To measure annual productivity in wetlands, measurements of plant biomass are made at the onset of the growing season and at the time of peak live biomass. Measurements of decomposition are generally initiated during the mid to late growing season. Methods that have been used in wetlands are described only briefly below. Measurement of biological processes in wetlands has generally been done with great innovation and adaptation, with few studies employing exactly the same procedures. For other processes and parameters, methods used in other surface waters, e.g., for measurement of invertebrate production, might sometimes be applicable to wetlands.
Decomposition is inferred by difference in weight over a specified period of time.
Three to five replicates of each type were put between wire mesh to hold them on the sediment below the water level of a reservoir. Macroinvertebrates were removed from the samples before air-drying. They identified false rings by their gradual change in cell size, as contrasted with true rings, in which small latewood cells are readily distinguishable from large earlywood cells. Their method is based on ratios of 13C to 12C, using the principle that, under drought conditions when stomates are closed, the tree will use a greater proportion of carbon-13 in photosynthesis. Repeated measurement of tree diameter also can be used to gauge growth.