Nitrogen forms affect root structure and water uptake in the hybrid poplar

The study analyses the effects of two different forms of nitrogen fertilisation (nitrate and ammonium) on root structure and water uptake of two hybrid poplar (Populus maximowiczii x P. balsamifera) clones in a field experiment. Water uptake was studied using sap flow gauges on individual proximal roots and coarse root structure was examined by excavating 18 whole-root systems. Finer roots were scanned and analyzed for architecture. Nitrogen forms did not affect coarse-root system development, but had a significant effect on fine-root development. Nitrate-treated trees presented higher fine:coarse root ratios and higher specific root lengths than control or ammonium treated trees. These allocation differences affected the water uptake capacity of the plants as reflected by the higher sapflow rate in the nitrate treatment. The diameter of proximal roots at the tree base predicted well the total root biomass and length. The diameter of smaller lateral roots also predicted the lateral root mass, length, surface area and the number of tips. The effect of nitrogen fertilisation on the fine root structure translated into an effect on the functioning of the fine roots forming a link between form (architecture) and function (water uptake)

Evapotranspiration and water use efficiency in relation to climate and canopy nitrogen in U.S. forests

Understanding relations among forest carbon (C) uptake and water use is critical for predicting forest-climate interactions. Although the basic properties of tree-water relations have long been known, our understanding of broader-scale patterns is limited by several factors including (1) incomplete understanding of drivers of change in coupled C and water fluxes and water use efficiency (WUE), (2) difficulty in reconciling WUE estimates obtained at different scales, and (3) uncertainty in how evapotranspiration (ET) and WUE vary with other important resources such as nitrogen (N). To address these issues, we examined ET, gross primary production (GPP), and WUE at 11 AmeriFlux sites across North America. Our analysis spanned leaf and ecosystem scales and included foliar δ13C, δ18O, and %N measurements; eddy covariance estimates of GPP and ET; and remotely sensed estimates of canopy %N. We used flux data to derive ecosystem WUE (WUEe) and foliar δ13C to infer intrinsic WUE. We found that GPP, ET, and WUEe scaled with canopy %N, even when environmental variables were considered, and discuss the implications of these relationships for forest-atmosphere-climate interactions. We observed opposing patterns of WUE at leaf and ecosystem scales and examined uncertainties to help explain these opposing patterns. Nevertheless, significant relationship between C isotope-derived ci/ca and GPP indicates that δ13C can be an effective predictor of forest GPP. Finally, we show that incorporating species functional traits—wood anatomy, hydraulic strategy, and foliar %N—into a conceptual model improved the interpretation of Δ13C and δ18O vis-à-vis leaf to canopy water-carbon fluxes

WHAT ARE THE RISKS ASSOCIATED WITH DIFFERENT SELECTIVE SEROTONIN RE-UPTAKE INHIBITORS (SSRIS) TO TREAT DEPRESSION AND ANXIETY IN PREGNANCY? AN EVALUATION OF CURRENT EVIDENCE

A literature review was conducted to elucidate the respective reproductive safety profiles of different SSRIs to inform the prescribing practices of doctors treating pregnant women with anxiety and depression. Background: Women are most likely to be diagnosed with depression or anxiety between the ages of 25 and 44 years, which are also the years of childbearing potential (Burke et al., 1991). Therefore a substantial number of women face a decision about whether or not to take an antidepressant or anxiolytic during pregnancy. There are no psychotropic medications that have UK marketing authorisation (NICE, 2014), no clear clinical consensus has been reached regarding the use of SSRIs in pregnancy, and clinicians lack a resource which discusses the reproductive safety profiles of different SSRIs rather than the class of drugs as a whole. Subjects and methods: We performed a search for the English language literature indexed on MEDLINE/PubMed for the period 2012 to 2017, using the following key terms: fluoxetine, prozac, paxil, oxactin, paroxetine, seroxat, sertraline, lustral, citalopram, cipramil, escitalopram, cipralex, fluvoxamine, faverin, with \u27pregnant woman\u27, \u27pregnant women\u27, pregnancy. We excluded general SSRI and pregnancy articles (although we did read these papers for valuable background information) because we are interested in elucidating the differences between the drugs in this class, rather than the general effects of the SRRI class as a whole. Results: The literature shows that paroxetine and fluoxetine have the strongest association with negative outcomes (significant malformations, PPHN and PNAS) whilst the associations between sertraline and citalopram with negative outcomes remains mixed and generally unsubstantiated when studies that show an association are controlled for the effects of maternal depression and associated factors. There are too few studies to draw definite conclusions regarding the safety of escitalopram and fluvoxamine. Conclusions: Sertraline and citalopram should be first-line drug treatments for anxiety and depression in pregnant women in the SSRI class. Sertraline can be continued in breast-feeding as the concentration found in breast milk is very low and has not been linked to infant complications. Furthermore, it would be useful to assess GPs current knowledge and confidence levels about prescribing, to see whether further education is needed in this area to encourage an open discussion of the risks and benefits of medication or no medication. It would also be useful to conduct further research on escitalopram which is likely to grow in popularity in the coming years as it came off patent in 2012. When these holes are filled, a clinical protocol for treating anxiety and depression in pregnant women should be created and implemented for the UK population

