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(1)Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author..

(2) KAMAHI DECLINE IN TONGARIRO NATIONAL PARK. A thesis presented. for the Degree of Doctor of Philosophy in Ecology at Massey University. Kim Suzanne MCBreen. 1999.

(3) III. "And I forget just what it takes and , yeah, I guess it makes me smile,. I found it hard, it was hard to find, oh well, whatever, nevermind.". Cobain, 1 990.. "I greet him the days I meet him, and bless when I understand." Hopkins, 1875..

(4) v. ACKNOWLEDGMENTS H eck, so many people to thank. Start with the official ones I guess.. This thesis was funded by the Department of Conservation, M assey U niversity G raduate Research Fund , M assey University Ecology Department funding, and a g rant from the Robert B ruce Trust. DoC also provided much logistic support, by way of labou r and accommodation, as well as h eaps of advice and support from the l ikes of Harry Keyes, Cam Speedy, and Cathy Jones, all of whom initially came up with the idea and money for this p roject,. also Sean Husheer. DoC collected much of the data for Chapter 2, and set up the exclosure p lots for Chapter four, providing all labour and equipment. The Ecology Department was equally supportive, and I am grateful to the many techn icians who have helped, particularly Jens Jorgensen and Paul B arrett who, along w ith some lucky volunteers, helped set up the treatments for Chapter three. M uch is owed to my supervisors. -. JiI I R apson, M ur ray Potter, Peter van. E s s e n and lan Atkinson for all the help and advice.. Particularly J i I I , w ho's put a lot. of time i nto this project especially in the i n itial stages, helping set up the t reatments for chapter three and taggi ng seedlings for chapter four, and in the last year or so, w ith editing, and advice on writing and stats.. I've had advice and assistance from so many other people on this project, I ' m beginning to wonder what I actually did. At least this will make my thesis longer. . .. For free advice many thanks and m uch awe to: lan Henderson, who was the fortunate recipient of an endless stream of q u estions and. barely articulated requests regarding the appropriateness of statistical techniques, and explanations of resu lts. If the stats i n this thesis make any sense, all c re d it m ust g o to him. Bill Faulds, who sent m e i n the right direction when setting up the experime nt for. Chapter three, and provided useful advice thro ughout the project, or asked othe r people at FRI on my behalf. Ross Beever and Peter Joh n ston for explanations relating to Sporothrix taxonomy. and ecology. J . B .Wilson, for the software and analysis for chapter three, plus statistical advice. along the way..

(5) VI. For p ractical help, s etting up experiments and such like , I am eternally g ratefu l to: James and S uzanne Lambie. James pretty much helped set up everything I did for. the chapter three experiment, and I didn't even have to marry h i m . Suzanne also helped with possum banding of trees for that experiment, as well as providing heaps of moral support, and an able and willing husband. And while I'm on the topic of Lambies, I g u ess I better not forget C h a rlie and An ne, who fed me, gave me a warm place to stay, and endless supplies of gin, beer, whisky and possums. Cheers. Vau g han Keesing, who also helped band trees, kept me company on countless rec.. trips to the Park, and when we got lost, counted (as well as tagging and id.ing) seedlings for chapter four, and g enerally kept me more sane than I would otherwise have been during the initial stages of this thesis. Halema Flan nigan, yet another person who tagged seedlings for chapter four,. crawling around very small exclosure plots so I didn't have to. Nick Singers for help setting up the experiment for chapter three and also h elping. keep me sane. Penny Aspin helped set up the l itter traps for chapter three, provided me with a car. whenever I was desperate for one, and introduced me to her g randma, Wanaka Cooga n , who gave me a warm and lovely place to stay, and lots of interesting. conversation . Jarn Godfrey, worked like a Trojan (whatever that means) helping sort and weigh. samp les for c hapter three. Whoa, I hope I haven't missed anyone, deepest apologies if I have, it's j ust that I ' m t rying t o block t h i s part o f my life from memory.. To the many, many people who have g iven me much needed support - big sloppy kisses, i n particular everyon e previously mentione d , and: M um and Dad, because they're my mother and father respectively.. everyone I've flatted with over the last couple of years, but mostly Stove and Waka, because they had to put up with me for longest (and because they're lovely) , and Jen n y and Patrick, because they're as lovely as people can possibly be. Hira ni, for obvious reasons, being neat, and eating with me, and letting me stay when. I d idn't exactly have a flat, and being someone I could bitch to, because that's what I most n eeded through most of this thesis. Step h , for similar reasons, taking my m ind off school at all times..

(6) vii. Megan, lovely, sigh, who spent as m uch time with me as I needed while I was losing my. m i n d trying to finish this ridiculous piece of work. Yeah . . . I think that's probably af( the more important people, obviously God for the inspiration , M USA for the distraction and blah blah. Pretty m uch every morning I get d ressed. I don't have many clothes to choose fro m , but I pick o u t what I feel like wearing a n d ask eithe r Megan or my flatmates h o w I l ook. Scruffy, usually. Sweet as, I say - because I 'm a student. A student. And with that i n m i n d. . ..

