Relationships between rooting restrictions, radial growth, and drought stress with white pine (Pinus strobus) decline in southern Maine

Throughout southern Maine there was a noticeable decline and mortality of white pine (Pinus sfrobus) from 1997 through 2000 in dense pole-size stands. The decline was widespread, scattered, and happened simultaneously indicating that it was incited by an abiotic stress. Because only isolated stands showed decline and mortality, site factors likely predisposed trees to injury. Site factors are likely related to the widespread field abandonment that took place throughout southern and central Maine, and led to establishment of pure white pine stands in many areas. Although white pine can regenerate on many sites, some locations will have soil limitations, such as plow plans and lithological discontinuities that cause white pine roots to spread more horizontally. A shallow root system would result in less water being available to a tree during a drought. The first hypothesis is that soil rooting restrictions predisposed the white pine to water stress inciting decline and mortality. The second hypothesis follows that the drought event occurred prior to 1997-2000, the period of white pine mortality. Paired sites, consisting of one high and one low mortality site, were evaluated i