Chronosequence

We use a 200-year record of forest succession at the University
of Michigan Biological Station (UMBS), derived from three sets of long-term forest plots and their associated datasets, to elucidate drivers of forest carbon (C) storage at successional timescales. This work is justified by 1) an incomplete scientific understanding of controls on forest C uptake and storage across wide successional timescales and 2) recent observations, in contrast to an existing paradigm, that old-growth forests can function as C sinks for centuries after establishment. A major component of this work is an installation known as the Burn Plots, a 100-yr experimental time sequence of 5, ~1-ha plots, each subjected the same cut-bole removal-burn treatment in 1936, 1948, 1954, 1980, or 1998, within a forest that developed after a similar wide-spread disturbance in 1911. The Burn Plots, as well as an adjacent 100-yr time series of plots subjected to cutting and bole removal but not burned, and sets of plots in three successional end-member ‘old growth’ forests (130 to >200 yr old) at UMBS, provide an opportunity to link disturbance, climatic, canopy structural, and biogeochemical controls to long-term changes of C storage in a broadly representative temperate forest. Data from standardized measurements of C cycling, soil nutrient status, and forest stand and canopy structure proposed here will be linked with >80 yr of archived data from these three sets of long-term plots to build mechanistic, transformational understanding of long-term controls on forest C storage. Such understanding is needed to explain why some aging forests remain C sinks beyond the time expected from the paradigmatic view of forest C balances during succession. As part of this project, the investigators will 1) implement course-based teaching labs and data collection, 2) draw upon an on-going manipulation of forest succession (funded from other sources) investigating process-level changes in C storage and its drivers at sub-annual to decadal timescales, and 3) use contacts within the land management community to extend the broader impacts of this research.

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