica L. and needles of Abies alba Mill

Abstract Lignin decomposition in litter of beech leaves and fir needles as related to litter N concentration and litter mass loss was studied for 7 y in two forests at Mount Taburno (41°05′N., 12°07′E.; Campania Apennines). Both types of litter showed a pattern of decomposition characterized by two stages with significantly decreasing decomposition rates. Litter N concentration did not appear to influence the rate of litter decomposition in either the early or the late stage of the process. On the contrary mass loss rates of litter were influenced by lignin concentrations at the beginning of the late stage: the lower the lignin concentration the higher was mass loss rate. Both in beech and fir litter lignin degradation started immediately during incubation. Lignin degradation throughout the study was less in fir needles than in beech leaves with lignin losses of 60–67% and 73–87% of initial amount, respectively. Both in beech and fir litter, lignin loss rate was negatively correlated to the initial N concentration. Lignin loss rate of both beech and fir litter was correlated to litter mass loss rate during the early as well as during the late phase of decomposition. Different dynamics of lignin decomposition between the two species were observed with a higher lignin decomposition rate in the early stage than in the late stage in beech litter, and rates of lignin decomposition increasing from early to late phase in fir litter.

Leaf contamination by atmospheric pollutants as assessed by elemental analysis of leaf tissue, leaf surface deposit and soil

In order to evaluate the influence of air pollutants influx on leaf elemental composition, the concentration of N, S, Cu, Fe and Pb were analyzed in the surface deposit and tissue of Quercus ilex L. leaves from 8 sites of the urban area of Naples. The soil from the trunk base area of Q. ilex trees in the same sites was also analyzed for total contents of N and S and for available contents of Cu, Fe and Pb. In the leaf surface deposit S content was high though significantly (P <0.001) lower than in the leaf tissue, whilst N was not detectable. Cu, Pb and Fe contents in leaf surface deposit were conspicuous. The Pb content was higher in the leaf surface deposit than in the leaf tissue. No correlation between leaf tissue and surface deposit contents was found for S or for Fe. By contrast, positive and significant correlations (P<0.01) were found between leaf deposit and leaf tissue for both Cu and Pb. N and S contents in the leaves were not correlated to the respective contents in the soil and the same was also found for Cu and Fe. In contrast with the presence of limiting concentrations in the soil, N, S and Fe leaf contents were significantly higher than in the leaves from remote sites. The data suggest that direct uptake of airborne pollutants, in addition to root absorption, may influence leaf elemental composition of Q. ilex L. leaves.

TRACE METAL BIOMONITORING IN THE SOIL AND THE LEAVES OF QUERCUS ILEX IN THE URBAN AREA OF NAPLES

The concentrations of Pb, Cu, Fe, and Mn were analyzed in surface deposit and tissue ofQuercus ilex leaves from several sites of the urban area of Naples, exposed to different degrees of air pollution. These included some major roads with heavy traffic loads, squares, and three urban parks. The soil from the trunk base area ofQ. ilex trees in the same sites was also analyzed for total and available metal contents. Pb, Cu, and Fe contents in the surface deposit and leaf tissue were significantly higher (p<0.01) in leaves from roadside sites than in leaves from parks; significant correlations were found between deposit- and tissue-contents of Pb, Cu, and Fe. Mn content in leaves from roadside sites and in leaves from parks were similar and Mn content in the leaf deposit was irrelevant. Significant differences (p<0.001) in both total and available Pb and Cu soil content were found between sampling sites. Also for available Fe and Mn soil content differences among sites were relevant, although the highest values were measured in soil from urban parks. A positive correlation between leaf and soil metal content was found only for Pb, thus suggesting that trace metal contents of leaves directly depend on atmospheric depositions. Seasonal variations of Pb, Cu, and Fe were pronounced at a polluted site, whereas no relevant seasonal variation was observed at a control site; moreover, metal accumulation was high at the polluted site. Mn content and seasonal dynamics were comparable at control and polluted sites.

