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Desert ecosystems possess an astonishing biodiversity and are rich in endangered species. This study investigated characteristics of species diversity and soil environmental factors in three major deserts of China's Alxa Plateau. The Alxa Desert included 183 plant species belonging to 109 genera and 35 families. The highest numbers of plant species belonged to the Compositae, Gramineae, and Chenopodiaceae families. The research area belongs to the semi-shrub and small semi-shrub deserts in temperate deserts. Species diversity was low, with the Shannon–Wiener index (H′) of shrub-herb = shrub > herb > tree. The Pielou evenness index (E) of shrub herb vegetation was the lowest, indicating more enriched species and fewer sparse species in the community, and that these types of vegetation had the characteristics of rich and obviously dominant species. Redundancy analysis (RDA) and correlations between the comprehensive plant community biodiversity index and soil factors indicated that soil-available phosphorus (NP), organic matter (SOM), and electrical conductivity (EC) had significant impacts on community species diversity. The herbaceous shrub community exhibited the highest H′, Simpson index (D), species richness index (S), soil moisture (SW), and soil nutrients. Planting Calligonum mongolicum, Ephedra membranacea, Artemisia annua, and Phragmites australis to form a typical desert shrub community for community diversity protection is recommended to effectively protect and restore desert ecosystems. [ABSTRACT FROM AUTHOR]

• Three ostracod species were identified and related ecological information are reported in the Badain Jaran Desert. • The node formation of Limnocythere inopinata is affected by a combination of the salinity and Ca2+ content of lake water. • The relationship between the percentage of noded individuals and salinity of lake water is complex. Limnocythere inopinata (Baird, 1843) is a widely distributed ostracod in modern non-marine waters and Quaternary sediments. Based on its morphological variation (the number and position of its nodes), different phenotypes have been identified. However, the factors controlling its morphological variation are currently open to debate, which hinders palaeoecological reconstructions based on this species. In this study, ostracod distribution and hydrochemical analyses of the ambient environment of 21 lakes in the Badain Jaran Desert were carried out. Three ostracod species belonging to two genera are identified as Limnocyhtere inopinata , Cypris cf. granulate and Cypris sp. with the dominant species L. inopinata represented by six phenotypes. The distribution features of these ostracods in the lakes and related ecological information are reported. In addition, the factors controlling the morphological variations of L. inopinata were analysed. Our data indicate that the noded individuals of L. inopinata prefer water with appropriate Ca2+ content (30–40 mg L−1) and low salinities (below 4.60 g L−1). The percentage of noded individuals of L. inopinata increases with increasing salinity only within a certain salinity range. Hence, caution should be exercised in reconstructions of palaeosalinity based on the morphological variability of L. inopinata. [ABSTRACT FROM AUTHOR]

Mega-dunes in the lake group area of the Badain Jaran Sand Sea, China, are generally taller than dunes in the non-lake group area. This spatial distribution of dune heights may provide a new perspective on the controversy regarding the dunes' formation mechanism. In this study, we calculated the relative heights and slopes of individual dunes based on a digital elevation model, and we confirmed the height distribution of abnormally tall dunes in the lake group area of the sand sea. It was also found that slopes of more than 10° in the lake group area are more common than those in the non-lake group area. Based on meteorological observations, coupled with the measurement of water content in the sand layers, we propose a conceptual model demonstrating that moisture exchange between the lakes and soil via non-rainfall water will humidify dune slopes and form a more favorable accumulation environment for aeolian sand, thus increasing dune heights. Although long-term observations are yet to be carried out, the present study can be used as evidence for understanding the basis of dune formation in the lake group area and assessing groundwater utilization in deserts. [ABSTRACT FROM AUTHOR]

The relationship between the variation of CO 2 flux and the pH of inorganic factors. [Display omitted] • The difference of CO 2 absorption and release is obvious during the day and night. • Yindeer Lake was a net sink of CO 2 during the study period. • The lakes can absorb large amounts of CO 2 every year to slow down global warming. • Meteorological factors controlling CO 2 fluxes differed by time scale. • pH is the main influencing factor controlling CO 2 absorption and release. Carbon sequestration levels in lakes are often underestimated despite being vital for the comprehensive analysis of CO 2 budget and significantly influencing inland lakes in arid areas. In this study, the eddy covariance (EC) technique was used to measure CO 2 flux for six consecutive years during 2012–2017 in a small salt-lake (Yindeer Lake) replenished by groundwater in southeastern Badain Jaran Desert, China. The results indicate that: (1) Yindeer Lake was a net sink of CO 2 , which led to the estimate that the lakes in the Badain Jaran Desert can absorb approximately 1.91 × 103 t of CO 2 per year and help slow down the rate of global warming. (2) The effects of meteorological factors on the CO 2 flux of the lake vary with timescales. (3) Inorganic processes, in which pH is the main influence mechanism, control CO 2 absorption and releases in Yindeer Lake. Thus, the study results provide a new guide for solving the "missing sink" problem. [ABSTRACT FROM AUTHOR]

Plant phenology is a commonly used indicator representing the impacts on vegetation by the climate and other environmental factors. The use of repeated digital photography provides an opportunity to conduct long-term monitoring of plant phenology and to extract phenological transition dates. Here, we tracked the phenological changes in the flowering tree, Elaeagnus angustifolia L., in the Cherigele (CRGL) of the Badain Jaran Desert (BJD) and the nearby Lianggejing (LGJ); using one-year near-surface digital repeat photography and meteorological data, the phenological difference between the two sites was revealed. We found that the use of digital cameras allowed for the monitoring of plant phenology with high temporal and spatial accuracy in these dryland ecosystems. Furthermore, in the lake group region of BJD, the onset of greening occurred 23 days earlier, the onset of dormancy began 13 days later and the growing season was 36 days longer, compared to those of the surrounding area. This difference is partly related to the higher altitude in the LGJ; however, it is dominantly related to the warm island effect in the lake group region. This effect resulted in the mean annual temperature in the CRGL being ~1.6 °C higher than in the LGJ. • This study fills the gap in phenological research using digital cameras in desert ecosystems in China. • The onset of greening was earlier, that of dormancy was later in the lake group region of BJD than in the surrounding area. • Phenological disparity between the two sites was mainly caused by the warm island effect in the lake group region of the BJD. [ABSTRACT FROM AUTHOR]

The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical features.