ENVIRONMENTAL AND VEGETATIONAL GRADIENTS ON AN ARIZONA PONDEROSA PINE LANDSCAPE: IMPLICATIONS FOR ECOLOGICAL RESTORATION by Scott R. Abella A Dissertation Submitted in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy in Forest Science Northern Arizona University May 2005 Approved: __________________________________ W. Wallace Covington, Ph.D., Chair __________________________________ Peter Z. Fulé, Ph.D. __________________________________ Margaret M. Moore, Ph.D. __________________________________ Carolyn H. Sieg, Ph.D. ABSTRACT ENVIRONMENTAL AND VEGETATIONAL GRADIENTS ON AN ARIZONA PONDEROSA PINE LANDSCAPE: IMPLICATIONS FOR ECOLOGICAL RESTORATION SCOTT R. ABELLA This research was performed in northern Arizona ponderosa pine (Pinus ponderosa) forests to enhance the ecological basis for restoration projects currently ongoing in these forests. My objectives were to: (i) develop a forest ecosystem classification on a 110,000-ha ponderosa pine landscape, (ii) determine geomorphic and soil gradients associated with the distribution of plant communities on this landscape, (iii) assess potential contributions of the soil seed bank for reestablishing understory communities, and (iv) determine understory responses to forest-floor manipulations in an existing ecological restoration experiment. I identified 10 landscape ecosystem types on this landscape, ranging from black cinders/Phacelia ecosystems low in available moisture and total N, to mesic basalt/Festuca and aspen/Lathyrus ecosystems. Distribution of plant communities was chiefly correlated with soil texture and resource levels reflecting influences of parent materials. Soil seed bank composition was partly ecosystem- specific, and was dominated by graminoids and short-lived forbs such as aspen fleabane (Erigeron divergens). I did not detect any short-term (2 year) treatment effects on understory vegetation in the forest-floor manipulation experiment. ii ACKNOWLEDGEMENTS My major advisor, Dr. Wally Covington, was instrumental to the completion of this research by providing continuous support. Dr. Covington also has created an atmosphere at the Ecological Restoration Institute, which funded this dissertation, conducive for performing timely research supporting on-the-ground ecological restoration. I also appreciate the encouragement, advice, and thoughtful discussions from my committee members: Drs. Margaret Moore, Pete Fulé, and Carolyn Sieg. Students and staff at the Ecological Restoration Institute assisted me with fieldwork and numerous other aspects of this dissertation. In particular I thank Judy Springer for botanical help in the field, identifying seedlings in seed bank studies, watering seed bank samples when I could not, and numerous discussions about northern Arizona vegetation. Brian Zimmer did an exemplary job performing soil analyses, and many analyses would not have been possible without him. Other individuals at the Institute who made major contributions of their skills and time during the completion of this research include Don Normandin, Matt Tuten, Lauren Shapiro, Luke Brandy, Joe Crouse, the members of my field crews including Katie Allan, Kyle Christie, Allison Bair, Brandon Williams, Scott Sink, Jennifer Tsonis, and Jeff Rainey, and students and staff who assisted with dendrology including Bob Ivens, Steve Blazewicz, Jennifer Tsonis, Claire Fuller, Danielle Gift, and Kristen Pearson. I also benefited from many discussions about soils and seed banks with Mike Stoddard, who also always knew where to find research equipment. iii Dr. Brent D. Burch from the NAU Statistics Department provided sound advice for the statistical analysis of several data sets for this dissertation, and taught me much about statistics along the way. I am grateful to Brad Blake and Phil Patterson, who manage the NAU greenhouse, for their dedication to plant conservation and support of my greenhouse research. Dr. Steve Hart and Dan Guido of the Hart Lab, and Dr. Steve Overby and Lauren Hertz of the Rocky Mountain Research Station, provided helpful soils analysis advice and allowed me to use their equipment. I thank Keith Pajkos of the Arizona State Land Department for sharing his field knowledge, which is extensive, during several discussions in the field at the Centennial Forest. For permitting me to conduct research on their land, I thank Sheila Sandusky, J.J. Smith, and the Coconino National Forest and the Centennial Forest. I also am grateful for formatting help from Randi Walker and Rachel Crawford of the NAU School of Forestry. Finally, I thank my undergraduate advisor, Dr. Neil MacDonald of Grand Valley State University, and my M.S. advisor, Dr. Vic Shelburne of Clemson University, who enabled me to get to this point. iv TABLE OF CONTENTS ABSTRACT........................................................................................................................ ii ACKNOWLEDGEMENTS...............................................................................................iii TABLE OF CONTENTS.................................................................................................... v LIST OF TABLES............................................................................................................ vii LIST OF FIGURES .........................................................................................................viii PREFACE........................................................................................................................... x CHAPTER 1: INTRODUCTION....................................................................................... 1 CHAPTER 2: LITERATURE REVIEW............................................................................ 4 Introduction..................................................................................................................... 4 Ecosystem Classification Applications........................................................................... 6 Forest Site Classification in the Southwest................................................................... 11 Literature Cited ............................................................................................................. 13 CHAPTER 3: FOREST ECOSYSTEMS OF AN ARIZONA PINUS PONDEROSA LANDSCAPE: MULTIFACTOR CLASSIFICATION AND IMPLICATIONS FOR ECOLOGICAL RESTORATION .................................................................................... 20 Abstract......................................................................................................................... 20 Introduction................................................................................................................... 21 Methods......................................................................................................................... 23 Results and Discussion ................................................................................................. 27 Conclusion .................................................................................................................... 37 Acknowledgements....................................................................................................... 38 Literature Cited ............................................................................................................. 39 CHAPTER 4: VEGETATION-ENVIRONMENT RELATIONSHIPS AND ECOLOGICAL SPECIES GROUPS OF AN ARIZONA PINUS PONDEROSA LANDSCAPE................................................................................................................... 62 Abstract......................................................................................................................... 62 Introduction................................................................................................................... 63 Methods......................................................................................................................... 65 Results and Discussion ................................................................................................. 70 Acknowledgements....................................................................................................... 76 Literature Cited ............................................................................................................. 76 CHAPTER 5: SEED BANKS OF AN ARIZONA PINUS PONDEROSA LANDSCAPE: RESPONSES TO ENVIRONMENTAL GRADIENTS AND FIRE CUES .................... 95 Abstract......................................................................................................................... 95 Introduction................................................................................................................... 96 Methods......................................................................................................................... 98 Results and Discussion ............................................................................................... 103 Acknowledgements..................................................................................................... 113 v Literature Cited ........................................................................................................... 114 CHAPTER 6: FOREST-FLOOR TREATMENTS IN ARIZONA PONDEROSA PINE RESTORATION ECOSYSTEMS: NO SHORT-TERM EFFECTS ON PLANT COMMUNITIES ............................................................................................................ 138 Abstract......................................................................................................................