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not applied to stimulate short-term growth where crop production cycles span many decades, soil analyses are carried out to determine the medium- to long-term P supplying capacity of forest ecosystems. Hence, there is a need to review the currently available methods used to assess their limitations and advantages with regard to this objective. This review will consider a number of issues raised in the introduction, which will then lead to suggestions for the development of appropriate methods for future studies where medium- to long-term changes in the P status of forest soils are to be investigated. Labile organic P, microbial P Protected organic P Plant P Solution P Occluded inorganic P Labile inorganic P (readily available P) Moderately and sparingly soluble inorganic P Fig 11 : A conceptual model of phosphorus dynamics in forest soils Secondary mineral P primary mineral P 52
Table 8 : Sequential extraction procedure to define soil P fractionation and their lability with respect to P uptake (Modified from Hedley et al. 1982) Extraction step Lability and fractions 1. Resin Pi Labile - soluble and exchangeable 2. NaHCO3 Pi Labile - adsorbed 3. NaHCO3 Po Readily mineralisable 4. NaOH Pi Fe and Al – associated 5. NaOH Po Slowly mineralisable 6. IM HCl Pi Ca – associated 7. Conc. HCl Pi Occluded P and secondary mineral P 8. Residual P – Pi and Po Primary and secondary mineral P and organic P Table 9: Commonly employed soil test methods to determine available P Soil group Soil pH Most common P forms Available P methods Highly acid to 7.2 Ca-P, Mg-P Anion exchange resin, calcareous Olsen, lactate methods 3.2 Factors affecting P status of forest soils 3.2.1 P concentration in soil solution : the controlling component of P uptake Concentrations of about 1 mM P are commonly required in soil solution to supply P in adequate amounts to plants, however, P concentrations rarely exceed 10 µm (Bieleski, 1973). Moreover, P concentrations can vary over a wide range depending 53
Page 1 and 2: ASSESSMENT OF CHANGES IN THE PHOSPH
Page 3 and 4: RECOMMENDATIONS 1. The results of t
Page 5 and 6: EXECUTIVE SUMMARY 1. The first nati
Page 7 and 8: High N inputs and uptake by plants
Page 9 and 10: 12. It is recommended that a series
Page 11 and 12: Below, these hypotheses are being d
Page 13 and 14: Douglas fir which suffered from abs
Page 15 and 16: easons of such results. Another rea
Page 17 and 18: The frequency and the amount of mas
Page 19 and 20: usually present in the leaves. In v
Page 21 and 22: level class are given in brackets.
Page 23 and 24: 2.3 Factors influencing the foliage
Page 25 and 26: example the compiled data from BZE-
Page 27 and 28: mostly during periods of active gro
Page 29 and 30: Table 3: Number of cases included f
Page 31 and 32: P % 0.1 0.2 0.3 0.4 Kiefer 4 4,5 5
Page 33 and 34: P % 0.1 0.2 0.3 0.4 0.5 Eiche 4 4,5
Page 35 and 36: 19.84 n=144 NVHU< 1228 | CMENGE< 38
Page 37 and 38: 2.6 Changes in P concentrations in
Page 39 and 40: in section 1 of this report. In sum
Page 41 and 42: Fig 8: Mixed linear model describin
Page 43 and 44: Fig 10: . Mixed linear model descri
Page 45 and 46: Table 6: Concentration of P (mg/g)
Page 47 and 48: (Nilsen and Abrahmsen 2003) reporte
Page 49 and 50: 3. PHOSPHRUS IN FOREST SOILS 3.1 In
Page 51: sequential extraction scheme of ext
Page 55 and 56: phosphates at pH values
Page 57 and 58: 3.2.2 Inorganic forms of P - desorp
Page 59 and 60: Mineralisation of organic P does no
Page 61 and 62: enhances the dissolution of Ca-phos
Page 63 and 64: water, and sodium bicarbonate metho
Page 65 and 66: Table 10. Estimated transfers and c
Page 67 and 68: 3.3 Use of pedo-transfer functions
Page 69 and 70: the amount taken up at each site. T
Page 71 and 72: is commonly saturated with HCO3 is
Page 73 and 74: assess P status or any changes in P
Page 75 and 76: Forest Ecol. Manage. 92, 119-152. B
Page 77 and 78: Rev. Plant Physiol.Plant Mol. Biol.
Page 79 and 80: and N-free-fertilisation. Plant Soi
Page 81 and 82: Sparling GP, Hart PBS, August JA. (

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