Community Ecology Processes, Models, and Applications

conclude with some suggestions for users, stake-
holders and scientists.

7.2 Community interactions across system boundaries

7.2.1 Linkages between adjacent or distant ecosystems

Adjacent ecosystems may influence each other in a
variety of ways. For example, upstream deforesta-
tion may lead to downstream nutrient enrichment
and sedimentation (Inesonet al. 2004). Adjacent
ecosystems also may be mutually influenced by
animal species that have a wide foraging range
(van de Koppelet al. 2005). For example, seabirds
affect plant productivity, detritus and, consequent-
ly, beetles in coastal terrestrial communities (San-
chez-Pinero and Polis 2000). Introduced exotic
species may influence these community interac-
tions. For example, introduced rats in New Zealand
feed on seabirds, reducing the transport of nutri-
ents from sea to land and leading to cascading
effects on belowground organisms and associated
ecosystem processes (Fukamiet al. 2006).
Land use changes can have strong and large-
scale consequences far from the actual site of
change. The current increasing demand for biofuels
to replace fossil fuels in the industrialized world
influences production systems in second and third
countries. As a consequence, the increasing de-
mand of biofuels in Europe or the USA will influ-
ence food production in other parts of the world.
This competition for land between food and biofuel
production influences food prices and changes the
traditional competition between land needed for
food production and for biodiversity conservation.
Therefore, the desire of human society to counter its
impact on climate may lead to food limitation in the
third world.
Local subsidies may also disrupt remote commu-
nity interactions in nature. The increased use of
nitrogen fertilizers in the mid-west of the USA is
correlated with the increased abundance of mid-
continent snow geese. Most likely, agricultural
food subsidy to the geese during their overwinter-
ing in the mid-west indirectly destroys the breeding
grounds in the Canadian Arctic and sub-Arctic;

large populations of the snow goose cause over-

grazing of shoreline vegetation, transforming the

vegetation into bare sediment. Even when the

snow goose population is eventually reduced, re-

covery of the breeding ground vegetation will take

decades (Abrahamet al. 2005).

Climate change may have strong local and non-

local effects on phenology. Local effects are, for

example, the interruption of prey abundance for

hole-breeding birds, such as the great tit (Parus

major). This forest bird feeds on winter moth,

which occurs on birch and oak trees. When they

are feeding their nestlings,P. majorfirst use winter

moth caterpillars from birch and then switch to

caterpillars from oak trees. However, climate

warming has advanced spring by 10 days over

past decades and, while birch trees respond to

warming, oaks do not. As a consequence, the birds

face a gap in prey availability, limiting their ability

to raise their chicks (Visser and Holleman 2001).

Some migratory birds, such as the pied flycatcher,

overwinter in West Africa. As the effects of climate

warming on arrival of spring in North-Western

Europe are not apparent in West Africa, the Pied

flycatchers still arrive at the same dates, but at a

later stage of phenology. This reduces preparation

time for nest building and egg laying and con-

strains the ability of the birds to adjust chick feed-

ing to prey availability (Both and Visser 2001).

7.2.2 Linkages between subsystems: aboveground–belowground interactions

Aboveground and belowground compartments of

terrestrial ecosystems traditionally have been con-

sidered separately, but now their interlinkages are

receiving increased interest (Wardleet al. 2004).

Community composition and community process-

es in each linked subsystem depend strongly on the

adjacent communities and often there is mutual

interference. These dependencies can be caused by

organisms that spend part of their life cycle in the

soil and the other part above ground, such as many

root-feeding insects, which mate and disperse

above ground. Also, some carnivorous inverte-

brates are supposed to use belowground prey sub-

sidies to survive the absence of aboveground preys,

for example in between two agricultural crops (Bell

APPLICATIONS OF COMMUNITY ECOLOGY APPROACHES 85