The Sensitivity of Diel CO2

Measurements of ecosystem gas exchange, meteorology, and hydrology (rainfall and soil moisture) were used to assess the seasonal patterns of, and controls on, average diel (24 h) net ecosystem CO2 exchange (NEE), evapotranspiration (E), and bulk canopy water vapor conductance (Gc) of a tropical tran...

Full description

Saved in:
Bibliographic Details
Published in:Earth interactions 2005-12, Vol.9 (27), p.1
Main Authors: Vourlitis, George L, Souza Nogueira, José de, Filho, Nicolau Priante, Hoeger, Wander, Raiter, Fernando, Biudes, Marcelo Sacardi, Arruda, Jose Carlos, Capistrano, Vinicius Buscioli, Brito de Faria, Jorge Luiz, Almeida Lobo, Francisco de
Format: Article
Language:English
Subjects:
Carbon dioxide
Diel variations
Drought
Dry season
Ecology
Ecosystems
Evapotranspiration
Forests
Gas exchange
Hydrology
Land use
Photosynthesis
Rainfall
Seasonal variations
Seasons
Soil moisture
Soil surfaces
Tropical forests
Vapor pressure
Water availability
Water vapor
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Measurements of ecosystem gas exchange, meteorology, and hydrology (rainfall and soil moisture) were used to assess the seasonal patterns of, and controls on, average diel (24 h) net ecosystem CO2 exchange (NEE), evapotranspiration (E), and bulk canopy water vapor conductance (Gc) of a tropical transitional (ecotonal) forest in the Brazilian Amazon. Diel trends in E and NEE were almost completely explained by the diel variation in photosynthetic photon flux density (QPPFD), and while the QPPFD response of E varied little over the annual cycle, the QPPFD response of NEE declined substantially during the dry season, and the magnitude of hysteresis in the NEE-QPPFD response increased as well. The magnitude of the residuals for the QPPFD versus NEE response was significantly negatively correlated with total monthly rainfall and surface soil moisture and positively correlated with the maximum daily temperature and atmospheric vapor pressure deficit (V). Average daily Gc was also significantly correlated with average daily V (r = -0.72) and soil moisture (r = 0.62), suggesting strong stomatal control of NEE during drought. However, drought reduced ecosystem CO2 efflux relatively more than CO2 assimilation, suggesting that the seasonal variation in NEE was largely driven by seasonal variation in respiration. When compared with other tropical forests, seasonality in NEE was negatively correlated with annual rainfall and positively correlated with dry-season length. The relatively high sensitivity of NEE to seasonal variation in climate and water availability has profound implications for C cycling dynamics under novel climates resulting from climate and/or land-use change in the Amazon basin. [PUBLICATION ABSTRACT]
ISSN:1087-3562
DOI:10.1175/EI124.1