The world's forests sequester roughly a quarter of anthropogenic emissions of carbon dioxide and store it in wood. Assessing this carbon sink includes quantifying annual wood production, establishing baselines, and characterizing both long-term trends and inter-annual variability. Direct measures of forest wood production are often based on measures of individual tree growth along the stem, often taken at a single height: basal height (1.3 meters). This assumes that a measurement of wood production at a single height is representative of wood production along the whole stem. In violation of this assumption, it is known that trees do accumulate wood differentially along the stem, and that this longitudinal variability can change from year to year. Few efforts have been made to describe annual longitudinal variability, and quantify the error in estimated annual whole-stem wood production related to assuming that constant wood production along the stem. In the present study, I present a stem analysis of 30 Populus grandidentata to address this. Dendrochronological techniques are used to develop three chronologies: a traditional tree-ring width chronology from basal height, a novel chronology developed from tree rings grown in the crown of the trees, and a specific volume increment chronology calculated from measured annual volume increment data. A novel taper chronology is also presented. In Chapter 2, comparisons are made between the chronologies to explore differences in inter-annual variability, and the suitability for using tree-ring data from basal height as a proxy for annual wood production. Both basal and crown tree-ring width chronologies were strongly correlated with the volume chronology (r = 0.96 and 0.88, respectively), suggesting that the basal chronology is a superior proxy for stem volume. However, a chronology of taper along the stem indicates that the reliability of either chronology to represent specific volume increment (SVI) changes over time, resulting in different common signals, especially in the last decade of this dataset. If accurately capturing the relative year-to-year changes in stem wood volume is desired, stem dissection and development of an SVI chronology is required. In Chapter 3, two models that use tree-ring data to estimate annual wood production are compared to volume measurements from the stem analysis. The two models are a site-specific allometric model of biomass, and a simplified conic model of volume. Additionally the conic model is decomposed into the three dimensions of growth along which variability exists (around the circumference, along the length of the stem, and height) to identify which dimension introduces the most error when no variability in that dimension is assumed. Relative error (RE) analysis and regression analysis show that stem analysis is superior in cases where few trees are used and accurate measures of wood increment are needed. At the population level, the allometric and conic models show different strengths. Allometric models are more accurate than the conic model (RE = -16% and -18%, respectively) and are better for carbon budgets, whereas the conic model was more precise than the allometric model (R² = 0.94 and 0.86, respectively; interquartile range = 24% and 41%, respectively) and maintains inter-annual variability, which is necessary in cross-validation efforts. Decomposition of the conic model supports previous findings that height is the second most important parameter, following diameter at breast height, in models of woody tissue growth. In Chapter 4, basal, crown and specific volume chronologies are compared to eddy covariance estimates of carbon dioxide flux between the forest and the atmosphere, including net ecosystem exchange, gross primary production and ecosystem respiration. At the University of Michigan Biological Station (UMBS), crown-grown tree-ring widths from P. grandidentata individuals are good recorders of the inter-annual variability of net ecosystem production. Coupled with other environmental information from UMBS, these records implicate defoliating insects as a previously under-appreciated modifier of stand level respiration and gross primary production. These histories of ring widths, volume and taper have unique potential to improve our understanding of how carbon is stored in and flows through forests within the terrestrial biosphere. In the face of global change, forests will experience new stressors, and changes in frequency of known stressors, that reduce the ability of trees to store carbon in woody tissues. A diversity of tree-ring-based chronologies can describe the sensitivity of carbon stores to these stressors, improving predictions of how forests respond to environmental changes.

