松嫩碱化草甸土壤种子库格局、动态研究进展

草地退化是全球干旱和半干旱草地生态系统的共同特征,由于土壤种子库在植被恢复和生物多样性维持等方面的重要作用,已成为研究热点。作为重要的脆弱生态系统,松嫩碱化草甸在人类活动和全球变化影响下发生了明显退化。松嫩碱化草甸土壤种子库研究始于20世纪90年代,主要集中在对虎尾草群落、星星草群落、碱蓬群落、羊草群落等不同演替阶段土壤种子库物种种类、密度、季节变化研究;该地区土壤种子库的物种数目随着恢复演替由初级向高级阶段而呈现逐渐增加的趋势,但物种数目均相对较少,且多以1年生为主。另外对种子雨和某些物种种子散布动态也有零星报道,主要是从群落水平进行的研究,种子雨的空间异质性表现在其组成和大小因群落而异。今后需要加强对松嫩碱化草甸土壤种子库格局与关键生境要素的耦合特征、种子库分布格局的形成机制等研究,研究方法上,引入稳定同位素标记和分子遗传学等研究方法和手段,开展持久种子库的长期定位监测研究,为盐碱地植被恢复提供理论依据。

Advances in research on the seed bank of a saline-alkali meadow in the Songnen Plain

Grassland degradation is common in arid and semi-arid areas of the world. The soil seed bank plays a critical role in vegetation restoration and biodiversity maintenance and has become a hot research topic. Due to human activities and global climate change, the Songnen meadow is being degraded by salinization, and about 90% of the Leymus chinensis vegetation has been degraded. This perennial grass was a high quality and useful species in this area before the 1960s. With the increase in degradation, i.e. increase in soil saline-alkalinity, secondary succession in this grassland began. In light saline-alkali areas, the dominant species is still L. chinensis. However, bare-soil patches occur in the most severe saline-alkali areas with high soil pH, in some of these patches Suaeda glauca grows only in the rainy season. In some moderate saline alkali areas, Chloris virgata, Puccinellia tenuiflora, Kochia sieversiana communities have appeared. The soil seed bank in the Songnen saline-alkali meadow has been investigated since the 1990s, with a focus on the floristics, seed density and seasonal dynamics in the succession stages of the Chloris virgata, Puccinellia tenuiflora, Kochia sieversiana, and Aeluropus sinensis communites and on the bare-soil saline-alkali patches. Seed rain and seed dispersal also have been investigated in several species. This paper summarizes these reports and points out problems that still exist. Researches on the following aspects of the ecology of this grassland should be increased in the future. Firstly, the mechanisms in the pattern of soil seed bank formation and the relationship between the seed bank pattern and the critical ecological environment factors such as soil salinity, soil pH, soil moisture, wind and so on should be investigated. Secondly, long-term monitoring of the persistent soil seed bank should be undertaken. Thirdly, some new technologies and methods should be introduced to help obtain more accurate and detailed research results on the soil seed bank.