J Paleolimnol (2013) 50:207–229 DOI 10.1007/s10933-013-9715-9 ORIGINAL PAPER Diatom–environment relationships and a transfer function for conductivity in lakes of the Badain Jaran Desert, Inner Mongolia, China Patrick Rioual • Yanbin Lu • Handong Yang • Louis Scuderi • Guoqiang Chu • Jonathan Holmes • Bingqi Zhu • Xiaoping Yang Received: 24 January 2012 / Accepted: 5 April 2013 / Published online: 17 April 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract We describe a dataset of 26 modern diatom model, with a high coefficient of determination 2 samples and associated environmental variables from (rboot = 0.91) and low prediction error (RMSEPboot = -1 the Badain Jaran Desert, northwest China. The influ- 0.136 log10 lScm ). To assess its potential for ence of electrical conductivity (EC) and other variables palaeosalinity and palaeoclimate reconstructions, the on diatom distribution was explored using multivariate EC transfer function was applied to fossil diatom analyses and generalized additive modeling of species assemblages from 210Pb-dated short sediment cores response curves. A transfer function was derived for collected from two subsaline lakes of the Badain Jaran EC, the variable with the largest unique effect on Desert. The diatom-inferred (DI) EC reconstructions diatom variance, as shown by partial canonical corre- were compared with meteorological data for the past spondence analysis. Weighted-averaging partial least 50 years and with remote sensing data for the period squares regression and calibration provided the best AD 1990–2012. Changes in DI–EC were small and their relationship with climate was weak. Moreover, remote sensing data indicate that the surface areas and Electronic supplementary material The online version of water depths of these lakes did not change, which this article (doi:10.1007/s10933-013-9715-9) contains supplementary material, which is available to authorized users. suggests that water loss by evaporation is compensated P. Rioual (&) Á Y. Lu Á G. Chu Á X. Yang J. Holmes Key Laboratory of Cenozoic Geology and Environment, e-mail: [email protected] Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China L. Scuderi e-mail: [email protected] Department of Earth and Planetary Sciences, University of New Mexico, MSC03 2040, Albuquerque, NM 87131, Y. Lu USA e-mail: [email protected] e-mail: [email protected] G. Chu e-mail: [email protected] B. Zhu Key Laboratory of Water Cycle and Related Land Surface X. Yang Processes, Institute of Geographic Sciences and Natural e-mail: [email protected] Resources Research, Chinese Academy of Sciences, Beijing 100101, China H. Yang Á J. Holmes e-mail: [email protected] Environmental Change Research Centre, University College London, Pearson Building, Gower Street, London WC1E 6BT, UK e-mail: [email protected] 123 208 J Paleolimnol (2013) 50:207–229 by groundwater inflow. These results suggest that the and related variables such as electrical conductivity (EC) response of these lakes to climate change is mediated and concentrations of anions and cations (Fritz et al. by non-climatic factors such as the hydrogeological 1993; Gasse et al. 1995; Wilson et al. 1996;Gell1997; setting, which control recharge from groundwater, and Reed 1998;Daviesetal.2002; Ryves et al. 2002; may be non-linear and non-stationary. Verleyen et al. 2003;YangXDetal.2003;Shinneman et al. 2009;Wangetal.2011;Reedetal.2012). Keywords Diatoms Á Transfer function Á Electrical Our research on the lakes of the Badain Jaran had conductivity Á Saline lakes Á Badain Jaran Desert Á two aims. First, we explored the relationship between China the composition of diatom assemblages in surface sediment samples and lake-water chemistry and Introduction developed diatom-based transfer-functions. Second, we applied one of these transfer functions to diatom The Badain Jaran Desert, in western Inner Mongolia records from short sediment cores to infer recent (China) is characterized by a unique landscape in which changes in lake conditions. This work contributes to megadunes, the tallest in the world, coexist with[100 the wider application of lacustrine diatoms for the permanent spring-fed lakes (Yang 2000). In recent study of Holocene climate variability in the drylands years, research in this desert has focused mainly on the of northern China and Central Asia. geomorphology and evolution of the megadunes (Yang XP et al. 2003), the source of recharge for the inter-dune Study area lakes, past lake-level fluctuations recorded in former shorelines (Yang et al. 2010) and the geochemistry of We focused on the southeastern Badain Jaran Desert, the lakes and groundwater (Yang and Williams 2003). from 102°14 to 102°310E and 39°33 to 39°530N, where There is, however, scant