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1. chinaXiv:202005.00089 [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: Biology >> Botany >> Applied botany

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 2020-05-31 From cooperative journals:《Journal of Arid Land》 Hits11232Downloads794 Comment 0

2. chinaXiv:201906.00048 [pdf]

Effects of land use and cover change on surface wind speed in China

LI Yupeng
Subjects: Geosciences >> Geography

The surface wind speed (SWS) is affected by both large-scale circulation and land use and cover change (LUCC). In China, most studies have considered the effect of large-scale circulation rather than LUCC on SWS. In this study, we evaluated the effects of LUCC on the SWS decrease during 1979–2015 over China using the observation minus reanalysis (OMR) method. There were two key findings: (1) Observed wind speed declined significantly at a rate of 0.0112 m/(s?a), whereas ERA-Interim, which can only capture the inter-annual variation of observed data, indicated a gentle downward trend. The effects of LUCC on SWS were distinct and caused a decrease of 0.0124 m/(s?a) in SWS; (2) Due to variations in the characteristics of land use types across different regions, the influence of LUCC on SWS also varied. The observed wind speed showed a rapid decline over cultivated land in Northwest China, as well as a decrease in China's northeastern and eastern plain regions due to the urbanization. However, in the Tibetan Plateau, the impact of LUCC on wind speed was only slight and can thus be ignored.

submitted time 2019-06-20 From cooperative journals:《Journal of Arid Land》 Hits7559Downloads876 Comment 0

3. chinaXiv:201804.01249 [pdf]

Negligible effect of tooth reduction on body mass in Mesozoic birds

ZHOU Ya-Chun; ZHANG Fu-Cheng; Corwin SULLIVAN
Subjects: Geosciences >> Geology

Tooth reduction and loss was an important evolutionary process in Mesozoic birds. Analysis of evolutionary trends in the total mass of the dentition, a function of tooth size and tooth number, has the potential to shed light on the evolutionary pattern of tooth reduction and loss, and on the causes of this pattern. Because modern birds lack teeth, however, they cannot provide the basis for a model that would allow estimation of tooth masses in their Mesozoic counterparts. We selected the teeth of crocodilians as analogues of those in Mesozoic birds because the former are the closest living relatives of the latter, and the two groups are similar in tooth morphology, tooth implantation, and tooth replacement pattern. To estimate tooth masses in Mesozoic birds, we formulated four regression equations relating tooth mass to various linear dimensions, which were measured in 31 intact isolated teeth from eight individual crocodiles (Crocodylus siamensis). The results for Mesozoic birds show that dental mass as a proportion of body mass was negligible, at least from the perspective of flight performance, suggesting that selection pressure favoring body mass reduction was probably not the primary driver of tooth reduction or loss. Variations in dental mass among Mesozoic birds may reflect the different foods they ate, and the different types of feeding behavior they displayed.

submitted time 2018-04-04 From cooperative journals:《古脊椎动物学报》 Hits4488Downloads989 Comment 0

4. chinaXiv:201711.02398 [pdf]

International UTC TAI comparison based on BDS PPP

Yulong Ge; Baoqi Sun; WeiJin Qin; Mingjun Ouyang; Xuhai Yang
Subjects: Geosciences >> Other Disciplines of Geosciences

