Effect of altered nitrogen availability following accelerated succession of a forest: the role of tree species and size.

Abstract

Many factors affect the amount of mycorrhizal colonization in a plant, such as soil fertility and plant species. We focus on the effect of accelerated succession, which changes nitrogen availability, on mycorrhizal colonization. Tree species and size were also of interest, as very few direct comparisons of species or size have been conducted. We measured colonization between sapling and canopy variants of Acer rubrum (red maple), Quercus rubra (northern red oak), and Pinus strobus (white pine) in a northern temperate forest in northern Michigan by analyzing fine roots using a well-developed gridline intersect method. These trees were located at two sites, one where succession was accelerated and one without accelerated succession that served as a control. Greater mycorrhizal colonization was measured in the forest undergoing accelerated succession, implying that several factors besides nutrient availability may be influencing colonization. Greater mycorrhizal colonization was also measured in the white pines, likely due to its coarser roots which rely more on mycorrhizal associations because of lower surface to volume area in the roots. It appears that both canopy and sapling individuals for each of the three study species have a similar reliance on mycorrhizal colonization, despite the different nutritional requirements between the two size classes.