Biomass Dynamics of Amazonian Forest Fragments William F. Laurance & Henrique Nascimento Smithsonian Tropical Research Institute, Panama Biological Dynamics of Forest Fragments Project, Manaus, Brazil

Deforestation in Brazilian Amazonia Increased significantly during the last decade : 1.31 million ha/year : 1.92 million ha/year

Rapid Forest Fragmentation Every km 2 of each landscape has km of forest edge Every km 2 of each landscape has km of forest edge Nearly 20,000 km of new edge created in Brazilian Amazon annually* Nearly 20,000 km of new edge created in Brazilian Amazon annually* * W. Chomentowski, D. Skole, M. Cochrane, Michigan State University

Biological Dynamics of Forest Fragments Project

Study Area

Edge-related Changes in Forest Dynamics, Structure, and Composition

Elevated Tree Mortality Laurance et al. (1998) Ecology

Loss of Large-tree Biomass Laurance et al. (1997) Science Laurance et al. (2000) Nature

Goals To assess impacts of fragmentation on all components of aboveground biomass To assess impacts of fragmentation on all components of aboveground biomass Large (>10 cm dbh) trees Large (>10 cm dbh) trees Understory biomass Understory biomass Necromass Necromass To estimate effects on forest C storage and atmospheric emissions To estimate effects on forest C storage and atmospheric emissions

Biomass Parameters Downed coarse debris (>10 cm) Downed coarse debris (>10 cm) Downed fine debris ( cm) Downed fine debris ( cm) Snags Snags Litter (leaves, twigs, fruits, etc.) Litter (leaves, twigs, fruits, etc.) Annual production of wood debris Annual production of wood debris Turnover of wood debris Turnover of wood debris Large-tree biomass Necromass Necromass Seedlings (<1 cm) Seedlings (<1 cm) Saplings (1-4.9 cm) Saplings (1-4.9 cm) Small trees (5-10 cm) Small trees (5-10 cm) Stemless palms Stemless palms Lianas (>1 cm) Lianas (>1 cm) Understory biomass Large-tree biomass Large-tree biomass Biomass increment Biomass increment Annual change in biomass Annual change in biomass

Ordination of 14 Biomass Attributes

Edge vs. Interior: Significant Differences

Increased Wood Debris Nascimento & Laurance, in press. Ecological Applications.

Increased Litter Nascimento & Laurance, in press. Ecological Applications.

Biomass of Small (5-10 cm dbh) Trees

Total Understory Biomass

Estimating Edge-related Carbon Emissions Assume no changes in belowground biomass Assume no changes in belowground biomass Net biomass decline = biomass lost from large trees (22.7 Mg/ha) – increases in understory biomass (1.7 Mg/ha) and necromass (10.1 Mg/ha) = 10.9 Mg/ha Net biomass decline = biomass lost from large trees (22.7 Mg/ha) – increases in understory biomass (1.7 Mg/ha) and necromass (10.1 Mg/ha) = 10.9 Mg/ha Half of biomass is carbon, most is respired quickly Half of biomass is carbon, most is respired quickly Thus, committed emissions are 4-6 Mg/ha Thus, committed emissions are 4-6 Mg/ha Because tree mortality is elevated within 300 m of edges, we expect Mg C for every 100 m of forest edge created Because tree mortality is elevated within 300 m of edges, we expect Mg C for every 100 m of forest edge created Based simply on current rate of edge creation, annual emissions would be million Mg/year Based simply on current rate of edge creation, annual emissions would be million Mg/year

Fragmentation and Fire Increased wood debris & litter Increased wood debris & litter Recurring canopy damage Recurring canopy damage Higher insolation, wind & temperatures Higher insolation, wind & temperatures Nearby ignition sources Nearby ignition sources

Conclusions Fragmentation causes striking changes in the distribution of aboveground biomass Fragmentation causes striking changes in the distribution of aboveground biomass – Decline of large-tree biomass – More wood debris, litter, small trees C cycling accelerates sharply C cycling accelerates sharply Substantial C emissions Substantial C emissions Drastic increase in fire vulnerability Drastic increase in fire vulnerability