Short-term physiological responses of black walnut (Juglans nigra L.) to plantation thinning

Published in Forest Science 55(3): 221-229

We studied physiological responses of mature black walnut (Juglans nigra L.) trees to determine the time necessary for photosynthetic adaptation to plantation thinning. Measurements were taken before treatment (July 25, 2007) and for the first 3 days after thinning (July 29, 30, and 31, 2007). Measurements did not continue in August because trees had developed leaf anthracnose and senescence was occurring, but measurements resumed on May 29, 2008 and July 29, 2008. Repeated measures of net photosynthetic rates (A) showed that thinned trees did not respond immediately to partial release, but nearly doubled in A compared with a 35% increase in control trees 1 year after thinning. Significant increases in light, leaf water status, relative humidity of the air, and nitrogen content per unit leaf area were also found in thinned trees 1 year after treatment. From these variables, light (r² = 0.79) showed the strongest relationship with A. Results suggest that black walnut requires a full growing season before it responds to treatment when thinned late in the growing season. Thinning earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our study.

Forests

Scientific Article

Forestry Research, Forests, Silviculture

GAUTHIER, Martin-Michel and Douglass F. JACOBS

2009

Available at the Direction de la recherche forestière

compétition, éclaircie, écophysiologie, noyer noir, sylviculture, sylviculture des forêts naturelles feuillues, Juglans nigra, article scientifique de recherche forestière, sylviculture et rendement des forêts naturelles - peuplements feuillus, silviculture and yield of natural forests - hardwood stands, black walnut, competition, ecophysiology, silviculture, thinning