Nitrogen and Phosphorus Resorption Dynamics of Five Tree Species in a Kansas Gallery Forest

Publisher Website
Google Scholar
Abstract
The foliar N and P contents of 25 gallery forest trees on the Konza Prairie Research Natural Area were measured 1 mo. before, and immediately after autumnal abscission in 1979. Leaves from 5 trees each of bur oak (Quercus macrocarpa), chinquapin oak (Q. muehlenbergii), green ash (Fraxinus pensylvanica), hackberry (Celtis occidentalis) and red elm (Ulmus rubra), ranging in diameter from 3-77 cm, were sampled. Total leaf contents varied from 47-219 .mu.g N cm-2 and 4.3-23.8 .mu.g P cm-2. Pre- to postabscission decreases of N and P were statistically significant in all species except red elm. Mean foliar N decreases varied from 13.2-54.2% among species and followed the order, chinquapin oak > bur oak > hackberry > green ash > red elm. Mean foliar P decreases varied from 7.9-36.7% and followed the order, bur oak > chinquapin oak > green ash > hackberry > red elm. P reductions were much lower than reductions reported for other hardwood forests in the USA. This may be a function of the availability of soil P at the various sites. Tree age and diameter were positively correlated with the magnitude of N reductions. Stepwise regression models based on all species combined indicated that age and diameter accounted for little of the variance in N decreases. The measured reductions in foliar N and P were not caused by leaching or insect herbivory, but rather were the result of biologically controlled nutrient resorption.