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ANALYSIS OF DROUGHT PHENOMENON WITHIN OLTENIA PLAIN, ROMANIA (1961-2010)  [PDF]
ALINA VL?DU?,IRINA ON?EL,CRISTINA RO?CA,ALINA CHIVU
Riscuri ?i Catastrofe , 2013,
Abstract: Analysis of drought phenomenon within Oltenia Plain, Romania (1961-2010). Oltenia Plain, located in the south-western part of the Romanian Plain, is characterized by a moderate pluviometric regime (compared to the pluviometric patterns of plain areas from Romania) and, thus, each negative deviation generates certain complex phenomena, such as drought, that trigger perturbations of the natural environment and economic activities. Thus, determining the annual, seasonal and monthly negative deviations of precipitation at local scale is extremely important in order to establish accurate trends of drought phenomenon. We used 50-year time series (1961-2010) for six meteorological stations. The Standardized Precipitation Anomaly (SPA) and Weighted Anomaly of Standardized Precipitation (WASP) indicate a high predominance of normal years (>70%), both at annual and monthly levels. However, there clearly resulted a deterioration of the rainfall regime in the past three decades – normal years, but negative deviations in 80% of the cases; the driest years in the last five decades (1992, 1993, 2000, 2008); the wettest years (1999 and 2005). Linear regression emphasizes an obvious negative trend of the SPA values for the western and eastern parts of the plain (D.T. Severin, Caracal) and a positive trend for the northern extremity (Craiova); the rest of the region displays a slightly negative trend. At monthly level, the most exposed season is summer, even if drought affected the region in all the months of the year. For the last decade, the impact of drought was also assessed based on satellite images SPOT- VEGETATION and TERRA/MODIS. We used the products NDVI (Normalized Difference Vegetation Index), 10-day synthesis and 1 km spatial resolution and LAI (Leaf Area Index) 8-day synthesis, 1 km spatial resolution, data supplied by French Spatial Agency and NASA. The analysis of these products allowed us to emphasize a spatial and temporal differentiation of the density of vegetation within Oltenia, mainly induced by rainfall deficit and variability.
PATTERNS OF THE MAXIMUM RAINFALL AMOUNTS REGISTERED IN 24 HOURS WITHIN THE OLTENIA PLAIN  [PDF]
ALINA VL?DU?,CRISTIANA V?LCEA
Aerul ?i Apa : Componente ale Mediului , 2012,
Abstract: Patterns of the maximum rainfall amounts registered in 24 hours within the Oltenia Plain. The present study aims at rendering the main features of the maximum rainfall amounts registered in 24 h within the Oltenia Plain. We used 30-year time series (1980-2009) for seven meteorological stations. Generally, the maximum amounts in 24 h display the same pattern as the monthly mean amounts, namely higher values in the interval May-October. In terms of mean values, the highest amounts are registered in the western and northern extremity of the plain. The maximum values generally exceed 70 mm at all meteorological stations: D.T. Severin, 224 mm, July 1999; Slatina, 104.8 mm, August 2002; Caracal, 92.2 m, July 1991; Bechet, 80.8 mm, July 2006; Craiova, 77.6 mm, April 2003. During the cold season, there was noticed a greater uniformity all over the plain, due to the cyclonic origin of rainfalls compared to the warm season, when thermal convection is quite active and it triggers local showers. In order to better emphasize the peculiarities of this parameter, we have calculated the frequency on different value classes (eight classes), as well as the probability of appearance of different amounts. Thus, it resulted that the highest frequency (25-35%) is held by the first two classes of values (0-10 mm; 10.1-20 mm). The lowest frequency is registered in case of the amounts of more than 100 mm, which generally display a probability of occurrence of less than 1% and only in the western and eastern extremities of the plain.
Rainfall intermittency and vegetation feedbacks in drylands
M. Baudena,A. Provenzale
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2008,
Abstract: We discuss a simplifed, conceptual model for the dynamics of the soil-vegetation system in drylands. The model considers the different dynamical processes taking place in vegetated and non-vegetated soil and it distinguishes between the upper soil layer, where rapid evaporation dominates, and the deeper root layer where only plant transpiration takes place. We explore the role of rainfall intermittency and of different plant colonization strategies, and discuss in detail the effect of two different vegetation feedbacks: reduced evaporation due to plant shading and increased infiltration in vegetated areas. The results of the analysis indicate that both temporal rainfall intermittency and the shading/infiltration feedbacks have a beneficial effect on vegetation. However, it turns out that in this model rainfall intermittency and vegetation feedbacks have almost a mutually exclusive role: whenever one of these two components is present, the addition of the other does not further affect vegetation dynamics in a significant way.
