Williams Richard J, Hutley Lindsay B, Cook Garry D, Russell-Smith Jeremy, Edwards Andrew, Chen Xiayong
Cooperative Research Centre for Tropical Savanna Management. CSIRO Sustainable Ecosystems, PMB 44 Winnellie, NT 0821, Australia. Corresponding author; email:
Cooperative Research Centre for Tropical Savanna Management. School of Science and Primary Industries, Charles Darwin University, Darwin, NT 0909, Australia.
Funct Plant Biol. 2004 Jun;31(5):415-422. doi: 10.1071/FP03215.
Tropical savannas cover a quarter of the Australian landmass and the biome represents a significant potential carbon sink. However, these savannas are subject to frequent and extensive fire. Fire regimes are likely to affect the productivity and carbon sequestration potential of savannas, through effects on both biomass and carbon emissions. The carbon sequestration potential has been estimated for some savanna sites by quantifying carbon storage in biomass and soil pools, and the fluxes to these pools. Using different techniques, previous work in these savannas has indicated that net ecosystem productivity [NEP, net primary productivity (NPP) less heterotrophic respiration] was about -3 t C ha y (i.e. a carbon sink). However, the impacts of fire were not accounted for in these calculations. Estimates of NEP have been combined with remotely-sensed estimates of area burnt and associated emissions for an extensive area of mesic savanna in Arnhem Land, NT, Australia. Combining NEP estimates with precise fire data provides an estimate of net biome productivity (NBP), a production index that includes carbon loss through disturbance (fire), and is thus a more realistic indicator of sequestration rate from this biome. This preliminary analysis suggests that NBP is approximately -1 t C ha y (i.e. a carbon sink). A reduction in the annual area burnt is likely to increase the sink size. Uncertainties surrounding these estimates of NBP and the implications of these uncertainties for land management in these extensive landscapes are discussed.
热带稀树草原覆盖了澳大利亚四分之一的陆地面积，该生物群落具有成为重要潜在碳汇的巨大潜力。然而，这些稀树草原频繁遭受大面积火灾。火灾状况可能会通过对生物量和碳排放的影响，进而影响稀树草原的生产力和碳固存潜力。通过量化生物量和土壤库中的碳储量以及这些库的通量，已经对一些稀树草原地点的碳固存潜力进行了估算。利用不同技术，此前在这些稀树草原开展的工作表明，净生态系统生产力[净生态系统生产力（NEP），即净初级生产力（NPP）减去异养呼吸]约为-3吨碳/公顷·年（即碳汇）。然而，这些计算中并未考虑火灾的影响。已将澳大利亚北领地阿纳姆地大面积湿润稀树草原的净生态系统生产力估算值与遥感估算的火烧面积及相关排放量相结合。将净生态系统生产力估算值与精确的火灾数据相结合，可得出净生物群系生产力（NBP）的估算值，这是一个生产指数，包括因干扰（火灾）导致的碳损失，因此是该生物群落碳固存率更现实的指标。这一初步分析表明，净生物群系生产力约为-1吨碳/公顷·年（即碳汇）。年火烧面积的减少可能会增加碳汇规模。文中讨论了这些净生物群系生产力估算值的不确定性以及这些不确定性对这些广阔地区土地管理的影响。
