松嫩草地次生光碱斑种子流及其生态恢复意义

通过陷井法 ,对松嫩草地次生光碱斑的表面种子流、土壤种子库动态进行了分析 ,调查发现次生光碱斑种子流数量巨大 ,种类相当丰富 ;次生光碱斑的表面种子流月份间差异极显著 ,6月份最小 ,10月份最大。次生光碱斑的土壤种子库很小 ,种类单一 ,原有的土壤种子库严重流失 ;与典型羊草群落相比 ,土壤种子库在种类和数量上均有很大差异。次生光碱斑的土壤种子库很小 ,尤其在 5、6月 ,造成次生光碱斑种子极度缺乏 ,是次生光碱斑植物自然恢复进程极其缓慢的重要原因之一。根据种子流的生理 -生态特征和数量特征 ,它对次生光碱斑的植被恢复具有重要意义 ,是潜在种源。

Seed movement in the secondary bare alkali-saline patch and its implication for ecological restoration in the Songnen grassland, northeastern China

Soil seed banks usually play an important role in the vegetation regeneration and succession, and there exists a very close relationship between vegetation dynamics and soil seed bank. Especially for some severely deteriorated ecosystems, soil seed banks are the main available seed source in natural conditions, serving as a template for subsequent successive processes such as germination, competition, growth, and ultimately shaping the stable native communities. Therefore, soil seed bank to some extent can impact the revegetation process and direction. The secondary bare alkali-saline patches (SAP), in this paper, are severely degraded ecosystems caused by irrational exploitation or overuse in the past decades. Through setting seed pitfall traps in the secondary bare alkali-saline patches (SAP) in the Song-nen plain, seed dynamics of SAP, including seed movement over its surface and the seed bank in soil, were investigated during six successive months, which almost coincided with the non-frozen period there. The objective of the study was to evaluate seed movement of SAP and the implication for ecological restoration. The questions were addressed at: (1) how much were seed movement and seed bank in soils of SAP, and what kinds? (2) What was the eco-physiological property of the seed movement like, and whether can they be utilized to improve those secondary bare alkali-saline patches or not, serving as potential important seed sources? The results showed that, the total number of seed movement of secondary bare alkali-saline patch (SAP) was enormous, and species composition was relatively abundant, Including 6 families and 13 genera. Moreover, there exists a significant change in the seed movement in SAP among different months, which being least in June, and most in October, 1111.1 grains/m~(2) and 28210.1 grains/m~(2), respectively. However, seed bank in soil of SAP was minor, and species composition was also quite simple. Of course, soil seed bank in SAP also changes significantly over time. No any soil seed can even be founded in May and June, while in October soil seed bank was relatively high. Compared with the typical Leymus chinense community, the seed band in soil of SAP was very low in August, because the intrinsic surface soil in SAP had been already destroyed seriously and soil seed bank here was lost drastically. Furthermore, seeds of salt-tolerant plants were predominant, not only in the seed movement but also soil seed bank in SAP, especially for Chloris virgata, which accounting for 91.83 % of the total seed movement, next were Suaeda spp. and Puccinellia spp.. Seed movement in SAP should be very important potentially for both scientists and grassland managers to improve or meliorate the secondary bare alkali-saline patches (SAP), serving as direct seed sources in natural conditions, due to their eco-physiological property and quantitative property. Many scientists and managers consider that the extremely high content of soluble saline ion in soil is the dominant cause, which makes the natural revegetation process of these secondary bare alkali-saline patches so slow. However, what is little known is that the deficiency of soil seeds also is another important factor in the SAP, especially in May and June, when it is prime period for native plants to germinate. Therefore, the seed movement should be potentially important seed sources and can be utilized in the revegetation process of the secondary bare alkali-saline patches (SAP).