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Pyle, Elizabeth Hammond

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Pyle

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Elizabeth Hammond

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Pyle, Elizabeth Hammond
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    Seasonal carbon dynamics and water fluxes in an Amazon rainforest
    (Wiley-Blackwell, 2012) Kim, Yeonjoo; Knox, Ryan G.; Longo, Marcos; Medvigy, David; Hutyra, Lucy; Pyle, Elizabeth Hammond; Wofsy, Steven; Bras, Rafael L.; Moorcroft, Paul
    Satellite-based observations indicate that seasonal patterns in canopy greenness and productivity in the Amazon are negatively correlated with precipitation, with increased greenness occurring during the dry months. Flux tower measurements indicate that the canopy greening that occurs during the dry season is associated with increases in net ecosystem productivity (NEP) and evapotranspiration (ET). Land surface and terrestrial biosphere model simulations for the region have predicted the opposite of these observed patterns, with significant declines in greenness, NEP, and ET during the dry season. In this study, we address this issue mainly by developing an empirically constrained, light-controlled phenology submodel within the Ecosystem Demography model version 2 (ED2). The constrained ED2 model with a suite of field observations shows markedly improved predictions of seasonal ecosystem dynamics, more accurately capturing the observed patterns of seasonality in water, carbon, and litter fluxes seen at the Tapajos National Forest, Brazil (2.86°S, 54.96°W). Long-term simulations indicate that this light-controlled phenology increases the resilience of Amazon forest NEP to interannual variability in climate forcing.
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    Dynamics of Carbon, Biomass, and Structure in Two Amazonian Forests
    (American Geophysical Union, 2008) Pyle, Elizabeth Hammond; Santoni, Gregory; Nascimento, Henrique E. M.; Hutyra, Lucy R.; Vieira, Simone; Curran, Daniel J.; van Haren, Joost; Saleska, Scott R.; Chow, Victoria Ye; Carmago, Plinio B.; Laurance, William; Wofsy, Steven
    Amazon forests are potentially globally significant sources or sinks for atmospheric carbon dioxide. In this study, we characterize the spatial trends in carbon storage and fluxes in both live and dead biomass (necromass) in two Amazonian forests, the Biological Dynamic of Forest Fragments Project (BDFFP), near Manaus, Amazonas, and the Tapajós National Forest (TNF) near Santarém, Pará. We assessed coarse woody debris (CWD) stocks, tree growth, mortality, and recruitment in ground-based plots distributed across the terra firme forest at both sites. Carbon dynamics were similar within each site, but differed significantly between the sites. The BDFFP and the TNF held comparable live biomass (167 ± 7.6 MgC·ha−1 versus 149 ± 6.0 MgC·ha−1, respectively), but stocks of CWD were 2.5 times larger at TNF (16.2 ± 1.5 MgC·ha−1 at BDFFP, versus 40.1 ± 3.9 MgC·ha−1 at TNF). A model of current forest dynamics suggests that the BDFFP was close to carbon balance, and its size class structure approximated a steady state. The TNF, by contrast, showed rapid carbon accrual to live biomass (3.24 ± 0.22 MgC·ha−1·a−1 in TNF, 2.59 ± 0.16 MgC·ha−1·a−1 in BDFFP), which was more than offset by losses from large stocks of CWD, as well as ongoing shifts of biomass among size classes. This pattern in the TNF suggests recovery from a significant disturbance. The net loss of carbon from the TNF will likely last 10–15 years after the initial disturbance (controlled by the rate of decay of coarse woody debris), followed by uptake of carbon as the forest size class structure and composition continue to shift. The frequency and longevity of forests showing such disequilibruim dynamics within the larger matrix of the Amazon remains an essential question to understanding Amazonian carbon balance.