Rainfall intermittency and vegetation feedbacks in drylands
M. Baudena,A. Provenzale
Hydrology and Earth System Sciences Discussions , 2007,
Abstract: We discuss a simplifed, conceptual model for the dynamics of the soil-vegetation system in drylands. The model considers the different dynamical processes taking place in vegetated and non-vegetated soil and it distinguishes between the upper soil layer, where rapid evaporation dominates, and the deeper root layer where only plant transpiration takes place. We explore the role of rainfall intermittency and of different plant colonization strategies, and discuss in detail the effect of two different vegetation feedbacks: reduced evaporation due to plant shading and increased infiltration in vegetated areas. The results of the analysis indicate that both temporal rainfall intermittency and the shading/infiltration feedbacks have a beneficial effect on vegetation. However, it turns out that in this model rainfall intermittency and vegetation feedbacks have almost a mutually exclusive role: whenever one of these two components is present, the addition of the other does not further affect vegetation dynamics in a significant way.
FOREST VEGETATION IN THE TECUCI PLAIN (GALATI COUNTY)  [PDF]
OPREA ADRIAN
Journal of Plant Development , 2004,
Abstract: In this paper, the forest vegetation in the Tecuci Plain (Galati County) is presented. There have been identifyed nine vegetal associations, framed out in four Classes, five Orders, and seven Alliances of vegetation. Thus, the forest vegetation is installed along the rivers, on the sand dunes, or on the hills in that region. Every association, in this paper, is accompanied by: a diagnosis, a live form’s spectrum, a fitogeographical spectrum, and a phytosociological table. Also, there are cross-references to the most significantly papers, in relation to this vegetation of the Tecuci Plain.
Multivariate analysis of vegetation of the salted lower-Cheliff plain, Algeria
Ababou, Adda;Chouieb, Mohammed;Khader, Mohammed;Mederbal, Khalladi;Saidi, Djamel;Bentayeb, Zineddine;
Boletín de la Sociedad Botánica de México , 2009,
Abstract: the main objectives of this study were to identify the edaphic factors that could be related to vegetation distribution in the lower-cheliff plain (35.750° - 36.125°n, 0.5° - 1°e) one the largest salted plains of northwestern algeria and to establish the relationships between these soil factors and the main plant communities. soil and vegetation data were obtained from 133 relevés. species in chenopodiaceae and asteraceae were dominant in the salted plain. soil variables measured included electrical conductivity, elevation, soil texture, soil structure, organic matter, caco3, ph, ca++, na+, cl-, camg and color of soil. multivariate analyses including detrended correspondence analysis (dca) and redundancy analysis (rda) were performed to analyze the collected data. the results showed that the vegetation distribution pattern was mainly related to conductivity and elevation. separation of relevés into groups according to the first two axes of rda provided four vegetation units, each one composed of several diagnostic species with highly significant fidelity value according to fisher's test. the theoretical maps produced by kriging revealed a close relationship between these vegetation units and conductivity.
MULTIVARIATE ANALYSIS OF VEGETATION OF THE SALTED LOWER-CHELIFF PLAIN, ALGERIA  [cached]
ADDA ABABOU,MOHAMMED CHOUIEB,MOHAMMED KHADER,KHALLADI MEDERBAL
Boletín de la Sociedad Botánica de México , 2009,
Abstract: The main objectives of this study were to identify the edaphic factors that could be related to vegetation distribution in the lower-Cheliff plain (35.750° - 36.125°N, 0.5° - 1°E) one the largest salted plains of northwestern Algeria and to establish the relationships between these soil factors and the main plant communities. Soil and vegetation data were obtained from 133 relevés. Species in Chenopodiaceae and Asteraceae were dominant in the salted plain. Soil variables measured included electrical conductivity, elevation, soil texture, soil structure, organic matter, CaCO3, pH, Ca++, Na+, Cl-, CaMg and color of soil. Multivariate analyses including detrended correspondence analysis (DCA) and redundancy analysis (RDA) were performed to analyze the collected data. The results showed that the vegetation distribution pattern was mainly related to conductivity and elevation. Separation of relevés into groups according to the first two axes of RDA provided four vegetation units, each one composed of several diagnostic species with highly significant fidelity value according to Fisher's test. The theoretical maps produced by kriging revealed a close relationship between these vegetation units and conductivity.
