Controls on autotrophic and heterotrophic respiration in an ombrotrophic bog

[摘要] Northern peatlands are globally significant carbon stores, but thesink strength may vary from year-to-year due to variations in environmentaland biogeochemical conditions. This variation is mainly brought about bychanges in primary production and in autotrophic respiration (AR;respiration by plant parts), components that we understand reasonably well.Heterotrophic respiration (HR; respiration by the soil microbial community,mycorrhizal fungi, etc.), on the other hand, is crudely measured andsimulated, which may lead to biased estimates if a change favours one formof respiration over another. HR has only recently been shown to be moreintimately linked to vegetation dynamics than once thought, particularly inwetter, oligotrophic, sedge-dominated ecosystems. The objective of thisstudy is to determine the factors that relate to the spatial and temporalvariability in respiration and its autotrophic and heterotrophic componentsin an ombrotrophic bog (Mer Bleue) where woody shrubs are dominant and tosee if the more dynamic nature of HR in sedges also exists in this bog. Plotlevel measurements using manual chambers were used to partition respirationfrom both the dominant shrubs and the sparse sedges at the site, and thecontrols on respiration were explored by measuring a variety ofenvironmental variables, such as air and soil temperatures ( T ) and watertable (WT) depth. Results show that AR and HR correlate primarily with airand soil T , with WT depth playing an important role in some cases, and thata higher variability in respiration exists for the shrub plots than thesedge plots, especially when WT levels are more variable. Our findings alsoshow that a plant's response to changes in climate is related to the plants'root structure, which indicates different mechanisms of obtaining waterresources and utilizing associations with other plants around them. Theseresults will improve our understanding of peatland carbon cycling, as wellas improve the conceptualization of HR.

[学科分类] 大气科学