# Diagnosing Phosphorus Limitation in Subtropical Forests in China under Climate Warming
## 2 Materials and Methods
### Methods
#### 2.3.4. Field Sampling  
The field investigations were conducted in July 2018 in Shennongjia, Qian Yanzhou, Mt. Gongga and Dinghushang. The locations of the forest sites, including Shennongjia (109\({}^{\circ}\)59\({}^{\prime}\)-ll0\({}^{\circ}\)58\({}^{\prime}\) E, 3l\({}^{\circ}\)15\({}^{\prime}\)-3l\({}^{\circ}\)57\({}^{\prime}\) N), Mt. Gongga (29\({}^{\circ}\)20\({}^{\prime}\)-30\({}^{\circ}\)20\({}^{\prime}\) N, 101\({}^{\circ}\)30\({}^{\prime}\)-102\({}^{\circ}\)15\({}^{\prime}\) E), Dinghushang (23\({}^{\circ}\)09\({}^{\prime}\)-23\({}^{\circ}\)11\({}^{\prime}\) N, 112\({}^{\circ}\)31\({}^{\prime}\)-112\({}^{\circ}\)34\({}^{\prime}\) E) and Qian Yanzhou (26\({}^{\circ}\)12\({}^{\prime}\)-26\({}^{\circ}\)34\({}^{\prime}\) N, 115\({}^{\circ}\)10\({}^{\prime}\)-115\({}^{\circ}\)23\({}^{\prime}\) E), are shown in Figure 1.  
Shennongjia is located in the broad-leaved forest ecological zone of Qinba Mountain, which is a key area for biodiversity conservation in China. The forest in Shennongjia represents a natural mountainous forest in the northern subtropical China. The annual mean temperature is 10.6 \({}^{\circ}\)C, and the annual total precipitation is 1219 mm in Shennongjia [51]. The soil samples were obtained at the altitudes of 760 m for EBF and 2080 m for ENF. The soils of both EBF and ENF are yellow-brown clay. Mt. Gongga is located in the transitional area between China's eastern monsoon subtropics and the frigid area of the Tibetan Plateau. The forest in Mt. Gongga represents a natural mountainous forest in western subtropical China. The annual mean temperature is 4.4 \({}^{\circ}\)C and the annual total precipitation is 1910 mm in Mt. Gongga. The soil samples were obtained at the altitudes of 2265 m for EBF and 3082 m for ENF. The soil for EBF is brown silt soil and that for ENF is dark-brown silt soil. Dinghushan is located in southern tropical China, and its forest represents a southern tropical natural forest in China. The annual total precipitation is 1680 mm and the annual mean temperature is 22.3 \({}^{\circ}\)C in Dinghushan [52]. The sampling plots were located at the altitudes of 89 m for EBF and 210 m for ENF. The soils for both EBF and ENF are red loam. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Pool** & \(\mathbf{r}_{ij}\) & **Ref** & \(\mathbf{d}_{ij}\) & **Ref** & **RSB** & **Ref** \\ \hline \multirow{4}{*}{EBF} & root & 433.62 & \multirow{4}{*}{[39; 40]} & \multirow{4}{*}{0.72} & \multirow{4}{*}{0.58} & \multirow{4}{*}{[58]} \\  & wood & (177.02–585.82) & & & & & \\  & & 479.62 & \multirow{4}{*}{[39; 40]} & \multirow{4}{*}{0.72} & \multirow{4}{*}{0.06} & \multirow{4}{*}{[58]} \\  & leaf & (269.02–828.16) & & & & & \\  & leaf & 431.41 & \multirow{4}{*}{[39; 42; 43; 44; 45; 46]} & \multirow{4}{*}{0.06} & \multirow{4}{*}{[52]} & \multirow{4}{*}{[51]} \\  & root & (208.11–779.13) & & & & & \\ \hline \multirow{4}{*}{ENF} & root & 386.92 & \multirow{4}{*}{[59; 50]} & \multirow{4}{*}{0.19} & \multirow{4}{*}{0.58} & \multirow{4}{*}{[58]} \\  & & (224.84–404.80) & & & & & \\ \cline{1-1} \cline{5-5}  & wood & 726.67 & \multirow{4}{*}{[59; 50]} & \multirow{4}{*}{0.73} & \multirow{4}{*}{0.58} & \multirow{4}{*}{[58]} \\  & leaf & & 568.55 & & & & \\ \cline{1-1} \cline{5-5}  & leaf & (333.12–843.06) & & & & & \\ \hline \multirow{4}{*}{DBF} & root & 513 (410–615) & [59; 50] & 0.24 & \multirow{4}{*}{0.06} & \multirow{4}{*}{0.46} \\  & wood & 2187 (1750–2625) & [59] & 0.70 & & & \\ \cline{1-1} \cline{5-5}  & leaf & 622 (192–1052) & [59; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 60; 62; 64; 63; 65; 67; 68; 69; 61; 60; 64; 65; 66; 68; 67; 69; 62; 68; 69; 60; 63; 67; 68; 69; 60; 64; 65; 67; 68; 69; 61;Qian Yanzhou is located at the central subtropical region in China, with an annual total precipitation of 1485 mm and an annual mean temperature of 17.9 \({}^{\circ}\)C. The plantation in Qian Yanzhou represents a man-made forest in the central subtropical region. The soil samples were obtained at the altitudes of 55 m for EBF and 103 m for ENF.