Ecosystem-atmosphere exchanges of carbon dioxide (CO₂) and water vapor were investigated in a moist mountain meadow (Loney Meadow) at 1822 m MSL in the Sierra Nevada, California, USA. An eddy covariance (EC) tower was deployed for most of the snow-free period from May to September 2016. The meadow ecosystem progressed from a strong sink of CO₂ in the peak of the growing season under saturated to wet soil conditions (−18.51 gC m⁻² d⁻¹) to a weak source (2.97 gC m⁻² d⁻¹) following a rapid decline in soil moisture as runoff decreased. The variability of Net Ecosystem Exchange (NEE) over diurnal, synoptic and seasonal timescales was dominated by Gross Primary Production (GPP) which ranged from 43 gC m⁻² d⁻¹ during the peak of the growing season to 19 gC m⁻² d⁻¹ during senescence. Ecosystem respiration was small in magnitude and variability compared to GPP. Approximations of annual NEE for the meadow ranged from −285 to −450 gC m⁻² yr⁻¹, which is high compared to grasslands, and more similar to mature wetland or forest ecosystems. At diurnal and synoptic scales, CO₂ flux was driven most strongly by photosynthetically active radiation (PAR), while seasonally, the ecosystem was linked closely to changes in soil moisture. Light-use and water-use efficiencies of the meadow ecosystem were high compared with those found in most other ecosystems using comparable observations. These results suggest meadows have the potential to be large sinks of atmospheric CO₂ and that their ability to do so is sensitive to water table height. This is important for understanding the future of carbon sequestration in mountain meadows in the context of changing hydroclimates and different land management decisions that impact meadow hydrology.

在美国加利福尼亚内华达山脉的湿山草甸（Loney Meadow），MSL为1822 m MSL，研究了生态系统-大气中二氧化碳（CO ₂）和水蒸气的交换。在2016年5月至2016年9月的大部分无雪期间，都部署了涡旋协方差（EC）塔。在饱和至湿润的土壤条件下，草甸生态系统在生长季节的高峰期从强大的CO ₂吸收池发展而来（−18.51 gC m ^-2 d ^-1）转化为弱源（2.97 gC m ^-2 d ^-1），之后土壤水分随着径流减少而迅速下降。净生态系统交换（NEE）的可变性）在昼夜，天气和季节尺度上，总初级生产力（GPP）占主导地位，其范围从生长期高峰期间的43 gC m ^-2 d ^-1到衰老期间的19 gC m ^-2 d ^-1。与GPP相比，生态系统呼吸的幅度和变异性小。草地的年度NEE近似值介于-285至-450 gC m ^-2  yr ^-1之间，与草原相比较高，并且与成熟的湿地或森林生态系统更为相似。在昼夜和天气尺度上，CO ₂通量受光合有效辐射（PAR），但在季节性情况下，生态系统与土壤水分的变化密切相关。与其他大多数生态系统相比，草甸生态系统的光利用效率和水利用效率与可比较的观测结果相比较高。这些结果表明，草甸有可能成为大气中CO _2的大汇，而这样做的能力对地下水位高度很敏感。这对于了解不断变化的水气候和影响草甸水文学的不同土地管理决策的背景下山区草甸碳固存的未来至关重要。