A vocabulary of landscape — a landscape of words
1469 entries
overstory
The overstory is the upper layer of a forest, the crowns of the tallest trees taken together, and the layer that determines what happens beneath it by controlling how much light gets through. Below it are the understory, the shrub layer, and the ground layer, and in tall tropical forest a few trees stand clear above the rest as emergents.
Etymology
The word is a plain English compound using story in its architectural sense, meaning a floor or a level of a building, so a forest is described as a structure with stories. That sense of story is unrelated to a narrative and came into English from a Latin word for a picture or a row of images, apparently from the painted or sculpted rows on the fronts of medieval buildings.
Notes
How closed the overstory is decides most of what a forest is. A canopy gap from a single fallen tree lets a column of light down and sets off a race among everything that has been waiting in the ground layer, which is why old forest is a mosaic of ages rather than a uniform stand. Glade, nurse log, and blowdown entries all describe pieces of the same process.