New Harvard Forest Publication: Water Use in Hemlocks and Oaks

Water Use by Oak versus Hemlock: Implications for Ecosystem-level Effects of Hemlock Woolly Adelgid

The major significance of this paper is that it shows that a red oak-dominated forest, common in many areas of southern New England, uses more water in summer than an old-growth hemlock forest. As a result, if hemlocks that are killed by the hemlock woolly adelgid are eventually replaced by a deciduous forest with oak as the dominant species (or any other species with similarly high water use), forest water use will increase and the amount of water available for streamflow, lakes and reservoirs will be reduced.

The paper also shows that although summer carbon storage in the hemlock forest between July 2004 and June 2006 was much less than in the oak-dominated deciduous forest, the hemlock forest stored enough carbon during relatively mild weather (without freezing nights) in spring and fall, that annual carbon storage in the hemlock forest was comparable to the oak-dominated forest. Climate warming appears likely to increase carbon storage during these spring and fall periods.

Hadley, J.L, P.S. Kuzeja, M.T. Mulcahy and S. Singh. 2008. Water use and carbon exchange of red hemlock dominated forests in the northeastern ecosystem-level effects of hemlock woolly. Tree Physiology 28, 615–627.