Fig 1.
Location of the Wuliwan catchment in Loess Plateau of China and the sampling process.
The map was plotted by Arcgis9.3.
Fig 2.
Chronology and land use history of the sample site.
RP, CK, AB and SC represent Robinia pseudoacacia L. land, Caragana korshinskii Kom. Land, abandoned cropland and slop cropland, respectively, same in the rest figures.
Table 1.
General situation of the sample plots.
Table 2.
Correction factors for SOC analysis.
Fig 3.
Soil contents of SOC, TN, and TP for different land use types and soil depth in 2009, 2011, and 2013.
Bars represent standard errors.
Fig 4.
Soil storage of SOC, TN, and TP of different land use types and soil depth in 2009, 2011, and 2013.
Columns with different capital letters indicate significantly difference among different soil depth in same land use types; columns with different small letters indicate significantly different of among different land use types in same soil depth. All significances are been tested at P<0.05 level of probability. Error bars represent standard errors.
Fig 5.
Principal component analysis (PCA) loadings for the soil SOC, TN and TP storage samples.
Symbols with different shape represent different land use types: triangle is RP, square is CK, roundness is AB and cross is SC. Symbol with different color represent different soil depth: red for 0–20cm, blue for 20–40cm and green for 40–60cm. The ellipse is the approximate group of samples.
Table 3.
ANOSIM R-values of SOC, TN and TP storagesa.
Fig 6.
Stratification ratios of SOC, TN, and TP of different land use types and soil depth in 2009, 2011, and 2013.
Abscissa and ordinate value is the stratification ratios of each symbol in 0–20:20–40cm and 0–20:40–60cm, respectively. Symbols with different shape represent different land use types: roundness is RP, square is CK, rhomb is AB and triangle is SC. Symbol with different color represent different experiment year: red for 1999, green for 2011 and blue for 2013. Bars across the symbol represent standard errors. Cross LSD shows its magnitude (at P < 0.05 or 0.01) in horizontal and vertical to compare means for stratification ratios of different land use types and years in 0–20:20–40cm and 0–20:40–60cm.
Fig 7.
Principal component analysis (PCA) loadings for SR of soil SOC, TN and TP samples.
Symbols with different shape represent different land use types: triangle is RP, square is CK, roundness is AB and cross is SC. Symbol with different color represent different soil depth: blue for 0–20:20–40cm and green for 0–20: 40–60cm.
Table 4.
R-value for ANOSIM of SRs of SOC, TN and TPa.
Table 5.
Correlations between storage and SR of SOC, TN and TP.
Cor. (Sig.) is short for correlation coefficient (significance). **represent significant at P<0.01 level; * represent significant at P<0.05 level; NS represent no significant correlation.