abstract earthworms are an important component of soil fauna, and play a crucial role in the improvement of soil properties. however, very little is known of the interactive influence of earthworms and organic materials on soil enzyme activities, particularly in arid and semi-arid soils. the low organic matter content and the significant role of earthworms in stimulating microbiological and bio...

abstract erosion and sedimentation are the most complicated problems in hydrodynamic which are very important in water-related projects of arid and semi-arid basins. for this reason, the presence of suitable methods for good estimation of suspended sediment load of rivers is very valuable. solving hydrodynamic equations related to these phenomenons and access to a mathematical-conceptual model ...

depth of frost penetration is one of the main indices in agriculture, civil and transportation engineering. soil temperature is a function of several factors including: topography, solar radiation, air temperature, moisture content and other physical properties of soil such as thermal capacity, coefficient of heat conductivity, and specific heat. the main objective of the present paper is to de...

knowledge about low flow statistics is essential for effective water resource planning and management in ungauged orpoorly gauged catchment areas, especially in arid and semi-arid regions such as iran. we employed a data set of 20 riverflow time-series from the iranian central plateau river basin, iran to evaluate the low-flow series using several frequencyanalysis methods and compared the resu...

in arid and semi-arid rangelands, grazing as one of the natural or human induced processes has direct and indirect effects on structure and dynamics of plant community and ecosystems. a study was done to analyze the effects of grazing on plant species diversity and plant functional types‘ (pfts) diversity of arid and semi-arid rangelands. we analyzed plant richness and diversity data from 75 sa...

this study aims to assess the effect of grazing intensity on vegetation structure, soil nutrient concentrations and soil physical properties. the study was carried out in steppe rangelands of saveh, markazi province, iran. four sites with four grazing intensities including very high, high, moderate and non-grazed with the same ecological conditions were selected. to study various vegetation and...

Few studies have investigated the influence of water availability on plant population spatial patterns. We studied changes in the spatial patterns of Caragana stenophylla along a climatic drought gradient within the Inner Mongolian Plateau, China. We examined spatial patterns, seed density, "nurse effects" of shrubs on seedlings, transpiration rates and water use efficiency (WUE) of C. stenophy...

On July 17, 2003, the National Bureau of Economic Research announced that the United States economy had troughed in November 2001 following the peak in March 2001. This makes the 2001 recession one of the shortest in U.S. history being only eight months in length. Whereas business cycles are defined in terms of the overall economies the authors of this paper investigate whether this national re...

Cynara cardunculus.L exhibits an important adaptability to arid and semi-arid regions where high salinity is frequently present. Aiming to introduce its cultivation in the Mediterranean environment especially in Tunisia, it seemed interesting to study seed germination of eight populations of cardoon in four concentrations of NaCl: 0g/L, 2g/L, 4g/L, and 8g/L. Our results showed a good variabilit...

Arid and semi-arid areas occupy one third of the total area of the world. This vast region is rich in natural resources. In recent times, desertification has become a world-wide phenomenon, due to human activities. China also suffers from this problem. Desertification is especially severe in the southeastern part of the arid and semi-arid region of the country. In this paper, the use of remote ...