Response of soil properties and C dynamics to land-use change in the west of Loess Plateau

Figures & data

Table 1 Description of different land use types

Land use	Age (year)	Prior land use	Management practices	Source of disturbances
DG			No management	Sheep
AL	50	DG	Tillage, irrigation and fertilization	Farmer
AG	9	AL	Irrigation and cutting	Farmer
AAL	6	AL	No management	Wildlife
AW	17	DG	Irrigation	Wildlife

AL: arable land; AG: artificial grassland; AAL: abandoned arable land; AW: artificial woodland; DG: desert grassland.

Figure 1 Location of the study area and sample scheme of different land uses.

Table 2 Some soil properties as affected by land use change in the west of Loess Plateau.

	Bulk density	θw		EC	TN
Land use	g cm^−3	%	pH	ms cm^−1	g kg^−1	C/N
0–10 cm
AL	1.15 ± 0.03 a	21.73 ± 0.63 b	8.95 ± 0.04 a	0.24 ± 0.02 a	0.75 ± 0.02 b	8.05 ± 0.06 a
AG	1.21 ± 0.05 a	16.79 ± 1.60 a	9.05 ± 0.02 ab	0.13 ± 0.01 a	0.93 ± 0.03 c	8.60 ± 0.14 a
AAL	1.26 ± 0.06 a	14.65 ± 1.24 a	9.38 ± 0.21 b	0.14 ± 0.05 a	0.85 ± 0.02 bc	8.57 ± 0.38 a
AW	1.20 ± 0.07 a	16.14 ± 1.43 a	9.03 ± 0.10 a	0.22 ± 0.07 a	0.54 ± 0.07 a	8.08 ± 0.33 a
DG	1.17 ± 0.01 a	13.62 ± 0.22 a	9.24 ± 0.04 ab	0.15 ± 0.02 a	0.71 ± 0.06 b	8.01 ± 0.22 a
10–20 cm
AL	1.21 ± 0.09 a	20.59 ± 0.62 b	9.05 ± 0.06 a	0.19 ± 0.02 ab	0.70 ± 0.01 b	7.99 ± 0.08 ab
AG	1.31 ± 0.04 a	16.17 ± 0.88 ab	9.15 ± 0.02 a	0.14 ± 0.02 a	0.68 ± 0.03 b	8.17 ± 0.17 ab
AAL	1.26 ± 0.04 a	12.09 ± 1.99 a	9.13 ± 0.03 a	0.18 ± 0.02 ab	0.73 ± 0.03 b	8.37 ± 0.19 b
AW	1.22 ± 0.05 a	13.95 ± 1.21 a	8.90 ± 0.22 a	0.38 ± 0.15 b	0.46 ± 0.10 a	7.56 ± 0.4 ab
DG	1.13 ± 0.06 a	10.47 ± 1.32 a	9.21 ± 0.04 a	0.39 ± 0.03 b	0.65 ± 0.09 ab	7.48 ± 0.24 a
20–40 cm
AL	1.42 ± 0.03 b	17.89 ± 0.22 b	9.16 ± 0.01 b	0.16 ± 0.01 a	0.60 ± 0.05 b	7.63 ± 0.10 ab
AG	1.24 ± 0.03 ab	15.61 ± 0.82 b	9.19 ± 0.04 b	0.13 ± 0.01 a	0.54 ± 0.06 b	7.45 ± 0.25 ab
AAL	1.18 ± 0.04 a	11.05 ± 1.36 ab	9.04 ± 0.14 ab	0.22 ± 0.05 a	0.62 ± 0.04 b	8.06 ± 0.38 b
AW	1.22 ± 0.12 ab	12.77 ± 1.18 ab	8.85 ± 0.13 a	0.56 ± 0.17 b	0.33 ± 0.08 a	7.06 ± 0.06 a
DG	1.13 ± 0.05 a	7.07 ± 0.53 a	8.96 ± 0.04 ab	1.02 ± 0.14 c	0.57 ± 0.05 b	7.42 ± 0.24 ab
40–60 cm
AL	1.16 ± 0.04 a	19.78 ± 0.81 c	9.20 ± 0.01 b	0.18 ± 0.00 a	0.54 ± 0.06 a	7.27 ± 0.04 a
AG	1.19 ± 0.04 a	14.67 ± 1.54 bc	9.23 ± 0.03 b	0.15 ± 0.01 a	0.52 ± 0.09 a	7.26 ± 0.29 a
AAL	1.17 ± 0.03 a	10.35 ± 1.06 ab	9.12 ± 0.10 b	0.19 ± 0.03 a	0.51 ± 0.04 a	7.87 ± 0.06 b
AW	1.22 ± 0.05 a	8.98 ± 1.58 ab	8.83 ± 0.12 a	0.79 ± 0.21 b	0.34 ± 0.09 a	7.09 ± 0.21 a
DG	1.16 ± 0.06 a	6.89 ± 0.47 a	9.03 ± 0.10 ab	1.27 ± 0.09 c	0.43 ± 0.02 a	6.77 ± 0.10 a
60–80 cm
AL	1.24 ± 0.02 b	19.25 ± 0.54 b	9.25 ± 0.03 b	0.18 ± 0.01 a	0.47 ± 0.04 a	6.71 ± 0.15 ab
AG	1.20 ± 0.04 ab	12.41 ± 1.49 ab	9.29 ± 0.04 b	0.17 ± 0.01 a	0.50 ± 0.14 a	7.21 ± 0.41 ab
AAL	1.25 ± 0.02 b	9.78 ± 1.77 a	9.20 ± 0.07 b	0.18 ± 0.02 a	0.44 ± 0.04 a	7.27 ± 0.10 b
AW	1.25 ± 0.02 b	7.26 ± 0.99 a	8.90 ± 0.11 a	0.73 ± 0.15 b	0.32 ± 0.08 a	6.55 ± 0.19 a
DG	1.14 ± 0.04 a	6.20 ± 0.50 a	9.09 ± 0.10 ab	1.43 ± 0.21 c	0.38 ± 0.02 a	6.90 ± 0.08 ab
80–100 cm
AL	1.27 ± 0.02 a	17.50 ± 1.18 b	9.24 ± 0.00 b	0.22 ± 0.03 a	0.42 ± 0.05 a	6.58 ± 0.06 a
AG	1.21 ± 0.05 a	10.85 ± 1.36 ab	9.31 ± 0.09 b	0.19 ± 0.03 a	0.43 ± 0.13 a	7.05 ± 0.40 a
AAL	1.25 ± 0.02 a	9.29 ± 1.54 ab	9.25 ± 0.04 b	0.18 ± 0.02 a	0.39 ± 0.02 a	7.26 ± 0.07 a
AW	1.23 ± 0.02 a	6.74 ± 0.82 a	8.99 ± 0.13 a	0.70 ± 0.07 b	0.33 ± 0.07 a	6.71 ± 0.40 a
DG	1.19 ± 0.03 a	5.29 ± 0.68 a	9.29 ± 0.00 b	1.24 ± 0.08 c	0.32 ± 0.01 a	6.46 ± 0.11 a
Analysis of variance (ANOVA) summary (P values)
Land use (L)	*	***	***	***	***	***
Depth (D)	NS	***	0.06	***	***	***
L × D	NS	NS	NS	***	NS	NS

