black spruce (Picea mariana) aged 3e151 years peaks for 71-yearold
stands. Yuan and Chen (2012) reported that FRP of post-fire
stands aged 3e205 years peaks relatively early, at 11 years, and
then declines. In this study on the Loess Plateau, however, neither
the peak nor the stable condition of FRP of the two species occurred
within the 40 year time frame of the stands, which could be related
to the narrow range of stand-age classes (Finer et al., 1997;
Makkonen and Helmisaari, 2001). This finding suggests that
further investigations with both younger and older stands are
needed to test whether FRP responds in the “increase-peakdecline”
manner widely agreed upon by other researchers (BondLamberty
et al., 2004; Yuan and Chen, 2012).