Variabilidad espacio-temporal de formas de nitrogeno y fosforo en suelos de las colonias de gaviota patiamarilla (Larus michaellis, Naumann 1840) en el Parque Nacional Maritimo-Terrestre de las Islas Atlanticas de Galicia

Abstract

An intensive program of environmental monitoring was carried out in the yellow-legged gull coloniesin order to assess its impact on vegetation, soil and water of the National Park. The monitoring wasconducted during the period January 2011 to December 2014, with a sampling frequency of about 4months for soil and coastal waters, but more intensive for the rainwater. Soil testing, rainwater, runoffand pools of Cíes and Ons and coastal waters were analysed. Also, different types of biomaterials generated by gull (droppings, feathers, pellets and eggs) were also analysed. In this paper, the results onthe dynamics of nitrogen and phosphorus in soils of yellow-legged gull colonies are presented. Soilsamples were taken at permanent plots located in different plant communities.Yellow-legged gull droppings had a high content of total nitrogen (TN) ranging between 0.7 and 16%,of which 2,000-3,000 mg kg-1 are inorganic forms that are directly assimilated by plants (N-NO3- and NNH4+). The concentration of total P in seagull droppings was also very high but less than the total N (Ptotal: 31,721 mg kg-1).The results obtained from a model indicate that annual bioenergy is deposited throughout the park45.37 t N and 7.56 t P which gives the soils colonies these nutrients to a concentration much higher thanthat obtained for the Control area. Despite the seasonal dynamics of N and P in soils it is clearly different. Thus, it has been observed that in the soils of the colony, the content of the forms of P was significantly higher in both summer and winter, while forms of N were only significantly in summer.Nitrification with the sandy nature of the soil and high rainfall is concentrated in late autumn favouredthe leaching of inorganic forms of N, but not P. Regarding this last item, fractionation showed that Papatite was the dominant form, followed by the residual P; while the P associated with the oxides andhydroxides of Fe was very low, which agrees with the low-soluble Fe ammonium oxalate.