(7) ix. TABLE OF CONTENTS. TABLE OF CONTEN TS ABSTRACT. . . . . .. . .. .. C H A PTER 1 :. . . . . . . .. .. . . . . . . . . . . . . . . ... . . . . . . . .. .. . . . . . . .. . .. . . . . .. .. . . . . . .. . . . . .. .. .. ...... .. .. . . . .. . . . . . . . . . . . . .. .. ... . .. . . . . . . .. .. .. . . . . . . . . .. . . . . . . . . . ... ... . . . .. . . . . . . . . . . .. . . . . . . . . .. .. . .. .. . .. .. .. . . .. . .. . . . . . . .. .. . . . . . . .. . . .. . .. .. .. . . . . . .. . .. . . . .. . . .. ... . . . . . ... .. ... IX. XIII. THE D IEBACK PH E N O M E NON WITH REFERENCE TO KAMA H I. (WEINMANNIA RACEMOSA) I N TONGARIRO NATIONAL PAR K, N EW ZEALAN D1 DIEBACK. . ... . . ... . . . . .. . . . . .. . . . . .. MODELS OF DIEBACK. .. . . . .. . . .. . .. .. .. .. .. .. .. . .. . . .. . .. . . . . . . . . . .. .. . . .. .. .. . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1. GENERAL MODEL OF DIEBACK . . .. . . .. .. . . . . . . ... . . . . ... . . . .. .. .. . . . .. . . . .. 4. MODEL OF SUCCESSiON. . .. . . . . . . .. TONGARI RO NATIONAL PARK . . .. Park H i story . . .. . . . . . . .. .. .. .. .. . .. .. .. .. .. . .. ... . . . . . . . . . . .. .. . .. .. .. .. .. . . .. . ... .. . . .. . .. . . .. .. .. . .. . .. .. .. .. . . . . . . .. .. .. . . .. .. .. .. . . . . . . .. .. . .. .. . .. .. .. .. . . .. .. . .. . . . . . . .. . .. .. . . .. . ... .. .. .. . . . .. . . . .. . .. . .. . .. . . .... . .. .. .. .. .. . .. . . . . .. .. . . . . .. . . . . . . . . . . .... .. .. .. .. .. .. .. .. ... .. . . .. . .. .. . . . . .. .. . . . . . .. .. .. . .. .. . . .. .. .. . . . . . . . . . . .. .. . . . . .. . .. . . .. . . . . . . .. . . . .. . . . . . . .. . . . . . . .. .. . . . .. . .. .. .. . . . . . . . . . . . . . . . .. .... .. .. . . . . . .. .. . .. .. . . .. . .. . . . . . . . .. . .. .. . . . . . .. . . . . . . . . .. . . . . . . . . . . . . . . . . ... .. . .. 2. .. .. .. . .. . ... . . ............ . . . . .. . . ... . .. KAMAHI ( WEINMANNIA RACEMOSA) . . AIMS OF THIS STUDy .. .. .. . . '" ..... ............................ ..... . ... . . . 4. 2. DECLINE DISEASE THEORY OF STAND-LEVEL DIEBACK 3. COHORTSENESCENCE THEORy. .. .. . .. . . . . .. .. .. . .. .. ... .. . . ... . . . . . . . .. .. .. . . . . . . . . .. . .. .. .. . . . .. . . . . . . . . . .. . . . . . . .. .. .. . . . .. . . . . ... . . .. .. .. .. . .... .. . . . . . . . .. .. . . . . . . .. .. .. .. .. . .. . . . . .. . . .. 5 6. . 7 .. .. . . . . . .. .. . . .. .. . . . .. . . . . . . .. . . .. .. . ... . . . . . .. . . . . .. . . . . . . ... . . .. . . . . . . . . . . . . . . .. .4. . . . . . .. . . . . . . . .. . . . . . . .. . . . .. . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . .. .. 8. .1 0 .. 1 1. . .1 4 . .. APPROACHES................................................................................................................ 1 5. REFERENCES. .. . . .. .. ... . . ..... .. .. . . .. .. . . . . . . . . . . .. .. . . . . .. .. . .. .. . . ... .. . . .. .. .. .. . . . . . . . . . . . . . .. . . .. .. . . . . . . . . . . . . . . . . . . .. .. . . . .. .. .. . . . . . .. .. . .. .. . . .. .. 1 7. C HAPTER 2: SURVEYS O F KAM A H I (WEINMANNIA RACEMOSA) D I E BA C K I N TONGAR I R O NATIONAL PARK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . .2 1. I NTRODUCTION. . . . . . .. . . . . . . . . .. ... . . . . . . . . . . .. . .. .. .. . . . . .. . . . . .. . .. . . . . . .. . . . .. .. . . . . . .. .. . . . . . . . . . . . .. .. .. .. .... . . . . . . . .. . . . . . . . . . . . . .. . .. .. . . .. 21. C H APTER 2A:. ASSESSMENT OF EXTENT AND POSSIBLE CAUSES OF KAM A H I. ABSTRACT.. .. (WEINMANNIA RACEMOSA) D I E BACK I N TONGARJRO NATIO N A L PAR K . . . . .2 3 .. . . .. .. . . . . .. I NTRODUCTION . . .. .. . . . . . . . . . .. .. . .. . .. .. .. . . . . .. .. .. .. .. . .. . . . . . . . . .. . . .. . . . . .. . . . .. . . .. ... .. . . . . . . . . . .. . . . . . . . .. . . . . . . . . . .. . . . . . . . . . . . . .. ... .. . . . . . .. .. . .. . . . .. .. ..... .. . . . . . . . . . . . . . . . . .. STAND DYNAMICS AND PA TTERNS OF REGENERA TION. ........ .. .. .. .. . . . . . .. .. . . . . . . . . . . . . . . . . . ... .. .. . . . ...... .. . . . . . . . . . . ... . . .. . . . . . . . . .. .. .. . . .. .. .. .. . . . .. .. . . . .. ... . . .. .. .. .. . . .. . . . . . . .. ... ... .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . .. . . . .. .. . . .. . . .. .. . .. . . . . .. .. . .. .. . . . . . . . . .. .. .. .. . . . .. . . . . . . . . . . . .. . . .. . .. . . .. . . . . . . . . . . . . .. . . . . . . . . .. .. . . . . . . . . .. .. . . . .. . .. .. .. 25. . . .2 5. A IMS. M ETHOD .. 23. . .. . . .. 26 28. SITE SELECTJON " ......... . . . " ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 . .. SITE SURVEy. .. . .. . . . . . . . .. TREE SURVEY. . .. .. . .. . . . .. .. . .. .. .. .. .. .. .. .. . . . . . .. . . . .. .. . .. .. . .. .. . . . .. .. . . .. .. Characters . . Health . . .. . Potential causes of d ieback . ANALYSIS . . . .. .. . . . . . . .. . . .. . . . . .. . . . .. .. .. . . . .. . .. .. .. . .. .. . . . . .. .. ... .. . . . .. .. . .. .. .. . .. RESULTS SITES. .. .. . . . . . . .. .. ...... .. .. . . .. . .. .. . .. .. . .. DiSCUSSiON. .. . . . . .. . . . ... . . . .. .. . . . ... .. . .. . . . . . .. .. . . . . .. . . . . .. . .. . . . . . . . . . .. . . . . . . .. . . . . ... TREES . .. .. . .. .. .. . . . .. .. . . . . .. .. . .. . . . . .. .. .. .. .. .. .. .. . . . . . . . . . .. . .. . . . . .. .. . . . . ... . . . . . . . . .. .. .. .. .. .. .. .. .. ... .. .. ... .. .. .. . . . . .. . . .... .. .. . . . . .. . . . . . . . . . . . . . . . . . . . .. .. .. .. .. . .. .. .. .. . . . . . . . . . . ... .. .. .. .. .. . . . .. .. .. .. . .. .. . .. .. .. .. . . ... . . . . .. .. . .. .. . .. . .. .. . . . .. .. . . . .. . .. . . . . . .. . . . .. .. .. .. . .. . . . . . . . . . .. . . . . . . . .. . .. .. . .. . . . .. . . . . . . . . . . . .... . . . . . . .. . . . . .. . . . . . . . . .. .. .. .. . . . .. .. .. . .. .. .. .. . .. .. .. ... .. ..... ... . .. . . . . . . . . . .. . .. .. . . . . . .. .. . . . . ... . . . .. . . . . . . . . . . . .. . . . ... .. SITE RELA TlONSHIPS TO DIEBACK . . .. .. .. .. . . . . . . .. . . .. . . . . . . ... ..... .. .... .. .. .. ... .. .. ... .. .. . . . .. .. .. . .. .. . . . ... .. . . . . .. . . . . .. .. .. .. .. . .. .. ... .. .. .. ... .. . .. ... .. .. .. . .. .... .. .. . .... . . . . .. . . . . . .. . . . . . . . .. . . . .. ... .. ... . . .. . . . . . .. . . . .. .. . . . .. . .. ... .. . . . . . .. .. .. .... .. . .. ... .. . .... .. . . . . .. ... . ... .. .. . . . . . . .. . .. .. .. .. . . .. .. .. ... .. . . . .. . . . . . . . . . . .. 30 30 30 31 3 1. .31 32 .. .. 34. . . 34 ... . . . . . . .. . ... . . ... .. . .. .... . . . . ... . . . . . .. . . . .. . . . . . . . . . . .. .. .. . . ... .. .. .. . . ... ... . . . . . . . ... .... .. . . . 28. . . . . .. . .. . . . . .. .. . . . . .. . .. . .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . .. . . .. .... . . . . . . .. .. . . . . . . . . . .. . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . .. . . . . . . . . . .. . .. . .. ... . . . . . . . . . . . . . . . . . . . . . .. .. .. .. . .. .. . . . . . . . ... . . . . . .. . . . .. . . . . . . . . . . . . .. .. . . . . . .. . . . .. .. .. .. . . .. .. . . . . . . .. . . . . . . . . .. . . . . . . . .. . . . . . . . . . .. . . . . . . . . . . . . . . . . .. .. . .. . . . . .. .. . . . . . . . . . . . . . . . . . . .. ... . . .. . .. . . . .. . . . .. . . . . .. . . . . . . . .. . . . . . . . . . .. .. .. .. . . . . . . .. . . . .. . . . . .. . . . . . . . . . . . . . . . .. . . . . . . . . . .. . . . ... . . . . .. Site d escri ptors . Tree data . . . . . .. .. ... . . . . . . . ... . . .. .... . . . . . . . .. .. .. .. . 38. . . . . . . .. .. 45. . .. 45. .. .......

