Community ecology of New Guinea rainforest trees: Carbon storage, dynamics, and fungal endosymbionts A DISSERTATION SUBMITTED TO THE FACULTY OF UNIVERSITY OF MINNESOTA BY John Brady Vincent IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Advisor: Dr. George D. Weiblen August 2015 © John B. Vincent 2015 ACKNOWLEDGMENTS I owe great deal of gratitude to my advisor, George Weiblen for always supporting and encouraging my intellectual curiosity and academic growth, and giving me a truly unique and exceptional graduate experience in part by introducing me to a truly fascinating part of the world. I would also like to acknowledge and give a sincere thank you to my committee members Joe Knight, Georgiana May, and Rebecca Montgomery for all their time, effort, and thoughtful feedback throughout this process. These chapters have all been produced by highly collaborative experiences, benefitting from thoughtful comments and input from many outstanding researchers. Weiblen lab members, both current and former, Erin Treiber, Bega Inaho, Rebecca Sims, Bridget Henning, and Tim Whitfeld, were tremendous for their willingness to read, discuss, and counsel. Soil nutrient data in chapter two was collected, measured, and analyzed in collaboration with Clant Alok, Ben Turner, and Claire Baldeck. Chapter three benefitted greatly from many discussions with Peter Kennedy, Nhu Nguyen, and the May lab. These chapters were made possible by the tireless work and careful data collection of numerous partners. Fieldwork would not have been possible without the support of the staff and students of the New Guinea Binatang Research Center. Particularly Vojtech Novotny, Chris Dahl, and Pagi Toko for logistical support, Bruce Isua, Martin Mogia, Maling Rimandai, Kenneth Molem, and Joachim Yalang for field assistance, Mavis Jimbudo, Nancy Labun and Gibson Sosanika for their curatorial skills, Billy Bau and Clant Alok for their collaboration and unwavering interest, and all other staff and students in addition to those listed here for their companionship and laughter. My work in Wanang was made possible and welcoming by the entire Wanang community and in particular by Matthew Kumba, Filip Damen, Albert Mansa, and Dominic Rinan. i I would also like to thank Gail Kalli and the directors of graduate studies during my time in the Plant Biological Sciences Graduate Program - Jane Glazebrook, Gary Muehlbauer, George Weiblen, and Cindy Tong. This work was supported by National Science Foundation (DEB-0816749 and DEB-0515678), National Institutes of Health (ICBG 5UO1TW006671), Smithsonian Center for Tropical Research Science, University of Minnesota Graduate School (thesis research travel grant, Carolyn Crosby fellowship, doctoral dissertation fellowship), Bell Museum of Natural History (Dayton and Wilkie natural history grants), Plant Biological Science Graduate Program (summer fellowships, travel grants). Last but not least, I would like to thank my family and friends for their understanding, support, and encouragement. Teammates and adversaries in noon hoops, slow pitch, bowling league, and companions on many long bike rides played no small role in sustaining me, in particular Mark Ditmer, Jake Jungers, Nathan Springer, Pete Hermanson, and Peter Kennedy. To my father, James Vincent, for teaching me how to eat an elephant, my mother, Kerry Vincent, for never leaving a question unanswered, and to Jessie DiMariano for her support and patience during my time in the field – I wish her luck on her infinite pursuit of being the funny one. ii Community ecology of New Guinea rainforest trees: Carbon storage, dynamics, and fungal endosymbionts John B. Vincent Advisor: George D. Weiblen ABSTRACT This dissertation examines the community ecology of trees and fungal endophytes in the lowland rainforests of New Guinea. Forest inventory and soil nutrient data from a large permanent plot in addition to a chronosequence of regenerating forest were used to quantify carbon stocks and forest dynamics. These data were coupled with intensive sampling of foliar fungal endophytes at three sites to investigate local and regional variation in community composition of endosymbionts associated with a diverse sample of rainforest trees. The Wanang 50 ha forest dynamics plot is located in mature lowland wet rainforest in the Middle Ramu area of the Madang province in Northern Papua New Guinea. Established in 2009, the Wanang plot is the first spatially explicit, large-scale, long-term forest plot in Oceania aimed at studying forest dynamics and biodiversity through time. Chapter 1 investigated carbon storage in the Wanang forest dynamics plot and spatial and demographic variation in biomass. During the first census, every stem ≥1 cm in diameter at breast height (1.3 m above