M.Sc. (Botany) / Please refer to full text to view abstract

Almonds are one of the first commercial nut trees to bloom in early spring and thus are susceptible to temperature patterns prior to and during bloom which affect bloom timing, bloom length, pollination and nut set. Data used in this project include yearly dates of 90% bloom from 1996-2006, bloom length in days and final crop yields in pounds per tree for Nonpareil and Mission varieties. Data were collected from the University of California Cooperative Extension reports on the 1993-2006 Regional Almond Variety Trials in Butte, San Joaquin and Kern Counties. Temperature pattern models in the form of Chill Hours (Chill Hour Model), Chill Units (Chill Unit Model), Chill Portions (Chill Portion Model) and Growing Degree Hours (GDH°) (Heat Model) prior to bloom were used to predict the date of 90% bloom for each variety, site and year. Temperature model results were compared to averaged actual dates of 90% bloom by site and variety used to predict bloom timing (Calendar Model). The relationship between bloom length in days and GDH° during bloom and the relationship between bloom length, GDH° during bloom and final crop yields were also evaluated. The average error in predicting the 90% bloom date for both Nonpareil and Mission was smaller using the Calendar Model compared to the four temperature pattern models. The Chill Portion model did not have significantly higher average error in predicting the date of 90% bloom than the Calendar model in Nonpareil. The Chill Unit and Chill Portion models had smaller errors in predicting 90% bloom date than the Chill Hour or GDH° model in Mission. GDH° during bloom was positively correlated with bloom length. GDH° during the first four days of Nonpareil bloom was significantly correlated with crop yields, with each additional GDH° during bloom correlated with a 0.4 lbs./tree increase in crop yield. Further research is needed on specific temperature thresholds and their relationship to physiological changes during almond bloom and pollination. The practice of monitoring chilling and heat accumulation will allow growers to anticipate bloom, prepare to optimize bee activity during bloom, and plan for possible crop yield variations due to adverse weather conditions during bloom in almonds.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20817号 / 農博第2257号 / 新制||農||1056(附属図書館) / 学位論文||H30||N5099(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 北島 薫, 教授 神﨑 護, 教授 小杉 緑子 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Loblolly pIne (Pinus taeda) and sweetgum (Liquidambar styraciflua) were grown in miniature stands at 7.6-cm spacings outdoors in open-top chambers (4.6 m in diameter and 3.5 m tall) for 16 months. Treatments consisted of ambient- and elevated-CO₂ , drought-stressed and well-watered, and stand type (monoculture and 50:50 replacement mixture). Gas exchange was measured monthly, growth parameters bimonthly. Loblolly pine carbon exchange rate (CER) was positive throughout the winter in all treatments and averaged 83% of summer rates. Between November 1994 and April 1995, relative crowding coefficient (RCC) of pine stem volumes increased regardless of CO₂ or water availability. RCC of pine biomass increased in droughted stands relative to well-watered stands, while RCC of sweetgum showed the opposite response. Based on these results increased atmospheric CO₂ concentrations will not affect the competitive outcomes of loblolly pine and sweetgum mixed stands: loblolly pine will continue to be more competitive on dry sites, sweetgum on wet sites. CER of loblolly pine and sweetgum, as well as soil respiration, were consistently significantly greater in elevated-C02 stands. CER in upper-canopy foliage was significantly greater than that of lower-canopy foliage for sweetgum. Loblolly pine, but not sweetgum, demonstrated a significant canopy position x CO₂ interaction, with upper-canopy CER greater only in elevated-CO₂ conditions. No consistent acclimation of CER to elevated CO₂ was statistically significant for either species, although acclimation response was stronger in sweetgum than in loblolly pine. / Master of Science

