Current carbon cycle-climate models predict that future soil carbon storage will be determined by the balance between CO2 fertilization and warming. However, it is uncertain whether greater carbon ...inputs to soils with elevated CO2 will be sequestered, particularly since warming hastens soil carbon decomposition rates, and may alter the response of soils to new plant inputs. We studied the effects of elevated CO2 and warming on microbial soil carbon decomposition processes using laboratory manipulations of carbon inputs and soil temperature. We incubated soils from the Aspen Free Air CO2 Enrichment experiment, where no accumulation of soil carbon has been observed despite a decade of increased carbon inputs to soils under elevated CO2. We added isotopically-labeled sucrose to these soils in the laboratory to mimic and trace the effects of increased carbon inputs on soil organic carbon decomposition and its temperature sensitivity. Sucrose additions caused a positive priming of soil organic carbon decomposition, demonstrated by increased respiration derived from soil carbon, increased microbial abundance, and a shift in the microbial community towards faster growing microorganisms. Similar patterns were observed for elevated CO2 soils, suggesting that the priming effect was responsible for reductions in soil carbon accumulation at the site. Laboratory warming accelerated the rate of the priming effect, but the magnitude of the priming effect was not different amongst temperatures, suggesting that the priming effect was limited by substrate availability, not soil temperature. No changes in substrate use efficiency were observed with elevated CO2 or warming. The stimulatory effects of warming on the priming effect suggest that increased belowground carbon inputs from CO2 fertilization are not likely to be stored in mineral soils.
Effects of elevated CO2 and warming on the soil carbon cycle. Display omitted
•Increased carbon inputs in laboratory cause a positive priming of SOC decomposition.•Increased carbon inputs to soil from 10 y of eCO2 similarly altered SOC decomposition.•Warming increased the rate, not amount, of SOC primed by increased carbon inputs.•Microbial substrate use efficiency for added sucrose was unchanged by eCO2 or warming.•The priming effect did not change the proportion of different ages of C in respiration.
Environmental stresses not only influence production of plant metabolites but could also modify their resorption during leaf senescence. The production-resorption dynamics of polyphenolic tannins, a ...class of defense compound whose ecological role extends beyond tissue senescence, could amplify the influence of climate on ecosystem processes. We studied the quantity, chemical composition, and tissue-association of tannins in green and freshly-senesced leaves of
exposed to different temperature (
and
) and precipitation treatments (
) at the Boston-Area Climate Experiment (BACE) in Massachusetts, USA. Climate influenced not only the quantity of tannins, but also their molecular composition and cell-wall associations. Irrespective of climatic treatments, tannin composition in
was dominated by condensed tannins (CTs, proanthocyanidins). When exposed to
and
conditions,
produced higher quantities of tannins that were less polymerized. In contrast, under favorable conditions (
), tannins were produced in lower quantities, but the CTs were more polymerized. Further, even as the overall tissue tannin content declined, the content of hydrolysable tannins (HTs) increased under
treatments. The molecular composition of tannins influenced their content in senesced litter. Compared to the green leaves, the content of HTs decreased in senesced leaves across treatments, whereas the CT content was similar between green and senesced leaves in
treatments that produced more polymerized tannins. The content of total tannins in senesced leaves was higher in
treatments under both
and
precipitation treatments. Our results suggest that, though climate directly influenced the production of tannins in green tissues (and similar patterns were observed in the senesced tissue), the influence of climate on tannin content of senesced tissue was partly mediated by the effect on the chemical composition of tannins. These different climatic impacts on leaves over the course of a growing season may alter forest dynamics, not only in decomposition and nutrient cycling dynamics, but also in herbivory dynamics.
