Responses of gross primary productivity in different types of terrestrial ecosystems to interannual variation in the northern boundary of the East Asian summer monsoon

The northern boundary of the East Asian summer monsoon (EASMNB), located in the transitional zone from humid to arid regions, is characterized by significant north-south fluctuations. These fluctuations can exert profound impacts on the photosynthetic activity of vegetation by causing anomalous climate conditions, and thus play an important role in the carbon cycle over large parts of northern China. In general, a more northward position of the EASMNB generally leads to increasing precipitation and decreasing incoming solar radiation (ISR) over most of northern China. The increasing precipitation leads to positive GPP anomalies in the temperate grassland over the western part of northern China, where water scarcity issues cause the high reliance of vegetation photosynthesis on dry-wet variability. In contrast, the decreasing ISR favors the occurrence of negative signals in the forest ecosystems over the eastern part of northern China, which holds strong resilience and resistance to dry-wet variability but sensitivity to ISR-induced changes in the available energy. Under this circumstance, the GPP responses are characterized by a zonal dipole pattern over northern China, with positive and negative signals situated over the western and eastern parts, respectively. The reverse pattern is also true when the EASMNB adopts a more southward position. Our findings highlight the distinctive impacts of EASMNB fluctuations on GPP changes among different land-cover types. Considering that the EASMNB is expected to shift northward under global warming, our study thus can provide important implications for the study of regional carbon cycles in a warmer world.