(8) x. TREE RELA TJONSHIPS TO DIEBACK CONCLUSION. REFERENCES APPENDIX A. . . . . .. . . . . . .. . . .. . .. . . . .. .. . . . .. . .. . . . . .. . .. . .. .. .. .. . . .. .. . . . . .. . . ... .. .... . . . .. .. .. .. .. .. .. .. . . .... . . . .. .. '" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 6. . . .. . .. . . . .. . .. . . . . . . .. . . . . . . . . . . . .. . . . . .. .. .. . . .. . . . . . . . .. . .. . . . .. .. . . .. . ... .. .. . .. . .. . .. . . . . .. . .. . ... ... ... .... .. .. .. . . . . . . . . . .. . . . . . . . . . . . . .. ..... . ... . . . ... . .. .. ..... ... .. .. .. .. .. . . .. . . . ... . .. .. . .. . .. .. ..... . .. ... . . . . . .. . . . . . . .. . .... .. . . . .. ... . . . ... ... .. ... .. .. ..... .. .. .. .. .. .. . . . .. . ... . . . ... .. . .. . . .. ... ... .. .. .. .. . . 48 .. .. .... ...... .50. .. 5 2. C H A PTER 2B: CAUSES O F KAMA H I I LL-H EALTH I N LOCALISED AREAS O F H I G H T R E E M O RTALITY I N TONGARIRO N ATIONAL P A R K 5 7 . . . . . . . . . . . . . . . . . . . . . . . .. ABSTRACT . . . .. ... . . . . . ..... . ... I NTRODUCTION . . . . ... . .. . .. ... . . .. . .. .... .. .. . . ... . .. .. .. .. . .. . . .. .. . . .. CAUSES OF KAMAHI DIEBACK A IMS AND APPROACH .. . . . . . .... .. .. .. .. .. . .. ... METHOD. .. ... . . .. . . .. . . . . . . . . .. .. ... . . . . . . . ... SITE SELECTION. .. . . .... .. ...... .. SURVEY .. . .. . .. .. . .. . .. .. .. . . .. . . ... . .. . .. Site character Tree health . A NALYSIS . . .. ..... .. .. . ... . .. .. ... .. . .. S ite character T ree h ealth . SITES. . . . . . . . ..... .. . .. .. .. .. .. .. . . . .. .. . .. ... .. .. .... .. ... ...... .. .. .... . . ... . .. .. .. .. . .. .. .. .. .. .. . . .. . .. .. ... . . . . .. . . . .. .. . .. . .. . .. .. .. .. ... .... .. .. . . .. . ..... .... .. . . . . .. .. .... . . .. .. .. . .... .. .. . ...... .. .. ...... .. .... . . .. .. ... ... .. . . . .. .. .. .. .. . .. . .. .. .. .. ... . .. .. .. .. .. . .. . . .. .. .. ... ........ .. .. ... .. . ...... .. .. . .. .. .. . .. . . . ... .. .. .. .. . . . .... .. . . . .. . . ......... .. . . .... .. .. .. .. .. . .. .. ..... .. .. . .. . . . . . .. .. . . .. . .. .... . .. .. .. .. .. .. . .. .... .. . .. . . . .. .. .. .. ... . .. .. . . . . .. ... .. .. . .. .. . .. . .. .. .. . .. .. ..... .. . . . ..... . . . . .. . .. .. .. .. . ... ... .. . .. .. .. .. . .. . .. . .. .. .. . ... ..... . .. .. .. .. . .. .. . ... . .. . . .. .. . .. .. . . . . ...... . . .... ... .. ........ . ...... .. .. .. . .. ... . . . . .. . . . .. ... .. .. .. . . ... . .. .. . .. .. ... ... . . .... .. . . ... . .. ..... . .. . . . . . . . .. ... . . .. .. . .. .. .. . . . .. .. . . ... . . . .. .. .. .. ... .. .. .. .. . .. .. ... .. .. .. .. .... . . . .. . .. .. . .. .. . . .. . . . . .. . .. . . .. .. 61. .. .. . . . .. .. . . . . . . . .. .. .... .. .. .. .. . . . . . . . .. . . . .. . .. . . . ..... . .. ... .. . .. . . . . . . .. .. . .. .... ... .. .. .. .. . .. . . . .. . ... .. .... .. .. .. . ... .. . .. .. .. .. . .. .. . . 6 3 . . 64 . . 67 .. .. .. . .. .. .. ... .. . .. .. .. .... .. ... .. ... .. .... . .. .. .. . .. . 6 8. . . .. . ... .. . . .. .. .. . . ... .. ... .. . 68. .. ... .. .. .. .. .... ... .. . . ... . . .. . . .. . . .... .. .. .. ... ..... . .. .. . .. . . . ...... . .. ... .. . . .. .. ... ... .. .. . . .. .. .... mEES. . . . . . . . . ....... . . ... DiSCUSSiON . .. .. . .. .. .. . .. . ... .. .. ..... .. .. .. . . . .... . . . . . . . . . . .. PREDISPOSING FACTORS. .. . . .. ..... . . .. .. . .. .. .. .. . .. . . .. . . . . . .. .. .. .. .. .. .. . . ... . . . . . . . . . ... . ..... . . . .. ... . . .. . . . . . . . . . . .. . . . . . . . .. .. .. TRIGGERING AND ACCELERATING FACTORS. ...... .. .. ..... .. .. .... ... . . .. .. .. .. . . . . ... .. .. . . ..... .. ... .. . . ...... .. .. . .. .... ... . . .. .. . .. . . ... .. . . .. .. .... . . .. .. . . ... . . .. . .. .. . . . . . .. . . . .... . . .. .. .. .. . . . . . . . .. . . . .. ... ... .. .. .. .. ... . . .. .. . ... .. . . . .. . ... .. ..... . . .. .... .. .. .. .. .. .. .... .. .. . . .. 72 73. . . .. 7 4 .. .. . . .. . . . . . . . . .. . . .. .. . . ... . . . . . . ..... . . . . . . . . . . . . . . . . . . . . ..... . . . . . ....... . . . . . . . . .. . . . .. . . . . .. . . . . .. . . . . .. . . . . . . . . . .. .. . . . .. .. 68. .. . . ... . . 6 8 .. . .. 6 8 . 72. ... .. .. . . 63. . ... ... . . . .. . . .. .. . . .. . .. . .. . .. .. ... .. . ... . . . . .. ... . ... .. .. . . ..... . .. . . ... . . . .. .... .. ... . ... . ... .. . ......... .. .. . . . . . . . . .. . . . .. . . ..... . .. . . . .... . . . . . . . . . . . . . . . . ... .. 59. . .. .. .. .... .. ... .... . . . ... ... 57. ... .. . .... . .. . .. ... . . . . . .. . . . ... . . .. . .. . . ... . . . . . . . . ..... ... . . . .. . . . . . .. . ... . . . .. . .. .. . . . . . . . . .. . .. . . . . . . . . . ... . . . .. ... . . . . . . .. . . .. . . . . . . .. . . . .. ..... .... .... .... . . ... . . . . . .. . ... . . . . . . . .. ... . .. .. ... .. .. .. . . . ........... .. .. ...... .. . ... . . . .. . . . . . . . . . . . . .. ... .. .. .. .. .. ..... . .. . . ... .. . .. . . . . . . .. .. ... . .. . .. . .. . .. .. .. .. . .. . .. .. .. . . . . . . . . . . . . . . . .. .. . ... ..... .. ... .. .. . . .. .. .... .. ... . .. .. .. . . . . .. . ..... . . . . .. . . .. . . . .... .. .. .... . . .. ... .. ... .... .. .. ... . . .. . .. .. .... . ... .... .. . .. ... . ... .. .... .. . .. . . . . .. .. .. ... . ... .. ... .. .. .. .. .. ..... .... . . .. . . . . .. . . . .. .. . . . . . . . . . .... . . . . . .. . . . . . .... . . . .. .. . .. . .. RESULTS. .. . .. .. ..... ..... ... .. ... .. . . . . . . . . . ..... . .. M easures of h ealth . . . Possible causes of die back Statistical Approach . . . . . . .... . .. 74. 80. . . . . .... .. . . . .. .. . . .. 83. 85. . . . .. . . . . . . . . . . . . . .. '" . . . . . . . . . . . . . . . . . . . . . . . . . . .88. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . '" . . . . . . . . . . . . . . . . '" . . . . . . . . .89. REFERENCES . . . . APPENDIX A. .. .. . .. .. .. . .. .... ..... .. .. . . . .. .... .. .. .. .... .. .. .. . . .. ..... . . . .. . .. .. . .. .. ... .. . .. .... .. ... .. ... .. .. .. . .. .. . . . .. .. .. .. . . . .. .. ... . .. .. .. .. . .. . ... APPROXlMA TE LOCA TJON OF TRANSECTS. ...... APPENDIX B. .. . . .. . .. . .. .. . .. .. . .. . .. .. . . . .. . .. ... .. . . ... . .. . . .. . . . .. . . . .. .. ... . .. .. .. .. . ... .. . .. . . . . . . .. . . . . . ... ..... . .. . . .. . . . .. . . .. . . . . . . .. . . . . . . .. ... .. ... ... .. . .. ... . . .. .. ..... . . .. . .. .... .. .. .. ... .. .. . . .. . ..... . .. . .. .. .. .. . .. .. .... .. .. ... .. . . . .. .. .. .. . . . .. . .... . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . . ... C HAPTER 2: D ISCUSSION O F THE TWO S URVEYS. .. .. . .. .. .. . . .... . . .. . . ... . . .. .. .. . .. .. . .. .. .. ... .. .. .. 9 0 .. ..... .. 9 4. '" . . . . .94. .. . .. .. . .. . . .. 95. 9 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. C HAPTER 3: A N EXP E R I M E NTAL APPROACH TO DETE R M I N E EFFECTS OF POSSUMS, P I N H OLE BORER, A N D SPOROTHRIX ON KAMAHI H EALTH 1 01 .. ABSTRACT. . .. . . . .. ... I NTRODUCTION . . POSSUMS. . . .. .. ... .. .... .. . . . . . . . .. . ... . . . . .. .. .. .. . . . ...... .. .. .. . . . .. .. . .. ... . . ... . .. . . . . .. . . . .. .. .. . . .. .. .. .. .. .. .... .. .. .. .. .... .. ..... . .. .. POSSUMS AND KAMAHI DJEBACK. .. ... .. .. . .. .. .. .. . .. . .. . .. ... .. .. .. .. ... . . .. . . . .. .. . . ... . . . . .. . .. . . . . .. .. . . . . .. .. .... .. .. ... . . ... .. .. .. .. . . .. . . .. .. .... .. .. .. . . .... .. ... . .. .. .. ... .. . . .. .. . .. . . .. . . . .. . . . . . . . . . . . . .. .. . . . . . . . . . . .. .. .. ... .. .. ... .. .. . . . . ... ... .. .. .. ... .... . .. .. .. .. .. . .. ... .. . . . . .. .. .. ... .. .. . .. .. .. .... . . .. . . . . . . ....... . . . .. . . . . . ..... . . . . . .. . . . . . .. .. .... .. . .. .. ... .. .. .. ... 1 0 1 .. .. .. . .. .. ... .. . .. .1 03. . .. .. . . . .. . . . .... . .. . .. .. . ... . .. 1 03 1 04. SPOROTHRIX AND PINHOLE BORER . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .... . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 5 SPOROTHRIX, PINHOLE BORER AND KAMAHI DIEBACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 7 A IMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 08.

