Soil Development and Nutrient Availability Along a 2 Million-Year Coastal Dune Chronosequence Under Species-Rich Mediterranean Shrubland in Southwestern Australia Benjamin L. Turner & Etienne Laliberté Ecosystems ISSN 1432-9840 Ecosystems DOI 10.1007/s10021-014-9830-0 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media New York. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”. 1 23 Author's personal copy Ecosystems DOI: 10.1007/s10021-014-9830-0 Ó 2014 Springer Science+Business Media New York Soil Development and Nutrient Availability Along a 2 Million-Year Coastal Dune Chronosequence Under Species-Rich Mediterranean Shrubland in Southwestern Australia Benjamin L. Turner1* and Etienne Laliberte´2 1Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Republic of Panama; 2School of Plant Biology, The University of Western Australia, Crawley, Perth, Western Australia 6009, Australia ABSTRACT Soil chronosequences provide valuable model grains over a petrocalcic horizon that occurs at systems to investigate pedogenesis and associated increasing depth as soils age. Early Pleistocene effects of nutrient availability on biological com- soils (>2,000,000 years old) are completely lea- munities. However, long-term chronosequences ched of iron oxides and consist of bleached quartz occurring under seasonally dry climates remain sand several meters deep. Changes in soil organic scarce. We assessed soil development and nutrient matter and nutrient status along the Jurien Bay dynamics along the Jurien Bay chronosequence, a chronosequence are consistent with patterns 2 million-year sequence of coastal dunes in observed along other long-term chronosequences southwestern Australia. The chronosequence is and correspond closely to expectations of the significant because it occurs in a Mediterranean Walker and Syers (1976) model of biogeochemical climate and supports hyperdiverse shrublands change during pedogenesis. Organic carbon and within a global biodiversity hotspot. Young soils nitrogen (N) accumulate rapidly to maximum formed during the Holocene (<6,500 years old) amounts in intermediate-aged Holocene dunes are strongly alkaline and contain abundant car- and then decline as soils age. In contrast, total bonate, which is leached from the profile within a phosphorus (P) declines continuously along the few thousand years. Middle Pleistocene soils (ca chronosequence to extremely low levels after 120,000–500,000 years old) are yellow decalcified 2 million years of pedogenesis, eventually repre- sands with residual iron oxide coatings on quartz senting some of the lowest P soils globally. Ratios of soil organic carbon to P and N to P increase continuously along the chronosequence, consis- Received 25 June 2014; accepted 20 October 2014 tent with a shift from N limitation on young soils Electronic supplementary material: The online version of this article to extreme P limitation on old soils. Phosphorus (doi:10.1007/s10021-014-9830-0) contains supplementary material, fractionation by sequential extraction reveals a which is available to authorized users. Author contributions BT and EL designed the study and conducted rapid decline in primary and non-occluded phos- the fieldwork. BT conducted laboratory analysis and wrote the manu- phate and an increase in organic and occluded P as script, with input from EL. soils age. Concentrations of extractable (that is, *Corresponding author; e-mail: [email protected] Author's personal copy B. L. Turner and E. Laliberte´ readily bioavailable) N and P, as well as changing patterns of nutrient limitation linked to exchangeable cations, are greatest in Holocene long-term soil and ecosystem development under dunes and decline to low levels in Pleistocene a Mediterranean climate. dunes. Extractable micronutrient concentrations were generally very low and varied little across Key words: chronosequence; ecosystem devel- the chronosequence. We conclude that the Jurien opment; pedogenesis; nutrients; phosphorus; Bay chronosequence is an important example of nitrogen. INTRODUCTION 2008; Jangid and others 2013; Laliberte´ and others A soil chronosequence is a series of soils that differ 2013a, 2014). from each other only in the time since the onset of Long-term retrogressive soil chronosequences their formation (Stevens and Walker 1970; Vito- have been identified in only a few locations around usek 2004). Other soil-forming factors, including the world (Peltzer and others 