The BeiDou navigation satellite system (BDS) developed by China, and provided official service for Asia-pacific region freely since 2012. With development of BDS, BDS-based time transfer has become an important research direction in BDS’s application fields. At present, the main method of BDS-based time transfer is BDS Common View (BDS CV), which can reach nanoseconds magnitude. Hence, we investigate the performance time transfer based on BDS precise point positioning (PPP) toward UTC/TAI compute. In this contribution, we focus on UTC/TAI comparison based on BDS PPP by using developed quad-constellation GNSS software, which called National Time System Center’s (NTSC) Bernese. And a long-term data analysis is presented. The experiments include two parts: (1) The reliability of the software and multi-GNSS products; (2) The performance of the BDS PPP toward International UTC/TAI comparison. The experimental results reveal that the accuracy of NTSC’s Bernese GPS PPP can reach about 0.1 ns relative to BIPM TAI PPP solutions. Compared with BIPM TAI PPP solutions, the accuracy of GPS PPP solutions can achieve about 0.2 ns by using multi-GNSS precise products, such as GBM, COM. For BDS PPP solutions, the solutions of GPS PPP are regarded as reference values. It is demonstrated that the accuracy of time transfer based on BDS PPP can reach better 1 ns toward UTC/TAI comparison for the statistics of 30 days-arc solutions, while 0.1 ns magnitude can be achieved for the statistics of daily solutions due to the influence of the day boundary discontinuity. Moreover, four different processing strategies of BDS PPP which include tropospheric delay fixed, tropospheric delay and coordinates fixed, coordinates fixed, and BDS-only are tested. Results show that the comparable accuracy can be achieved for four processing strategies. Hence, one can conclude that the time transfer based on BDS-only PPP show a good performance toward UTC/TAI computation.

submitted time 2018-01-07 Hits9199Downloads2105 Comment 0

5. chinaXiv:201711.02563 [pdf]

Implications for Late Miocene diet from Diceros gansuensis: starch granules in tooth calculus

CHEN He; WANG Shi-Qi; TAO Da-Wei; XIA Xiu-Min; CHEN Shan-Qin; WU Yan
Subjects: Geosciences >> Geology

Reconstructing the diet of extinct species is a fundamental goal in vertebrate paleobiology. Dental calculus is the calcium phosphate deposits on teeth, which captures a large number of food particles and contains the food information of ancient animal. It is possible to explore ancient animal dietary and investigate the environmental information from dental calculus. A large number of starch granules were found in dental calculus of Dicros gansuensis excavated from the earliest Late Miocene Guonigou fauna of the Linxia Basin, Gansu Province. It is the first time that starch granules from Late Miocene were found. We classified the ancient starch granules by its morphological characteristics and also analyzed the starch granules of leaves of modern plants around the living environment of D. gansuensis to find modern starch granules and compare them with ancient ones. The results indicate that D. gansuensis may eat not only shrubs leaves, such as the plant from Caprifoliaceae, but also some tree leaves from Juglandaceae (walnut), and maybe some herbs from Ranunculaceae and Polygonaceae. It is consistent with the results of previous morphological studies, and it also provides more information. Our study extends the range of time and object for dental calculus research, and offers more possibilities for research on feeding habits of ancient mammals.

submitted time 2017-11-24 From cooperative journals:《古脊椎动物学报》 Hits4492Downloads1157 Comment 0

6. chinaXiv:201708.00336 [pdf]

Morphological coevolution of the pygostyle and tail feathers in Early Cretaceous birds