(9) xi. STUDY SITE. .. . . . . . . . . . . . . .. . .. . . . .. METHOD. .. .. . . . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . . . . . . .. HEAL THYSUB-SITE. .. . . .. .. Banding . . . . . Fungus . H oles and I noculation UNHEAL THYSUB-SITE . . . .. ...... ..... ..... .. ... .. .. .. . . . . .... . .. . .. .. . . . . .. . . . . . . . . . . .. . . . . . ... .. .. . . . .. .. RESULTS. ..... . ... ... . . .. . . .. .. . .... .. ..... .. .. .. . . .. .. .. .. .. .. . .. . . . . .. .. . . .. .. .. .. .. ...... ...... .. ... .. ... . . .. .. .. .... . . .. . . . . .. ... ....... .. . . .. .... . . . . ... .. . .. .. .... ..... .. .. ... ... .. ... .. ... . .. .. .. . . .... .. .. . .. .. .. . . .. .... ...... ... .. . ... .. ... .. . .. .. . . . . . . . ... . .. . . ... . .. ...... . . . . . . .. . . .. .... ... ... ... .. ... .. .. .. ... ....... .. . .. .. .. .. .. . . ... .. ...... ... . .. . . .. ..... .. .. .. .. .... .... .. .. .... ... .... . . .. ... . . . . . . . . . . .... . . .. . . .. . . . . .. . . .. .. .. . . .. . .. . .. .. .. ... . .. .. . . . . . . . . . . ...... . ... . .. .. . .. .. .. .. .. ....... .. ... .... . .. .. ..... .. ..... .. ... .. .. .. ... .. 10 12 12. 14. .... .. .. . . . ... .. ... .. .. .. . . . . .. . 1 1 6 . ..... . .. .1 1 7 ... .. . . 1 17. . . . ... . . ... .. .. .. .. .. .. . . ... .. ... .. .. .... .. .. .. . .. .. .. . ... . 1 1 9. ..... . .. .. .... . ... . . . . . ..... ... ... .... .... .. .. . . ... . . ... .... .. .. .. .. . . . . .... . .. .... .... .... . . . . . . . . . ... ..... ..... . . .. ... . . ... . .. . . . . . . . ... . .. .. .. .... ...... .. ... .. . . .. 1 19. . . .. . .. . . . .1 1 9 . . . ... . . .. . . . 1 2 1 .. . . .. . . .. .. 1 2 1 ... . . ... . . .... .. . .1 24 .... . . .. .... . . .. 1 24 . . . . . . .. .. ..1 2 5 . . 125. .... ... ... . .... ...... .. .. ... ..... . . ... ... ... . .. . .... .. .... . . . .. .. .. .. .. . .. . .. . .. . . . ..... ........ .. .... . . .. . . . . . . .. . .. . . .. . . .. . . . .. .. ........1 1 0. ... ... . ...... 1 1 4 . . . .... . 1 14 . ..... . . . . .. . 1 1 6. .. .. ..... ... . . . . . .. .. 1 1 0. . .. . . . . . .... . .. . . . .. . . . . .. . .. .. .. .. ... .. ...1 . . .. . . . .. 1 . . .. ... . 1 . ... 1 . .. . . . . . . .. . . . .. . .. ... . .. . . . ... . . . .. . . . . . .. . . . .. .. ... .. .... .. . . .. ... .. . . . . . . . . . . . . . . .. . . .. .. .. . .. . . . . . . . . .. ... . . ..... .... .. . .. .. . . .... ..... . . . .. . . . ... .. . . . . . . .. . . . .... . .. ... . .. .. ... . . . ... ...... .. . . . . .. . . . .. . .. . . . . .. . . . .. ..... . . . . . . . . . . .. . .. . . . . ..... .... ... ... ......... . . .. . . . .. ... .. . . . . .. . . . . . .. . . . . . . . .. . . . . . .. .. ... .. . .. .. . . . . . . . . . . . .. .. .. . . . . .. . .. . . . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . .... .. . . . ..... ... .. . . . . ........ . . ... . .... . . .. .. .. . . . . .. . .. . . . . . .. . . .. . .. . .. . . .. . .. ... . .. .. . . . .. . .. . . .. . . . . . . .... .. ....... . ... . .. .. .. .......... .. .. ...... . . . .. . ... .... . . . .. .... .. ... .. . .. . . .. . .... .. .. . . ...... . . . . .. . . .. ......... .. ... . . . .. .. .... ..... ...1 0 9. . . .. . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. Counts and weights per day per m 2 P roportions of counts. . . . .. . Counts per day per m2 . . .. P ro portion of weight . . Proportio n of kamahi component . . . Weight per day per m2 . HEALTHYTREATMENTS . .. . . . .. . .. .. ... . ... .. . . . . . . .. . . . . . . . . . . . .. . ... ... . . . . . ...... .. . . . . . . . . . . . .. .. . ... . ...... . . .. . . . . . . . . . .. . . ...... . . ...... .. . ... .... .... . . . . . . . .. . . . . . . . . .. . . . . . . . . . .. . .. . .. . . . . . .... . . . .. . . . ..... . . . . . . . . . . . . . .. ALL TREATMENTS. .. .. . . . ... . . ... ..... .. . .. . . . . . . . ..... .. . ...... .. . . . . . . . . . . .. ... . . ...... .. . . . ... . . . ....... ... . . . . . . .. Leaf litter traps Observational data ANAL YSIS . . . .. . .. . ...... . . . .. . . . . . . . .. .. . . . .. . . . . . . . .. .. . .. . . . . . . . . .. .... . . .. Banding Fungicide inoculation MONITORING . . . .. . . . . . .. .. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. .. . . ... .. . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. ... . .. ... . .. .... .. .. .. .. ..... .. . .... .... .... .... . ... .. ... .. .. .. .. .. .. ... .. . . .. .. ..... .. .. .. .. . .... .. .. .. ... ... .... .. . .. . .. ..... . . .. . . . . . . . .. .. ... .. .. ........... . . . . . . . . . . . . ... P roportion of counts . . . . . .. ... . .1 2 5 Counts per day per m2 .. . ............... . . . . ... . . ... ..... . . . . . . . . .. . . . ............... . . . . . . . . . .... ...... . ....... . . 1 2 6 P roportion of weight . ... ... . ................. .......... ......... . ... ............. .................... . . ........... 1 2 6 P roportion of kamahi component . . .. . .. . . . ... . . . . . .. . .. . 1 2 7 Weight per day per m 2 . . . . . . . . . . . .. . . . . .. 1 2 7 UNHEAL THYTREA TMENTS . . . . . . . .. . . 127 ... . . . . ..... . .. . . .. . . . . . . .. . . . . . . . . . . . . . . . .. .... .. .. .... . . . . . . . . . . . . . . . . . . . . . ... .. .. .. . .. .. . . .. . . .. .. . .. . .. ... . . .. . .. ..... . . .. ... .. ... .... .. . . . ... . . . .. . .. . .. .. ... ... . . .. .. . .. .. .. ....... .. .. .. . .. . . .. .. .. .. .. . .. . . . . .. . . . . . . . ...... .. .. .. .. . .. . . . .. . .. . . ... . .. .. . .. .. . . .. . . . .. .. .. .. . .. . . . . . ... .. .. . . .. .. .. .. .. . .. . . . .. . . . . .. . . . .. . .. .. ... .. .. .. ... . . . . . . .. . .. .. P roportion of counts ......... . ........... . . ..... . . ... ...... . ... . . ....... . . . . . . . .... ........ . . .. . . ..... ............1 2 7 Counts per day per m2 .. . . . . . . . .. .. . . .. . . . .. .. .. .. .. ... . 1 2 8 . P roportion of weight . .. . . . . .. . ..1 2 8 P roportion of kamahi weight ... . . . . . . . .. . . . .... . . . . .. . . . . . ..... . . ... . . .. . . ..... . . . . . ... . . . . .. . . . . .. , ......... 1 2 9 Weight per day per m2 . . . ... ... ..... ....1 2 9 OBSERVA TIONAL DA TA . .. . . . . . .. 1 29 . . . . ... .. .. . . . . . . . . .. .. .. DISCUSSION. .. ....... . . .. . .. .. .. . . ........... .. . . . . . . . . . . . ... . . . . .. . . .... .. . . . .. . . . . .. .. .. .. . . .. ... .. . . ....... . . . . . . .. . . .. .... .. ... ....... . .. .. . .. . . . .. . . . ..... .... .... . . .. . . . . . . . . . . . . . . .. . .. . .. . . . . . . . . . ... . . . . . . . . . . ..... .... .. ... .... .. . . . . .. . . . . . . . .. . . . . .. . . . . . . ... .. ........ . . .. .. ...... .. .. .... .. ... . . .. ... .. .. . .. .. ... .. . . ... .. . . . . .... .... . . . . . . . . . . . .. .. .. .. .. . .. . .. .. ... . ...... .. .. . .. . . .... . . . . . . . . .. . .. . . . . . . . . . . . . .. .. .. . . . . . . . . .. . . . . .. ... . . .. . .. . . . ... ... . ...... 1 3 1 .... ... .. . .. ... .. REFERENCES .................................................... ............................................... ...... . . . . . ... 1 34 APPENDIX I. .. . . . . . . . . . .. .. . . .. . . ... ... . .. . . .. . ... ..... . .. . . .. . . . . . .. .. . . .. ... . .. . . . . . .. ... . . .... .. ..... ... . . . .... .. . . .. . . ... . .. .. .. ... ....1 3 6. . . . ... . .. C HAPTER 4: REGENERATION UNDER A H EALTHY OR THI N N I N G KAMA H I C A NO PY, A N D T H E EFFECT OF EXCLUDING LARGE A N I MALS 1 5 3 . . . .. . . . . . . . . . . . . . .. ABSTRACT . . . . . ..... . . . . . . . . . . . . . .... . . ... . . . . . ..... . . . . . . ....... . . . ... . . . .. .... . ... . . . .... . . ... ...... . . .... . ... ... ..... . . ..... . 1 5 3 I NTRODUCTION .. . . . . ... . . . . . . . .... . . . . ... . . ... . . . . . . . . ....... . . . . . .... . . ...... . ... ... . . ......... . . ...... . . .. . ...... .........1 5 5 REGENERA nON. . . . . . . . .. .. . .. .. . . ... .. . .. .. . . . . . .. . .. . . .. ... . . .. .. ........ .. ..... . . . . . . .... .... .. .. .. .... .. .. .. .... . . . . . .. . .. .. . . . . . . . .. .. . . .. . .. 1 5 5 .. .. 1 55. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . .. . . . .. . . . . . . .. 1 56. ANIMALS .. . . ... .. . . . . . . ....... .. . . . .. .. .. . .. .. . . . . . . . . . .. . . . . . . .. .. . . . . . .. . . . . . . .. .. . . .. .. .. . .. . .. .. .. ... ...... .. . . ... . . .. .. .. .. ... .. . . .. .. ... . . . . . . ..... .. .. A IMS. STUDY SITE M ETHOD. . . .. . . . .. . . .. . . .. . . . ... ... . . .. ... .. .. .... .. . . . .. . . .. . . .. .. . . . . . . . .. . . . . . . . . . .... . .. ENCLOSURE PLOTS. .. .. . . .... .. .. .. .. .. . . .. . . . . . . .. ..... .. . . . . . . . . .... . .. .... .. .. .. ..... .. .. . . .. .... .. . .. . . . .. . . ... ... ... ... . . ... . . .. . .. .. ... ... .... .. . . . . . .. . . . .. . . ..... ..... .. .. . . . . . . . .. . .. .. . . . . .. .. . . .... . . . . . . . . . . . . . . . .. .. . .. . . .. . .. . . . .. . . .. . .. .. . ... .. ... . . ... ..... .. . . ... ..... .. .. .. .. . . . . . . .1 5 8 .. .. .. . . .. . . . .... ...1 5 7. .. .. .. ... .. .... .. .. . .... ... ... . .. 1 58 ... ...

(10) xii. RECORDING ..... . . .. . ... . . . ..... ... . . . . . ...... . . ... . . . . . ...... . .... . . . ...... ..... ... . . . . . .... . .... ..... . . . . . . ... . . . .. . . .. . .158 ANALySiS . . . . . .. . . . ... ... . . . ..... . ... . ... . . .. . . . . . . . ... . . . . . ... . . . . . . . . ... ... . . . . . . . . . .... . .. . . . ... . . . . ..... . . . ... . . . . . . . . . .160. RESULTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 61. DATA EXPLORATION . ..... ... . . ..... . . . ..... . ..... . . ... . ... . . . . ... . . . ....... . . . . . . . . . . . . ....... . . ... ..... ... . . .... . ... .161 ANALySiS ....... . . . ... .... ..... . . . . . . . . .... . ....... . . ... . . . . . ..... . . .... . .............. . ... . ............ . . . . ..... .... .... ...165. DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 1 7 0 RESULTS ........... . . ........ . ... . . . . . . ... . . . .... . ... . ..... .... . .. ...... .... ........ . . . . ... .... . ... ... . . ....... ....... ......170 COMPARISON WITH LITERATURE . . . . . ...... . . ..... . . ..... . . . . . ... ....... . . . ..... . . . . . ..... .... . . . . . ... . . . . ....174. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . 1 7 6 C H A PTER 5 :. DiSCU SSiON. 1 7 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. INVESTIGA TlONS INTO KAMAHI DIEBACK. . . . . . . . . . . . . . . . . ..... . ... . . . . . . . ... . . . . . . . . . . . . . ... . ...... ..... . .177 KAMAHI ECOLOGy. . . . . . . . .. . . . . .. . . . . . . . ... . ... . . . . . . . . . . . . . . .. . ...... . . . . . . . . . . . . . . . . . . . . . . ... . . . . .. . . . . . . . .. . . . . ... . . .180 UNDERSTANDING THE DIEBACK PROCESS.... . . .. . . ... . . . ... ...... . . .................. . . .... .... . . . . . .....181 IMPLlCATIONS FOR THEORIES OF DIEBACK . . . . . . . .......... . . ... . ..... . . . . .............. . ... ...... . . . . . .183 . ... . . . . . . . . 1 86 Model of Dieback Management. . CONCLUSIONS FOR KAMAHI I N TONGARIRO NATIONAL PARK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 9 . . . . .. . .. . . . . .. . . . . . .. . . . . .. . . . . . . . . . . . . .. . . . .. . . . .. . . .. . . . . . . . . . . . .. . . . . . . .. MANAGEMENT IMPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9 1 1. TREA TMENT OF DIEBACK ... . . ............ . . ... . ... . . . ... ... . . ...... . . .... . . ....... . . ... . . . . . . . ....... . . . . ... .1 91. 2 . MAINTENANCE OF POSSUM DENSITY..... . . . .............. . .. . . ............... . . . .. . . ....... . .... ......1 91 3. DISSEMINATION OF INFORMATlON TO PUBL iC . . . . . . . . . . . ..... . . . . . . . . ... . . . ... . . ... . . . ... . . . . . . . .1 91 4 . RESEARCH ... . . . . . . .. . . ... . . . . . ... . . ... ... . . . . ... .... ... . . . . . . . . . . . . . . ....... . . . . . . ... ...... . . .... ..... . . .......... ... 1 9 1. FUTURE RESEARCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9 2 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9 4.

