Scaling from single-point sap velocity measurements to stand transpiration in a multispecies deciduous forest: Uncertainty sources, stand structure effect, and future scenarios

9 páginas.-- 5 figuras.-- 2 tablas.-- 58 referencias[EN] A major challenge in studies estimating stand water use in mixed-species forests is how to effectively scale data from individual trees to the stand. This is the case for forest ecosystems in the northeastern USA where differences in water use among species and across different size classes have not been extensively studied, despite their relevance for a wide range of ecosystem services. Our objectives were to assess the importance of different sources of variability on transpiration upscaling and explore the potential impacts of future shifts in species composition on the forest water budget. We measured sap velocity in five tree species (Fagus grandifolia Ehrh., Acer rubrum L., Acer saccharum Marsh., Betula alleghaniensis Britton, and Betula papyrifera Marsh.) in a mature stand and a young stand in New Hampshire, USA. Our results showed that the greatest potential source of error was radial variability and that tree size was more important than species in determining sap velocity. Total sapwood area was demonstrated to exert a strong controlling influence on transpiration, varying depending on tree size and species. We conclude that the effect of potential species shifts on transpiration will depend on the sap velocity, determined not only by radial variation and tree size, but also by the sapwood area distribution in the stand.[FR] Les études dont le but est d'estimer l'utilisation de l'eau a` l'échelle du peuplement dans les forêts mélangées font face a` un défi majeur : comment passer efficacement de l'échelle des arbres individuels a` l'échelle du peuplement. C'est le cas pour les écosystèmes forestiers dans le nord-est des États-Unis où les différences dans l'utilisation de l'eau entre les espèces et parmi les différentes catégories de taille n'ont pas fait l'objet d'études approfondies malgré leur pertinence pour une vaste gamme de services de l'écosystème. Nos objectifs consistaient a` évaluer l'importance des différentes sources de variation sur l'extrapolation de la transpiration et a` explorer les impacts potentiels des changements futurs dans la composition en espèces sur le bilan hydrique de la forêt. Nous avons mesuré la vitesse de la sève chez cinq espèces d'arbre (Fagus grandifolia Ehrh., Acer rubrum L., Acer saccharum Marsh., Betula alleghaniensis Britton et Betula papyrifera Marsh.) dans un peuplement mature et dans un jeune peuplement au New Hampshire (É.-U.). Nos résultats ont montré que la plus grande source potentielle d'erreur était la variation radiale et que la vitesse de la sève était davantage déterminée par la taille des arbres que par l'espèce. La surface totale de bois d'aubier avait un effet très déterminant sur la transpiration qui variait selon la taille et l'espèce d'arbre. Nous concluons que l'effet des changements potentiels dans la composition en espèces sur la transpiration dépendra de la vitesse de la sève qui est principalement déterminée par la variation radiale et la taille des arbres mais aussi de la distribution de la surface de bois d'aubier dans le peuplement.This work was funded by the University of New Hampshire and the New Hampshire Agricultural Experiment Station. The Bartlett Experimental Forest is operated by the USDA Forest Service Northern Research Station. S. Mcgraw, P. Pellissier, C. Breton, S. Alvarado-Barrientos, R. Snyder, and Z. Aldag assisted in the field and in the lab. The 2011 stand inventory was led by S. Goswami. Tree heights were measured and compiled by C. Blodgett, T. Fahey, and L. Liu. A. Richardson shared meteorology and solar radiation data from the Bartlett Amerflux tower. The stands used in this experiment are maintained and monitored by the MELNHE project under the direction of R. Yanai and M. Fisk, with funding from NSF grants DEB 0235650 and DEB 0949324Peer reviewe

KEGG annotation of differentially expressed genes.

<p>KEGG annotation showed that many unigenes are assigned to the ribosome signaling pathway and immune-related pathways.</p

Protection-Free Ag Nanowires as a Transparent Conductive Electrode for Improved Cu(In_1–<i>x</i>, Ga_<i>x</i>)Se₂ (CIGS)-Based Photovoltaic Performances

A rather low efficiency for Cu­(In_1–<i>x</i>, Ga_<i>x</i>)­Se₂ (CIGS)-based solar cells (mostly less than 1%) is generally reported, where silver nanowires (Ag NWs) are employed as a top transparent conductive electrode (TCE). The weak adhesion and small contact area between the Ag NWs and the n-type buffer layer remain an acknowledged issue to be addressed. Here, a modified polyol reduction process was elaborately proposed, on the basis of the regulation of the PVP molecule’s steric effect and cationic chemical characteristics. Ag NWs with controllable lengths and diameters were successfully synthesized, to meet the optimization of the photovoltaic performance. The mixed PVP consisting of short and long chains works very effectively, in increasing the length and shortening the diameter. We attribute this to the large steric hindrance-induced protective shielding on {100} planes by insertion of the short chains into the long ones. Cationic chemical characteristics, on the effect of Ag morphological evolution, were also referred and carefully conducted. Importantly, a champion efficiency of 4.97% on pristine Ag NWs without protection and post-treatment as a TCE was achieved, and this was attributed to the enhanced adhesion and increased contact area between Ag NWs and the top of buffer layer

