Multiyear precipitation reduction strongly decrease carbon uptake over North China

Abstract. Drought has been a concern of global and regional water, carbon and energy cycles. From 1999 to 2011, North China experienced a multiyear precipitation reduction, which decreased significantly water availability as indicated by decreased soil moisture and Palmer Drought Severity Index. In this study, three light use efficiency models (CASA, MODIS-GPP and EC-LUE) and one dynamic vegetation model (IBIS) were used to characterize the impacts of long-term drought on terrestrial carbon fluxes over the North China. All of four models showed the reduction in averaged GPP of 0.026–0.047 Pg C yr⁻¹ from 1999 to 2011 compared to 1982–2011. Based on IBIS model, simulated ecosystem respiration fell from 1999 to 2011 by 0.016 Pg C yr⁻¹. Multiple precipitation reduction changed the regional carbon uptake of 0.0014 Pg C yr⁻¹ from 1982 to 1998 to a~net source of 0.018 Pg C yr⁻¹. Moreover, a pronounced decrease of maize yield was found ranging from 1999 to 2011 versus the average of 1978–2011 at almost all provinces over the study region. The largest reduction of maize yield occurred in the Beijing (2499 kg ha⁻¹ yr⁻¹), Jilin (2180 kg ha⁻¹ yr⁻¹), Tianjing (1923 kg ha⁻¹ yr⁻¹) and Heilongjiang (1791 kg ha⁻¹ yr⁻¹), and maize yield anomaly was significantly correlated with the precipitation through May and September over the entire study area. Our results revealed that recent climate change, and especially drought-induced water stress, is the dominant cause of the reduction in the terrestrial carbon sink.