ECOPHYSIOLOGICAL RESPONSES OF TROPICAL WOODY SPECIES TO AMBIENT AND ELEVATED TEMPERATURES

Tropical forests cycle one third of Earth’s carbon, yet we are still unsure how tropical vegetation will respond to climate warming. Tropical biomes experience a smaller temperature margin compared to other systems, possibly making them less capable of thermal adjustments. In addition, thermal responses of vegetation have been identified as one of the areas of greatest uncertainty for global carbon models. This dissertation works to quantify tropical forest photosynthetic responses to temperature as well as assessing physiological thermal acclimation of four tropical species. In Chapter, 2 we conducted a meta-analysis to investigate global tropical photosynthetic responses to temperature. We presented algorithms that quantify how instantaneous temperature responses vary for different climate regimes within the tropics. We found that mean annual temperature was the single variable that best predicted most temperature response variables. Stepwise regression showed that including light in net photosynthetic models improved predictive power but, overall, we need better representations of tropical responses to different growth types and conditions. We implemented two in situ warming experiments in a Puerto Rican rainforest to assess physiological thermal acclimation. One experiment was implemented in the understory (Chapter 3) and one in the canopy (Chapter 4). Our understory warming experiment found evidence for net photosynthetic acclimation; however, acclimation did not systematically occur across both warming studies. Some species showed evidence of acclimation of the optimum temperature for photosynthesis (Topt) or both Topt and the photosynthetic rate; while, neither of our canopy species photosynthetically acclimated. Contrary to common hypotheses surrounding plant respiration, only one of the four species showed evidence of respiratory acclimation. Our understory vegetation temperature responses were more strongly controlled by soil moisture than temperature itself. Specifically, the photosynthetic rate declined as soils dried, a response that coincided with stomatal conductance. Surprisingly, Topt decreased with increasing height for our canopy species, and this response was likely, in part, due to higher thermal sensitivity of stomatal conductance in the mid and upper canopies. Additionally, our canopy species were found to be operating right at or above their Topt. The results of this dissertation better quantify tropical physiological responses to temperature, as well as assesses the potential of tropical plants to physiologically acclimate

Within-canopy experimental leaf warming induces photosynthetic decline instead of acclimation in two northern hardwood species

Northern hardwood forests are experiencing higher temperatures and more extreme heat waves, potentially altering plant physiological processes. We implemented in-situ leaf-level warming along a vertical gradient within a mature forest canopy to investigate photosynthetic acclimation potential of two northern hardwood species, Acer saccharum and Tilia americana. After 7 days of +3°C warming, photosynthetic acclimation was assessed by measuring differences between heated and control photosynthetic rates (Aopt) at leaf optimum temperatures (Topt). We also measured the effects of warming and height on maximum rates of Rubisco carboxylation, stomatal conductance, transpiration, and leaf traits: leaf area, leaf mass per area, leaf nitrogen, and leaf water content. We found no evidence of photosynthetic acclimation for either species, but rather Aopt declined with warming overall. We found slight shifts in LMA and Narea, leaf traits associated with photosynthetic capacity, after 1 week of experimental warming. T. americana LMA and Narea was lower in the upper canopy heated leaves than in the control leaves, contributing a shift in Narea height distribution in the heated leaves. T. americana showed evidence of greater resiliency to warming, with greater thermoregulation, physiological plasticity, and evapotranspiration. As expected, Aopt of A. saccharum increased with height, but Aopt of T. americana was highest in the sub canopy, possibly due to constraints on leaf water balance and photosynthetic capacity in the upper canopy. Thus, models relying on canopy height or light environment may incorrectly estimate vertical variation of photosynthetic capacity. If these species are not able to acclimate to warmer temperatures, we could see alteration of plant carbon balance of these two key northern hardwood species

Photosynthetic and Respiratory Acclimation of Understory Shrubs in Response to in situ Experimental Warming of a Wet Tropical Forest

