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1. chinaXiv:202004.00042 [pdf]

Stable oxygen-hydrogen isotopes reveal water use strategies of Tamarix taklamakanensis in the Taklimakan Desert, China

DONG Zhengwu; LI Shengyu; ZHAO Ying; LEI Jiaqiang; WANG Yongdong; LI Congjuan
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Tamarix taklamakanensis, a dominant species in the Taklimakan Desert of China, plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability. This study aimed to determine the water use strategies of T. taklamakanensis in the Taklimakan Desert under a falling groundwater depth. Four typical T. taklamakanensis nabkha habitats (sandy desert of Tazhong site, saline desert-alluvial plain of Qiemo site, desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site) were selected with different climate, soil, groundwater and plant cover conditions. Stable isotope values of hydrogen and oxygen were measured for plant xylem water, soil water (soil depths within 0–500 cm), snowmelt water and groundwater in the different habitats. Four potential water sources for T. taklamakanensis, defined as shallow, middle and deep soil water, as well as groundwater, were investigated using a Bayesian isotope mixing model. It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation, but through the river runoff from snowmelt water in the nearby mountain ranges. The surface soil water content was quickly depleted by strong evaporation, groundwater depth was relatively shallow and the height of T. taklamakanensis nabkha was relatively low, thus T. taklamakanensis primarily utilized the middle (23%±1%) and deep (31%±5%) soil water and groundwater (36%±2%) within the sandy desert habitat. T. taklamakanensis mainly used the deep soil water (55%±4%) and a small amount of groundwater (25%±2%) within the saline desert-alluvial plain habitat, where the soil water content was relatively high and the groundwater depth was shallow. In contrast, within the desert-oasis ecotone in the Qira and Aral sites, T. taklamakanensis primarily utilized the deep soil water (35%±1% and 38%±2%, respectively) and may also use groundwater because the height of T. taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low, which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities. Consequently, T. taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources (deep soil water and groundwater), reflecting its adaptations to the different habitats in the arid desert environment. These findings improve our understanding on determining the water sources and water use strategies of T. taklamakanensis in the Taklimakan Desert.

submitted time 2020-04-23 From cooperative journals:《Journal of Arid Land》 Hits221Downloads119 Comment 0

2. chinaXiv:202004.00044 [pdf]

Challenges for the sustainable use of water and land resources under a changing climate and increasing salinization in the Jizzakh irrigation zone of Uzbekistan

Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Jizzakh Province in Uzbekistan is one of the largest irrigated areas in Central Asia without natural drainage. In combination with aridity, climate change and extensive irrigation practices, this has led to the widespread salinization of agricultural land. The aim of this study was to identify opportunities to improve the reclamation status of the irrigated area and how best to effectively use the water resources in Jizzakh Province based on investigations conducted between 1995 and 2016. A database of field measurements of groundwater levels, mineralization and soil salinity conducted by the provincial Hydro-Geological Reclamation Expeditions was used in the study. The total groundwater mineralization was determined using a portable electric conductometer (Progress 1T) and the chloride concentration was determined using the Mohr method. The soil salinity analyses were conducted by applying two different methods: (1) the extraction and assessment of the soluble salt content, and (2) using an SM-138 conductivity sensor applied to a 1:1 mixture of soil sample and water. The analyses of the monitoring results and the salt balance in the "irrigation water–soil–drainage water" system clearly demonstrated that the condition of the irrigated land in the province was not significantly improved. Under these conditions, the stability of crop yields is achieved mainly through the use of large volumes of fertilizer. However, excess amounts of mineral fertilizers can also cause the salinization of soils. The average groundwater salinization value in most of the irrigated land (75.3%) fluctuated between 1.1 and 5.0 g/L, while the values were less than 1.0 g/L in 13.1% of the land and in the range of 5.1–10.0 g/L in 10.5% of the land. During the period of 1995–2016 the salinization level of the irrigated land in Jizzakh Province increased slightly and the area could be divided into the following classes: no salinity (17.7% of the total area), low salinity (51.3%), moderate salinity (29.0%), and high salinity (2.0%). Detailed studies of the salt balance in irrigated land, the impact of climate change, increased fertilizer use, and repeated remediation leaching on the groundwater level and mineralization should be conducted in the future, due to the possibility of accelerated salinization, fertility decline, and reduced yields of agricultural crops.

