PARENT SESSION
Tuesday, August 8, 8:00-11:30 am
COS 29 - Forest ecology I
L-3, Lobby Level, Cook Convention Center
Presiders: C Tripler and C Wayson

Succession, sampling biases, and biomass dynamics of old-growth tropical forests.

Feeley, Kenneth^*,1, Davies, Stuart¹, Potts, Matthew², Asheton, Peter¹, Bunyavejchewin, Sarayudh³, Kassim, Abdul Rahman⁴, Noor, Md. Nur Supardi⁴, Tan, Sylvester⁵, ¹ Center for Tropical Forest Science, Cambridge, MA² University of Miami, Coral Gables, FL³ Thai National Park Wildlife and Plant Conservation Department, Bangkok, Thailand⁴ Forest Research Institute of Malaysia, Kuala Lumpur, Malaysia⁵ Smithsonian Institution, Washington, DC

ABSTRACT- Recent studies have revealed that aboveground woody biomass has increased in tropical forest inventory plots over the past several decades. The studies contend that these findings are indicative of forest-wide responses to carbon fertilization and as such that tropical forests represent a large part of the missing carbon sink and may partially offset increasing CO₂ emissions. Alternatively these findings may be unrepresentative of dynamics at larger scales since small (1 ha) inventory plots are potentially biased towards early to mid-successional forests. Under this scenario, observed increases in biomass are due to recovery from past disturbance and would be offset by small-scale but dramatic carbon losses from poorly sampled mature forest stands. Here, using long-term tree census data from large (50 ha) inventory plots located in four different old-growth tropical forests (Barro Colorado Island, Panama; Pasoh, Malaysia; Lambir, Borneo; and Haui Kha Khaeng, Thailand), we show that the majority of area within these forests is in fact undergoing successional biomass increases largely offset by rare decreases which are underrepresented in small inventory plots. When succession is accounted for, two plots (Lambir and Haui Kha Khaeng) did not exhibit significant changes in biomass over the study period whereas the remaining two plots did. At Barro Colorado, the mean standing biomass of all succesional stages decreased. In contrast, at Pasoh the mean biomass of early succcessional stands increased while the mean biomass of mature forest decreased. These findings do not preclude an effect of global change phenomena but indicate that succession plays an important role in explaining biomass dynamics that must be accounted for in future studies.

Key words: forest biomass, successional dynamics, climate change