What Makes Haloxylon Persicum Grow on Sand Dunes While H

J Arid Land (2014) 6(5): 581–591 doi: 10.1007/s40333-014-0029-1 jal.xjegi.com; www.springer.com/40333 What makes Haloxylon persicum grow on sand dunes while H. ammodendron grows on interdune lowlands: a proof from reciprocal transplant experiments GuiQing XU, DanDan YU, JiangBo XIE, LiSong TANG, Yan LI State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China Abstract: Determining the mechanisms underlying the spatial distribution of plant species is one of the central themes in biogeography and ecology. However, we are still far from gaining a full understanding of the autecological processes needed to unravel species distribution patterns. In the current study, by comparing seedling recruitment, seedling morphological performance and biomass allocation of two Haloxylon species, we try to identify the causes of the dune/interdune distribution pattern of these two species. Our results show the soil on the dune had less nutrients but was less saline than that of the interdune; with prolonged summer drought, soil water availability was lower on the dune than on the interdune. Both species had higher densities of seedlings at every stage of recruitment in their native habitat than the adjacent habitat. The contrasting different adaptation to nutrients, salinity and soil water conditions in the seedling recruitment stage strongly determined the distribution patterns of the two species on the dune/interdune. Haloxylon persicum on the dunes had lower total dry biomass, shoot and root dry biomass, but allocated a higher percentage of its biomass to roots and possessed a higher specific root length and specific root area by phenotypic traits specialization than that of Haloxylon ammodendron on the interdune. All of these allowed H. persicum to be more adapted to water stress and nutrient shortage. The differences in morphology and allocation facilitated the ability of these two species to persist in their own environments. Keywords: Haloxylon; seedling recruitment; root distribution; biomass allocation; species distribution Citation: GuiQing XU, DanDan YU, JiangBo XIE, LiSong TANG, Yan LI. 2014. What makes Haloxylon persicum grow on sand dunes while H. ammodendron grows on interdune lowlands: a proof from reciprocal transplant experiments. Journal of Arid Land, 6(5): 581–591. doi: 10.1007/s40333-014-0029-1 Spatial patterns of species diversity and species dis- poral scales. For instance, climate appears to be im- tribution are central to ecology and have fascinated portant at the landscape level and above (Davis and naturalists, ecologists and biogeographers for centu- Shaw, 2001; Walther et al., 2007). Soil or topography ries (Zimmermann et al., 2009; Eiserhardt et al., 2011). dominates at landscape and local scales, hydrology at The factors influencing species distribution have be- local scales, and dispersal functions at all scales (An- come a major concern and attention has been focused gert and Schemske, 2005). Therefore, understanding on the roles played by climate (Honnay et al., 2002; the mechanisms underlying the size, shape and dy- Svenning and Skov, 2007), topography and habitat namics of the geographic distributions of various spe- heterogeneity (John et al., 2007), dispersal (Svenning cies remains a key challenge (Pennisi, 2005; Gaston, et al., 2008) and biotic interactions (Richards et al., 2009). Specifically, as the causes of species distribu- 1997; Araújo and Luoto, 2007). However, determi- tions do not function independently (McDowall, 2004) nants of species distributions vary on spatial and tem- and are scale dependent (Levin, 1992), the importance Corresponding author: Yan LI (E-mail: [email protected]) Received 2013-10-12, revised 2014-03-31, accepted 2014-04-10 © Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Science Press and Springer-Verlag Berlin Heidelberg 2014 582 JOURNAL OF ARID LAND 2014 Vol. 6 No. 5 of different mechanisms varies with scales (Hu et bution (Pohlman et al., 2005; Pineda-GarcÍA et al., al.,2012; Schei et al., 2012). 