The water deficit and aridity indexes in the Capitanata plain calculated by statistical downscaling
Luigi Palatella,Domenico Vitale,Domenico Ventrella,Gianfranco Rana
Italian Journal of Agronomy , 2012, DOI: 10.4081/ija.2012.e3
Abstract: This work describes the results obtained by the statistical downscaling technique for the assessment of changes in precipitation (P), potential evaporation (PE). In turn P and PE are used for computing two indexes of water availability, namely the index of water deficit (WDI) and the aridity index (AI). The analysis is carried out for the Capitanata plain (South-East of Italy) and the A2 scenario of the IPCC Assessment Report 4 (AR4). The large-scale temperature at the 1000hPa level and sea level pressure fields are used as predictors. The local precipitation and potential evaporation time series are used as predictands. The statistical downscaling technique used is based on Canonical Correlation Analysis. A validation procedure of the model is performed and the same technique is used for climatic projections of P, PE and consequently WDI and AI. Climate analysis and projections at this localspace scale is an important issue not only for current water management and planning, but also for improving the irrigation efficiency considering future climate change scenarios.
THE REFERENCE EVAPOTRANSPIRATION AND THE CLIMATIC WATER DEFICIT IN THE WESTERN PLAIN OF ROMANIA, NORTH OF THE MURE RIVER  [PDF]
EUGENIA ?ERBAN
Riscuri ?i Catastrofe , 2013,
Abstract: The Reference Evapotranspiration and the Climatic Water Deficit in the Western Plain of Romania, North of the Mure River. In the present paper, reference evapotranspiration (ET0) was calculated by the method proposed by C.W. Thornthwaite. The climatic water deficit, as the difference between atmospheric precipitation and ET0, has also been calculated and analyzed. In this respect, monthly and annual air temperature and precipitation data from 10 weather stations were used. The analysis period was 1961-2002. The result was that the annual average reference evapotranspiration varies, throughout the Western Plain of Romania, North of the Mure River territory, between 665 and 700 mm. It decreases from south to north and also from west to east, depending on the territorial distribution of the air temperature. The plain territory reveals an annual climatic water deficit between 63 mm in the north of the plain and 171 mm in its south. Therefore, the predominantly agricultural territory of the plain needs a water surplus from irrigation. Only in the east of the plain, at Holod, there is a surplus of moisture.
Investigation of the Vegetation on Saline-alkaline Soils and Marshes of Igdir Plain in Turkey  [PDF]
A. Istanbulluoglu
Pakistan Journal of Biological Sciences , 2004,
Abstract: This study involves in the investigation of halophytic vegetation in Igdir Plain which comprises of partly summer drying and partly prominent saline and alkaline marshes, located near Ararat Mountain in the Eastern Turkey. Six associations and three sub-associations were identified in the plain. Arthrocnemetum glaucum, Halimiono-Arthrocnemetum glaucum and Halocnemo-Salsoletum macrae associations were described in the area where the soil surface was covered by a white salt crust accompanying with extremely sodium, boron and lime contents. Junco-Puccinellietum distans association was widespread in the waterlogged marshes area of the plain while Panderino-Tamericetum parviflorae association prevailed on the soils containing small amount of salt and lime, and having no alkalinity and acidity problem (i.e. neutral in pH). Kochio-Schismetum arabicus was seen in the soil showing the characteristics of no salinity and low alkalinity problem and containing small amount of lime. This area was the transition zone between the wind erosion and highly saline and alkaline soils. All these associations, except Arthrocnemetum glaucum, were described in this study for the first time. Junco-Puccinelliatum distans association was included in Puccinellio-Salicornion europae alliance of Salsola-Aeluropetalia litoralli order. The other associations were grouped under Alhagio-Suaedion microphyllae alliance that was identified in this study for the first time.
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