Effects of experimental flooding regimes on the seasonal carbon and nitrogen budgets of silver maple (Acer saccharinum) and speckled alder (Alnus incana ssp. rugosa).

摘要

Alteration of natural flooding regimes can expose wetlands to soil waterlogging during any part of the growing season. Carbon and nitrogen budgets of dominant riparian woody species may be seriously impacted when flooding occurs after the normal spring flood period. To better understand this process, I exposed silver maple (Acer saccharinum L.) seedlings to summer, fall, and continuous (summer + fall) root flooding. Seedlings of speckled alder [Alnus incana ssp. rugosa (DuRoi) Clausen], a dominant N-fixing woody species in northern wetlands, received late spring, summer, and fall flooding treatments. Silver maple survived all flooding treatments and its capacity to grow and accrete N and nonstructural carbohydrates was significantly affected only with continuous flooding for the final four months of the growing season. Fall flooding expedited fall senescence processes in silver maple, including resorption of foliar N and nonstructural carbohydrates into woody tissues. Speckled alder survived flooding only in the fall. In alder, both nitrogen and carbon fixation were arrested without recovery during flooding in all treatments. Resorption of foliar N and nonstructural carbohydrates in alder were increased by fall flooding, possibly promoting survival the following spring. Seasonality of flooding differentially affected the carbon and nitrogen budgets of these two dominant riparian species and may influence the future range and ecological importance of these species as global climate change and water control structures alter current hydrological patterns.