Relationships Between Overstory and Understory Tree Composition and Light Environment in an Old Growth Forest, Adirondacks, NY

Density of tree seedlings and saplings can be considerably influenced by light availability and the overstory canopy composition. We examined whether forest understory light environment could be predicted by overstory composition in an old growth northern hardwood forest at Huntington Wildlife Forest in the central Adirondacks, NY. We also tested whether the overstory composition and light environment could be used to predict the understory tree composition. Existing continuous forest inventory data were used to quantify the overstory and we collected additional data on tree seedlings and saplings. We characterized the light environment using hemispherical canopy photography. Percent canopy openness was positively correlated with the proportion of American beech (Fagus grandifolia) in the overstory. Understory tree species richness was not predicted by light environment or by the overstory. Yet seedling and sapling density of certain tree species could be predicted by certain overstory characteristics. Density of understory beech was positively correlated with the proportion of overstory beech basal area; however, the densities of other tree species in the understory were not as well correlated with the proportion of overstory conspecifics. Understanding these relationships may help shed light on factors influencing regeneration dynamics in this Adirondack old growth forest. Additionally, since forests in the region have been impacted by beech bark disease the results of this study help elucidate the overstory-understory dynamics in the presence of this disturbance

The Impacts of Increased Precipitation Intensity on Dryland Ecosystems in the Western United States

As the atmosphere warms, precipitation events become larger, but less frequent. Such increases in precipitation intensity are expected regardless of changes in total annual precipitation. Despite strong evidence for increases in precipitation intensity, disagreement exists regarding how these changes will impact plants, and studies are lacking in many types of ecosystems. This dissertation addresses how increased precipitation intensity affects soil water availability, and how plants respond to any such changes. I address this question in the context of big sagebrush ecosystems and dryland winter wheat agriculture, which are both environments that can be sensitive to changes in water availability. Results from two field experiments (Chapters 2 & 3) and modelling (Chapter 4) indicate that fewer larger precipitation events cause water to be ‘pushed’ deeper into the ground. In sagebrush ecosystems this benefitted shrubs, because they tend to have deeper roots and could preferentially access the deeper soil water. The model simulations indicate that these positive effects on shrub growth should be expected in dry climates, but not in wetter climates where larger precipitation events caused more water to be lost to deep drainage. By comparison, increased precipitation intensity had little effect on more shallowly rooted herbaceous plants in sagebrush ecosystems. Similarly, production of winter wheat was not affected by increased precipitation intensity, potentially because this crop matures early in the growing season, while changes in soil moisture were most apparent only later in the summer. My research shows that responses to increased precipitation intensity are likely to differ between plant types and that larger precipitation events may contribute to patterns of increasing dominance of woody plants that can be observed globally. More broadly, these results stress the importance of accounting for climatic variability when forecasting ecological responses to climate change

Winter Wheat Resistant to Increases in Rain and Snow Intensity in a Semi-Arid System

As the atmosphere warms, precipitation events have been predicted and observed to become fewer and larger. Changes in precipitation patterns can have large effects on dryland agricultural production, but experimental tests on the effects of changing precipitation intensity are limited. Over 3 years, we tested the effects of increased precipitation intensity on winter wheat (Triticum aestivum L.; Promontory variety) in a temperate dryland agricultural system that was on a rotation of crop and fallow years. We used 11 (2.1 × 2.5 m) shelters to collect and redeposit rain and snow as larger, more intense events. Total precipitation was the same in all plots, but event sizes in each plot varied from 1 to 18 mm. Treatments increased soil water availability, but winter wheat biomass and grain yield did not differ among treatments. Similarly, other measured plant growth responses, including vegetation greenness, leaf area index, canopy temperature, photochemical efficiency, root area, and new root growth, did not differ among treatments. Results indicate that at least in the semiarid climate and silt loam soils studied here, anticipated increases in precipitation intensity are unlikely to affect winter wheat production negatively. Further, increased precipitation intensity may mitigate water stress caused by increasing temperatures and encourage the use of wheat varieties that utilize deeper, later season soil water

Application of electron microscopy and X-ray diffraction to graphite oxide and its decomposition products

Graphite oxides which had been prepared from three different size graphite particles by the modified Brodie method were observed with the electron microscope. The thermal decomposition products of the oxides, obtained by heating them at 240° and 300°, were observed using the electron microscope and x-ray diffraction. Graphite oxide was seen (using the electron microscope) to consist of flexible, irregularly shaped sheets. The decomposition products were observed as irregularly shaped sheets, somewhat folded, torn or split, and at higher temperatures as amorphous carbon. X-ray diffraction patterns of the decomposition products allow the qualitative evaluation of the change in the composition of the various samples. The level of oxidation obtained is due to the original graphite particle size and to the number of oxidation steps to which a sample is subjected. At the higher temperature the decomposition products consist of unoxidized graphite and amorphous carbon

