I certify that I have read this study and that in my opinion it 

 conforms to acceptable standards of scholarly presentation and is fully 

 adequate, in scope and quality, as a dissertation for the degree of 

 Doctor of Philosophy. 



Jerome V. Shifeman, Chair 

 Professor of Forest Resources 

 and Conservation 



I certify that I have read this study and that in my opinion it 

 conforms to acceptable standards of scholarly presentation and is fully 

 adequate, in scope and quality, as a dissertation for the degree of 

 Doctor of Philosophy. 



Ka£herine C? Ewel 

 Professor of Forest Resources 

 and Conservation 



I certify that I have read this study and that in my opinion it 

 conforms to acceptable standards of scholarly presentation and is fully 

 adequate, in scope and quality, as a dissertation for the degree of 

 Doctor of Philosophy. 



Donald A. Graetz 

 Professor of Soil Science 



,(:L*.;*srtLl 



I certify that I have read this study and that in my opinion it 

 conforms to acceptable standards of scholarly presentation and is fully 

 adequate, in scope and quality, as a dissertation for the degree of 

 Doctor of Philosophy. 



William T. Haller 

 Professor of Agronomy 



I certify that I have read this study and that in my opinion it 

 conforms to acceptable standards of scholarly presentation and is fully 

 adequate, in scope and quality, as a dissertation for the degree of 

 Doctor of Philosophy. 





^>l 



Kenneth M. Portier 

 Associate Professor of 

 Statistics 