Different letters indicate significant difference (P < 0.05) among land uses. Each value represents mean (n = 3) ± SE. AL: arable land; AG: artificial grassland; AAL: abandoned arable land; AW: artificial woodland; DG: desert grassland. θw: soil water content; EC: electronic conductivity; TN: total nitrogen content; C/N: ratio of SOC: Total N. SE: standard error; NS: not significant. *P < 0.05; **P < 0.01; ***P < 0.001.

Figure 2 Soil particle size distribution in the profiles among the different land-use changes of arable land (AL), artificial grassland (AG), abandoned arable land (AAL), artificial woodland (AW) and desert grassland (DG).

Figure 3 Soil organic carbon content in the profiles among the different land-use changes of arable land (AL), artificial grassland (AG), abandoned arable land (AAL), artificial woodland (AW) and desert grassland (DG). Different lower case letters indicate significant difference (p<0.05) among land uses.

Figure 4 Particulate organic carbon (POC) and POC:SOC ratio in the profiles among the different land-use changes of arable land (AL), artificial grassland (AG), abandoned arable land (AAL), artificial woodland (AW) and desert grassland (DG). Different lower case letters indicate significant difference (p<0.05) among land uses.

Figure 5 Labile organic carbon (LOC) and LOC:SOC ratio in the profiles among the different land-use changes of arable land (AL), artificial grassland (AG), abandoned arable land (AAL), artificial woodland (AW) and desert grassland (DG). Different lower case letters indicate significant difference (p<0.05) among land uses.

Figure 6 Biplot of PC1 (40.3% of the variation) and PC2 (25.0% of the variation) separating five land use types (AL, arable land; AG, artificial grassland; AAL, abandoned arable land; AW, artificial woodland; DG, desert grassland) using eight soil variables (0–10 cm depth). The variables that each principal component (PC) represents are given in Table 3.

Table 3 Variable loading coefficients (eigenvectors) for the first four principal components (PC) for nine soil variables (0–10 cm layer) from the principal component analysis (PCA) of the standardized values (correlation matrix), and their individual and cumulative percentage of total variance explained by each PC and eigenvalues

Soil property	PC1	PC2	PC3	PC4
TN	0.98	−0.06	−0.11	0.08
SOC	0.98	−0.09	−0.02	0.08
LOC	0.90	0.04	0.33	0.03
θw	0.15	0.89	−0.002	−0.04
pH	0.27	−0.86	−0.20	0.05
EC	−0.58	0.66	−0.30	0.09
POC	0.20	0.08	0.97	0.12
Bulk density	0.20	−0.06	0.12	0.97
Eigenvalue	3.2	2.0	1.2	1.0
Proportion of variance (%)	40.3	25.0	15.0	12.3
Cumulative variance (%)	40.3	65.3	80.3	92.6

SOC: soil organic carbon; LOC: labile organic carbon; TN: total nitrogen content; EC: electronic conductivity; θw: soil water content; POC: particulate organic carbon. Boldface eigenvectors are considered highly loaded.