(11) xiii. ABSTRACT. Forest dieback is a complex area of study that has led to the development of a n umber of theories or models which purport to explain it. These models are examined using the examp l e of kamahi dieback in Tongariro N ational Park. There h as long been concern over the health of kamahi in the Park and it is thought kamahi could be in a state of decli n e . A survey on three transects in the area of the Park where dieback is most apparent compared kamah i health to possible predisposing, triggering and hastening factors (the decline-disease theory of forest dieback) to determine their role in any d ieback.. Possums, pinhole borer, and Sporothrix fungus were highlighted in l iterature. as l ikely triggering factors in kamahi d i eback; an experiment examined their role: possums were excluded from trees, pinhole borer attack simulated , and h ealthy trees infected w ith Sporothrix, while unhealthy trees were treated with fungicide. To assess the effect of canopy health and vertebrate b rowsers on regeneration ( rege neration is important in both the cohort senescence theory and the model of stand succession), another experiment was conducted using open and exclosure plots under healthy and thinning canopies. A second survey assessed the overall health of kamahi in the area, and compared site and tree factors to levels of die back. The survey of an area with high apparent dieback foun d 1 4 % of kama h i stems were dead. There was some evidence that age predisposed stems to d ieback, and Sporothrix was identified as accelerating stem death; no causal factor was d eterm ined.. The experiment found no evidence that possums, pinhole borer, or Sporothrix were affecting the h ealth of kamahi at this site. Sites under a thinning cano py i n the regeneration study were much more variable in composition than sites under the h ealthy canopy; while sites in exclosure p lots had higher densities of seedl i n gs than sites that browsers had access to. Sites covered by the broad-scale survey contained very few unhealthy or dead kamahi trees, and none of the factors studied seemed to be impacting on the health of kamahi . There were more small (between 50 cm and 2 m ) sapl ings present a t s ites with more d ead kamahi trees. It was concluded that kamahi in T ongariro National Park is generally i n a healthy state, and not undergoing d ecline; although localised dieback m ay b e very high. Possums, pinhole borer and Sporothrix are not having a l arge effect o n kamahi health in this area. Vertebrate browsers may be maintaining regeneration at a level below natural . Comparison between the theories of dieback, s uccession and the kamahi data indicate that the successional model may best explain the pattern of kamahi d ieback..

(12) xiv. The models of dieback and s uccession can be inserted into an overriding model of d i eback management, which will indicate the best path for investigating forest d ieback..

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(14)

(15) Introduction. C hapter 1:. 1. The d i e back phe nome non with reference to kam a h i. (Weinmannia racemosa). i n Tongariro N ational Park, N e w Zea l a n d. Death is a n atural event, but accelerated death can be more or less natural. Trees may die for many reasons, and over many scales. Some of these reasons are obvious, such as fire or flood i ng , or severe d roughts, pollution or pestilence (Mueller-Dombois, 1 988). The terms below do not refer to these types of death , but rather to d eath w here there is no clear cause, and often a combination of factors involved. Although many trees pass through a period of deterioration or senescence before death, this thesis uses 'dieback'to refer to a category of 'disease' that does not connote any specific cause - it equates to S i nclair's ( 1 988) 'decline d isease' . D ieback implies that there is no primary agent capable of causing such death in healthy trees ( H o usto n , 1992). An almost d efining feature of this type of tree d eath is the lack of agreement among researchers o n the cause and importance of the factors i nvolved (Manion, 1 99 1 ) , and this is the issue addressed in this thesis.. The following terms are used in this thesis: Disease. m alfunctioning of host cells and tissues that results from contin uous. -. i rritation by biotic (e.g. pathogens) or abiotic ( environmental) factors, and l eads to d evelopment of symptoms (Agrios , 1 988; Beever, Forster, R ees-George, Robertson, Wood & Winks, 1 996) ; Dieback. progressive loss of health and d eath o f shoots, branches or roots,. -. crown foliage lost o ut of season, may lead to 'stag heads' and death (Agrios, 1 988; M u el l e r - D o m b o i s ,. 1 992) ;. Stand-level dieback - synchronous dieback of the canopy of whole stands or. parts thereof, rath e r than isolated trees ( M u e l l e r- Do m bois, 1 988; Steel, 1 989); Decline. widespread d ieback, to the extent that a species or vegetation type is. -. d eteriorating (Manion & Lachance , 1 992b) ; N at u r a l. -. l arge ly non-anthropoge n i c ;. W a l d st e r b e n - l iterally 'forest d eath ' , applies to 'novel forest decline' i n. E urope, a n d particularly Germany ( Kandler, 1 992) ..

(16) 2. Introduction. DIEBACK. Stand-level d ieback occurs over a wide spectrum of forest types and around the globe, and i s receiving i ncreasing interest from ecologists (Steel, 1 989; Mueller-Dombo i s , 1 993).. It is b e i n g investigated in many countries, in both southern a n d northern. h em isphe res (for example, Agyeman & Safo, 1 997; Akash i & M ueller-Dombois, 1 99 5 ; A rentz, 1 98 3 ; Auclair, Lill & R ivenga, 1 996; Balakrishn an & M ueller­ Dombois, 1 983; Fisher, 1 997; Haemmerli & Schlaepfer, 1 993; H in richsen , 1 98 7 ; Hosking & H utcheso n , 1 986; Houston , 1 974; Huettl & M u eller-Dombois, 1 993; Jane & G reen , 1 983; Kandler, 1 992; Landman n , 1 993; Landsberg , 1 990; M an i o n & Lachance, 1 992a; Mueller-Dombois, 1 988; Ogden, Lusk & Steel, 1 993; Payton, 1 98 7 ; Waring, 1 98 7 ; Ziegler, 1 988) .. It is certain ly not a new phenomenon, and i n. many cases i s d u e t o 'natural' causes (Muefler-Dombois, 1 987).. H owever, i t i s often. very d ifficult to d istinguish between those and anthropogenic causes of d ieback. There is a tende ncy to blame people in some way for any widespread d eath of trees i n the absence of an obvious cause (Mueller-Dombois, 1 986), to the extent that in many industrial countries, particularly European, dieback is always seen as a new and anthropogenic problem ( M ue l ler-Dombois, 1 988). Franklin et al. ( 1 987) comment that tree d eath is an extremely complex phenomenon, and often represents an arbitrary point on a continuum of d eterioration ; the factors influencing death may not be the factors that were influencing health. They stress tree d eath as part of the stand dynamic, and the consequence of the same multiple contributing factors that affect that dynamic.. M ueller-Dombois ( 1 983a) adds that. dieback does not end the life of the community, but that succession and community dynami cs contin u e in spite of it; further, dieback will have special effects on the succession i n those stands, for example in allowing podocarps to be released.. The l iterature on d ieback a round the world is extensive: there have been symposia and text books published o n the subject (e.g. Manion & Lachance, 1 992a; H u ettl & M ueller- Dombois, 1 993) .. I n the n orthern hemisphere a i r pollution is often the first. factor blamed for any d ieback phenomenon, while in the Pacific region similar patterns of d i eback occur l argely in the absence of high levels of industrial pollution, so othe r explanations a re explored ( M ueller- Dombois, 1 983b) . I n N ew Zealand , there has been research on a variety of taxa exhibiting d ieback in a variety of areas, and with various causes suggested. Browsing by the Australian brushtail possum ( Trichosurus vu/pecula) had been the accepted cause of d ieback in.

(17) Introduction. 3. forests dominated by rata (Metrosideros spp.) and kamahi ( Weinmannia racemosa) (as reviewed by Batcheler, 1 983) . R ecently, it has been realised that the problem i s more complex, also i nvolving, for example, stan d structure and regeneration dynamics ( Payton , 1 988), as well as a pletho ra of other factors. On the H uiara u range ( U rewera region) , where podocarps were observed to be declin ing , i ntroduce d feral browsers were initially blamed , but red uced precipitation effectiveness is now believed to be the cause (Grant, 1 963) . I n the Kaimai Range, again it was thought that introduced browse rs were to blame for the deterioration in forest h ealth (Jane & G reen, 1 983) .. It is now understood that low l evels of soil n utrients were reducing. plants' ability to respond to drought and d isease, and deer were then affecting the ability of the forest to recover. The 'abnormally high mortality' of canopy trees in the beech forests of the northern R uahine Range in the early twentieth century is believed to be due to the effect of d rought ( G rant, 1 984). Dieback of pohutukawa on White Islan d was found to be largely due to toxic fumes from volcanic activity (Clarkson & C larkso n , 1 994) . Thus many factors have been implicated in forest decline in New Zealand. I nternationally, there has been a move towards developing general models of d ieback, or of forests to explain the dieback occurring within them..

