SOIL COVER IN TUTOVA DRAINAGE BASIN. Învelişul de sol din bazinul hidrografic al Tutovei

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1 Factori şi Procese Pedogenetice din Zona Temperată 9 S. nouă (2010) SOIL COVER IN TUTOVA DRAINAGE BASIN I. C. Stângă, Ana-Maria Iacob Alexandru Ioan Cuza University of Iaşi Învelişul de sol din bazinul hidrografic al Tutovei Abstract This article covers a monographic presentation of the soils from the Tutova drainage basin. The analysis of the pedogeographic assemblage was performed based on the soil surveys of the territories corresponding to Tutova s drainage basin, and completed with field research. The taxonomic classification was done in accordance with the Romanian System of Soil Taxonomy (2003) and the soil map was created at a 1: scale. The zonal soils dominate the region; the Chernisols are on the first rank with a share of 39.95%, followed by Luvisols with a percent of 27.62%. Among the soils with an azonal and intrazonal character, the entic soils are dominant (21.90%), followed by Anthrosols (8.89%) and by Hydrisols (1.64%). Key words: Tutova drainage basin, soil cover, soil mapping INTRODUCTION Tutova drainage basin (68,593.7 ha) is the axial part of the Tutova Rolling Hills, a geographical unit with clearly shaped features. From the geological point of view, the basin belongs to the platform unit (the Moldavian Platform and the Barlad Depression); geomorphologically it belongs to the Barlad Plateau, more precisely the Tutovei Hills. Climatically, the studied area belongs to the wider zone of the transitionaltemperate-continental climate, situated eastside of the Eastern Carpathians. From the hydrological point of view, the limits are more clearly stated on the left side of the Siret River. In terms of biogeography, the temperate silvo-steppe, the oak and mixed forests (even beech forests in the upper basin) offer the main characteristics. The region's pedogeographic cover consists of soils characteristic mainly for the silvo-steppe and the forest domain, to which are added taxonomic units with an azonal and intrazonal character. The typology and specificity of the soil forming processes are controlled by the morpho-bio-climatic complex, to which contributes and the anthropic intervention, extremely visible in the past two centuries. 89

2 Fig. 1. Geographical location of Tutova drainage basin in Romania. The lithologic base is supported by the sedimentary rocks accumulated between Upper Sarmatian and Lower Quaternary, characterized by a texture differentiation on the North-South direction. Therefore, in the upper basin is met a clayey-silty facies, while in the lower one the sandy and sandy-clay deposits prevail. The presence of clays explains the frequency of stagnogleyzation processes, as well as the appearance of the vertic or pelic subtypes of the zonal soils. Marls can contribute to the occurrence of phaeozems, while sandy deposits allow a deeper percolation of the soil and the occurrence of some subtypes of psamic soils. Still, on this general pattern, the lithology is monotonous and it enforces an increased soil cover mosaic. Eluvial deposits, located at the level of crests or on the interstream plateaus, were formed through in situ transformation of the underlying rock, which offers them some sort of homogeneity. Occupying relatively flat surfaces, soil formation is more intense, erosion processes are insignificant (except sheet erosion and wind erosion), and soils evolved on these deposits are characterized by a deep and well-differentiated soil profile. Delluvial deposits are found at the slopes level, and they are sequential and discontinuously transported to the slopes basis by means of sheet and rill erosion or mass movement processes. Because of the morphogenesis /pedogenesis ratio, soils are either in the early stages of formation - Regosols, or they are excessive eroded. At the slopes bases are found prolluvial and colluvial deposits, which are genetically and textural differentiated, but they are spatially and evolutionally juxtaposed. In the upper and middle basin, these contact formations cover the entire major streambed of the rivers that are unable to carry the large amount of material derived from slopes, giving 90

