Long-Term Changes in Ionospheric Climate in Terms of foF2

There is not only space weather; there is also space climate. Space climate includes the ionospheric climate, which is affected by long-term trends in the ionosphere. One of the most important ionospheric parameters is the critical frequency of the ionospheric F2 layer, foF2, which corresponds to the maximum ionospheric electron density, NmF2. Observational data series of foF2 have been collected at some stations for as long as over 60 years and continents are relatively well covered by a network of ionosondes, instruments that measure, among others, foF2. Trends in foF2 are relatively weak. The main global driver of long-term trends in foF2 is the increasing concentration of greenhouse gases, namely CO2, in the atmosphere. The impact of the other important trend driver, the secular change in the Earth’s main magnetic field, is very regional, being positive in some regions, negative in others, and neither in the rest. There are various sources of uncertainty in foF2 trends. One is the inhomogeneity of long foF2 data series. The main driver of year-to-year changes in foF2 is the quasi-eleven-year solar cycle. The removal of its effect is another source of uncertainty. Different methods might provide somewhat different strengths among trends in foF2. All this is briefly reviewed in the paper.

Predicting Present and Future Suitable Climate Spaces (Potential Distributions) for an Armillaria Root Disease Pathogen (Armillaria solidipes) and Its Host, Douglas-fir (Pseudotsuga menziesii), Under Changing Climates

Climate change and associated disturbances are expected to exacerbate forest root diseases because of altered distributions of existing and emerging forest pathogens and predisposition of trees due to climatic maladaptation and other disturbances. Predictions of suitable climate space (potential geographic distribution) for forest pathogens and host trees under contemporary and future climate scenarios will guide the selection of appropriate management practices by forest managers to minimize adverse impacts of forest disease within forest ecosystems. A native pathogen (Armillaria solidipes) that causes Armillaria root disease of conifers in North America is used to demonstrate bioclimatic models (maps) that predict suitable climate space for both pathogen and a primary host (Pseudotsuga menziesii, Douglas-fir) under contemporary and future climate scenarios. Armillaria root disease caused by A. solidipes is a primary cause of lost productivity and reduced carbon sequestration in coniferous forests of North America, and its impact is expected to increase under climate change due to tree maladaptation. Contemporary prediction models of suitable climate space were produced using Maximum Entropy algorithms that integrate climatic data with 382 georeferenced occurrence locations for DNA sequence-confirmed A. solidipes. A similar approach was used for visually identified P. menziesii from 11,826 georeferenced locations to predict its climatic requirements. From the contemporary models, data were extrapolated through future climate scenarios to forecast changes in geographic areas where native A. solidipes and P. menziesii will be climatically adapted. Armillaria root disease is expected to increase in geographic areas where predictions suggest A. solidipes is well adapted and P. menziesii is maladapted within its current range. By predicting areas at risk for Armillaria root disease, forest managers can deploy suitable strategies to reduce damage from the disease.

Forest fires and climate-induced tree range shifts in the western US

Due to climate change, plant populations experience environmental conditions to which they are not adapted. Our understanding of the next century’s vegetation geography depends on the distance, direction, and rate at which plant distributions shift in response to a changing climate. In this study we test the sensitivity of tree range shifts (measured as the difference between seedling and mature tree ranges in climate space) to wildfire occurrence, using 74,069 Forest Inventory Analysis plots across nine states in the western United States. Wildfire significantly increased the seedling-only range displacement for 2 of the 8 tree species in which seedling-only plots were displaced from tree-plus-seedling plots in the same direction with and without recent fire. The direction of climatic displacement was consistent with that expected for warmer and drier conditions. The greater seedling-only range displacement observed across burned plots suggests that fire can accelerate climate-related range shifts and that fire and fire management will play a role in the rate of vegetation redistribution in response to climate change.

Past, present, and future climate space of the only endemic vertebrate genus of the Italian peninsula

The two extant Salamandrina species represent a unique case of morphology, ecology, and ethology among urodeles. The range of this genus is currently limited to Italy, where it represents the only endemic vertebrate genus, but its past range extended over a much broader area of Europe, including the Iberian and Balkan peninsulas. ENM analyses using modern occurrences of Salamandrina demonstrate that the current climate of the majority of Europe, and especially areas where fossils of this genus were found, is currently not suitable for this genus, neither was it suitable during the last 3.3 million years. This result allows possible assumptions about the climatic influence on the former extirpation of this salamander from several areas of Europe. Furthermore, it shows that, during Pliocene–Pleistocene climatic oscillations, Mediterranean peninsulas, despite being generally considered together because of similar latitude, had different potential to effectively become glacial refugia for this salamander, and possibly for other species as well. Future projections using different CO2 emission scenarios predict that climatic suitability will be even more drastically reduced during the next 50 years, underlining once more the importance of conservation strategies and emission-reducing policies.

