Effect of changing precipitation in different periods on precipitation use efficiency in a semi-arid grassland

Question

Climate change intensifies global and regional water cycles, leading to changes in both the magnitude and timing of precipitation. Precipitation use efficiency (PUE) plays a crucial role in measuring the response of above-ground net primary productivity (ANPP) to precipitation changes. However, little is known about how changes in precipitation during different periods affect PUE.

Methods

Using a manipulation precipitation experiment in a semi-arid steppe, we simulated a 60% increase and decrease in precipitation during the early (April–June), late (July–September), and entire (April–September) growing seasons across 2015–2021 to examine the effects of changes in precipitation timing on PUE.

Results

The results showed that: (1) decreased precipitation in the late growing season (DLP) and whole growing season (DWP) stimulated PUE by an average of 0.14 and 0.12 g m⁻² mm⁻¹ yr⁻¹ respectively, whereas increased precipitation in the late growing season (ILP) and whole growing season (IWP) suppressed PUE by an average of 0.11 and 0.09 g m⁻² mm⁻¹ yr⁻¹ respectively. By contrast, neither decreased nor increased precipitation in the early growing season affected PUE; (2) the increased PUE under DLP was primarily attributed to the increase of PUE in grass (GR) and annuals and biennials (AB), whereas the elevation of PUE under DWP was mainly due to an increase of PUE in AB. By contrast, the reduction of PUE under ILP was mainly caused by a decline of PUE in GR; (3) changes in evapotranspiration and leaf dry matter content (LDMC) explained the variation of PUE in AB while changes of PUE in GR was mainly due to the alteration of soil water content and LDMC.

Conclusions

These results suggest that precipitation during the late growing season has a crucial influence on PUE, highlighting the importance of evapotranspiration and LDMC in regulating ecosystem productivity in the semi-arid steppe.