THE AUTHORS 



RESEARCH SUMMARY 



MARTIN F. JURGENSEN, professor of forest soils, teaches 

 and conducts research in forest soils-soils micro- 

 biology. He earned a B.S. degree in forestry (1961), 

 an M.S. degree in silviculture (1965), and a Ph.D. 

 degree in soil science (1967). He has held the positions 

 of research associate (1966-1967) and assistant 

 professor (1966) at North Carolina State University. 

 Dr. Jurgensen's position is with the Department of 

 of Forestry, Michigan Technological University, 

 Houghton, Mich. 



ALAN E. HARVEY, plant pathologist, is responsible for 

 research into disease and other microbiological 

 problems of reforestation in the central and northern 

 Rockies. He is stationed at the Forestry Sciences 

 Laboratory, Moscow, Idaho. Dr. Harvey received a 

 B.S. degree in biology (1960), and M.S. degree in plant 

 pathology (1962), a Ph.D. degree in plant pathology 

 (1968), and an academic year of postgraduate work 

 in plant pathology (1972). He joined the Intermountain 

 Station in 1965. 



MICHAEL J. LARSEN, mycologist, is presently investi- 

 gating the taxonomy and ecology of forest fungi at 

 the Center for Forest Mycology Research, Forest 

 Products Laboratory, Madison, Wis. Dr. Larsen 

 received a B.S. degree in botany (1960), an M.S. 

 degree in plant products pathology (1963), and a Ph.D. 

 degree in forest mycology (1967). He held a position 

 with the Canadian Forestry Service (1966-1970) and 

 joined the Center for Forest Mycology Research 

 in 1971. 



ACKNOWLEDGMENTS 



The able assistance of technicians Glenn Mroz, Andrew 

 DePuydt, Margaret Gale, Scott Spano, Peter Cattelino, 

 and the other "Hungry Horse Androids" in various phases 

 of this study is gratefully acknowledged. Appreciation is 

 also due Charles Brooks, District Ranger, Hungry Horse 

 Ranger Station, Flathead National Forest, for his help and 

 cooperation during this study. 



The effects of a prescribed broadcast fire on soil nitrogen 

 (N) levels and related soil properties were determined 

 following the clearcutting of a 250-year-old Douglas- 

 fir/western larch stand in northwestern Montana. Soil N 

 losses from burning amounted to slightly over 90 lb/acre 

 (100 kg/ha), all from the surface organic layers. This was 6 

 percent of the total N originally present in the surface 12 

 inches (30 cm) of soil. In contrast, soil ammonium concen- 

 tration increased within 2 days following the fire. Rapid 

 nitrification also occurred after a 3-week lag period. The 

 higher nitrate levels were associated with increased 

 populations of nitrifying bacteria. Both soil ammonium 

 and nitrate concentrations returned to preburn levels by 

 the end of the following summer. 



Soil acidity was decreased after the burn and had not 

 yet returned to original levels in the organic horizons 

 4 years later. Organic matter content of the mineral 

 soil was not affected by the fire. 



No long-term depletion of soil N reserves would result 

 from this prescribed fire. Plant reestablishment on the 

 site benefited by increased soil N availability. 



CONTENTS 



Page 



INTRODUCTION 1 



STUDY AREA AND TREATMENT 1 



METHODS 1 



Sampling i 



Soil Analysis l 



Statistical Analysis 2 



RESULTS 2 



Total Nitrogen 2 



Available Nitrogen 2 



Other Soil Properties 4 



DISCUSSION 4 



PUBLICATIONS CITED 5 



