EFFECTS OF FIRE ON FOREST SOIL AND NUTRIENT CYCLING 



AN ANNOTATED BIBLIOGRAPHY 

 by 

 P.S. Downer and R.D. Barter* 



INTRODUCTION 



The forest floor and underlying mineral soil contain 

 most of a forest's nutrient reserve. Intensive and long 

 term production on forested land requires that forestry 

 practices be carefully evaluated in light of their 

 potential to modify the cycling of nutrients. Among 

 questioned practices, prescribed burning has received 

 considerable attention because fire is highly visible, 

 and uncontrolled fire is potentially disastrous. 

 However, naturally occurring fire has repeatedly 

 influenced forest development in many geographic regions. 

 Research to determine how important forest nutrients are 

 affected by fire has had conflicting results. Both site 

 improvement and detriment following fire have been 

 documented, and the problem remains largely unresolved. 



In theory, certain elements, notably carbon (C) and 

 nitrogen (N) , are volatilized when organic material is 

 burned. Among other nutrients, phosphorus (P) , potassium 

 (K) , calcium (Ca) , and magnesium (Mg) remain on the 

 surface in ash. Subsequent movement of the ash material 

 into mineral soil would increase base saturation and pH. 

 Research results have not led to clear conclusions 

 because fire intensity, amount and kind of fuel consumed, 

 soil properties, range of site variability, time since 

 burn, vegetation and climatic conditions differ for each 

 study site. 



While the abundance and availability of Ca, Mg , and 

 K are largely related to mineralogical properties, N 

 supply is dependent on microbiological processes. Fire 

 directly effects soil properties which influence 

 microbial activity. Indirectly, then, effects on 

 microorganisms will also be extremely important to the' 

 supply of plant-available nutrients. 



*Ms. Downer is a Research Assistant, and Dr. Barter is 



Associate Professor of Soil Chemistry, Institute of 



Natural and Environmental Resources, University of New 

 Hampshire. 



