Mortality of trees in loblolly pine plantationsThis article is part of a larger document. View the larger document here.
The annual probability of mortality for planted loblolly pine (Pinus taeda L.) trees was estimated using a set of permanent plots covering the entire native range of the species. The recorded causes of death were infestation by the southern pine beetle (Dendroctonus frontalis Zimmermann) and other insects, lightning, and unknown reasons. It was found that mortality from these causes does not change with age of trees, which allowed us to calculate an overall mean annual mortality probability for each density-independent factor. Two sets of these estimates are provided: one for all plots and another for the plots that in the past were affected by a given factor. A model was constructed to analytically separate densitydependent from density-independent factors of mortality recorded as "other causes." The average annual probabilities of mortality are 0.8 percent and 0.6 percent for density-independent and density-dependent causes, respectively. Our analysis also covers the events that wipe out entire plots such as flood, fire, and catastrophic insect infestation. This neglected kind of mortality, referred to as indiscriminate, eliminates four times as many trees as density-dependent mortality and three times as many as density-independent mortality.