3 birth to colluvial plains, which are extremely fertile when they are not affected by excess moisture. Alluvial deposits occupy a small surface of the basin, particularly along the main valley, but according to current Romanian System of Soil Taxonomy, alluvial soils (7.1% of basin s surface) include as well those soils formed on colluvial deposits (Fluvisols). Recent and current lacustrine deposits occupy insignificant surfaces; on their account (according to RSST 2003) were formed soils with a pronounced character of hydromorphism. The relief implies a South-North differentiation of the bioclimatic factors, simultaneously with the increase of altitude, in a vertical deviation of 400 m. This leads to a differentiation of the soil cover, from mollisols (chernozems, phaeozems) to luvisols (entic and typic luvisols). The boundary of the two classes is situated approximately at about 300 m altitude, with small differences according to local conditions (lithology, slope, exposition, land cover). For mollisols we cannot draw a clear altitude limit between chernozems and phaeozems, the latter being dependent on a larger soil forming complex, including the nature of the parent material. For luvisols however, a conventional limit can be set at about 400 altitudes, which separates the domain of the soils without an elluvial horizon from the one of soils with a more or less developed elluvial horizon. The slope degree plays an extremely important role, leading to both the differentiation of zonal soils, but also to the appearance of some soils with azonal or intrazonal character. Thus, horizontal or slightly inclined surfaces support water infiltration, the leaching of soluble compounds or colloidal fraction, resulting in a faster evolution of soils. The differentiation is extremely obvious both in the centralsouthern part of the basin (in the domain of mollisols), as well as in the upper basin (in the domain of luvisols). Exceptions are those sectors with insufficient internal and external drainage, where the gleyic and stagnogleyic soils meet the requirements for formation. Pronounced slopes encourage the evolution of morphogenetic processes, leading to either the maintenance of soils in incipient stages of formation, or to the degradation of existing soils. In the first case, the slopes are stable, affected by sheet erosion, which determines the beheading of the soil profile, while in the second case, slopes are affected by complex processes of rill erosion and mass movement processes. Water resources have a permanent and crucial role in soil formation, but they enforce (radically influencing the processes of soil formation) distinctively in two ways. First, it is about the influence of aquifers situated over the critical depth, producing thereby gleyzation processes of the soil (gleysols and subtypes of gleyic soils in the alluvial and aluvio-colluvial floodplains). Secondly, due to the clay intercalations from the central-north part, processes of soil stagnogleyzation may occur, reflected by the existence of the stagnic soils subtypes. The biogeographic cover entails the differentiation of bioaccumulation mineralization processes in the forest vegetation, and the grassland, but it also entails 91

4 the control of erosion processes and the adjusting of morphogenesis/ pedogenesis ratio, without imposing distinctive elements that are specific to Tutova drainage basin. Anthropogenic influence is felt both as a reflex of the dominant agricultural land use, frequently inadequate, thereby accelerating the degradation of existing soils by means of intensification of erosion mechanisms (eroded soils), but also as a result of anti-erosion improvements on the slopes (anthrosols). Likewise, the drainage works in the alluvial plains had an important impact in the reduction of humidity excess and the decrement of gleyzation processes. MATERIALS AND METHODS The analysis of the pedogeographic assemblage was performed starting from the soil surveys of the villages territories corresponding to Tutova s drainage basin (elaborated by OJSPA Vaslui and Bacău). These were completed with some field research and laboratory tests, performed due to some research contracts (CEEX 756/2006, CNCSIS 476/2007). The taxonomic classification was done in accordance with the Romanian System of Soil Taxonomy (2003), regardless the date on which the soil studies have been used. The soil map was elaborated at a 1:25,000 scale, having as starting point the soil profiles representative for the studied area. It was created in an informational system, using the TNTmips 7.3 software, program that has been as well used as the basis of statistical processing of soil data. RESULTS AND DISCUSSIONS Analyzing the 1:25,000 soil map drawn on the basis of the representatives profiles included in the soil surveys (1:100000), it can be observed that the zonal soils dominate, mollisols being first, with a share of 39.95% (27, ha), followed by luvisols with a percent of 27.62% (18, ha). Among the soils with an azonal and intrazonal character, the entic ones dominate (21.90%, meaning ha), followed by anthrosols (8.89%, meaning ha) and on the last rank are the hidrisols (1.64%, meaning ha). Entic soils represent a typological entity at an early stage of formation, which occupies an extremely high share of the region (21.90%, meaning ha). Two aspects contribute to this situation: the presence of moderate-high declivity slopes and that of alluvial, alluvial-colluvial and colluvial plains. Regosols ( ha, meaning 14.80% of the basin s surface) occupy stable slopes, with moderate-high declivity, where slow but long-lasting erosion ( geologic erosion ) prevails the pedogenesis processes, maintaining the soil in an overlong stage of early formation. 92

5 Soils in Tutova drainage basin (1:25000) Class Type Subtype Area (hectares) % from Protisols Chernisols Luvisols Hydrisols A nt hri 93 Table 1. % from type % from total class Total *** Total Aluviosols Regosols coluvic Mollic Gleyic Mollic-gleyic Total Calcaric Eutric Mollic Vertic Stagnic Total *** Chernozems Total Calcic Haplic Luvic Phaeozems Haplic-Hyposalinic Total Haplic Greyi-luvic Haplic Luvic Stagnic Total *** Preluvosols Total Haplic Luvisols Luvic Phaeozems Luvosols Stagnic Total Haplic Stagnic Total *** Gleysols Total Mollic Fluvic Lacustrine ares Total *** Anthrosols Hortic

