Biogeochemistry is the scientific discipline that addresses the biological, chemical, physical, and geological processes that govern the composition of the natural environment, with particular emphasis placed on the cycles of chemical elements critical to biological activity. Biogeochemical assays may measure a specific elemental pool, determine the rate of a pathway, or address a surrogate of a biogeochemical process or an elemental pool. In this chapter, we have attempted to emphasize field techniques; however, some of the techniques have relatively standard laboratory components that are beyond the scope of this chapter. This chapter is not meant to be all inclusive. We have chosen to emphasize the cycling of carbon, nitrogen, phosphorous, sulfur, manganese, and iron. Some of these techniques are not appropriate for all types of wetlands, or may be appropriate for a seasonally saturated wetland only during part of the season. Some of the techniques are simple and rely on equipment available to most wetlands practitioners. Others, which utilize isotopic methodologies, require expensive sophisticated equipment. Some techniques, such as soil organic matter determination by loss on ignition, have been accepted as standard methods for decades. Others, such as the determination of dissolved organic matter represent recent advances in a rapidly evolving field of ultra-violet and fluorescence technology. Some techniques rely solely on direct field measurements; others rely on the incorporation of published data with field data. Apparent strengths and weaknesses of the various approaches, and wetland scenarios that would preclude the use or compromise the accuracy of a given technique are addressed.
Overview of TechniquesBiogeochemistry is the scientific discipline that addresses the biological, chemical, physical, and geological processes that govern the composition of the natural environment. Particular emphasis is placed on the study of the cycles of chemical elements such as carbon (C), nitrogen (N), and phosphorous (P) which are critical to biological activity. Biogeochemical assays may measure a specific elemental pool (e.g., soil organic carbon), determine the rate of a pathway (e.g., denitrification), or address a surrogate of a biogeochemical process or an elemental pool. The surrogate approach is popular for rapid assessment to characterize ecosystem health, functional capacity, nutrient loading, or water quality. In each case the practitioner must be aware of the exact nature of the parameter in question as well as limitations to the method. Attempts to quantify individual pools of C or N at best, produce representative estimates. On a wetland scale, it is not realistic to believe that the pool can be quantified with 100 % certainty. There is too much variability in the field and input sources which cannot be completely accounted for. Accuracy is compromised due to precision limits inherent to the technique and due to field variability. Results are often expressed on a per area basis (e.g., m
À2). E...
