The atmospheric carbon dioxide (CO2) record displays a prominent seasonal cycle that arises mainly from changes in vegetation growth and the corresponding CO2 uptake during the boreal spring and summer growing seasons and CO2 release during the autumn and winter seasons. The CO2 seasonal amplitude has increased over the past five decades, suggesting an increase in Northern Hemisphere biospheric activity. It has been proposed that vegetation growth may have been stimulated by higher concentrations of CO2 as well as by warming in recent decades, but such mechanisms have been unable to explain the full range and magnitude of the observed increase in CO2 seasonal amplitude. Here we suggest that the intensification of agriculture (the Green Revolution, in which much greater crop yield per unit area was achieved by hybridization, irrigation and fertilization) during the past five decades is a driver of changes in the seasonal characteristics of the global carbon cycle. Our analysis of CO2 data and atmospheric inversions shows a robust 15 per cent long-term increase in CO2 seasonal amplitude from 1961 to 2010, punctuated by large decadal and interannual variations. Using a terrestrial carbon cycle model that takes into account high-yield cultivars, fertilizer use and irrigation, we find that the long-term increase in CO2 seasonal amplitude arises from two major regions: the mid-latitude cropland between 25° N and 60° N and the high-latitude natural vegetation between 50° N and 70° N. The long-term trend of seasonal amplitude increase is 0.311 ± 0.027 per cent per year, of which sensitivity experiments attribute 45, 29 and 26 per cent to land-use change, climate variability and change, and increased productivity due to CO2 fertilization, respectively. Vegetation growth was earlier by one to two weeks, as measured by the mid-point of vegetation carbon uptake, and took up 0.5 petagrams more carbon in July, the height of the growing season, during 2001-2010 than in 1961-1970, suggesting that human land use and management contribute to seasonal changes in the CO2 exchange between the biosphere and the atmosphere.
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http://dx.doi.org/10.1038/nature13893 | DOI Listing |
Sci Rep
December 2024
School of Ecology, Hainan University, Haikou, 570228, China.
Climate change and human activities are the primary drivers influencing changes in runoff dynamics. However, current understanding of future hydrological processes under scenarios of gradual climate change and escalating human activities remains uncertain, particularly in tropical regions affected by deforestation. Based on this, we employed the SWAT model coupled with the near future (2021-2040) and middle future (2041-2060) global climate models (GCMs) under four shared socioeconomic pathways (SSP1-2.
View Article and Find Full Text PDFJ Pineal Res
January 2025
Department of Integrated Biology and Physiology, University of Minnesota, Minneapolis, Minnesota, USA.
Light environment in the Arctic differs widely with the seasons. Studies of relationships between objectively measured circadian phase and amplitude of light exposure and melatonin in community-dwelling Arctic residents are lacking. This investigation combines cross-sectional (n = 24-62) and longitudinal (n = 13-27) data from week-long actigraphy (with light sensor), 24-h salivary melatonin profiles, and proxies of metabolic health.
View Article and Find Full Text PDFCureus
November 2024
Third Department of Obstetrics and Gynecology, National and Kapodistrian University of Athens, Attiko Hospital, Athens, GRC.
Introduction: The seasonality of human births has been studied globally for over two centuries, revealing diverse patterns across populations shaped by intricate interactions involving both biological and socio-cultural factors. This study offers a thorough examination of national birth data in Greece spanning from 1956 to 2022, aiming to elucidate long-term trends and changes in seasonal birth patterns.
Materials And Methods: Data on live births in Greece were categorized by month based on national registries, and the analysis of birth seasonality was conducted annually.
Plants (Basel)
November 2024
Northeast Asia Ecosystem Carbon Sink Research Center (NACC), Key Laboratory of Sustainable Forest Ecosystem Management, Ministry of Education, School of Ecology, Northeast Forestry University, Harbin 150040, China.
Understanding the sensitivity of ecosystem respiration (ER) to increasing temperature is crucial to predict how the terrestrial carbon sink responds to a warming climate. The temperature sensitivity of ER may vary on a diurnal basis but is poorly understood due to the paucity of observational sites documenting real ER during daytime at a global scale. Here, we used an improved flux partitioning approach to estimate the apparent temperature sensitivity of ER during the daytime (E) and nighttime (E) derived from multiyear observations of 189 FLUXNET sites.
View Article and Find Full Text PDFJ Sports Sci
December 2024
Faculty of Kinesiology and Health Studies, University of Regina, Regina, SK, Canada.
Assessment of cerebral oxygenation during repeated squat stands following an acute sport-related concussion (SRC) has the potential to identify physiological changes following SRC. All varsity university athletes completed a pre-season assessment and 53 were followed up within 5-days of suffering an SRC. Of the 53 participants, 29 had continuous beat-to-beat blood pressure (BP; sampled at 200 hz) collected by finger photoplethysmography, and 53 had right prefrontal cortex oxygenation collected by near-infrared spectroscopy (NIRS; sampled at 10 hz).
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