## 3 Results
### Evaluation of the Differences and Similarities of Amendment Effects using PCA  
Figure 3a presents the plot of the different amendments with the first two principal components (PCs) of the PCA results obtained from soil microbial community variables. The cumulative % of the first two PCs was 80.1%, with PC1 68.5% and PC2 11.6% of the total variance. Microbial activity, microbial biomass C, dehydrogenase, cellulase and urease activities had large positive loading coefficients on PC1 (loading \(>0.7\)), while acid phosphatase had a large negative loading on PC1. The amended samples almost all located on the positive side of PC1, indicating higher microbial activity, microbial biomass C, dehydrogenase, cellulase and urease and lower acid phosphatase activities. In contrast, the control1 and control2 samples were positioned on the negative side of PC1, suggesting higher acid phosphatase and lower microbial activity, microbial biomass C, dehydrogenase, cellulase and  
Figure 2: Soil enzyme activities in the mine soil with different amendments (means \(\pm\) S.E, n = 4). The bars with different letters indicated significant differences at \(p<0.05\) according to LSD test. lime1 (25 t ha\({}^{-1}\)), lime2 (50 t ha\({}^{-1}\)), Rs (river sediment 30%, w:w); **(a)**: dehydrogenase activity; **(b)**: urease activity; **(c)**: cellulase activity; **(d)**: acid phosphatase activity  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**OM (g kg\({}^{-1}\))** & **TN (mg kg\({}^{-1}\))** & **TP (mg kg\({}^{-1}\))** & **TK (mg kg\({}^{-1}\))** \\ \hline
3.7 \(\pm\) 0.93c \({}^{*}\) & 72 \(\pm\) 3.6d & 276 \(\pm\) 2.9d & 183 \(\pm\) 2.7d \\
21 \(\pm\) 2.4b & 179 \(\pm\) 8.8c & 289 \(\pm\) 8.2d & 229 \(\pm\) 26d \\
21 \(\pm\) 0.76b & 235 \(\pm\) 7.9b & 297 \(\pm\) 10d & 286 \(\pm\) 24d \\
23 \(\pm\) 1.5b & 236 \(\pm\) 7.5b & 303 \(\pm\) 11d & 289 \(\pm\) 27d \\
23 \(\pm\) 1.4b & 232 \(\pm\) 6.2b & 359 \(\pm\) 11c & 386 \(\pm\) 28c \\
25 \(\pm\) 0.59 ab & 458 \(\pm\) 12a & 446 \(\pm\) 10b & 551 \(\pm\) 44 ab \\
25 \(\pm\) 1.7 ab & 487 \(\pm\) 35a & 423 \(\pm\) 14b & 630 \(\pm\) 52a \\
23 \(\pm\) 0.66b & 221 \(\pm\) 10b & 322 \(\pm\) 11 cd & 266 \(\pm\) 7.3d \\
27 \(\pm\) 1.4a & 237 \(\pm\) 6.3b & 326 \(\pm\) 5.3 cd & 262 \(\pm\) 6.2d \\
27 \(\pm\) 1.5a & 262 \(\pm\) 4.3b & 362 \(\pm\) 18c & 410 \(\pm\) 41c \\
28 \(\pm\) 2.0a & 478 \(\pm\) 5.3a & 418 \(\pm\) 8.0b & 525 \(\pm\) 14b \\
29 \(\pm\) 1.8a & 492 \(\pm\) 14a & 513 \(\pm\) 23a & 521 \(\pm\) 24b \\ \hline \hline \multicolumn{4}{l}{\({}^{*}\) Different letters in the same column indicated significant differences at \(p<0.05\) according to LSD test.} \\ \end{tabular}
\end{table}
Table 3: Nutrient elements in the mine soil with different amendments (means \(\pm\) S.E, n = 4).  
urease activities. The treatments with and without river sediment were also separated, suggesting that the combination of lime and river sediment had a greater effectiveness compared to the other treatments. As to the PCA for soil nutrient elements, the value of PC1 was 71.2% of the total variance and PC2 was 12.1% (Figure 3b). TN, NH4+-N, NO3-N, TP, AP and TK had large loading coefficients on PC1, all with positive values. The treatments with river sediment (lime1 + Rs, lime1 + NPK + Rs, lime2 + Rs, lime2 + NPK + Rs) are located on the right section of PC1; the treatments without river sediment (lime1, lime1 + NPK, lime1 + P, lime2, lime2 + NPK, lime2 + P) are in the central part of the diagram, whereas the two controls are positioned to the left. A separation between control1 and control2 is again attributed to the sawdust addition.