ABSTRACT

Windswept Sasa grasslands are stable communities but may have the potential to change into other vegetation such as forests through germination of the soil seed bank. I investigated the compositions of the vegetation and soil seed banks in two windswept Sasa grasslands in the Tanzawa Mountains, eastern Japan: Ryugababa (RGB) and Fudonomine (FDM). Tall tree and sub-tall tree seedlings were present in both grasslands but were below a dense cover of Sasa hayatae. The number of buried viable seeds was estimated as 2831 seeds m⁻² comprising 39 species at RGB and 5786 seeds m⁻² comprising 58 species at FDM, 70% of which were graminoids and 5−23% of which were sub-tall trees at both sites. Most sub-tall tree seeds were Weigela decora, which forms windswept scrub forests around Sasa grasslands. No seedlings of S. hayatae germinated from any of the soil seed bank samples. A habitat type analysis of the soil seed banks showed that the “other” type (species that are infrequent or do not belong to a particular plant association) had the highest relative dominance (approximately 70%), followed by windswept scrub forest (13−25%) at both sites. Sørensen’s similarity index between the vegetation and soil seed bank was low (39.6% in RGB and 47.1% in FDM), possibly because the dense Sasa cover prevents seedlings from germinating and growing. These results suggest that the soil seed banks in windswept Sasa grasslands have different species compositions from the vegetation and consequently have the potential to cause a shift to W. decora scrub forest.

摘要

风吹拂的萨沙草原是稳定的社区，但可能通过土壤种子库的发芽而转变为其他植被，例如森林。我调查了日本东部Tanzawa山上两个风吹拂的Sasa草原上的植被和土壤种子库的成分：Ryugababa（RGB）和Fudonomine（FDM）。这两个草原上都存在高大的树和次高大的树苗，但都在密集的Sasa hayatae之下。埋藏的可存活种子的数量估计为2831种子m ^-2，包括RGB的39种种子和5786种子m ^-2，包括58种在FDM的种子，其中70％是类粉虱，而5-23％是次高大的树木。两个站点。大多数次高大的树木种子是韦格拉（Weigela decora），在萨沙（Sasa）草原周围形成风吹拂的灌木林。没有从任何土壤种子库样品中发芽的S. hayatae幼苗。对土壤种子库的栖息地类型分析表明，“其他”类型（不常见或不属于特定植物群落的物种）具有最高相对优势度（大约70％），其次是风吹灌丛的森林（13− 25％）。Sørensen在植被和土壤种子库之间的相似性指数很低（RGB为39.6％，FDM为47.1％），这可能是因为密集的Sasa覆盖物阻止了幼苗发芽和生长。这些结果表明被风吹扫的莎莎的土壤种子库草原具有与植被不同的物种组成，因此有可能导致向W. decora灌丛森林转移。