Exploring the long-term response of undisturbed Mediterranean catchments to changes in atmospheric inputs through time series analysis

Bernal S., Belillas C., Ibanez J.J., Avila A. (2013) Exploring the long-term response of undisturbed Mediterranean catchments to changes in atmospheric inputs through time series analysis. Science of the Total Environment. 458-460: 535-545.
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Doi: 10.1016/j.scitotenv.2013.04.072

Resum:

The aim of this study was to gain insights on the potential hydrological and biogeochemical mechanisms controlling the response of two nested Mediterranean catchments to long-term changes in atmospheric inorganic nitrogen and sulphate deposition. One catchment was steep and fully forested (TM9, 5.9ha) and the other one had gentler slopes and heathlands in the upper part while side slopes were steep and forested (TM0, 205ha). Both catchments were highly responsive to the 45% decline in sulphate concentration measured in atmospheric deposition during the 1980s and 1990s, with stream concentrations decreasing by 1.4 to 3.4μeqL-1y-1. Long-term changes in inorganic nitrogen in both, atmospheric deposition and stream water were small compared to sulphate. The quick response to changes in atmospheric inputs could be explained by the small residence time of water (4-5months) in these catchments (inferred from chloride time series variance analysis), which was attributed to steep slopes and the role of macropore flow bypassing the soil matrix during wet periods. The estimated residence time for sulphate (1.5-3months) was substantially lower than for chloride suggesting unaccounted sources of sulphate (i.e., dry deposition, or depletion of soil adsorbed sulphate). In both catchments, inorganic nitrogen concentration in stream water was strongly damped compared to precipitation and its residence time was of the order of decades, indicating that this essential nutrient was strongly retained in these catchments. Inorganic nitrogen concentration tended to be higher at TM0 than at TM9 which was attributed to the presence of nitrogen fixing species in the heathlands. Our results indicate that these Mediterranean catchments react rapidly to environmental changes, which make them especially vulnerable to changes in atmospheric deposition. © 2013 Elsevier B.V.

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WeMO effects on the amount and the chemistry of winter precipitation in the north-eastern Iberian Peninsula

Izquierdo R., Alarcón M., Àvila A. (2013) WeMO effects on the amount and the chemistry of winter precipitation in the north-eastern Iberian Peninsula. Tethys. 10: 45-51.
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Doi: 10.3369/tethys.2013.10.05

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The cluster classification of provenances at a site in the NE Iberian Peninsula indicated that in the period of extended winter (December to March, DJFM) fast Atlantic air flows correspond to positive WeMO index (WeMOi), while negative WeMOi are associated to Mediterranean circulations. The amount of winter precipitation was inversely correlated with winter WeMOi. Wet deposition fluxes of marine-derived (Na+, Mg2+ and Cl-) and anthropogenic-derived (NO3 - and K+) ions were significantly (and negatively) related to winter WeMOi. The negative phase of WeMO causes the entry of air masses from the Mediterranean into the Iberian Peninsula, that are enriched with marine ions. For NO3 - this result suggests the advection over the Mediterranean of polluted air masses from southern Europe and the scavenging and deposition of this pollution by rain during WeMO negative phases. This will carry long-range pollutants to the NE Iberian Peninsula, but local pollutants may also contribute, as precipitation events from the Mediterranean (associated to negative WeMOi) may incorporate local anthropogenic emissions that build up during the winter anticyclonic episodes typical of the region. © BY 2013 Author(s).

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Multi-generational long-distance migration of insects: Studying the painted lady butterfly in the Western Palaearctic

Stefanescu C., Páramo F., Åkesson S., Alarcón M., Ávila A., Brereton T., Carnicer J., Cassar L.F., Fox R., Heliölä J., Hill J.K., Hirneisen N., Kjellén N., Kühn E., Kuussaari M., Leskinen M., Liechti F., Musche M., Regan E.C., Reynolds D.R., Roy D.B., Ryrholm N., Schmaljohann H., Settele J., Thomas C.D., van Swaay C., Chapman J.W. (2013) Multi-generational long-distance migration of insects: Studying the painted lady butterfly in the Western Palaearctic. Ecography. 36: 474-486.
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Doi: 10.1111/j.1600-0587.2012.07738.x

Resum:

Long-range, seasonal migration is a widespread phenomenon among insects, allowing them to track and exploit abundant but ephemeral resources over vast geographical areas. However, the basic patterns of how species shift across multiple locations and seasons are unknown in most cases, even though migrant species comprise an important component of the temperate-zone biota. The painted lady butterfly Vanessa cardui is such an example; a cosmopolitan continuously-brooded species which migrates each year between Africa and Europe, sometimes in enormous numbers. The migration of 2009 was one of the most impressive recorded, and thousands of observations were collected through citizen science programmes and systematic entomological surveys, such as high altitude insect-monitoring radar and ground-based butterfly monitoring schemes. Here we use V. cardui as a model species to better understand insect migration in the Western Palaearctic, and we capitalise on the complementary data sources available for this iconic butterfly. The migratory cycle in this species involves six generations, encompassing a latitudinal shift of thousands of kilometres (up to 60 degrees of latitude). The cycle comprises an annual poleward advance of the populations in spring followed by an equatorward return movement in autumn, with returning individuals potentially flying thousands of kilometres. We show that many long-distance migrants take advantage of favourable winds, moving downwind at high elevation (from some tens of metres from the ground to altitudes over 1000 m), pointing at strong similarities in the flight strategies used by V. cardui and other migrant Lepidoptera. Our results reveal the highly successful strategy that has evolved in these insects, and provide a useful framework for a better understanding of long-distance seasonal migration in the temperate regions worldwide. © 2012 The Authors. Journal compilation © 2012 Nordic Society Oikos.

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