(18) 4. Introduction. M O D E LS OF D I E BACK. From i nformation on specific cases of dieback, a variety of theories o r models have been developed that seek to g ive more general explanations for forest d ieback. These models highlight the ecological processes d riving d ieback, as opposed to simply describing its purported conservation significance or visual impact. The most general model is f rom H ouston ( 1 984): 1 . GENERAL MODEL O F DIEBACK. � � �. Healthy tree. stress. 2 Altered tree (dieback begins) more stress. 3 Tree altered more (may lose ability to respond to g ood conditions) o rganisms of secondary action. 4 Tree invaded , may be killed Step 1 begins with a healthy tree, that becomes stressed . If t h e tree is stressed enough, it will alter its d evelopment as a response, often reducing growth as d ieback is initiate d . If t h e stressed tree i s exposed t o further stress, i t may become so altered that it is unable to respond to favourable conditions, such as a respite f rom d rought. At this point the tree is effectively 'doomed', and attack by o rganisms of secondary action will f i n al ly kill it. The type of stress is not specifie d , b ut any stressor of trees w i l l fit, for example d rought, b rowse pressu re , n utrient deficiency o r acid rai n .. The. organi sms of secondary action are often the proximate causes of tree death, and manifest as plague or pestilence, such as vascular wilt d iseases, root rots o r i nsect attack. As they are so often associated with death, they tend to be blamed for the d ieback, rather than the original stressor which caused the deterioration i n h ealth that leads to d eath ( Hosking , 1 993b; Hosking, 1 993a) . M ueller-Dombois ( 1 986) h igh lights the need to focus more o n the structure of forests exhibiting dieback, and to examine their spatial and temporal patterns, habitat relationships and associated vegetation and successional responses, in order to assess what is d rivin g the d ieback, and whether it is really a problem for the forest. The following models provide frameworks withi n which these can be studied ..

(19) Introduction. 5. 2. DECLIN E DISEASE THEORY OF STAND-LEVEL DIEBACK This theory was d eveloped by Houston ( 1 974) , and is d iscussed f urther by M u eller­ Dombois ( 1 988) and Manion ( 1 99 1 ) . I t sees dieback a s a three step process o r chain reaction , and is largely a re-expression of the previous model, with the three stages of this model corresponding to the three a rrows (or stressors) of the general model :. Predisposing factors. 2. ". Precipitating factors. ". 3 Hasten ing factors. ( h e a lt h. .. d e c l i n e ). Predisposing factors affect a stand's susceptibility t o d ieback. Stand structure i s consid e re d a n i m po rtan t factor, with singl e-aged stands being particularly susceptible as they approach senescence. Extrem e edaphic conditions and recu rring perturbations can also predispose a stand to d ieback. Landmann ( 1 993) states that stands where soils are rich i n n utrients but 'physically u nfavou rable' (for example, o n steeply sloping sites) are perhaps the most predisposed to d ieback. The argument is that these stands will mature most rapidly, without the n ecessary d evelopment to avo i d the impact of mild stresses, for example a well-d eveloped root-system to avoid d rought or n utrient stress. This stage is similar to step 1 of Houston's ( 1 984) model (see above ) , w it h trees h ealthy. P recipitating factors act to synch ronise d eath in stands that contai n trees p redis posed to die. Precipitating factors may be abiotic stresses, such as drought or severe storms, or biotic agents such as high l evels of animal browse ( M uelle r­ Dombois, 1 986). They trigger actual d eath of trees. This is the stage where dieback symptoms are first exhibited, and relates to steps 2 and 3 of the general model. H astening factors accelerate the d ieback, and are generally b iotic in nature , s uc h as pathogenic fungi, and i nsects o r other h erbivores (Muel le r- Dombois, 1 992) . They correspond to the 'organisms of secondary action' from the previous model (see above) . This theory has served to provide a focus for research on stand-level dieback, and can be used for d ieback events of natural or anthropogen i c nature (Mueller-Dombois, 1 988). Stewa rt ( 1 989: 243) goes so far as to say that 'all known e xamples of d ie back.

(20) 6. Introduction. i n N ew Zealand Nothofagus spp. , Metrosideros spp. , and beech/hardwood forests can be explained using this three-factor framework' .. It has been a very influential theory ,. and seems t o h ave become ubiquitous or all-pervasive in d ieback research . 3. COHORT SENESCENCE THEORY T h i s theory, d eveloped by Mueller-Do mbois ( 1 983a; 1 986) , d iffers from the previous model, which implies a disease or d isorder in the system , only in that it applies to, or d escribes, senescence and implies succession , which is part of the system. Whereas synchronous d ieback of single-aged stands would be treated as a sym ptom of a problem in the previous model, i n this model dieback i s a n ormal and i ntegral part of the system .. 1 . Catastrophic d isturbance allows large cohort to invade the s ite. '". 2 . Stand d evelopment proceeds; stands which are under similar conditions will remain synchronised demog raphically as they approach senescence ( the "". pred isposing factor of previous model). 3.. '". Pert urbations that usually only affect g rowth , now i nitiate d ie back i n stands. predisposed ("" precipitating factor of p revious model). ,. (leads to patchwork pattern of die back based on pattern of s ite suitabi lity). '". 4. Othe r factors may hasten decline after initial breakdown of canopy, and may result in death of all life stages and larger areas than a single 'stand' (patchwork breaks down) (. '". hastening factor of previous model). (successional g rad ient over time). This model o n ly applies to certain systems as it requires: a) an enviro n m e nt with catastrophic disturbances; b) s pecies able to take advantage of such d isturbances by rapid (re)invasion ; and c) that the widespread d isturbance occurs less frequently over the site than the generation turn-over of the species concerned . The above process may lead to successive cohorts becoming spatially reduced and out of p h ase w ith each other until another catastrophic disturbance resets the cycle..

(21) Introduction. 4. MODEL OF SUCCESSION Successional models may also include reference to d ieback stages, and there a re many examples of d ieback that seem to be part of the regeneration process of a species, and that operate without catastrophic d isturbances to start the cycle. This is classic gap­ phase regene ration. One such classic model of succession is included to show that d ieback occurs within an ecological system , and has profound significance on that system . This is important to remember, as the cause of d ieback is so often considere d t o be o utside t h e natural system , a n d thus upsetting t h e natural cycle. T h e model i s from Mayer and Neuman ( 1 98 1 , cited by Mueller-Dombois, 1 987) (fig 1 ) . For species, such as Nothofagus in New Zealand , and Metrosideros in Hawai'j, where d i e back is very important in succession, thi s model explains the timing and significance of dieback, without reference to any causal factors. These issues are investigated i n this thesis on kamahi d ieback in T ongariro N ational Park, New Zealand .. St and regenerat ion. St and-level. Mxed st ruet ure. Opt imum healt h of ----.. stand. St and senescence. Figure 1 Generalised model of stand succession from Muel/er-Dombois (1 987). Senescing stage is the longest, with more open canopy than the optimum health stage.. 7.

(22) 8. Introduction. TONGARIRO NATIONAL PAR K. Tongariro National Park in the central North Island of N ew Zealand (390 S , 1 75° E ; fig 2) is a park dominated by m ountains (figs 3 and 4) .. kilometres. 20 I. 10 I. o I Scale. i. 1 :400 000. Mt Tonganro. N. ... o. Mt Ngauruhoe ... o. .. / ....... ..,.­. /. ",-..".""'". I I I. ... r\, ..... \.,._. ,.., "'I I. (,��. .... ,,\.;.-. J. �. '. <'". ,..>. 'jI .... '1-. \. OhakUne. ..e:. I. I. "I. Mt Ruapehu. J. SH4. I I I. I. ,.../. /. I. '. .... ....;. I. / I I. /'. '-. ". ,,�. /. /. ./. /- __ tfII!I'""".--.. .......... /. �//. / I. ParK Boundary. �. SH49. Fig 2 Location of Tongariro National Park in the central volcanic Pla teau, North Island, New Zealand..

(23) Introduction. Fig 3 Tongariro National Park in win ter, showing mountains. Ngaurahoe (2291 m) is the conical mountain in centre, Tongariro (1967) the smaller, older mo untain to the right (photo G.Rapson).. -i. Fig 4 Ruapehu (2797 m) in Tongariro Na tional Park (photo G.Rapson).. 9.

(24) 10 Introduction. Due to its background, it contains relatively small areas of native forest, and has corresponding problems of encroaching weeds, edge effects, and introduced browsers. Park H i story I n 1 887, Ngati Tuwharetoa as represented by Te Heuheu , gifted the three mountains R uapehu, Ngauruhoe and Tongari ro to the government of New Zealand . Te Heuheu was concerned that these mountains, the ancestors of Ngati Tuwharetoa, would be d ivided and sold piece by piece to Pakeha, who had already shown their disrespect for the mountains. These mountains became N ew Zealand's first National Park (and the fourth i n the world) when Tongariro N ational Park was established in 1 894 and gazetted in 1 907. As the main concern of Ngati Tuwharetoa was for the integrity of the mountains, the original Park included only the peaks of Ruapehu, Tongariro and Ngauruhoe - 2600 hectares containing very l ittle vegetation Following the recommendations of eminent N ew Zealand botanists Cockayne ( 1 908) and Turner ( 1 909), the Park was expanded with the purpose of i ncluding more vegetation types. This expansion has continued, and at present the Park includes over 80 000 ha ( Department of Survey and Land I nformation - Te Puna a Korero Whenua) and is a World H eritage area, The Park n ow constitutes a varied landscape, for example the volcanic mountains, plateaux, lakes and desert. It thus contains a diversity of vegetation types (Atkinson , 1 98 1 ; 1 985), from lowland podocarp/hardwood forests , through montane beech ( Nothofagus spp.) forests, subalpine shrubland , to alpine herbfields; from bogs and almost rainforest on the west, to the Rangipo Desert on the East; and also including areas of h eathland and tussockland. It was this diversity of vegetation that Cockayne ( 1 908) had so wanted to preserve. However the Park is not without its conservation problems, as the tussock lands are widely invaded by european heather ( Cal/una vulgaris) . Additionally, the health of the forests have caused concern to managers, for. example beech in the past (Skipworth, 1981), and today kamah i ..

