Silviculture and Cinegetics Review - Societatea Progresul Silvic

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phenomena of digression. In the subsidence plains the pedophreatic layer is situated at depths between 0.5- 5.0 m. This intervenes directly in the process of pedogenesis. The pedophreatic water regimen is influenced by damming and drainage. In the piedmont plains the groundwater has a maximum depth ranging from 5 to 10 m. The climatic factors are to a large extent determined by the geographical location of the place taken into consideration (latitude and longitude). For the plain the exposure is of little effect. The Banat territory is located between 44 0 27’ - 46 0 48’ north latitude and 20 0 15’- 22 0 52’ east longitude. For the area under study (fig.1) there could be defined, depending on thermal resource, the following altitude zones: - I. less than 100 m, average annual temperatures above 11.1 0 C; - II. 101-200 m, average annual temperatures between 10.1 0 C-11.0 0 C. For the cold season (winter) must be noted that in the high plains (contact area between lowlands and hills), frosts are more severe than in the lowest parts of the plain of digression. The number of frost days is often less than 90 days in the Banat Plain. In the Banat Plain, the nightly thermal threshold of 16 0 C is the limit at which the warmth-loving plants can optimally grow and develop. Rainfall is distributed differently on the surface under study, as shown in tab.1, and like in the case of the temperatures, there can be defined two altitudinal zones relative to the annual rainfall: - I. under 100 m, average annual rainfall under 600 mm; - II. 101-200 m, average annual rainfall between 601- 700 mm. The number of days with annual precipitation in the subsidence and digression plain ranges from 105 days at Denta and 133.3 days at Lugoj. In the high plain the number of days with annual precipitation ranges from 110 at the subsidence contact area to 130 days at the connection with the piedmont hills (in the center part 120 days were recorded). Generally, the average precipitation ranges between 550-600 mm in the plain area. The humidity deficit is of about 234 mm. The De Martonne indexes have values between 25-27 and even lower. The aridity indexes have aproximatively lower than 30 values in the western side of the Banat Plain, direction Miniş (30.0), Timişoara (30.2), Denta (28.7). At Sinnicolaul Mare (25.8) and Jimbolia (27.2) they have lower values, and towards the hills area they have higher values (Făget 36.0, Caransebeş 36.3, Bocşa Montană 41.4 and Oraviţa 44.0). Yearly potential evapotranspiration calculated by the Thornthwaite method, for the period 1896-1955, is higher than the average annual precipitation at the following stations: Sânnicolaul Mare (P.m.a.-536; E.T.P.-696), Jimbolia (P.m.a.-569; E.T.P.-695), Timişoara (P.m.a.-570; E.T.P.-698) and Miniş (P.m.a.-632; E.T.P.-697) and lower at Lugoj (P.m.a.- 605; E.T.P.-534). For the climate with a dry season, specific for the Banat Plain, the ground water reserves are being depleted gradually through evapotranspiration and its consumption by plants. The water loss is compensated by rainfall, but with the water supply depletion a net deficit of precipitation begins, the evapotranspirations consumes the current rainfall, leaving an extra demand of the atmosphere, unsatisfied by these precipitations. The precipitations deficit of this period compared to the evapotranspiration expresses quantitatively the dry character of the climate and soil, resulting in a need for crop irrigation. In the Banat Plain, an amount of rainfall during May, June and July that is lower than 100 mm leads to a compromise of the crops. The results of calculations by the three methods of drought indexes (Wehry) for a period of 4 years are presented in Table 1. From these calculations it results that out of the four years analyzed, three are dry, among them 1992 being very dry. The results demonstrate the need for irrigation and of installation of field protection forest belts in this area. Thus the P.A.I. curve drawn by the Hungarian researchers for the dry part of Hungary includes the Banat Plain as well (as part of Pannonian Field). This is confirmed by the results of calculations made using the indexes used in Romania, as shown in Table 1. The specific aspects of the steppe formation phenomena that are characteristic to the Banat Plain are a consequence of the reduction, in recent times, of the amount of precipitations, in conjunction with the lowering of the groundwater from hydro ameliorative works (sometimes oversized) and of the alternation of the air masses from different directions (as we shall see below) which, at certain wind speeds, increase evapotranspiration. To characterize the movement of the air in the plain 17
