Factors contributing to the oxygen concentration over the Qinghai-Tibetan Plateau and its contribution rate calculation

A decline in atmospheric oxygen concentration is projected in the 21st century given the background of global warming.The Qinghai-Tibetan Plateau is located at a high altitude,and thus,it faces a hypoxia challenge;however,knowledge of the factors contributing to its atmospheric oxygen concentration is still lacking.Here,we conducted joint observations of ecosystem oxygen production and carbon sinks and near-surface atmospheric oxygen concentrations on the Qinghai-Tibetan Plateau and meteorological elements at Beijing Fangshan Station.Using seasonal differences and statistical methods,we calculated the relative contribution rates of vegetation to changes in atmospheric oxygen concentration.Our results indicate that solar radiation,atmospheric humidity,and ecosystem oxygen consumption and production have a significant impact on the atmospheric oxygen concentration,and the impact shows temporal and spatial differences.Vegetation significantly impacts the oxygen concentration,with a contribution rate of 16.7%–24.5%,which is underestimated in existing research.Our findings provide important insights into the factors that influence atmospheric oxygen concentration and highlight the contribution of vegetation.To better understand the oxygen dynamics of the Qinghai-Tibetan Plateau,we recommend further field observations of soil respiration and vegetation photosynthesis to clarify the contributions of carbon storage,carbon sinks and other factors to the near-surface atmospheric oxygen concentration.

气候变化和人类活动对中国北方沙漠地区NDVI变化的影响

Vegetation plays a key role in maintaining ecosystem stability,promoting biodiversity conservation,serving as windbreaks,and facilitating sand fixation in deserts.Based on the Moderate Resolution Imaging Spectroradiometer Normalized Difference Vegetation Index(MODIS NDVI)and climate data,a Theil-Sen median trend analysis combined with the Mann-Kendall test and partial correlation and residual analyses were employed to explore spatiotemporal patterns of vegetation dynamics and key drivers in the Badain Jaran and Tengger deserts and Mu Us Sandy Land.Data were collected during the growing season between 2001 and 2020.Further analyses quantified the relative contribution of climate variation and anthropogenic activities to NDVI changes.Results revealed a predominantly increasing trend for average NDVI.The spread of average annual NDVI and growth trends of the vegetation were determined to be influenced by spatial differences.The area with improved vegetation was greater than that of the degraded region.Climate variability and human activities were driving forces controlling vegetation cover changes,and their effects on vegetation dynamics varied by region.The response of vegetation dynamics was stronger for precipitation than temperature,indicating that precipitation was the main climate variable influencing the NDVI changes.The relative role of human activities was responsible for>70%of the changes,demonstrating that human activities were the main driving factor of the NDVI changes.The implementation of ecological engineering is a key driver of increased vegetation coverage and has improved regional environmental quality.These results enhance our knowledge regarding NDVI change affected by climate variation and human activities and can provide future theoretical guidance for ecological restoration in arid areas.