Diversity and community structure of ammonia oxidizing archaea in rhizosphere soil of four plant groups in Ebinur Lake Wetland

The aim of this study was to reveal the differences in the community structure of AOA between rhizosphere and non-rhizosphere soil, to provide a theoretical basis for further study on the relationship between halophyte rhizosphere soil microorganisms and salt tolerance. The results of diversity and community structure showed that the diversity of ammonia-oxidizing archaea community in rhizosphere soil of Reed was higher than that in non-rhizosphere soil in spring and lower than that in non-rhizosphere soil in summer and autumn; In summer, the diversity of rhizosphere soil was higher than that of non-rhizosphere soil of Karelinia caspica lower than that of non-rhizosphere soil in spring and autumn. The diversity of rhizosphere soil of Halocnemum strobilaceum in three seasons was lower than that in non-rhizosphere soil. The diversity of rhizosphere soil of Salicornia was higher than that in non-rhizosphere soil in three seasons. In addition, the relative abundance of AOA in rhizosphere soil of four plants was higher than that in non-rhizosphere soil. AOA community in all soil samples was mainly concentrated in Crenarchaeota and Thaumarchaeota. RDA results showed salinity (EC), soil water moisture (SM), pH and soil organic matter (SOM) were important factors affecting the differentiation of AOA communities.

Variability of Grain Size of Surface Sand on Nebkhas at the Southern Fringe of the Taklimakan Desert, China

Nebkha plays a major role in the ecological and environmental stabilization by accumulating wind-blown sediments around shrubs. Grain-size characteristics of different positions on nebkha reflect the sorting effect of aeolian dynamics. Based on the collected sand grains of different positions on four types of nebkhas at the southern fringe of Taklimakan Desert, China, this paper provided detailed insight into variability of the grain size of surface sand on nebkhas. The results showed that: a) Grain-size distributions on shield-shaped Karelinia caspica Nebkhas under natural condition had the larger spatial variability in comparison with the others. b) Grain size on nebkhas regularly showed the spatial variation. Grain size was increasingly larger along the windward slope upward, and then became finer along the leeward slope downward. c) The grain-size sortings of different positions on shield-shaped Alhagi sparsifolia Nebkhas under new reclaimed land were the best.

Leaf nitrogen allocation and partitioning in three groundwater-dependent herbaceous species in a hyper-arid desert region of north-western China

Groundwater-dependent vegetation (GDV) is useful as an indicator of watertable depth and water availability in north-western China. Nitrogen (N) is an essential limiting resource for growth of GDV. To elucidate how leaf N allocation and partitioning influence photosynthesis and photosynthetic N-use efficiency (PNUE), three typical GDV species were selected, and their photosynthesis, leaf N allocation and partitioning were investigated in the Taklamakan Desert. The results showed that Karelinia caspica (Pall.) Less. and Peganum harmala L. had lower leaf N content, and allocated a lower fraction of leaf N to photosynthesis. However, they were more efficient in photosynthetic N partitioning among photosynthetic components. They partitioned a higher fraction of the photosynthetic N to carboxylation and showed higher PNUE, whereas Alhagi sparsifolia Shap. partitioned a higher fraction of the photosynthetic N to light-harvesting components. For K. caspica and P. harmala, the higher fraction of leaf N was allocated to carboxylation and bioenergetics, which led to a higher maximum net photosynthetic rate, and therefore to a higher PNUE, water-use efficiency (WUE), respiration efficiency (RE) and so on. In the desert, N and water are limiting resources; K. caspica and P. harmala can benefit from the increased PNUE and WUE. These physiological advantages and their higher leaf-area ratio (LAR) may contribute to their higher resource-capture ability.