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1. Leaf nitrogen affects photosynthesis and water use efficiency similarly in nitrogen‐fixing and non‐fixing trees

   https://doi.org/10.1111/1365-2745.14194  

   Bytnerowicz, Thomas A. ; Funk, Jennifer L. ; Menge, Duncan N. L. ; Perakis, Steven S. ; Wolf, Amelia A. ( September 2023 , Journal of Ecology)

   Nitrogen (N)‐fixing trees are thought to break a basic rule of leaf economics: higher leaf N concentrations do not translate into higher rates of carbon assimilation. Understanding how leaf N affects photosynthesis and water use efficiency (WUE) in this ecologically important group is critical.

   We grew six N‐fixing and four non‐fixing tree species for 4–5 years at four fertilization treatments in field experiments in temperate and tropical regions to assess how functional type (N fixer vs. non‐fixer) and N limitation affected leaf N and how leaf N affected light‐saturated photosynthesis (A_sat), stomatal conductance (g_sw) and WUE (WUE_iand δ¹³C).

   A_sat, WUE_iand δ¹³C, but notg_sw, increased with higher leaf N. Surprisingly, N‐fixing and non‐fixing trees displayed similar scaling between leaf N and these physiological variables, and this finding was supported by reanalysis of a global dataset. N fixers generally had higher leaf N than non‐fixers, even when non‐fixers were not N‐limited at the leaf level. Leaf‐level N limitation did not alter the relationship ofA_sat,g_sw, WUE_iand δ¹³C with leaf N, although it did affect the photosynthetic N use efficiency. Higher WUE was associated with higher productivity, whereas higherA_satwas not.

   Synthesis: The ecological success of N‐fixing trees depends on the effect of leaf N on carbon gain and water loss. Using a field fertilization experiment and reanalysis of a global dataset, we show that high leaf‐level photosynthesis and WUE in N fixers stems from their higher average leaf N, rather than a difference between N fixers and non‐fixers in the scaling of photosynthesis and WUE with leaf N. By clarifying the mechanism by which N fixers achieve and benefit from high WUE, our results further the understanding of global N fixer distributions.

    

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2. Ranked Document Retrieval in External Memory

   https://doi.org/10.1145/3559763  

   Shah, Rahul ; Sheng, Cheng ; Thankachan, Sharma ; Vitter, Jeffrey ( January 2023 , ACM Transactions on Algorithms)

   The ranked (or top-k) document retrieval problem is defined as follows: preprocess a collection{T₁,T₂,… ,T_d}ofdstrings (called documents) of total lengthninto a data structure, such that for any given query(P,k), wherePis a string (called pattern) of lengthp ≥ 1andk ∈ [1,d]is an integer, the identifiers of thosekdocuments that are most relevant toPcan be reported, ideally in the sorted order of their relevance. The seminal work by Hon et al. [FOCS 2009 and Journal of the ACM 2014] presented anO(n)-space (in words) data structure withO(p+klogk)query time. The query time was later improved toO(p+k)[SODA 2012] and further toO(p/log_σn+k)[SIAM Journal on Computing 2017] by Navarro and Nekrich, whereσis the alphabet size. We revisit this problem in the external memory model and present three data structures. The first one takesO(n)-space and answer queries inO(p/B+ log_Bn + k/B+log^*(n/B)) I/Os, whereBis the block size. The second one takesO(nlog^*(n/B)) space and answer queries in optimalO(p/B+ log_Bn + k/B)I/Os. In both cases, the answers are reported in the unsorted order of relevance. To handle sorted top-kdocument retrieval, we present anO(nlog(d/B))space data structure with optimal query cost.

    

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3. Responses of stomatal features and photosynthesis to porewater N enrichment and elevated atmospheric CO 2 in Phragmites australis , the common reed

   https://doi.org/10.1002/ajb2.1638  

   Garrison, Julian R. ; Caplan, Joshua S. ; Douhovnikoff, Vladimir ; Mozdzer, Thomas J. ; Logan, Barry A. ( April 2021 , American Journal of Botany)

   Biological invasions increasingly threaten native biodiversity and ecosystem services. One notable example is the common reed,Phragmites australis, which aggressively invades North American salt marshes. Elevated atmospheric CO₂and nitrogen pollution enhance its growth and facilitate invasion becauseP. australisresponds more strongly to these enrichments than do native species. We investigated how modifications to stomatal features contribute to strong photosynthetic responses to CO₂and nitrogen enrichment inP. australisby evaluating stomatal shifts under experimental conditions and relating them to maximal stomatal conductance (g_wmax) and photosynthetic rates.

   Plants were grownin situin open‐top chambers under ambient and elevated atmospheric CO₂(eCO₂) and porewater nitrogen (N_enr) in a Chesapeake Bay tidal marsh. We measured light‐saturated carbon assimilation rates (A_sat) and stomatal characteristics, from which we calculatedg_wmaxand determined whether CO₂and N_enraltered the relationship betweeng_wmaxandA_sat.

   eCO₂and N_enrenhanced bothg_wmaxandA_sat, but to differing degrees;g_wmaxwas more strongly influenced by N_enrthrough increases in stomatal density whileA_satwas more strongly stimulated by eCO₂. There was a positive relationship betweeng_wmaxandA_satthat was not modified by eCO₂or N_enr, individually or in combination.

   Changes in stomatal features co‐occur with previously described responses ofP. australisto eCO₂and N_enr. Complementary responses of stomatal length and density to these global change factors may facilitate greater stomatal conductance and carbon gain, contributing to the invasiveness of the introduced lineage.

