Abstract
Nitrate, ammonium, dissolved organic N, and dissolved oxygen were measured in stream water and shallow groundwater in the riparian zones of two tropical watersheds with different soils and geomorphology. At both sites, concentrations of dissolved inorganic N (DIN; NH4 +- and NO3 −-N) were low in stream water (< 110 ug/L). Markedly different patterns in DIN were observed in groundwater collected at the two sites. At the first site (Icacos watershed), DIN in upslope groundwater was dominated by NO3 −-N (550 ug/L) and oxygen concentrations were high (5.2 mg/L). As groundwater moved through the floodplain and to the stream, DIN shifted to dominance by NH4 +-N (200–700 ug/L) and groundwater was often anoxic. At the second site (Bisley watershed), average concentrations of total dissolved nitrogen were considerably lower (300 ug/L) than at Icacos (600 ug/L), and the dominant form of nitrogen was DON rather than inorganic N. Concentrations of NH4 + and NO3 − were similar throughout the riparian zone at Bisley, but concentrations of DON declined from upslope wells to stream water.
Differences in speciation and concentration of nitrogen in groundwater collected at the two sites appear to be controlled by differences in redox conditions and accessibility of dissolved N to plant roots, which are themselves the result of geomorphological differences between the two watersheds. At the Icacos site, a deep layer of coarse sand conducts subsurface water to the stream below the rooting zone of riparian vegetation and through zones of strong horizontal redox zonation. At the Bisley site, infiltration is impeded by dense clays and saturated flow passes through the variably oxidized rooting zone. At both sites, hydrologic export of nitrogen is controlled by intense biotic activity in the riparian zone. However, geomorphology appears to strongly modify the importance of specific biotic components.
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References
Boccheciamp RA (1977) Soil survey of Humacao area of eastern Puerto Rico. 103 pp. U.S.D.A. Soil Conservation Service
Boersma L (1965) Field measurement of hydraulic conductivity below a water table, pp 222–233 In: Black CA (Ed) Methods of Soil Analysis Part 1 — Physical and Mineralogical Methods. 1st ed. American Society of Agronomy — Soil Science Society of America, Madison, WI
Bogart DB, Arnow T & Crooks JW (1964) Water Resources of Puerto Rico — A Progress Report. Water Resources Bulletin No. 4. 102 pp. U.S. Geological Survey, San Juan, PR
Bouwer H 1986 Intake rate: cylinder infiltrometer, pp 825–844, In: Klute A (Ed) Methods of Soil Analysis Part 1 — Physical and Mineralogical Methods. 2nd ed. American Society of Agronomy — Soil Science Society of America, Madison, WI
Bowden WB, McDowell WH, Asbury CE & Finley AM (1993) Riparian nitrogen dynamics in two geomorphologically distinct tropical rain forest watersheds: nitrous oxide fluxes. Biogeochemistry 18: 77–79
Brown S, Lugo AE, Silander S & Liegel L (1983) Research history and opportunities in the Luquillo Experimental Forest. General Technical Report SO-44. 128 pp. USDA Forest Service, New Orleans, Louisiana
Cooper AB (1990) Nitrate depletion in the riparian zone and stream channel of a small headwater catchment. Hydrobiologia 202: 13–26
Curtis RE Jr., Aquino Z, Diaz PL & Garcia R (1986) Water Resources Data — Puerto Rico and the U.S. Virgin Islands. Water Year 1986. U.S.G.S. Water-Data Report PR-86-1
Dahm CN, Trotter EH & Sedell JR (1987) Role of anaerobic zones and processess in stream ecosystem productivity, pp 157–178. In: Averett RC & McKnight DM (Eds) Chemical quality of water and the hydrologic cycle. Lewis Publishers, Chelsea, Michigan
Davidson EA & Swank WT (1986) Environmental parameters regulating gaseous nitrogen losses from two forested ecosystems via nitrification and denitrification. Applied and Environmental Microbiology 52: 1287–1292
Day PR (1965) Particle fractionation and particle-size analysis, pp 545–577. In: Black CA (Ed)Methods of Soil Analysis Part 1 — Physical and Mineralogical Methods. 1st ed. American Society of Agronomy — Soil Science Society of American, Madison, WI
Duff JH & Triska FJ (1990) Denitrification in sediments from the hyporheic zone adjacent to a small forested stream. Canadian Journal of Fisheries and Aquatic Sciences 47: 1140–1147
E.P.A. (1983) Methods for chemical analysis of water and wastes E.P.A.-600/4-79-020. U.S.E.P.A. Environmental Monitoring and Support Laboratory, Cincinnati, OH
Ewel JJ & Whitmore JL (1973) The ecological life zones of Puerto Rico and the U.S. Virgin Islands. U.S.D.A. Forest Service Research Paper ITF-18. 72 pp. Institute of Tropical Forestry, Rio Piedras, P.R.
