Time-lag effects of vegetation gross primary production response to the hydro-climate changes in humid and semi-humid areas of China

Study region: Hanjiang River Basin (HRB), sub-basin of Yangtze River Basin, locates in center of China, a typical humid and sub-humid region. Study focus: This study examined the relationship between vegetation gross primary production (GPP), precipitation (P), temperature (T), and the residual of basin water balance (basin water storage, ∆S). Moreover, the time-lag effects of GPP response to the factors were also delved deeper in the typical humid and semi-humid basin. New hydrological insights for the region: The overall GPP in HRB presented an increasing trend during 2001–2018. A robust correlation was observed between GPP and T on monthly, seasonal and annual scales. Yet P only exhibited relatively strong correlation with GPP on monthly scale, while ∆S manifested its influence on GPP on annual scale. The time-lag between GPP and ∆S was 4 months. This delaying effect displays most obvious in spring and winter. The previous P showed negative effects on GPP. In contrast, T did not show obvious time-lag effects on GPP. To sum up, the hydrological factors showed relative long-term effects on GPP compared to the instant response of GPP to T. The delayed response of GPP to basin water storage highlighted the persistence and enduring effects of hydrological conditions on GPP in humid and semi-humid areas, especially on medium to long-term time scales.