    

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4. Temporal trends in molecular markers of drug resistance in Plasmodium falciparum in human blood and profiles of corresponding resistant markers in mosquito oocysts in Asembo, western Kenya

   https://doi.org/10.1186/s12936-022-04284-6  

   Zhou, Zhiyong ; Gimnig, John E. ; Sergent, Sheila B. ; Liu, Ying ; Abong’o, Bernard ; Otieno, Kephas ; Chebore, Winnie ; Shah, Monica P. ; Williamson, John ; ter Kuile, Feiko O. ; et al ( September 2022 , Malaria Journal)

   Over the last two decades, the scale-up of vector control and changes in the first-line anti-malarial, from chloroquine (CQ) to sulfadoxine-pyrimethamine (SP) and then to artemether-lumefantrine (AL), have resulted in significant decreases in malaria burden in western Kenya. This study evaluated the long-term effects of control interventions on molecular markers ofPlasmodium falciparumdrug resistance using parasites obtained from humans and mosquitoes at discrete time points.

   Dried blood spot samples collected in 2012 and 2017 community surveys in Asembo, Kenya were genotyped by Sanger sequencing for markers associated with resistance to SP (Pfdhfr, Pfdhps), CQ, AQ, lumefantrine (Pfcrt, Pfmdr1)and artemisinin (Pfk13).Temporal trends in the prevalence of these markers, including data from 2012 to 2017 as well as published data from 1996, 2001, 2007 from same area, were analysed. The same markers from mosquito oocysts collected in 2012 were compared with results from human blood samples.

   The prevalence of SPdhfr/dhpsquintuple mutant haplotype C₅₀I₅₁R₅₉N₁₀₈I₁₆₄/S₄₃₆G₄₃₇E₅₄₀A₅₈₁A₆₁₃increased from 19.7% in 1996 to 86.0% in 2012, while an increase in the sextuple mutant haplotype C₅₀I₅₁R₅₉N₁₀₈I₁₆₄/H₄₃₆G₄₃₇E₅₄₀A₅₈₁A₆₁₃containingPfdhps-436H was found from 10.5% in 2012 to 34.6% in 2017. ResistantPfcrt-76 T declined from 94.6% in 2007 to 18.3% in 2012 and 0.9% in 2017. MutantPfmdr1-86Y decreased across years from 74.8% in 1996 to zero in 2017, mutantPfmdr1-184F and wildPfmdr1-D1246 increased from 17.9% to 58.9% in 2007 to 55.9% and 90.1% in 2017, respectively.Pfmdr1haplotype N₈₆F₁₈₄S₁₀₃₄N₁₀₄₂D₁₂₄₆ increased from 11.0% in 2007 to 49.6% in 2017. No resistant mutations inPfk13were found. Prevalence ofPfdhps-436H was lower while prevalence ofPfcrt-76 T was higher in mosquitoes than in human blood samples.

   This study showed an increased prevalence ofdhfr/dhpsresistant markers over 20 years with the emergenceof Pfdhps-436H mutant a decade ago in Asembo. The reversal ofPfcrtfrom CQ-resistant to CQ-sensitive genotype occurred following 19 years of CQ withdrawal. NoPfk13markers associated with artemisinin resistance were detected, but the increased haplotype ofPfmdr1N₈₆F₁₈₄S₁₀₃₄N₁₀₄₂D₁₂₄₆was observed. The differences in prevalence ofPfdhps-436H andPfcrt-76 T SNPs between two hosts and the role of mosquitoes in the transmission of drug resistant parasites require further investigation.

    

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5. Thermal property values of a central Iowa soil as functions of soil water content and bulk density or of soil air content

   https://doi.org/10.1111/ejss.12856  

   Tong, Bing ; Kool, Dilia ; Heitman, Joshua L. ; Sauer, Thomas J. ; Gao, Zhiqiu ; Horton, Robert ( July 2019 , European Journal of Soil Science)

   Soil thermal properties play important roles in dynamic heat and mass transfer processes, and they vary with soil water content (θ) and bulk density (ρ_b). Bothθandρ_bchange with time, particularly in recently tilled soil. However, few studies have addressed the full extent of soil thermal property changes withθandρ_b. The objective of this study is to examine how changes inρ_bwith time after tillage impact soil thermal properties (volumetric heat capacity,C_v, thermal diffusivity,k, and thermal conductivity,λ). The study provides thermal property values as functions ofθandρ_band of air content (n_air) on undisturbed soil cores obtained at selected times following tillage. Heat pulse probe measurements of thermal properties were obtained on each soil core at saturated, partially saturated (θat pressure head of −50 kPa) and oven‐dry conditions. Generally,kandλincreased with increasingρ_bat the three water conditions. TheC_vincreased asρ_bincreased in the oven‐dry and unsaturated conditions and decreased asρ_bincreased in the saturated condition. For a givenθ, a largerρ_bwas associated with larger thermal property values, especially forλ. The figures ofC_v,kandλversusθandρ_b, as well asC_v,kandλversusn_air, represented the range of soil conditions following tillage. Trends in the relationships of thermal property values withθandρ_bwere described by 3‐D surfaces, whereas each thermal property had a linear relationship withn_air. Clearly, recently tilled soil thermal property values were quite dynamic temporally due to varyingθandρ_b. The dynamic soil thermal property values should be considered in soil heat and mass transfer models either as 3‐D functions ofθandρ_bor as linear functions ofn_air.

   Thermal property values for a range ofθandρ_bwere measured on undisturbed soil cores.

   Freshly tilled soil thermal property values were quite dynamic temporally.

   The thermal property values of a tilled soil were described as 3‐D surfaces withθandρ_b.

   The thermal property values of a tilled soil varied linearly withn_air.

    

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