Despite the importance of tropical forests to global carbon balance, our understanding of how tropical plant physiology will respond to climate warming is limited. In addition, the contribution of tropical forest understories to global carbon cycling is predicted to increase with rising temperatures, however, in situ warming studies of tropical forest plants to date focus only on upper canopies. We present results of an in situ field-scale +4°C understory infrared warming experiment in Puerto Rico (Tropical Responses to Altered Climate Experiment; TRACE). We investigated gas exchange responses of two common understory shrubs, Psychotria brachiata and Piper glabrescens, after exposure to 4 and 8 months warming. We assessed physiological acclimation in two ways: (1) by comparing plot-level physiological responses in heated versus control treatments before and after warming, and (2) by examining physiological responses of individual plants to variation in environmental drivers across all plots, seasons, and treatments. P. brachiata has the capacity to up-regulate (i.e., acclimate) photosynthesis through broadened thermal niche and up-regulation of photosynthetic temperature optimum (Topt) with warmer temperatures. P. glabrescens, however, did not upregulate any photosynthetic parameter, but rather experienced declines in the rate of photosynthesis at the optimum temperature (Aopt), corresponding with lower stomatal conductance under warmer daily temperatures. Contrary to expectation, neither species showed strong evidence for respiratory acclimation. P. brachiata down-regulated basal respiration with warmer daily temperatures during the drier winter months only. P. glabrescens showed no evidence of respiratory acclimation. Unexpectedly, soil moisture, was the strongest environmental driver of daily physiological temperature responses, not vegetation temperature. Topt increased, while photosynthesis and basal respiration declined as soils dried, suggesting that drier conditions negatively affected carbon uptake for both species. Overall, P. brachiata, an early successional shrub, showed higher acclimation potential to daily temperature variations, potentially mitigating negative effects of chronic warming. The negative photosynthetic response to warming experienced by P. glabrescens, a mid-successional shrub, suggests that this species may not be able to as successfully tolerate future, warmer temperatures. These results highlight the importance of considering species when assessing climate change and relay the importance of soil moisture on plant function in large-scale warming experiments

Predicting effects of climate change on productivity and persistence of forest trees

Global climate change increases uncertainty in sustained functioning of forest ecosystems. Forest canopies are a key link between terrestrial ecosystems, the atmosphere, and climate. Here, we introduce research presented at the 66th meeting of the Ecological Society of Japan in the symposium “Structure and function of forest canopies under climate change.” Old-growth forest carbon stores are the largest and may be the most vulnerable to climate change as the balance between sequestration and emission could easily be tipped. Detailed structural analysis of individual large, old trees shows they are allocating wood to the trunk and crown in patterns that cannot be deduced from ground, thus can be used to more accurately quantify total forest carbon and sequestration. Slowly migrating species sensitive to novel climatic conditions will have to acclimate at the individual level. Accounting for physiological responses of trees to climate change will improve predictions of future species distributions and subsequent functioning of forest ecosystems. Field experiments manipulating temperature and precipitation show how trees compensate physiologically to mitigate for higher temperatures and drought. However, it is difficult to measure acclimation responses over long timeframes. Intraindividual trait variation is proposed as an indicator of acclimation potential of trees to future conditions and suggests that acclimation potential may vary among regional populations within a species. Integrating whole-tree structural data with physiological data offers a promising avenue for understanding how trees will respond to climatic shifts

Cross-cultural adaptation of children’s environmental health questionnaires for nursing students in England

