Net ecosystem carbon exchange of a dry temperate eucalypt forest Article Swipe
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· 2016
· Open Access
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· DOI: https://doi.org/10.5194/bg-2016-192
· OA: W4230849028
Forest ecosystems play a crucial role in the global carbon cycle by sequestering a considerable fraction of anthropogenic CO2 thereby contributing to climate change mitigation. However, there is a gap in our understanding about the carbon dynamics of eucalypt (broadleaf evergreen) forests in temperate climates, which might differ from temperate coniferous or deciduous forests given their fundamental differences in physiology, phenology and growth dynamics. To address this gap we undertook a three year study (2010–2012) using eddy covariance measurements in a dry temperate eucalypt forest in south-eastern Australia. We determined the annual net ecosystem carbon exchange (NEE) and investigated the temporal (seasonal and inter-annual) variability and environmental controls of NEE, gross primary productivity (GPP) and ecosystem respiration (ER). The forest was a large and constant carbon sink throughout the study period, even in winter, with an overall mean NEE of −1062 ± 53 g C m−2 yr−1. Gross CO2 ecosystem fluxes showed no significant inter-annual variability and mean annual estimate of GPP was 2521 ± 35 g C m−2 yr−1 and ER was 1458 ± 31 g C m−2 yr−1. GPP and ER had a pronounced seasonality with GPP being greatest during spring and summer and ER during summer whereas peaks of NEE occurred in early spring and again in summer. High NEE in spring was caused by a delayed increase in ER due to low temperatures. A random forest analysis showed that variability in GPP was mostly explained by incoming solar radiation whilst air temperature was the main environmental driver of ER on seasonal and inter-annual time scales. The forest experienced unusual above average annual rainfall during the first two years of this three year period so that soil moisture content remained relatively high and the forest was not water limited. Our results show the potential of temperate eucalypt forests to sequester large amounts of carbon when not water limited. Our observations can provide data on an underrepresented biome to test and parameterise ecosystem models. However, longer monitoring is needed to assess the inter-annual variability of the carbon sink strength particularly during years with drought conditions.
