Search

• 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]

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]

• New methods to quantitatively reconstruct consecutive lake level changes in desert. • The highest lake levels occurred at the early Holocene in BJD hinterland. • Increase in meltwater resulted in high lake levels during the early Holocene. Quantitative reconstruction of consecutive paleolake-level fluctuations may help reconstruct lake evolution during the Holocene. However, the reconstruction of a groundwater recharged lake in a desert hinterland is challenging. In this study, 23 samples of lake bottom sediments were obtained from eight groundwater recharged lakes in the hinterland of the Badian Jaran Desert in northwest China to establish models between the grain size component and lake level. Our results showed that the four grain size components of the sediments could be separated using the Weibull function. The first two fine grain components (W1 and W2) were deposited in the atmospheric dust. The two coarser components (W3 and W4) could be interpreted as sediments transported by wind from the surrounding sand dunes, while W3 was subsequently redistributed by lake waves. Changes in the lake water depth could be expressed by the W1 and W2 component contents, as well as the modal size of W3. Using the above models, unmixing grain size components of the lake sediment obtained from the ZZH section located in a seasonal lake (Zhunzhahan Jaran Lake) in the desert hinterland were used to quantitatively reconstruct the lake-level fluctuations during the Holocene. The lake level frequently fluctuated between 3.82 and 9.21 m during 10.6–8.6 cal kyr BP, slightly fluctuated between 3.41 and 5.26 m during 8.6–4.7 cal kyr BP, and markedly declined from 6.09 m to 4.46 m during 4.7–3.5 cal kyr BP. Lake-level changes in the hinterland of the Badian Jaran Desert did not correspond to the effective moisture changes during the early Holocene. Instead, the rise in lake level during the early Holocene would have resulted from the input of groundwater from the meltwater in the mountains of the recharge area. The data reveal new methods for quantitatively reconstructing consecutive paleolake-level fluctuations by groundwater recharged lakes in the desert hinterland. [ABSTRACT FROM AUTHOR]