George C. Zalidis

Impacts of agricultural practices on soil and water quality in the Mediterranean region and proposed assessment methodology

In countries around the Mediterranean basin, the degradation of soil and water resources is a serious threat for the human welfare and the natural environment as a result of the unique climate, topography, soil characteristics, and peculiarities of agriculture. The detrimental effects of agricultural practices on soil quality include, erosion, desertification, salinization, compaction, and pollution. The resultant impacts on water resources include pollution due to nutrient and pesticide leaching and intrusion of seawater into aquifers. In order to select the appropriate sustainable strategies for preventing those impacts, research should focus on development of an accurate soil quality monitoring system at multiple scales based on a functional evaluation of soils. The objectives of this work are: (a) to point out the peculiarities of the Mediterranean region; (b) to underline the most important impacts of agricultural practices on soil and water quality, in respect to the above peculiarities; and (c) to propose a simple and cost effective methodology for the assessment of soil quality at a watershed scale, based on zones of specific functional interest. The proposed assessment methodology would provide information about the status of the soil resources, correlate soil quality with management and aid with the development of sustainable management practices.

Decision Fusion of GA Self-Organizing Neuro-Fuzzy Multilayered Classifiers for Land Cover Classification Using Textural and Spectral Features

A novel Self-Organizing Neuro-Fuzzy Multilayered Classifier, the GA-SONeFMUC model, is proposed in this paper for land cover classification of multispectral images. The model is composed of generic fuzzy neuron classifiers (FNCs) arranged in layers, which are implemented by fuzzy rule-based systems. At each layer, parent FNCs are combined to generate a descendant FNC at the next layer with higher classification accuracy. To exploit the information acquired by the parent FNCs, their decision supports are combined using a fusion operator. As a result, a data splitting is devised within each FNC, distinguishing those pixels that are currently correctly classified to a high certainty grade from the ambiguous ones. The former are handled by the fuser, while the ambiguous pixels are further processed to enhance their classification confidence. The GA-SONeFMUC structure is determined in a self-constructing way via a structure-learning algorithm with feature selection capabilities. The parameters of the models obtained after structure learning are optimized using a real-coded genetic algorithm. For effective classification, we formulated three input sets containing spectral and textural feature types. To explore information coming from different feature sources, we apply a classifier fusion approach at the final stage. The outputs of individual classifiers constructed from each input set are combined to provide the final assignments. Our approach is tested on a lake-wetland ecosystem of international importance using an IKONOS image. A high-classification performance of 92.02% and of 75.55% for the wetland zone and the surrounding agricultural zone is achieved, respectively.

Using Earth Observation to update a Natura 2000 habitat map for a wetland in Greece.

The European Habitats Directive 92/43/EEC has defined the need for the conservation of habitats and species with the adoption of appropriate measures. Within the Natura 2000 ecological network of special areas of conservation, natural habitats will be monitored to ensure the maintenance or restoration of their composition, structure and extent. The European Space Agencys GlobWetland project has provided remotely sensed products for several Ramsar wetlands worldwide, such as detailed land cover-land use, water cycle and inundated vegetation maps. This paper presents the development and testing of an operational methodology for updating a wetlands habitat map using the GlobWetland products, and the evaluation of the extent to which GlobWetland products have contributed to the habitat map updating. The developed methodology incorporated both automated and analyst-supervised techniques to photo-interpret, delineate, refine, and evaluate the updated habitat polygons. The developed methodology was proven successful in its application to the wetland complex of the Axios-Loudias-Aliakmon delta (Greece). The resulting habitat map met the European and Greek national requirements. Results revealed that GlobWetland products were a valuable contribution, but source data (enhanced satellite images) were necessary to discriminate spectrally similar habitats. Finally, the developed methodology can be modified for original habitat mapping.

Shoot Sr concentrations in relation to shoot Ca concentrations and to soil properties

This work was aimed to investigate whether shoot Sr concentrations of plant species are related to respective Ca concentrations and to soil properties and to compare the Sr-Ca observed ratios (OR), defined as the quotient of the ratios Sr/Ca in shoots and in the soil solution or in the extractable form, among species and soils. Ten pasture plant species were grown in pots (1-L volume) filled with eight soils differing in the various physicochemical characteristics. Each pot received 50 mg Sr except those of the soil with the highest cation exchange capacity (C.E.C.) that received 100 mg Sr per pot. For each soil, shoot Sr concentrations of species were linearly and positively related with the respective Ca concentrations. C.E.C, organic matter content and Ca in the soil solution or in the extractable form were the only soil properties that were related, all negatively, with shoot Sr concentrations. The ratio of extractable Sr and Ca was positively and linearly related with the ratio of Sr and Ca. in the soil solution. OR was affected by both species and soils. Most of OR values of all species in all soils ranged between 0.8 and 1.5, except for the grass Agrostis capillaris which had the highest values for most of soils. This indicates that Agrostis capillaris compared to other species, takes up proportionally more Sr than Ca.

Lake Koronia, Greece: Shift from autotrophy to heterotrophy with cultural eutrophication and progressive water-level reduction

Abstract Lake Koronia, a Ramsar site, is shallow, polymictic, hypertrophic and until recently was aerially the fourth largest lake in Greece. Although exceeding 5 m in the past, lake depth has declined progressively from 3.8 m in 1980 to 6000 μS cm−1 in 1991. Increased phosphate concentrations from the late 1970s (8–45 μg L−1) to the late 1990s (100–1000 μg L−1) document that the previously eutrophic system with a limited littoral zone switched to hypertrophy dominated by massive cyanobacteria blooms. Oxygen saturation of the water column increased progressively from about 80% in 1983 to full saturation about 1993, after which it decreased progressively to only 20% saturation in 1997. In spite of cyanobacteria dominance, community metabolism of the lake switched from progressively increasing autotrophy to rapidly advancing heterotrophy associated with progressive water-level reduction leading to fish extirpation in the lake.

