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INDICATORI AI PEDODIVERSITĂŢII ÎN CÂMPIA BĂRĂGANULUI CENTRAL

INDICATORS OF PEDODIVERSITY IN THE CENTRAL BĂRĂGAN PLAIN

ALINA GHERGHINA, MARIUS EFTENE, AMELIA ANGHEL, FLORINA GRECU

Keywords: spatial pedodiversity, indicators, soil cover, Central Baragan Plain

REZUMAT

Conceptul de pedodiversitate se referă atât la modul de formare a solurilor (diversitate genetică), cât şi la modelele diferite de dispunere a lor în teritoriu (diversitate spaţială) şi reflectă atât modul geometric de distribuţie în teritoriu a solurilor cât şi deosebirile calitative dintre solurile componente ale învelişului de sol (Florea, 2009). Învelişul de sol al Câmpiei Bărăganului Central a fost analizat din punct de vedere morfometric, fiind calculaţi şi interpretaţi următorii indicatori ai pedodiversităţii: variabilitatea, ponderea solurilor, indicele topopedogeografic, mărimea arealelor, suprafaţa medie şi indicele de complexitate. Valorile acestor indicatori au fost calculate pe baza hărţii solurilor la scara 1:200.000 şi reflectă influenţa factorilor pedogenetici în formarea solurilor.

În Câmpia Bărăganului Central, la nivel de clasă de sol, predomină clasa cernisoluri, cu 87,76 %, urmată de clasele protisoluri, cu 10,81%, salsodisoluri, cu 1,03%, hidrisoluri, cu 0,24% şi antrisoluri, cu 0,15%.

ABSTRACT

The concept of pedodiversity refers both to the formation of soils (genetic diversity) and to the different patterns in territory (spatial diversity) and reflect the qualitative differences between the components of the soil cover (Florea, 1997, 2009).

The soil cover of the Central Plain Baragan was analyzed from morphometric point of view. Have been calculated and interpreted the following pedodiversity indicators: variability, weight, topo-pedo-geographical index, size, mean area and complexity index. The values of these indicators were calculated on the basis of soil map scale 1:200.000 and reflect the influence of pedogenetic factors in soil formation.

In the Central Baragan Plain the soil class of Cernisols prevails, with 87.76%, followed by Protisols, with 10.81%, Salsodisols (1.03%), Hydrisols, (0.24%) and Antrisols (0.15%).

INTRODUCTION Pedodiversity express quantitatively differences between the soils patterns

distribution, and refers to the soil type, the surface occupied in territory and the mode of distribution. The concept of pedodiversity refers both to the soils formation (genetic diversity) and to the different patterns in territory (spatial diversity) and reflects the qualitative differences between the components of the soil cover (Florea, 1997, 2009).

Genetic pedodiversity analyzes the soils formation and the indicators expressing the state of development of the soil cover (Demeter and Geanana, 2001).

Spatial pedodiversity indicates the complexity of the soil cover, soil differences (contrast) and the pedogeographical heterogeneity, which are important features of the soil cover assemblage (Florea, 1997).

The purpose of this paper is to briefly describe the indicators which characterize the spatial pedodiversity in the Central Baragan Plain.

The Central Baragan Plain is situated in the south-east part of the country, in the eastern part of the Romanian Plain and overlaps the Ialomita-Calmatui interfluve. The floodplains of these two rivers represent the southern and the northern limits of the plain.

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On the northern part of the plain is developed an Aeolian relief, with large waving areas and elongated Aeolian depressions. On the central and the southern part, the plain incline very slow to the Ialomita meadow and many microdepressionary areas are present.

The parent materials of the soils are loess and loess-like deposits which are covered, in the north part of the plain, with aeolian reworked sands.

The climate is temperate continental with a big degree of continentally, and is characterized by: medium annual temperature less than 10,5° C in the west part (10,4° C) and more than this value in the eastern part of the plain (10,6° C); the July temperatures vary from 22,4° C to the west and 22,7° C to the east, and the January temperatures vary from -3,1° C to the west and -3,2° C to the east. Medium annual precipitations are between 450 and 500 mm (the values decrease from the west to the east).

Natural spontaneous vegetation of the Central Baragan Plain is characteristic to the steppe area; now, the natural vegetation has been replaced by agricultural lands (Gherghina et. .al, in press).

MATERIAL AND METHODS

The soil cover of the Central Baragan Plain was analyzed from morphometric point of view. The following indicators have been calculated and interpreted: the soil variability, the soil percentage, topo-pedo-geographical index, size, mean area and complexity index. The values of these indicators have been calculated using the formulas listed in Table 1, based on soil map scale 1:200.000.

Table 1

Formulas of the pedodiversity indicators No. Indicator Formula

1 Soil variability The number of soil units 2 Soil percentage Ps = Sa/S x 100 3 Topo-pedo-geographical

index Itp =

Azonal soils (%, km2) Zonal soils (%, km2)

4 Mean area Sn = ∑Si/h 5 Complexity index

Ic = )km( 2S

n

The symbols significance in the formulas is as follows:

- Sa - the surface of each soil unit - S - total area of the plain - Si - the area of each soil polygon - h - the number of areas from a soil unit - n - the total number of soil areas.

