RECONDES
Field Areas
Cárcavo catchment and region, Spain
The main area of study in Spain is the Cárcavo catchment located in Murcia Region.
Climate
The Region of Murcia is located in southeastern Spain. This area is in the rain shadow of the Betic ranges and forms one of the driest areas of Europe. Climate is predominantly Mediterranean semiarid. In the southwestern parts average annual precipitation is a low 180 mm, although at the top of the mountains it is as high as 500-600 mm. Average annual precipitation for most of the region, falls below the isohyet of 300 mm.
Cárcavo catchment is located in a central position in the Region of Murcia. Aridity is not so severe, nevertheless ecosystems have to cope with hydric stress. Average yearly rainfall is just under 300 mm, and average temperature is 16.5°C. Intraannual droughts, typical of Mediterranean climate, are severe. In July and most of August there is virtually no rain, and extended periods of very low or no rainfall 5 months or more in duration are not uncommon. Maximum rainfall is bimodal with peaks in April and October. Autumn rains can be especially intense, producing severe episodes of soil erosion. Maximum intensities over 125 mm day-1 are usual. Potential evapotranspiration, measured by Thornthwaite method is close to 900 mm, although empirical measurements with Pich�� evaporimeter are over 1700 mm. The coldest month is January, with average temperature of 9.5°C and hottest July and August close to 26°C. Frost is relatively uncommon and rarely severe.
Relief, geology, lithology and soils
Cárcavo catchment is basically a marl depression surrounded by limestone ranges north, east and west, and gypsum hills in the south. The ranges east and west reach heights of 750-900 m a.s.l, and are especially abrupt. Minimum height is about 200 m a.s.l. The outlet of the basin drains directly into the Segura River, the major river system of southeastern Spain. The large difference of base level between the Segura River and the Cárcavo catchment is important in driving the erosive processes in the catchment. Indeed 'Cárcavo' in Spanish means gully.
The area is located in a complicated geological setting. It is in the external area of the Betic ranges. The limit between two important units of the Betics, the Prebetic and the Subbetic, is just in the north border of the catchment. The core of the basin are Miocene marls. They are rich in salts, especially gypsum. The Limestone and Dolomite ranges are of Jurassic origin. Between the ranges and the marls there are extensive limestone colluvial deposits. At the base of the ranges, but especially in the southwestern, Triassic materials are dominant. The Keuper formation is the most important and is formed by gypsiferous marls and bulk gypsum.
Because of climate and lithology, as well as historic degradation processes the soils in the catchment are mainly calcic Lithosols on the ranges, calcic Xerosols on the colluvium, marly Regosols on the marls (with abundant gypsiferous facies) and gypsic Xerosols on the Keuper areas. On the whole, they are scarcely developed soils, and problems with excess of salts are important in over a large part of the basin.
Land use
There are two main land uses in Cárcavo catchment: forest land and field agriculture. The first land use is dominated by reforestation with Pinus halepensis, 20-35 years old. They were executed on strips and terraces. Moreover, there is a mature Pinus halepensis forest on North slope of the main range mountain which surrounds the basin.
There are three different stages in the recent agricultural history of the Cárcavo catchment (past 100 years). The first half of the twentieth century was characterized by an extension of traditional dry crops and livestock in the catchment. From 1950s to 1980s agriculture suffered and there was a high rate of land abandonment due to general socioeconomic factors relating to the marginal areas in Spain. Strong migration from the country to the city areas took place at the same time as government reforestation projects tried to recover abandoned land. In the latter years, however, irrigated crops were substituting rainfed croplands.
Nowadays, croplands occupy some plains on marls, wide streambeds and terraces. Dominant crops are olive trees and almond trees. Although, cereal fields, vineyard and fruit trees are present and abandoned lands on wide marly stream beds are also frequent. Livestock is a marginal agricultural activity: there are two small mixed sheep and goat flocks which use the marginal agriculture fields and areas that border the basin. Close to the outlet, the catchment drains into a reservoir which was built in the eighties for the purposes of flood control.
Vegetation
Slope vegetation are mainly composed of Stipa tenacissima communities and dwarf-shrubs with Rosmarinus officinalis, Cistus clusii, Thymus membranaceus on mid and low areas. Harvesting of Stipa tenacissima tussocks was one of the main economic activities in this region of southeastern Spain, so these type of communities has been favoured over the centuries. Slope vegetation at higher altitudes comprises Rhamno lycioidis-Quercetum cocciferae shrublands with Juniperus oxycedrus and Pistacia lentiscus, which are considered the climax vegetation in this mesomediterranean semiarid area. These shrublands are usually mixed with old woodlands of Pinus halepensis. Moreover, scrub species typical of gypsum includes several endemic plants such as Ononis tridentata, Salsola genistoides, Teucrium carolipaui, Helianthemum squamatum, Senecio auricula or Thymus zygis subsp. gracilis, etc. are common, being frequently dominant vegetation on bare gypsum-slopes.