WANG Wei; Jingmai K. O'CONNOR
Subjects: Geosciences >> Geology

The transformation from a long reptilian tail to a shortened tail ending in a pygostyle and accompanied by aerodynamic fanning rectrices is one of the most remarkable adaptations of early avian evolution. However, no fossils directly capture this transition, and information regarding the structural morphology and the early evolution of the pygostyle in Mesozoic birds and their integuments is relatively limited. Here we provide a review of the pygostyle morphology of Early Cretaceous birds with comparison to the structure in living birds. This study emphasizes the convergent evolution of distally co-ossified caudal vertebrae in non-avian maniraptorans and early birds. There further exist distinct differences in pygostyle morphology between Sapeornithiformes, Confuciusornithiformes, Enantiornithes, and Ornithuromorpha. The morphology of the pygostyle and rectrices in early ornithuromorphs appear similar to that of extant birds, whereas the pygostyle in more primitive birds does not appear morphologically capable of supporting the rectricial bulbs and musculature necessary to control an aerodynamic fan-shaped tail. The rectricial bulbs and rectricial fan appear to have coevolved with the plough-shaped pygostyle early in the evolution of the Ornithuromorpha. This study also shows that the confuciusornithiform pygostyle was more similar to that of enantiornithines than previously recognized, consistent with the presence of nearly identical ornamental tail feathers in both groups. 从兽脚类恐龙中爬行类的骨质长尾,到以尾综骨为终端,并附着具有空气动力学功能的扇状尾羽的短巧尾部,是早期鸟类演化中最显著的适应性转变之一。但能直接反映这一转变的化石记录匮乏,而且对中生代鸟类尾部形态结构,以及尾综骨和尾羽早期演化的认知也相对不足。在此对早白垩世鸟类的尾综骨形态予以概述并将其与现生鸟类尾部结构类比。本研究强调了非鸟手盗龙类中尾椎的联合骨化与早期鸟类的尾综骨实属趋同演化。本研究表明,会鸟形类、孔子鸟形类、反鸟类和今鸟型类的尾综骨结构存在明显差异。今鸟型类尾综骨和尾羽(舵羽)与现代鸟类的相似,而相对更原始的鸟类的尾综骨,从形态来看,并不能支持舵羽球状膨大和必要的肌肉附着来操控具有空气动力学功能的扇状尾羽。由此可见,舵羽球状膨大、舵羽扇面与犁铧状的尾综骨是在今鸟型类演化早期相伴相生的。相对于从前的认知,本研究还发现孔子鸟类的尾综骨与反鸟类的有更多相似之处,与二者都具有的几乎相同的装饰性尾羽相符合。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits3287Downloads976 Comment 0

7. chinaXiv:201708.00335 [pdf]

A new species of Brontotheriidae from the Middle Eocene of Junggar Basin, Xinjiang, China

Li Shuo
Subjects: Geosciences >> Geology

A new species of large Irdinmanhan brontothere, Epimanteoceras mae sp. nov., is described based on an incomplete skull which was collected from the ?qbulak Formation of Sangequan site, Junggar Basin of Xinjiang Uygur Autonomous Region. The new specimen can be assigned to the genus Epimanteoceras by the large superorbital processes, the broad frontal bone, the shallow central fossae on the molars, and the absence of the anterolingual cingular cusp on molars and the hypocone on M3. E. mae is characterized by the slightly laterally bowed zygomatic arches, the medially arched parasagittal ridges, the posteromedially angled external auditory pseudomeatus, and the prominent occipital pillar processes. E. mae and E. formosus are closely related. It is uncertain whether E. mae or E. formosus forms the sister group to Brontotheriina, but both of them are the basal group of the latter in the phylogenetic analysis. They are both closed to the Irdinmanhan brontothere Protitan grangeri from Nei Mongol but much primitive than Aktautitan hippopotamopus from Kazakhstan. The discovery of E. mae in Sangequan indicates that the age of ?qbulak Formation is Middle Eocene, and earlier than that of Kyzylbulak Formation bearing A. hippopotamopus in Kazakhstan. Moreover, the discovery of E. mae in Xinjiang expanded the distribution of the genus Epimanteoceras, which was only found in Nei Mongol previously. 新疆准噶尔盆地三个泉中始新世依希白拉组内发现的晚叉额雷兽属新种-马氏晚叉额雷兽(Epimanteoceras mae sp. nov.)是新疆目前发现保存最好的雷兽头骨化石。标本为一件不完整的头骨,缺失鼻骨,前颌骨,部分上颌骨和泪骨。新种具有眶上突较粗大,额骨宽阔平坦,臼齿有中心窝,臼齿舌侧齿带前部上的齿尖不发育,M3无次尖等晚叉额雷兽属的特征。新种的颧弓成向外扩的弓形,额顶嵴在后侧向内收缩弯曲的弧度更大,外耳道较为倾斜,枕柱上方有舌状的突起,与唯一的属型种娇晩叉额雷兽(Epimanteoceras formosus)明显不同。马氏晚叉额雷兽同属型种关系最近,两者在系统发育分析中同为雷兽亚族(Brontotheriina)的基干类群,但是两者是否为后者的姊妹类群尚无法确定。和属型种一样,马氏晚叉额雷兽在演化程度上与内蒙古伊尔丁曼哈期的谷氏原雷兽(Protitan grangeri)接近,但与同时期地理位置更近的哈萨克斯坦的雷兽Aktautitan hippopotamopus相比,马氏晚叉额雷兽较原始,表明新种所在的地层时代很可能要早于发现A. hippopotamopus地层。三个泉剖面依希白拉组伊尔丁曼哈期内以前发现的化石较少,此次马氏晚叉额雷兽的发现,不仅扩大了晚叉额雷兽属的地理分布,亦为依希白拉组内存在伊尔丁曼哈期的沉积提供了新的佐证。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits1962Downloads843 Comment 0

