In the zone

Nature loves order. A place for everything, and everything in its place. This week we take a look at zones, nature’s sorting bins.

Every species has its habitat, which is where it lives and what it consumes. It also has a range, which is the geographical limits of where it and its habitat exist. On a more local scale, the habitat and range occur in a zone of an ecosystem.

Even though it’s bitter cold outside (at least where I sit), let’s revisit the beach we explored at Labor Day. We examined the sea creatures one several different rocks. There were many species there: mussels, starfish, anemones, and barnacles just to name a few. They all share the same habitat (beach) and while they may have different ranges (British Columbia to northern California vs Alaska to Baja for instance), at this location their ranges overlap.

Soft-bodies sea life at the lowest exposed rocks at low tide

Hard-shelled sea life in the highest exposed rocks at low tide

But notice that the species on one rock are totally different from those on another, even though they are separated by a distance of just a few dozen feet. The rocks are in different zones. Starfish and anemones are on rocks that are farther away from the high tide line, and those species are more sensitive to the drastic changes in tide. Closer to the high tide line you’ll see the mussels, snails, and barnacles. They are hardier and can withstand exposure to dry conditions much better. Also, notice that those three all have a hard outer shell, while the starfish and anemones don’t. Think there might be a connection between zones and defensive adaptations?

Not all zones are at the beach. Take a drive up to Mount Rainier with me this summer and I’ll show you how the forest changes as we go up in elevation. The dense western red cedar, Douglas fir, and western hemlock give way to mountain hemlock, pines, and Pacific silver fir right on up to subalpine fir scattered throughout mountain meadows. The taller trees are at lower elevations, while higher up the trees are stunted and warped by the short growing season and heavy snow cover. Even the air smells different in the different zones. Marine and aquatic environments also have different zones according to depth and the amount of light that reaches them.

Western red cedar, western hemlocks, and Douglas fir at about 3500 ft above sea level

Subalpine fir at about 5500 feet above sea level

Ocean zones from Marine Biodiversity wiki
http://www.marbef.org/wiki/open_oceans

Zones can change by elevation, depth, and latitude, or a combination. Douglas fir can be found at higher elevations in the southern Cascades than in the northern Cascades. Zones can also change over time, not just space. Forest zones change as trees grow and die, or in the case of disturbances such as fire. Next time you are out and about, look around for changing zones around you!