Soil Properties

Magnetic soils can seriously hamper the performance of electromagnetic sensors for the detection of buried land mines and unexploded ordnance (UXO). Soils formed on basaltic substrates commonly have large concentrations of ferrimagnetic iron oxide minerals, which are the main cause of soil magnetic behavior. Previous work has shown that viscous remanent magnetism (VRM) in particular, which is caused by the presence of ferrimagnetic minerals of different sizes and shapes, poses a large problem for electromagnetic surveys. The causes of the variability in magnetic soil properties in general and VRM in particular are not well understood. In this paper we present the results of laboratory studies of soil magnetic properties on three Hawaiian Islands: O"ahu, Kaho"olawe, and Hawaii. The data show a strong negative correlation between mean annual precipitation and induced magnetization, and a positive correlation between mean annual precipitation and the frequency dependent magnetic behavior. Soil erosion, which reduces the thickness of the soil cover, also influences the magnetic properties.

In large canal irrigation project areas, integrated management of surface and groundwater resources can improve water use efficiencies and agricultural productivity and also control water logging. Such integrated management requires an estimation of spatial distribution of recharge and ground water flow in the underlying aquifer. Recharge occurs both as percolation losses from fields and seepage losses from the water distribution network. Percolation losses are influenced by weather, soil properties, land use, and canal water and groundwater use. Seepage losses depend on the conditions of flow in the water distribution system. In large irrigation project areas all the factors influencing the recharge of groundwater vary spatially. In this study, a geographical information systems (GIS) is used to map the spatial distribution of recharge which then serves as input to a regional groundwater flow model for simulating the behavior of the underlying aquifer. The basis is that the project...

With regard to the high mortality of silver fir (Abies alba Mill.) in Italy, pathological and climatic causes are considered crucial, while soil properties are usually neglected. Two of the largest Tuscan forests of this species, the one of Vallombrosa and the other of Mount Amiata, are seriously affected byHeter obasidion annosum, a fungus causing root rot. However, in spite of the same provenance of firs and intersterile group of the fungus, the tree death is different at the two sites. In one case, firs quickly died standing, while in the other they were uprooted after a slow course of the illness. A study was conducted on the two localities to perceive the role of soil properties in this connection. In the light of our results, pedological conditions are important, negatively affecting the plants either “directly” — limiting deep rooting and preventing the trees to achieve sufficient anchorage in the ground — and “indirectly” — favouring the spread and the virulence ofH. annosum. Mit Blick auf die hohe Sterblichkeit der Weiß-Tanne (Abies alba Mill.) in Italien werden pathologische und klimatische Gründe als entscheidend betrachtet, Bodeneigenschaften jedoch gewöhnlich vernachlässigt. Zwei der ausgedehntesten toskanischen Wälder dieser Gattung, der eine in Vallombrosa, der andere am Amiata-Berg, sind schwer vonHeterobasidion annosum betroffen, einem Pilz, der Wurzelfäulnis auslöst. Trotz derselben Herkunft der Tannen und der intersterilen Gruppe des verläuft der Baumtod an beiden Standorten verschieden. Im einen Fall starben die Tannen rasch und blieben stehen, während sie im anderen Fall nach langsamem Krankheitsverlauf entwurzelt wurden. An beiden Standorten wurde eine Studie durchgeführt, um in diesem Zusammenhang die Rolle der Bodenbeschaffenheit herauszufinden. In Anbetracht unserer Ergebnisse sind pädologische (pedological) Bedingungen wichtig und beeinträchtigen die Pflanzen sowohl „direkt“ — indem sie tiefe Verwurzelung einschränken und die Bäume am Erreichen ausreichender Bodenverankerung hindern — als auch „indirekt“ — indem sie Ausbreitung und Virulenz vonH. annosum begünstigen.

Leaf-cutting ants (Atta spp.) are known for their extensive defoliation in neo-tropical forests and savannahs. Debate about the costs and benefits of their activities has been largely dominated by their detrimental effects on agriculture and agroforestry. However, the large accumulation of nutrients and changes in soil properties near their nests might benefit plants growing near them. Here, we test whether trees use nutrients that accumulate in debris piles near, or refuse chambers within, leaf-cutting ant nests. At two tropical sites (a moist tropical forest site in Panama and a savannah site in Brazil), we fed leaves labelled with the stable isotope 15N to two species of leaf-cutting ants (Atta colombica and Atta laevigata) and traced the stable isotope label in plants surrounding the two nests. Thus, we show that plants in both sites access resources associated with Atta nests. In addition, leaf tissue of trees near the nests labelled with 15N had significantly higher calcium co...

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et a ̀ la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Serge Marlet et Pierre Ruelle (éditeurs scientifiques), 2002. Vers une maîtrise des impacts environnementaux de l’irrigation. Actes de l’atelier

The islands of the Mediterranean Basin probably represent some of the ecosystems globally most at risk from invasive species. Compared to neighbouring mainland areas, island floras have a significantly higher proportion of alien plant species. Yet the circumstances that have led to this situation and the subsequent consequences of plant invasions remain poorly understood. This knowledge deficit is addressed in this paper through a comprehensive review of recent research findings. Most alien plants occurring on Mediterranean islands have been introduced intentionally for economic purposes although there still exists a sizeable proportion that arrives by accident. A wide range of alien plant functional types have colonized Mediterranean islands. While certain traits appear important, e.g. reproductive strategies, species characteristics are closely allied to the habitats invaded. Large-scale biogeographic studies have highlighted a strong correlation between local and regional abundan...

The risk of soil acidification is high in the Athabasca oil sands region (AOSR) in Alberta, Canada, due to elevated SO2 emission and the resultant acid deposition to sensitive, coarse-textured soils. Understanding the sulfate adsorption characteristics of soils sensitive to acidification will help establish critical loads of acid deposition in AOSR. Sulfate adsorption properties were evaluated and relationships between sulfate

A series of soils of the Mayo-gwoi flood plain in Jalingo Nigeria were classified and characterized to develop a baseline for soil improvement and increase agricultural productivity. Seven pedons were dug in the area marked Soil units 1, 2 and 3 and were examined with regards to their morphology, physical and chemical properties. The soils were formed over basement complex rocks and alluvial deposits, having shallow to deep pedons, they had high sand fraction and clay content which increased irregularly with depth. The dominant hues were 10YR at the surface and 2.5Y at the subsurface indicating poor drainage. Soil texture varied from sandy clay loam to clay. The pH was slightly acidic to alkaline (6.6-7.7), organic carbon was low (mean: 0.2%). The N content was low to moderate with mean value of 0.02%. Available phosphorus content were generally low to moderate in all pedons studied having mean value of 8.8 mg/Kg. Cation exchange capacity (CEC) was generally moderate in all the pedo...

A two year field experiment was conducted to investigate the effect of different tillage methods on soil physical properties and crop yield of watermelon. Tillage treatments in the study were moldboard plow + two passes of disk harrow as conventional tillage (CT), two passes of disk harrow as reduced tillage (RT), one pass of disk harrow as minimum tillage (MT) and no-tillage (NT) as direct drilling method. The statistical results of the study indicated that tillage method significantly (P≤0.05) affected crop yield, fruit weight, fruit length, fruit diameter and total soluble solids, but there was no significant differences in other components such as number of plants per hectare, number of fruits per plant, root length and root dry matter. The maximum value of crop yield (21.11 t ha), number of plants per hectare (2730), fruit weight (5.15kg), fruit diameter (20.3cm), root length (42.0cm) and root dry matter (54.1%) was observed in case of CT treatment, while maximum value of numbe...