Studies show evidence of recent biomass increases across various forest types, including temperate forests. However, long-term observations of biomass trends in forests are not common, and thus we should improve our base understanding of what “normal” biomass trends look like before drawing conclusions about recent trends. In this study, I am interested in observing multi-decadal, species-specific growth trends to gain a better understanding about long-term successional trends in biomass. Using an 80-year tree-growth and mortality data set of 34 permanent sample plots in the Duke Forest, I examine trends of biomass accumulation and individual tree growth in a successional temperate Piedmont forest.
My results suggest that successional pine forests in the Piedmont sustained continued biomass accumulation through at least 90 years after initial stand development. Total plot biomass increased from an average of 43.3 Mg/ha to 317.4 Mg/HA during the length of the study. It appears that biomass of stands remained increasing even following "regular levels" of canopy pine senescence. The hardwood species in the understory more than made up for the loss of canopy biomass due to senescence , and total plot biomass increased due to increases in understory Liquidambar styraciflua, Liriodendron tulipifera, Acer rubrum, and (to a lesser degree) various species of oaks and hickories. However, major losses of biomass occurred following major destruction from Hurricane Fran in 1996 and to a lesser extent Hurricane Hazel in in the mid-1950s. The oldest plots (i.e., those > 80 years old at the time of the more recent hurricane) suffered a much larger loss of biomass following Fran, likely owing to the weakened state of the older canopy trees. However, all but two plots returned to accreting biomass less than a decade following the hurricane (a trend that continues almost 2 decades later).
This study provides an updated, directly-informed understanding of long-term successional biomass patterns in Southeastern U.S. forests to allow for continued and enhanced utility of succession as a predictive model in the face of land-use and climate change.