These diebacks were numerically analyzed to exclude natural tree mortality.

Reduced tree mortality resulting from proper trenching/tunneling practices.

These are accompanied by biological changes such as elevated tree mortality, increased leaf fall and reduction of bird populations.

Thousand cankers is a recently described disease and its involvement in tree mortality apparently is also recent.

When trees are defoliated two or more years in a row, "extensive tree mortality" can result.

Severe outbreaks, which occurred on the coast during the 1940s and 1950s covered millions of acres and resulted in considerable tree mortality.

The birds can cause serious damage to trees, and intensive feeding has been documented as a source of tree mortality.

On those rare occasions when infestations last for three years or more, significant levels of tree mortality will begin to emerge during the years following outbreak collapse.

Where there are "forests already teetering on the edge," he added, the prospect of "massive tree mortality and greater susceptibility to fire" must be considered.

The Oak leaftier has caused "considerable tree mortality", especially in the Appalachian region.