UNIVERSITY of CALIFORNIA Los Angeles the Ecological Impacts Of
Total Page：16
File Type：pdf, Size：1020Kb
UNIVERSITY OF CALIFORNIA Los Angeles The ecological impacts of leaf drought tolerance A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Biology by Megan Kathleen Bartlett 2016 Copyright by Megan Kathleen Bartlett 2016 ABSTRACT OF THE DISSERTATION The ecological impacts of leaf drought tolerance by Megan Kathleen Bartlett Doctor of Philosophy in Biology University of California, Los Angeles, 2016 Professor Lawren Sack, Chair Climate change is expected to exacerbate drought for many plants, making drought tolerance a key driver of species and ecosystem responses. However, predicting responses from traits requires greater understanding of how physiological processes impact ecology. I developed new theory and methods and applied meta-analyses to characterize the ecological impacts of leaf drought tolerance. I compared the predictive ability of several traits for ecological drought tolerance and showed that the leaf water potential at turgor loss point, or wilting ( p tlp ), was the strongest predictor of species’ habitat water supply. I then showed that the main driver of p tlp was the osmotic potential at full hydration ( p o), or the solute concentration of a hydrated cell. Thus, plants achieve greater leaf drought tolerance by accumulating solutes in the leaf cells. I then developed a new method to rapidly estimate p tlp from measurements of p o. This method is 30x ii faster than the standard, making it feasible to characterize drought tolerance for many species within diverse clades and communities. Plasticity - the ability of individual plants to change trait values - is expected to strongly influence species’ responses to climate change. I meta-analyzed plasticity in p tlp and showed that, while most species became more drought tolerant under dry conditions, p tlp from wet or dry conditions and not plasticity predicted species distributions. Thus, p tlp measured in one season can reliably characterize most species’ ecological drought tolerances. Drought tolerance traits are also expected to impact species distributions within ecosystems through effects on habitat associations and competition. I showed that p tlp was a strong driver of habitat associations in a tropical community, and that drought tolerant species were significantly spatially clustered, suggesting drought tolerant species exclude sensitive species through hierarchical competition. Finally, plant drought tolerance is determined by multiple traits. I applied meta-analyses to evaluate general patterns in the relationships among hydraulic, stomatal, and wilting traits, and produce a framework for predicting plant responses to a wide range of water stress from one or two sampled traits. Overall, these findings provide insight into the impacts of leaf drought tolerance on plant ecology at community and global scales. iii The dissertation of Megan Kathleen Bartlett is approved. Philip Rundel Priyanga Amarasekare H. Jochen Schenk Stephen Hubbell Lawren Sack, Committee Chair University of California, Los Angeles 2016 iv TABLE OF CONTENTS ABSTRACT OF THE DISSERTATION …ii LIST OF TABLES …ix LIST OF SUPPLEMENTARY TABLES …x LIST OF FIGURES …xiii LIST OF SUPPLEMENTARY FIGURES …xv ACKNOWLEDGEMENTS …xvii VITA …xx CHAPTER 1: PREMISE OF THE DISSERTATION …1 REFERENCES …5 CHAPTER 2: THE DETERMINANTS OF LEAF TURGOR LOSS POINT AND PREDICTION OF DROUGHT TOLERANCE OF SPECIES AND BIOMES: A GLOBAL META-ANALYSIS ABSTRACT …8 INTRODUCTION …9 MATERIAL AND METHODS …15 RESULTS AND DISCUSSION …16 CONCLUSIONS …29 TABLES …32 FIGURE CAPTIONS …33 FIGURES …36 SUPPLEMENTARY MATERIAL …44 REFERENCES …57 v CHAPTER 3: RAPID DETERMINATION OF COMPARATIVE DROUGHT TOLERANCE TRAITS: USING AN OSMOMETER TO PREDICT TURGOR LOSS POINT ABSTRACT …76 INTRODUCTION …77 MATERIAL AND METHODS …79 RESULTS …85 DISCUSSION …89 TABLES …93 FIGURE CAPTIONS …95 FIGURES …97 SUPPLEMENTARY MATERIAL …101 REFERENCES …105 CHAPTER 4: GLOBAL ANALYSIS OF PLASTICITY IN TURGOR LOSS POINT, A KEY DROUGHT TOLERANCE TRAIT ABSTRACT …112 INTRODUCTION …112 MATERIAL AND METHODS …116 RESULTS …121 DISCUSSION …125 TABLES …130 FIGURE CAPTIONS …131 FIGURES …133 vi SUPPLEMENTARY MATERIAL …136 REFERENCES …147 CHAPTER 5: DROUGHT TOLERANCE AS A DRIVER OF TROPICAL FOREST ASSEMBLY: RESOLVING SPATIAL SIGNATURES FOR MULTIPLE PROCESSES ABSTRACT …161 INTRODUCTION …162 MATERIAL AND METHODS …166 RESULTS …170 DISCUSSION …173 TABLES …180 FIGURE CAPTIONS …183 FIGURES …185 SUPPLEMENTARY MATERIAL …187 REFERENCES …224 CHAPTER 6: RESOLVING THE TEMPORAL SEQUENCE AND CORRELATIONS OF PLANT DROUGHT RESPONSES: COORDINATION AMONG STOMATAL, HYDRAULIC, AND WILTING TRAITS ABSTRACT …230 INTRODUCTION …231 MATERIAL AND METHODS …234 RESULTS AND DISCUSSION …235 TABLES …245 FIGURE CAPTIONS …246 vii FIGURES …249 SUPPLEMENTARY MATERIAL …252 REFERENCES …287 CHAPTER 7: CONCLUSIONS AND FUTURE DIRECTIONS …315 REFERENCES …321 APPENDICES: SUPPLEMENTAL METHODS 2.1 …323 SUPPLEMENTAL RESULTS AND DISCUSSION 2.1 …326 SUPPLEMENTAL RESULTS AND DISCUSSION 2.2 …329 SUPPLEMENTAL REFERENCES FOR CHAPTER 2 …331 SUPPLEMENTAL METHODS 4.1 …335 SUPPLEMENTAL METHODS 4.2 …337 SUPPLEMENTAL METHODS 4.3 …338 SUPPLEMENTAL METHODS 4.4 …341 SUPPLEMENTAL RESULTS AND DISCUSSION 4.1 …343 SUPPLEMENTAL REFERENCES FOR CHAPTER 4 …345 SUPPLEMENTAL METHODS 5.1 …347 SUPPLEMENTAL METHODS 5.2 …349 SUPPLEMENTAL METHODS 5.3 …352 SUPPLEMENTAL REFERENCES FOR CHAPTER 5 …XX …357 SUPPLEMENTAL METHODS 6.1 …XX …360 SUPPLEMENTAL REFERENCES FOR CHAPTER 6 …XX …361 viii LIST OF TABLES CHAPTER 2 TABLE 2.1. A primer of terms and symbols used in leaf pressure-volume (p-v) …32 analysis of water relations and drought tolerance. CHAPTER 3 TABLE 3.1. Woody species tested, origin, leaf type and pressure-volume curve …93 parameters and osmotic potential at full turgor measured using osmometry. CHAPTER 4 TABLE 4.1. The proportion of variance of drought tolerance traits explained by …130 climate. CHAPTER 5 TABLE 5.1. Hypothesized relationships between key ecological processes and …180 spatial patterns in trait variation. …181 TABLE 5.2. The habitat variable relationships to light and water supply underlying the hypotheses for their correlations with traits. …182 TABLE 5.3. The best-fit models predicting traits from habitat that were more predictive than autocorrelation. CHAPTER 6 TABLE 6.1. The symbol, definition, and functional significance of the drought …245 tolerance traits and the environmental water supply and plant water status variables. ix LIST OF SUPPLEMENTARY TABLES CHAPTER 2 TABLE S2.1. Summary of mean values ± standard error from a global database for …44 pressure-volume parameters and for leaf mass per area (LMA). CHAPTER 3 TABLE S3.1. Regression equations predicting pressure-volume curve measurements …102 of osmotic potential (π pv ) and turgor loss point (π tlp ) from osmometry measurements. CHAPTER 4 TABLE S4.1. Summary of site-level means for pre- and post-drought turgor loss …138 point (π tlp, ), the plasticity of π tlp (Δπ tlp ), and habitat water supply. TABLE S4.2. Summary of biome-level means for pre- and post-drought turgor loss …141 point (π tlp, ), the plasticity of π tlp (Δπ tlp ), and habitat water supply. TABLE S4.3. Mean pre- and post-drought treatment turgor loss point (π tlp ) and π tlp …142 plasticity for cultivars of 37 crop species. CHAPTER 5 TABLE S5.1. Mean trait values and percent relative abundances for each of the 43 …194 study species. TABLE S5.2. Species mean habitat variables. …196 TABLE S5.3. Species mean habitat variables, corrected for local quadrat density. …198 x TABLE S5.4. Correlation coefficients for univariate correlations among species …200 means for trait and habitat variables uncorrected for differences in quadrat density. TABLE S5.5. Correlation coefficients values for univariate correlations among ...202 means trait and habitat variables, with habitat means corrected for quadrat density. TABLE S5.6. Model structures used to predict habitat associations from trait means. …204 TABLE S5.7. Observed r values for the best-fit habitat models, compared to the 95% …205 confidence interval of the r values obtained from 1000 torus translations. TABLE S5.8. Pagel’s l values for each trait and habitat variable. …207 TABLE S5.9. Pagel’s l values for the univariate correlations among the trait and …208 habitat variables. TABLE S5.10. Pagel’s l values for each univariate correlation among the trait and …209 habitat variables, with habitat variables corrected by tree density …210 TABLE S5.11. Pagel’s l values estimated for the best-fit multivariate models between traits and habitat variables. CHAPTER 6 TABLE S6.1. Drought tolerance trait values compiled from the literature. …255 TABLE S6.2. Paired t-tests comparing each trait combination. …272 TABLE S6.3. Paired t-tests showing that the angiosperm temporal sequence is …274 xi largely robust to leaf phenology. TABLE S6.4. Paired t-tests showing that the angiosperm temporal sequence is robust …276 to differences in the shape of the stem vulnerability curves, but potentially influenced by the shape of the root vulnerability curves. TABLE S6.5. Univariate standardized maJor axis (SMA) correlations between each …278 pair of traits. TABLE S6.6. Univariate standardized maJor axis (SMA) correlations between each …279 pair of traits, including the stem and root hydraulic trait values interpolated from non-sigmoidally shaped vulnerability curves. TABLE S6.7. r 2, AICc values, and sample size for models predicting each trait as a …280 function of one other trait, Y min , and where relevant, phylogeny. TABLE