submitted time 2020-04-23 From cooperative journals:《Journal of Arid Land》 Hits222Downloads124 Comment 0

3. chinaXiv:202004.00049 [pdf]

Crop production changes and the impact of Grain for Green program in the Loess Plateau of China

LYU Changhe; XU Zhiyuan
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Since the Grain for Green (GFG) program was implemented in 1999, most steeply sloping farmlands in the Loess Plateau of China have been returned to forestland and grassland. To understand its impact on the food production, this study analyzed the spatiotemporal changes of food crop production (FCP) in the plateau and quantified the contribution of sown area and yield changes to the total FCP during 1998–2014 using factor decomposition models, and then discussed the impact of GFG program on the FCP based on literature data. With the implementation of GFG program, total sown area in the Loess Plateau quickly deceased by 17.3% from 1998 to 2003, and then gradually restored to 1.03×107 hm2 in 2010. Thereafter, it slightly decreased to 1.02×107 hm2 (94.6% of the area in 1998) in 2014. By contrast, total FCP generally showed an apparent growth trend, averagely increased by 1.71% per year in the whole plateau during 1998–2014. This increase was jointly contributed by the improved yield of individual crops, and the adjustment of cropping structure, i.e., the expansion of high yield maize crop. The factor decomposition analysis results indicate that the sown area shrinkage only reduced the growth rate of total FCP by 0.29% per year during 1998–2014, although a significant impact was found for the early stage of 1999–2003. The results suggest that the implementation of GFG program would not induce an obvious risk of the food security. Therefore, it is suggested that the GFG program should be set as a long-term strategic policy, by not only supporting the conversion of slope farmlands, but also helping local farmers to seek sustainable ways of land use to improve the income and livelihood. It can be combined with the poverty eradication program, to simultaneously achieve the national goals of ecological civilization building and the livelihood improvement of rural people in the Loess Plateau. Considering rainfall limitation, the conversion of slope farmlands should be prioritized to grasslands.

submitted time 2020-04-23 From cooperative journals:《Journal of Arid Land》 Hits154Downloads85 Comment 0

4. chinaXiv:202004.00051 [pdf]

Uncertainty assessment of potential evapotranspiration in arid areas, as estimated by the Penman-Monteith method

HUA Ding; HAO Xingming; ZHANG Ying; QIN Jingxiu
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

The Penman-Monteith (PM) method is the most widely used technique to estimate potential worldwide evapotranspiration. However, current research shows that there may be significant errors in the application of this method in arid areas, although questions remain as to the degree of this estimation error and how different surface conditions may affect the estimation error. To address these issues, we evaluated the uncertainty of the PM method under different underlying conditions in an arid area of Northwest China by analyzing data from 84 meteorological stations and various Moderate Resolution Imaging Spectroradiometer (MODIS) products, including land surface temperature and surface albedo. First, we found that when the PM method used air temperature to calculate the slope of the saturation vapor pressure curve, it significantly overestimated the potential evapotranspiration; the mean annual and July–August overestimation was 83.9 and 36.7 mm, respectively. Second, the PM method usually set the surface albedo to a fixed value, which led to the potential evapotranspiration being underestimated; the mean annual underestimation was 27.5 mm, while the overestimation for July to August was 5.3 mm. Third, the PM method significantly overestimated the potential evapotranspiration in the arid area. This difference in estimation was closely related to the underlying surface conditions. For the entire arid zone, the PM method overestimated the potential evapotranspiration by 33.7 mm per year, with an overestimation of 29.0 mm from July to August. The most significant overestimation was evident in the mountainous and plain non-vegetation areas, in which the annual mean overestimation reached 5% and 10%, respectively; during July, there was an estimation of 10% and 20%, respectively. Although the annual evapotranspiration of the plains with better vegetation coverage was slightly underestimated, overestimation still occurred in July and August, with a mean overestimation of approximately 5%. In order to estimate potential evapotranspiration in the arid zone, it is important that we identify a reasonable parameter with which to calibrate the PM formula, such as the slope of the saturation vapor pressure curve, and the surface albedo. We recommend that some parameters must be corrected when using PM in order to estimate potential evapotranspiration in arid regions.

