CO 2 -fertilisation enhances resilience to browsing in the recruitment phase of an encroaching savanna tree
CO 2 -fertilisation enhances resilience to browsing in the recruitment phase of an encroaching savanna tree
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CO 2 施肥增强了入侵稀树草原树补充阶段的浏览能力
DOI：
10.1111/1365-2435.14215
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发表时间：
2022
影响因子：
5.2
通讯作者：
Ripley B
中科院分区：
文献类型：
--
作者：
Ripley B
CO2施肥与热带稀树草原的广泛而显著的木本侵蚀有关，这是由于CO2刺激的地下储量增加，增强了火灾后的树苗再生。然而，在热带稀树草原，草食动物的其他主要干扰，CO2浓度（[CO2]）对树的反应的影响，知之甚少。草食动物的反应不能从火的反应来预测，因为草食动物的影响发生在建立的早期，并通过植物的适口性和防御而不是地下的碳积累来调节。草食动物和[CO2]之间的关系在这里使用一种广泛的，强烈侵入的稀树草原树Vachellia karroo来探索。使用温室种植的幼苗在过去通过预测未来-[CO2]（180-1000 ppm）和在环境[CO2]下田间生长的幼苗，我们评估了植物的存活、生长、防御和适口性。增加[CO2]通过刺激生长和允许更早达到与存活相关的临界大小阈值来提高温室生长的幼苗对草食动物的耐受性，从而降低了在脆弱的补充阶段发生致命食草动物的可能性。升高的[CO2]也减少了达到第二个大小阈值所需的时间，这与食草动物后田间生长的幼苗的加速恢复有关。幼苗生长对增加[CO2]的反应是非线性的，这表明历史上的生长和生存增强小于未来的预测。增加[CO2]与更大的抗食草动物（更多的分支芽结构），但不是叶适口性（C：N比）或防御（叶单宁和脊柱密度）。在南部非洲稀树草原上，石灰岩密度已经成为一个主要的土地管理问题。然而，在未来的[CO2]下，这种物种以及其他热带稀树草原树种的入侵可能会大大加剧，因为在补充阶段对食草动物的耐受性进一步增强。阅读期刊博客上这篇文章的免费简明语言摘要。
CO2‐fertilisation is implicated in the widespread and significant woody encroachment of savannas due to CO2‐stimulated increases in below‐ground reserves that enhance sapling regrowth after fire. However, the effect of CO2concentration ([CO2]) on tree responses to the other major disturbance in savannas, herbivory, is poorly understood. Herbivory responses cannot be predicted from fire responses, as herbivore effects occur earlier during establishment and are moderated by plant palatability and defence rather than below‐ground carbon accumulation.The relationship between herbivory and [CO2] is explored here using a widespread, strongly encroaching savanna tree,Vachellia karroo. Using greenhouse‐grown seedlings under past—through to predicted future—[CO2] (180–1000 ppm) and field‐grown seedlings under ambient [CO2], we assessed plant survival, growth, defence and palatability.Increasing [CO2] improves the tolerance of greenhouse‐grown seedlings to herbivory by stimulating growth and allowing a critical size threshold associated with survival to be reached earlier, thereby decreasing the probability of fatal herbivory during the vulnerable recruitment phase. Elevated [CO2] also decreases the time taken to reach a second size threshold linked to accelerated recovery of field‐grown seedlings following herbivory. Seedling growth responses to increasing [CO2] are nonlinear, suggesting that historic growth and survival enhancements are smaller than those predicted for the future. Increasing [CO2] is associated with greater resistance to herbivores (more branched shoot architecture) but not leaf palatability (C:N ratio) or defence (leaf tannins and spine density).IncreasingV. karroodensities already constitute a major land management problem in southern African savannas. However, encroachment by this species, and likely other savanna tree species, may be greatly exacerbated under future [CO2], as tolerance to herbivory at the recruitment stage is further enhanced.Read the free Plain Language Summary for this article on the Journal blog.