knowledge on the current most lakes are located (Fig. 1). The lakes have a limnology of these lakes and no palaeolimnological narrow range of altitude, 1,162–1,337 m above sea work has been published. It is known, however, that level. Surface morphology consists of sand dunes with lakes in the Badain Jaran Desert show a wide range in a maximum height of 460 m. The regional climate is salinity, from subsaline to hypersaline (Hofmann 1996; strongly continental and hyper-arid. During the winter Yang and Williams 2003). months, this desert is under the influence of the dry and Closed-basin lakes in arid regions respond rapidly cold air masses associated with the high-pressure to climate-driven changes in hydrology, with oscilla- system centered over Mongolia. At the weather station tions in the balance between precipitation and evap- of Ekenhuduge town, in Alashan Youqi county, at the oration having an impact on both changes in lake level southern edge of the desert (39°120N, 101°400E), the and the concentration of dissolved salts (Fritz 2008). mean annual temperature is 7.7 °C, and mean monthly The situation is more complicated for lakes in the temperature ranges from -10 °C in January to Badain Jaran Desert. Although there are neither ?25 °C in July. The average annual precipitation is streams discharging into them nor outlets draining 118 mm, but inter-annual variation is very high. More them, these lakes cannot be considered strictly closed- than half of the precipitation falls in the summer basin lakes as they are fed by freshwater springs and months between June and August, and is derived from can be considered seepage lakes (Hofmann 1996). the East Asian summer monsoon. Diurnal tempera- Nevertheless, recent work has shown that local tures in summer months range from 0 to[40 °C (Yang precipitation makes a significant contribution to and Williams 2003; Yang XP et al. 2003). groundwater recharge of these lakes and that their past water-level variations should reflect palaeocli- matic changes (Yang et al. 2010). Materials and methods Among the environmental indicators that can be found in lake sediments from arid regions, diatoms, which are Physical and chemical variables unicellular algae with a cell wall composed of silica (Si), have been widely used to reconstruct past changes in Forty-two lakes were sampled during four field limnological variables, in particular lake-water salinity campaigns in June 2007, October 2008, March and 123 J Paleolimnol (2013) 50:207–229 209 Fig. 1 Map of the study 95o 100o 105o 110o area in north-central China (a) (a) and sampled sites in the 45o Badain Jaran desert (b). In a, Mongolia the location of the nearest meteorological station Inner Mongolia (Ekenhuduge town, Alashan Gansu 40o Youqi county) is given. b Satellite image of the China Ekenhuduge south-east corner of the Lanzhou o BadainJaran Desert, Qinghai 35 showing the 42 lakes Xian Shaanxi sampled in this study. Lakes Sichuan included in the current research are labeled (b) according to their number in Table 1 N 50' o 39 40' o 39 5km 102o15' 102o30' October 2009 (Fig. 1; Table 1). Altitude, latitude and Some lakes were sampled up to three times from 2007 longitude of sampling sites were measured in the field to 2009, although most were sampled once. using a MagellanÒ handheld GPS. Lake area was EC, pH, total alkalinity (Alk), total phosphorus estimated from topographic maps and satellite images (TP) and total nitrogen (TN) were measured on Ò - 2- - (Google Earth Pro ). For water chemistry analysis, unfiltered lake water. Anions (Cl ,SO4 ,NO3 ), surface water samples were collected by hand cations (Ca2?,Mg2?,K?,Na?), dissolved organic (*0.3 m depth) from the deepest part of each lake, carbon (DOC) and dissolved Si were measured on as determined either with a hand-held acoustic depth water filtered through Whatman GF/FÒ glass fiber meter in deep lakes or with a ruler for shallow lakes. filters. Anion concentrations were measured on a 123 210 J Paleolimnol (2013) 50:207–229 Table 1 Geographical location, maximum depth, lake area, electrical conductivity and salinity of the 42 lakes included in the Badain Jaran dataset (the date of sampling is indicated in the last column on the right) S. no. Lake name Code Latitude (°) Longitude Altitude Depth Area EC 25 Salinity Date (°) (m asl) (m) (ha) (mS/cm) (g/L) 1 Aer Jilin AERJ 39.34.319N 102.14.485E 1,202 1.70 7.3 2.4 2.0 Jun-07 2 Badan Bei Hu 1 BADB1 39.33.720N 102.21.078E 1,212 0.20 0.3 131.1 160.0 Oct-08 3 Badan Bei Hu 2 BADB2 39.33.399N 102.21.180E 1,208 0.90 1.0 11.6 9.8 Oct-08 4 Badan Bei Hu 3 BADB3 39.33.387N 102.21.312E 1,208 0.50 0.3 38.1 30.3 Oct-08 5 Badan Dong Hu BADD 39.33.120N 102.21.859E 1,202 1.40 6.5 2.5 1.6 Oct-08 6 Badan Xi Hu BADX 39.33.157N