CO 2 Exchange in an Alpine Swamp Meadow on the Central Tibetan Plateau

Abstract

Alpine wetland on the Qinghai-Tibetan Plateau holds the highest organic carbon density of plateau ecosystems and is among the most sensitive areas to climate change. Understanding CO₂ exchange and its environmental forces in this specific ecosystem can benefit constraints of carbon budgets from site to global scale under future climate change. Here we investigated CO₂ flux measurements from 2009 to 2013 in a wide-distributed alpine wetland, Kobresia littledalei-Blysmus sinocompressus swamp meadow, by eddy covariance (EC) on the central Tibetan Plateau. Results showed diurnal variation of net ecosystem CO₂ exchange (NEE) was affected by photosynthetically active radiation (PAR), and this alpine swamp meadow had a high maximum ecosystem photosynthesis rate (Amax) with 32.96 μmol CO₂ m⁻² s⁻¹. Nighttime ecosystem respiration (Re) rates were well associated with temperature, and average annual temperature sensitivity of Re (Q₁₀) was 3.2. Both temperature and relative humidity (RH) played key roles in regulations of seasonal NEE, and their interactive effect was only significant in GS, especially when soil temperature at 10 cm was above 6.3 °C. Our results suggested this alpine swamp meadow was a stable CO₂ sink with an annual accumulation of −161.85 ± 28.02 g C m⁻². However, response of annual Re was more sensitive than GPP to change of temperature and length of growing season (LOG), which implied that future climate warming likely to weaken the CO₂ sink of this alpine swamp meadow.

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