Fungal mycelium and decomposition of needle litter in three contrasting coniferous forests

The fungal mycelium ingrowth and the rates of mass loss and respiration of needle litter of Pinus pinea, Pinus laricio, Pinus sylvestris, and Abies alba were investigated, in three coniferous forests, over a 3-year period by means of a composite set of incubations. In the early stages, the fungal flora of the decomposing needles was dominated by dematiaceous hyphomycetes and coelomycetes. Basidiomycetes reached a peak after 6 months on pine needles, but were absent from the N-rich needles of A. alba. Soil fungi (Penicillium, Trichoderma, Absidia, Mucor sp. pl.) became most frequent in later stages. At the end of the study period, the total mycelium amount showed the lowest values in all pine needles incubated in the P. laricio forest and the highest ones in P. pinea needles incubated in the P. pinea forest. In all data sets, as in data for boreal forests examined for comparison, the concentration of litter fungal mycelium versus litter mass loss followed a common exponential model. However, in later stages, the amount of litter fungal mycelium was very close to that of the humus at the incubation site, thus supporting the hypothesis of a logistic growth pattern. Respiration rates of decomposing litters varied with season and decreased with litter age to values close to those of the humus at the incubation site. Respiration of water-saturated litter was negatively correlated with the total mycelium concentration, and this was consistent with the observation that in far-decomposed litter only a minor fraction of the total mycelium is alive.

Nutrient dynamics in decaying leaves of Fagus sylvatica L. and needles of Abies alba Mill.

Abstract The dynamics of nutrients (N, P, K, Ca, Mg) in decomposing beech and fir litters was studied. N, P, Mg and Ca content increased in all litters, whereas K content decreased. Nutrient content correlated to mass loss with a few exceptions for K and P. Final N, K, Mg and Ca content was higher the lower the initial content and the higher the initial C/nutrient ratio was. Final P content correlated neither with initial P content nor with initial C/P ratio. All litters lost K very quickly, mainly by leaching. P was lost initially by leaching, although at a lower rate than K, and later by mineralization. Mg, Ca and N showed alternate phases of accumulation and release. Mg losses by leaching occurred only in litters with high initial Mg content; in litters with low initial Mg content, Mg losses occurred by mineralization. Ca and N were lost only by mineralization. A mobility series K>P>Mg>Ca=N is suggested.

Heavy metals and litter decomposition in coniferous forests

The dynamics of Mn, Zn, Fe, Cu, Pb, and Cd during litter decomposition was studied to understand how litter and soil metal concentrations influence the accumulation and/or the release of metals. Three types of leaf litters (green and brown leaves of Populus tremula L., green leaves of Betula pubescens Ehrh.) and four types of needle litters (green and brown needles of Pinus sylvestris L., brown needles of Pinus contorta L. and Pinus pinea L.), differing in heavy metal concentrations were incubated at two unpolluted coniferous forest sites: a temperate silver fir ( Abies alba Mill.) forest at site Monte Taburno, southern Italy, and a boreal Scots pine ( Pinus sylvestris L.) forest at site Jadras, Sweden. Compared to the Scots pine forest, the humic surface horizon of the silver fir forest had a higher pH, higher concentrations of available Cu and Cd, and lower Fe concentration. After a period of about 900 days, all litter types were more decomposed at M. Taburno than at Jadras. Zn, Fe, Pb and Cd concentrations in leaf and needle litters increased at both sites; Cu concentrations increased only in the silver fir forest; Mn concentration decreased in the litter richest in Mn and increased in the litters poorest in Mn. Litter decomposition in an early phase (0 up to 528/565 days) was significantly and positively correlated to initial Cu and Cd concentrations in litter. In a late phase (528/565 up to 918/929 days), decomposition was correlated significantly and negatively with litter Zn and Cu, and significantly and positively with litter Mn concentration at the start (528/565 days) of the period. At both sites, increases in absolute amounts of Fe, Cd, and Pb were observed in all litters; however, P. pinea , which showed the highest initial concentration of Pb, released Pb during decomposition. All litters released Cu at Jadras and accumulated Cu at M. Taburno. Zn was released at both sites from all leaf litters and from the needle litter of P. contorta . Mn was released at both sites from all litters, except the litter of P. tremula , which accumulated Mn at Jadras. The results indicate that heavy metal accumulation or release may depend on the gradient of metal concentration between litter and soil, on the pH of the soil, and on the capacity of litter to bind metal; atmospheric deposition could account at least partly for the increase of absolute amounts of Pb, Fe, and Cu at M. Taburno.

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.