Controles dos Processos de Assimilação e Respiração de uma Floresta Amazônica Estou trablahando em Amonzonia Central para mais ou menos 10 anos com pesquiasadores, alunos, e pessoal do campo que faz parte do INPA. Uma questao que esta interesante para nos e o balanco de carbono em florestas primarias. A questao e basico: se voce poderia quantificar todo carbono na floresta un ano depois da outra, para 10, 20, 50 anos, a floresta iria ser fonte, sumidor, ou balancado no sentido de carbono? Jeffrey Q. Chambers, Edgard S. Tribuzy, Liliane M. Teixeira, Ligia C. Toledo, Roseana da Silva, Joaquim dos Santos, Niro Higuchi, and Susan E. Trumbore

The Central Amazon Manaus Work carried out on reserves managed by Nossos trabalhos estao feitos em reservas perto de cidade Manaus que voce pode ver nesse imagem satelite. Este Rio aqui e o Rio Negro, e este e o Solimoes. Este fragmento de floresta e Reserva Ducke, com comprimento de 10 por 10 kilometros. Work carried out on reserves managed by Instituto Nacional de Pesquisas da Amazônia (INPA)

Seasonal Changes: Tree Growth Each tree with dendrometer — trees of various sizes — monthly growth w/ calipers — precipitation variables Este projeto foi liderado por Rose da Silva, que ja terminou o mestrado dela no INPA.

Seasonal Changes: Tree Growth What drives variability? — Precipitation (30 day sum) — Dry days (distribution of precip.) — Month – why important? — evolutionary constraints important Dark green data, light green empirical model. Top figure only precipitation variables, bottom figure with precipitation and “month” as variables. Probably demonstrates importance of phenology; what is expected instead of what happens.

Ecosystem Respiration Components

Partitioning of Ecosystem Respiration Components Reco= 7.8 Ra 5.6 mmol m-2 s-1 Rh 2.2 mmol m-2 s-1 Units = mmol m-2 s-1 Tulane University: www.tulane.edu/~jchamber

Moisture Control Over Fine Surface Litter Respiration Respiratory flux from surface litter sensitive to moisture stress Respiration can be modeled as function of precipitation history

Ecosystem Fine Surface Litter Respiratory Flux 1997 El Niño 2200 mm 1999 La Niña 3200 mm Difference between wet and dry year ~0.4 Mg C ha-1 yr-1

Estimating Ecosystem Carbon Use Efficiency Ra Pg Pn CUE = Pn/(Ra + Pn) CUE = 30% Only about 30% of carbon assimilated in photosynthesis was used to construct new tissues, the remainder being respired back to the atmosphere as autotrophic respiration. Temperate Forest and Suggested Global Constant: CUE = 50% Chambers, J. Q., E. S. Tribuzy, L. C. Toledo, B.O. Crispim, N. Higuchi, J. d. Santos, A. C. Araújo, B. Kruijt, A. D. Nobre, and S. E. Trumbore. In press. Respiration from a Tropical Forest Ecosystem: Partitioning of Sources and Low Carbon Use Efficiency. Ecological Applications.

Potential Explanations for Low CUE Higher respiratory costs in tropical forests CUE increases with mean annual temperature Not carbon limited: many trees are assimilating more carbon than needed for construction and maintenance respiration CH2- + O2 cytochrome alternate CO2 + H2O + ATP CO2 + H2O + heat oxidase Does the alternate oxidase control an overflow pathway?

carbon allocated to woody tissue Carbon Overflow Hypothesis carbon allocated to woody tissue respiration growth maint. waste 1 m growth Carbon Partitioning in Woody Tissues: Resources Limited

carbon allocated to woody tissue Carbon Overflow Hypothesis carbon allocated to woody tissue respiration growth maint. waste 1 m growth Carbon Partitioning in Woody Tissues: Resources Increased

Overview of the BIONTE Logging Experiment Km-22 Km-23 Vicinal ZF-2 Bloco 4 Bloco 2 Bloco 1 A Acampamento Estrada de escoamento da madeira Escala 1: 20.000 P1, P2, ... : PICADA SP1, SP2, ... : SUB-PARCELA BLOCO 600 m 400 m 200 m SP1 SP3 SP2 SP5 SP4 SP6 SP7 SP8 SUB-BLOCO P1 P2 P3 P4 P5 P6 P7 P8 Treatments: % of commercial species basal area removed: T0: Control (3 ha) T1: 32% (3 ha) T2: 42% (3 ha) T3: 69% (3 ha) How does growth and woody tissue respiration of surviving tree respond to this disturbance?

Comparative Woody Tissue Respiration and Growth: Jacaranda/BIONTE Methods: Closed dynamic chambers 50 trees from Jacaranda plots continuous forest five growth classes 80 trees from BIONTE plots control plots three logging treatments Growth rate from dendrometer bands, corrected for density and carbon content.

Some Factors Accounting for Variability in Respiratory Flux Multiple regression and ANOVA Growth rate, tree size and treatment together explained about 50% of the variability in woody tissue respiration rates. The strongest treatment effect was between the BIONTE control plots and the undisturbed forest site. Analyses based on average rates over a number of months

Average Respiratory Flux for Statistically Equivalent Tree Size and Growth Rate Why was woody tissue respiration in the BIONTE control plots 50% less than the continuous forest site?

Changing Dynamics of Tropical Forests Forest turnover (recruitment + mortality) doubled from 1975-1990 Phillips, O. L., and A. H. Gentry. 1994. Increasing turnover through time in tropical forests. Science 263:954-958. Phillips, O. L., Y. Malhi, N. Higuchi, W. F. Laurance, P. V. Núñez, R. M. Vásquez, S. G. Laurance, L. V. Ferreira, M. Stern, S. Brown, and J. Grace. 1998. Changes in the carbon balance of tropical forests: evidence from long-term plots. Science 282:439-442. Phillips, O. L., R. V. Martinez, L. Arroyo, T. R. Baker, T. Killeen, S. L. Lewis, Y. Malhi, A. M. Mendoza, D. Neill, P. N. Vargas, M. Alexiades, C. Ceron, A. Di Fiore, T. Erwin, A. Jardim, W. Palacios, M. Saldias, and B. Vinceti. 2002. Increasing dominance of large lianas in Amazonian forests. Nature 418:770-774. Tree biomass has increased in Neotropics since 1980 at about 0.4-0.5 Mg C ha-1 yr-1 Relative dominance of lianas/trees has doubled over the past 20 years What is causing this non-equilibrium behavior?

Catastrophic and Background Mortality Permanent plot data provide information on background mortality What is the effect of catastrophic mortality on forest carbon balance? Little information on frequency and extent 200 m Severe downburst winds associated with late dry season storms

Summary Various transient ecological processes can account for year-to-year variations in carbon exchange with the atmosphere, but not represent a directional change in ecosystem carbon balance. Trees surviving elevated mortality responded to increase in resources with faster growth rates, a decrease in woody tissue respiratory flux, and an increase in carbon use efficiency. Hypothesis: many Central Amazon trees exist in a state of elevated carbon supply, and are poised to quickly respond when additional resources become available. Relatively small elevated mortality events lead to changes in forest carbon metabolism that may appear as biomass accumulation, but better characterized as a recovery phase. What portion of time are undisturbed tropical forests in biomass recovery phase as opposed to biomass loss phase?

Acknowledgments Instituto Nacional de Pesquisas da Amazônia (INPA) NASA LBA-ECO Projeto Piculus (PPG7) Japanese International Cooperation Agency (JICA) Tulane University