Methods: Details of the multivariate ANOVA in our study

As described in the text, two variables, identity of removed PFG and number of removed PFG, were treated as independent variables and removed biomass as a covariate in the multivariate ANOVA. Our model could be illustrated below. For simplicity, the replicates were not shown. In the column of “identity of removed PFG”, removal of a certain PFG was indicated as “0”, and “1” stood for no removal of this PFG. The number of removed PFG after removal of the PFG in the first column was indicated in the second column. The third column is the totally removed biomass in the plot. For a root or soil property (e.g. root biomass), five variables in the right of the table were the five dependent variables.

The root or soil properties, e.g. root biomass, soil nitrate etc
Identity of removed PFG / Number of removed PFG / Removed aboveground biomass / AB / PB / PF / PR / SS
0 / 1
0 / 2
0 / 3
0 / 4
0 / 5
1 / 0
1 / 1
1 / 2
1 / 3
1 / 4

The analysis of PFG identity and richness shown here has been used in another study, e.g. Olemann et al. (2007) (the same reference in the text) where effects of presence or absence of a PFG (similar to identity of PFG in our study) and PFG richness (similar to PFG richness in our study) were analyzed with a similar procedure (see the data analysis in Olemann’s study and figures therein)

Table S1 Protocol of plant functional group (PFG) removal. Abbreviations for the PFG are as follows: PR is perennial rhizome grass, PB is perennial bunchgrasses, PF is perennial forbs, SS is shrubs and sub-shrubs and AB is annuals and biennials

PFG
combinations / Number of removed PFG / Identity of removed PFG
PR / PB / PF / SS / AS / Replicate Projected / Replicates in practice
1 / 0 / 8 / 8
2 / 1 / × / 8 / 7
3 / 1 / × / 8 / 8
4 / 1 / × / 8 / 8
5 / 1 / × / 8 / 8
6 / 1 / × / 8 / 8
7 / 2 / × / × / 8 / 8
8 / 2 / × / × / 8 / 8
9 / 2 / × / × / 8 / 8
10 / 2 / × / × / 8 / 8
11 / 2 / × / × / 8 / 8
12 / 2 / × / × / 8 / 8
13 / 2 / × / × / 8 / 8
14 / 2 / × / × / 8 / 8
15 / 2 / × / × / 8 / 8
16 / 2 / × / × / 8 / 8
17 / 3 / × / × / × / 8 / 8
18 / 3 / × / × / × / 8 / 8
19 / 3 / × / × / × / 8 / 8
20 / 3 / × / × / × / 8 / 8
21 / 3 / × / × / × / 8 / 8
22 / 3 / × / × / × / 8 / 8
23 / 3 / × / × / × / 8 / 8
24 / 3 / × / × / × / 8 / 8
25 / 3 / × / × / × / 8 / 8
26 / 3 / × / × / × / 8 / 8
27 / 4 / × / × / × / × / 8 / 8
28 / 4 / × / × / × / × / 8 / 8
29 / 4 / × / × / × / × / 8 / 8
30 / 4 / × / × / × / × / 8 / 8
31 / 4 / × / × / × / × / 8 / 8
32 / 5 / × / × / × / × / × / 8 / 8

The symbol of “×” stands for the removal. Abbreviations for the PFG are: PR: perennial rhizome grass, PB: perennial bunchgrasses, PF: perennial forbs, SS: shrubs and sub-shrubs SS, AB: annuals and biennials

Table S2 Summary of the five plant functional group (PFG)

Plant functional group (PFG) / No. of species
per PFG / C:N in aboveground biomass / Aboveground biomass
(g m-2)
Perennial rhizome (PR) / 1 / 24.86 / 102.1
Perennial bunchgrass (PB) / 6 / 28.71 / 139.88
Perennial forbs (PF) / 17 / 19.63 / 40.43
Shrub or sub-shrub (SS) / 3 / 15.77 / 0.84
Annuals or biennials (AB) / 5 / 13.03 / 0.18

Table S3 Results of MANOVA for effects of identity and number of removed PFG and removed biomass on root P. Abbreviations of the PFG are the same as in table 1

df / Root P
F / P
Corrected model a / Removal of AB / 9 / 1.01 / 0.432
Removal of PB / 9 / 0.98 / 0.457
Removal of PF / 9 / 0.95 / 0.498
Removal of PR / 9 / 1.16 / 0.321
Removal of SS / 9 / 0.94 / 0.500

Note: F, F-values.

Significant effects (P0.05) are indicated in bold and non-significant effects are not shown.

a See Table 1 in the text for the corrected model

Table S4 Results of MANOVA for effects of identity and number of removed PFG and removed biomass on Soil NH4+, Soil TN, Soil TP and Soil AP. Abbreviations of the PFG are the same as in table 1

df / Soil NH4+ / Soil TN / Soil TP / Soil AP
F / P / F / P / F / P / F / P
Corrected model a / Removal of AB / 9 / 1.46 / 0.157 / 0.62 / 0.800 / 0.82 / 0.607 / 1.02 / 0.429
Removal of PB / 9 / 0.75 / 0.674 / 0.40 / 0.947 / 0.60 / 0.811 / 1.02 / 0.429
Removal of PF / 9 / 0.77 / 0.658 / 0.48 / 0.903 / 0.64 / 0.776 / 1.50 / 0.319
Removal of PR / 9 / 1.10 / 0.360 / 0.41 / 0.940 / 0.60 / 0.816 / 1.37 / 0.194
Removal of SS / 9 / 0.94 / 0.493 / 0.35 / 0.967 / 0.59 / 0.822 / 1.00 / 0.445

Note: F, F-values.

Significant effects (P0.05) are indicated in bold and non-significant effects are not shown.

Soil NH4+ is soil ammonium. Soil TN, soil TP and soil AP are total nitrogen, phosphorus and available phosphorus content in soil, respectively.

a See Table 1 in the text for the corrected model

Table S5 Results of MANOVA for effects removed aboveground biomass on root biomass, root N, root N pool, root P pool, soil NO3-, soil InN and Rmin

df / Root biomass / Root N / Root N pool / Root P pool
F / P / F / P / F / P / F / P
Removed biomass / Removal of AB / 9 / 8.52 / 0.004
Removal of PB / 9 / 0.29 / 0.591 / 1.46 / 0.228 / 0.07 / 0.799 / 0.40 / 0.528
Removal of PF / 9
Removal of PR / 9 / 8.53 / 0.004 / 21.49 / <0.001
Removal of SS / 9 / 4.34 / 0.038 / 15.26 / <0.001
df / Soil NO3- / Soil InN / Nmin
F / P / F / P / F / P
Removed biomass / Removal of AB / 9 / 65.74 / <0.001 / 59.33 / <0.001 / 42.72 / <0.001
Removal of PB / 9 / 15.9 / <0.001 / 13.12 / <0.001 / 45.56 / <0.001
Removal of PF / 9 / 44.53 / <0.001 / 36.90 / <0.001 / 65.39 / <0.001
Removal of PR / 9 / 36.87 / <0.001 / 30.98 / <0.001 / 44.16 / <0.001
Removal of SS / 9 / 40.63 / <0.001 / 33.37 / <0.001 / 39.72 / <0.001

Notes: The P and F values are shown only when the ‘corrected model’ in table 1, 2 and 3 in the text is significant (P0.05).

Soil NO3- and Soil InN is soil nitrate and soil inorganic nitrogen. Nmin is the net N mineralization rate.