2010). Well-known parent material, topography, climate, and vegeta- examples are the Hawaiian Islands chronosequence tion, are held relatively constant, although it is (Crews and others 1995; Vitousek 2004), the Franz recognized that climate and vegetation rarely con- Josef post-glacial chronosequence in New Zealand form strictly to this definition (Huggett 1998). (Walker and Syers 1976), and the Cooloola coastal Nevertheless, soil chronosequences provide an dune chronosequence in eastern Australia important means of assessing pedogenesis and (Thompson 1981). However, the majority of these associated patterns of nutrient availability and chronosequences occur in relatively humid cli- limitation in terrestrial ecosystems over timescales mates, with only a small number in more arid from hundreds to millions of years (Vitousek 2004; ecosystems. These include the 3 million-year San Walker and others 2010; Turner and Condron Joaquin alluvial terrace sequence under Mediter- 2013). ranean grassland in California (Harden 1982; Typically, nutrient availability follows a predict- Baisden and others 2002) and the 3 million-year able pattern during long-term pedogenesis (Walker basalt chronosequence in the Northern Arizona and Syers 1976). Nitrogen (N) is absent from most Volcanic Field, which supports a semiarid pin˜ on– parent materials, but accumulates quickly in young juniper woodland (Selmants and Hart 2008, 2010). soils through biological N fixation (Menge and Long-term nutrient dynamics might be expected Hedin 2009). In contrast, phosphorus (P) declines to deviate from the Walker and Syers (1976) model continually as pedogenesis proceeds, as it is lost in in dry ecosystems through a slower rate of P loss by runoff at a greater rate than it is supplied by bed- leaching (Lajtha and Schlesinger 1988). However, rock weathering and atmospheric deposition both the Northern Arizona and the San Joaquin (Walker and Syers 1976). At the same time, chronosequences show patterns of soil nutrients chemical and biological transformations further that are consistent with the Walker and Syers reduce the availability of the P remaining in the soil model of nutrient dynamics during pedogenesis. by converting primary mineral phosphate into or- Additional information from similar arid environ- ganic forms and occluding them within secondary ments around the world, which includes much of minerals (Walker and Syers 1976; Parfitt and others the Australian continent, is required to confirm the 2005; Turner and others 2007). As a result, primary broad applicability of the Walker and Syers (1976) productivity tends to be limited by N availability on model to Mediterranean ecosystems. young soils and by P availability on old soils Here we report the results of a study of soils (Vitousek and Farrington 1997; Laliberte´ and oth- along a 2 million-year coastal dune chronose- ers 2012; Coomes and others 2013). In very old quence at Jurien Bay, Western Australia. The soils on stable landscapes, P limitation can become chronosequence occurs under a Mediterranean strong enough to constrain plant biomass, produc- climate but differs from the previously studied dry tivity, and other ecosystem processes, termed chronosequences in terms of its origin and parent ‘ecosystem retrogression’ (Wardle and others material (coastal carbonate dunes) and is of par- 2004), and to influence the distribution and ticular interest because of the exceptionally high diversity of plant and microbial communities levels of plant diversity due to its location within (Williamson and others 2005; Lambers and others a global biodiversity hotspot (the Southwest Author's personal copy Soil Development and Nutrient Availability Australian Floristic Region) (Hopper and Gioia the east by the Darling Fault, which separates it 2004). A glasshouse nutrient-addition experiment from the Archean Yilgarn Block, part of the Wes- using soils from the Jurien Bay chronosequence tern Australian Shield (Playford and others 1976). found evidence for a shift from N to P limitation Coastal dune soils in the Swan Coastal Plain have (Laliberte´ and others 2012), which was supported been grouped into three main units based on the by a subsequent analysis of foliar nutrient con- corresponding dune systems (McArthur and Bet- centrations and resorption efficiency in naturally tenay 1974; McArthur 2004; Laliberte´ and others occurring plants in the field (Hayes and others 2012). The