Evidence for Non-additive Influence of Single Nucleotide Polymorphisms within the Apolipoprotein E Gene

We analyzed 13 single nucleotide polymorphisms (SNPs) within the apolipoprotein E ( APOE ) gene, to identify pairs of SNPs that interact in a non-additive manner to influence genotypic mean levels of the ApoE protein in blood. An overparameterized general linear model of two-SNP genotype means was applied to data from 456 female and 398 male unrelated European Americans from Rochester, MN, USA. We found statistically significant evidence for non-additivity between SNPs within the male sample, but not within the female sample. We observed nine pairs of SNPs with evidence of non-additivity at the Α= 0.05 level of statistical significance within the male sample, when approximately three were expected by chance. Five of the nine pairs involved three SNPs (560, 624 and 1163) that did not have a statistically significant influence when considered separately in a single-site analysis. Three of the nine pairs involving four SNPs (832, 1998, 3937 and 4951) showed significant evidence for non-additivity in at least one of two other male samples from Jackson, MS, USA and North Karelia, Finland. Although all four of these SNPs had a statistically significant influence in Rochester when considered separately, only SNP 3937 gave a significant result in the other male samples. The four SNPs are located in the promoter, intronic and exonic regions, and 3' to the polyadenylation signal in the APOE gene. Our study suggests that analyses that only consider SNPs located in exons and ignore contexts such as those indexed by gender and population, and disregard non-additivity of SNP effects, may inappropriately model the contribution of a gene to the genetic architecture of a trait that has a complex multifactorial etiology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65641/1/j.1529-8817.2003.00112.x.pd

Internal Transcribed Spacer 2 (nu ITS2 rRNA) Sequence-Structure Phylogenetics: Towards an Automated Reconstruction of the Green Algal Tree of Life

L). Some have advocated the use of the nuclear-encoded, internal transcribed spacer two (ITS2) as an alternative to the traditional chloroplast markers. However, the ITS2 is broadly perceived to be insufficiently conserved or to be confounded by introgression or biparental inheritance patterns, precluding its broad use in phylogenetic reconstruction or as a DNA barcode. A growing body of evidence has shown that simultaneous analysis of nucleotide data with secondary structure information can overcome at least some of the limitations of ITS2. The goal of this investigation was to assess the feasibility of an automated, sequence-structure approach for analysis of IT2 data from a large sampling of phylum Chlorophyta.Sequences and secondary structures from 591 chlorophycean, 741 trebouxiophycean and 938 ulvophycean algae, all obtained from the ITS2 Database, were aligned using a sequence structure-specific scoring matrix. Phylogenetic relationships were reconstructed by Profile Neighbor-Joining coupled with a sequence structure-specific, general time reversible substitution model. Results from analyses of the ITS2 data were robust at multiple nodes and showed considerable congruence with results from published phylogenetic analyses.Our observations on the power of automated, sequence-structure analyses of ITS2 to reconstruct phylum-level phylogenies of the green algae validate this approach to assessing diversity for large sets of chlorophytan taxa. Moreover, our results indicate that objections to the use of ITS2 for DNA barcoding should be weighed against the utility of an automated, data analysis approach with demonstrated power to reconstruct evolutionary patterns for highly divergent lineages

Extreme drought impacts have been underestimated in grasslands and shrublands globally

Climate change is increasing the frequency and severity of short-term (~1 y) drought events-the most common duration of drought-globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function-aboveground net primary production (ANPP)-was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought

Living thinking for a culture of transformation

This dissertation describes a dominant abstract modern frame of mind—termed object-thinking—as a root cause of unsustainability. I argue that for long-term sustainability we need a different kind of thinking, called living thinking, that is modeled after the dynamism, interconnectedness, and wholeness that informs the life of organisms and ecological processes in nature. The methodology of Goethean phenomenology is discussed and applied as a means to learn living thinking. I present and describe the adult education course work at The Nature Institute as a model for nature-based, participatory, and transformational learning in sustainability education. A central concern is to show how the phenomenological study of plants can serve as an exemplary way to develop context-sensitive, relational, and holistic ways of conceiving and interacting with the world. The analysis of a course participant survey shows how the personal and professional lives of participants have been affected in a variety of ways, and often deeply, by their learning experiences at The Nature Institute