The Stem Sap Flow and Water Sources for Tamarix ramosissima in an Artificial Shelterbelt With a Deep Groundwater Table in Northwest China.

Feiyao Liu,Quangang You,Jing Pan,Xian Xue,Cuihua Huang,Xiaojie Chen,Shaoxiu Ma,Fei Peng,Yaofang Shi

doi:10.3389/fpls.2022.794084

Abstract

The shelterbelt forest between oases and the desert plays a vital role in preventing aeolian disasters and desertification in arid regions of northwest China. Tamarix ramosissima (T. ramosissima), a typical perennial and native xerophyte shrub in Northwest China, grows naturally and is widely used in building artificial shelterbelt forests. The balance between water consumption and the availability of water determines the survival and growth of T. ramosissima. How T. ramosissima copes with extremely low rainfall and a deep groundwater table remains unknown. To answer this, the transpiration and the water sources of T. ramosissima were investigated by the heat balance and oxygen isotopic analysis method, respectively. Our results show that the daily T. ramosissima stem sap flow (SSF) was positively correlated with air temperature (Ta), photosynthetically active radiation (PAR), and the vapor pressure deficit (VPD). We found no significant relationship between the daily SSF and soil moisture in shallow (0–40 cm) and middle (40–160 cm) soil layers. Oxygen isotope results showed that T. ramosissima mainly sources (>90%) water from deep soil moisture (160–400 cm) and groundwater (910 cm). Diurnally, T. ramosissima SSF showed a hysteresis response to variations in PAR, Ta, and VPD, which suggests that transpiration suffers increasingly from water stress with increasing PAR, Ta, and VPD. Our results indicate that PAR, Ta, and VPD are the dominant factors that control T. ramosissima SSF, not precipitation and shallow soil moisture. Deep soil water and groundwater are the primary sources for T. ramosissima in this extremely water-limited environment. These results provide information that is essential for proper water resource management during vegetation restoration and ecological reafforestation in water-limited regions.

Highlights

Aeolian disasters in arid regions are a major hazard to crop production and human life (Lei et al, 2003; Dong, 2004; Wang et al, 2011)
We focus on the capacity of T. ramosissima for groundwater uptake, which has been neglected in previous studies
We found that the precipitation events with less than 5 mm of rainfall did not strongly affect soil moisture

Summary

Introduction

Aeolian disasters in arid regions are a major hazard to crop production and human life (Lei et al, 2003; Dong, 2004; Wang et al, 2011). Shelterbelt forests play an important role in weakening wind erosion, reducing sand sediment, and preventing aeolian desertification (Ryszkowski and Kedziora, 2007). The large water deficit in arid regions and the urgency with which environmental protection is required make it challenging to allocate the scarce water resources for socioeconomic development without compromising the health of the ecosystem (Wang et al, 2017). Recent studies have demonstrated that soil water and groundwater have been strongly affected by the large-scale artificial shelterbelt forest creation, which has driven changes in evapotranspiration and infiltration (Wang et al, 2010; Jia and Shao, 2014; Jia et al, 2017) in the arid region and which may cause the further degradation of oasis shelterbelts (Fu et al, 2016)

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