Evaluation of the Impacts of Marine Salts and Asian Dust on the Forested Yakushima Island Ecosystem, a World Natural Heritage Site in Japan
Evaluation of the Impacts of Marine Salts and Asian Dust on the Forested Yakushima Island Ecosystem, a World Natural Heritage Site in Japan
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海洋盐分和亚洲沙尘对日本世界自然遗产屋久岛森林生态系统的影响评估
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
K. Satake
中科院分区：
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作者：
T. Nakano;Y. Yokoo;M. Okumura;S. Jean;K. Satake
为了阐明空气传播物质对日本屋久岛生态系统的影响，我们测定了溪流、土壤、植被和岩石中的元素组成以及 Sr 和 Nd 同位素比率。溪水的Na和Cl含量较高，Ca和HCO3含量较低，Na/Cl和Mg/Cl比值接近海水，但pH值较低（5.4至7.1），Ca/Cl比值高于海水，并且根据基岩类型不同，87Sr/86Sr比值也不同。通过假设 Cl 源自海盐气溶胶来估计，溪水中源自雨水的阳离子的比例平均为 Na 81%、Mg 83%、K 36%、Ca 32% 和 Sr 33%。Sr 值与通过比较雨水和花岗岩基岩之间的 Sr 同位素比率估计的 28% 相当。与母质相比，土壤中的钙、钠、磷和锶含量较低。在西北侧的四濑，植物和土壤池的 87Sr/86Sr 比率与海盐成分较高的雨水相似。相比之下，A层和B层土壤矿物的Sr和Nd同位素比接近中国北方黄土中硅酸盐矿物的同位素比。土壤钙和磷的消耗主要是由于花岗岩中斜长石和少量磷灰石和方解石的化学风化造成的。这表明屋久岛的生态系统受到大量海盐成分较高的酸性降水的影响，这些降水将钙及其代理物（Sr）从基岩中浸出到溪流中，并受到亚洲尘埃衍生的磷灰石的影响，磷灰石是碱性阳离子贫化土壤中磷的重要来源。
To elucidate the influence of airborne materials on the ecosystem of Japan’s Yakushima Island, we determined the elemental compositions and Sr and Nd isotope ratios in streamwater, soils, vegetation, and rocks. Streamwater had high Na and Cl contents, low Ca and HCO3 contents, and Na/Cl and Mg/Cl ratios close to those of seawater, but it had low pH (5.4 to 7.1), a higher Ca/Cl ratio than seawater, and distinct 87Sr/86Sr ratios that depended on the bedrock type. The proportions of rain-derived cations in streamwater, estimated by assuming that Cl was derived from sea salt aerosols, averaged 81 % for Na, 83 % for Mg, 36 % for K, 32 % for Ca, and 33 % for Sr. The Sr value was comparable to the 28 % estimated by comparing Sr isotope ratios between rain and granite bedrock. The soils are depleted in Ca, Na, P, and Sr compared with the parent materials. At Yotsuse in the northwestern side, plants and the soil pool have 87Sr/86Sr ratios similar to that of rainwater with a high sea salt component. In contrast, the Sr and Nd isotope ratios of soil minerals in the A and B horizons approach those of silicate minerals in northern China’s loess soils. The soil Ca and P depletion results largely from chemical weathering of plagioclase and of small amounts of apatite and calcite in granitic rocks. This suggests that Yakushima’s ecosystem is affected by large amounts of acidic precipitation with a high sea salt component, which leaches Ca and its proxy (Sr) from bedrock into streams, and by Asian dust-derived apatite, which is an important source of P in base cation-depleted soils.