Table 6. Main environmental factors of eight locations throughout China.

Items	S1	S2	S3	S4	S5	S6	S7	S8
XN	6.31 ± 0.03 abcd	28.12 ± 0.02 cde	32.65 ± 0.04 abc	8.09 ± 0.07 ab	7.43 ± 0.04 abc	8.13 ± 0.03 abcd	32.21 ± 0.02 cde	35.82 ± 0.03 abc
XP	6.42 ± 0.06 ab	7.58 ± 0.05 a	8.56 ± 0.02 b	11.37 ± 0.15 de	8.25 ± 0.24 ab	7.24 ± 0.06 ab	8.85 ± 0.05 a	10.13 ± 0.02 b
XK	107.69 ± 0.02 cde	357.53 ± 0.04 e	96.71 ± 2.14 de	132.04 ± 4.30 e	160.41 ± 0.01 de	135.96 ± 0.02 cde	384.35 ± 0.03 e	112.71 ± 0.04 de
XOM	5.00 ± 0.01 bcde	6.52 ± 0.01 bcd	5.40 ± 0.01 b	10.02 ± 0.06 de	6.38 ± 0.03 cde	4.09 ± 0.01 bcde	7.22 ± 0.03 bcd	6.50 ± 0.01 b
XTN	0.23 ± 0.02 e	0.25 ± 0.001 bc	0.20 ± 0.004 e	0.29 ± 0.005 de	0.32 ± 0.004 e	0.17 ± 0.001 e	0.33 ± 0.001 bc	0.16 ± 0.005 e
XTP	0.03 ± 0.001 ab	0.11 ± 0.002 cde	0.14 ± 0.003 e	0.21 ± 0.005 bc	0.05 ± 0.001 de	0.02 ± 0.001 ab	0.15 ± 0.002 cde	0.32 ± 0.003 e
XTK	2.45 ± 0.01 e	1.49 ± 0.02 de	1.62 ± 0.04 de	1.77 ± 0.03 abc	2.46 ± 0.05 e	2.60 ± 0.01 e	1.56 ± 0.02 de	2.35 ± 0.04 de
XpH	6.20 ± 0.05 abc	7.31 ± 003 bcd	6.59 ± 0.05 cde	6.39 ± 0.07 cde	6.12 ± 0.06 abcd	6.40 ± 0.05 abc	7.09 ± 003 bcd	6.20 ± 0.05 cde
XAMT	7.00 ± 0.05 ab	6.90 ± 0.08 d	6.40 ± 0.04 e	4.32 ± 0.02 e	6.80 ± 0.05 cde	9.00 ± 0.05 ab	6.90 ± 0.08 d	7.60 ± 0.04 e
X1	−7.0 ± 0.01 bcd	−4.0 ± 0.04 abcd	−8.2 ± 0.02 de	−7.6 ± 0.05 bcd	−2.2 ± 0.04 bcd	−5.6 ± 0.01 bcd	1.5 ± 0.03 abcd	−5.0 ± 0.02 de
X7	19.0 ± 0.01 abc	22.5 ± 0.07 ab	23.4 ± 0.03 bcd	21.7 ± 0.04 d	15.5 ± 0.01 ab	13.4 ± 0.02 abc	16.3 ± 0.03 ab	16.8 ± 0.05 bc
XAAT	1847.43 ± 0.03 bc	2390.80 ± 0.05 ab	3643.87 ± 0.06 c	4108.22 ± 0.04 bcd	1265.20 ± 0.04 bcde	1526.70 ± 0.03 bc	2263.20 ± 0.05 ab	1931.52 ± 0.03 bcd
XAHT	40.44 ± 0.08 cd	32.80 ± 0.04 bc	39.50 ± 0.01 abc	35.00 ± 0.03 ab	31.70 ± 0.01 cd	24.60 ± 0.04 cd	30.60 ± 0.05 bc	33.90 ± 0.02 abc
XALT	−24.00 ± 0.04 de	−25.50 ± 0.06 d	−26.62 ± 0.03 bcd	−24.24 ± 0.01 bc	−28.91 ± 0.04 abc	−23.40 ± 0.04 de	−14.4 ± 0.02 d	−20.30 ± 0.03 bcd
XAAP	616.32 ± 0.01 abc	635.44 ± 0.04 bc	620.30 ± 0.04 abc	530.27 ± 0.06 cde	880.30 ± 0.04 ab	627.20 ± 0.01 abc	650.45 ± 0.04 bc	642.41 ± 0.06 abc
XASD	2370.12 ± 0.04 ab	2021.35 ± 0.07 bcde	1226.55 ± 0.03 bc	2659.62 ± 0.06 abc	1738.34 ± 0.03 a	2206.40 ± 0.04 ab	2020.53 ± 0.07 bcde	2246.20 ± 0.01 bc
XFFP	132.61 ± 15.38 abc	158.00 ± 9.66 a	230.54 ± 11.55 ab	121.52 ± 8.12 abc	180.00 ± 1.23 a	167.00 ± 15.38 abc	180.00 ± 9.66 a	147.35 ± 11.55 ab
XALTI	2061.25 ± 36.55 a	2747 ± 87.32 c	2800 ± 56.72 c	2311.5 ± 23.65 b	2525.25 ± 121.66 b	3200 ± 67.54 d	3345.25 ± 210.4 d	3373.75 ± 121.41 d

Eighteen environmental factors were performed in the Table 1. For the same variable, values with no letters in common are significantly different (P < 0.05).