ABSTRACT
The effectiveness of a Geographical Information Systems cost-distance tool for detecting landscape permeability in relation to the movement of pests in olive landscapes was established. The simplification of agricultural systems is linked to an increased incidence of pests on crops. Therefore, it is important to understand the impact of different land uses surrounding olive groves on pests. In this work, we analysed the effect of the structure of the olive landscape on the movement of two main olive pests-the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae) and the olive moth, Prays oleae (Bernard) (Lepidopetera: Praydidae). We applied linear mixed effects models to analyse the relationship between pest abundance and cost-distance, using different hypotheses to evaluate those land uses that are favourable or unfavourable for the movement of these pests. The results show that this methodology is effective in detecting possible unfavourable land uses with a barrier effect, such as woodland and artificial land uses, and favourable land uses with a corridor effect such as olive groves. Whether other land uses, such as scrubland or riverbanks, act as a barrier or corridor depends on the pest and its life cycle stage. The effect that different land uses have in maintaining low levels of pest populations and ensuring the long-term sustainability of these agricultural systems are discussed. The implications of landscape permeability for the physical structure of the landscape and the dispersal of organisms, and the potential of that landscape to impact the continuous flow of natural processes are also addressed.
Subject(s)
Olea , Tephritidae , Animals , Crops, Agricultural , Environmental Monitoring , Spatial AnalysisABSTRACT
With the aim of obtaining an index of coastal water quality, a methodological procedure based on numerical classification and discriminant analysis is presented. The procedure was applied to nutrient data (ammonia, nitrite, nitrate, and phosphate) analyzed along the coastal waters of a Spanish tourist area. Using numerical classification, three levels of nutrient loading were revealed, characterizing oligotrophic, mesotrophic, and potentially eutrophic waters. Discriminant analysis was shown to be an effective methodological tool in the discrimination between trophic groups. For every group, the discriminant procedure generated the centroids. The centroids representing oligotrophic and potentially eutrophic conditions were used to establish the two extremes of the continuum of mesotrophic conditions in these coastal waters: Standardizing values from -1 to 1, the centroids for oligotrophic and potentially eutrophic waters yielded an interval that defined the range of mesotrophic conditions. This interval is proposed as a water quality index. The ability of the coastal water quality index to successfully predict mesotrophic conditions was proved with random samples.
Subject(s)
Eutrophication , Recreation , Water Pollutants/analysis , Water Supply/standards , Environmental Monitoring , Forecasting , Quality Control , Reference ValuesABSTRACT
En 1986 se inició el análisis ecológico de la cuenca inferior del río Bermejo a cargo del Grupo de Estudios sobre Ecología Regional. Los estudios realizados tanto a nivel global como sectorial permiten, en primer lugar, describir los elementos estructurales del sistema para establecer las relaciones e interacciones entre estos componentes. El conocimiento gradual del funcionamiento de esta cuenca es la base para formular propuestas de manejo y para evaluar las tendencias del sistema en respuesta a la intervención antrópica
Subject(s)
Argentina , Hydrographic Basins , Water Resources PlanningABSTRACT
En 1986 se inició el análisis ecológico de la cuenca inferior del río Bermejo a cargo del Grupo de Estudios sobre Ecología Regional. Los estudios realizados tanto a nivel global como sectorial permiten, en primer lugar, describir los elementos estructurales del sistema para establecer las relaciones e interacciones entre estos componentes. El conocimiento gradual del funcionamiento de esta cuenca es la base para formular propuestas de manejo y para evaluar las tendencias del sistema en respuesta a la intervención antrópica
