Relevance of the Nitrogen Fertilization Literature to the Problem of Critical Loads for the Georgia Basin. Gordon F. Weetman Dept. Forest Science. UBC. Vancouver March 2007 Contract Report for Environment Canada.. Georgia Basin Puget Sound Research Conference March 26-29, 2007 Vancouver, British Columbia MOUNTAIN HEMLOCK ZONEMOUNTAIN HEMLOCK ZONE Biogeoclimatic Zones in Georgia Basin What can we learn from experience with forest fertilization? A huge body of literature and experience over 45 years: 11 Sources of intelligence were reviewed Source 1. Commercial N fertilization (around 200kgN/ha) in N America and Scandinavia with many environmental impact assessments and studies. e.g. Hogbom L. and Jacobson S Nitrogen an impact assessment of forest fertilization in Sweden. For.Res. Inst Sweden, Redgorelse nr 6. 42pp What can we learn from experience with forest fertilization? Source 2. Optimum nutrition experiments designed to explore the upper limits of increased productivity. e.g. Jacobson, S Fertilization to increase and sustain tree growth in coniferous stands in Sweden. Doctoral Thesis, Swedish Univ. Agr. Science., Silvestra 217. Uppsala What can we learn from experience with forest fertilization? Source 3. Fear of N staturation experiments designed to explore the capacity of the system to contain N. e.g. Tamm, C. O. Aransson A. Popovic B. and Flower-Ellis Optimum nutrition and nitrogen saturation in Scots pine stands. Studia Forestalia Suecia pp What can we learn from experience with forest fertilization? Source 3:More N saturation work: e.g. McNulty S.G. et al Red spruce ecosystem changes following 14 years of chronic N fertilization. For. Ecol. Man (in press) What can we learn from experience with forest fertilization? More N saturation work. Aber J.D. and Magill A.H Chronic nitrogen additions at the Harvard Forest (USA): the first 15 years of a nitrogen saturation experiment For.Ecol Man. 196(1):1-5. What can we learn from experience with forest fertilization? Source 4. Use of N fertilization as a test of forest ecosystem N status under suspected N loading situation e.g. Rueth H. M., Baron J.S. and Allstoff E.J Responses of Engelmann spruce forests to nitrogen fertilization in the Colorado Rocky mountains. Ecol. Applic. 13(3); What can we learn from experience with forest fertilization? Source 5. Natural loading of PNW forest ecosystems by N fixation under red alder. e.g. Compton, J. E., Church, M. R., Larned S. T. and Hogsett W. E Nitrogen saturation in forested watershed of the Oregon Coast Range: The landscape role of N2 fixing red alder Ecosystems 6: What can we learn from experience with forest fertilization? Source 6. BC experience with N fertilization in forested watersheds. e.g. Pike, R and Perrin C Fertilization in forested watersheds. Streamline Watershed Management Bull.9(1);13-20 What can we learn from experience with forest fertilization? Source 7. Reviews of N deposition effects in the US.: Work of Fenn and co-authors e.g. Fenn M.E., Poth M.A., Aber J.D., Baron J.S., Bormann B.T., Johnson D.A., Lemly A.D., McNully S.G., Ryan D.F. and Stottlemyer.R Nitrogen excess in North American Ecosystems: predisposing factors, ecosystem responses, and management strategies. Ecological Applications 8(3): What can we learn from experience with forest fertilization? Source 8. Fundamental science understanding of the N cycle in forested ecosystems. e.g. Tamm C.O Nitrogen in Terrestrial Ecosystems, Springer-Verlag. Ecol. Studies pp. What can we learn from experience with forest fertilization? Source 9. Reviews of literature by other agencies and organizations when setting critical N loads e.g. SAEFL 2003 Empirical critical loads for nitrogen: expert workshop. Swiss Agency for the Enviroment, Forests and Landscape (SAEFL) Enviro. Doc pp.schweiz.ch/buwal/shop/files/pdf/phpDQvvMp.pdf What can we learn from experience with forest fertilization? Source 10. Attempts to model the effects of N fertilization. e.g. Lillemagi M.2002 Modeling the effects of forest fertilization on the N balance in a pine stand in northern Sweden What can we learn from experience with forest fertilization? Source 11. Our understanding of the most N sensitive ecosystems in the Georgia Basin based on the work behind the BC Biogeoclimatic Ecosystem Classification (BEC). E.g. Klinka,K. and Chourmouzis The Mountian Hemlock Zone of BC and Brett.R.B.,Klinka K. and Qian H.2002 Classification of high elevation non-forested plant communities in Coastal BC.Scientia Silvica Extension Series.( Not formally published but it is the only classification and it is very thorough). What does all this work suggest about N impacts in the Georgia Basin? 1.At current low rates of N input (2 to 6 kg N/ha/yr) in the Georgia Strait present forested ecosystems it appears that no significant detrimental effects on ecosystem functions can be expected because of the ability of the humus and soil to absorb and immobilize added N. What does all this work suggest about N impacts in the Georgia Basin? 2.At higher input rates of 100 to 300 kg N/ha, in single one time doses, used in operational forest fertilization, experience from similar temperate forest ecosystems suggests that no serious detrimental effects have been found provided guidelines about applications to lakes and water courses are respected. Operational forest fertilization has been applied to second growth stands in the Georgia Basin for over 30 years and is ongoing What does all this work suggest about N impacts in the Georgia Basin? 3.Repeated applications of N fertilizer, in experiments designed to approximate N saturation, have indicated a surprising ability of forested ecosystems to absorb added N. What does all this work suggest about N impacts in the Georgia Basin? 4.European empirical critical N loads for natural and semi-natural ecosystems in 2002 are in the range of 5 to 20 kg N/ha/yr for forest and subalpine habitats. Coastal, inland surface water and bog and fen habitats are in the range of 5 to 25 kg N/ha/yr. Given the similarity of ecosystem structure and function these are reasonable values for the Georgia Basin. US values are in the same range What does all this work suggest about N impacts in the Georgia Basin? 5.N fertilization has been used to test the degree of N saturation of forested ecosystems. This review suggests it be used in the Mountain Hemlock biogeoclimatic zone of the Georgia Basin where the greatest impacts of N inputs might be expected.(An assessment of the Mountain Hemlock Zone situation has been done by Anliang Zhong as a separate contract.) What does all this work suggest about N impacts in the Georgia Basin? Recommendation. Even though current N inputs are assumed to be very low there is an almost complete lack of data on the Georgia Basin high elevation forest ecosystems.; monitoring is needed. These ecosystems are the ones expected to first show symptoms of N saturation. N fertilizer should be added experimentally to some sensitive high elevation forest sites in the Mountain Hemlock Zone of the Georgia Basin followed by monitoring.. In spite of all the research done so far, the European critical nitrogen loads expert panel suggested in 2002 at the Berne workshop that more N addition experiments are needed in areas with low deposition (Thats us!) Monitoring needed in Mt. Hemlock Zone fertilization: the changes in: tree needle sizes and N uptake; changes in the natural ground vegetation as classified by K. Klinka; changes in the humus and soil properties similar to the Engelmann-Spruce Subalpine Fir Zone ( ESSF) N addition trial in Colorado; changes in the macrofungi sporocarp production as suggested by Trudell and Edmonds. In spite of all the research done so far, the European critical nitrogen loads expert panel suggested in 2002 at the Berne workshop that more N addition experiments are needed in areas with low deposition (Thats us!) Mountain Hemlock Zone. Most N input sensitive in Georgia Basin? What was not considered THANK YOU