Photosynthetic sensitivity to historic meteorological variability for conifers in the eastern Sierra Nevada

Increased climatic variability can impact tree physiological processes beyond what is predicted from changes in mean conditions. We assessed the sensitivity of conifer saplings to spatial and temporal variability in meteorological conditions, taking advantage of the end of California's historic drought and the exceedingly wet winter of 2017. We sought to understand how very dry and very wet conditions constrain photosynthesis and growth in four regionally dominant conifers and whether sensitivity in these processes changes across a 500 m gradient in elevation. All species demonstrated phenotypic plasticity in response to temporal differences in precipitation on both inter-annual and seasonal timescales. Net photosynthesis in Pinus contorta decreased from an early season 2016 average of 12.4 to 6.89 μmol CO₂ m^-2 s^-1 later in the summer, but increased 14.1% between seasons in the wet year. By contrast, elevation had almost no effect on instantaneous photosynthetic gas exchange, CO₂ response curve parameters, or stem water potential in any of the years for any of the species. Effects of the heavy snow year (2017) on needle growth differed between elevations. Pinus contorta showed a 38.9% increase in average needle length at the lower two elevations but a 31.6% decrease at the highest site compared to the height of the drought. Despite these differences, biological variation was dampened compared to the physical variation between years, suggesting these trees can effectively withstand substantial meteorological variability. Our results show that these species demonstrated considerable ability to tolerate and recover from an extreme drought event.

Impacts of urbanization and long-term meteorological variations on global PM2.5 and its associated health burden

PM_2.5 pollution has adverse health effects on humans. Urbanization and long-term meteorological variations play important roles in influencing the PM_2.5 concentration and its associated health effects. Our results indicate that the urbanization process can enhance the PM_2.5 concentration globally. The PM_2.5-caused mortality density (deaths/100 km²) is also positively correlated with the urbanization degree in both developed and developing countries. The results from machine learning technique revealed that the meteorology-driven variation in PM_2.5-caused health burden has increased with the increase in the urbanization degree from 1980 to 2018, suggesting that residents living in urban areas are more vulnerable to experiencing unfavorable meteorological conditions (e.g. low wind speed and planetary boundary layer height). The maximum difference in PM_2.5-caused mortality due to the variation in annual meteorological conditions (between 2013 and 1986) was 270 600 (196 800-317 900). Our findings indicate an urgent need to understand the driving force behind the appearance of unfavorable meteorological situations and propose suitable climate mitigation measures.

Meteorological Variation Is a Predisposing Factor for Aneurismal Subarachnoid Hemorrhage: A 5-Year Multicenter Study in Fuzhou, China

OBJECTIVE

The climatic characteristics of aneurysmal subarachnoid hemorrhage (aSAH) have been reported, but consensus has not yet been reached. It is of great significance to elucidate the relationships between meteorological variation and aSAH in regions with specific climate patterns. We analyzed the occurrence of aSAH in the capital city of Fujian Province, China, through a multicenter, 5-year study, and aimed to reveal the meteorological influences on aSAH in the coastal city of eastern Fujian under the subtropical marine monsoon condition.

METHODS

A total of 2555 consecutive patients with aSAH in Fuzhou were collected using specialized stroke admission database from January 2013 to December 2017. Meteorological parameters including temperature, atmospheric pressure, and humidity were obtained from China Surface Meteorological Station during the same period. Poisson regression was used to explore the association between meteorological parameters and aSAH to calculate the incidence rate ratios (IRRs) with corresponding 95% confidence intervals (CIs). Generalized additive model analysis further revealed the nonlinear relationships between weather and aSAH.

RESULTS

Daily minimum temperature (IRR 0.976, 95% CI 0.958-0.996) and maximum pressure (IRR 1.022, 95% CI 1.001-1.042) were independently correlated with the onset of aSAH. Low temperature (below 16°C) and excessive atmospheric pressure (above 1008 hPa) increased the risk of aSAH. In addition, March in spring and December in winter were the 2 ictus peaks in Fuzhou throughout the year.

CONCLUSIONS

Cold and excessive atmospheric pressure are triggers for the occurrence of aSAH; March in spring and December in winter are the predominant onset periods in Fuzhou.

The use of conifer needles as biomonitor candidates for the study of temporal air pollution variation in the Strasbourg region

The continuous emission of polluting chemicals into the atmosphere requires the implementation of monitoring of ambient air quality. The use of vegetation for environmental monitoring can be considered as a simple monitoring technique by providing a cheap and accessible matrix. In this study, needles of two conifers (Pinus nigra and Cedrus atlantica), were used for the consecutive biomonitoring of multipollutants such as pesticides, polychlorinated biphenyls, and polyaromatic hydrocarbons (PAHs) in an urban area in Strasbourg (France). The extraction was performed by accelerated solvent extraction, solid-phase extraction, and solid-phase microextraction and was followed by gas chromatography coupled to tandem mass spectrometry and liquid chromatography coupled to tandem mass spectrometry analyses. The results obtained for conifer samples collected in 5 successive weeks (April 09-May 07, 2015) show a similar variation of the different types of pollutants. A pollution peak was observed during the second week of analysis, and the concentration of all pollutants then decreased to complete disappearance at the end of the sampling period. PAHs were the most concentrated with a total concentration of about 35.87 ng g^-1, and naphthalene was, among these pollutants, the most concentrated with a total concentration of about 15.1 ng g^-1. The analysis of meteorological data during this period suggests that the results correlated with climatic conditions that widely vary during this period of the year. The results show that the concentration peak was obtained when no precipitation was detected.