Beneath the Bark: Assessing Woody Stem Water and Carbon Fluxes and Its Prevalence Across Climates and the Woody Plant Phylogeny

While woody stems are known to influence carbon and water dynamics, direct exchange with the atmosphere is seldom quantified, limiting our understanding of how these processes influence the exchange of mass and energy. The presence of woody stem chlorophyll in a diversity of climates and across a range of species suggests an evolutionary advantage to sustaining carbon assimilation and water relations through permeable stem tissue. However, no formal evaluation of this hypothesis has been performed. In this mini-review, we explore the interactions between woody stems and the atmosphere by examining woody stem photosynthesis and bark-atmosphere water exchange. Specifically, we address the following questions: (1) How do water and carbon move between the atmosphere and woody stems? (2) In what climate space is woody stem photosynthesis and bark water uptake advantageous? (3) How ubiquitous across plant families is woody stem photosynthesis and bark-atmosphere water exchange? In the literature, only seven species have been identified as exhibiting bark water uptake while over 300 species are thought to conduct woody stem photosynthesis. The carbon dioxide and water gained from these processes can offset respiration costs and improve plant water balance. These species span diverse biomes suggesting a broad prevalence of bark-atmosphere permeability. Finally, our results demonstrate that there may be an evolutionary component as demonstrated by a high Pagel’s lambda for the presence of stem photosynthesis. We end with recommendations for future research that explores how bark water and carbon interactions may impact plant function and mass flow in a changing climate.

The mechanism of snow shift affect seasonal streamflow in the contiguous US

<p>Climate warming has caused in a significant decrease in snowpack, increase in precipitation intensity and earlier melt onset. Based on earlier work published in 2014 on changes in streamflow resulting from a shift from snow towards rain, we analysed the sensitivity of seasonal streamflow to the average annual snow fraction in 253 catchments in CAMELS dataset, which have a record length more than 28 years and mean annual snow fraction larger than 15%. The result shows that places (or years) with higher mean annual snow fraction tend to have higher seasonal streamflow. We quantified seasonal sensitivity as a ratio of change in seasonal flow to change in annual snow fraction, for a given annual precipitation.  There are 91%，57% and 51% catchments which showed a positive sensitivity value for Spring, Summer and Winter streamflow, respectively. According to the results of seasonal sensitivity analysis in climate space, we found the largest seasonal sensitivity normally happens at the same regional climate. Places with higher average annual snow fraction tend to have the largest sensitivity in summer, while for places with lower annual snow fraction this largest sensitivity occurs in spring.</p><p>In order to explore the mechanism(s) by which snow fraction change affects seasonal streamflow, we summarized four hypothesised mechanisms from the literature: water-energy synchrony (Mechanism I), inputs exceed threshold (Mechanism II), demand-storage competition (Mechanism III), and energy partitioning (Mechanism IV). Most of the catchments in the western part of the contiguous US can be explained by the mechanism I, II, III and IV, while for catchments in the central US can be explained by mechanism II, III and IV. Catchments in the eastern part (and some scattered in the northern part) can be explained by mechanism III.  Other types of evidence are required to further distinguish between mechanisms in much of the USA. in further research we will use detailed data or hydrologic model to reproduce the hydrological process to find what are the hydrological processes responsible for precipitation phase partitioning changing with climate warming to influence catchment response. These findings would provide an evidence for how does snow affect hydrology, which may help to understand the effect of climate warming on future water resources in snow-dominated regions.</p>

Neither too early nor too late: Goldilocks litigation in the climate space

This opinion discusses Good Law Project’s approach to climate change litigation. It argues that the law has an important role in achieving positive change in the climate change space but that ‘successful’ legal outcomes are not the only extent of that role.

The impact of methodological decisions on climate reconstructions using WA-PLS

Most techniques for pollen-based quantitative climate reconstruction use modern assemblages as a reference data set. We examine the implication of methodological choices in the selection and treatment of the reference data set for climate reconstructions using Weighted Averaging Partial Least Squares (WA-PLS) regression and records of the last glacial period from Europe. We show that the training data set used is important because it determines the climate space sampled. The range and continuity of sampling along the climate gradient is more important than sampling density. Reconstruction uncertainties are generally reduced when more taxa are included, but combining related taxa that are poorly sampled in the data set to a higher taxonomic level provides more stable reconstructions. Excluding taxa that are climatically insensitive, or systematically overrepresented in fossil pollen assemblages because of known biases in pollen production or transport, makes no significant difference to the reconstructions. However, the exclusion of taxa overrepresented because of preservation issues does produce an improvement. These findings are relevant not only for WA-PLS reconstructions but also for similar approaches using modern assemblage reference data. There is no universal solution to these issues, but we propose a number of checks to evaluate the robustness of pollen-based reconstructions.

Intraspecific, ecotypic and home climate variation in photosynthetic traits of the widespread invasive grass Johnsongrass

Despite their near ubiquity across global ecosystems, the underlying mechanisms contributing to the success of invasive plants remain largely unknown. In particular, ecophysiological traits, which are fundamental to plants’ performance and response to their environment, are poorly understood with respect to geographic and climate space. We evaluated photosynthetic trait variation among populations, ecotypes and home climates (i.e. the climates from the locations they were collected) of the widespread and expanding invader Johnsongrass (Sorghum halepense). We found that populations vary in the maximum net photosynthetic flux and the light-saturated net photosynthetic rate, and that agricultural and non-agricultural ecotypes vary in apparent quantum yield and water-use efficiency (WUE). We also found that populations from warmer home climates had lower dark respiration rates, light compensation points and WUEs. As Johnsongrass expands across the USA the abiotic and biotic environments are driving variation in its genetics, phenotypes and its underlying physiology. Our study demonstrates the importance of evaluating physiological traits in invasive plants, especially as they relate to home climates.