6 Class Type Subtype Area (hectares) Erodosols 94 % from total % from type % from class Total Calcaric regosols Haplic regosols Cambisols (eroded phase) Luvisols (eroded phase) Stagnic Regosols TOTAL According to local conditions the following subtypes were differentiated: eutric ( ha), calcaric ( ha), mollic ( ha), stagnic ( ha) and vertic ( ha). These soils are characterized by a low fertility and high erosion risk in situations of misuse, which is a common in the studied area. Aluviosols occupy hectares, representing 7.1% of the basin s surface, along the main valleys of the upper watercourses, with predominantly colluvial plains up to the place where Tutova flows into Barlad River, where the floodplain has a typically alluvial character. The following subtypes were separated: mollic ( ha), colluvic ( ha), gleyic ( ha), to which the combined mollic-gleyic subtype is added. These soils raise two major problems. First of all, it s about the taxonomic classification at the type s level, the colluvial materials having no alluvial character, according to any definition accepted at an international level (Rusu et al., 2006). Secondly, it s about the installation of the excess moisture and the materialization of gleyzation processes, almost permanently after the drainage works (after 1975), at least in some areas. Chernisols make up the dominant fund of the region, particularly in the centralsouth part, but they are neither missing from the upper basin. Two types of this class are represented in the basin: chernozems, which occupy an area of 16, ha (23.52% of the basin s surface), and phaeozems with 11, ha (16.43%). Chernozems were formed in a silvo-steppe and steppe environment, with multiannual mean temperatures of C, relatively low precipitation ( mm) and a dominant vegetation of grasslands. In the southern part of the basin loess deposits or other sandy and clay-sandy elluvial deposits appear on each relief level from the level of loess-like deposits-covered ridges to the colluvial-prolluvial formations at the basis of the slope, along which they extend to the north. On the slopes they occupy areas with moderate declivity and a slower dynamics of the erosion processes. At a subtype level, a significant share have the Calcic Chernozems, Haplic Chernozems ( ha) and Luvic Chernozems ( ha), other subtypes (hyposalic, vertic, gleyic) having an insignificant share. Phaeozems were formed in a steppe environment, at the shift to the forest domain, with multiannual mean temperatures of 8.0 to 10 C and precipitations of 500-

7 650 mm. According to the RSTS (2003), phaeozems include as well, at the subtype level, a series of soils with intrazonal or azonal character, conditioned by parental material or by excess groundwater humidity. Thus, the former pseudorendzine formed on slighlty consolidated carbonate parent materials, are currently equivalent to Haplic Phaeozems, Calcaric Phaeozems, Stagnic Phaeozems, or Vertic Phaeozems. From this study s perspective, the identification at the type level of some taxonomic units with high risk of gleyzation, stagnogleyzation or installation of excess humidity is easier. At a subtype level, the Haplic Phaeozems ( ha), Greyi-luvic Phaeozems ( ha), Haplic Phaeozems ( ), Luvic Phaeozems ( ha) and Stagnic Phaeozems ( ha), are dominant, other typological entities occupying disjoint, small areas, that were not separated at the level of the created map. Luvisols are specific to the forest domain, and they appear grouped in the central-northern part of the region, under the conditions of higher precipitations and lower temperatures. The more intense fragmentation, specific to the area where these soils occur, as well as the removal of forest vegetation determined the acceleration of morphogenesis processes to the detriment of the pedogenesis ones and it also determined the substitution of these zonal soils with Regosols or eroded soils, extremely characteristics on slopes. Among Luvisols, in the basin s area were identified two types: entic Luvisols, with ha surface (20.55% of basin s surface), and typical Luvisols, totaling , representing 7.07% of the total. Entic Luvisols develop at the basis of forest domain, with average temperatures of 8-9 C and annual rainfall of mm, depending on the conditions of different internal and external drainage. It is essential to ensure a percolation hydric system and the leaching of the clay fraction, forming an argic horizon. The following representative subtypes have been identified: typical ( ha), mollic ( ha) and stagnic ( ha). Typical Luvisols have developing conditions in the upper basins of Studineţ, Iezer and Lipova, as well as Tutova/Zeletin-Pereschiv ridge, generally at altitudes over 400 m. These soils are specific to the forest domain with temperatures that don t exceed 8.5 C, 600 mm annual rainfall and moderate evapotranspiration, elements that allow a more intense leaching of clay and a clearer differentiation of elluvial and illuvial horizons. Percolation is favored by the small declivity, corresponding to interstream plateaus and ridges, while superficial flow is insignificant. At the subtype level, have been identified and mapped only two subtypes: typical ( ha) and stagnic ( ha). At the slopes level, the increase of superficial flow in disfavor of infiltration, allowed the development of solely entic Luvisols, even though there were specific bioclimatic conditions for typical Luvisols as well. Anthrisols are formed and intensively transformed by anthropic intervention, either directly (Anthrosols), or indirectly through an acceleration of morphogenesis processes (Erodosols and eroded soils). These soils occupy a surface of ha, representing 8.89% of the basin surface. In this soil class, the majority are eroded soils ( ha), with an expansion tendency, as a result of land misuse. At a subtype level, have been identified Calcaric Anthrosols ( ha), Haplic Regosols (