Gene expression analysis of porcine whole blood cells infected with foot-and-mouth disease virus using high-throughput sequencing technology

<div><p>Foot-and-mouth disease virus (FMDV) is a single-stranded positive RNA virus that belongs to the family <i>Picornaviridae</i>. FMDV infects cloven-hoofed animals, such as pigs, sheep, goats, cattle and diverse wildlife species, and remains a major threat to the livestock industry worldwide. In this study, a transcriptome analysis of whole blood from pigs infected with FMDV was performed using the paired-end Illumina sequencing technique to understand the interactions between the pathogen and its host cells. During infection with FMDV, a total of 120 differentially expressed genes (DEGs) were identified, including 110 up-regulated genes and 10 down-regulated genes. To further investigate the DEGs involved in interactions between the virus and its host, gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were conducted. GO annotation indicated that a number of DEGs were enriched in categories involved in host-virus interactions, such as response to stimulus, immune system process and regulation of biological process. KEGG enrichment analysis indicated that the DEGs were primarily involved in the ribosome signaling pathway and immune-related signaling pathways. Ten DEGs, including the immune-related genes <i>BTK1</i>, <i>C1QB</i>, <i>TIMD4</i> and <i>CXCL10</i>, were selected and validated using quantitative PCR, which showed that the expression patterns of these genes are consistent with the results of the <i>in silico</i> expression analysis. In conclusion, this study presents the first transcriptome analysis of pig whole blood cells infected with FMDV, and the results obtained in this study improve our understanding of the interactions between FMDV and host cells as well as the diagnosis and control of FMD.</p></div

Details of primers used for qPCR assay.

<p>Details of primers used for qPCR assay.</p

Comparison of gene expression levels between the I and NI groups.

<p>Yellow triangles represent up-regulated genes, blue rhombuses indicate down-regulated genes, and brown dots represent genes that did not change significantly. The parameters “Probability> = 0.8” and “abs(log2(Y/X)> = 1)” were used as thresholds to determine the significance of gene expression differences.</p

Investigation of the Interaction between Perovskite Films with Moisture via in Situ Electrical Resistance Measurement

Organometal halide perovskites have recently emerged as outstanding semiconductors for solid-state optoelectronic devices. Their sensitivity to moisture is one of the biggest barriers to commercialization. In order to identify the effect of moisture in the degradation process, here we combined the in situ electrical resistance measurement with time-resolved X-ray diffraction analysis to investigate the interaction of CH₃NH₃PbI_3−<i>x</i>Cl_<i>x</i> perovskite films with moisture. Upon short-time exposure, the resistance of the perovskite films decreased and it could be fully recovered, which were ascribed to a mere chemisorption of water molecules, followed by the reversible hydration into CH₃NH₃PbI_3–<i>x</i>Cl_<i>x</i>·H₂O. Upon long-time exposure, however, the resistance became irreversible due to the decomposition into PbI₂. The results demonstrated the formation of monohydrated intermediate phase when the perovskites interacted with moisture. The role of moisture in accelerating the thermal degradation at 85 °C was also demonstrated. Furthermore, our study suggested that the perovskite films with fewer defects may be more inherently resistant to moisture

Thermal Evaporation and Characterization of Sb₂Se₃ Thin Film for Substrate Sb₂Se₃/CdS Solar Cells

Sb₂Se₃ is a promising absorber material for photovoltaic cells because of its optimum band gap, strong optical absorption, simple phase and composition, and earth-abundant and nontoxic constituents. However, this material is rarely explored for photovoltaic application. Here we report Sb₂Se₃ solar cells fabricated from thermal evaporation. The rationale to choose thermal evaporation for Sb₂Se₃ film deposition was first discussed, followed by detailed characterization of Sb₂Se₃ film deposited onto FTO with different substrate temperatures. We then studied the optical absorption, photosensitivity, and band position of Sb₂Se₃ film, and finally a prototype photovoltaic device FTO/Sb₂Se₃/CdS/ZnO/ZnO:Al/Au was constructed, achieving an encouraging 2.1% solar conversion efficiency