## 3 Results
### Chemical and NIRS Analyses  
Refuse pile samples of _P. fallax_ were different from the nest's interior soil and from the surrounding soil. However, the interior nest soil did not differ from the control soil. The contents of N, P, K, Mg, and OM were significantly higher in soils from the refuse piles, where the pH was 14 to 70% greater than that of the control soil. Likewise, refuse piles had lower pH levels and lower Ca contents than control soils, with a significant difference only for pH levels (Table 2).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Site** & \(n\) & **Seeds (g)** & **AD (g)** & **OAD (g)** & \(p\)**-Value** \\ \hline
16 years & 15 & 0.27 a & 0.36 b & 0.03 b & 0.001 \\  & & _0.09_ & _0.07_ & _0.01_ & \\
20 years & 15 & 0.41 a & 0.64 a & 0.12 b & 0.001 \\  & & _0.20_ & _0.21_ & _0.03_ & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mean and standard error (SE, given in italics) of organic debris found in refuse piles of _P. fallax_ determined by the Kruskal–Wallis test and post hoc comparisons using the Dunn test. Different letters denote statistically significant differences between study sites. \(n\) = number of nests; AD = arthropod debris; OAD = other animal debris.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Refuse Pile**} & \multicolumn{2}{c}{**Nests**} & \multicolumn{2}{c}{**Control Soil**} & \multicolumn{2}{c}{**Increase/Decrease**} \\  & **Mean** & **SE** & **Mean** & **SE** & **Mean** & **SE** & **P** & \\ \hline pH & 6.70 a & 0.17 & 7.83 b & 0.15 & 7.84 b & 0.06 & \textless{}0.01 & \(\downarrow\) & 14.54 \\ OM (\%) & 9.36 a & 1.30 & 3.32 b & 0.10 & 3.28 b & 0.31 & \textless{}0.01 & \(\uparrow\) & 64.96 \\ N (\%) & 0.98 a & 0.29 & 0.30 b & 0.10 & 0.29 b & 0.07 & \textless{}0.01 & \(\uparrow\) & 70.41 \\ P (ppm) & 132.29 a & 7.85 & 46.54 b & 9.31 & 54.11 b & 13.03 & \textless{}0.01 & \(\uparrow\) & 59.10 \\ Ca (meq) & 39.19 a & 7.28 & 56.60 b & 8.53 & 54.6 b & 8.31 & & \\ Mg (meq) & 10.13 a & 1.14 & 4.28 b & 0.19 & 4.36 b & 0.25 & \textless{}0.01 & \(\uparrow\) & 56.96 \\ K (meq) & 5.43 a & 0.31 & 2.46 b & 0.16 & 2.53 b & 0.25 & \textless{}0.01 & \(\uparrow\) & 53.41 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical properties (mean and standard error, SE) of soils collected from _P. fallax_ (\(n\) = 7) nests, refuse piles, and control soil from rehabilitated sites of the Cerrejón mine, located in La Guajira, Colombia. The Kruskal–Wallis test was performed, along with post hoc comparisons using the Dunn test. An increase or decrease in the values for refuse piles (RP) with respect to the control soil (CS) is indicated as a percentage and with arrows.  
Figure 2: Biomass (g) of three item types found in 15 coal mine refuse piles colonized by _P. fallax_ in 16-year and 20-year rehabilitated sites of the Cerrejón mine in La Guajira, Colombia. AD = arthropod debris; OAD = other animal debris.  
A separation of the refuse piles from the control and nest soils was observed in the PCA results (Figure 3). However, in this case, the NIRS analyses distinguished nest soils from control soils (the barycenters are separated). The first component (21.3% variance explained) separated the sampling plots and showed high variability, while the second component (12.3% variance explained) distinguished the soil's origin. The refuse piles formed a separate group (_p_ < 0.01, 3.5% variance explained by the Monte Carlo test) (Figure 3).