assessment of changes in the phosphorus status of forest ...

More documents

Recommendations

Info

of these compounds under such soil conditions. Only under very high acid soil conditions did these P forms show a high order of crystallinity as evidenced by their low (
Mineralisation of organic P does not follow the same pattern as N, whereas very little N is released during the initial phases of litter decomposition, causing the C:N ratio to increase in the decomposing litter, a significant amount of P is released, before it follows the same pattern of decomposition as for N. 3.2.4 P uptake - Role of rhizosphere and mycorrhiza activities Presence of mycorrhiza may facilitate the uptake of P under acidified rhizosphere conditions. Gillespie and Pope (1991) reported that P plant uptake rates were similar at both pH 4.0 and pH 7.0 by non-mycorrhizal black locust (Robinia pseudoacacia L.), whereas in plants with mycorrhizal associations, the rate of phosphorus uptake at pH 4.0 was twice that observed at pH 7.0. Depending on the soil type five-fold differences in the P diffusion rates were observed in the six forest soils using desorption-isotherm buffer power assays. There are many studies in this special area of research and the Mycorrhizal Information Exchange (MIE) website at the following address provides the pertinent literature (http://mycorrhiza.ag.utk.edu/). The following issues should be mentioned in the context of this review: 1. Phosphate uptake is a diffusion processes which occurs a few mm around the fine roots and mycorrhizal filaments, thus the rhizosphere play an important role in the amount of P taken up by plants. 2. A number of rhizosphere processes would affect the solubility of inorganic P, the most important ones are the changes in pH, exudation of inorganic acids by roots. 3. Mycorrhiza play an active role in the uptake of P by intensive exploring of soil volume, and through exudation of acids and enzymes. 4. Phosphate being an anion, other anions will compete with its uptake. Thus interactions with other ions in the rhizosphere are important determining factors for P uptake. 5. Fine roots and mycorrhiza are highly sensitive to acid conditions and high levels of nutrients in the soil. 3.2.5 Use of soil tests – limitations and possibilities Many chemical solutions are used to extract P from soils. With any extracting solution, four basic reactions are involved by which P is removed from the solid 59
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 and 52: sequential extraction scheme of ext
Page 53 and 54: Table 8 : Sequential extraction pro
Page 55 and 56: phosphates at pH values
Page 57: 3.2.2 Inorganic forms of P - desorp
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. (
show all

assessment of changes in the phosphorus status of forest ...

Create successful ePaper yourself

Delete template?

Save as template?