Landscape linkagesThere
is broad interest in better understanding the importance of landscape
linkages among what were once thought to be isolated ecosystems. Some
of the most interesting questions relate to linkages between aquatic
and terrestrial ecosystems, within aquatic systems such as littoral
pelagic linkages, and among aquatic systems such as lakes and the
coastal ocean. Landscape location and arrangement, and their
interaction with ecosystem size, may have important impacts on the
strength linkages among ecosystems and food webs.
David
Post has also worked to understand how food webs dynamics may be
influenced by the movement of predators or the flow of energy and
nutrients across ecosystem and sub-ecosystem boundaries. Using
theoretical models, David has addressed how food web linkages created
by mobile top predators may influence dynamical properties of food webs
(Post et al. 2000).
David has also addressed the problems with defining boundaries for of
ecosystem, and how our definition of an ecosystem boundary is
influenced by the questions we ask (Post et al. 2007).
Related publications (Publications):Walters,
A.W., and D.M. Post. In review. Anadromous alewives contribute
marine-derived nutrients to coastal stream food webs. Submitted to Canadian Journal of Fisheries and Aquatic Sciences.
Post, D.M. and A.W. Walters. In review. Nutrient excretion rates of
anadromous alewives during their spawning migration. Submitted to Transactions of the American Fishery Society. Dalton, C.M., D. Ellis, D.M. Post. In review. The impact of Double-crested Cormorant predation on anadromous alewives in south-central Connecticut. Canadian Journal of Fisheries and Aquatic Sciences. Paetzold, A., M. Lee, and D.M. Post. In press. Marine resource flows to terrestrial arthropod predators on a temperate island – the role of subsidies between systems of similar productivity. Oecologia. Post, D.M., M.W. Doyle, J.L. Sabo, and J.C. Finlay. 2007. The problem of boundaries in defining ecosystems: a potential landmine for uniting geomorphology and ecology. Geomorphology 89:111-126. Post, D.M., M.E. Conners, and D.S. Goldberg. 2000. Prey preference by a top predator and the stability of linked food chains. Ecology 81:8-14. Kitchell,
J.F., D.E. Schindler, B.R. Herwig, D.M. Post, M.H. Olson, and M.
Oldham. 1999. Nutrient cycling at the landscape scale: the role of diel
foraging migrations by geese at the Bosque del Apache National Wildlife
Refuge, New Mexico. Limnology and Oceanography 44:828-836. Post,
D.M., J.P. Taylor, J.F. Kitchell, M.H. Olson, D.E. Schindler, and B.R.
Herwig. 1998. The role of migratory waterfowl as nutrient vectors in
managed wetlands. Conservation Biology 12:910-920. |
In
collaboration with researchers at the University of Wisconsin - Madison
and the US Fish & Wildlife, David Post has studied the role of
migratory waterfowl in moving nutrients across the landscape of central
New Mexico (
(about half
of the total annual nutrient load for those wetlands), the impacts were
diluted at the larger spatial scale of the entire wetland complex where
bird born nutrient had little effect on ambient nutrient
concentrations. This project was especially germane in the Southwest
where water quantity and quality, and the use of water by humans and
wildlife, are in potential conflict. High nutrient inputs by birds
exacerbate conservation and management problems associated with high
bird densities and limited water supply.
Members of the Post lab have also explored the role of subsidies between systems of similar produtivity (
tested
these ideas on Horse Island, in Long Island Sound. The forest of Horse
Island is more productive then the relatively productive waters of Long
Island Sound which surround the island. We used pitfall traps and
stable isotope techniques to addressed the questions a) to what degree
do major guilds of terrestrial arthropods derive energy from marine
inputs, b) how far do marine resources penetrate the island, and c)
whether arthropod consumers are more abundant near shore than in inland
areas . Our results provide the first estimates of the importance of
marine resources to a terrestrial system where net primary production
in the recipient habitat is similar to that of the donor habitat (
Emerging
work in the Post lab on anadromous and landlocked alewives adds a new
element to our research on spatially linked food web interactions. In
coastal lakes throughout New England, life history difference between
landlocked and anadromous alewives mediate the spatial scale of
interactions between alewife populations and local communities and
ecosystems. Anadromous alewife populations create a spatial linkage
between lakes where they spawn and the coastal ocean where they spend
much of their life. 
In
contrast, landlocked alewives provide no spatial linkage outside the
lake in which they reside because dams or other similar impediments
have severed their migratory route to the coastal ocean. Because
alewives are important as both predators and prey, they provide a
system for simultaneous consideration of the effects of mobile
predators and prey subsidies. Anadromous alewives are important vectors
for moving marine derived nutrients into freshwater ecosystems (Post
and Walters in review; Walters et al. in review) and important prey for
many coastal breading birds like cormorants (Dalton et al. in press)
and osprey and for fish predators in many coastal lakes. Alewife lakes
along the coast of New England provide a powerful context in which the Post Lab
will address the question: how do spatial linkages driven by mobile
organisms mediate local dynamics? Because differences in spatial
linkages emerge from variation in life history strategies, alewives
also provide a model system for addressing a secondary question: how do