Elevated atmospheric CO₂ concentrations can change chemistry and input rate of plant tissue to soil, potentially influencing above‐ and below‐ground biogeochemical cycles. Given the important role ...played by leaf and root litter chemistry in controlling ecosystem function and vulnerability to environmental stresses, we investigated the hydrolyzable amino acid distribution and concentration in leaf and fine root litter among control and elevated CO₂ treatments at the Rhinelander free air CO₂ enrichment (FACE) experiment (WI, USA). We extracted hydrolyzable amino acids from leaf litter and fine (< 2 mm) roots at three depths for both control and elevated CO₂ plots. We found that elevated CO₂ decreased the proportion of total leaf amino acid carbon (C), but had no effect on total leaf amino acid nitrogen (N). There was no treatment effect for total root amino acid N or amino acid C for any depth. The decrease in leaf amino acids is probably a result of the shift of protein compounds to more structural compounds. Despite the decrease in leaf amino acid C concentrations, the overall increase in annual plant production under elevated CO₂ would result in an increase in plant amino acids to the soil.
Although many environmental and science educators have explored students' conceptual understandings, misconceptions, and knowledge of the greenhouse effect, global warming, and climate change, few ...have investigated the ways students conceptualize climate as a system or how components of the system influence climate. Therefore, the purpose of this study was to begin the process of understanding how US students conceptualize a climate system. A total of 42 seventh grade students (ages 12-13) from the Midwest completed an open-response task. From the inductive analysis of student written responses, 22 codes emerged that reflected students' conceptions of the climate system. From these codes, three path diagrams were constructed that illustrate these students' conceptions about how a climate system influences climate and how greenhouse gases and global warming impact the climate system. A generalized model of students' conception of a climate system was generated. Students in this study conceptualized a climate system in a unidirectional, linear, cause and effect relationship that emphasized the atmospheric component of the climate system.
► We incubated soil samples from a chronosequence of woody plant encroachment for 1year. ► Carbohydrate C was lost slightly faster than bulk C. ► Increases in amino C correlated with thermal data. ► ...Microbial recycling of C was important for soil C stability. ► Soil C decomposition was not linked to intrinsic degradability of isolated compounds.
Up to 50% of organic C and 80% of organic N within soil can exist as amino acids, amino sugars and carbohydrates. To determine how potential microbial accessibility and turnover of these compounds is impacted by encroachment of woody plants into grasslands, we investigated changes in evolved CO2 during thermal analysis and in carbohydrate and amino compound chemistry after long term laboratory incubation of sandy loam grassland woodland soils from southern Texas, USA. Thermal analysis showed that incubation increased the amount of soil organic matter (SOM) released at higher temperatures and that evolved CO2 profiles correlated with increases in amino C. During incubation, total carbohydrate C decreased slightly faster than bulk soil C, with preferential loss of plant-derived carbohydrates and/or production of microbial carbohydrates most strongly expressed in grassland and younger woodland soils. Total N content did not change during incubation, so the reduction in extractable amino N in older woodland soils suggested that N became more resistant to extraction during incubation. These data, along with previous measurements of respired CO2, indicate that changes in carbohydrate C and amino C did not predict mineralized CO2 yields and that amino compounds and microbial carbohydrate C were not selectively lost during incubation. The differing response in SOM loss (or enrichment) during incubation of the older woodland soils revealed a system with altered SOM dynamics due to woody encroachment, confirming that the short term ‘lability’ or ‘recalcitrance’ of SOM components is dependent on a number of interacting variables.
Summary
Elevated atmospheric
CO
2
concentrations can change chemistry and input rate of plant tissue to soil, potentially influencing above‐ and below‐ground biogeochemical cycles. Given the ...important role played by leaf and root litter chemistry in controlling ecosystem function and vulnerability to environmental stresses, we investigated the hydrolyzable amino acid distribution and concentration in leaf and fine root litter among control and elevated
CO
2
treatments at the Rhinelander free air
CO
2
enrichment (
FACE
) experiment (
WI
,
USA
).
We extracted hydrolyzable amino acids from leaf litter and fine (< 2 mm) roots at three depths for both control and elevated
CO
2
plots.
We found that elevated
CO
2
decreased the proportion of total leaf amino acid carbon (C), but had no effect on total leaf amino acid nitrogen (N). There was no treatment effect for total root amino acid N or amino acid C for any depth.
