Forest Fire History in Amazonia Inferred From Intensive Soil Charcoal Sampling and Radiocarbon Dating
Forest Fire History in Amazonia Inferred From Intensive Soil Charcoal Sampling and Radiocarbon Dating
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DOI：
10.3389/ffgc.2022.815438
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发表时间：
2022-05
影响因子：
4
通讯作者：
T. Feldpausch;L. Carvalho;K. Macario;P. Ascough;César F. Flores;E. H. Coronado;Michelle Kalamandeen;O. Phillips;R. Staff
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作者：
T. Feldpausch;L. Carvalho;K. Macario;P. Ascough;César F. Flores;E. H. Coronado;Michelle Kalamandeen;O. Phillips;R. Staff
火在热带森林中具有历史作用，与过去的气候和跨越全新世的古代土地利用有关;然而，从木炭记录中还不清楚火在不同时空尺度上是如何变化的，以及需要什么样的采样策略来确定火的历史及其影响。我们评估火灾的变化，结构完整，terra-firme亚马逊森林，密集的土壤木炭采样从三个重复的土坑在圭亚那和北方和南部秘鲁的网站。我们使用放射性碳（14 C）测量来评估（1）在当地，我们样本中所代表的火灾时间如何在森林地块的表面和土壤深度上变化，（2）流域范围内，火灾的年龄如何在气候和环境梯度上变化，以及（3）当应用14 C方法评估最后一次火灾的日期时，有多少样本是合适的。考虑到所有的14 C日期（n = 33），最近的火灾发生在类似的时间在每个三个网站（中位年龄：728-851卡年BP），表明在火灾干扰至少，这些森林可以被认为是古老的增长。独特的火灾事件的数量范围从1至4个坑，从4至6个每个网站。根据我们的抽样策略，北秘鲁网站，年降水量最高的火灾事件。中位火返回间隔从455到2,950 cal年BP之间的网站。根据现有的日期，至少需要三个样本（从三个坑的顶部各取一个）进行采样，以便有合理的可能性捕捉到最近没有火灾历史的森林的最近火灾。两个地点的最大火灾重现期比上一次火灾发生后的时间短，这表明在过去的1800年里，这些森林经历了比过去2000 - 3500年更长的无火期。我们对陆地森林土壤的分析有助于提高对火灾状况变化的理解，评估现代植被和土壤火灾后遗产所需的信息，并校准模型以预测气候变化下森林对火灾的反应。
Fire has a historical role in tropical forests related to past climate and ancient land use spanning the Holocene; however, it is unclear from charcoal records how fire varied at different spatiotemporal scales and what sampling strategies are required to determine fire history and their effects. We evaluated fire variation in structurally intact, terra-firme Amazon forests, by intensive soil charcoal sampling from three replicate soil pits in sites in Guyana and northern and southern Peru. We used radiocarbon (14C) measurement to assess (1) locally, how the timing of fires represented in our sample varied across the surface of forest plots and with soil depth, (2) basin-wide, how the age of fires varies across climate and environmental gradients, and (3) how many samples are appropriate when applying the 14C approach to assess the date of last fire. Considering all 14C dates (n = 33), the most recent fires occurred at a similar time at each of the three sites (median ages: 728–851 cal years BP), indicating that in terms of fire disturbance at least, these forests could be considered old-growth. The number of unique fire events ranged from 1 to 4 per pit and from 4 to 6 per site. Based upon our sampling strategy, the N-Peru site—with the highest annual precipitation—had the most fire events. Median fire return intervals varied from 455 to 2,950 cal years BP among sites. Based on available dates, at least three samples (1 from the top of each of 3 pits) are required for the sampling to have a reasonable likelihood of capturing the most recent fire for forests with no history of a recent fire. The maximum fire return interval for two sites was shorter than the time since the last fire, suggesting that over the past ∼800 years these forests have undergone a longer fire-free period than the past 2,000–3,500 years. Our analysis from terra-firme forest soils helps to improve understanding of changes in fire regime, information necessary to evaluate post-fire legacies on modern vegetation and soil and to calibrate models to predict forest response to fire under climate change.