Coastal wetlands are considered as significant carbon sinks due to their high efficiency in trapping sediments and primary productivity. During the past five decades, the coastal wetland in the Yellow River delta of China has been experiencing a rapid climate warming during winter and spring associated with a dramatic reduction in precipitation during summer and autumn. However, it remains unclear how these two seasonal climate changes will impact ecosystem CO2 exchange in this region. Since 2017, a field manipulative experiment was conducted to examine the main and interactive effects of winter-spring warming (+2 ℃) and summer-autumn drought (-50% rainfall) on ecosystem CO2 exchange in a coastal wetland in the Yellow River delta. Net ecosystem CO2 exchange (NEE) and its two components, including gross ecosystem production (GEP) and ecosystem respiration (ER), were measured bi-weekly since June 2017.
Results/Conclusions
Based on the measurements from June 2017 to June 2018, we found that summer-autumn drought significantly reduced the growing-season NEP, while winter-spring warming significantly increased NEP in the following growing season. Interestingly, a significant interactive effect between drought and warming was detected on NEP and its two components. A significant reduction of NEP was observed in the treatment of warming plus drought in the first year. These results suggest that the response of wetland carbon cycle to climate change could be more elusive than terrestrial ecosystems, in which the influences of multiple climate-change drivers are commonly additive. The ecological mechanisms underlying such seasonal-scale interactions between drought and warming are crucial for predicting the carbon feedback of coastal wetlands to future climate change.