submitted time 2020-04-23 From cooperative journals:《Journal of Arid Land》 Hits150Downloads85 Comment 0

5. chinaXiv:202004.00052 [pdf]

Effect of the W-beam central guardrails on wind-blown sand deposition on desert expressways in sandy regions

WANG Cui; LI Shengyu; LEI Jiaqiang; LI Zhinong; CHEN Jie
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Many desert expressways are affected by the deposition of the wind-blown sand, which might block the movement of vehicles or cause accidents. W-beam central guardrails, which are used to improve the safety of desert expressways, are thought to influence the deposition of the wind-blown sand, but this has yet not to be studied adequately. To address this issue, we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow, the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions. The subgrade model is 3.5 cm high and 80.0 cm wide, with a bank slope ratio of 1:3. The W-beam central guardrails model is 3.7 cm high, which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column. The wind velocity was measured by using pitot-static tubes placed at nine different heights (1, 2, 3, 5, 7, 10, 15, 30 and 50 cm) above the floor of the chamber. The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler, which was sectioned into 20 intervals. In addition, we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016, by using a customized 78-cm-high gradient sand sampler for the sand flux structure test. Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade, and the wind velocity on the leeward side weakens significantly. The W-beam central guardrails decrease the leeward wind velocity, whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails. The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails. At 0.0H and 0.5H (where H=3.5 cm, which is the height of the subgrade), the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails, and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface. The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height. The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points, which is consistent with the position of the minimum wind velocity in the wind tunnel test. The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.

submitted time 2020-04-23 From cooperative journals:《Journal of Arid Land》 Hits133Downloads84 Comment 0

6. chinaXiv:202002.00081 [pdf]

SARS-coronavirus-2 nsp13 possesses NTPase and RNA helicase activities

Shu, Ting; Huang, Muhan; Wu, Di; Ren, Yujie; Zhang, Xueyi; Han, Yang; Mu, Jingfang; Wang, Ruibing; Qiu, Yang; Zhang, Ding-Yu; Zhou, Xi
Subjects: Biology >> Virology

The ongoing outbreak of Coronavirus Disease 2019 (COVID-19) has become a global pandemic and crisis. SARS-coronavirus-2 (SARS-CoV-2), the causative pathogen of COVID-19, is a positive-sense single-stranded RNA virus belonging to the family Coronaviridae. For RNA viruses, virus-encoded RNA helicases have long been recognized to play pivotal roles during viral life cycles by facilitating the correct folding and replication of viral RNAs. Here, our studies show that SARS-CoV-2-encoded nonstructural protein 13 (nsp13) possesses the nucleoside triphosphate hydrolase (NTPase) and RNA helicase activities that can hydrolyze all types of NTPs and unwind RNA helices dependently of the presence of NTP, and further characterize the biochemical characteristics of these two enzymatic activities associated with SARS-CoV-2 nsp13. Moreover, we found that some bismuth salts could effectively inhibit both the NTPase and RNA helicase activities of SARS-CoV-2 nsp13 in a dose-dependent manner. Thus, our findings demonstrate the NTPase and helicase activities of SARS-CoV-2 nsp13, which may play an important role in SARS-CoV-2 replication and serve as a target for antivirals.

submitted time 2020-04-19 Hits12034Downloads1005 Comment 0

7. chinaXiv:202004.00001 [pdf]

Reappraisal of Serridentinus gobiensis Osborn & Granger?and Miomastodon tongxinensis Chen:the validity of Miomastodon

