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Biogeochemical Cycling in Coniferous Ecosystems on Different Aged Marine Terraces in Coastal Oregon
Author(s) -
Bockheim J. G.,
LangleyTurnbaugh S.
Publication year - 1997
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1997.00472425002600010041x
Subject(s) - throughfall , biogeochemical cycle , tsuga , cycling , forest floor , soil water , environmental chemistry , stemflow , chronosequence , nutrient cycle , biogeochemistry , geology , chemistry , nutrient , environmental science , ecology , soil science , forestry , organic chemistry , biology , geography
Biogeochemical cycling was studied in Sitka spruce [ Picea sitchensis (Bong.) Carr.] and western hemlock‐Douglas‐fir [ Tsuga heterophylla (Raf.) Sarg.‐ Pseudotsuga menziesii (Mirbel) Franco] ecosystems on chronosequence of five uplifted marine terraces in coastal Oregon. The terraces occur 0.25 to 8.6 km from the Pacific Ocean and range from 80 to ∼500 kyr in age. The soils are highly weathered and include Inceptisols on the youngest terrace and Spodosols with clay‐enriched horizons and Ultisols on the older terraces. Bulk precipitation, throughfall, and soil solutions (four depths) were collected monthly from November 1992 through April 1993. The solutions were analyzed for pH, dissolved cations (Na, Mg, Ca, K, Fe, Al, and Si), anions (Cl, SO 4 , HCO 3 , NO 3 , and PO 4 ), and organic C. Cations (µmol c L −1 ) in all solutions were ranked: Na > Mg > Ca ≥ K > H; anions were ranked: Cl > SO 4 > NO 3 >> HCO 3 . The Na/Cl ratio in all solutions was comparable to that of seawater. The mean sums of cations and anions in all solutions declined sharply with distance from the coast. Throughfall enrichment of all ions suggests that aerosol impaction of sea salts is a dominant process within the coastal fogbelt of Oregon. In that the soils have low inherent fertility, the trees appear to obtain Ca, Mg, K, and S primarily from atmospheric sources. These nutrients are utilized by abundant fine roots in the forest floor and upper 5 to 20 cm of mineral soil. Net cation loss is less than in other areas of the Pacific Northwest and is controlled by organic anions rather than the bicarbonate anion.