The decrease in leaf amino acids is probably a result of the shift of protein compounds to more structural compounds. Despite the decrease in leaf amino acid C concentrations, the overall increase in annual plant production under elevated
CO
2
would result in an increase in plant amino acids to the soil.
Rising atmospheric CO2 and O3 levels have the potential to change both the chemistry and input rate of plant and microbial organic matter to soil, causing fundamental changes in both above and below ...ground biogeochemical cycles. Because forests store vast amounts of C, small shifts in the photosynthetic input and ecosystem respiration can result in large changes to the overall C and N budget in the forest ecosystem. Pairing the effects of elevated CO2 and O3 with the increasing occurrence of invasive earthworm activity in temperate forests, the outcome results in a shift in how the forest functions. In an effort to examine the shift that occurs we examined the effects of elevated levels of CO2 and O3 on plant and soil (0-25 cm) amino acids at the Rhinelander free-air CO2 enrichment forest (FACE) site in northern Wisconsin, USA. We examined soil amino acids, which are mainly derived from plant and microbial input, because they are of particular importance to soil organic matter dynamics and terrestrial productivity because they store between 35-80% of total soil N, and shifts in amino acid content of the plant litter may shift the N cycle in the Rhinelander FACE site. In addition we also examined earthworm populations and the amino acids of their fecal matter in an effort to understand how earthworms can alter the ecosystem and how they are influenced by changes in ecosystems, such as elevated CO 2 or O3 levels. Also, embedded in this objective is the role that invasive earthworms play in the incorporation of the chemically altered plant material into the soil. These objectives were accomplished through the use of molecular and isotopic analysis of the plant, soil, and earthworm samples. Our work showed that the presence of elevated CO2 resulted in a decrease in concentration of amino acids in the leaf litter, but no change in the proportion of specific amino acids compared to ambient CO2. Amino acids found in the root however, did not change. Although the concentration of amino acids in leaf litter was lower in elevated CO2, because of the increased leaf and root biomass, there was a net increase of amino acid-N added to the soil each year. The presence of elevated O3 resulted in an increase in leaf litter amino acid-C, with no change to the root amino acids. The presence of elevated atmospheric gases results in mainly a change to the leaf litter chemistry, but no significant changes to underground plant tissue. Despite changes to the plant litter, no changes were observed in the soil amino acids with either elevated CO2 or O3. In our one time sampling of earthworms, we found that the presence of elevated CO2 resulted in an increased total number of earthworms, while elevated O3 did not affect the population of earthworms. In the amino acid analysis of the fecal matter, we did not find a treatment effect on the fecal matter on the extracted amino acids, despite the fact that the epigeic earthworms consume more leaf litter and the endogeic earthworms consume more soil. We did, however, find that the endogeic earthworm fecal matter contained more amino acids than all other samples measured, making their fecal matter nutrient hotspots when deposited in the soil. Using an isotopic mixing model for multiple potential sources, we were able to determine a percentage range for the potential sources to the earthworm fecal matter. For the epigeic earthworm fecal matter, the largest contribution to the overall isotopic signature is from the leaf litter (50-80%), while the other is coming from soil and root tissue. For the endogeic earthworm fecal matter, the largest contributor is the surface soil and fine root tissue. It also illustrates that earthworms are a key driver of the incorporation and movement of soil and organic matter at this FACE site. Overall, these results reveal that elevated CO2 and O 3 paired with the change in soil invertebrates can have a large impact on the cycling of C and N in a forest ecosystem. Earthworms at this FACE site and others may be an important factor in the movement of C and N.
Countries of the greater Mekong subregion have made a transition from malaria control to an aim for falciparum and vivax malaria elimination. The elimination of falciparum malaria will have to be ...achieved against a background of increasing artemisinin and multi-drug resistance. This ambitious goal requires an operational research (OR) agenda that addresses the dynamic challenges encountered on the path to elimination, which will need to be flexible and developed in close relation with the cambodian national programme for parasitology, entomology and malaria control (CNM). In Cambodia, a number of meetings with stakeholders were convened by the CNM and emergency response to artemisinin resistance (ERAR) hub, producing an initial list of priority OR topics. The process and outcome of these meetings are described, which could serve as a template for other countries in the region.