Vegetation in channels and gullies is characterized as alternating between bare ground on eroded sections and patches of riparian, saltmarsh or halo-nitrophilous semiarid vegetation. Riparian galleries and thickets on gullies and concave hillslopes of upper areas are characterized by Nerium oleander, Rhamnus lycioides and Pistacia lentiscus tall shrubs, with some scrub species such as Anthyllis cytisoides, Rosmarinus officinallis, Cistus sp. pl., etc.; Brachypodium retusum perennial grass forms high-cover meadows not only below the Pinus halepensis canopy, but also beneath scrub canopy. Tamarix canariensis thickets and riparian galleries on temporary inundated soils are common, principally on silty beds up-waters of check dams in marly ephemeral streams. Down-water of check dams are frequent temporary ponds dominated by Juncus and Scirpus tall rushes, with reedbeds of Phragmites australis and Limonium delicatulum on margins.
Nevertheless, most usual vegetation on marly ephemeral streams and gully bottoms is characterized by patches of low-cover meadows, scrubs and grasses communities, with Moricandia arvensis, Polypogon mospeliensis, Bromus sp., Diplotaxis harra subsp. lagascana, Pipthaterum miliaceum, Plantago albicans, Dorycnium pentaphyllum, Salsola genistoides, Brachypodium retusum, etc., alternating with scarce individuals of Nerium oleander and Tamarix canariensis. Moreover, salt steppes associations rich in perennial, rossete-forming Limonium sp. and saltmarsh fringe formations of Lygeum spartum are frequent. Finally, gypsiferous rocky gullies are dominated by Nerium oleander riparian galleries with Phragmites australis, Saccharum ravennae on beds and gypsum scrubs with Ononis tridentata, Salsola genistoides, Thymus membranaceus, etc., on banks.
Orcia catchment and region, Tuscany
The Italian study areas chosen comprise two smaller subcatchments of the Orcia Catchment, the Landola and Scalonca subcatchments both located in the Province of Siena.
Climate
The climate of the Province of Siena is characterized by a high variability due to the differences in morphology and local elevations. The heights above sea level range from about 300 m of the river valley floors to the 1,738 of Mount Amiata, with the nearly 1,000 m a.s.l. of Chianti and Cetona mounts. The presence of both Amiata, in the south west part of the area, and Chianti-Cetona mounts ridge, in the north-east part, largely affects the climatic characteristics of the area, with the highest precipitations (above 1,000 mm on average, and up to 1,500 mm on Mount Amiata), and lowest mean annual temperatures (lower than 12°C, and around 9°C on Mount Amiata), localized along the two ridges at the higher altitudes, and with a relatively arid and warm zone in the Orcia river valley bottom (mean annual temperature of about 14°C and average precipitations of less than 600 mm).
Geology, lithology and soils
The basin of the Orcia River is a sort of rectangle delimited by the Mt Cetona ridge (east), the relief of Montalcino (North), Mt Amiata (West) and the peak of Radicofani (South). The geological history of valley is characterised by the deposition of continental and marine sediments in the Pliocene during a marine ingression that followed a tectonic distensive phase. The continental and marine sediments buried the pre-neogenic basament of limestone (Trias) and allochtonous shale and clays formations (Oligocene-Miocene) along the E-SE side of the area. During the Late Pliocene and throughout the Pleistocene an intense uplifting produced a complete emersion and an intensive erosion of the valley ridges and previous Pliocene marine sediments and the filling of the whole valley floor.
The last tectonic phase in the Pleistocene was also accompanied by an intense magmatic activity of Radicofani (1.3-0.003 My b.p.) and Mt Amiata (0.303-0.287 My b.p.), both characterised by a prevalent acid magmatism that covered part of the valley sediments with lava flows and piroclastic deposits. A review of the geological studies conducted in the area is given in Colica (1997).
The Pliocene sediments are characterized by intense erosion phenomena which lead in certain morphological conditions to the formation of badlands, known as calanchi and biancane. The former are small hydrographical units, with steep, eroded slopes, often subdivided into several secondary valleys separated by sharp ridges. The second are dome-shaped forms, generally less than 20 m high, sometimes isolated, but more often grouped into fields ("campi"), and typically with the steeper southern side lacking vegetation and the northern covered by a scanty herbaceous vegetation (Alexander, 1982; Guasparri, 1978; Mazzanti and Rodolfi, 1988; Rodolfi, 1991).
