PARENT SESSION
Oral Session 3: Biogeochemistry I: Litter and Decomposition.
Presiding: J Dilustro
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 107.
The effects of tree species on decomposition: Interactions between litter chemistry, earthworms and microbes.
Hobbie, Sarah*,1, Reich, Peter1, Oleksyn, Jacek1, 2, Ogdahl, Megan1, Zytkowiak, Roma2, Hale, Cynthia1, Karolewski, Piotr2, 1 University of Minnesota, Saint Paul, MN, USA2 Polish Academy of Sciences, Kornik, Poland
ABSTRACT- Plants can influence decomposition both through the chemistry of their litter and through effects on the environment. In a common garden of replicated monocultures of fourteen tree species, we used three separate experiments to distinguish these two aspects of plant effects on decomposition. First, we measured decomposition of litter produced in each monoculture plot decomposed in situ to assess the simultaneous influences of substrate chemistry and the environment on decomposition. Second, we measured decomposition of litter produced in all plots decomposed in a common site to assess the influence of substrate chemistry on decomposition in a common environment. Third, we measured decomposition of a common leaf litter type decomposed in each plot to assess the influence of the environment created by each species on decomposition of a common substrate. Tree species influenced decomposition both through substrate effects and by altering the environment for decomposition. Trees differed in their substrate quality, with Acer spp. decomposing most quickly and Fagus sylvatica decomposing most slowly. In contrast to many other studies, litter decomposition in a common site and in situ was unrelated to most measures of carbon and nutrient chemistry, but was positively related to litter potassium. Trees influenced the environment for decomposition by influencing the mass of the forest floor, with decomposition occurring most rapidly in plots with the greatest forest floor mass, likely because of greater litter moisture in those plots. Forest floor mass was in turn negatively related to litter calcium concentrations and the abundance of earthworms. Thus, litter chemistry influenced decomposition in direct and indirect ways. High-calcium species promoted earthworms that increased forest floor removal (and perhaps decomposition) but created a detrimental environment for litter decomposition on the forest floor.
Key words: litter, trees, decomposition, earthworms