Objectives: Children are among the most vulnerable population groups with regard to environmental risks. Nursing students must be fully educated on children’s environmental health as they are in a key position to prevent and reduce the effects of environmental hazards. The main objective of this study was to adapt and validate an English language version of two questionnaires about children’s health and the environment, to assess the knowledge and skills of student nurses in England. Design: Observational cross-sectional study. Setting: A university in Southern England. Method: The study involves translating, adapting and validating the Children’s Environmental Health Knowledge Questionnaire (ChEHK-Q) and the Children’s Environmental Health Skills Questionnaire (ChEHS-Q) with nursing students in England (N = 232). Results: The psychometric characteristics of both questionnaires were strong. Infit and outfit values were close to 1. The reliability values for the items and people were 0.96 and 0.79 for ChEHK-Q and 0.98 and 0.89 for ChEHS-Q, respectively. Only 52 (22.41%) and 77 (33.62%) participants had at least good knowledge and skills, respectively. Higher knowledge and skills were found with respect to the vulnerability of children and identification of environmental risks in the home. Lower levels of knowledge and skills were found with respect to the effects of pesticides and the assessment of neoplastic pollutants. Conclusion: Findings demonstrate deficiencies in nursing competencies related to children’s environmental health. The use of these questionnaires will facilitate improvement in both knowledge and skills related to children’s environmental health among future nurses

Effectiveness of the e-NurSus Children Intervention in the Training of Nursing Students

The paediatric population is the most vulnerable to exposure to environmental risk factors. Institutions of higher education have to equip nursing students with the attitudes, knowledge, and skills to respond to this using blended learning. The aim of this study was to evaluate the effect of e-NurSus Children intervention on student nurses’ attitudes, knowledge, and skills. A quasi-experimental study of time series was designed using pre and post educational intervention evaluation in 2018. The participants were nursing students (N = 267) from Spain (n = 110) and the United Kingdom (n = 157). Three instruments were used: the Sustainability Attitudes in Nursing Survey, the Children’s Environmental Health Knowledge Questionnaire, and the Children’s Environmental Health Skills Questionnaire. The attitudes (15.81%), knowledge (39.02%), and skills (29.98%) of nursing students improved following the e-NurSus Children intervention. It is necessary to include topics on children’s environmental health in nurse education as students are aware of this issue but do not have the knowledge or skills required to manage problems or illness caused by the environment. The e-NurSus Children intervention is an effective tool to address this educational gap.</jats:p

Does Uptake of Pharmaceuticals Vary Across Earthworm Species?

This study compared the uptake and depuration of four commonly used pharmaceuticals (carbamazepine, diclofenac, fluoxetine and orlistat) in two earthworm species (Lumbricus terrestris and Eisenia fetida). L. terrestris are a larger species and often found in deep burrows whereas E. fetida prefer to reside near the soil surface. Species burrowing habits and sizes may alter uptake by earthworms. All four pharmaceuticals were taken up into both L. terrestris and E. fetida tissue after 21 days exposure to spiked soil. Bioconcentration factors (BCFs) ranged between 1.72 and 29.83 for L. terrestris and 1.14 and 63.03 for E. fetida. For carbamazepine and diclofenac, BCFs were similar whereas for fluoxetine and orlistat, BCFs in E. fetida were more than double those seen in L. terrestris. Results indicate that uptake into earthworms cannot be generalised between species and that the influence of species traits can vary depending on the nature of the study chemical

How much randomness can be extracted from memoryless Shannon entropy sources?

We revisit the classical problem: given a memoryless source having a certain amount of Shannon Entropy, how many random bits can be extracted? This question appears in works studying random number generators built from physical entropy sources. Some authors use a heuristic estimate obtained from the Asymptotic Equipartition Property, which yields roughly $n$ extractable bits, where $n$ is the total Shannon entropy amount. However the best known precise form gives only $n-O(\sqrt{\log(1/\epsilon) n})$, where $\epsilon$ is the distance of the extracted bits from uniform. In this paper we show a matching $n-\Omega(\sqrt{\log(1/\epsilon) n})$ upper bound. Therefore, the loss of $\Theta(\sqrt{\log(1/\epsilon) n})$ bits is necessary. As we show, this theoretical bound is of practical relevance. Namely, applying the imprecise AEP heuristic to a mobile phone accelerometer one might overestimate extractable entropy even by $100\%$, no matter what the extractor is. Thus, the ``AEP extracting heuristic\u27\u27 should not be used without taking the precise error into account

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV