The sensitivity of ecosystem carbon cycle to climate change is an important issue in the context of future carbon neutrality across the globe. Because of the vast area， rich carbon storage， and vulnerability of the alpine grassland on the Qinghai-Tibetan Plateau， many site-specific studies have focused on the responses of carbon and water fluxes of alpine grassland to climate change in recent years. In such studies， various observation and simulation techniques， especially eddy correlation （EC） techniques， have been used. However， the sensitivity of different alpine grassland types to changes in climatic factors under the same climatic background remains unclear. Based on the estimates of carbon and water fluxes made using EC techniques from 2009 to 2011 under different water conditions， this study analyzed and compared the climate sensitivity of the carbon cycle between two adjacent （<5 km） alpine grassland ecosystems， alpine meadow and alpine wetland， in northern Tibet. The results showed that the carbon exchange capacity of alpine meadow was significantly lower than that of alpine wetland. The alpine meadow was carbon neutral with an annual net CO2 exchange （NEE） of 18.09±40.66 g C·m-2， while the alpine wetland was a stable carbon sink with an annual NEE of 155.09±32.85 g C·m-2. The moisture conditions weakly affected the maximum photosynthetic rate of the light response curves in both alpine meadow and alpine wetland， but was significantly positively correlated with gross primary productivity under saturated light intensity. The effect of moisture conditions to regulate the exponential response relationship between ecosystem respiration （Re） and temperature was mainly reflected by the basic respiration value （a）. The mean a value of alpine wetland was 3.76-times larger than that of alpine meadow， but the effect of moisture conditions to regulate the temperature sensitivity of Re （Q10） in the two alpine grasslands was not significant. The mean value of annual Q10 （1.84） and the trend of Q10 to decrease with temperature were basically the same in the alpine meadow and alpine wetland. We concluded that the response of CO2 exchange in the alpine grassland ecosystem in northern Tibet to environmental factors depends on joint restricting effects of multiple factors. Therefore， a regional network and collaborative observations are helpful to better understand the mechanism of the carbon exchange response of the alpine ecosystem to climate change.