A landscaping exercise was conducted to gather all past, on-going and planned malaria focussed OR activities conducted by the cambodian research consortium in Cambodia and categorized according to research theme. The six themes included (1) malaria epidemiology, surveillance and response, (2) malaria case management, (3) malaria vector control, (4) malaria behavioural issues, (5) malaria clinical studies, and (6) other vector-borne diseases (dengue, neglected tropical diseases, soil-transmitted helminths). The different themes were discussed in small focus groups, which made an initial prioritization list which was then presented to a plenary group for further discussion. This produced a list of research questions ranked according to priority.
OR priorities produced by the thematic groups were discussed in the plenary meeting and given a priority score by group voting. A list of 17 OR questions were developed, finalized and listed, which included questions on surveillance, active case detection and treatment efficacy.
This paper describes ERAR's work on supporting Cambodia's transition to malaria elimination by identifying national operational research priorities. ERAR has initiated and currently plays a critical role in the development of country specific research agendas for malaria elimination. The first example of this has been the described exercise in Cambodia, which could serve a template for setting OR priorities in the wider region.
This commentary offers insight into how to best address barriers that may hinder the translation of malaria research findings into policy. It also proposes viable methods of implementing these ...policies in Cambodia. Currently, a wide range of malaria research is being conducted by in-country stakeholders, including Cambodia's National Programme for Parasitology, Entomology and Malaria Control's (CNM), non-governmental organizations, and academic institutions. Coordinating research amongst these partners, as well as within the Ministry of Health, is a challenge. Results are rarely disseminated widely and seldom inform programme and policy decisions. CNM and its research partners have severely limited access to each other's databases. This lack of accessibility, timeliness, engagement and cooperation between CNM and its partners greatly impacts overall research efficiency in this field, and is stifling innovation both within and beyond CNM. Cambodia has set a goal to eradicate all forms of malaria by 2030. As countries approach the elimination phase, there is a greater need for sharing research-generated evidence amongst partners, in order to ensure that appropriate and impactful activities are conducted. The Cambodian Research Consortium was established to serve as a framework for partners, stakeholders and researchers to share research projects, information and results, and to promote the goals of CNM. The sharing of malaria research results will help to inform prevention, control and elimination activities in the country. It will also determine and address the country's operational research needs, and could potentially become a framework model to be used in other countries aiming to transition from malaria control to elimination.
Adult T-cell leukemia (ATL) is a malignancy of mature lymphocytes caused by the retrovirus human T-cell lymphotropic virus-1. It is an aggressive leukemia with a median survival time of 9 months; no ...chemotherapy regimen appears successful in inducing long-term disease-free survival. The scientific basis of the present study is that ATL cells express high-affinity interleukin-2 receptors identified by the anti-Tac monoclonal antibody, whereas normal resting cells do not. To exploit this difference, we administered anti-Tac armed with Yttrium-90 (90Y) to 18 patients with ATL initially (first 9 patients) in a phase I dose-escalation trial and subsequently (second group of 9 patients) in a phase II trial involving a uniform 10-mCi dose of 90Y-labeled anti-Tac. Patients undergoing a remission were permitted to receive up to eight additional doses. At the 5- to 15-mCi doses used, 9 of 16 evaluable patients responded to 90Y anti-Tac with a partial (7 patients) or complete (2 patients) remission. The responses observed represent improved efficacy in terms of length of remission when compared with previous results with unmodified anti-Tac. Clinically meaningful (≥grade 3) toxicity was largely limited to the hematopoietic system. In conclusion, radioimmunotherapy with 90Y anti-Tac directed toward the IL-2R expressed on ATL cells may provide a useful approach for treatment of this aggressive malignancy.
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