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Lake Group of Badain Jaran Desert and the recharge sources are hot issues in the academic community. The Mega Dune links the atmospheric precipitation and the lake water. Studying its hydrological characteristics could deepen the understanding of regional lake water cycle, while the plant distribution is an important indicator of the hydrological characteristics of the Mega Dune. This paper took the Tamarix laxa as the research object, measured the water content by drying method, analysed the spatial and temporal variation characteristics of the water content, then explored the indicative significance to the hydrological characteristics of the Mega Dune. The results showed: the soil profile of Tamarix laxa distribution area can be divided into moisture rapid change layer(0 to 60 cm), moisture active layer(60 to 120 cm) and moisture relatively stable layer(120 to 200 cm) according to its moisture characteristics, and the moisture content tends to decrease with increasing depth, and the average moisture content of rapid change layer is 1.69%, which is significantly higher than the other two layers. The water content of the distribution area is 95.83% in the range of 0.50% to 3.00% and the observed maximum value was 4.88%, all of them are less than the field water capacity(5.00%), which indicated that it was difficult to form gravity water in the Tamarix laxa distribution area at the leeward slope of the Mega Dune, but also indicated that the precipitation is difficult to quickly infiltrate to replenish lake water as gravity water for the leeward slope of the Mega Dune. The "arborization" growth characteristics of Tamarix laxa and its special distribution position are not only conducive to its root tiller propagation, but also to the storage and maintenance of water, which maintains its survival and development. [ABSTRACT FROM AUTHOR]

It is of great significance to study the effects of precipitation events on carbon exchange in the ecosystem for an accurate understanding of the carbon cycle. However, the response of net ecosystem CO2 exchange (NEE) in the desert to precipitation events is elusive. In this study, the NEE in response to precipitation events of varying intensities in the Badain Jaran Desert (BJD) in China was continuously monitored using the eddy covariance (EC) technique. The following results were obtained: (1) The BJD ecosystem was a net CO2 sink throughout the study period, with NEE values of -113.4, -130.7, and -175.4 g C m-2a-1 in 2016, 2018, and 2019, respectively. The total precipitation yielded a higher carbon sequestration capacity in 2019 than in the other two years. In addition, the intensity, time, and frequency of precipitation had significant impacts on CO2; (2) the threshold value of the NEE response to precipitation was ~1.4 mm, indicating the extreme sensitivity of the BJD to precipitation events; (3) the variations in the NEE response to precipitation events conformed to a dual exponential model. The analytical results of the model indicate that precipitation intensity was positively correlated with the carbon sequestration capacity of the desert. The model revealed that the greater the precipitation intensity, the longer it takes the NEE to reach the maximum, and the lengthier the duration of the residual effects. With an increase in the total precipitation and frequency of extreme precipitation events under warm and humidification climates, the carbon sequestration capacity of the BJD will likely be enhanced. The results of this study are of great significance for revealing the carbon cycle mechanism of the desert ecosystem. [ABSTRACT FROM AUTHOR]

The Alxa Desert in north-central China has a unique landscape that contains hundreds of lakes and the highest sand dunes in the world. To date, however, the explanation of the water source in this desert is still controversial. In this paper, continuous hydrometeorological observations, including precipitation, evaporation, water level and temperature, in the interior of the Alxa Desert are presented and the water balance of a typical desert lake is calculated. The moisture, Cl − concentration, δ 2 H and δ 18 O of several sand profiles, the hydrogeochemical characteristics of some lakes and groundwater, and the elemental composition of some travertine samples are analyzed to investigate the rainfall percolation and groundwater recharge. The results showed that local precipitation is not the major replenishment source of the lakes and groundwater in the Alxa Desert. It is supposed that the groundwater from deep strata in the adjacent fracture zone might recharge the desert lake group from the southeast along an altitudinal gradient. [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 Badain Jaran Desert (BJD) is characterized by the coexistence of over 110 perennial lakes and thousands of megadunes in its southeast part. Unlike the cold island effect, we found a special phenomenon of the warm island effect in the lake group region of the BJD. However, the concept and formation mechanism remains unclear. In this study, based on observations of land surface processes in the area, we first used the daily mean temperature from 23 automated meteorological stations from 2010 to 2017 to calculate the mean daily temperature (T) ≥ 0 °C, T ≥ 10 °C accumulated temperature and negative accumulated temperature. Furthermore, using the net radiation from two eddy covariance measurement systems, characteristics of the net radiation between the lake and megadunes were analyzed. When comparing observed data in the lake group region to surrounding areas, accumulated temperature from all three meteorological stations in the lake group region were higher; the duration days of T ≥ 0 °C and T ≥ 10 °C were longer, whereas duration days of negative accumulated temperature were shorter. In addition, the initial dates for T ≥ 0 °C and T ≥ 10 °C accumulated temperature were earlier, whereas the end dates were delayed. Variations in heat were observed between stations in the lake group region that may be reflective of microclimate environments between lakes. The authors relate warm island formation in the BJD lake group region to (1) the heat carried by groundwater recharge to the desert lake groups has a great impact on the local temperature. (2) Net heat radiation to the atmosphere through sensible heat flux owing to sparse vegetation in the desert areas. Hence, heat resources are richer in the lake group region. This study aims to improve our understanding of the warm island effect from a comprehensive analysis of its intensity and distribution pattern around the lake group region as compared to its surroundings. In addition, the results from this study will provide a scientific basis for determining the source of lake water in the BJD. [ABSTRACT FROM AUTHOR]