Enhanced Australian carbon sink despite increased wildfire during the 21st century
Enhanced Australian carbon sink despite increased wildfire during the 21st century
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DOI：
10.1088/1748-9326/9/10/104015
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发表时间：
2014-10
影响因子：
6.7
通讯作者：
D. Kelley;Sandy P. Harrison
中科院分区：
文献类型：
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作者：
D. Kelley;Sandy P. Harrison
气候预测显示，澳大利亚在21世纪将显著变暖，大陆大部分地区的降水量将减少。这种变化通常被认为会增加野火的风险。然而，我们表明，澳大利亚南部的燃烧面积增加，但在澳大利亚北部减少。总体而言，预估的火灾增加很小（占土地面积的0.72-1.31%，具体取决于所使用的气候情景），并且不会导致碳储量的减少。事实上，碳储量增加了3.7-5.6 Pg C（取决于所使用的气候情景）。利用基于过程的植被动态、植被-火灾相互作用和碳循环模型，我们发现，火灾的增加促进了林地向更适应火灾的树木的转变，并促使它们向草原的侵蚀，森林面积总体增加了3.9-11.9%。这两种变化都增加了碳的吸收和储存。木本植被的增加增加了粗凋落物的数量，而粗凋落物的腐烂速度比细凋落物慢，因此导致总体异养呼吸的相对减少，进一步减少了碳损失。二氧化碳的直接影响增加了树木覆盖、水利用效率和生产力，因此与二氧化碳保持在现代值不变的模拟相比，碳储量增加了8.5-14.8 Pg C。在干旱地区，CO2效应往往会增加燃烧面积、火通量，从而增加碳损失，但在树木繁茂的地区，CO2效应会增加植被密度，减少燃烧面积。
Climate projections show Australia becoming significantly warmer during the 21st century, and precipitation decreasing over much of the continent. Such changes are conventionally considered to increase wildfire risk. Nevertheless, we show that burnt area increases in southern Australia, but decreases in northern Australia. Overall the projected increase in fire is small (0.72–1.31% of land area, depending on the climate scenario used), and does not cause a decrease in carbon storage. In fact, carbon storage increases by 3.7–5.6 Pg C (depending on the climate scenario used). Using a process-based model of vegetation dynamics, vegetation–fire interactions and carbon cycling, we show increased fire promotes a shift to more fire-adapted trees in wooded areas and their encroachment into grasslands, with an overall increase in forested area of 3.9–11.9%. Both changes increase carbon uptake and storage. The increase in woody vegetation increases the amount of coarse litter, which decays more slowly than fine litter hence leading to a relative reduction in overall heterotrophic respiration, further reducing carbon losses. Direct CO2 effects increase woody cover, water-use efficiency and productivity, such that carbon storage is increased by 8.5–14.8 Pg C compared to simulations in which CO2 is held constant at modern values. CO2 effects tend to increase burnt area, fire fluxes and therefore carbon losses in arid areas, but increase vegetation density and reduce burnt area in wooded areas.