Variation in the access to deep soil water pools explains tree-to-tree differences in drought-triggered dieback of Mediterranean oaks

Individual differences in the access to deep soil water pools may explain the differential damage among coexisting, conspecific trees as a consequence of drought-induced dieback. We addressed this issue by comparing the responses to a severe drought of three Mediterranean oak species with different drought tolerance, Quercus pubescens L. and Quercus frainetto Ten., mainly thriving at xeric and mesic sites, respectively, and Quercus cerris L., which dominates at intermediate sites. For each species, we compared coexisting declining (D) and non-declining (ND) trees. The stable isotope composition (d2H, d18O) of xylem and soil water was used to infer a differential use of soil water sources. We also measured tree size and radial growth to quantify the long-term divergence of wood production between D and ND trees and non-structural carbohydrates (NSCs) in sapwood to evaluate if D trees presented lower NSC values. The ND trees had access to deeper soil water than D trees except in Q. frainetto, as indicated by significantly more depleted xylem water values. However, a strong d2H offset between soil and xylem water isotopes observed in peak summer could suggest that both tree types were not physiologically active under extreme drought conditions. Alternative processes causing deuterium fractionation, however, could not be ruled out. Tree height and recent (last 15-25 years) growth rates in all species studied were lower in D than in ND trees by 22 and 44%, respectively. Lastly, there was not a consistent pattern of NSC sapwood concentration; in Q. pubescens, it was higher in ND trees while in Q. frainetto, the D trees were the ones exhibiting the higher NSC concentration. We conclude that the vulnerability to drought among conspecific Mediterranean oaks depends on the differential access to deep soil water pools, which may be related to differences in rooting depth, tree size and growth rate

XLA Petiole Index: A Novel Hydraulic Function Metric for Interpreting Drought-Induced Dieback in Mediterranean Ring-Porous Oak Forests

Climate-induced forest mortality is an increasing global phenomenon occurring at both regional and local scales, with implications for ecosystem functioning and the provision of essential ecosystem services. In recent years, the Italian peninsula has experienced widespread oak forest decline, with forests showing increased susceptibility to severe heat waves and prolonged droughts. Our study examined a drought-induced tree mortality episode in the Mediterranea region (Pollino National Park, Southern Italy) focusing on deciduous oak forest stands (Quercus frainetto Ten.). We employed a comprehensive approach, combining ecophysiological and dendro-ecological analyses to compare non-decaying (ND) and decaying (D) coexisting trees. Recent advancements in understanding the relationship between petiole xylem anatomy and leaf form and function have revealed a positive correlation between petiole vessel diameter and leaf size, both within and across species. Leaf petioles, serving as the singular entry point for water into the leaf venation system, offer a standardized basis for comparing xylem investment with downstream transpirational demands. To quantify this relationship, we employed a novel index derived from quantitative wood anatomy of petioles. This integrative trait characterizes leaf water transport function by measuring the ratio of cross-sectional xylem area (XA) at the petiole to the downstream leaf area, termed the XLA petiole Index. Our assessment of XLA petiole variation can provide evidence supporting a safety-efficiency trade-off in oak leaves, a crucial aspect of plant hydraulic strategy

Variation in the use of soil water sources explains drought-induced decline of oak species in southern Italy

Widespread forest dieback and increased mortality rates have been described for Mediterranean oak species as a consequence of rising temperatures and drying trends. Here, we investigated if there are differences in functioning regarding to soil water uptake by comparing asymptomatic and symptomatic coexisting trees, and by using oxygen d18O and hydrogen d2H isotopic compositions of soil and xylem water. We used as study system oak stands (Q. pubescens, Q. cerris, Q. frainetto) located in southern Italy where several cases of drought-induced dieback episodes have been recently reported. We sampled couples of neighboring declining (D) and non-declining (ND) trees for all species during the most extreme drought episode occurred in the last decade (summer 2017) and measured xylem water isotope composition in branches. We used tree-ring width data for the retrospective characterization of the decline onset. Soil water at different depths was also monitored for stable isotopes alongside groundwater, which was estimated using two alternative methods: (i) the weighted average of monthly isotopic signatures of precipitation from October to April (soil recharge period in the Mediterranean) in the nearest site of the Italian Network of Isotopes in Precipitation; (ii) the average of samples of water collected from three nearby fountains (natural springs). By comparing stable isotopes in soil and xylem water, our results showed differences between declining and non-declining trees only in Q. cerris and Q. pubescens, where asymptomatic trees used less enriched water linked to access to deeper water sources. Most variability in water isotopes could be attributed to differences among the vigor classes that suggest an adaptive relevance of resource investment in deep roots as a strategy towards securing a source of water in dry environments where, in our case of study, particularly in species from less xeric areas such as Q. cerris and Q. pubescens in contrast to Q. frainetto, which is more aboundant in more xeric areas. The differentiation that was observed for 18O and 2H during the most important period of water shortage points to differences in water uptake patterns among coexisting symptomatic and asymptomatic oak trees, underpinning the adaptive relevance of the differential access to deep soil water pools in drought-prone regions

