| |
Year
|
CK
|
N
|
P
|
NP
|
|---|
|
Available C&N&P
|
|
DOC (mg·kg− 1)
|
2014
|
299.2 ± 8.3 a
|
281.6 ± 6.1 a
|
310.4 ± 19.1 a
|
314.1 ± 28.3 a
|
|
2015
|
294.8 ± 2.8 b
|
288.9 ± 5.5 b
|
316.0 ± 3.1 a
|
324.3 ± 5.3 a
|
|
MBC (mg·kg− 1)
|
2014
|
571.7 ± 3.8 a
|
557.1 ± 3.5a
|
589.3 ± 2.9 a
|
588.2 ± 19.6 a
|
|
2015
|
563.4 ± 15 ab
|
545 ± 10.3 b
|
593.2 ± 4.8 a
|
587.0 ± 1.7 a
|
|
NH4+ (mg·kg− 1)
|
2014
|
8.1 ± 0.2 b
|
10.9 ± 0.6 a
|
6.8 ± 0.1 b
|
7.4 ± 0.5 b
|
|
2015
|
7.7 ± 0.1 a
|
8.7 ± 0.6 a
|
6.7 ± 0.1 b
|
8.1 ± 0.03 a
|
|
NO3− (mg·kg− 1)
|
2014
|
38.4 ± 0.9 b
|
42.4 ± 1.1 a
|
35.0 ± 0.3 c
|
37.1 ± 0.9 bc
|
|
2015
|
40.6 ± 0.1 b
|
48.1 ± 2.3 a
|
36.9 ± 0.3 b
|
41.6 ± 0.7 b
|
|
AP (mg·kg− 1)
|
2014
|
27.5 ± 8.4 b
|
24.8 ± 4.3 b
|
149.3 ± 11.9 a
|
150.6 ± 21.4 a
|
|
2015
|
29.3 ± 3.6 b
|
22.3 ± 4.1 b
|
139.4 ± 12.8 a
|
131.9 ± 9.8 a
|
|
Soil cations
|
|
Soil pH
|
2014
|
4.7 ± 0.04 a
|
4.5 ± 0.07 a
|
4.6 ± 0.03 a
|
4.5 ± 0.1 a
|
|
2015
|
4.6 ± 0.08 a
|
4.2 ± 0.04 b
|
4.4 ± 0.1 b
|
4.3 ± 0.01 b
|
|
Al3+ (mmol·kg− 1)
|
2014
|
38.0 ± 1.0 c
|
50.2 ± 1.0 a
|
42.4 ± 0.8 b
|
44.8 ± 0.9 b
|
|
2015
|
38.4 ± 3.2 c
|
60.4 ± 0.4 a
|
48.7 ± 0.8 b
|
61.0 ± 1.4 a
|
|
Ca2+ (mmol·kg− 1)
|
2014
|
33.6 ± 3.1 a
|
25.1 ± 1.8 b
|
28.8 ± 0.3 ab
|
25.0 ± 0.7 b
|
|
2015
|
30.3 ± 2.9 a
|
20.1 ± 0.5 c
|
26.0 ± 0.2 ab
|
22.6 ± 0.5 bc
|
|
Mg2+ (mmol·kg− 1)
|
2014
|
4.7 ± 0.4 a
|
4.3 ± 0.2 a
|
4.2 ± 0.4 a
|
4.2 ± 0.1 a
|
|
2015
|
4.2 ± 1.0 a
|
3.5 ± 0.6 a
|
3.7 ± 0.1 a
|
3.3 ± 0.1 a
|
|
Na2+ (mmol·kg− 1)
|
2014
|
1.5 ± 0.2 a
|
1.4 ± 0.04 a
|
1.3 ± 0.3 a
|
1.3 ± 0.2 a
|
|
2015
|
1.2 ± 0.2 a
|
1.3 ± 0.4 a
|
1.2 ± 0.1 a
|
1.2 ± 0.1 a
|
|
Plant
|
|
Fine root biomass (g·m− 2)
|
2014
|
172.2 ± 1.3 a
|
147.4 ± 4.0 c
|
161.9 ± 0.7 b
|
152.2 ± 1.5 c
|
|
2015
|
178.9 ± 1.9 a
|
142.6 ± 1.7 d
|
159.7 ± 1.4 b
|
148.6 ± 1.2 c
|
- Notes: Values are means with SE. The different lowercase letters in the same row indicate significant differences among the four treatments at P < 0.05 level. CK, control; N, nitrogen addition; P, phosphorus addition; NP, nitrogen and phosphorus addition
