Grasslands may be more reliable carbon sinks than forests in California
Grasslands may be more reliable carbon sinks than forests in California
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DOI：
10.1088/1748-9326/aacb39
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发表时间：
2018-07-01
影响因子：
6.7
通讯作者：
Warlind, David
中科院分区：
文献类型：
--
作者：
Dass, Pawlok;Houlton, Benjamin Z.;Warlind, David
虽然自然陆地生态系统已经吸收了大约25%的人为二氧化碳排放量，但这一关键生态系统服务的长期可持续性受到质疑。森林传统上被视为强大的碳（C）汇;然而，极端热浪，干旱和野火增加了树木死亡率，特别是在广泛的半干旱地区，占地球陆地面积的41%。使用一组建模实验，我们表明，加州草原是一个更有弹性的碳汇比森林在应对21世纪世纪的气候变化，设计气候智能的上限和贸易抵消政策的影响。草原对气温上升、干旱和火灾的适应能力，加上C优先储存在地下汇中，有助于保护被隔离的陆地C，防止其重新进入大气。相比之下，加州的森林似乎无法科普全球气候的急剧变化，至少在世纪中期，它将从大量的碳汇转变为碳源。这些结果突出了在缺乏管理干预措施的情况下依赖森林碳抵消的固有风险，以避免大量火灾驱动的碳排放。另一方面，由于草原环境，包括树木稀疏的牧场，似乎更有能力维持碳汇在21世纪世纪，这样的生态系统应被视为一个替代的碳抵消气候脆弱的森林。加州碳市场气候智能方法的进一步发展可以作为抵消世界各地项目的一个例子，特别是那些扩展到广泛干旱和半干旱地区的项目。
Although natural terrestrial ecosystems have sequestered similar to 25% of anthropogenic CO2 emissions, the long-term sustainability of this key ecosystem service is under question. Forests have traditionally been viewed as robust carbon (C) sinks; however, extreme heat-waves, drought and wildfire have increased tree mortality, particularly in widespread semi-arid regions, which account for similar to 41% of Earth's land surface. Using a set of modeling experiments, we show that California grasslands are a more resilient C sink than forests in response to 21st century changes in climate, with implications for designing climate-smart Cap and Trade offset policies. The resilience of grasslands to rising temperatures, drought and fire, coupled with the preferential banking of C to belowground sinks, helps to preserve sequestered terrestrial C and prevent it from re-entering the atmosphere. In contrast, California forests appear unable to cope with unmitigated global changes in the climate, switching from substantial C sinks to C sources by at least the mid-21st century. These results highlight the inherent risk of relying on forest C offsets in the absence of management interventions to avoid substantial fire-driven C emissions. On the other hand, since grassland environments, including tree-sparse rangelands, appear more capable of maintaining C sinks in 21st century, such ecosystems should be considered as an alternative C offset to climate-vulnerable forests. The further development of climate-smart approaches in California's carbon marketplace could serve as an example to offset programs around the world, particularly those expanding into widespread arid and semi-arid regions.