Software for spatially-explicit simulation of forest dynamics

Light behaviors

Light is the key resource for trees in the SORTIE model. Consequently, great care is taken in SORTIE to calculate the amount of light that each tree gets - in fact, these calculations take up more processing time than any other during model runs.

There are two basic light index types used by SORTIE to describe the amount of light a tree receives. The first is the Global Light Index, or GLI. GLI is the percentage of full sun received at a point. The second index is the Sail Light index, which is the proportion of shade seen at a point, from none to total. (The name Sail Light comes from the fact that the shape of shading neighbor tree crowns is approximated by a 2D rectangle, like a sail).

How light calculations work

Average Light behaviorAverages GLI values to produce a set of values with a coarser spatial resolution.
Basal Area Light behaviorCalculates light levels as a function of the basal area of trees in a neighborhood.
Beer's law light filter behaviorSimulates a filter that reduces light according to Beer's Law.
Constant GLI behaviorAssigns a constant GLI value to all trees to which it is assigned.
Gap Light behaviorShortcuts the light calculation process by considering GLI to be binary: either full light or no light.
GLI light behaviorCalculates a Global Light Index (GLI) value for each individual.
GLI Map Creator behaviorCalculates a GLI value for each cell in a grid to create a light map.
GLI Points File Creator behaviorCalculates GLI values for individual points in the plot.
Quadrat-based GLI light behaviorCalculates GLI for grid cells and assigns trees the GLI of their cell.
Sail light behaviorCalculates a Sail Light index value for each individual.
Storm Light behaviorCalculates light levels as a function of number of trees damaged in storms.