How bird droppings can affect the vegetation composition of ombrotrophic bogs

Abstract

Ombrotrophic bogs depend on nutrient input from the atmosphere, so bird droppings may be a significant nutrient source. We studied the influx of N, P, and K by bird droppings, and the effects of this nutrient influx on the vegetation composition and development of Irish ombrotrophic bogs. Bird droppings significantly increased the influx of N, K, and particularly P. Concentrations of N, P, and K in the peat and vegetation were much higher at sites with bird droppings than at reference sites without bird droppings. Pinus sylvestris L. trees were able to grow much better at the sites with bird droppings, and growth was severely limited by P and K at the reference sites. Sites with bird droppings allowed atypical species to grow on ombrotrophic bogs. This change in vegetation composition alters the structure of the ombrotrophic vegetation locally, thereby affecting the atmospheric nutrient input and interception of precipitation.Key words: nitrogen, nutrient limitation, potassium, phosphorus, Pinus sylvestris, soil CO 2 evolution, Sphagnum.Résumé : Les tourbières ombrotrophes dépendent d'apports nutritifs en provenance de l'atmosphère, et conséquemment les déjections d'oiseaux peuvent constituer une source significative de nutriments. Les auteurs ont étudié l'arrivée de N, P et K provenant des fientes, ainsi que leurs effets sur la composition de la végétation et le développement de tourbiè-res ombrotrophes, en Irlande. Les fientes augmentent significativement les apports en N, K et particulièrement en P. Les teneurs en N, P et K, dans la végétation et la tourbe, sont beaucoup plus élevées sur les sites recevant des fientes que sur des sites de référence n'en recevant pas. Les Pinus sylvestris L. poussent bien mieux sur les sites avec fientes et leur croissance est limitée par le P et le K sur les sites de référence. Les sites recevant des fientes permettent la croissance d'espèces atypiques pour les tourbières ombrotrophes. Cette modification de la composition de la végétation perturbe la structure de la végétation ombrotrophe localement, et conséquemment affecte l'apport en nutriment atmosphérique et l'interception de la précipitation.

Between ice and ocean; soil development along an age chronosequence formed by the retreating Breiðamerkurjökull glacier, SE-Iceland

“…Verbeek and Boasson (1984) studied bird hummocks in the Pyrenees, France, and similarly reported significantly more N compared to the soils of their surroundings. As did Tomassen et al (2005) for bird dropping sites in Irish bogs but those had significantly higher influxes of nutrients and showed more vegetation vigor than at reference sites without droppings. The impact of seabirds on vegetation establishment and soil formation is well established from the volcanic island, Surtsey, off the coast of S-Iceland, where the lesser black-backed gull (Larus fuscus) colonized the island in 1985, establishing a nesting colony on the young lava .…”

“…In general, vegetation stratification is developed over time, with time-dependent sequence of herbs, shrubs and trees for specific regions such as the Alps and Alaska (Burga et al, 2010;Crocker and Major, 1955), and cryptogams appear to precede phanerogams at higher latitudes and in mid-and high-alpine zones (Hodkinson et al, 2003;Persson, 1964;Stork, 1963). Animals also impact the plant succession and soil development in various ways and add nutrients to the soil through dropping, often creating stark differences among sites of fertilization and the regular nutrient-poor surfaces (Bockheim and Haus, 2014;Tomassen et al, 2005).…”

High arctic ponds receiving biotransported nutrients from a nearby seabird colony are also subject to potentially toxic loadings of arsenic, cadmium, and zinc

“…Surface sediments of guano-affected ponds had significantly higher levels of P (t 6.3 5 2.42) and K (t 8 5 2.95) than ponds situated more than 1,000 m from the seabird colony (all p ,0.05). Elevated levels of these elements have been reported in soils and vegetation influenced by seabird inputs [18,[32][33][34], demonstrating that the products of biotransport may be incorporated into terrestrial food webs. This was expected since northern fulmars are generalist scavengers with a diet rich in zooplankton, squid, and fish [30] and excrete high quantities of marine-derived K, N, and P in their guano [31].…”

Lichen response to ammonia deposition defines the footprint of a penguin rookery

“…It is also possible that high surface enzyme activities in lichens are adaptations for exploiting infrequent, spatially unpredictable but highly eutrophicating events associated with deposition of animal excreta in otherwise oligotrophic areas. At Cape Hallett this would be excreta from bird species such as skuas and snow petrels flying at some distance from their nesting and roosting sites (Tomassen et al 2005;Bokhorst et al 2007). …”