Inventory of Greek wetlands as natural resources

This effort is the first approximation for an inventory of Greek wetlands that will be used to create a national archives of wetland information. The objectives of this study were to a) collect data on characteristics, functions, threats, and positive actions related to the use of wetlands, b) design and develop a data base with the above information, and c) depict part of these data on a digitized thematic map. The project consisted of a) design of a questionnaire that would be easy to understand and fill out, comprehensive, and compatible with data formats of other international data bases (Ramsar Bureau. CORINE Biotopes), b) distribution of the questionnaire, c) data quality control, d) design and development of the data base, and e) depiction of the location of the types of Greek wetlands proportional to their size on a scale of 1∶1,000,000. The results included the publication of the compiled information sheets for 378 Greek wetlands. These data sheets contain information on the location, the area, the most important biotic and abiotic characteristics, the values, the uses, the pressures threatening the wetlands, the legal status, and the positive actions. Additional results included the number and the location of drained wetlands, the preliminary results on the wetland flora of Greece, and a digitized map of Greek wetlands.

Caesium and strontium uptake by two pasture plant species grown in organic and inorganic soils

Caesium (300 mg per pot) or strontium (190 mg per pot) were applied to pots, containing either 1200 g of inorganic or 560 g of organic soil 2, 1 and 0 months before sowing with either Lolium perenne or Trifolium repens. For inorganic soil only and the addition of Cs and Sr at the time of sowing, three levels of K (0, 83 and 166 mg per pot) or Ca (0, 100 and 200 mg per pot) were applied. Changes of extractable Cs were monitored with time in unsown pots. Extractable Cs decreased with time, especially in the inorganic soil. In shoots, harvested 5 months after sowing Cs and Sr concentrations were higher in Trifolium than in Lolium with a trend for lower concentrations when Cs or Sr was applied earlier. Concentrations of Cs were higher in organic than in inorganic soil. The reverse was evident for Sr concentrations. Addition of K tended to decrease and that of Ca to increase shoot Cs and Sr concentrations, respectively.

Integrated Methodology for Estimating Water Use in Mediterranean Agricultural Areas

Agricultural use is by far the largest consumer of fresh water worldwide, especially in the Mediterranean, where it has reached unsustainable levels, thus posing a serious threat to water resources. Having a good estimate of the water used in an agricultural area would help water managers create incentives for water savings at the farmer and basin level, and meet the demands of the European Water Framework Directive. This work presents an integrated methodology for estimating water use in Mediterranean agricultural areas. It is based on well established methods of estimating the actual evapotranspiration through surface energy fluxes, customized for better performance under the Mediterranean conditions: small parcel sizes, detailed crop pattern, and lack of necessary data. The methodology has been tested and validated on the agricultural plain of the river Strimonas (Greece) using a time series of Terra MODIS and Landsat 5 TM satellite images, and used to produce a seasonal water use map at a high spatial resolution. Finally, a tool has been designed to implement the methodology with a user-friendly interface, in order to facilitate its operational use.

Forms and distribution of heavy metals in soils of the axios delta of northern Greece

Abstract Distribution and availability of heavy metals to plants is important when assessing the environmental quality of an area. The objectives of this study, conducted in 1992–1993, were: a) to determine the levels of the heavy metals, cadmium (Cd), chromium (Cr), copper(Cu), lead (Pb), manganese (Mn), nickel (Ni), and zinc (Zn), in the soils of the Axios Delta (a Ramsar wetland site in Northern Greece) so that the degree of pollution could be ascertained, b) to identify the various heavy metal forms present in soils using a fractionation scheme based on sequential extraction, and c) to find possible dependence on soil physicochemical properties. Total heavy metal content of the soils studied was generally higher than the levels reported in the literature for similar soils, suggesting some degree of pollution with heavy metals. The exchangeable forms of the heavy metals, however, were very low indicating that under present conditions, the availability of the heavy metals to plants is at a minimum. Most...

Environmental impacts on Greek wetlands

This study identified the possible impact of anthropogenic activities on the ecological character of Greek wetlands. The objectives of this project were a) to record the anthropogenic activities that caused change in a wetland’s ecological character and assess their intensity for each wetland site and b) to identify the most significant environmental impact on each type of Greek wetland. Nineteen factors of degradation (intensive human activities) were identified and grouped in one of the impact categories according to their most significant direct impact. These degradation factors were grouped into four categories for impact evaluation: change in water regime, depletion of wetland resources, change in water quality, and loss of wetland area.To inventory anthropogenic activities and their possible impact on the ecological character of Greek wetlands, more than 1200 questionnaires were distributed, selected, and processed to compile information. These data for 291 wetlands were compiled into a data base GRIN (GReek INventory) that provides information on the factors of degradation of different kinds of wetlands (deltas, estuaries, lagoons, lakes, reservoirs, rivers, marshes, and springs). The following factors most frequently impacted Greek watlands: a) construction of irrigation schemes and diversion of water courses, causing changes in water regime (12%); b) overpumping, land clearing, and illegal hunting, causing depletion of natural resources (26%); c) agricultural and municipal pollution, causing changes in water quality (54%); and d) establishment of housing facilities and expansion of agriculture, causing loss of wetland area (32%). Change in water regime affected 50% of the springs and 40% of the rivers, natural resources depletion affected 42% of the deltas and 41% of the reservoirs, loss of wetland area affected 60% of the marshes and 52% of the estuaries, while all deltas and 75% of rivers had their water quality impacted.