Runoff Trends Driven by Climate and Afforestation in a Pyrenean Basin

Abstract

The abandonment of traditional rural life in mountain areas has favoured the expansion of forest in the headwaters of Pyrenean rivers. In this paper, we (i) analyse hydro-climatic trends at the annual and monthly scales in three nested sub-catchments in a central Pyrenean basin and (ii) quantify the relative contribution of climate change and forest cover on the observed changes in runoff. Land use maps indicate an increase in the forest cover in all sub-basins for the period 1987-2009. Non-parametric Mann-Kendall statistic on annual and monthly hydro-climatic data from 1965 to 2009 was used to identify trends in climate and runoff data. To assess the potential influence of the period length, trends were also examined for the 1941-2009 stretch. Upward trends were detected for temperature and potential evapotranspiration, particularly during summer and winter months. Precipitation trends and their significance depended on the length of the period considered, although overall results indicated a decrease, particularly for February and July. The effects of climate change and land cover change on annual runoff were identified by means of a change point analysis. Results indicated that a change in annual runoff took place in the 1980s, suggesting the non-linearity in the relationship between precipitation and runoff, and thus the influence of land use factors. The influence of forest cover was confirmed by comparing observed runoff trends with those resulting from a hydro-climatic model that does not take into account land use changes. Divergence between both trends revealed that forest cover can account for~40% of the observed decrease in annual runoff.

Spatio-temporal variation of throughfall in a hyrcanian plain forest stand in Northern Iran

“…To understand the hydrological cycle and ecosystem services, it is necessary to quantify the role of vegetation in partitioning rainfall resulting in water balance at pedon, slope and watershed scale, and correspondingly the runoff, sediment, nutrients, contaminants and even biota redistribution (Buendia et al, 2016;Cao et al, 2008;Celentano et al, 2016;Cox et al, 2006;Davudirad et al, 2016;Gabarrón-Galeote et al, 2013;García-Fayos et al, 2010;Hosseini et al, 2016;Keesstra et al, 2009;Keesstra et al, 2012;Lal, 1997;Novara et al, 2013;Pereira et al, 2013;Sadeghi et al, 2015;Yousefi et al, 2016;Vega et al, 2005). Improving our understanding about rainfall partitioning in forests ecosystems is very important for studies that focus on forest hydrology to better management and decision making on this vital ecosystems (Ajami et al, 2011;Brecciaroli et al, 2012;Davudirad et al, 2015;Dohnal et al, 2014;Frot et al, 2007;Holko et al, 2009;Xu et al, 2014).…”

The enduring link between forest cover and rainfall: a historical perspective on science and policy discussions

“…Ellison et al support tree planting in Spain to increase precipitation (Ellison et al 2012). This view runs contrary to a significant body of hydrological evidence from Spain (not to mention studies from comparable climates elsewhere in the world) that shows strong correlations between increased forest-cover and decreased water-supply (see for instance Buendia et al 2016;Gallart and Llorens 2003). Supply-side thinking has the potential to reinforce calls for widespread tree-planting in Africa.…”

Agricultural land abandonment in Mediterranean environment provides ecosystem services via soil carbon sequestration

“…SOCag was strongly affected by the type of Bioclimate, increasing from 16.7 Mg ha −1 in the thermoMediterranean to 54.5 Mg ha −1 in the supra-Mediterranean Bioclimate. The impact of climate on soil development, runoff generation, soil erosion, and plant cover is well-known (Anaya-Romero et al, 2015; Buendia et al, 2016;Cerdà, 1998b;Ochoa et al, 2016), but little is known about its impact on soil organic carbon, and this is why the results shown here shed light into the environmental impact of land abandonment. Our findings confirm the results of other investigations that are summarised in Köchy et al (2015aKöchy et al ( , 2015b and quantified by Pabst et al (2016) in Africa or by Willaarts et al (2016) in the Mediterranean.…”