Soil organic phosphorus transformations along a coastal dune chronosequence under New Zealand temperate rain forest

Abstract

The chemical composition of soil phosphorus can vary markedly during pedogenesis, which has implications for phosphorus availability to plant and microbial communities during long-term ecosystem development. We used NaOH-EDTA extraction and solution 31 P NMR spectroscopy to examine changes in soil phosphorus composition along the Haast chronosequence, a 6,500 year sequence of coastal dunes under lowland temperate rain forest on the west coast of the South Island of New Zealand. Soils along the chronosequence contained a variety of inorganic (orthophosphate, pyrophosphate, and longchain polyphosphate) and organic (phosphomonoesters, phosphodiesters, and phosphonates) phosphorus compounds, although long-chain polyphosphates were detected only in the organic horizon and phosphonates were detected only in mineral soil. The concentrations of most compounds increased initially during the first few hundred years of pedogenesis and then declined as soils aged. However, concentrations of phospholipids, DNA, and longchain polyphosphate all increased markedly in the organic horizon of older sites. The four inositol hexakisphosphate stereoisomers (myo, scyllo, neo, and D-chiro) accounted for a considerable proportion of the phosphomonoesters in mineral soil along the sequence (36-52 % of the organic phosphorus), but were not detected in quantifiable concentrations in the youngest mineral soil and all but one organic horizon. Concentrations of the two most abundant isomers (myo-and scyllo) declined along the chronosequence, but the scyllo isomer increased markedly as a proportion of the soil organic phosphorus as soils aged. Amorphous aluminum and iron oxides (i.e., extractable in acid-ammonium oxalate) increased continually throughout the chronosequence, indicating that the decline in inositol hexakisphosphate is due to low phosphorus availability rather than a decline in stabilization potential. Overall, these results provide further evidence that the chemical composition of organic and inorganic phosphorus pools vary markedly during pedogenesis, which has important implications for our understanding of biologically-available organic phosphorus during ecosystem development.

The composition of organic phosphorus in soils of the Snowy Mountains region of south-eastern Australia

“…Turner et al 2012;Vincent et al 2012;Ahlgren et al 2013;Vincent et al 2013;Turner et al 2014). This supports our hypothesis that climate has a strong influence on organic P speciation, with IP 6 comprising a larger proportion of organic P in cold and wet environments, whereas humic-P comprises most of the organic P in warm and dry environments.…”

“…This supports our hypothesis that climate has a strong influence on organic P speciation, with IP 6 comprising a larger proportion of organic P in cold and wet environments, whereas humic-P comprises most of the organic P in warm and dry environments. The soils along a chronosequence in New Zealand, where mean annual rainfall is 3455 mm and the mean monthly temperature range is 7À158C, displayed similar organic P compositions to those of the soils presented in this study (Turner et al 2014) in that the phosphomonoester region in the New Zealand soils was also was dominated by myo-and scyllo-IP 6 and smaller quantities of the neo-and D-chiro-IP 6 stereoisomers were also detected. Similarly, pasture soils from the Falkland Islands were particularly rich in scyllo-IP 6 and contained detectable amounts of the neo-and chiro-stereoisomers (Turner et al 2012).…”

“…In particular, the presence of phosphonates, which we identified in two of the soils at the coldest and wettest locations, have not been reported before in Australian soils but have been identified in cold, wet and acidic soils elsewhere where microbial activity is limited (Tate and Newman 1982;Zech et al 1987;Gil-Sotres et al 1990). Similarly, neo-and D-chiro-IP 6 are also often associated with soils from cooler, rather than warmer climates (Omotoso and Wild 1970;Irving and Cosgrove 1982;Turner et al 2014;Jarosch et al 2015), although the origins and dynamics of these compounds are still not well understood.…”

Identification of inositol hexakisphosphate binding sites in soils by selective extraction and solution 31P NMR spectroscopy

“…Soil was collected from three ecosystems: tropical rice paddies in Madagascar (Turner, 2006), temperate grasslands in the Falkland Islands , and temperate rainforest at the Haast chronosequence in New Zealand (Turner et al, 2014). The following labels were used: for the rice paddies (MDG), temperate grassland soils (EAST) and temperate rainforest soils (Dune).…”

“…The soils had a range of properties, including total P concentrations (Table 1), and were known from previous studies to contain IP 6 . Detailed information on the soils is available elsewhere (Turner, 2006;Turner et al, 2012Turner et al, , 2014, although it should be noted that the temperate grassland soils were from slightly different locations from those studied previously . All samples were surface soils (0-10 cm) and were air dried, screened and sieved (b2 mm) prior to analysis, with storage in sealed plastic bags at ambient laboratory temperature and humidity (22°C and 55%, respectively).…”