8 ha), Cambisols ( ha), Luvisols ( ha) and Stagnic Regosols ( ha). Anthrosols, exclusively hortic ( ha) record an evolutionary tendency of rehabilitation to natural conditions, by abandonment of vineyards and orchards or antierosion works (agro-terraces). CONCLUSIONS Considering the relatively small area of study, it cannot be taken in discussion an actual pedogeographical regionalization. However, given the altimetry and bioclimatic differences, manifested in different limits on a south-north direction, these have imposed a differentiation of the pedogeographic cover. Thereby, the southern part, with lower altitudes, with less than 550 mm rainfall is the domain of mollisols, completed in the to the north, in the upper basin with the domain of luvisols. Likewise, taking in consideration the local traits, there is a differentiation of the pedogenesis processes on the same direction, standing out a higher frequency of salinisation and carbonation processes in the southern part, while, towards north the processes of gleyzation and stagnogleyzation become more frequent. Overall, pedogeographically speaking, the basin looks like a topographic sequence of the argic soils domain strongly modified by human actions. Acknowledgements Financial support for this study was partly provided by the Sectorial Operational Program Human Resources Development through the project POSDRU/CPP 107/DMI 1.5/S/ REFERENCES 1. FLOREA N., MUNTEANU I., Sistemul Român de Taxonomie a Solurilor, Ed. Estfalia Bucureşti, 182 pp. 2. NIACŞU L., Bazinul Pereschivului (Colinele Tutovei). Studiu de geomorfologie si pedogeografie cu privire speciala asupra utilizării terenurilor, Teză de doctorat, Universitatea Al. I. Cuza Iasi, 249 pp. 3. RUSU C., STÂNGĂ I. C., NIACŞU L., VASILINIUC I., Observaţii privind posibilitatea îmbunătăţirii Sistemului Român de Taxonomie a Solurilor (Bucureşti, 2003), Lucrări ştiinţifice vol. 49, seria Agronomie, Ed. Ion Ionescu de la Brad Iaşi (CD) 4. STÂNGĂ I.C., Bazinul Tutovei. Riscurile naturale şi vulnerabilitatea teritoriului, Teză de doctorat, Universitatea Al. I. Cuza Iasi, 242 pp. 5. ***, 1986 Harta solurilor României 1: , foaia Bârlad. 96

9 6. ***, Studiu pedologic. Teritoriul comunei Lipova, OJSPA Bacău 7. ***, Studiu pedologic. Teritoriul comunei Plopana, OJSPA Bacău 8. ***, Studiu pedologic. Teritoriul comunei Iveşti, OJSPA Vaslui 9. ***, Studiu pedologic şi bonitarea terenurilor teritoriului comunal Perieni, OJSPA Vaslui 10. ***, Studiu pedologic şi bonitarea terenurilor teritoriului comunal Dragomireşti, judeţul Vaslui, OJSPA Vaslui 11. ***, Studiu pedologic şi bonitarea terenurilor teritoriului comunal Iana, judeţul Vaslui, OJSPA Vaslui 12. ***, Studiu pedologic şi agrochimic necesar realizării şi reactualizării sistemului naţional şi judeţean de monitorizare sol-teren pentru agricultură al teritoriului administrativ Puieşti, OJSPA Vaslui 13. ***, Studiu pedologic şi agrochimic necesar realizării şi reactualizării sistemului naţional şi judeţean de monitorizare sol-teren pentru agricultură al teritoriului administrativ Voineşti, OJSPA Vaslui 97

PhD Thesis Studinet catchment (Tutova Hills). Pedogeomorphological. Scientific leader Prof. univ. dr. Constantin RUSU PhD student Ana-Maria Iacob

PhD Thesis Studinet catchment (Tutova Hills). Pedogeomorphological study Scientific leader Prof. univ. dr. Constantin RUSU PhD student Ana-Maria Iacob IASI 2013 CONTENTS CHAPTER I. INTRODUCTION I.1. The