Preliminary Investigations of the Role of Smoke Aerosols on Carbon Uptake of a Northern Australian Tropical Savanna
| Kanniah, Kasturi | Monash University |
| Tapper, Nigel | Monash University |
| Beringer, Jason | Monash University |
| Zhu, Xuan | Monash University |
| Long, Chuck | Pacific Northwest National Laboratory |
Category: Aerosols
Plant productivity is a major component of the global carbon cycle. It is an indicator of the quantity of carbon absorbed and stored by vegetation. Plant productivity is largely driven by solar radiation (photosynthetically active radiation/PAR). Aerosols originating from savanna burning produce the second largest amount of organic and elemental carbon into the atmosphere (17.67 Tg C/yr) after tropical forests (18.53 Tg C/yr). Organic carbon, the most abundant carbonaceous aerosol, is an effective scatterer of solar radiation. This scattering can increase the relative proportion of diffuse solar radiation reaching the forest canopy. Per unit optical depth, aerosols are more effective at converting direct PAR to diffuse PAR (Cohan et al., 2002). Diffuse radiation provides a more even illumination of leaf surfaces and greater penetration of leafy canopies and therefore leads to a larger photosynthetic efficiency per unit of total global radiation (Gu et al., 2002). Research in many ecosystems around the world has shown enhanced productivity under cloudy and hazy environments (Cohan et al., 2002, Gu et al., 2002, Roderick et al., 2001). However, excessively high levels of cloud or aerosol loadings can reduce plant productivity through an increase in optical depth. Canopy structure/architecture and photosynthesis pathways of different vegetation, as well as other environmental factors at different locations on the earth are likely to exhibit contrasting responses to different levels of aerosol. For example, in northern Australia, vast areas of savannas are burnt annually and result in a range of aerosol loadings. This preliminary study, utilizing direct and diffuse solar radiation, aerosol optical depth, and a range of other measurements from the Darwin ARM site explores the links between aerosol loadings associated with savanna burning and plant productivity at Howard Springs, Northern Australia. Plant productivity (gross primary production - GPP) has been measured at Howard Springs continuously since 2001 using an eddy covariance flux tower (Beringer et al., 2005), which provides detailed half-hourly micrometeorological and plant physiological data. References: 1. Beringer et. al., 2005, Savanna fires and their impact on net ecosystem productivity in North Australia, in press. 2. Cohan, D., et al., 2002, Impact of atmospheric aerosol light scattering and absorption on terrestrial net primary productivity, Glob Biogeochemical Cycles, 16(4). 3. Gu, et al. 2002, Advantages of diffuse radiation for terrestrial ecosystem productivity, J. Geophys. Res, 107(D6). 4. Pyles, R. David, 2000, The development and testing of the UCD Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) for use in climate prediction and field studies PhD, UNIVERSITY OF CALIFORNIA, DAVIS. 5. Roderick, et al., 2001, On the direct effect of clouds and atmospheric particles on the productivity and structure of vegetation, Oecologia, 129:21-30.
This poster will be displayed at the ARM Science Team Meeting.
