Climate Influences the Content and Chemical Composition of Foliar Tannins in Green and Senesced Tissues of \u3ci\u3eQuercus rubra\u3c/i\u3e

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 Quercus rubra exposed to different temperature (Warming and No Warming) and precipitation treatments (Dry, Ambient, Wet) 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 Q. rubra was dominated by condensed tannins (CTs, proanthocyanidins). When exposed to Dry and Ambient*Warm conditions, Q. rubra produced higher quantities of tannins that were less polymerized. In contrast, under favorable conditions (Wet), 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 Wet 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 Wet treatments that produced more polymerized tannins. The content of total tannins in senesced leaves was higher in Warming treatments under both dry and ambient 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

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance.

Investment in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing in Africa over the past year has led to a major increase in the number of sequences that have been generated and used to track the pandemic on the continent, a number that now exceeds 100,000 genomes. Our results show an increase in the number of African countries that are able to sequence domestically and highlight that local sequencing enables faster turnaround times and more-regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and illuminate the distinct dispersal dynamics of variants of concern-particularly Alpha, Beta, Delta, and Omicron-on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve while the continent faces many emerging and reemerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The potential interactive effects of elevated carbon dioxide and ozone and invasive earthworm activity in forest systems

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

Degree of woody encroachment into grasslands controls soil carbohydrate and amino compound changes during long term laboratory incubation

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

Climate Influences the Content and Chemical Composition of Foliar Tannins in Green and Senesced Tissues of Quercus rubra

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 Quercus rubra exposed to different temperature (Warming and No Warming) and precipitation treatments (Dry, Ambient, Wet) 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 Q. rubra was dominated by condensed tannins (CTs, proanthocyanidins). When exposed to Dry and Ambient*Warm conditions, Q. rubra produced higher quantities of tannins that were less polymerized. In contrast, under favorable conditions (Wet), 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 Wet 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 Wet treatments that produced more polymerized tannins. The content of total tannins in senesced leaves was higher in Warming treatments under both dry and ambient 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