Geography
Document Type
Article
Abstract
Predicting the seasonal dynamics of ecosystem carbon fluxes is challenging in broadleaved evergreen forests because of their moderate climates and subtle changes in canopy phenology. We assessed the climatic and biotic drivers of the seasonality of net ecosystem-atmosphere CO2 exchange (NEE) of a eucalyptus-dominated forest near Sydney, Australia, using the eddy covariance method. The climate is characterised by a mean annual precipitation of 800mm and a mean annual temperature of 18°C, hot summers and mild winters, with highly variable precipitation. In the 4-year study, the ecosystem was a sink each year (-225gCm-2yr-1 on average, with a standard deviation of 108gCm-2yr-1); inter-annual variations were not related to meteorological conditions. Daily net C uptake was always detected during the cooler, drier winter months (June through August), while net C loss occurred during the warmer, wetter summer months (December through February). Gross primary productivity (GPP) seasonality was low, despite longer days with higher light intensity in summer, because vapour pressure deficit (D) and air temperature (Ta) restricted surface conductance during summer while winter temperatures were still high enough to support photosynthesis. Maximum GPP during ideal environmental conditions was significantly correlated with remotely sensed enhanced vegetation index (EVI; r2 Combining double low line 0.46) and with canopy leaf area index (LAI; r2Combining double low line 0.29), which increased rapidly after mid-summer rainfall events. Ecosystem respiration (ER) was highest during summer in wet soils and lowest during winter months. ER had larger seasonal amplitude compared to GPP, and therefore drove the seasonal variation of NEE. Because summer carbon uptake may become increasingly limited by atmospheric demand and high temperature, and because ecosystem respiration could be enhanced by rising temperatures, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.
Publication Title
Biogeosciences
Publication Date
2018
Volume
15
Issue
12
First Page
3703
Last Page
3716
ISSN
1726-4170
DOI
10.5194/bg-15-3703-2018
Keywords
air temperature, broad-leaved forest, carbon dioxide, carbon sink, eddy covariance, environmental conditions, evergreen forest, leaf area index, light intensity, seasonal variation, seasonality, source-sink dynamics, summer, temperate environment, vegetation index
Repository Citation
Renchon, Alexandre A.; Griebel, Anne; Metzen, Daniel; Williams, Christopher A.; Medlyn, Belinda; Duursma, Remko A.; Barton, Craig V.M.; Maier, Chelsea; Boer, Matthias M.; Isaac, Peter; Tissue, David; Resco De DIos, Victor; and Pendall, Elise, "Upside-down fluxes Down Under: CO2 net sink in winter and net source in summer in a temperate evergreen broadleaf forest" (2018). Geography. 876.
https://commons.clarku.edu/faculty_geography/876
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Copyright Conditions
Published source must be acknowledged with citation:
Renchon, Alexandre A., et al. "Upside-down fluxes Down Under: CO 2 net sink in winter and net source in summer in a temperate evergreen broadleaf forest." Biogeosciences 15.12 (2018): 3703-3716.
