Trade‐off between standing biomass and productivity in species‐rich tropical forest: Evidence, explanations and implications

  1. Despite its broad implications for community structure and dynamics, we lack a clear understanding of how forest productivity is partitioned among tree species. As leaf mass per unit of standing biomass declines with tree size, species achieving larger stature should show lower relative productivity as compared to smaller stature species. However, many observations indicate large‐stature species grow faster than small‐stature species. In this study, we address this apparent paradox, and clarify interspecific trade‐offs between turnover rates and maximum size in terms of forest‐level productivity and biomass storage.
  2. We examined data from the 1990 and 2000 surveys of the Pasoh 50‐ha plot of Malaysian rain forest. In these data, individual stems ≥1 cm stem diameter (dbh) have been identified, marked, measured and mapped. We applied site‐specific equations to estimate tree biomass from dbh. We estimated species‐level productivity and loss rates that are less influenced by census interval‐related effects and biases.
  3. Among 390 abundant tree species, species with high stand‐level biomass were predominantly those large‐stature species where individuals could achieve large sizes. We found that relative (= per‐species‐biomass) productivity and loss rate, per‐capita recruitment and mortality of species were all negatively correlated to species biomass and maximum size, but not to species abundance.
  4. Large‐stature species grew faster than small‐stature species at the same tree sizes up to 36 cm dbh. However, the relative growth of large species at their maximum size markedly declined. As a result, tree‐level relative growth at maximum size and species‐level relative productivity decreased with species‐level biomass.
  5. Performing further analyses using smaller plots in four old‐growth forests in Indonesia and Japan, we observed a similar interspecific negative relationship between relative productivity and biomass. We expect this phenomenon is widespread across species‐rich forests.
  6. Synthesis. How productivity is partitioned among species determines and reflects forest ecosystem functioning and species coexistence. Many species with low biomass and small maximum stem sizes disproportionally contribute to forest primary productivity, rapid recovery and resilience. In contrast, long‐lived, high‐biomass species contribute disproportionally to ecosystem stability and carbon storage. This complementarity reflects differentiation by adult stature among species.
Takashi S. Kohyama, Matthew D. Potts, Tetsuo I. Kohyama, Kaoru Niiyama, Tze Leong Yao, Stuart J. Davies, & Douglas Sheil
Journal of Ecology