农田开垦对三江平原湿地土壤种子库影响及湿地恢复潜力

种子库是湿地植被恢复的重要途径之一,不同时期的耕作土壤中残留的种子对开垦湿地恢复具有重要的作用.本文采用温室萌发法在两种水分条件下对三江平原天然湿地、不同开垦年限湿地种子库结构和规模进行了研究,以了解不同开垦年限湿地种子库特征及其在湿地植被恢复中的潜力.本次实验共萌发物种50种,随着开垦年限增加,萌发物种逐渐减少,天然湿地、开垦1年、3年、10年、20年的湿地分别为34种、31种、21种、21种和8种,萌发物种数与种子库规模均表现出极显著差异(F1=8.32,F2=5.946,P＜0.001).种子库密度以天然湿地和开垦1年湿地最大,分别为7624粒/m2,9836粒/m2.随着开垦年限增加,种子库规模逐渐减小,开垦3年、10年种子库密度为4336粒/m2,4872粒/m2.开垦20 a后,显著减少为432粒/m2.湿润条件下萌发物种数及种子密度显著高于淹水处理,种子库具有明显的分层现象,0-5 cm土层种子库规模显著高于5-10 cm.小叶章(Calamagrostis angustifolia)作为该地区优势物种,由最初的1192粒/m2,经过20 a开垦后在种子库中消失.研究表明,在一定的开垦年限范围内,开垦湿地土壤中仍然保留大量的湿地物种种子,在湿地恢复中具有重要的作用.

Effects of farming on wetland soil seed banks in the Sanjing Plain and wetland restoration potential

Seed banks are an important source of regenerative material in wentlands, and can be of value in the restoration of farmed wetlands if the seeds can survive periods of cultivation. A seed bank assay was performed in a greenhouse under two water regimes to evaluate the community structure of the soil seed bank of natural versus farmed wetlands for different years in the Sanjiang Plain of northeastern China. The seeds of fifty plant species germinated from the seed bank. The number of species germinated from seed banks decreased gradually with the increase of the farm years, which were 34, 31, 21, 21 and 8 in natural wetland and farmed wetlands for 1yr, 3yrs, 10yrs and 20yrs respectively. One-way ANOVA was performed and showed that mean species richness and seedling density of seed banks have significant difference among habitats(F₁=8.32,F₂=5.946,P<0.001).The seed density of the natural wetland and wetland farmed for 1yr were 7624 individuals/m², 9836 individuals/m², much higher than that in wetlands farmed for 3yrs and 10yrs, whose seed density were 4336individuals/m², 4872individuals/m² respectively. The lowest of seed density occurred in wetland farmed for 20yrs, which was only 432 individuals/m². The number of species and seedling density of seed banks under drawdown condition were significantly higher than that under flooded condition. Seed density varied with depth so that seed density was higher in 0-5cm than in 5-10cm. Calamagrostis angustifolia, the dominant species in the vegetation of the Sanjiang Plain had 1192 individuals/m² germinating in the seed bank from the natural wetland; this species was absent in seed banks after 20 years of farming. Our research suggests that even after several years of farming that these wetlands retain the seeds of many species, which can be valuable for wetland restoration.