The amount, quality and turnover of soil P is heavily influenced by changes
in soil management. The objective of this study was to investigate the eff
ects of deforestation and pasture establishment on the concentrations, form
s and turnover rate of soil P in mountain soils of the Alay Range, Khyrgyzi
a. A sequential extraction was applied to distinguish soil P pools. We used
particle-size fractionation to follow the dynamics of different P pools in
soils under forest and pasture and P-31-NMR spectroscopy to investigate th
e structure of alkali-soluble P forms. In the A horizons of the forest soil
s, total soil P concentration was 1093 mg kg(-1), organic P (P-o) represent
ing 46% of the total P. Deforestation followed by pasture establishment not
only increased significantly (P<0.01) the total P concentration (1560 mg k
g(-1)) but also the contribution of P-o to total P was increased by 17%. Pa
sture soils had significantly higher P pools than forest soils except highl
y labile inorganic P (P-i NaHCO3) and primary P-i (P-i HCldil) Both in fore
st and pasture soils stable P increased with decreasing particle size (coar
se sand 50%, clay 80% of total P) and primary P decreased with decreasing p
article size. Phosphate monoesters and diesters represented 80% of P identi
fied by P-31 NMR. Low monoester to diester ratios in the alkali extracts of
forest and pasture soils indicate low microbial activity. This is consiste
nt with high C/P-o ratios and high stable P-o concentrations in the fine ea
rth of forest and pasture.