Impact of thinning on the water balance of a catchment in a Mediterranean environment

Abstract

A study on the impact of silvicultural practices on the water balance was carried out in a watershed in Calabria, southern Italy, the prevalent cover of which is Calabrian pine stands. A thinning was carried out in 1993, which removed 50% of the total number of trees (about 30% of the basal area), and the catchment hydrological response before and after the intervention was compared. After thinning, differences were observed in yearly runoff, with a significant increase in groundwater flow during spring and summer. In light of this evidence, we assume that silvicultural interventions can contribute significantly to improve water resources management, particularly in regions with a long dry season, as in the Mediterranean area.Key words: Pinus laricio, runoff, small catchment, thinning, water resources management L'impact des interventions sylvicoles sur le bilan hydriques a été étudié en un bassin-versant boisé, en Calabre (Italie méridionale), dominé par des peuplements de pin laricio. En 1993 un élagage fut effectué, emportant l'élimination de 50% du nombre total des arbres (correspondant à environ 30% de la surface terrière) et la réponse hydrologique du bassin fut comparée avant et après l'intervention. Les résultats ont montré que l'élagage a induit quelques différences significatives sur le ruissellement annuel, avec une augmentation assez remarquable de l'écoulement souterrain surtout au printemps et en été. Sur la base de cette évidence, il est très vraisemblable que les interventions sylvicoles peuvent notablement contribuer à l'amélioration de l'aménagement des ressources hydriques, surtout dans des régions caractérisées par une longue saison sèche comme la région méditerranéenne.

Root Biomechanical Traits in a Montane Mediterranean Forest Watershed: Variations with Species Diversity and Soil Depth

“…The Typic Xerumbrepts are variable in thickness, from several centimeters to over a meter, with a dominant sandy texture; the presence of the granite bedrock is common in the most eroded areas. The Ultic Haploxeralfs are moderately thick with a silty clay loam texture [34]. The study area is strictly uniform from a geological point of view.…”

“…Mean annual precipitation at the Bonis site is 1179 mm and mean annual air temperature is 9 • C [33]. Acidic plutonic rocks [34] underlie two types of soils (Typic Xerumbrepts and Ulpic Haploxeralfs) in the catchment. The Typic Xerumbrepts are variable in thickness, from several centimeters to over a meter, with a dominant sandy texture; the presence of the granite bedrock is common in the most eroded areas.…”

Using 137Cs measurements to establish catchment sediment budgets and explore scale effects

“…These areas are highly susceptible to erosion during periods of heavy rainfall. Geologically, the catchment is underlain by acid plutonic rocks (Callegari et al , 2003) that support sandy soils characterized as Typic Xerumbrepts and Ulpic Haploxeralfs. The climate of the area is typical of that of the mountain areas of Calabria, with a short dry period in summer and rainfall almost uniformly distributed though the period extending from September to April.…”

Mediterranean water resources in a global change scenario

“…Mountains are also affected by changes in water demand from human activities (new urbanizations, sky resorts and snow making devices etc) and by intense modifications in plant cover and land uses including i) rapid deforestation as a consequence of overexploitation and overgrazing in developing countries, and forest fires; and, ii) afforestation processes as a consequence of land abandonment and reforestation activities, especially in developed countries. Such changes in vegetation cover affect the water balance because of effects on evapotranspiration and interception rates (Joffre and Rambal, 1993;Llorens et al, 1995Llorens et al, , 1997Cosandey et al, 2004;David et al, 2006;López-Moreno and Latron, 2008), soil moisture dynamics (Correia, 1999;Maestre and Cortina, 2004), and the recharge of aquifers (Callegari et al, 2003). For these reasons, changes in land cover, particularly in the mountains, are as important as climatic variability in explaining the observed hydrological alterations and in assessing future water availability in the region.The present work reviews the main findings on the effects of climate fluctuations and land use changes on water resources of the Mediterranean region.…”