Search results for "Humu"
showing 10 items of 132 documents
Vegetation, soils, and humus forms of Sardinian holm oak forests and approximated cross-harmonization of vegetation types, WRB Soil Groups and humus …
2018
Five plant communities, related to elevation above sea level and geological substrata, are recognized in the holm oak forests of Sardinia (Italy). These forests show a considerable inhomogeneous structure due to present day and past uses. Coppice management prevails, influencing the quantity and quality of organic horizons. Most frequent mineral soils are Cambisols, Leptosols, and Regosols. Regarding the humus forms, Moder and, with less extent, Amphi, are prevailing. Furthermore, the paper presents a synoptic table giving a rough picture of the relationships between vegetation types, WRB Soil Groups and humus forms in selected Mediterranean ecosystems.
Transmission of PPV-M to Prunus persica by Brachycaudus schwartzi and Phorodon Humuli (Hem. Aphididae)
2004
Aphids are reported to be vectors of the most serious viral pathogen of the drupaceous species plum pox virus (PPV), but there is little direct experimental evidence of this. PPV (serotype M) is widespread in peach orchards even where there are severe control measures. Laboratory bioassays were conducted to study, under controlled conditions, the ability of Brachycaudus schwartzi (Borner) and Phorodon humuli (Schrank) to transmit PPV (serotype M). The results have shown that all the peach trees tested had evident symptoms of sharka and were positive to the RT-PCR analysis, confirming the ability of these two aphid species to transmit the virus.
Chemical composition of volatile and fixed oils from of Salvia argentea L. (Lamiaceae) growing wild in Sicily.
2015
The chemical compositions of the essential oil and of the non-polar extracts (petroleum ether, dichloromethane) of the aerial parts (flowers, leaves and stems) of Salvia argentea L. were determined by GC-FID and gas chromatographyâmass spectrometry analysis. 14-Hydroxy-α-humulene (40.1%) was recognised as the main constituents of the essential oil of S. argentea, together with 1,3,8-p-menthatriene (12.1%), globulol (7.4%) and β-sesquiphellandrene (5.8%). Tritriacontane (9.9% and 14.1%), heptacosane (8.4% and 10.5%), hentriacontane (8.3% and 10.9%), tetradecanal (8.4% and 10.2%) and methyldotriacontane (7.9% and 7.6%) were recognised as the main constituents of the extracts in petroleum …
Effects of pentachlorophenol in forest soil: a microcosm experiment for testing ecosystem responses to anthropogenic stress
1996
Changes in the structure and function of a soil decomposer community and growth of birch (Betula pendula) due to chemical contamination were studied in laboratory microcosms. Sodium pentachlorophenate (PCP) was added to the humus layer of a simulated forest soil at three nominal concentrations (0, 50 and 500 mg kg-1 dry mass). After two growing periods (48 weeks), there were more small soft-bodied mites, but less collembolans and microbial biomass, in the higher PCP concentration treatment than in the other treatments. Number of enchytraeids were significantly reduced and fungal-feeding nematodes became extinct in the soil with the higher PCP concentration. Soil respiration did not change d…
Humus in World Soils
1996
Publisher Summary This chapter discusses the soil humus and total organic carbon (OC) content. It reviews the results concerning the changes in soil organic matter (SOM) chemical nature regardless of the technical methods used. Information about C cycling and storage in soils is also given. Soil humus is characterized by its amounts and properties such as water retention capacity, aggregation and cementing agent, and the ability to absorb both nutrients and contaminants. The uncontrolled decrease in soil humus content affects soil water regime, aeration, fertility, and purifying capacity. The chapter focuses on the main soil types and the areas of the world where they are found, and conside…
Soil humic acids formation and characteristics in a xeric mollisol reforested with two tree species
2002
Publisher Summary The study discussed in this chapter examines the influence on humic acids (HAs) characteristics of different plant species—Pinus halepensis Miller and Cedrus atlantica (Endl) Carriere—used in the restoration of a Mollisol under xeric conditions. The area studied is in Sicily (Italy), and two stands were compared 40 years after planting. The differences among soil profile developments in the two stands were investigated by chemical and biochemical methods to understand the different levels at which the processes of pedogenesis acted in the study area. The chapter analyzes some chemical and spectroscopic characteristics of HAs, separated from two selected pedons. The results…
Horizontal distribution of copper, nickel and enchytraeid worms in polluted soil
1999
We studied the horizontal distribution of Cu, Ni and enchytraeid worms (Cognettia sphagnetorum, Vejdovsky, Oligochaeta, Enchytraeidae) in forest soil near a Cu–Ni smelter in SW Finland. Soil samples were taken from a polluted site (2 km from the smelter) and a reference area (8 km from the smelter). We used a hierarchical sampling design in the polluted area for studying possible scale-dependent variability in parameters measured, distance between the samples (different scales) being 5, 50 and 500 cm. Distribution of metals was moderately heterogeneous in the polluted soil; coefficient of variances (CV), 26% for Cu and 32% for Ni. Instead, distribution of enchytraeids in the area was highly…
Morphogenetic characteristics of chernozem leached in mining enterprises pollution conditions
2019
The article presents the results of comparative studies on the uncontaminated (virgin) leached chernozem soil in terms of heavy metal contamination due to zinc plant operations. Study object location is given. The territory under the influence of plant emissions is devoid of vegetation. Everywhere on the soil surface there are manifestations of deep erosion processes and continuous erosion of the topsoil. Soil cuts with morphogenetic descriptions, physical, physico-chemical and biological characteristics of the soil were laid at the objects. The soil cover under the influence of pollution has undergone degradation and led to transformational processes of particle size distribution, humus co…
Labile carbon alleviates wood ash effects on soil fauna
2008
The combined effects of wood ash, sucrose and oxalic acid on enchytraeid size and biomass, the abundance of microbial-feeding nematodes and pH were studied in a full three-factorial design in laboratory microcosms containing 30 g of Norway spruce forest humus. Wood ash treatment reduced enchytraeid size and abundance, but these effects were offset by sucrose without any change in pH or moisture. The positive effects of sucrose were partially counteracted by oxalic acid. Both carbon compounds increased the abundance of obligate microbial-feeding nematodes, indicating enhanced microbial production.
Surface Activity of Humic Substances Within Peat Profile
2012
Humic substances are able to reduce the surface tension of their solutions and thus can act as surface-active substances in natural environment and possibly also for industrial applications. The ability to influence the surface tension of humic substance solutions depends on their origin. The objective of this study is a comparison of the ability of humic substances from peat profile to influence the surface tension of their solutions and identification of the structural characteristics of peat humic acids, determining their surfactant properties. Humic acids isolated from peat demonstrated significant impact of the surface tension of their solutions – they act as weak surfactants. The surf…