(25) Introduction. 11. K A M A H I (WEINMANNIA RACEMOSA). Kamahi (sometimes called tawhero around National Park, or Kamai in Southland) is an important component of all but the higher altitude forest associations in Tongariro N ational P a rk (Atkinso n , 1 98 1 ) .. It is a non-offensive, p leasant-looking canopy tree,. g rowing up to 25 m tall, and to a trunk diameter of over 1 .2 m (Salmon , 1 980). It may grow as a single stemmed tree, or may assume a many-stemmed guise, and is often of epiphytic origi n with very irreg ular stems (Ward l e , 1 966) (fig 5 ) .. Kamahi l eaves. are thick, l eathery and serrated (fig 6) , with much variatio n in shape.. J uvenile. l eaves ten d to b e tri-foliate, and adult uni-foliate. Kamahi is endemic, and closely related to Weinmannia si/vico/a, which is the more northerly species, ranging from Waikato and the Bay of Plenty north to Mangonu i (Salmo n , 1 980) . Wardle ( 1 966) speculates that kamahi i s New Zealand's most abundant canopy tree, and comments that it probably associates with every other tree species present south of the Far North. It ranges from Auckland to Stewart Island, and from sea-level to around 1 1 00 metres above sea leve l , but may not be tole rant of drought and poorly drained sites. Kamahi produces racemes of white or red-tinged flowers, abundant some years (figs 7 and 8) , and less in others (pers.obs.). Flowers appear in late spring, and may pers ist as seed pods to the following year. The very small and abundant seeds are wind dispersed, and require a lit situation (although not direct sunlight) to germinate, b ut seedlings prefer shaded cond itions (Wardle, 1 966). Seedlings may be either epiphytic o r terrestrial in habit.. Kamahi saplings have extremely fast growth rates , and are the. most common canopy species present in forest gaps (Ogden, Fordham, P ilkington & Serra, 1 99 1 ) .. This leads to continual recruitment, and the typically all-sized. popu lation structure ( Lusk & Smith , 1 998) . Kamahi is thought to be an important species in successio n , particularly following disturbance (Wardle, 1 966) . And d ieback of kamah i may be an important part of the forest system, where podocarps can regenerate under kamahi, but not under adult podocarps (Beveridge, 1 973) ..

(26) 12. Introduction Fig 5 Kamahi stem, sho wing irregular nature on trees of epiphytic origin (photo G.Rapson).. Fig 6 Kamahi foliage (photo G. Rapson)..

(27) Introduction. Fig 7 (right) Kamahi branch sho wing a bundant white ra cemes of flo wers.. Fig 8 (below) Kamahi bush with seedpods (brown) and two ra cemes s till with flowers ( w h ite) .. 13.

(28) 14. Introduction. A I M S O F TH I S STUDY. Dead trees are an obvious feature of the forest of some areas of Tongariro National Park and have g iven rise to concern that kamahi forests may be in general decline. Possums h ave been widely assumed to b e causal in this situatio n , possibly in combination with insect and fungal pathogens. Kamahi in Tongariro National Park can be considered a case study of a d ieback phenomenon, in the context of models of forest d ieback. Superficially it appears to fit each mod e l , with the patchy mortal ity typical of decline d isease, cohort senescence and the successional model presented. H istory of Tongariro National Park is briefly reviewed, as well as aspects of the ecology of kamahi, as i mportant background i nformatio n . This research examines whether kamahi is in decline, and attempts to find the causes of the mortality. The aims of this thesis are : ( 1 ) to establish the extent of kamahi mortality (chapter 2a) ; (2) to examine the correlations between d ieback and possible predisposing and / o r triggering biotic, environm e ntal o r demographic features (chapters 2a a n d 2b, with 2b focusing o n an area of more severe dieback); (3) to establish causality of these relationships by the effect of their manipulation o n kamahi h ealth (chapter 3 ) ; (4) t o examine t h e role o f kamahi mortality in forest succession (chapter 4) ; and , (5) to exami n e the effect of browsing (largely by introduced mammals) i n constraining replacement o f kamahi (chapter 4) . Underlying these aims is the d esire to identify which (if any) of the various dieback models applies in this case study, and to suggest management strategies for identifying d ieback problems and deciding on the most appropriate course of action. APPROACHES The approach taken i n this thesis to answer the preceding questions is a combination of surveys and experi ments. In order to understand the extent and patterns of kamahi mortality in the Park, two surveys were undertaken.. The first, a broad-scale survey. of kamahi habitats in and near the Park, aimed to assess the extent and scale of kamahi d ieback, and to suggest causes (chapter 2a) , it aims to give an overview of the situation rather than d i rectly add ressing any of the models. The effects of possible causes, such as possum browse, i nsect browse , and susceptibility to d rought and age, on kamahi health were tested by examining correlations between them and the level of d ieback observed in trees. The second survey focused on an area of the Park where kamahi mortality had been found to be heaviest (chapter 2b) . Using the decline-disease theory.

(29) Introduction. 15. of forest d ieback, this survey aimed to ascertain the chi ef predisposing, triggering and accelerating factors i n kamahi d ieback, by comparing each of the most likely factors to m easures of kamahi stem or stand health. The structure of the fieldwork for chapter 2 b was largely determined by the Department of Conservation, who located and marked the transects and each of their quadrats, as well as n umbering each stem withi n each quad rat. The Department of Conservation also collected much of the data describing each stem, although all but Diameter at B reast Heig ht were later checked by myself i n the fiel d . A review o f t h e l iterature on h i g h levels of kamahi mortality elsewhere in N ew Zealand highlighted browsing by the introduced b rushtai l possums, attack by Platypus spp. pinhole borer, and i nvasion by Sporothrix fungus as being the most likely, o r m ost commonly d iscussed, causes. I n this study, an experiment was designed and executed to examine the impacts of these factors, both separate and i nteracting, on kamahi h ealth i n Tongariro National Park (chapter 3), and to test any findings from the two surveys. The impacts of red ucing possums' access to h ealthy and unhealthy trees (by banding stems ) , excluding fungi from u n h ealthy trees ( using systemic fungicide ) , i ntroducing Sporothrix to healthy trees, and boring large n umbers of holes i n healthy trees (as Platypus spp borer often do) were tested. This experiment uses the concept of triggering factors from the d ieback models: it identifies the factors m ost l i ke ly to trigger a decline in health in kamahi, and assesses their ability to be c ausative. Regeneration at sites under a healthy canopy as opposed to a less healthy canopy, and the effect of excluding larger animals were looked at to assess the importance of stand level d i e back in succession (chapter 4).. If regeneration is markedly d ifferent. under a thinning kamahi canopy than under the h ealthy canopy, particula rly if seedlings of canopy species appear more suited to an unhealthy canopy, then stand level kamahi d ieback is likely to be important in the forest system (as in the successional model presented by Beveridge, 1 973). The effect of exoti c herbivores is investigated to d etermi n e the role they a re having in this process, in particular whether suppression of seed l i ngs by browsing will be having an effect on levels of successful regeneration. H ig h levels of regeneration (in the absence of herbivory) are features of the cohort s en escence and successional models (though not necessarily restricted to , them). The thesis concludes with a revision of the evidence for proportion and scale of kamahi d i eback i n the context of the dieback models, identifies which of these models.

(30) 16. Introduction. (if any) best fits the d ata, and proposes a model for i nvestigation and management of high tree mortality i n native forests..

(31) Introduction. 17. R E FERE NCES. Department of Survey and Land I nformation - Te Puna a K6rero Whenua Parkmap Tongariro National Park, I nfomap 273.04, EDITION 4 . Agrios, G . N . 1 988. Plant Pathology. Academic P ress, San Diego. 803 p p . Arentz, F. 1 983. Nothofagus d ieback on M t . Giluwe, Papua New G uinea. Pacific Science 3 7 : 453-458. Atkinson, I .A . E . 1 98 1 . Vegetation Map of Tongariro National Park, North Island, New Zealand. Wellington , New Zealand Department of Scientific and I nd ustrial Research. Atkinso n , I .A . E . 1 985. Derivation of vegetation mapping units for an ecological survey of Tongariro National Park, North Island, N ew Zealand . New Zealand Journal of B o ta ny 2 3 : 3 6 1 -378. Batcheler, C L 1 983. The possum and rata-kamahi d ieback i n N ew Zealan d : a review. Pacific Science 3 7 : 4 1 5-426. Beever, R . E . , R.L.S. Forster, J . Rees-George, G . I . Robertson , G .A. Wood and C.J. Winks. 1 996. Sudden decline of cabbage tree ( Cordyline australfs) : search for the cause. New Zealand Journal of Ecology 20: 53-68. Beveridge, A . E . 1 973. Regeneration o f podocarps in a central North Island forest. N e w Zealand Journal of Forestry 1 8 : 23-35. Clarkso n , B.O. and B.R. Clarkson. 1 994. Vegetation decline following recent e ruptions on White Island (Whakaari), Bay of Plenty, N ew Zealand. New Zealand Journal of Botany 3 2 : 2 1 -36. Cockayne, L. 1 908. Report on a Botanical Survey of the Tongariro National Park. Department of Lands, Wellington. 42 pp. Frankli n , J . F . , H.H. Shugart and M.E. H armon. 1 987. Tree death as an ecological p ro cess. BioScience 3 7 : 550-556. G rant, P .J. 1 963. Forests and recent climatic history of the H uiarau range , U rewera region, North Island. Transactions of the Royal Society of New Zealand. Botany. 2 : 1 44- 1 72 . G rant, P . J . 1 984. D rought effect on high-altitud e forests, R uahine Range, North I slan d , N ew Zealand . New Zealand Journal of Botany 2 2 : 1 5-27. H aemme rl i , F. and R. Schlaepfer. 1 993. Forest decline in Switzerland: a review. Pages 3-1 7 in Huettl , R . F . and D. Mueller- Dombois (eds.) Forest Decline in the A tlantic and Pacific Region. Springer-Verlag , Berlin . Hin richsen, D . 1 987. The forest decline enigma - What underlies extensive d ie back o n two continents? BioScience 37: 542-546. H osking , G . P . 1 993a. Nothofagus decline in N ew Zealand : separating causes from symptoms. Pages 275-279 in H uettl, R . F. and D. M ueller-Domboi s (eds.) Forest Decline in the A tlantic and Pacific Region. Springer-Verlag , Berli n , H e i d e lberg . H osking, G . P . 1 993b. Seeing is not believing: I nsects as symptoms and not causes. New Zealand Entomologist 1 6 : 1 -4. Houston , D . R . 1 974. Diebacks and d eclines: d iseases initiated by stress, including defoliation. International Shade Tree Conference Proceedings 49: 73-76. H ouston , D . R .. 1 984. Stress related to diseases. Arboricultural Journal 8 : 1 37 -1 49 .. H ouston , D . R . 1 992. A host--stress--saprogen model for forest d i e back-decli n e diseases. Pages 3-25 in Manion, P . D . and D. Lachance (eds.) Forest Decline Concepts. American Phytopathological Society, St Pau l , Minnesota..