8. chinaXiv:201708.00333 [pdf]

Cranial and dental material of Gomphotherium wimani (Gomphotheriidae, Proboscidea) from the Middle Miocene of the Linxia Basin, northwestern China

YANG Xiang Wen; LI Yu ; WANG Shi-Qi
Subjects: Geosciences >> Geology

嵌齿象是真象的基干类群,其研究历来受到重视,同时也存在很多争议。维曼嵌齿象(Gomphotherium wimani)是中国的一个特有种,之前仅有一些牙齿和破碎下颌的报道,研究者对其形态特征和演化地位的认识一直比较模糊。本文报道了发现于甘肃省临夏盆地的维曼嵌齿象的新材料,包括上沟地点一件未成年头骨和倒黑沟地点属于同一个体的部分颊齿。通过研究对比,认为维曼嵌齿象是嵌齿象中一个比较进步的种,具有如下独有特征:颊齿的主齿柱前后中心小尖分裂并成嵴状,副齿柱趋向于分裂,发育有弱的副齿柱中心小尖,齿谷中等开阔,齿冠相对较高。对过去发现的维曼嵌齿象材料的厘定表明,该种最初建立时产于泉头沟地点的一颗m3实际上是葛氏铲齿象(Platybelodon grangeri)的M3; 而西宁吊沟地点发现的维曼嵌齿象的一件M3极有可能属于铲齿象类(amebelodontids)。对厘定后的维曼嵌齿象地点的研究表明,维曼嵌齿象分布于中国甘肃、青海的几个中中新统地点,其时代基本上可以与MN6?MN7/8早期相对比,时代跨度估计为15~13 Ma。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits2087Downloads999 Comment 0

9. chinaXiv:201708.00332 [pdf]

Paleoecology of Cenozoic rhinos from northwest China: a stable isotope perspective

