The Sensitivity of Diel CO2 and H2O Vapor Exchange of a Tropical Transitional Forest to Seasonal Variation in Meteorology and Water Availability

Vourlitis, George L.; Nogueira, José de Souza; Filho, Nicolau Priante; Hoeger, Wander; Raiter, Fernando; Biudes, Marcelo Sacardi; Arruda, Jose Carlos; Capistrano, Vinícius; Faria, J.L.B.; Lobo, Francisco de Almeida

doi:10.1175/ei124.1

Cited by 32 publications

(41 citation statements)

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“…Thus, even with ample surface water availability and consistently high LAI there was significant resistance to water vapor exchange from stomatal closure (McWilliam et al 1996;Sa et al 1996;Vourlitis et al 2008;Sendall et al 2009), hydraulic conductivity (Meinzer et al 1993;Eamus 1999), and canopy structure (Jarvis and McNaugton 1986). This response has been described in other tropical forests (Meinzer et al 1993;Vourlitis et al 2005) and has likewise been attributed to stomatal closure caused by high evaporative demand.…”

Section: Seasonal Variation In Energy Balancementioning

confidence: 95%

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

et al. 2011

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The recent and widespread expansion of the pioneer tree species Vochysia divergens Pohl into western Brazil has the potential to significantly alter the structure and function of the Pantanal-a UNESCO World Heritage Site and the World's largest tropical wetland. Here we assess the seasonal pattern of evapotranspiration (ET) and micrometeorological variables of V. divergens (locally known as cambarazal), located in the Northeast of the Brazilian Pantanal. ET was calculated from a number of micrometeorological measurements recorded between January 2007 and January 2008. The results indicate that ET was the dominant sink for net radiation (R n ) during the wet and dry seasons, primarily because the forest was either flooded (December-May) or retained a high level of soil moisture. ET decreased during the dry season due to a decline in R n and surface water availability, and an increase in atmospheric vapor pressure deficit. Based on this analysis we conclude that the spread of V. divergens into the Pantanal and the associated high rates of ET are due in part to high water availability, even during the dry season, and the consistently high leaf area index that increases the transpiration surface area when the water table is below the soil surface.

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Section: Seasonal Variation In Energy Balancementioning

confidence: 95%

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

et al. 2011

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“…Field observations showed the importance of seasonal variations in ecosystem respirations responding to the water availabilities (e.g. Saleska et al, 2003;Vourlitis et al, 2005). Current ecosystem models mostly fail to simulate the seasonality of respiration, therefore, further improvements of water effects on respiration are required to simulate NEE.…”

Section: Limitation and Further Model Improvementsmentioning

confidence: 99%

Constraining rooting depths in tropical rainforests using satellite data and ecosystem modeling for accurate simulation of gross primary production seasonality

Ichii

Hashimoto

White

et al. 2006

Global Change Biology

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Accurate parameterization of rooting depth is difficult but important for capturing the spatio-temporal dynamics of carbon, water and energy cycles in tropical forests. In this study, we adopted a new approach to constrain rooting depth in terrestrial ecosystem models over the Amazon using satellite data [moderate resolution imaging spectroradiometer (MODIS) enhanced vegetation index (EVI)] and Biome-BGC terrestrial ecosystem model. We simulated seasonal variations in gross primary production (GPP) using different rooting depths (1, 3, 5, and 10 m) at point and spatial scales to investigate how rooting depth affects modeled seasonal GPP variations and to determine which rooting depth simulates GPP consistent with satellite-based observations. First, we confirmed that rooting depth strongly controls modeled GPP seasonal variations and that only deep rooting systems can successfully track flux-based GPP seasonality at the Tapajos km67 flux site. Second, spatial analysis showed that the model can reproduce the seasonal variations in satellite-based EVI seasonality, however, with required rooting depths strongly dependent on precipitation and the dry season length. For example, a shallow rooting depth (1-3 m) is sufficient in regions with a short dry season (e.g. 0-2 months), and deeper roots are required in regions with a longer dry season (e.g. 3-5 and 5-10 m for the regions with 3-4 and 5-6 months dry season, respectively). Our analysis suggests that setting of proper rooting depths is important to simulating GPP seasonality in tropical forests, and the use of satellite data can help to constrain the spatial variability of rooting depth.

