Chapter 4 – The LithosphereChapter 4 – The Lithosphere

Phosphorus Minerals“Ultimate” limiting nutrient given its origin

Apatite only primary mineral

(4.7) Ca5(PO4)3OH + 4H2CO3 5Ca2+ + 3HPO43- + 4HCO3- + H2O

Weathered P has many fates…-- release as PO4

3- (non-occluded)

-- binding by iron and aluminum sesquioxides (occluded)-- storage in organic matter (organic P)-- plant uptake-- lost by leaching

Evolved plant strategies for P uptake:- accelerate P weathering (via chelators)- inhibit Al and Fe oxide crystallization (via chelators) - associate with mycorrhizal fungi

Chapter 4 – The Lithosphere

Walker and Syers (1976) model during pedogensis

Chapter 4 – The Lithosphere

Role of pH in affecting P availability and occlusion

StationaryHotpsot

Crews et al. (1995) Ecology 76(5):1407-1424 Crews et al. (1995) Ecology 76(5):1407-1424 P fractions in soils of Hawaiian archipelagoP fractions in soils of Hawaiian archipelago

Soil Forming Factors (Jenny 1980)1. Parent Material2. Climate3. Vegetation4. Topography5. Time

Distribution of P corresponds well toWalker and Syers (1976) model

Total mass of P doesn't declinethrough soil development

Figure 3 Change in soil element content integrated over the top metre of soil, compared with element contents in the lava parent material(38). Measured element concentrations (a, Mg, Ca, Si; b, Al, P) were corrected for changes in density and loss of mass during soil formation71. In c, the rates of loss of P and Ca are calculated using the mass of an element lost between two sites and the corresponding difference in age.

Figure 4 Comparison of Ca inputs from substrate and the atmosphere. a, Rate of Ca loss from substrate (Fig. 3c) plotted with the present addition of Ca in rain water and cloud water. b, The per cent of total Ca inputs that are derived from the atmosphere, calculated by dividing the atmospheric contribution by the sum of atmospheric and weathering (actually loss from substrate) contribution.

Radioactive DecayRadioactive Decay

Source of 87Sr: radiogenic origin 87Rb & primordial nucleo-synthesis

Figure 5 Indicators of the sources of Sr and Ca measured for each site. a, The 87Sr/86Sr ratio of Sr extracted from soil exchange sites and from Metrosideros leaves. The isotope ratio is primarily constrained by the value for Hawaiian lava of 0.7035 and a value for sea water (and hence rainfall in Hawaii) of 0.7092 (ref. 48). b, The concentration of Ca in soil solution collected by lysimeters inserted below the primary rooting zone in the soils. The measured values have been normalized using a standard sea-salt ratio to reflect Ca released to soil solution by mineral weathering only.

Fig. 2. Variation in the 87Sr/86Sr composition of seawater for the past 100 Ma [19]. Dashed lines represent the mean 87Sr/86Sr values for the Northern and Southern Lowlands. Gray shading represents 2 standard deviation about the mean values.

Hodell et al. (2003) J. Archaeological Science 31(5):585

Atm.=0.7092

Lava=0.7035

Mineral weathering only

Figure 8 Comparison of phosphorus inputs from substrate and the atmosphere. a, Rate of P loss from the soil as a whole (Fig. 3c) plotted with the long-term average addition of P in mineral aerosol. b, The per cent atmospheric contribution for each site calculated by dividing the atmospheric contribution by the sum of the atmospheric inputs and contribution from soil phosphorus release.

Figure 8 Comparison of phosphorus inputs from substrate and the atmosphere. a, Rate of P loss from the soil as a whole (Fig. 3c) plotted with the long-term average addition of P in mineral aerosol. b, The per cent atmospheric contribution for each site calculated by dividing the atmospheric contribution by the sum of the atmospheric inputs and contribution from soil phosphorus release.

Figure 6 Map showing estimates of the long-term (integrated glacial plus interglacial) rate of dust deposition to the Pacific Ocean (from. ref. 58). The isopachs (mg m-2 yr-1) are based on models of atmospheric dust transport (58) and are in general agreement with data collected from numerous ocean cores (52). Chadwick et al. (1999)

Central Asian Dust Supplies Hawaiian Archipelago with PCentral Asian Dust Supplies Hawaiian Archipelago with P

Fall 2015:We did not cover the remaining 3 slides in this presentation

Concentration [~available] of rock-derived nutrients is high initially, but declines with soil age The concentration [& availability] of N increases through time

Vitousek and Farrington (1997)Biogeochemistry 37:63-75

+100 kg N ha-1 y-1

+100 kg P ha-1 y-1

Measured diameter growth of canopytrees

Ca and Mg additions did not Ca and Mg additions did not affect forest productivity at affect forest productivity at any siteany site