DOI: 10.5061/dryad.hqbzkh1pp
title: Effect of changing precipitation in different periods on precipitation use efficiency in a semi-arid grassland

description: 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. 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. 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 0.09g 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.
 These results suggest that precipitation during the late growing season
 has a crucial influence on PUE, highlighting the importance of
 evapotranspiration and leaf dry matter content in regulating ecosystem
 productivity in the semi-arid steppe.
description: The experiment was conducted on April 15th of 2015 with a
 completely randomized block design. The experiment had seven treatments,
 including control (C), a 60% decrease in precipitation during the early
 growing season (from April to June, DEP), late growing season (from July
 to September, DLP), and whole growing season (from
 April to September, DWP), a 60% increase in
 precipitation during the early growing season (from April to June, IEP),
 late growing season (from July to September, ILP), and whole growing
 season (from April to September, IWP).
description: We classified the plants by species and then dried them at 65°C until they
 reached a constant weight. We chose 34 common species, which accounted for
 more than 95% of the above-ground biomass, for trait measurements at the
 flowering time from July 1st first to August 20th in 2018 to measure plant
 functional trait. There were three replicates per species.
 Evapotranspiration was measured using LI-6400 Portable Photosynthesis
 System (Li-Cor Inc, Lincoln, NE, USA), which connected to a transparent
 chamber (0.5m x 0.5m x 0.5 m) three times a month. The transparent chamber
 was placed on a permanent aluminum frame (0.5 m x 0.5 m), which inserted
 into the soil with a depth of 3 cm. There were two fans inside the chamber
 running continuously to mix the air during measurements. The water flux
 was recorded every 10 seconds during 90 seconds. ET was calculated based
 on the time courses of water flux. In mid-September of each year, two 20
 cm soil cores were drilled using a 7cm soil auger, and the soil sample
 from two holes were mixed in each sub-plot. The roots and gravel were
 sifted out with a 2 mm sieve. The physical and chemical indexes, including
 nitrate nitrogen (NO3-N), dissolved organic carbon (DOC), and soil water
 content (SWC) were measured.