Aims West Ordos Desert (WOD) in Inner Mongolia of China is characterized by unique geographical and ecological features to avoid the direct invasion of Quaternary Continental Glaciation, so it hosts many endangered relic species such as Tetraena mongolica, Ammopiptanthus mongolicus and Potaninia mongolica from Tertiary. However, how these plants utilize available water sources remains unknown. The objective of this study was to investigate the water utilization strategies of selected rare and endangered plant species in WOD by comparing hydrogen isotope ratios between their xylem water and possible water sources following four rainfall events of varying-intensities.
Methods We measured the hydrogen isotope ratios of xylem water from T. mongolica, A. mongolicus and P. mongolica and an accompanying species Sarcozygium xanthoxylum and potential water sources (including precipitation and soil water in different soil layers from 0 to 150cm) over 9 days following each of four varying-intensity rainfall events during the summer of 2012. And then calculated the percentage utilization of potential water sources by each species after each rainfall events using the linear mixing model. We also made the measurements of soil moisture and root biomass in favor of interpretation of plant water use strategies.
Important findings Tetraena mongolica, A. mongolicus and S. xanthoxylum primarily relied on deep soil water, whereas P. mongolica depended predominantly on rainwater. These rare and endangered desert plants had differential utilizations of available water sources, so some competition for limited water existed among some species. Tetraena mongolica had a competitive relationship in absorption of soil moisture with the same family species S. xanthoxylum, suggesting that T. mongolica and S. xanthoxylum should be restored separately at different areas in the WOD. Overall, this study provides a better understanding of water use strategies of these four plants and scientific evidence for protecting rare and endangered plants, maintaining regional species diversity, and developing effective vegetation restoration plans in the WOD.