Tropical savannas are characterized by high primary productivity and high fire frequency, such that much of the carbon captured by vegetation is rapidly returned to the atmosphere. Hence, there have been suggestions that management-driven reductions in savanna fire frequency and/or severity could significantly reduce greenhouse gas emissions and sequester carbon in tree biomass. However, a key knowledge gap is the extent to which savanna tree biomass will respond to modest shifts in fire regimes due to plausible, large-scale management interventions. Here, we: (1) characterize relationships between the frequency and severity of fires and key demographic rates of savanna trees, based on long-term observations in vegetation monitoring plots across northern Australia; (2) use these relationships to develop a process-explicit demographic model describing the effects of fire on savanna tree populations; and (3) use the demographic model to address the question: to what extent is it feasible, through the strategic application of prescribed burning, to increase tree biomass in Australian tropical savannas? Our long-term tree monitoring dataset included observations of 12,344 tagged trees in 236 plots, monitored for between 3 and 24 years. Analysis of this dataset showed that frequent high-severity fires significantly reduced savanna tree recruitment, survival, and growth. Our demographic model suggested that: (1) despite the negative effects of frequent high-severity fires on demographic rates, savanna tree biomass appears to be suppressed by only a relatively small amount by contemporary fire regimes, characterized by a mix of low- to high-severity fires; and (2) plausible, management-driven reductions in the frequency of high-severity fires are likely to lead to increases in tree biomass of about 11.0 t DM ha⁻¹ (95% CI: −1.2–20.8) over a century. Accounting for this increase in carbon storage could generate significant carbon credits, worth, on average, three times those generated annually by current greenhouse gas (methane and nitrous oxide) abatement projects, and has the potential to significantly increase the economic viability of fire/carbon projects, thereby promoting ecologically sustainable management of tropical savannas in Australia and elsewhere. This growing industry has the potential to bring much-needed economic activity to savanna landscapes, without compromising important natural and cultural values.

中文翻译：

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使用人口统计模型预测火灾管理对澳大利亚大草原树木生物量的长期影响

热带稀树草原具有高初级生产力和高火灾频率的特点，因此植被捕获的大部分碳会迅速返回大气层。因此，有人建议，管理驱动的稀树草原火灾频率和/或严重程度的减少可以显着减少温室气体排放并封存树木生物量中的碳。然而，一个关键的知识缺口是稀树草原树生物量将在多大程度上响应因合理的大规模管理干预而导致的火灾状况的适度变化。在这里，我们：(1) 根据对澳大利亚北部植被监测地块的长期观察，描述火灾的频率和严重程度与稀树草原树木的关键人口统计率之间的关系；(2) 利用这些关系开发一个过程明确的人口统计模型，描述火灾对稀树草原树种群的影响；(3) 使用人口模型来解决以下问题：通过战略性应用规定的燃烧，在多大程度上增加澳大利亚热带稀树草原的树木生物量是可行的？我们的长期树木监测数据集包括对 236 个地块中 12,344 棵标记树木的观察，监测时间为 3 至 24 年。对该数据集的分析表明，频繁的高强度火灾显着减少了稀树草原树的补充、存活和生长。我们的人口统计模型表明：(1) 尽管频繁的高强度火灾对人口统计率产生了负面影响，但热带草原树木的生物量似乎仅受到当代火灾制度相对较小的抑制，以低到高严重性火灾的混合为特征；(2) 合理的、由管理驱动的高强度火灾频率的减少可能导致树木生物量增加约 11.0 t DM ha⁻¹ (95% CI: −1.2–20.8) 超过一个世纪。考虑到碳储存量的增加，可以产生显着的碳信用额度，其价值平均是当前温室气体（甲烷和一氧化二氮）减排项目每年产生的碳信用额度的三倍，并且有可能显着提高火/碳的经济可行性项目，从而促进澳大利亚和其他地方热带稀树草原的生态可持续管理。这个不断发展的行业有可能在不损害重要的自然和文化价值的情况下，为稀树草原景观带来急需的经济活动。