Integrating physiological threshold experiments with climate modeling to project mangrove species’ range expansion

Predictions of climate-related shifts in species ranges have largely been based on correlative models. Due to limitations of these models, there is a need for more integration of experimental approaches when studying impacts of climate change on species distributions. Here, we used controlled experiments to identify physiological thresholds that control poleward range limits of three species of mangroves found in North America. We found that all three species exhibited a threshold response to extreme cold, but freeze tolerance thresholds varied among species. From these experiments, we developed a climate metric, freeze degree days (FDD), which incorporates both the intensity and the frequency of freezes. When included in distribution models, FDD accurately predicted mangrove presence/absence. Using 28 years of satellite imagery, we linked FDD to observed changes in mangrove abundance in Florida, further exemplifying the importance of extreme cold. We then used downscaled climate projections of FDD to project that these range limits will move northward by 2.2–3.2 km yr⁻¹ over the next 50 years

A multifault earthquake threat for the Seattle metropolitan region revealed by mass tree mortality

This is the final version. Available on open access from the American Association for the Advancement of Science via the DOI in this recordData and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and Supplementary Materials. The MacBlo, Price Lake, Hamma Hamma, Lake Washington, West Point log, Lake Sammamish, and Dry Bed Lake tree-ring measurement data will be available upon publication through the U.S. National Oceanic and Atmospheric Administration World Data Service for Paleoclimatology International Tree-Ring Databank (www.ncei.noaa.gov/products/paleoclimatology/tree-ring) as datasets CAN382 and WA155 to WA160. All radiocarbon data are provided in table S2.Compound earthquakes involving simultaneous ruptures along multiple faults often define a region’s upper threshold of maximum magnitude. Yet, the potential for linked faulting remains poorly understood given the infrequency of these events in the historic era. Geological records provide longer perspectives, although temporal uncertainties are too broad to clearly pinpoint single multifault events. Here, we use dendrochronological dating and a cosmogenic radiation pulse to constrain the death dates of earthquake-killed trees along two adjacent fault zones near Seattle, Washington to within a 6-month period between the 923 and 924 CE growing seasons. Our narrow constraints conclusively show linked rupturing that occurred either as a single composite earthquake of estimated magnitude 7.8 or as a closely spaced double earthquake sequence with estimated magnitudes of 7.5 and 7.3. These scenarios, which are not recognized in current hazard models, increase the maximum earthquake size needed for seismic preparedness and engineering design within the Puget Sound region of >4 million residents.U.S. Geological Surve

Nutrient enrichment shifts mangrove height distribution: Implications for coastal woody encroachment

<div><p>Global changes, such as increased temperatures and elevated CO₂, are driving shifts in plant species distribution and dominance, like woody plant encroachment into grasslands. Local factors within these ecotones can influence the rate of regime shifts. Woody encroachment is occurring worldwide, though there has been limited research within coastal systems, where mangrove (woody shrub/tree) stands are expanding into salt marsh areas. Because coastal systems are exposed to various degrees of nutrient input, we investigated how nutrient enrichment may locally impact mangrove stand expansion and salt marsh displacement over time. We fertilized naturally co-occurring <i>Avicennia germinans</i> (black mangrove) and <i>Spartina alterniflora</i> (smooth cordgrass) stands in Port Aransas, TX, an area experiencing mangrove encroachment within the Northern Gulf of Mexico mangrove-marsh ecotone. After four growing seasons (2010–2013) of continuous fertilization, <i>Avicennia</i> was more positively influenced by nutrient enrichment than <i>Spartina</i>. Most notably, fertilized plots had a higher density of taller (> 0.5 m) mangroves and mangrove maximum height was 46% taller than in control plots. Fertilization may promote an increase in mangrove stand expansion within the mangrove-marsh ecotone by shifting <i>Avicennia</i> height distribution. <i>Avicennia</i> individuals, which reach certain species-specific height thresholds, have reduced negative neighbor effects and have higher resilience to freezing temperatures, which may increase mangrove competitive advantage over marsh grass. Therefore, we propose that nutrient enrichment, which augments mangrove height, could act locally as a positive feedback to mangrove encroachment, by reducing mangrove growth suppression factors, thereby accelerating the rates of increased mangrove coverage and subsequent marsh displacement. Areas within the mangrove-marsh ecotone with high anthropogenic nutrient input may be at increased risk of a regime shift from grass to woody dominated ecosystems.</p></div

Identity Styles, Positive Youth Development, and Civic Engagement in Adolescence

Identity formation is a core developmental task of adolescence. Adolescents can rely on different social-cognitive styles to seek, process, and encode self-relevant information: information-oriented, normative, and diffuse-avoidant identity styles. The reliance on different styles might impact adolescents' adjustment and their active involvement in the society. The purpose of this study was to examine whether adolescents with different identity styles report differences in positive youth development (analyzed with the Five Cs-Competence, Confidence, Character, Connection, and Caring-model) and in various forms of civic engagement (i.e., involvement in school self-government activities, volunteering activities, youth political organizations, and youth non-political organizations). The participants were 1,633 (54.1 % female) 14-19 years old adolescents (Mage = 16.56, SDage = 1.22). The findings indicated that adolescents with different identity styles differed significantly on all the Five Cs and on two (i.e., involvement in volunteering activities and in youth non-political organizations) forms of civic engagement. Briefly, adolescents with an information-oriented style reported high levels of both the Five Cs and civic engagement; participants with a normative style reported moderate to high scores on the Five Cs but low rates of civic engagement; diffuse-avoidant respondents scored low both on the Five Cs and on civic engagement. These findings suggest that the information-oriented style, contrary to the diffuse-avoidant one, has beneficial effects for both the individual and the community, while the normative style has quite beneficial effects for the individual but not for his/her community. Concluding, adolescents with different identity styles display meaningful differences in positive youth development and in rates of civic engagement