Disturbances to forests, such as logging or wildfires, typically lead to large losses of carbon and nutrients from both the plants and soils of the ecosystem. Virtually all forests are in some state of recovery from such disturbances, whether caused naturally or by humans. Knowledge of the time required for a forest to recover its original amounts of carbon and nutrients after a disturbance is not complete, nor is an understanding of how regrowing plants, recovering soils and the year to year variation in climate interact to control recovery as a forest ages. This project takes advantage of long existing research plots in forests at the University of Michigan Biological Station to figure out how changes in forest structure, carbon and nitrogen contents of the forests, and variations in climate act together through time to influence how fast trees grow, nitrogen is retained, and carbon is captured and stored in forests. Scientists and students will make regular measurements of the types of trees, their stem sizes and mass, their patterns of leaf arrangement, the amounts of carbon and nitrogen in soils, and other factors in five forest that were cut and burned in 1936, 1948, 1954, 1980, and 1998 and so today range from 15 years to 115 years old. Several nearby much older forests will also be sampled. This will let the project link disturbances, climate and ecology for forests that are broadly representative of those across the northern United States, Canada, Europe and Asia.
Researchers used dbh tapes and / or calipers to measure the diameter at breast height (dbh, 1.37 above ground) of every tree within the boundaries of each plot. For some plots, the location (azimuth and distance) from plot center (or corner post) was determined. For some plots, dbh values were assigned as classes (e.g., 6-8 cm dbh) and the number of stems of each species within each diameter class was recorded.
Below are the two equations used to estimate aboveground biomass and height of trees. See the Allometric_equations.csv file for constants used in these two equations according to species. In cases where the species is not listed in the table, the generic constants were used.
AG biomass = a * dbh^b * height^c
height = a*dbh^b