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Interactions between leaf phenological type and functional traits drive variation in isoprene emissions in central Amazon forest trees
The Amazon forest is the largest source of isoprene emissions, and the seasonal pattern of leaf-out phenology in this forest has been indicated as an important driver of seasonal variation in emissions. Still, it is unclear how emissions vary between different leaf phenological types in this forest. To evaluate the influence of leaf phenological type over isoprene emissions, we measured leaf-level isoprene emission capacity and leaf functional traits for 175 trees from 124 species of angiosperms distributed among brevideciduous and evergreen trees in a central Amazon forest. Evergreen isoprene emitters were less likely to store monoterpenes and had tougher and less photosynthetically active leaves with higher carbon-to-nitrogen ratios compared to non-emitters. Isoprene emission rates in brevideciduous trees were higher with a higher diversity of stored sesquiterpenes and total phenolics content. Our results suggest that the way isoprene emissions relate to growth and defense traits in central Amazon trees might be influenced by leaf phenological type, and that isoprene may participate in co-regulating a chemical-mechanical defense trade-off between brevideciduous and evergreen trees. Such knowledge can be used to improve emission estimates based on leaf phenological type since, as a highly-emitted biogenic volatile organic compound (BVOC), isoprene affects atmospheric processes with implications for the Earth’s radiative balance.
Journal Article
Leaf isoprene and monoterpene emissions vary with fast-slow carbon economics strategies in central Amazon woody species
Plant responses to stress, inter-organismal signaling, and atmospheric chemistry are significantly influenced by leaf volatile isoprenoid (VI) emissions (e.g., isoprene and monoterpenes). Despite their critical roles in ecology and the atmosphere, we have little understanding of whether and how VI emissions vary with axes of plant functional variation. Understanding these relationships is particularly important in tropical forests, which emit more VIs into the atmosphere than any other biome, and where high species diversity necessitates the imputation of plant traits based on functional and evolutionary relationships. Here, we investigated how VI emissions varied with functional trait axes of fast-slow carbon economics strategies (CES) in Central Amazon Forest woody species. We measured leaf-level isoprene and monoterpene emission capacity ( E c ; emission measured under standard conditions of photosynthetically active radiation of 1000 µmol m -2 s -1 and leaf temperature of 30 ˚C), and 12 leaf and four stem functional traits for 91 trees from 31 species of angiosperm distributed across different vegetation types: non-flooded upland, white sand, and ancient non-flooded river terrace forests. Principal component analysis (PCA) of functional traits revealed two partially independent main axes of CES: a first axis of leaf strategies and a second of mixed leaf/stem strategies. The capacity to emit monoterpenes was observed in 27 species, and monoterpene emitters occupied the whole range of fast-slow strategies, but magnitudes of monoterpene E c increased toward faster leaves. The capacity to emit isoprene was observed in 14 species, and isoprene emitters tended to be positioned toward slower leaf/stem strategies, with magnitudes of isoprene E c also increasing toward slower leaves/stems. Our results highlight the importance of understanding leaf-level emissions to accurately estimate VI fluxes and provide a holistic view of emissions within CES on different organ-system levels. This shows a direction for improving current modeling estimates, which have simplified plant functional type representations and are poorly developed for compounds other than isoprene in the tropics. A more mechanistic representation of plant functional types based on forest functional compositions can reduce modeling emission uncertainties and contribute to understanding the roles of VIs within forest-atmosphere interactions, atmospheric chemistry, and the carbon cycle.
Journal Article
Leaf spectroscopy as a tool for predicting the presence of isoprene emissions and terpene storage in central Amazon forest trees
Background
Volatile isoprenoids (VIs), such as isoprene, monoterpenes, and sesquiterpenes, participate in various forest-atmosphere processes ranging from plant cell regulation to atmospheric particle formation. The Amazon Forest is the greatest and most diverse source of VI emissions, but the lack of leaf-level studies and the logistical challenges of measuring in such remote and highly biodiverse sites bring high levels of uncertainty to modeled emission estimates. Studies indicate that leaf spectroscopy is an effective tool for estimating leaf morphological, physiological, and chemical traits, being a promising tool for more easily assessing VI emissions from vegetation. In this study, we tested the ability of leaf reflectance spectroscopy to predict the presence of VI emissions and storage in central Amazon Forest trees. We measured leaf-level isoprene emission capacity (
E
c
; emission measured at standard conditions: light of 1000 µmol m
− 2
s
− 1
photosynthetically active radiation and leaf temperature of 30 ˚C), stored monoterpene and sesquiterpene contents, and hyperspectral visible to short-wave infrared (VSWIR) reflectance from dry and fresh leaves of 175 trees from 124 species of angiosperms.
Results
We found that dry leaf hyperspectral reflectance data, and fresh leaf reflectance measured at selected wavelengths (616, 694, and 1155 nm), predicted the presence of isoprene emissions with accuracies of 0.67 and 0.72, respectively. Meanwhile, fresh leaf hyperspectral reflectance data predicted monoterpene and sesquiterpene storage with accuracies of 0.65 and 0.67, respectively.
