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Rapid recovery of net ecosystem production in a semi-arid woodland after a wildfire
Agricultural and Forest Meteorology ( IF 6.2 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.agrformet.2020.108099
Qiaoqi Sun , Wayne S. Meyer , Georgia R. Koerber , Petra Marschner

Abstract Altered precipitation regimes and increased temperatures can enhance wildfire risk, particularly in semi-arid and arid ecosystems. Since these ecosystems occupy a third of the earth's land area, the immediate loss of carbon and the post fire reduction in carbon sequestration will significantly affect regional and global carbon budgets. However, there are few studies that quantify the recovery of ecosystem carbon production post fire in semi-arid ecosystems. In January 2014, a wildfire caused severe loss and damage to plants in a semi-arid Eucalyptus woodland in South Australia. The carbon flux of the woodland was monitored pre- and post-fire from an in-situ eddy covariance flux tower. Daily net ecosystem production (NEP), ecosystem respiration (Reco) and gross primary production (GPP), together with environmental variables collected in 2012 and 2013 (pre-fire) were used to generate machine learning regression algorithms. Subsequently, the algorithms were used to simulate Reco, GPP and NEP at the same site without fire from the environmental variables, which is referred to as modelled carbon fluxes. Changes in the difference between the modelled fluxes and the actual post-fire measured fluxes were used to investigate the recovery of Reco, GPP and NEP during four years after the fire (April 2014–March 2018). We found that the woodland was a carbon source throughout the first year and in the hot and dry months of the second year, but was a carbon sink in the third and fourth year after the fire. The recovery of NEP to pre-fire levels was estimated to take approximately 35 months (30–43 months at 95% confidence interval). Post fire measured GPP responded more strongly to rainfall events than indicated by the modelled values which suggests that carbon sequestration by new leaf growth is more responsive to rainfall than equivalent mature leaf area of this woodland. After four years, both measured Reco and GPP rates were still lower than modelled rates indicating that the mass of carbon and its turnover in the ecosystem was not yet at pre-fire levels. We conclude that full recovery from fire in this woodland, and likely in similar ecosystems, is strongly influenced by the incident rainfall regime after fire and will take five years or more, especially if total annual rainfall is less than the long term average.

中文翻译:

野火后半干旱林地净生态系统产量的快速恢复

摘要 降水状况的改变和温度的升高会增加野火风险,尤其是在半干旱和干旱生态系统中。由于这些生态系统占据了地球陆地面积的三分之一,碳的直接损失和火灾后碳固存的减少将显着影响区域和全球的碳预算。然而,很少有研究量化半干旱生态系统火灾后生态系统碳生产的恢复。2014 年 1 月,一场野火对南澳大利亚半干旱桉树林地的植物造成了严重损失和破坏。林地的碳通量在火灾前和火灾后通过原位涡流协方差通量塔进行监测。每日净生态系统产量 (NEP)、生态系统呼吸 (Reco) 和初级生产总值 (GPP),与 2012 年和 2013 年(火灾前)收集的环境变量一起用于生成机器学习回归算法。随后,这些算法被用于模拟同一地点的 Reco、GPP 和 NEP,没有来自环境变量的火灾,这被称为模拟碳通量。模拟通量与实际火灾后测量通量之间差异的变化用于研究火灾后四年(2014 年 4 月至 2018 年 3 月)Reco、GPP 和 NEP 的恢复情况。我们发现林地在第一年和第二年炎热干燥的月份都是碳源,但在火灾后的第三年和第四年是碳汇。NEP 恢复到火灾前水平估计需要大约 35 个月(95% 置信区间为 30-43 个月)。火灾后测量的 GPP 对降雨事件的反应比模拟值所表明的更强烈,这表明新叶生长的碳固存比该林地的等效成熟叶面积对降雨更敏感。四年后,测量的 Reco 和 GPP 率仍低于模型率,表明生态系统中的碳质量及其周转率尚未达到火灾前的水平。我们得出的结论是,这片林地以及类似生态系统中的火灾完全恢复受火灾后发生的降雨情况的强烈影响,需要五年或更长时间,尤其是如果年总降雨量低于长期平均值。
更新日期:2020-09-01
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