Data/hora: 08/06/2024 20:38:43

Biblioteca(s): | Embrapa Florestas.
Data corrente: | 23/09/2008
Data da última atualização: | 23/09/2008
Autoria: | CALLAHAM, M. A.; BUTT, K. R.; LOWE, C. N.
Título: | Stable isotope evidence for marine-derived avian inputs of nitrogen into detrital foodwebs on the Isle of Rum, Scotland, UK.
Ano de publicação: | 2008
Fonte/Imprenta: | In: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.
Idioma: | Inglês

Conteúdo:

The Isle of Rum is home to one of the largest breeding colonies of Manx shearwater (Pufinus
pufinus) in the North Atlantic. These obligately piscivorous birds nest in burrows constructed on
the nutrient poor, rocky slopes of the highest peaks (800m) on the island. Soils around the
entrances to burrows are enriched by frequent inputs of guano as the birds embark and return
from feeding forays, and consequently, these soils support relatively lush vegetation. An
experimentally fertilized plot established in 1965 demonstrates that modest inputs of N, P, and
K in combination can support vegetation similar to that found on shearwater ?greens,? although
subsequent plots, established in 1996, testing amendments of single nutrients N, P, or K have
all but failed to vegetate.
Previous sampling of earthworms on Rum revealed that ?greens? surrounding the entrances to
shearwater burrows were among the only locations where earthworms could be reliably collected
at high elevations. Manx shearwaters are therefore appropriately viewed as ecosystem
engineers, providing habitat for earthworms that would otherwise be marginal, if not impossible,
for occupancy. Reasoning that nitrogen derived from a marine predator would have a distinctive
15N isotopic signature, we sampled feathers, guano, soil, vegetation, and earthworms to
determine the relative importance of shearwater-derived N in habitats associated with their
burrows. Soils and vegetation were sampled at 2-m intervals along transects running from the
burrow entrance into soil that was not impacted by guano inputs. For comparison, we made
similar collections in transects crossing the edge of the historic fertilizer plot, and from two lower
elevation habitats that were free from shearwater influence.
Manx shearwater feathers had the highest level of 15N enrichment of all materials collected
(+18?), followed by guano (+12?). Soil (+7.5?) and vegetation (+5.7?) collected within a
few cm of the burrow entrance were enriched with 15N relative to those collected at 2 m or more
from the burrow entrance (+0.5 to +3.1? for soil, and -2.5 to -4.6? for vegetation). In contrast,
soils from the fertilized plot had 15N signatures close to 0 and became more enriched further
away from the plot edge, and vegetation was never more enriched than -4.6? on or off the
plot. Earthworms collected from shearwater greens had tissue 15N signatures that were
dramatically enriched relative to those from the fertilizer plot (+3.8 and -0.9?, respectively).
These results imply that Manx shearwater derived N is substantially assimilated by earthworms
at high elevations on Rum. The unusual pattern of earthworm tissues less enriched in 15N than
the bulk soils on shearwater greens is worthy of further examination. Sampling for additional
earthworm material is scheduled for Spring of 2008, and these samples will also be analyzed
and presented.

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