Search results for "Arid"
showing 10 items of 1382 documents
The impact of natural and anthropogenic factors on groundwater quality in an active volcanic/geothermal system under semi-arid climatic conditions: T…
2017
Abstract A comprehensive hydrogeochemical study of the cold and thermal groundwaters of the presently quiescent volcanic system at Methana was undertaken that involved collecting 71 natural water samples. Methana is a peninsula in Peloponnesus, Greece whose arid climate and hydrological situation is similar to that of the nearby small islands of the Aegean Sea. Similarly, the chemical and isotopic compositions of its water are dominated by the mixing of seawater with meteoric water both through direct intrusion and meteoric recharge. However, the simple mixing trends at Methana are modified by water–rock interaction processes, enhanced by the dissolution of endogenous CO2, which lead to str…
Vegetation cover seasonal changes assessment from TM imagery in a semi-arid landscape
2004
This work evaluates the suitability of spectral mixture analysis (SMA) methods to assess vegetation cover seasonal changes in a desertification context. Our main interest is to produce remotely sensed derived maps, sensitive to vegetation activity and quite independent of the soil background. A further aim is to analyse the inter-annual variations of this magnitude for different natural vegetation species, in response to seasonal and climatic changes. Fractional vegetation cover (FVC) was obtained using a Variable Endmember Spectral Mixture Analysis (VESMA) technique. The aim is to identify the main vegetation cover and lithological units and decompose them in separate stages. The use of sp…
Quick and Slow Components of the Hydrologic Response at the Hillslope Scale
2016
It is widely recognized that the Hortonian mechanism of runoff generation occurs in arid and semi-arid regions, generally characterized by high rainfall intensity on soils exhibiting low infiltrabilities. Differently, in steeply sloping forested watersheds in humid climates, by infiltrating through a highly permeable upper soil horizon, water moves beneath the soil surface determining a slow response. However, in most real cases, for example when in arid regions mountain forested areas take place, both (quick and slow) runoff generation processes coexist and together contribute to the hydrologic hillslope response. In this paper, based on analytical solutions of the hydrologic response, ins…
Pedogenesis and Variability in Soil Properties in a Floodplain of a Semiarid Environment in Southwestern Sicily (Italy).
2010
We performed a pedological study of the variability in soils in a floodplain area of a semiarid region in southwestern Sicily. The objectives of our research were to (i) investigate the role of parent material, erosion, and distribution processes on soil pedogenesis and horizon differentiation; (ii) evaluate the statistical distribution of soil properties; and (iii) interpret these distributions in terms of pedogenic and other processes. Our results showed that not all soil properties examined followed a normal distribution and that even when logtransformed, the degree of normality of the soil salinity data did not improve. Furthermore, principal component analysis was performed to investig…
Compared regimes of NDVI and rainfall in semi‐arid regions of Africa
2006
Bi‐monthly normalized difference vegetation index (NDVI) at an 8 km spatial resolution from the advanced very high resolution radiometers (AVHRR) was used from 1981 to 1995 to analyse the vegetation response to rainfall supply in semi‐arid regions of Africa. Within the 200–600 mm annual rainfall belt, for which the apparent NDVI response to rainfall was the strongest, three regions were selected which exhibited different patterns in their NDVI regimes and/or relationships with rainfall. The regions, located in western, southern and eastern Africa, were split into coherent sub‐regions in terms of mean regime of photosynthetic activity through a cluster analysis. Overall, intra‐regional diffe…
Influence of surface roughness in hydrological response of semiarid catchments
2005
Abstract Here, an investigation has been carried out in order to understand the influence of the surface roughness in the definition of the hydrological response of semiarid catchments. Following a previous study of one of the authors, a modified version of TOPMODEL is used, in which the convolution routing procedure has been extended to the hillslopes by specifying the routing velocity for each pixel of the watershed. These velocities have been linked to the watershed land use through the different surface roughness whose coefficients has been derived on the basis of Engman's table. In this paper, roughness coefficient distributions are expressed as function of a unique value treated as a …
A conceptual dynamic vegetation-soil model for arid and semiarid zones
2007
Plant ecosystems in arid and semiarid zones show high complexity from the point of view of water resources, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development. The available water in the system results from a water balance where the soil, vegetation and the atmosphere are the key issues; but it is the vegetation which modulates (to a great extent) the total balance of water and the mechanisms of the feedback between soil and atmosphere, being the knowledge about soil moisture quite relevant for assessing available water and, as a consequence, for growth and plants maintenance and t…
Proteinaceous and oligosaccharidic elicitors induce different calcium signatures in the nucleus of tobacco cells.
2005
We previously reported elevated cytosolic calcium levels in tobacco cells in response to elicitors [D. Lecourieux, C. Mazars, N. Pauly, R. Ranjeva, A. Pugin, Analysis and effects of cytosolic free calcium elevations in response to elicitors in Nicotiana plumbaginifolia cells, Plant Cell 14 (2002) 2627-2641]. These data suggested that in response to elicitors, Ca2+, as a second messenger, was involved in both systemic acquired resistance (RSA) and/or hypersensitive response (HR) depending on calcium signature. Here, we used transformed tobacco cells with apoaequorin expressed in the nucleus to monitor changes in free nuclear calcium concentrations ([Ca2+](nuc)) in response to elicitors. Two …
I RODITORI DI CAVA MONTICINO (BRISIGHELLA, RA)
2021
Rodents are the most abundant group of small mammals occurring in Brisighella deposits. They are represented by 12 species in total, among which 2 hamsters (Apocricetus cf. barrierei and Ruscinomys cf. lasallei), 2 dormice (Muscardinus sp. and Myomimus sp.), 1 porcupine (Hystrix (Hystrix) depereti), 2 sciurids (Atlantoxerus cf. rhodius and Hylopetes sp.) and 5 species of muridae (Apodemus cf. gudrunae, Centralomys benericettii, Occitanomys sp, Paraethomys meini and Stephanomys debruijni). This association suggests a relatively dry open environment, interrupted by forest environment with more or less dense underground.
Production of microalgal external organic matter in a Chlorella-dominated culture: influence of temperature and stress factors
2020
[EN] Although microalgae are recognised to release external organic matter (EOM), little is known about this phenomenon in microalgae cultivation systems, especially on a large scale. A study on the effect of microalgae-stressing factors such as temperature, nutrient limitation and ammonium oxidising bacteria (AOB) competition in EOM production by microalgae was carried out. The results showed non-statistically significant differences in EOM production at constant temperatures of 25, 30 and 35 degrees C. However, when the temperature was raised from 25 to 35 degrees C for 4 h a day, polysaccharide production increased significantly, indicating microalgae stress. Nutrient limitation also see…