The soil names were given in agreement with the World Reference Base for Soil Resources (IUSSISRIC-FAO, 2006).

RESULTS AND DISCUSSIONS

Soil variability, defined by the number of soil units in a territory, has value 38 for the Central Baragan Plain, divided as follows: 27 units in the field interfluve and 11 units in the Ialomita meadow (Fig. 2, Table 2).

The soil percentage is calculated by dividing the area of a soil polygon to the total area of the plain.

In the Central Baragan Plain as soil class level, predominant are Cernisols, with 87.76%, followed by Protisols, with 10.81%, Salsodisols, with 1.03%, Hydrisols, by 0.24% and Antrisols, with 0.15% (Fig. 1).

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Fig.1. Percentage share of soil types: a) on the field interfluve and b) on Ialomita meadow

On the field interfluve, the prevalent soil types are Chernozems, with 95.69%

followed by Arenosols with 2.65%, Solonetz with 0.79%, Solonchaks, 0.39 % Kastanozems with 0.29%, and eroded Regosols with 0.18%. On the Ialomita meadow prevalent are Fluvisols (66%), followed by fluvic Chernozems (32%) and Gleysols (2%).

Fig. 2. The soil map of the Central Bărăgan Plain

a b

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Table 2

Numerical features of the soil units

No. Soil units Area Areal

number

Mean area km

2 km

2 %

1 Eutric Arenosols and cambic Chernozems 83.83 2.50 15 5.59

2 Eutric Arenosols and Sands 5.21 0.16 2 2.60

3 Calcaro-calcic Kastanozems 9.78 0.29 1 9.78

4 Calcaro-calcic Chernozems 74.63 2.22 14 5.33

5 Calcaro-calcic Chernozems (on aeolian relief) 11.24 0.34 1 11.24

6 Calcaro-calcic Chernozems (vermic) 247.84 7.39 10 24.78

7 Calcic Chernozems (vermic) 735.42 21.92 35 21.01

8 Calcic Chernozems with shallow groundwater 442.49 13.19 56 7.90

9 Calcic Chernozems and haplic Chernozems, on aeolian relief 52.27 1.56 5 10.45

10 Calcic Chernozems and haplic Chernozems, with shallow groundwater (on aeolian relief) 44.52 1.33 2 22.26

11 Calcic Chernozems (eroded phase) 25.84 0.77 14 1.85

12 Haplic Chernozems 545.63 16.26 39 13.99

13 Haplic Chernozems with shallow groundwater 520.76 15.52 21 24.80

14 Cambic Chernozems (on aeolian relief) 242.73 7.24 24 10.11

15 Haplic Chernozems, with shallow groundwater (on aeolian relief) 43.48 1.30 8 5.44

16 Haplic Chernozems, eutric and haplic Arenosols (eroded phase) 11.10 0.33 1 11.10

17 Gleyic - Haplic chernozems 51.87 1.55 8 6.48

18 Haplic Chernozems and luvic Chernozems (in microdepressions) 11.76 0.35 28 0.42

19 Haplic Chernozems and luvic Chernozems with shallow groundwater (in microdepressions) 12.41 0.37 14 0.89

20 Gleyic Chernozems 105.65 3.15 64 1.65

21 Gleyic-salic Chernozems 20.12 0.60 16 1.26

22 Hyposodic Chernozems 10.36 0.31 9 1.15

23 Haplic Solonchaks and endosalic Solonetz 13.14 0.39 41 0.32

24 Haplic Solonetz 0.81 0.02 20 0.04

25 Haplic Solonetz and haplic Solonchaks 2.94 0.09 14 0.21

26 Haplic Solonetz 22.86 0.68 20 1.14

27 Haplic Regosols 5.97 0.18 10 0.60

28 Water bodies 6.62

29 Bogs 3.64

Total field interfluve 3364.92 86.80 492 6.82

1 Haplic Fluvisols 64.68 12.95 10 6.47

2 Haplic – gleyic Fluvisols 0.26 0.05 4 0.07

3 Haplic - salic Fluvisols 0.37 0.07 1 0.37

4 Eutric Fluvisols 139.91 28.02 23 6.08

5 Gleyic Fluvisols 96.69 19.36 25 3.87

6 Salic Fluvisols 25.84 5.17 9 2.87

7 Calcaro-calcic - fluvic Chernozems 9.76 1.95 2 4.88

8 Gleyic-fluvic chernozems 122.88 24.61 22 5.58

9 Hyposalic-fluvic chernozems 19.82 3.97 7 2.83

10 Hyposalic-fluvic - gleyic chernozems 10.08 2.02 2 5.04

11 Fluvic gleysols 9.10 1.82 8 1.14

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12 Water bodies 0.56

Total meadow 499.95 12.92 113 4.42

Total 3864.87 100 625 6.39

Calcic Chernozems occupies the largest area (735.42 km2), respectively 21.92%,

followed by haplic Chernozem (545.63 km2), with 16.26% and haplic Chernozem with shallow groundwater (520.76 km2), with 15.52%. The smallest polygons are occupied by haplic Solonetz (0.81 km2), with 0.002% and haplic Solonetz associated with haplic Solonchaks (2.94 km2), with 0.09% (Fig. 2).

