Comparison of fine root biomass among cropland and younger and older plantations in each site as well as among the younger and older plantations in four sites.

<p>Younger plantations are 5- to 9-year- old and older plantations are 25- to 30- year-old forests, respectively. The error bars represent the standard deviations of the means. The sample numbers are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085426#pone-0085426-t001" target="_blank">Table 1</a>. A different lowercase English letter is used for cropland and for younger and older plantations in the same site, and a different uppercase English letter represents younger plantations across the sites, whereas a different Greek letter is used for older plantations to indicate a significant difference at the 0.05 level.