Variation in the access to deep soil water pools explains tree-to-tree differences in drought-triggered dieback of Mediterranean oaks

Individual differences in the access to deep soil water pools may explain the differential damage among coexisting, conspecific trees as a consequence of drought-induced dieback. We addressed this issue by comparing the responses to a severe drought of three Mediterranean oak species with different drought tolerance, Quercus pubescens L. and Quercus frainetto Ten., mainly thriving at xeric and mesic sites, respectively, and Quercus cerris L., which dominates at intermediate sites. For each species, we compared coexisting declining (D) and non-declining (ND) trees. The stable isotope composition (δ2H, δ18O) of xylem and soil water was used to infer a differential use of soil water sources. We also measured tree size and radial growth to quantify the long-term divergence of wood production between D and ND trees and non-structural carbohydrates (NSCs) in sapwood to evaluate if D trees presented lower NSC values. The ND trees had access to deeper soil water than D trees except in Q. frainetto, as indicated by significantly more depleted xylem water values. However, a strong δ2H offset between soil and xylem water isotopes observed in peak summer could suggest that both tree types were not physiologically active under extreme drought conditions. Alternative processes causing deuterium fractionation, however, could not be ruled out. Tree height and recent (last 15-25 years) growth rates in all species studied were lower in D than in ND trees by 22 and 44%, respectively. Lastly, there was not a consistent pattern of NSC sapwood concentration; in Q. pubescens, it was higher in ND trees while in Q. frainetto, the D trees were the ones exhibiting the higher NSC concentration. We conclude that the vulnerability to drought among conspecific Mediterranean oaks depends on the differential access to deep soil water pools, which may be related to differences in rooting depth, tree size and growth rate.This research was financially supported by the project OT4CLIMA (Italian Ministry of Education, University and Research (MIUR), Project N. ARS01_00405) ‘Advanced EO Technologies for studying climate change impacts on the environment’ and by the project ‘Alarm of forest mortality in Southern Italy’ (Gorgoglione Administration, Basilicata Region, Italy). M.C. was supported by the PhD program from the University of Basilicata (Italy). J.J.C. acknowledges funding by the project CGL2015-69186-C2-1-R project (Spanish Ministry of Economy). We acknowledge the E-OBS dataset from the EU-FP6 project UERRA (http://www.uerra.eu) and the data providers in the ECA&D project (https://www.ecad.eu)

SilvaCuore: a web-application to monitor the health status of Italian forests

In the current context of climate change, this paper provides a brief overview of climate-vegetation interactions in the Mediterranean basin, where global warming and aridification trends are predicted to intensify. Rising temperatures coupled with extreme drought events have notable impacts on forest ecosystems, triggering dieback and mortality phenomena worldwide. The health status of forest vegetation may be assessed by either ground surveys or remote sensing. Several investigations of declining oak forests in the Apennine region have shown that the drought vulnerability of Mediterranean oaks is dependent on differences in access to deep soil water pools, which can be related to differences in rooting depth, tree size and growth rate. Forest dieback is widely reported in Italy, but the extent and overall distribution of this phenomenon have not yet been well defined. Thus, understanding the future dynamics of forest stands has several key objectives: inventorying declining forest stands to gain insight into the phenomenon and create a national-level database; locating these stands to allow monitoring of their evolution over time; and monitoring to allow planning of mitigation measures, as well as recovery and adaptation strategies. This background led to the implementation of SilvaCuore, the first web application designed in Italy to report forest health status. Silvacuore is a web application developed with the aim of improving the link between citizens and the scientific community by contributing to the development of a valuable scientific database. The direct involvement of citizens in forest preservation offers an interesting perspective because the innovative use of technology can tap into citizens’ growing enthusiasm for environmental topics. Thus, SilvaCuore may be viewed from a dual perspective as a resource for the scientific community and as a unique opportunity for citizens to take an active role in research activities (Citizen Science project)

The need for an integrated approach for chronic disease research and care in Africa

With the changing distribution of infectious diseases, and an increase in the burden of non-communicable diseases, low- and middle-income countries, including those in Africa, will need to expand their health care capacities to effectively respond to these epidemiological transitions. The interrelated risk factors for chronic infectious and non-communicable diseases and the need for long-term disease management, argue for combined strategies to understand their underlying causes and to design strategies for effective prevention and long-term care. Through multidisciplinary research and implementation partnerships, we advocate an integrated approach for research and healthcare for chronic diseases in Africa