(32) 18. Introduction. H u ettl, R . F . 1 993 . Summary and concluding remarks. Pages 35 1 -358 in H u ettl, R . F. and D. M ueller-Dombois (eds.) Forest Decline in the A tlantic and Pacific Region. Springer-Verlag, Berl i n . H u ettl , R . F. a n d D . M ueller- Dombois ( E d ) . 1 993. Forest Decline in the A tlantic and Pacific Region. Springer-Verlag , Berl i n , Heidelberg . H unter, I . R . 1 993. The role o f n utrition i n forest decline - - a case study o f Pinus radiata in New Zealand. Pages 293-306 in H uetti, R . F . and D. Mueller­ Dombois (eds.) Forest Decline in the A tlantic and Pacific Region. Springer­ Verlag , Berl i n . I n n e s , J . L . 1 993. Some factors affecting t h e crown d ensity o f t rees in G reat B ritain based on recent annual surveys of forest condition. Pages 40-53 in H uettl, R . F. and D. M ueller-Dombois (eds.) Forest Decline in the A tlantic and Pacific Region. Springer-Verlag, Berl i n . J a n e , G .T. and T . G .A. Green. 1 983. Episodic forest mortality i n t h e Kaimai Ranges, North Islan d , New Zealand . New Zealand Journal of Botany 2 1 : 2 1 -31 . Kandler, O. 1 992. The German forest decline s ituation : a complex d isease o r a complex of d iseases. Pages 59-84 in Manion, P . D . and D. Lachance (eds.) Forest Decline Concepts. American Phytopathological Society, St. Paul, Minnesota. Landmann, G . 1 993. Role of climate, stand dynamics and past management in forest declines: a review of ten years of field ecology in France. Pages 1 8-39 in H uettl , R . F. and D. M uel ler-Dombois (eds.) Forest Decline in the A tlantic and Pacific Regions. S pringer-Verlag, Berl i n . Landsberg, J . 1 990a. Dieback o f rural e ucalypts: Does insect herbivory relate to dietary q uality of tree foliage? A ustralian Journal of Ecology 1 5 : 73-87. Landsberg , J . 1 990b. Dieback o f rural e ucalypts: R esponse o f foliar dietary quality and herbivory to defol i ati o n . A ustralian Journal of Ecology 1 5 : 89-96. Landsberg, J . 1 990c. Dieback of rural eucalypts: the effect of stress on the nutritional quality of foliage. A ustralian Journal of ECOlogy 1 5 : 97- 1 07. Lusk, C . H . and B . Smith. 1 998. Life h istory d ifferences and tree species coexistence i n a n old-growth N e w Zealand rain forest. Ecology 7 9 : 795-806. M an ion , P . D . 1 99 1 . Tree Disease Concepts. Prentice Hall, Englewood Cliffs, N ew J ersey. 402 pp. Manion, P.D. and D . Lachance ( Ed) . 1 992a. Forest Decline Concepts. American Phytopathological Society, St Paul, Minnesota. Manion, P. D. and D. Lachance. 1 992b. Forest decline concepts: an overview. Pages 1 81 - 1 90 in Manion, P . D . and D. Lachance (eds.) Forest Decline Concepts. American Phytopathological SOCiety, St. Paul, Minnesota. Mueller-Dombois, D. 1 983a. Canopy dieback and successional processes in Pacific forests . Pacific Science 3 7 : 3 1 7-325 . M ue l ler-Dombois, D .. 1 983b.. Concluding synthesis.. M ue ller-Dombois, D .. 1 983c.. I ntroductory statement.. Pacific Science 3 7 : 483-48 9 . Pacific Science 3 7 : 3 1 3-3 1 6 .. M ueller-Dombois, D . 1 986. Perspectives for an etiology of stand-level d ieback. Annual Review of Ecology and Systematics 1 7 : 221 -243. M ue l ler-Dombois, D.. 1 987.. N atural d ieback in forests.. BioScience 3 7 : 575-583.. M ueller-Dombois, D . 1 988. Towards a unifying theory for stand-level d ieback. G eoJo urna / 1 7 : 249-25 1 . M uelier-Dombois, D. 1 992. A natural d ieback theory, cohort senescence as an alternative to the decline d isease theory. Pages 26-37 in Manion, P . D . and D. Lachance (eds.) Forest Decline Concepts. American Phytopathological Society, St Paul, Minnesota..

(33) Introduction. 19. M ueller-Dombois, D . 1 993. B iotic i m poverishment and climate change: g lobal causes of forest decline. Pages 338-348 in H u ettl, R . F. and D. M ue ller-Dombois (eds. ) Forest Decline in the A tlantic and Pacific R egion. Springer-Verlag, Berlin. Ogd e n , J . , RA. Fordham, S . Pilkington and R G . Serra. 1 99 1 . Forest gap formation and closure along an altitudinal gradi en t in Tongariro N ational Park, N ew Zealan d . Journal o f Vegetation Science 2 : 1 65- 1 72 . Payton, \ . 1 988. Canopy closure , a factor i n rata ( Me trosideros) - k a m ah i ( Weinmannia) forest decline i n Westland, N ew Zealand . New Zealand Journal of Ecology 1 1 : 39-50. Salmon, J .T . 1 980. The Native Trees of New Zealand. A . H . & A.W. Reed Ltd. , Wellington , NZ. 384 pp. Sinclair, W.A. and G .W. Hudler. 1 988. Tree declines: four concepts of causality. Journal of A rboriculture 1 4 : 29-35 . Statham , H . L. 1 995. The brushtail possum ( Trichosurus vulpecula Kerr) and rural d ieback in Tasmania. in A ustralian Vertebrate Pest Control Conference, Tasmania. pp 2 1 7-223 . Steel, M .G . 1 989. Mountain beech forest on Mt Ruapehu: dynamics, disturbance and dieback. U npub. thesis, Univers ity of Auckland. Stem mermann, L. 1 983. Ecological studies of H awaiian Metrosideros i n a successional context. Pacific Science 37: 361 -37 3 . Stewart, G . H . 1 989. Ecological considerations of dieback in New Zea la nd's i ndigenous forests. New Zealand Journal of Forestry Science 1 9 : 243-249. Turner, E . P . 1 909. Botanical exami n ation of the H igher Waimarino D istrict. Department of Lands. Report. C . 1 1 . Wardle, P . 1 966. B iological flora of N ew Zealand 1 . Weinmannia racemosa Linn. f. (Cunoni aceae). Kamahi. New Zealand Journal of Botany 4: 1 1 4- 1 3 1 . Waring, R H . 1 987. Characteristics of trees pre disposed to die. BioScience 3 7 : 569574.

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(36) Survey s. C hapte r 2 :. S u rveys of Kamah i. (Weinmannia racemosa). 21. d ieback i n. To n g a ri ro N a ti o n a l Park. I NT R O D UCTION. As discussed i n the previous chapter, forest d ieback or d ecli n e is an i m po rtant and globally widespread issue, with many d ifferent theories which attempt to describe and explain it. These theories tend to separate into those that focus on the mortality as an unnatural, anthropogenic problem, and those which focus on periods of i ncreased m o rtality as naturally occuring within the forest system, and necessary to that system's survival.. I n order to examine the vali dity of the more important of these. theories, an example of forest dieback is n ecessary. Kamahi ( Weinmannia racemosa) is a very important canopy tree species in the forest of Tongariro National Park, making up a h uge proportion of the total basal area of the forest on the western and southern sides of the Park (approximately 45 % of the basal area of l ive trees on the western lower slop es of Hauhungatahi is kamahi (unpub. DOe data)). Large scale d ieback of kamahi has been noticed on the western side of the Park. The cause of the high rates of mortality observed has been m uch speculated on, with possibil ities rang i ng from those of an anthropogenic origi n , such as b rowsing by the i ntroduced brushtail possum ( Trichosurus vulpecula) , to completely n atura l causes, such a s d rought stress. It appears t o be a n ideal example with which t o examine forest d ieback theory. The following two sub-chapters (2a and 2b) present surveys that p rovide i nformation on kamahi mortality at two scales that can be compare d to the theorie s . An o bvious first approach for a study of species mortality i s a survey, covering areas where dieback is and is not evident, to determine the magnitude of the dieback 'probl e m ' , any patterns of mortality that may occur, and whether the m ortal ity appears to fit s uccessional models . A broad scale approach is n ecessary for such a widespread species which occupies a range of forest habitats and roles within the forest comm u n ity (being important in secondary succession, as well as an i mportant sub­ canopy and canopy s pecies). This approach allows generalisations on the environmental preferences and related vulnerabilities of the species to be made, as well as providing baseline data for i nterpreting its ecology . Chapte r 2a i nvestigates the level of kamahi mortality in the National Park area, and compares h ealth of trees to several site factors and possible causal factors, as well as to indices of regenerat io n ..

Figure

Figure 1 Generalised model of stand succession from Muel/er-Dombois (1987). Senescing stage is the longest, with more open canopy than the optimum health stage
Fig 2 Location of Tongariro National Park in the central volcanic Plateau, North Island, New Zealand
Fig 3 Tongariro National Park in winter, showing mountains. Ngaurahoe (2291 m) is the conical mountain in centre, Tongariro (1967) the smaller, older mountain to the right (photo G.Rapson)
Fig 6 Kamahi foliage (photo G. Rapson).
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References

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