Patches and Mosaics
Historically, due to the short time scale of human observation, mosaic landscapes were perceived to be static. This focus centered around the idea that the status of a particular population, community, or ecosystem could be understood by studying a particular patch within a mosaic. However, this perception ignored the conditions that interact with, and connect patches. In 1979, Bormann and Likens coined the phrase shifting mosaic to describe the theory that landscapes change and fluctuate, and are in fact dynamic. This is related to the battle of cells that occurs in a Petri dish.
Patch dynamics refers to the concept that all landscapes are dynamic. There are three states that a patch can exist in: potential, active, and degraded. Patches in the potential state are transformed into active patches through colonization of the patch by dispersing species arriving from other active or degrading patches. Patches are transformed from the active state to the degraded state when the patch is abandoned, and patches change from degraded to potential through a process of recovery.
Logging, fire, farming, and reforestation can all contribute to the process of colonization, and can effectively change the shape of the patch. Patch dynamics also refers to changes in the structure, function, and composition of individual patches that can, for example, effect the rate of nutrient cycling.
Patches are also linked, although separated from other patches, migration occurs from one patch to another. This migration maintains the population of some patches, and can be the mechanism by which some plant species spread. This implies that ecological systems within landscapes are open, rather than closed and isolated. (Pickett, 2006)
Read more about this topic: Patch Dynamics
Famous quotes containing the word patches:
“A good story is one that isn’t demanding, that proceeds from A to B, and above all doesn’t remind us of the bad times, the cardboard patches we used to wear in our shoes, the failed farms, the way people you love just up and die. It tells us instead that hard work and perseverance can overcome all obstacles; it tells lie after lie, and the happy ending is the happiest lie of all.”
—Kathleen Norris (b. 1947)