Nikko Botanical Garden, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tochigi, Japan.
Laboratory of Radiocarbon Dating, The University of Museum, The University of Tokyo, Tokyo, Japan.
Sci Rep. 2021 Jun 1;11(1):11497. doi: 10.1038/s41598-021-91078-6.
Plants have difficulty absorbing phosphorus from volcanic ash soils owing to the adsorption of phosphorus by aluminum and iron in the soils. Thus, on volcanic ash soils, the phosphorus source for natural vegetation is expected to be organic matter, however, there is a lack of experimental evidence regarding this occurrence. Here, we studied the effect of organic matter on plant growth of some species that occur in primary successions of volcanic ash soil ecosystems, based on growth experiments and chemical analyses. We found that a large amount of inorganic phosphorus (but only a limited amount of inorganic nitrogen) is leached from fresh leaf litter of the pioneer spices Fallopia japonica at the initial stage of litter decomposition. Phosphorus from the fresh litter specifically activated the growth of subsequently invading nitrogen-fixing alder when immature volcanic soil was used for cultivation. In contrast, old organic matter in mature soil was merely a minor source of phosphorus. These results suggest that fresh litter of F. japonica is essential for growth of nitrogen-fixing alder because the litter supplies phosphorus. We consider that rapid phosphorus cycles in fresh litter-plant systems underlie the productivity of natural vegetation even in mature ecosystems established on volcanic ash soils.
由于土壤中的铝和铁对磷的吸附作用，植物从火山灰土壤中吸收磷较为困难。因此，在火山灰土壤中，天然植被的磷源预计来自有机物，但关于这种情况的实验证据还很缺乏。在这里，我们基于生长实验和化学分析，研究了有机物对一些出现在火山灰土壤生态系统演替初期的物种的植物生长的影响。我们发现，在凋落叶分解的初始阶段，先锋种日本葛藤的新鲜凋落叶会淋溶出大量无机磷（但只有有限量的无机氮）。当使用未成熟火山土进行种植时，来自新鲜凋落物的磷专门激活了随后入侵的固氮桤木的生长。相比之下，成熟土壤中的旧有机物只是磷的次要来源。这些结果表明，日本葛藤的新鲜凋落物是固氮桤木生长所必需的，因为凋落物提供了磷。我们认为，即使在建立在火山灰土壤上的成熟生态系统中，新鲜凋落物-植物系统中的快速磷循环也是天然植被生产力的基础。
