Ecological Indicators (Oct 2022)
Effect of simulated precipitation regimes on sap flow and water use efficiency for xerophytic Caragana korshinskii
Abstract
Precipitation variation under global climate change condition exacerbates the challenges in vegetation restoration and management in arid and semiarid regions. The response of plant water use to precipitation variation is not well understood for Caragana korshinskii, a kind of dominant xerophytic shrub species that is widely cultivated on the Chinese Loess Plateau for soil and conservation. Thus, we investigated the response of sap flow (SF) in C. korshinskii to the rainout-shelter simulated precipitation regimes: 30% precipitation reduction (P-30%), control (CK), and 30% precipitation increase (P+30%), during the growing seasons (April–October) in 2019 and 2020. The average soil water content (SWC, 0–80 cm) in P+30% significantly increased by 13.6–57.9% than that in CK and P-30% on both years. There were no significant differences in canopy transpiration (Tc), water use efficiency (WUE), and stem morphological characteristics (except for basal area increment) among the three precipitation regimes in 2019. However, in 2020, the P+30% treatment promoted greater increase in stem length, stem basal area, and biomass than CK and P-30%. The average Tc in P+30% (2.3 mm d–1) was 0.2- and 1.9-fold greater than that in CK (1.9 mm d–1) and P-30% (0.8 mm d–1), respectively. The average WUE in P+30% (3.7 kg m−3) was 19.4% and 60.9% greater than that in CK (3.1 kg m−3) and P-30% (2.3 kg m−3), respectively. Solar radiation (Rs), soil temperature (Ts), variable of transpiration (VT), reference evapotranspiration (ET0), air temperature (Ta) and SWC were the key environmental factors controlling SF. The structural equation model further showed that, with increasing precipitation gradient, the effect of SWC on SF diminished, while the influences of Ta and ET0 on SF gradually increased. These results indicated that increasing precipitation by 30% can promote rejuvenation, increase transpiration and water use efficiency in C. korshinskii, which is essential for interpreting the key ecohydrological processes of xerophytic shrubs under precipitation varying conditions in similar dry regions.
