Carbonyl sulfide (COS) is a tracer of ecosystem photosynthesis that can advance carbon cycle research from leaf to global scales; however, a range of newly reported caveats related to sink/source strength of various ecosystem components hinder its application. Using comprehensive eddy-covariance and chamber measurements, we systematically measure ecosystem contributions from leaf, stem, soil, and litter and were able to close the ecosystem COS budget. The relative contributions of nonphotosynthetic components to the overall canopy-scale flux are relatively small (~4% during peak activity season) and can be independently estimated based on their responses to temperature and humidity. Converting COS to photosynthetic CO fluxes based on the leaf relative uptake of COS/CO , faces challenges due to observed daily and seasonal changes. Yet, this ratio converges around a constant value (~1.6), and the variations, dominated by light intensity, were found unimportant on a flux-weighted daily time-scale, indicating a mean ratio of daytime gross-to-net primary productivity of ~2 in our ecosystem. The seasonal changes in the leaf relative uptake ratio may indicate a reduction in mesophyll conductance in winter, and COS-derived canopy conductance permitted canopy temperature estimate consistent with radiative skin temperature. These results support the feasibility of using COS as a powerful and much-needed means of assessing ecosystem function and its response to change.
Observations in the semi-arid Loess Plateau area of north-west China are utilized to reveal the characteristics and variations in the seasonal distribution of dewfall (frost) and the influence of micrometeorology, precipitation, and other weather conditions. Precipitation is the dominant water source in the Loess Plateau; however, non-rainfall water accounts for 13 % of the total land-surface water source. Dew is the second largest non-rainfall component next only to soil adsorption water. Observations show that dew (frost) occurrence is likely to occur when an inversion occurs between the heights of 1 and 4 m with a temperature difference of 0.25 K, surface wind speed of 1.5 m s −1 , and surface relative humidity greater than 80 %.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.