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Oxygen (O 2 ) availability within the sediment–root interface is critical to the survival of macrophytes in O 2 -deficient sediment; however, our knowledge of the fine-scale impact of macrophyte roots upon the spatiotemporal dynamics of O 2 is relatively limited. In this study, a no n -invasive imaging technology was utilized to map O 2 micro-distribution around Vallisneria spiralis. Long-term imaging results gathered during a 36 day-period revealed an abundance of O 2 spatiotemporal patterns ranging from 0 to 250 μmol L − 1 . The root-induced O 2 leakage and consequent oxygenated area were stronger in the vicinity of the basal root compared to that found in the root tip. The O 2 images revealed V. spiralis exhibited radial O 2 loss (ROL) along the entire root, and the O 2 distribution along the root length showed a high degree of small-scale spatial heterogeneity decreasing from 80% at the basal root surface to 10% at the root tip. The oxygenated zone area around the roots increased as O 2 levels increased with root growth and irradiance intensities ranging from 0 to 216 μmol photons m − 2 s − 1 . A weak ROL measuring < 20% air saturation around the basal root surface was maintained in darkness, which was presumably attributed to the O 2 supply from overlying water via plant aerenchyma. The estimated total O 2 release to the rhizosphere of V. spiralis was determined to range from 8.80 ± 7.32 to 30.34 ± 17.71 nmol m − 2 s − 1 , which is much higher than many other macrophyte species. This O 2 release may be an important contribution to the high-capacity of V. spiralis for quickly colonizing anaerobic sediment. [ABSTRACT FROM AUTHOR]

Abstract In the context of global precipitation anomalies and climate warming, the evolution of fragile desert ecosystems, which account for one-third of the world's land area, will become more complex. Studies of regional climate change and ecosystem response are important components of global climate change research, especially in arid desert regions. Zygophyllum xanthoxylum and Ammopiptanthus mongolicus are two dominant but endangered shrub species in the Alxa Desert in the arid region of central Asia. Using dendrochronological methods, we studied the response of radial growth of those two species to climate factors, and the adaptability of the two shrub populations under a regional warming trend. We found that radial growth of both shrubs was mainly affected by precipitation during the growing season. In additionally, along with the decrease of precipitation and the increase of temperature from east to west of Alxa desert Plateau, the limiting effect of drought during the growing season on radial growth increased. The climate response characteristics and changes between dry and wet periods exhibited spatial and temporal heterogeneity due to micro-level geomorphological factors. Under a regional climate warming trend, individual growth and population development of the two endangered shrubs will be adversely affected. In areas where these species are naturally distributed, populations will gradually become concentrated in micro-geomorphic regions with better soil moisture conditions, such as low-lying areas in the gullies that develop in alluvial fans. This finding has important scientific significance for understanding the development of the region's dominant shrub populations and protection of these and other endangered plants in arid desert areas. Graphical abstract Unlabelled Image Highlights • Radial growth of two co-occurring desert shrubs, Z. xanthoxylum and A. mongolicus , was mainly affected by precipitation. • The climate response characteristics and changes between dry and wet periods exhibited spatial and temporal heterogeneity. • Under climate change, the desert shrub populations will concentrated in better moisture micro-geomorphic regions. [ABSTRACT FROM AUTHOR]