Fail JL, Hamzah MN, Haines BL & Todd RL (1986) Above and below-ground biomass, production, and element accumulation in riparian forests of an agricultural watershed, pp 193–223 In: Correll DL (Ed) Watershed Research Perspectives. Smithsonian Institution Press, Washington, DC
Ford TE & Naiman RJ (1989) Groundwater — surface water relationships in boreal forest watersheds: dissolved organic carbon and inorganic nutrient dynamics. Can. J. Fish. & Aqua. Sci. 46: 41–49
Frangi JL & Lugo AE (1985) Ecosystem dynamics of a subtropical floodplain forest. Ecological Monographs 55: 351–369
Gregory SV, Swanson FJ, McKee WA & Cummins KW (1991) An ecosystem perspective of riparian zones. BioScience 41: 540–551
Grimm NB & Fisher SG (1984) Exchange between interstitial and surface water: Implications for stream metabolism and nutrient cycling. Hydrobiologia 111: 219–228
Hendrickson OQ Jr. (1981) Flux of nitrogen and carbon gases in bottomland soils of an agricultural watershed. Ph.D. dissertation, University of Georgia
Hendricks SP & White DS (1991) Physicochemical patterns within the hyporheic zone of a northern Michigan river, with comments on surface water patterns. Canadian Journal of Fisheries and Aquatic Sciences 48: 1645–1654
Hill AR (1990) Groundwater flow paths in relation to nitrogen chemistry in the near-stream zone. Hydrobiologia 206: 39–52
Hynes HBN (1983) Groundwater and stream ecology. Hydrobiologia 100: 93–99
Jacobs TC & Gilliam JW (1985) Headwater stream losses of nitrogen from two coastal plain watersheds. Journal of Environmental Quality 14: 467–472
Lodge DJ & McDowell WH (1991) Summary of ecosystem-level effects of Caribbean hurricanes. Biotropica 23: 373–378
Lowrance RR, Todd RL & Asmussen LE (1983) Waterborne nutrient budgets for the riparian zone of an agricultural watershed. Agricultural Ecosystems and Environment 10: 371–384
Lowrance R, Todd R, Fail JJ, Henderickson OJ, Leonard R & Asmussen L (1984) Riparian forests as nutrient filters in agricultural watersheds. BioScience 34: 374–377
Odum HT (1970) Rain forest structure and mineral-cycling homeostasis, pp H3–H52. In: 144 Odum HT & Pigeon RF (Eds) A tropical rain forest — a study of irradiation and ecology at El Verde, Puerto Rico. Division of Technical Information, U.S. Atomic Energy Commission, Washinton, DC
Peterjohn WT & Correll DL (1984) Nutrient dynamics in an agricultural watershed: observations on the role of a riparian forest. Ecology 65: 1466–1475
Pringle CM & Triska FJ (1991) Effects of geothermal groundwater on nutrient dynamics of a lowland Costa Rican stream. Ecology 72: 951–965
Scatena FN (1979) An introduction to the physiography and history of the Bisley Experimental Watersheds in the Luquillo Mountains of Puerto Rico. General Technical Report SO-72, 22 pp. USDA Southern Forest Experiment Station New Orleans, Louisiana
Scatena FN, Silver W, Siccama T, Johnson AH & Sanchez MJ (1993) Biomass and nutrient content of Bisley Experimental Watersheds, Luquillo Experimental Forest. Biotropica (In press)
Schnabel RR 1986 Nitrate concentrations in a small stream as affected by chemical and hydrologic interactions in the riparian zone, pp 263–282. In: Correll DL Watershed Research Perspectives. Smithsonian Institution Press, Washington, DC
Seiders VM (1971) Geologic map of the El Yunque quadrangle, Puerto Rico. Miscellaneous Geological Investigation I-658. U.S. Department of the Interior, Geological Survey, Washington, DC
Solorzano L & Sharp JH (1980) Determination of total dissolved nitrogen in natural waters. Limnology and Oceanography 25: 751–754
Stanford JA & Ward JV (1988) The hyporheic habitat of river ecosystems. Nature 335: 64–66
Stark NM & Jordan CF (1978) Nutrient retention by the root mat of an Amazonian rain forest. Ecology 59: 434–437
Triska FJ, Duff JH & Avanzino RJ (1990) Influence of exchange flow between the channel and hyporheic zone on nitrate production in a small mountain stream. Canadian Journal of Fisheries and Aquatic Sciences 47: 2099–2111
Triska FJ, Kennedy VC, Avanzino RJ, Zellweger GW & Bencala KE (1989) Retention and transport of nutrients in a third-order stream in northwestern California: Hyporheic processes. Ecology 70: 1893–1905
Valett HM, Fisher SG & Stanley EH (1990) Physical and chemical characteristics of the hyporheic zone of a Sonoran Desert stream. Journal of the North American Benthological Society 9: 201–215
Wadsworth F & Bonnet JA (1951) Soils as a factor in the occurrence of two types of montane forest in Puerto Rico. Caribbean Forester 12: 67–70
Weaver PL & Murphy PG (1990) Forest structure and productivity in Puerto Rico's Luquillo Mountains. Biotropica 22: 69–82
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McDowell, W.H., Bowden, W.B. & Asbury, C.E. Riparian nitrogen dynamics in two geomorphologically distinct tropical rain forest watersheds: subsurface solute patterns. Biogeochemistry 18, 53–75 (1992). https://doi.org/10.1007/BF00002703
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DOI: https://doi.org/10.1007/BF00002703