Kyushu University Forest, Kyushu University, 394 Tsubakuro, Sasaguri, Fukuoka, 811-2415, Japan.
Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan.
Sci Rep. 2021 Jan 25;11(1):2200. doi: 10.1038/s41598-021-81191-x.
Rawanbuki, a variety of Japanese butterbur (Petasites japonicus subsp. giganteus), grow naturally along the Rawan River, Hokkaido, northern Japan. Most plants reach 2-3 m in height and 10 cm in diameter in 2 months and are much larger than those grown along other rivers. We examined the hypothesis that nutrients exported from upland streams enhance the growth of the Rawanbuki. Nutrient concentrations, including nitrogen, phosphorus, and base cations, in the Rawan River were much higher than those in rivers of adjacent watersheds. High nutrient concentrations and moisture contents were found in soil along the Rawan River and a significant relationship was found between physicochemical soil conditions and aboveground biomass of butterburs. This indicates that extremely large Rawanbuki plants could be caused by these high nutrient concentrations and moisture contents in the soils. A manipulation experiment showed that fertilization simulated the growth environment along the Rawan River and enhanced the stem height and stem diameter of butterburs. This study concluded that the extremely large butterburs are caused by a large amount of nutrients exported from upland areas. These results are the first demonstration of the role of stream water nutrients in enlarging agricultural crops.
瓦万布基，一种日本毛莲菜（Petasites japonicus subsp. giganteus）的变种，自然生长于日本北海道然别川。两个月内，大多数植株可长至 2-3 米高，10 厘米粗，比其他河流生长的植株大得多。我们检验了一个假说，即从高地溪流输出的养分可促进瓦万布基的生长。然别川的养分浓度（包括氮、磷和碱基阳离子）远高于邻近流域河流的养分浓度。然别川沿岸土壤中的养分浓度和湿度都很高，毛莲菜地上部分生物量与土壤理化性质之间存在显著关系。这表明，土壤中极高的养分浓度和湿度可能导致了如此巨大的瓦万布基植株的形成。一项操作实验表明，施肥模拟了然别川沿岸的生长环境，从而促进了毛莲菜的茎高和茎径生长。本研究得出结论，大量从高地输出的养分导致了巨型毛莲菜的形成。这些结果首次证明了溪流水中养分在扩大农作物方面的作用。