Dana BIASATTI; WANG Yang; DENG Tao
Subjects: Geosciences >> Geology

The diets and environments of fossil rhinocerotoids from the Linxia Basin, Gansu, China, ranging in age from 25 to 2.5 Ma, were reconstructed based on bulk and serial carbon (C) and oxygen (O) isotope analyses of tooth enamel. The results support many previous hypotheses inferred from dentition and cranial and limb morphology and offer new insight on the paleoecology of some genera. The isotopic results support the following previous hypotheses: the Late Oligocene rhino Paraceratherium inhabited a forested environment, and the coexisting rhino Allacerops lived in a relatively open habitat and had a less specialized diet; the Middle Miocene Hispanotherium grazed in open territory, whereas the contemporaneous Alicornops had a more generalized diet in a forested environment; and the Late Miocene rhino Parelasmotherium grazed in an open steppe habitat. The isotope data indicate that the rhinos Acerorhinus and Dicerorhinus inhabited open steppe environments, inconsistent with previous inferences that these two rhinos dwelled in forested environments. The isotopic results are not conclusive concerning the habitat of Iranotherium, but support previous hypotheses that this rhino was a specialized C3 grazer. The results also suggest that Chilotherium was a forest-dweller throughout much of the Late Miocene, but occupied a more open environment by the end of the Late Miocene. Additionally, the results are consistent with previous hypotheses that the Pliocene rhino Shansirhinus and the Pleistocene rhino Coelodonta were grazers in open habitats. Finally, the C isotope data support that all rhinos in this study were pure C3 feeders, confirming that C4 grasses were not an important component of the plant biomass in the Linxia Basin from 25 to 2.5 Ma. 根据牙齿釉质的全样和系列碳、氧同位素分析,重建了甘肃临夏盆地25~2.5Ma期间犀牛的食性和环境。其结果支持先前根据牙齿和头骨-肢骨形态做出的一些推断,并对部分属的古生态提出了新的看法。同位素结果支持如下的推断:晚渐新世的巨犀Paraceratherium生活于森林环境,而与其共生的异角犀Allacerops栖息地相对开阔,食性特化程度低;中中新世的西班牙犀Hispanotherium在开阔领地上取食草本植物,而同时代的奇角犀Alicornops在森林环境中具有更特化的食性;晚中新世的副板齿犀Parelasmotherium在开阔的稀树草原上取食草本植物。与先前认为无鼻角犀Acerorhinus和额鼻角犀Dicerorhinus生活于森林化环境的推断不同,数据指示这两种犀牛也生活于开阔的稀树草原环境。同位素结果未能得出伊朗犀Iranotherium的确切生活环境,但支持先前认为它特化为C3草本植物取食者的推断。研究结果也显示大唇犀Chilotherium在晚中新世的大多数时间内是森林生活者,但其在晚中新世末期占据了更开阔的环境。此外,分析结果与先前的推断一致,即上新世的山西犀Shansirhinus和更新世的披毛犀Coelodonta是开阔生活环境中的食草者。最后,碳同位素数据支持在此项研究中的所有犀牛都是纯C3取食者,确认C4植物不是临夏盆地从25Ma到2.5Ma期间植被的重要成分。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits2215Downloads916 Comment 0

10. chinaXiv:201708.00331 [pdf]

Restudy of Regalerpeton weichangensis (Amphibia: Urodela) from the Lower Cretaceous of Hebei, China

RONG Yu-Fen
Subjects: Geosciences >> Geology

Regalerpeton weichangensis was established in 2009 on an incomplete skeleton preserved mainly as an impression from the Lower Cretaceous of Hebei, China. However, several anatomical characters were misinterpreted due to distortion of the holotype, and its taxonomic position has been in debate. In this paper, R. weichangensis is redescribed based on eight new specimens and its diagnosis and phylogenetic position are re-examined. This work shows that R. weichangensis was a neotenic form with ossified carpals and tarsals. It has a series of unique combination of characteristics including the vomer with a transverse vomerine tooth row, anterior end of the cultriform process of the parasphenoid indented, basibranchial II triradiate and scapulocoracoid with a rectangular coracoid end. Phylogenetic analysis suggests Regalerpeton, Jeholotriton and Pangerpeton should be placed in the suborder Salamandroidea with three synapomorphies. Moreover, they also share unicapitate ribs with Cryptobranchoidea, which indicates that they represent an important stage of evolution in the Cryptobranchoidea-Salamandroidea split. 围场皇家螈(Regalerpeton weichangensis)于2009年基于一件产自河北围场下白垩统不完整的骨骼印痕标本命名。然而由于标本变形导致皇家螈的部分解剖学特征被曲解,系统发育位置也存在争论。本文基于八件新标本对该蝾螈的鉴定特征和系统发育位置进行了修订。研究显示,皇家螈是一种腕骨和跗骨骨化的幼态持续型蝾螈,具有独特的特征组合,包括犁骨齿列横向排列、副蝶骨前端呈齿状、基鳃骨II呈三射型以及肩胛乌喙骨的乌喙端呈矩形。新的系统发育分析根据三个近裔共性将围场皇家螈、热河螈和胖螈归入蝾螈亚目。此外,它们还与隐鳃鲵亚目共有“肋骨单关节头”这一特征,显示这三种蝾螈可能代表了隐鳃鲵亚目与蝾螈亚目分离时期这一重要演化阶段。

submitted time 2017-08-24 From cooperative journals:《古脊椎动物学报》 Hits1561Downloads697 Comment 0

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