Influences of elemental interactions and pedogenic processes in organic matter dynamics

This paper reviews progress in understanding the processes which are important in elemental interactions and which influence organic matter composition of soils of the Great Plains in N. America. Comparison of grassland (semiarid) soils along environmental gradients and cultivation chrono- and toposequences with adjacent forest (subhumid) soils and consideration of the C/N/P/S ratios of organic matter of genetic horizons in the solum have emphasized the importance of movement of low molecular weight organic compounds in soil solution in addition to microbial degradation in the formulation of organic matter in soils. Phosphorus forms and transformations help to provide both an index on weathering and insight into textural influences. Use of ¹⁵N and ³⁴S in combination with¹⁴C and other radioisotopes has provided valuable information on processes. Submicroscopy techniques in combination with cytoplasmic staining techniques have focussed attention in a realistic way on the mechanisms of organic matter stability. More attention must be paid to the catalytic role of soil inorganic constituents and selected minerals in the abiotic formation of stable organic matter. Conceptual and mathematical simulation models have an invaluable role in focussing attention on important processes and verifying hypotheses.