In the Ialomita meadow haplic Fluvisols occupy the largest area (139.91 km2), with 28.02%, followed by gleyic-fluvic chernozem (122.88 km2), with 24.61%. Haplic-gleyic Fluvisols unit has the smaller area (0.26 km2), with 0.05%, followed by haplic-salic Fluvisols (0.37 km2), with 0.07%.

The mean area is the ratio between the amount of each soil polygon included in a soil unit and the number of polygons.

In the Central Baragan Plain the mean area of the soil units is 6.39 km2. On the field interfluve the value is slightly higher, 6.82 km2 respectively, due to reduced variability of pedogenetic factors, while in the Ialomita Meadow, which presents more varied conditions, the mean area is 4.42 km2.

Topo-pedo-geographical index (Itp) is the ratio between the area occupied with zonal soils and the area occupied with azonal soils. The reference value of the topo-pedo-geographical index is 1. Up to this value, the azonal soils prevail in a territory (Florea et.al., 1996).

The azonal soils whose formation is determined by local conditions (rocks, excess moisture, slope, age), are represented by Arenosols, Gleysols, Solonchaks, Solonetz and also by gleyic, salic and eroded soil types. Chernozem formed on aeolian deposits and those formed on microdepressions (haplic and luvic Chernozems) are also included in the same category.

The zonal soils are determined by bioclimatic conditions and are represented by Kastanozems and calcic and haplic Chernozems.

For the soil cover of the Central Baragan Plain (interfluvial area), Itp = 778.11 / 2576.56 = 0.3, which means that the zonal soils are prevalent.

On Mohreanu Field the value Itp is 0.23. The zonal soils are represented here by calcaro-calcic and calcic chernozem (both vermic), and the azonal soils are represented by cambic chernozems formed on aeolian deposits.

Itp has the lowest values on the Amara Field (0.05), Urziceni Field (0.10) and Tataru Field (0.14). These subunits have the highest degree of homogeneity of environmental conditions.

The maximum value of Itp is recorded in the Pogoanele Field, respectively 0.69 and is due to the effects of the shallow groundwater (3-5 m) and to diversity of parental materials, respectively aeolian sand in the northern part of the field, sandy loess in the central part and loess deposits in the south. The presence of microdepressions, also, determines the formation of azonal soils.

The complexity index is calculated as ratio between the number of soil polygons and the total area of a territory, and expresses the variety of the soil cover.

In the Central Baragan Plain, the complexity index is equal to 0.16, indicating a reduced complexity of the soil cover. The complexity slightly increases on the Ialomita meadow, to 0.23, and decreases to 0.15 on the interfluve.

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CONCLUSIONS 5. On the Central Baragan Plain the chernozems are prevalent (more than 90% of the

plain area), and calcic and haplic subtypes are the most developed ones. 6. They are associated on the central part of the plain, with solonchaks, solonetz and

gleyic chernozems, as azonal soils, which formation is caused by the shallow groundwater and by the presence of the depressionary areas.

7. The highest degrees of homogeneity of environmental conditions have Amara, Urziceni and Tataru Fields.

8. The great variety of pedological factors in the Pogoanele Field leads to the development of azonal soils, as is reflected in the value of the topo-pedo-geographical index (0.69).

9. The value of the complexity index indicates a reduced complexity of the soil cover in the Central Baragan Plain.

REFERENCES

4. Florea N., 2009 – Pedodiversitate şi pedociclicitate, Bucureşti, 280 p. 5. Florea N.,1997 – Pedodiversitatea genetică a unităţilor teritoriale, indici de

caracterizare şi de analiză geografică, Publ. SNRSS, vol. 29D, Bucureşti, p. 45-51.

6. Florea N., Vespremeanu Rodica, Untaru Georgeta, 1996 – Coeficientul topopedogeografic al învelişului de sol al principalelor unităţi geomorfologice din România, în vol. „Factori şi procese pedogenetice din zona temperată‖, vol.3, Ed. Univ. Al. I. Cuza, Iaşi, p. 89-98.

7. Florea N., Untaru Georgeta, Vespremeanu Rodica, Motelică D., 1997 – Distribuţia cantitativă a solurilor în principalele unităţi de relief din România, Ştiinţa Solului, vol. XXXI, nr. 1, p. 57-70.

8. Demeter T., Geanana M., 2001 – Cartografie pedologică, EUB, 131 p. 9. Gherghina Alina, Eftene M., Ignat P., Grecu Florina, – The influence of parent

material on soil distribution and genesis in the Central Baragan Plain, Publicaţiile SNRSS, 9 p, (in press).

10. IUSS-ISRIC-FAO, 2006 – World Reference Base for Soil Resources, Food and Agriculture Organization of the United Nations, Roma.