土壤筛对喀斯特地区不同植被类型土壤种子库的分选效果

Separation Effect of Soil Sieves on Separating Soil Seed Bank of Different Vegetation Types in Karst Region

采用土壤分析筛分离处理和室内萌发试验,对桂西北喀斯特退化生态系统不同植被类型土壤种子粒径进行了研究。结果表明,在0～15cm的土层中,草地土壤种子库密度为1955粒m-2,灌丛次之,为1850粒m-2,次生林地最少,仅有665粒m-2;垂直剖面上,草地和灌丛土壤种子集中分布在0～2cm土层,而次生林地种子主要分布于5cm以下;草地可萌发种子总量的99%集中于>0.25mm粒径,灌丛与次生林地主要集中在>0.25mm和≤0.177mm粒径;透过0.177～0.25mm的土壤萌发种子数量很少,3类样地分别仅为0.5%、1.4%和2.2%。因此,喀斯特地区退化生态系统草地土壤种子分离的最小孔径确定为0.25mm,灌丛和次生林地透过0.177～0.25mm筛孔的土壤可不进行萌发试验。

In the degraded karst .ecosystem of Northwest Guangxi Autonomous region, seed granular size buried in the soils of different vegetation types （grassland, scrub, secondary forest） was studied systematically, using soil analysis sieves treatment and germination method. For the soil samples in 0-15 cm layer, the results showed that the seed density of grassland was the highest （1955 seeds m^-2 ）, followed by scrub （1850 seeds m^-2 ）, and secondary forest （665 seeds m^-2 ）. Vertically, seeds buried in grassland and scrub soils distributed in soil surface layers （0-2 cm） concentratively, while the seeds of secondary forest distributed below 5cm depth mostly. Around 99% of total germinated seeds of grassland were from the sieve with diameter of 〉0.25mm. However, the germinated seeds of scrub and secondary forest were mainly from the sieve with diameter of 〉0.25mm and ≤0.177mm. The germinated seeds from the 0.177-0.25mm diameter sieve accounted for 0.5%, 1.4 % and 2.2%, respectively. Therefore it could be concluded that 0.42mm diameter sieve was applied to separate soil seed bank of grassland. As to scrub and secondary forest, soil samples of 0.177-0.25mm could not put up germination experiment.