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“…For example, eddy covariance studies in the Amazon Basin indicate that tropical ecosystems may be sinks for atmospheric CO 2 [ Malhi et al , 1998; Araujo et al , 2002; Carswell et al , 2002; von Randow et al , 2004], approximately in balance [ Priante‐Filho et al , 2004; da Rocha et al , 2002; Vourlitis et al , 2004; Hutyra et al , 2007], or net sources of CO 2 to the atmosphere [ Saleska et al , 2003; Miller et al , 2004]. Some of this uncertainty may stem from methodological differences, such as variations in data rejection criteria (i.e., u * correction) and flux corrections [ Kruijt et al , 2004; Miller et al , 2004], but given the size, floristic diversity, and climatic variation of the Amazon Basin, these disparate results are likely influenced strongly by large‐scale interactions between climate variability and ecosystem phenology [ Goulden et al , 2004; Vourlitis et al , 2004, 2005; Meir and Grace , 2005; Saleska et al , 2009; Vourlitis and da Rocha , 2010].…”

Section: Introductionmentioning

confidence: 99%

Temporal patterns of net CO₂exchange for a tropical semideciduous forest of the southern Amazon Basin

Vourlitis¹,

Lobo²,

Zeilhofer³

et al. 2011

J. Geophys. Res.

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The carbon cycling of tropical ecosystems has received considerable attention over the last 1–2 decades; however, interactions between climate variation and tropical forest net ecosystem CO2 exchange (NEE) are still uncertain. To reduce this uncertainty, and assess the biophysical controls on NEE, we used the eddy covariance method over a 3 year period (2005–2008) to measure the CO2 flux and energy balance for a 25–28 m tall, mature tropical semideciduous forest located near Sinop Mato Grosso, Brazil. The study period encompassed warm‐dry, cool‐wet, and cool‐dry climate conditions, and based on previous research, we hypothesized that the net CO2 accumulation of the semideciduous forest would be lower during periods of drought. Using time series of the enhanced vegetation index (EVI), a NEE‐light‐use model, and path analysis, we found that the estimated quantum yield (a′, μmol CO2μmol photons−1) was directly affected by temporal variations in the EVI, precipitation, and photosynthetically active radiation (PAR), while the optimal rate of gross primary production (FGPP,opt, μmol m−2 s−1) was directly affected by the EVI and PAR. However, indirect effects of precipitation on the a′ and FGPP,opt were stronger than direct effects because variations in precipitation also lead to variations in the EVI and the atmospheric vapor pressure deficit (VPD). Daytime ecosystem respiration (FRE,day, μmol m−2 s−1) was directly affected by temporal variations in temperature and VPD and indirect effects of other variables were of lesser importance. Net ecosystem CO2 uptake was often higher in the dry season than the wet season, not because of a dry season “green‐up” but because rates of ecosystem respiration declined relatively more than rates of canopy photosynthesis. Over interannual timescales, average daily NEE increased over the 3 year study period and was highest in 2007–2008, which was also the driest year in terms of rainfall. However, 2007–2008 was also the coolest year during the 3 year study period, and the low temperature appeared to compensate for the low rainfall. Overall, our data suggest that the NEE of tropical semideciduous forests is sensitive to temporal variations in surface water availability but that indirect effects of other variables, such as temperature and VPD, are important in controlling CO2 gain and loss. Such interactions will be important for the future NEE under warmer and drier conditions that are anticipated with anthropogenic climate change.

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The Sensitivity of Diel CO2 and H2O Vapor Exchange of a Tropical Transitional Forest to Seasonal Variation in Meteorology and Water Availability

Cited by 32 publications

References 50 publications

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

Constraining rooting depths in tropical rainforests using satellite data and ecosystem modeling for accurate simulation of gross primary production seasonality

Temporal patterns of net CO₂exchange for a tropical semideciduous forest of the southern Amazon Basin

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The Sensitivity of Diel CO2 and H2O Vapor Exchange of a Tropical Transitional Forest to Seasonal Variation in Meteorology and Water Availability

Cited by 32 publications

References 50 publications

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

Seasonal Patterns of Evapotranspiration for a Vochysia divergens Forest in the Brazilian Pantanal

Constraining rooting depths in tropical rainforests using satellite data and ecosystem modeling for accurate simulation of gross primary production seasonality

Temporal patterns of net CO2exchange for a tropical semideciduous forest of the southern Amazon Basin

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Temporal patterns of net CO₂exchange for a tropical semideciduous forest of the southern Amazon Basin