Organic Matter Transformations through Arroyos and Alluvial Fan Soils within a Native American Agroecosystem

• Published in: Soil Science Society of America journal Vol. 71; no. 3; pp. 829 - 835
• Main Authors: Norton, J.B, Sandor, J.A, White, C.S, Laahty, V
• Format: Journal Article
• Language: English
• Published: Madison Soil Science Society 01.05.2007; Soil Science Society of America; American Society of Agronomy
• Subjects: Agricultural ecosystems; Agronomy. Soil science and plant productions; Alluvial fans; alluvial soils; Biological and medical sciences; Canyons; Chemical, physicochemical, biochemical and biological properties; Detritus; Downstream; Earth sciences; Earth, ocean, space; Ephemeral streams; Exact sciences and technology; Forest floor; forest litter; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; Geochemistry; hills; Indigenous peoples; Mineralization; Native North Americans; Organic farming; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; preferential flow; sediment deposition; Sediments; Semiarid lands; semiarid zones; slope; Soil and rock geochemistry; soil fertility; soil nutrient dynamics; soil nutrients; soil organic matter; soil quality; Soil science; Soils; Streambeds; Surficial geology; Suspended sediments; VOCs; Volatile organic compounds; water flow; watershed hydrology; watersheds; New Mexico; United States; Amerindian; Fluvial features; Traditional farming; Chemical transformation; Alluvial soil; streams; Property of soil; cultivated soils; Man environment interface; Earth science; debris cones; North America; biogeochemistry; Agroecosystem; Temporary water; fluvial sedimentation; temperate zone; Agronomy; Biotransformation; Arroyos; organic materials; alluvium; Soil science; sediments
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj2006.0020

Linked biochemical and fluvial processes in discontinuous ephemeral streams may support sustained productivity of soils farmed by southwestern Native Americans for 3000 yr. Ephemeral stream channels transport forest floor litter and soil materials from upland hillslopes to alluvial fans. Improved understanding of how ephemeral streams transport and process forest-floor organic materials could improve conservation of ecologically important and productive headwater alluvial fans. We analyzed organic and mineral materials from source to mouth along two ephemeral streams and analyzed suspended sediments from four collection traps in each. Results suggest that decomposition processes differ by reach and frequent, low-energy flows preferentially transport organic detritus as it decomposes. Processing of organic-rich sediments in canyon reaches is dominated by microbial immobilization (low inorganic N and available P, high C/N ratio). Arroyo reaches receive organic materials chiefly from upstream so mineralization plays in increasing role as materials are transported and decomposed downstream without fresh inputs. The frequency of flow decreases in a downstream direction as water infiltrates sandy streambeds. In lower arroyo and fan reaches, inputs of organic-rich sediments are infrequent. Relatively frequent wetting and drying stimulates mineralization of organic materials so concentrations of inorganic N and available P in detritus are relatively high. Results suggest that organic-rich sediments processed through ephemeral streams and deposited on unincised alluvial fans are important in sustaining one of the most productive landscape positions in semiarid regions.