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

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CONTENTS RECOMMENDATIONS………………………………………………………………………..……….3 EXECUTIVE SUMMARY………………………………………………………………………………5 1 INTRODUCTION..........................................................................................................................10 1.1 Changes in P supply in forest soils due to acidifying inputs. ...................................................11 1.2 Decrease in the decomposition of organically bound P and retention in the litterlayer under forests. ................................................................................................................................................15 1.3 Changes in the growth patterns of trees ...................................................................................16 1.4 Possible causal mechanisms of decrease in P status of trees....................................................17 2. PHOSPHORUS IN PLANT COMPONENTS ...............................................................................18 2.1 P in plants: role, uptake and distribution in trees .....................................................................18 2.2 Commonly used critical P-values for tree nutrition..................................................................19 2.3 Factors influencing the foliage P concentrations in trees .........................................................23 2.4 Analysis of van den Burg data sets for important German tree species........................................28 2.5 BZE 1 sites – Re-evaluation of data on foliage P and soil P parameters..................................33 2.6 Changes in P concentrations in the foliage and leaf litter during the last 10 years at Level II sites in Lower Saxony (NS)................................................................................................................37 2.7 Foliage analysis data from long term P fertilizer experiments.................................................45 2.8 Summary and Recommendations for use of foliar P concentrations........................................48 3. PHOSPHRUS IN FOREST SOILS................................................................................................49 3.1 Introduction..............................................................................................................................49 3.2 Factors affecting P status of forest soils...................................................................................53 3.2.1 P concentration in soil solution : the controlling component of P uptake.......................53 3.2.2 Inorganic forms of P - desorption and retention processes.............................................57 3.2.3 Organic P forms - mineralization and immobilization processes ...................................58 3.2.4 P uptake - Role of rhizosphere and mycorrhiza activities...............................................59 3.2.5 Use of soil tests – limitations and possibilities ...............................................................59 3.2.5 Soil P measurement by sequential fractionation.............................................................65 3.3 Use of pedo-transfer functions to assess availability and the amount of available soil P.........67 3.4 Suggested method to assess changes in P status of soils..........................................................68 3.5 Summary of P in Forest Soils...................................................................................................72 4. ACKNOWLEDGEMENTS............................................................................................................73 5. REFERENCES...............................................................................................................................74 2
RECOMMENDATIONS 1. The results of this study suggest that P nutrition appears to be a substantial problem in German forests, and the problem is becoming more severe in the main coniferous species, Picea abies and Pinus sylvestris. 2. Foliar P values depend upon a number of site and stand factors and one time sampling of stands during national forest soil surveys (BZE) may provide general trends at the population level, but otherwise has limited site specific information. 3. Repeated sampling at individual sites, when carried out over for a long time (data available for 10 years period on 27 monitoring sites of Lower Saxony), provided trends in foliar P levels, showing that P concentrations declined in pine and spruce, but were stable in beech. However, the data base was too small, of regional nature and covered only a restricted number of site and soil characteristics to extrapolate the results to a national level for predictions in foliar P status of forest stands. 4. To assess, whether a decline in P nutrition is a widespread phenomenon, or restricted to certain regions or site types, there is a need to carry out further evaluation of temporal dynamics in foliar P concentrations for other Level II sites in additional German States. These analysis should also include litter fall data from Level II sites across different German States. 5. There is a need to monitor changes in the amount of soil P available to trees in the medium- to long-term. 6. Presently available pedo-transfer functions in the literature to predict labile soil P fractions from total soil P values were developed on restricted soil types and cannot be used at an extensive scale of nationwide forest soil inventories. Moreover, P fractions representing different chemical (organic and inorganic) forms of P would not indicate small scale changes in labile P. We therefore recommend that this area of investigation should not be pursued further. 7. Methods employed to determine available soil P in agriculture were developed for specific purposes to make recommendation regarding fertilizer application rates. Their usefulness to assess medium- to long-term changes in the P status of forest soils is highly questionable, as has been demonstrated in many long-term monitoring experiments. They can however be employed to show comparative and short term changes in soil P status after silvicultural treatments (fertilization, fire, slash management). We do not recommend their use for soil samples from the nationwide forest soil inventory (BZE). 3
Page 1: ASSESSMENT OF CHANGES IN THE PHOSPH
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 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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