Conclusions
Our results indicate the possibility of using spectral readings from botanical collections or field inventories to orient sampling efforts toward potential isoprene-emitting or terpene-storing trees, or to identify key spectral features (most informative selected wavelengths) for potential future incorporation into remote sensing models. The use of spectral tools for detecting potential isoprene-emitting and terpene-storing species can help to improve current VI emission datasets, reduce modeling emission uncertainties, and contribute to a better understanding of the roles of VIs within forest-atmosphere interactions, atmospheric chemistry, and the carbon cycle.
Journal Article
Mirror image molecules expose state of rainforest stress
Monoterpenes are key to plant communication and defence against biotic (e.g., herbivory) and abiotic (e.g., heat, drought) stress. Chiral monoterpenes, like alpha-pinene, exist as mirror image pairs, known as enantiomers. Enantiomers have the same atmospheric reactivity, but are produced and emitted by different enzymes and internal leaf mechanisms. Abiotic stress can alter their relative emissions, suggesting enantiomer ratios could indicate stress severity. Here we present (−)- and (+)-alpha-pinene and methyl salicylate measurements from the Amazon rainforest over time-of-day, season, and the 2023-24 El Niño. Correlations between alpha-pinene enantiomers shifted with stress, aligning with weakening carbon dioxide uptake by vegetation and transition between de novo and storage emissions. Low- and high-stress zones, along with a recovery zone, were defined through alpha-pinene enantiomer correlations, revealing a metric for ecosystem stress. This chiral ratio reveals diel, seasonal, El Niño, and edge effect stresses, offering a method to gauge drought severity due to climate change.
Correlations of positive and negative alpha-pinene adjust according to drought stress on plants, according to an analysis of atmospheric chemistry data from a tall-tower site in the Amazon rainforest.
Journal Article
TURKISH-GERMAN BILINGUALS AND THEIR INTONATION: TRIANGULATING EVIDENCE ABOUT CONTACT-INDUCED LANGUAGE CHANGE
In this article, I focus on the intonation patterns of Turkish-German bilinguals to discuss intonation within the context of language contact and language variation. The intonational variance involves the realization of terminal rises as produced by second- and third-generation Turkish-German bilinguals living in Germany. These speakers produce two phonetically, phonologically, and pragmatically distinct rises, which differ from what is typically reported for German monolinguals. The primary phonetic differences between the two rises include the relative alignment and slope of the rise, with one rise aligning on the final syllable of the word regardless of the stress pattern and showing a significantly steeper slope than the other. Although the source of these two rises is likely the two languages used by the speakers, this is not a case of intonational code-switching. Rather, the two rises, along with other edge phenomena, form an intonational system in which the rises are in contrast with one another as well as with falls and level edge contours and as such play different pragmatic roles relative to one another.*
Journal Article
Vox popular
Our favorite movies and TV shows feature indelible characters who tell us about themselves not just in what they say but in how they say it. The creative decisions behind these voices—such as what accent or dialect to use—offer rich data for sociolinguistic study. Ideal for students of language variation as well as general readers interested in media, Vox Popular is an engaging tour through the major issues of sociolinguistic study as heard in the voices from mass media. • Provides readers with a unified and accessible picture of the interrelationships between language variation and the mass media • Presents detailed original analyses of multiple audiovisual media sources • Includes a broad methods chapter covering quantitative and qualitative methods in a style not available in any other textbook • All theoretical terms are accessibly explained, with engaging examples, making it suitable for non-academics as well as undergraduate students • Incorporates pedagogical textboxes throughout and includes sections dedicated to developing practical skills for the field
eBook
“I Really Wanted to Do It Better This Year”: How Cognitive Coaching Alters Self-Efficacy and Changes Classroom Writing Instruction
This dissertation investigates the impact of prior writing experiences to determine their effects on teachers’ self-efficacy as writers and writing teachers and on classroom practice. Additionally, the study explored whether cognitive coaching altered teachers’ self-efficacy. Using qualitative action research, the study placed personal experience at the forefront of research analysis to determine if cognitive coaching altered efficacious beliefs and classroom practice. The data collection methods were four phenomenological semi-structured interviews, four cognitive coaching cycles, and participants’ reflective journals. The study aimed to answer the following two research questions. First, in what ways do elementary teachers’ writing identities inform their writing instruction (self-perceptions)? Second, how does cognitive coaching enable teachers to understand and adapt their self-efficacy as writing teachers? Ultimately, the study answered both research questions.The findings indicate that cognitive coaching successfully alters self-efficacy beliefs and positively impacts classroom practice. Findings also proved that Bandura’s sources of efficacy do alter self-efficacy beliefs. The study also discounted Bandura’s belief that low efficacy beliefs hinder people from continuing in a task or endeavor. This research contributes to understanding why elementary teachers may or may not teach writing in their classrooms and determines how to positively influence the scope and nature of writing instruction in classrooms. Future implications of the study include using cognitive coaching as a sustainable, ongoing form of professional development. Additionally, the study has implications for altering efficacy and practice for other curricular areas, not just writing.
Dissertation