Skagit Valley College logo

Aquatic-Terrestrial Interactions

It has long been recognized that the well being of aquatic resources like the Skagit River largely depends on their terrestrial environments within the watershed. The ecological edge between the aquatic and the terrestrial ecosystems are defined as the ecotone. The land-water ecotones are especially important because numerous geological, biological and ecological processes are taking place making it a highly dynamic system. Numerous disciplines such as ecologists, wildlife managers, geographers, geologist, fisheries biologists, have for decades focused on the aquatic-terrestrial ecotone.

Community Types

Riparian Zones
Community Types Along Riparian Zones of Streams:

  • 1 - active channel
  • 2 - riparian zone
  • 3 - zone of influence
  • 4 - uplands
  • 2 and 3 make up the total zone of influence!

Links between the aquatic and terrestrial ecosystems through the riparian forests of the Skagit River:

Small stream | Mid-size stream | Large stream | Longitudinal profile of the Skagit River

Aquatic-Terrestrial Food Web

View Aquatic - Terrestrial Food Web PDF

Macroinvertebrates

View Macroinvertebrate Assemblages of the Skagit River

Nutrient Spiraling Concept

graphic of Nutrient Spiraling Concept

Streams with mature complex ecotones of woody vegetation are capable of producing many ecological processes.Macroinvertebrates and wildlife species perform these processes.

Streams lacking woody vegetation in the riparian zone are only capable of performing a few ecological processes; thereby losing energy faster than natural stream sections.

The complexity and number of loops possible is also dependent on LWD input into the stream from the riparian zone.

The nutrient spiraling concept illustrates the important link between ecological processes in the lotic and terrestrial environments and how they are linked across the aquatic-terrestrial ecotone.

One loop illustrates one ecological process. For example, let us follow one nitrate molecule in a leaf. A shredder eats the leaf, and then the shredder is eaten by a juvenile salmon, which is eaten by a kingfisher, defecating in the riparian zone. Now the nitrate molecule enters the riparian ecosystem. The fecal matter is decomposed, then taken up by a tree and put into a leaf, which is eaten by a caterpillar, which is eaten by a flycatcher, which flies across the stream and defecates the nitrate back into the stream. And on it goes.

Ecotone Definition:

A zone of transition between adjacent ecological systems having a set of characteristics uniquely defined by space and time scales and by the strength of interactions between adjacent ecological systems.