area, the following meteorological stations were chosen: Timişoara, Sânnicolau Mare, Banloc and Lugoj. Wind frequency analysis on the 8 directions shows that the main directions are S and SE as follows: Lugoj (23.7 % - SE), Banloc (17.8 % - S) and Sânnicolau Mare (16.7 % - S); on the other hand at Timişoara it is NW (13.0 %). The predominant direction (S) at Sânnicolau Mare and Banloc, indicates a southern circulation in the plain area of Banat, and the predominant direction at Lugoj (SE – 15.9 %) is explained by the placement of the village in the Timiş valley, which flows from SE to NW. The highest values for calm are recorded at Lugoj (44.9%) and Timişoara (40.7%), which may be explained by the placement of the stations. Thus, the Lugoj meteorological station is situated on the Timiş valley, surrounded by the hills of Lugoj and Buziaş. Timişoara meteorological station is located near a forest (eastern side) and is surrounded by buildings on the other sides. Table 1. Drought indexes for 1990, 1992, 1993 and 1994 in different zones of the Banat Plain (by Wehry) P.A.I. Hydro climatic Index Climatic Index Crt. No. Year Kt Kp Kgw PAI0 PAI Characteristics Ich Characteristics Ic Characteristi cs 0 1 2 3 4 5 6 7 8 9 10 11 Sânnicolau Mare 1 1990 1.00 1.10 1.10 6.84 8.9 Dryness 24.1 Very large deficit 0.54 Extreme dryness 2 1992 1.11 1.24 1.06 9.20 13.4 Extreme dryness 25.9 Very large deficit 0.54 Very dry 3 1993 1.09 0.96 1.09 7.67 8.8 Moderate dryness 26.2 Large deficit 0.61 Very dry 4 1994 1.11 1.02 1.11 5.98 7.5 --- 31.8 Large deficit 0.77 Dry Timişoara 1 1990 1.00 1.10 1.07 5.21 6.1 Moderate dryness 43.9 Large deficit 0.94 Normal 2 1992 1.10 1.22 0.84 6.84 7.7 Moderate dryness 36.5 Large deficit 0.87 Slight dryness 3 1993 1.06 1.00 1.09 7.13 8.2 Dryness 30.0 Large deficit 0.67 Very dry 4 1994 1.10 1.03 1.22 5.36 7.5 Moderate dryness 46.0 Large deficit 1.07 Normal Banloc 1 1990 1.04 1.09 1.22 5.26 7.3 Moderate dryness 39.8 Large deficit 0.85 Slight dryness 2 1992 1.09 1.20 1.14 7.07 10.5 Extreme dryness 30.0 Large deficit 0.71 Dry 3 1993 1.08 0.91 1.14 5.77 6.5 Moderate dryness 33.1 Large deficit 0.73 Dry 4 1994 1.10 0.97 1.20 4.19 5.8 --- 54.8 Moderate deficit 1.23 Humid Lugoj 1 1990 1.00 1.12 1.01 4.63 5.2 --- 52.4 Moderate deficit 1.00 Normal 2 1992 1.07 1.10 0.99 3.95 4.6 --- 54.9 Moderate deficit 1.13 Moderate humidity 3 1993 1.06 0.91 0.99 5.14 5.0 --- 35.4 Large deficit 0.69 Very humid 4 1994 1.07 1.02 0.97 4.17 4.4 --- 52.3 Moderate deficit 1.04 Normal Berini 1 1990 0.93 1.09 1.15 6.75 7.87 Moderate dryness 35 Large deficit 0.65 Very dry 2 1992 1.09 1.23 1.32 9.10 16.10 Extreme dryness 24 Very large deficit 0.48 Extreme dryness 3 1993 1.06 0.98 1.27 5.79 7.64 Moderate dryness 41 Moderate deficit 0.77 Dry 4 1994 1.13 1.05 1.36 3.94 6.36 Moderate dryness 60 Moderate deficit 1.11 Normal From the analysis of the data on average speed by direction it results that in the plain zone, the highest speed is recorded at Banloc (4.6m/s), this station being located in the plain, without major obstacles, and the lowest value is at Lugoj (1.6 m/s). In the most western side, at Beba Veche, the most frequent winds blow from NE / SE on winter (frequency 15% and speed 4-6 m/s), and on summer and spring from SE / NW (frequency 5-10% and speed 4-6 m/s). To be mentioned as an example, that in this town there used to be a windmill producing flour and providing electricity for the mill and the owner’s household. The forest vegetation occupies small areas in the lowlands. Thus, in Timiş county it occupies 923.600 ha, that is 11% of the county surface (the percentage of afforestation in the country is of about 27%, at 40% being considered optimal). Each inhabitant thus has 0.15 ha of forest; the nationwide average is 0.39 ha. Of the total county forests, forests in the plain are at only 9% (in the following forest districts: O.S. Timişoara - 9%, O.S. Lunca Timiş - 3%, and O.S. Lugoj - 12%). Out of this percentage, 5% is the plain mixed hardwood forests with grayish oak and common oak, 2% mixed grayish oak and common oak, and 2% mixed grayish oak and downy oak. Considering the entire surface of the Banat Plain, 18
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Silviculture and Cinegetics Review - Societatea Progresul Silvic

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