WANG Shi-Qi; ZHANG Xiao-Xiao; LI Chun-Xiao?
Subjects: Biology >> Zoology

The elephantimorph proboscideans, Serridentinus gobiensis Osborn & Granger, 1932, and Miomastodon tongxinensis Chen, 1978, from the Middle Miocene of northern China, were revised as Zygolophodon gobiensis (Osborn & Granger, 1932). However, their phylogenetic positions are still being debated because of their intermediate morphology between the typical bunodont (Gomphotheriidae) and zygodont (Mammutidae) elephantimorphs. In the present paper, we compare their dental and mandibular morphology with that of the Eurasian Z. turicensis, Gomphotherium subtapiroideum, and G. tassyi, as well as the North American Mio. merriami and G. productum. It appears that S. gobiensis and Mio. tongxinensis share with Mio. merriami the slightly more bunodont molar morphology than that of Z. turicensis, e.g., the thicker enamel, thicker pretrite crescentoids, higher interlophid enamel pillars in buccal view, and the narrower contour majorly caused by the narrower posttrite half loph(id)s. S. gobiensis and Mio. merriami also possess an “erected oval cross-sectioned mandibular tusk”, in which the cross-section is mediolaterally compressed (dorsoventral diameter being larger than the mediolateral one). Whereas, in Z. turicensis and G. productum, the mandibular tusk is “laid oval cross-sectioned”, in which the cross-section is dorsoventrally compressed (dorsoventral diameter is smaller than the mediolateral one). Therefore, it is reasonable to revive the genus Miomastodon Osborn, 1922, which contains the species that were previously attributed to Zygolophodon, but they have relatively bunodont molar morphology (i.e., the robust type of the Z. turicensis group). The mandibular tusk with erected?oval cross-section seems to be a synapomorphy of Miomastodon species. Furthermore, the molar morphology of G. subtapiroideum and G. tassyi also exhibits intermediate status between the typical bunodonts and zygodonts. However, the mandibular symphysis of G. subtapiroideum and G. tassyi is stronger than that of Miomastodon, and the mandibular tusk is pyriform cross-sectioned. The validity of Miomastodon and G. subtapiroideum/tassyi obscures the boundary between the Gomphotheriidae and Mammutidae, and suggests that the evolutions of the Gomphotheriidae and?Mammutidae are deeply involved in with each other, rather than straightforwardly detached. This phenomenon has been revealed by a collagen sequence analysis among Notiomastodon, Mammut, and extant elephants, which should be further studied.

submitted time 2020-03-31 From cooperative journals:《古脊椎动物学报》 Hits4295Downloads391 Comment 0

8. chinaXiv:202004.00002 [pdf]

New material of Cervidae (Artiodactyla, Mammalia) from?Xinyaozi Ravine in Shanxi, North China

DONG Wei; BAI Wei-Peng; PAN Yue; LIU Wen-Hui
Subjects: Biology >> Zoology

Many cervid specimens were uncovered during the field exploration for Nihewan beds?at the beginning of the 1980s from Taijiaping, Shuichongkou and Dazhuangke localities along?Xinyaozi Ravine at Nangaoya Township of Tianzhen County, Shanxi Province in North China.?Recent studies on the cervid material identified seven species of Cervidae in total: Muntiacus?bohlini, Cervavitus cf. C. huadeensis, Axis shansius, Nipponicervus elegans, Elaphurus?davidianus predavidianus, E. bifurcatus from the Early Pleistocene deposits at Taijiaping and?Shuichongkou localities, and Cervus (Elaphus) elaphus from uncertain horizon at Dazhuangke. At?least the previous six species of cervids were from Nihewan Formation (Nihewanian or equivalent?to European middle and late Villafranchian), i.e. the Early Pleistocene, in Sangganhe Basin area.Cervavitus cf. C. huadeensis and A. shansius were survivors from the Late Neogene; M. bohlini,N. elegans, E. davidianus predavidianus and E. bifurcatus are new forms of the Early Pleistocene.If Dazhuangke horizon can be dated as those of Shuichongkou and Taijiaping localities, the appearance of elaphoid cervids could be traced back to the Early Pleistocene, and the evolution of?elaphoid antler would start from absence to presence of bez tine. The presence of Elaphurus and?Nipponicervus in mainland China and Japanese archipelago implies further that the sea level was?dropped down that these cervids could migrate from the mainland to the islands. The abundance?of folivorous cervid specimens in the Xinyaozi Ravine area indicates the existence of a certain?scale of forested environment in Sangganhe Basin area during the Early Pleistocene.