Soil types depend on the lithotype on which they develop and on their management and position on the slope: Inceptisols on the homogeneous clay sediments of the hills that characterize the lower part of the valley - and on the large and rounded divides, Entisols along the slopes, and Vertisols in the valley floors. This type of succession can be found in the biancana badlands that characterize this landscape. This ideal distribution is perturbed by present (and previous) land use. Usually cultivated soils are more eroded than soils under more 'natural-like' conditions. Reclaimed soils (i.e. soil in area that previously were badlands) are even more eroded. Still on Pliocene formation, near Radicofani, where slope gradients are much steeper and calanchi are a common landscape feature, Inceptisols can be found on conglomerates or on sandy clays on gentle slopes, otherwise Entisols dominate. Alfisols can only be found on the terraces of the river Formone (a tributary of the river Orcia) and on conglomerates and sands outcropping along the borders of the basin. Still Inceptisols, disturbed by erosion and mass movements, can be found on the shales and clays of the Allochtonous Complex.
The Montalcino territory has been formed in different geological eras, and presents extremely variable characteristics. For this reason, it is difficult to make generalization about its rocks and soils. The lowest areas consist of soils formed by the deposit of alluvial material with a deep rooting layer, dating from the Quaternary Period. Further uphill, on the marine sediments, soils are mainly clayey and enriched by calcareous fossil material, often rather thin, due to the severe erosion. In upper part of the territory soils are moderately stony and sandy, rich in lime, mingled with wide areas with clayey and stony soils.
Land use
Agriculture plays an important role in the economy of the Province of Siena. A large part of the territory is covered by woodland; less than 10% is planted in vineyard and olive grove, which are nevertheless the main profitable crops of the cultivated area; the remainder is mainly cultivated with grains, pastures and other cultivations.
In Orcia river valley arable lands (mainly winter wheat and winter barley) dominate on Pliocene clays. Pastures (sheeps and some horses at present, also cattle in the recent past) are spread over badlands and nearby erosion threatened areas. Irrigated crops such as maize and sunflowers are located in the alluvial plains. Vineyards and olive groves are found on Pliocene sands and conglomerates and on the shales of the Allocthonous Complex. Woods, of different types and composition according to climatic and edaphic conditions, are diffused on the steeper zones and at the higher altitudes. Re-afforestation of coniferous species is frequent in badland areas as a soil conservation practice.
Vegetation of the preserved biancane and calanchi badland environments
Both biancane and calanchi badlands are characterized by successions of depositional and erosional zones with quite distinctive qualities. This is reflected on the vegetation characteristics (De Dominicis et al., 1991). Obviously, as the two badland types are different, these differences are present in the plant associations too.
In the biancane badlands (Chiarucci et al., 1995a; Maccherini at al. 1996b), where the erosion/sedimentation dynamics is more active, a pioneer paucispecific vegetation, rich in annual species of Thero-Brachypodietea, and in halotolerant species, is found. In basal micropediments, where the sedimentation dynamics is strong, the vegetation is that typical of Parapholido-Artemisietum cretaceae formation; where there is sedimentation on the lower slopes Bromus erectus, characteristic of more evolved grassland, is also found. Particularly, when the pediment is isolated from the biancana slope the presence of Artemisia cretacea, Poa bulbosa and Podospermum laciniatum grows and species characteristic of more evolved stages, such as Dactylis hispanica, Linum strictum and Scabiosa columbaria, can be found. On biancana domes and ESE facing sides the dominant species are Bromus erectus, Aster lynosyris and Linun strictum ssp. corymbulosum. In wetter and cooler zones, as impluvium lines and slope bottoms, close grassland are dominated by Elytrigia atherica. On abandoned fields and on NW facing biancana slopes vegetation is dominated by Dactylis hispanica and Phleum bertolonii. On more stable sites, with relatively more evolved soils, also more evolved coenosis, with a different degree of shrubs cover, dominated in the grass layer by Bromus erectus, are found. On the domes of the more stable and taller biancane and steady surfaces, a vegetation with a lower number of species is found, differentiated by the presence of Lotus corniculatus and Dorycnium pentaphyllum ssp. erbaceum; in some cases a low scrub cover is also developed with Spartium junceum. In hydrographic impluvia or at footslopes Spartium junceum, Pyrus amygdaliformis, Crataegus monogyna, Prunus spinosa and sometimes Ulmus minor are found.
In the calanchi landscape the pioneer vegetation (Maccherini et al. 1998), i.e. Parapholido and Artemisietum cretaceae, is present where erosion is severe. Deposition areas are characterized by herbaceous association dominated by Phalarido coerulescentis and Elytrigietum athericae or Dactylis hispanica, Hedysarum coronarium and Phalaris coerulescens. Bromus erectus and Brachypodium rupestre dominated grasslands are present in several morphologies. Ulmus minor and Quercus pubescens and Quercus cerris are present along impluvia on original surfaces.