Soil chemical properties in glacial moraines across a chronosequence influenced by avifauna and volcanic materials: Breiðamerkurjökull, Iceland

Abstract

Seabird’s role in the soil landscape evolution can be dramatic, specifically where they establish colonies. Loose colonies allow for point-centered input from avifauna at Breiðamerkurjökull glacier outwash plane in SE-Iceland. The birds utilize the open area within the deglaciated fore-land for roosting, perching, and nesting, which has resulted in striking differences in the soil environment. Using a chronosequence based on when moraines were exposed on the foreland, the aim of this study was to 1) assess changes in soil chemical properties and nutrient availability, 2) compare the differences between sites where bird activity (roosting, perching, or nesting)has led to the formation of grassy hummocks, and the surrounding moraines, and 3) investigate evidence of development of selected andic properties over time. The results strongly indicate that both the moraine and hummock soils are developing from Vitrisols towards Andisols. This is supported by the distinct trend that less phosphorus (P) is available in the soil with time, consistent with andic soil properties. Maximum P-retention was reached in the 127-year old moraine soil and hummock at 26.6%, 48.9% P respectively, and 87.5% P in a nearby woodland reference site. Cation exchange capacity (CEC) in both soil environments showed increased concentration of cations with time, presenting greater values in the hummock soils. Other soil properties, including available ammonium, nitrate, nitrite, pHH2O, and pHNaF, demonstrated the stark effects of avifauna on the soil chemical properties. Organic inputs from birds added to the bio-nutrients and organic matter (OM) in the soil, which enriches vegetation. The data from this study show that avifauna can locally enhance soil formation creating a positive feedback mechanism between soils and vegetation. The results from this study show that avifauna can locally enhance the chemical properties, plant nutrient availability, and soil formation.