ground) was tagged, measured, and mapped to the nearest 10 cm. A subsequent species identification survey was carried out to associate every stem with a species or morphospecies concept. The first census at Wanang recorded a total 253,350 individual trees comprising 581 taxa, including 531 species and 50 morphospecies in 253 genera and 85 families. Our estimate of biomass iii averaged 222.3 Mg per hectare (95% CI: 211.3-232.7). This finding agrees closely with two previous estimates derived from a distributed network of small forest plots, suggesting this figure is a reasonable approximation of aboveground biomass in lowland forests in New Guinea. We found that there was significantly more carbon held in small trees than is typically assumed for lowland rainforest and that there is substantial fine- scale spatial variation in forest carbon (range: 161.5-324.43 Mg/ha). New Guinea forests have substantially lower biomass than tropical rainforests on average (global average: 373.7 Mg/ha), possibly driven by frequent natural disturbance. Chapter 2 explored the extent to which species composition and basal area in Wanang forest is associated with topography and soil nutrients. Additionally, the reputation that New Guinea rainforests are unusually dynamic was tested for the first time by comparing mortality rates and indicators of forest regeneration stage to other tropical rainforests. Soil nutrients and topography account for 29% of variation in tree species composition but only 4% of variation in basal area among 20 m by 20 m quadrats at Wanang. Basal area and gap phase character was significantly different than that observed at a comparable forest dynamics plot at Barro Colorado Island, Panama. Comparison of basal area in the mature forest of the Wanang plot to an adjacent regenerating forest chronosequence produced an estimate that 6% of the Wanang plot was naturally disturbed in the past decade. Disturbance at Wanang, in addition to tree falls, includes frequent small land slumps that result in catastrophic mortality of trees in portions of forest up to approximately one hectare. Mortality rate was also higher in Wanang than has been reported for any other lowland rainforest. These results lend quantitative support to the notion that New Guinea iv lowland rainforests are exceptionally dynamic. This dynamic character likely plays a role in the lower than average biomass and low density of large trees at Wanang described in chapter 1. A large forest plot, such as Wanang, offers the opportunity for biodiversity discovery and studies of species interactions otherwise not possible. Chapter 3 focused on the relative importance of host specificity and dispersal limitation in structuring community composition of fungal endophytes in rainforest trees. Fungi were isolated from a diverse sample of eleven tree species representing five genera in the lowland rainforests of Papua New Guinea. Collections resulted in the culturing and sequencing of 2,079 fungal endophytes from three sites. Sequences of the internal transcribed spacer (ITS) region, a common fungal ribosomal barcode, were clustered into molecular operational taxonomics units (MOTUs) at 95% similarity. A total of 670 endophytes were collected from a single site in 2010, comprising 61 MOTUs. A slightly modified collection method carried out at three sites in 2011 resulted in isolation of 1,409 endophytes belonging to 191 MOTUs. Composition of endophytes varied by host species and genus both within individual sites and in aggregate. Spatial proximity of host trees did not correlate with similarity of endophyte composition within species, genera, or trees (i.e. regardless of taxonomy). The endophyte community both within sites and regionally was comprised of few abundant host generalist and many rare taxa. Regional turnover of fungal endophyte taxa was low, illustrated by sites separated by hundreds of kilometers having high similarity in endophyte community composition. These findings are consistent with the hypothesis that host specificity plays a larger role than dispersal limitation in structuring fungal endophyte communities. The findings of these three v chapters provide a novel perspective of forest ecology in New Guinea that capitalized on the strengths of the long-term, large-scale plot setup of the Wanang forest dynamics plot. Additional plot censuses, focused studies of seed dispersal, and more intensive sampling of foliar endophytes will further elucidate the patterns described in this dissertation. vi TABLE OF CONTENTS ACKNOWLEDGMENTS ................................................................................................... i ABSTRACT ......................................................................................................................