## 3 Results  
Generally, transformation of land-use has a great impact on the soil microbial community structure. The change of total microorganisms in soil is generally indicated by the content of total PLFA in rhizosphere soil. The total PLFAs shown in Table 2 confirm that the soil had a higher PLFA biomass after planting _E.purpurea_, and the total amount of microorganisms in the soil changed significantly. Compared with the soil in which _E.purpurea_ was not planted, the total amount of PLFAs was obviously higher, with an average increase of approximately 70.90% (_p_ < 0.01). After planting _E.purpurea_, the Shannon-Wiener diversity index was mainly stable at 2.62 during the period of 0-150 days. Planting _E.purpurea_ did not significantly change microbial diversity of heavily PAH-contaminated soil (_p_ > 0.05). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{6}{c}{**Biomarkers in Soil in Different Periods before and after _E.purpurea_ Planting (nmol/g)**} \\ \hline
**Planting Period (d)** & **0** & \multicolumn{2}{c}{**60**} & \multicolumn{2}{c}{**120**} & \multicolumn{2}{c}{**150**} \\ \hline  & **C** & **S** & **C** & **S** & **C** & **S** & **C** & **S** \\ \hline ACT & 1.18 (a) & 0.54 (a) & 0.96 (a) & 0.40 (a) & 1.00 (a) & 1.20 (b) & 0.82 (a) & 1.39 (a) \\ SD & 0.15 & 0.07 & 0.18 & 0.10 & 0.07 & 0.43 & 0.16 & 0.3 \\ G+ & 4.34 (ac) & 2.27 (ac) & 3.20 (ac) & 1.76 (ac) & 3.59 (ac) & 6.40 (ac) & 2.95 (ac) & 8.27 (ac) \\ SD & 0.90 & 0.37 & 0.73 & 0.01 & 0.09 & 0.10 & 0.22 & 5.21 \\ G\(-\) & 9.42 (ac) & 5.82 (ac) & 7.21 (ac) & 4.86 (ac) & 8.14 (ac) & 13.11 (bd) & 7.43 (ac) & 13.53 (ac) \\ SD & 2.37 & 0.84 & 1.72 & 0.03 & 0.62 & 0.23 & 0.45 & 3.17 \\ BAC & 16.38 (ac) & 10.13 (ac) & 12.70 (ac) & 8.55 (ac) & 14.12 (ac) & 20.00 (bc) & 12.43 (ac) & 27.22 (ac) \\ SD & 3.53 & 1.32 & 2.56 & 0.004 & 0.77 & 0.12 & 0.74 & 7.49 \\ FUN & 2.25 (ac) & 1.20 (ac) & 1.70 (ac) & 0.93 (ad) & 1.76 (ac) & 2.47 (bd) & 1.47 (ac) & 2.36 (ac) \\ SD & 0.60 & 0.20 & 0.38 & 0.009 & 0.07 & 0.07 & 0.14 & 0.51 \\ AMF & 0.28 (a) & 0.15 (a) & 0.17 (a) & 0.11 (a) & 0.33 (a) & 0.47 (b) & 0.31 (a) & 0.46 (a) \\ SD & 0.07 & 0.01 & 0.03 & 0.0003 & 0.004 & 0.01 & 0.03 & 0.12 \\ B/F & 7.35 (a) & 8.47 (a) & 7.51 (a) & 9.29 (a) & 8.06 (a) & 8.55 (a) & 8.43 (a) & 9.65 (a) \\ SD & 0.41 & 0.32 & 0.45 & 0.11 & 0.08 & 0.22 & 0.32 & 1.69 \\ G\(-\)/G+ & 2.16 (a) & 2.57 (a) & 2.28 (a) & 2.78 (a) & 2.27 (a) & 2.14 (b) & 2.53 (a) & 2.13 (b) \\ SD & 0.23 & 0.14 & 0.38 & 0.05 & 0.11 & 0.07 & 0.03 & 0.07 \\ TOT & 29.72 (a) & 18.22 (a) & 22.72 (a) & 13.38 (a) & 26.69 (a) & 46.14 (b) & 24.31 (a) & 41.07 (a) \\ SD & 7.07 & 2.90 & 4.99 & 0.10 & 1.52 & 0.61 & 1.66 & 10.80 \\ \hline \hline \end{tabular} \(C\), not planted; S, planted; ACT, actinoryotes; G\({}_{+}\), Gram-positive bacteria; G\({}_{-}\), Gram-negative bacteria; BAC, bacteria; FUN, fungi; AMF, arbuscular mycorrhizal fungi; G+/G\({}_{-}\), ratio of Gram-negative to Gram-positive biomarkers; B/F, ratio of bacterial to fungal biomarkers; TOT, total average PLGA biomass; SD, standard deviation. Different letters represent the difference between samples in the same period (_p_ < 0.05). The first letter is the identification of the difference between the two groups of samples in the same period. The second letter is the identification of the difference between the same group of samples in different periods.  
\end{table} 
Table 1: Biomarker concentrations in soil at 0, 60, 120, and 150 days before and after planting _E.purpurea_ Planting (nmol/g)**The characteristic PLFAs were as follows: (1) actinomycetes (ACT): 16:0 10-methyl and 18:0 10-methyl; (2) Gram-positive bacteria (G+): 14:0 iso, 15:0 iso, 16:0 iso, 17:0 iso, 17:0 anteiso, 15:0 anteiso; (3) Gram-negative bacteria (G\(-\)): 16:1 w7c, 18:1 w7c, 17:1 w8c; (4) bacteria (BAC): Gram-positive and Gram-negative biomarkers, 14:0, 15:0, 17:0, 18:0, 16:0, 18:1 w7c 10-methyl, 17:1 iso w9c, 19:0 cyclo w7c, 17:0 cyclo w7c; (5) fungi (FUN): 18:1w9c, 18:2w6c; and (6) arbuscular mycorrhizal fungi (AMF): 16:1w5c.