Fates and fingerprints of sulfur and carbon following wildfire in economically important croplands of California, U.S.
Fates and fingerprints of sulfur and carbon following wildfire in economically important croplands of California, U.S.
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DOI：
10.1016/j.scitotenv.2020.142179
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发表时间：
2021-01
期刊：
影响因子：
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通讯作者：
A. Hermes;B. Ebel;S. Murphy;E. Hinckley
中科院分区：
文献类型：
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作者：
A. Hermes;B. Ebel;S. Murphy;E. Hinckley
硫 (S) 广泛用于农业，但人们对其在高地流域内的命运知之甚少，特别是在与野火等干扰相结合的情况下。我们的研究考察了土地利用和野火对生物地球化学“指纹”或硫和碳 (C) 的数量和化学成分的影响。我们在美国加利福尼亚州纳帕河流域进行了研究，那里的葡萄园普遍使用高硫，2017 年 10 月，约 20% 的流域被烧毁，造成了目前在温暖、干燥的美国西部地区常见的干扰。我们使用实验室降雨实验来比较未烧毁和轻度烧毁的葡萄园和草原土壤。然后，我们对具有不同土地利用、燃烧程度和燃烧严重程度的子流域排水的溪流进行了采样，以了解更广泛空间尺度的综合影响。在实验室实验之前，葡萄园土壤的硫含量是草地土壤的 2-3.5 倍，而烧毁的土壤（无论土地用途如何）的碳含量是未烧毁土壤的 1.5-2 倍。在实验室实验中，葡萄园土壤渗滤液中的 S 含量是草地渗滤液的 16-20 倍，而渗滤液中的 C 在不同的土地利用和燃烧土壤类型中变化更大。未燃烧和燃烧的葡萄园土壤浸出的硫的 δ34S 值比草原土壤富集 6-15 ‰，这可能是由于葡萄园土壤中微生物硫的过程所致。排出葡萄园的溪流也有农业硫的指纹，相对于排出非农业地区的溪流，硫浓度高出约 2-5 倍，δ34S-SO42−值富集约 10‰。然而，相对于未燃烧的非农业地区，排出较高比例的燃烧非农业地区的溪流也具有丰富的 δ34S 值，我们将其归因于燃烧过程中 32S 的损失。我们的研究结果说明了野火和土地利用对流域硫和碳循环的相互作用——这是气候变化下的一个新考虑因素，对生态系统功能和人类健康具有重大影响。
Sulfur (S) is widely used in agriculture, yet little is known about its fates within upland watersheds, particularly in combination with disturbances like wildfire. Our study examined the effects of land use and wildfire on the biogeochemical “fingerprints,” or the quantity and chemical composition, of S and carbon (C). We conducted our research within the Napa River Watershed, California, U.S., where high S applications to vineyards are common, and ~ 20% of the watershed burned in October 2017, introducing a disturbance now common across the warmer, drier Western U.S. We used a laboratory rainfall experiment to compare unburned and low severity burned vineyard and grassland soils. We then sampled streams draining sub-catchments with differing land use and degrees of burn and burn severity to understand combined effects at broader spatial scales. Before the laboratory experiment, vineyard soils had 2–3.5 times more S than grassland soils, while burned soils—regardless of land use—had 1.5–2 times more C than unburned soils. During the laboratory experiment, vineyard soil leachates had 16–20 times more S than grassland leachates, whereas leachate C was more variable across land use and burn soil types. Unburned and burned vineyard soils leached S with δ34S values enriched 6–15‰ relative to grassland soils, likely due to microbial S processes within vineyard soils. Streams draining vineyards also had the fingerprint of agricultural S, with ~2–5 fold higher S concentrations and ~ 10‰ enriched δ34S-SO42−values relative to streams draining non-agricultural areas. However, streams draining a higher fraction of burned non-agricultural areas also had enriched δ34S values relative to unburned non-agricultural areas, which we attribute to loss of32S during combustion. Our findings illustrate the interacting effects of wildfire and land use on watershed S and C cycling—a new consideration under a changing climate, with significant implications for ecosystem function and human health.