Few large trees drive the carbon dynamics of temperate forests

Although large trees explain the most variation in biomass and structure of forests, but little is known about whether and how large trees can explain variation of forest dynamics (forest productivity and biomass loss). To shed light on the effects of large trees on forest dynamics we analyzed repeated forest inventory data on 74,300 adult trees spread across 700 quadrats of temperate mixed forest in northeastern China. Here, using piecewise structural equation modeling we examined how top 1% high-biomass, 99% remaining-biomass trees, functional trait diversity (FD) and composition (CWM), climate and soil conditions influence forest dynamics in temperate old growth forests. We found that top 1% high-biomass and top 1% large-diameter trees highly increased forset dynamics and biomass stock rather their relevant 99% remaining trees, FD and CWM supporting big-size trees hypothesis. In addition, climate is more important determinant of forest productivity rates than soil nutrients. Moreover, forest productivity and biomass stock declined with CWM traits. Hence, we highlight top 1% trees overruled the effect of 99% remaining trees, FD and CWM on forest dynamics and biomass stock. We argue that including site variation and the big trees to the integrative ecological modeling help better understanding of ecological mechanisms and drivers of forest dynamics.