submitted time 2020-03-31 From cooperative journals:《古脊椎动物学报》 Hits3809Downloads332 Comment 0

9. chinaXiv:202004.00003 [pdf]

A new species of Amynodontopsis (Perissodactyla:?Amynodontidae) from the Middle Eocene of Jiyuan,?Henan, China

WANG Xiao-Yang; WANG Yuan-Qing; ZHANG Rui; ZHANG Zhong-Hui; ?LIU Xiao-Ling; REN Li-Ping
Subjects: Biology >> Zoology

An adult amynodont skull, collected from the Middle Eocene Niezhuang Formation of Jiyuan Basin (Henan, China), is recognized as a new species Amynodontopsis jiyuanensis sp. nov. The specimen possesses the typical features of the genus Amynodontopsis, such as a dolichocephalic skull with elevated roof, premaxilla-nasal contact, large preorbital fossa extending posteriorly medial to the orbit, inner surface of anterior orbital bar concave in continuation with the preorbital fossa, antecrochet usually presented on M1, and metastyle of M3 strongly deflected labially. A. jiyuanensis is diagnosed by a combination of the following characters: long nasals, nasal process of premaxilla extending far back laterally below the nasal and excluding the maxilla from the border of external nares, nasal notch above the post-canine diastema, more transverse and proportionally longer protoloph and metaloph on upper molars. Comparison with known species of Amynodontopsis indicates that it is the most primitive one in the genus, due to the possession of primitive characters. Associated fossil mammals support a correlation of the strata bearing A. jiyuanensis with the Shara Murun Formation of the Erlian Basin, Nei Mongol, China, namely the Middle Eocene Sharamurunian Asian Land Mammal Age (ALMA), prior to all other known Amynodontopsis species. The earlier geologic age and primitive morphological features of A. jiyuanensis suggest that Amynodontopsis has an Asian origin in the Middle Eocene and later immigrated into North America.

submitted time 2020-03-31 From cooperative journals:《古脊椎动物学报》 Hits3987Downloads331 Comment 0

10. chinaXiv:202003.00051 [pdf]

Followup ground-based observations of the dwarf nova KZ Gem

Zhibin Dai; Paula Szkody; John R. Thorstensen; N. Indika Medagangoda
Subjects: Astronomy >> Astrophysics

We present spectroscopy of stars in the immediate vicinity of the dwarf nova (DN) KZ Gem to confirm its identification, which had been ambiguous in the literature. Analysis of 73 radial velocities spanning from 2014 to 2019 provides a high-precision orbital period of 0.2224628(2) d (~5.34 hr) and shows KZ Gem to be a double-lined DN. Time series photometry taken from 2016 to 2018 shows a variable double-hump modulation with a full amplitude of ~0.3 mag, along with five Gaussian-like transient events lasting ~30 min or more. Using the light curve code XRBinary and nonlinear fitting code NMfit, we obtain an optimized binary model of the dwarf nova (DN) KZ Gem, from time series photometry, consisting of a Roche-lobe-filling K type dwarf with a mass transfer rate of 2.7 - 7.9 x 10^{-10} solar mass per yr to a large, cool and thick disk surrounding a white dwarf, in an orbit with an inclination of 51.6(+/-1.4) degree. Two hotspots on the disk are demonstrated to cause the observed variations in the ellipsoidal modulations from the secondary star. This physical model is compatible with the Gaia distance of KZ Gem.

submitted time 2020-03-09 Hits2750Downloads278 Comment 0

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