Understanding tree physiological responses to climate change is critical for quantifying forest carbon, predicting species' range change, and forecasting growth trajectories. Continued increases in temperature could push trees into conditions to which they are ill adapted -- such as decreased depth of winter snow cover, altered water regimes, and a lengthened effective growing season. A complicating factor is that in the northeastern United States, climate change is occurring on a backdrop of acid deposition and land-use change. In this dissertation, I used three studies to investigate the spatiotemporal nuances of resultant tree and sapling physiology to environmental change. First, I compared annual growth of co-occurring tree species (sugar maple, red spruce, red maple, yellow birch, and balsam fir) along an elevational gradient on Vermont's tallest peak: Mt. Mansfield. I found baseline differences in growth among species, and many annual variations were associated with species-specific events. Yet, protracted growth patterns, such as recent increases for red spruce and red maple, were correlated with increased temperature and cooling degree days (a heat index). For most species, temperature was positively associated with current growth, but negatively associated with growth the following year. This work demonstrated species' differences in response to change and the complex relationships between growth and temperature. Next, I analyzed how climate, environmental parameters, and site and tree factors related to recent, regional increases in red spruce growth. While there was variability in response to climate and acid deposition by elevation and location, site and tree factors did not adequately explain growth. Higher temperatures outside the traditional growing season were positively related to growth, while nitrogen deposition was strongly negative. However, if nitrogen inputs decline as projected then the strength of this relationship may decrease over time. These results suggest continued favorable conditions for red spruce in the near term as acid deposition declines and temperatures increase, provided precipitation remains adequate to support growth. Lastly, I used a replicated micro-catchment study to examine how four species of tree saplings (paper birch, quaking aspen, American chestnut and black cherry) responded to experimentally elevated temperature (2-4C above control) and reduced early winter snow (first six weeks of winter), depending on soil type. Soil and species characteristics strongly influenced sapling response. However, natural weather patterns during the treatment period were highly variable and muted or exacerbated results. Heating increased the potential photosynthetic period in the fall, causing an overall increase in leaf area. Many two- and three-way interactions of treatment factors were also detected. These outcomes demonstrate the variability in sapling response to a changing climate, as well as the complex interactions that occur among soil, species, and weather parameters.

<p dir="ltr">Deciduous leaf habits have evolved multiple times across many lineages in response to stresses like drought, cold, or darkness. This short, seasonal leaf lifespan allows trees to invest in photosynthesis during prime conditions and retreat to dormancy to survive less favorable conditions. The consequence of short leaf lifespan is that trees must perform an entire year's carbon capture into 6-8 months. This leads to leaves that are cheaper to produce than longer lived evergreen counterparts. As soon as challenging conditions have passed the leaves of deciduous trees expand rapidly; and this expansion has huge impacts on local ecosystems. Other plants like spring ephemerals have evolved to complete the majority of their life cycle before the upper canopy closes off. During the summer, deciduous leaves gather huge amounts of carbon for the trees to survive their dormancy. Finally, as the trees prepare to enter dormancy, nutrients are withdrawn from leaves as the chlorophyll is metabolized, causing them to transition from bright green to shades of red and yellow. In addition to other plants, people find the annual process of renewal on bud burst and tragic decline during senescence fascinating and culturally important. The aim of my thesis is to expand our understanding of winter deciduous leaves through every major stage of development, as well as to investigate how this process may shift due to climate change.</p>

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Red alder (Alnus rubra Bong.) is the only tree in British Columbia and the Northwest US to engage in actinorhizal symbiosis to fix atmospheric nitrogen. This study was conducted to explore the plasticity in growth and physiology among 58 17-year-old red alder families in response to variation in climate in two common garden plots, one at Bowser, BC and one at Terrace, BC. Physiological assessments included height and diameter growth, bud flush, water use efficiency as measured by δ13C, cold hardiness as measured by controlled freezing and electrolyte leakage, autumn leaf senescence, and instantaneous and seasonally integrated rates of nitrogen fixation as measured by acetylene reduction and natural abundance δ15N isotope analysis, respectively. Significant differences were identified among families for growth (height and diameter), bud burst stage, leaf senescence, cold hardiness, and bud nitrogen content. No significant differences among families were identified for water use efficiency as measured by δ13C, or for rates of nitrogen fixation as measured by either acetylene reduction or natural abundance δ15N. This study identified possible adaptive differences among red alder genotypes, especially in traits such as bud flush timing, cold hardiness, or nitrogen fixation and their respective contributions to growth. These differences often reflected a tradeoff between growth and the ability to tolerate an extreme environment. Cold hardiness results indicate that red alder families are well adapted to their climate of origin, and may not be able to acclimate sufficiently to a northward assisted migration of genotypes. Nitrogen fixation results demonstrated gaps in our current knowledge of Frankia distribution and impact on the actinorhizal symbiosis in British Columbia. / Graduate