2011; Pichancourt and van Klinken, 2012). However, At local (<1,000 m) to regional scales (100 km), the role of morphologic traits and biomass allocation Tuomisto and Poulsen (1996), Richards et al. (1997), in influencing species geographic distributions has not and John et al. (2007) reported plant species’ distribu- yet been clarified in the field (Poot and Lambers 2003; tions are strongly associated with edaphic conditions Ellers and Stuefer, 2010). including soil chemistry and nutrient availability. The Haloxylon ammodendron (C. A. Mey.) Bunge and influence of soil texture on hydrological conditions H. persicum Bunge ex Boiss. et Buhse (Chenopodi- may affect plant species distributions and diversity aceae) are two xerophytic desert trees (Song et al., (Rietkerk et al., 2002; Palm et al., 2007). Also, topog- 2005). H. ammodendron occurs naturally in various raphy may affect plant distributions indirectly by habitats, including gravel desert, clay desert, fixed and modulating other environmental factors such as soil semi-fixed sand, and saline land in Asian and African conditions, hydrology, wind exposure, as well as tem- deserts (Tobe et al., 2000). H. persicum occurs natu- perature and fog frequency (Svenning, 2001; Swen- rally in non-saline sandy deserts in Central Asia, the ning et al., 2009). Although the influence of environ- Middle East, Afghanistan, northwestern China and mental conditions on plant distribution patterns have Near Eastern deserts (Song et al., 2005; Al-Khalifah been well documented in the local scales, the related and Shanavaskhan, 2007). At the southern fringe of process and mechanisms causing these patterns are the Gurbantonggut Desert, the above two Haloxylon still poorly known, especially for tree species (Engel- species are the major dominant species for their re- brecht et al., 2007). Far less attention has been paid to spective plant communities. H. ammodendron occu- the dominant processes and mechanisms mediating pies interdunes and the flat slopes of dunes and H. tree species distribution patterns during various life persicum occurs mainly on the top of dunes, with both stages. species rarely growing together. The contrasting dis- Among the main processes and mechanisms of tribution patterns of the two Haloxylon species have population ecology, the regeneration stage is often the intrigued scientists in plant geography for many years. most critical stage during the life history of plants in However, we are still far from fully understanding determining adult plant distribution (Davis, 1991; what controls this distribution pattern. Pratt et al., 2008), especially as it relates to adaptation Sandy desert, characterized by the alternative dis- to local edaphic and microclimatic conditions during tribution of sand dunes and interdune lowlands, usu- germination and seedling establishment (Mustart and ally shows a varying pattern of vegetation composi- Cowling, 1993; Daws et al., 2002; Masaki et al., tion and contrasting plant community distribution on 2007). A reciprocal transplant approach had been con- the dune and interdune habitats (Pemadasa et al., 1974; sidered to be an effective method to ascertain the im- Avis and Lubke, 1996; Phillips et al., 2001; Liu et al., portance of edaphic factors on seedling establishment 2007). Desert dunes and interdune lowlands had been and species distribution (Wang et al., 1997). By mon- proven to provide habitat heterogeneity and to pro- itoring seedlings emergence, establishment, and mor- foundly influence the spatial and temporal distribution tality of species on their own and adjacent soils in of water and nutrients across the landscape (Rosenthal natural habitats, the edaphic factors that determine the et al., 2005; Grigg et al., 2008; Zuo et al., 2009). Cur- seedling distribution can be determined (Mustart and rently, topographic, edaphic and natural disturbance Cowling, 1993; Richards et al., 1997). characteristics, such as the underground flow of saline Furthermore, phenotypic plasticity, morphological water as well as sand movement or sand burial, influ- characteristics and biomass allocation have long been ence species composition and distribution of dune proposed to be the key mechanisms used by plant spe- ecosystems in deserts (Barnes and Harrison, 1982; cies to adaptively maintain distributions by enhancing Moreno-Casasola, 1988; Olff et al., 1993; Maun and physiological and demographic components of fitness Perumal, 1999). However, most of the research fo- (Poot and Lambers, 2003; Pichancourt and van cused on coastal and lacustrine sand dune systems, Klinken, 2012) and thus can also affect species distri- making the results of such research barely applicable GuiQing XU et al.: What makes Haloxylon persicum grows on sand dunes while H. ammodendron grows on interdune lowlands: …583 to sand dune systems in the continental interior such cluding above two Haloxylon species with typical sand as the Gurbantonggut Desert in Central Asia. Previous dunes-interdune lowlands distribution. Basing on a field studies in this typical temperate desert showed soil survey from 5 sites, the mean density of adult trees was mechanical composition significantly affects the veg- 120 plants/hm2 for H. persicum and 700 plants/hm2 for etation distribution. H. ammodendron benefits from H. ammodendron in their respective habitats. coarse textured soil along environmental gradients 1.2 Background data:

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