N and P in New Zealand Soil Chronosequences and Relationships with Foliar N and P

Abstract

The growth of forest species in soil development chronosequences becomes increasingly phosphorus (P)-limited with time, as P is weathered, eroded and leached from soil. Foliar nitrogen (N) concentrations also tend to decrease with soil age when vegetation may be limited in both N and P. Here we report on soil development in temperate rain forests along three New Zealand chronosequences that have minimal pollution and disturbance from human activities, at Franz Josef, Waitutu and Central Volcanic Plateau, and on factors influencing soil net N mineralization (aerobic; 56 days) and foliar N and P concentrations. Except in very young soils (<500 years), at least 85% of total-P in mineral soil (0-10 cm) was transformed to organic-P. In each chronosequence, total-P declined with time, and foliar N:P ratios (mass) generally increased from 8 to 15-18, suggesting P was more limiting than N in the oldest soils of the chronosequence. There was a negative relationship between net N mineralization and C:N ratio for mineral soil. For the FH (organic) layer, net N mineralization had the strongest relationships with total-N concentration (positively) and C:organic-P ratio (negatively); however, relationships varied with forest group, suggesting that other factors were also important. Foliar P of kamahi (Weinmannia racemosa Linn. f.), a dominant canopy species, was related to soil organic-P, suggesting mineralization was an important process for tree nutrition.Foliar N was positively related to N concentration in the FH layer, but was not significantly related to any measured property in mineral soil, possibly because of the wide range of soils. The consistent declines in both soil and foliar P across the contrasting chronosequences strongly suggest that vegetation becomes progressively P-limited during long-term ecosystem development.

Understanding ecosystem retrogression

“…A common aspect of the pedogenic changes in soil P during retrogression is its accumulation in organic and occluded forms, which can eventually represent most of the total soil P (Syers and Walker 1969, Parfitt et al 2005); however, this pattern of change is not universal (Lagerstrom et al 2009). The accumulation of organic P is rarely assigned any ecological significance because models that describe changes in P during pedogenesis consider organic P as a single functional pool of limited availability to plants (Walker and Syers 1976;but see Turner 2008).…”

Detecting Terrestrial Nutrient Limitation: A Global Meta-Analysis of Foliar Nutrient Concentrations after Fertilization

“…However, foliar nutrient concentrations are another valuable way to assess nutrient limitation because numerous studies demonstrate that they reflect soil nutrient concentrations at spatial scales of single sites (Shaver and Melillo, 1984;Valentine and Allen, 1990) and across chronosequences, environmental gradients, and ecosystem types (Vitousek, 1998;Han et al, 2005;Parfitt et al, 2005;Townsend et al, 2007;Ordoñez et al, 2009;Cleveland et al, 2011). When foliar nutrients are assessed as one-time measurements it is difficult to use them as evidence of nutrient limitation, because of the tremendous variation among study sites and the lack of universal cutoff values that indicate limitation.…”

Oxygen isotopes of phosphate and soil phosphorus cycling across a 6500 year chronosequence under lowland temperate rainforest

“…They are of significance because the space for time substitution allows observation of pedogenesis and associated ecosystem development over long time spans (Stevens and Walker, 1970). Soil chronosequences are often characterized by a long-term decline in total soil P as the initial source of inorganic P in primary minerals is rapidly depleted (Crews et al, 1995;Olander and Vitousek, 2004;Wardle et al, 2004;Parfitt et al, 2005;Turner et al, 2007). This classic paradigm, defined by Walker and Syers (1976), has been generally accepted as the overall model for P transformations as soils age.…”

“…This classic paradigm, defined by Walker and Syers (1976), has been generally accepted as the overall model for P transformations as soils age. The changes are twofold, as there is an overall decrease in P concentration due to leaching and erosion (Hedin et al, 2003) and a shift in the P forms that remain, with a decline in primary mineral P and an increase in organic P and inorganic P associated with secondary minerals (Crews et al, 1995;Parfitt et al, 2005;Turner et al, 2007). On stable landscapes, the long-term decline in soil P as ecosystems age can ultimately lead to a decline in plant biomass and productivity, termed ecosystem retrogression (Wardle et al, 2004).…”