西天山野果林不同居群黑果小檗土壤种子库及幼苗更新研究

通过野外调查及采集土样,对新疆西天山野果林内黑果小檗(Berberis atrocarpa Schneid.)3个自然居群(霍城、新源和特克斯)的土壤种子库及幼苗更新情况进行研究。结果显示,3个居群内黑果小檗土壤种子质量无显著差异,霍城、新源和特克斯居群黑果小檗土壤种子库中完整种子分别占种子总数的51.6%、49.4%和54.1%。霍城、新源和特克斯居群黑果小檗完整种子均聚集在枯枝落叶层,分别为98.4%、97.4%和100%,3个居群5~10 cm土层均未发现黑果小檗种子。土壤种子水平扩散距离随着坡度的增加逐渐增大。霍城、新源和特克斯居群黑果小檗幼苗均为根蘖苗,根蘖繁殖可使幼苗扩散到母株周围100 cm范围或更远处。Ⅱ级苗(20~40 cm)数量最多,占幼苗总数的50%;3个居群黑果小檗的Ⅰ级苗(0~20 cm)向Ⅱ级苗的转化率均为100%;霍城和新源居群Ⅱ级、Ⅲ级(40~60 cm)苗间的转化率较低,分别为29%和32%,特克斯居群Ⅱ级、Ⅲ级苗间的转化率较高,为78%。研究结果表明西天山野果林黑果小檗种子易滞留于地表,难以进入土壤深层且土壤中种子霉变率高,这可能是黑果小檗自然更新困难的原因。

Research on the soil seed bank and seedling renewal of different populations of Berberis atrocarpa in the Western Tianshan Wild Fruit Forest

The soil seed bank and seedlings of Berberis atrocarpa Schneid. from three wild populations (Huocheng, Xinyuan and Tekesi) within the Western Tianshan Wild Fruit Forest were surveyed. We collected 54 soil samples, which were taken back to the laboratory to collect B. atrocarpa seeds. Results showed that there were no significant differences in the B. atrocarpa seed quality from the three populations. Intact seeds from the seed banks of the Huocheng, Xinyuan and Tekesi populations accounted for 51.6%, 49.4% and 54.1% of the total seeds, respectively. The vertical distribution of the B. atrocarpa seeds was characterized by the accumulation of 98.4% (Huocheng), 97.4% (Xinyuan) and 100% (Tekesi) of whole seeds in the litter layer, with no seeds found in the 5-10 cm soil layer. The horizontal diffusion distance of soil seeds gradually increased with the increase in slope. The B. atrocarpa seedlings in the Huocheng, Xinyuan and Tekesi populations were all root saplings, which allowed the seedlings to spread 100 cm or more from the mother plant. Grade Ⅱ seedlings (20-40 cm) accounted for the largest number (~50% of total seedlings). The transformation rate of Grade Ⅰ seedlings (0-20 cm) to Grade Ⅱ seedlings (20-40 cm) was 100% in all three populations. The conversions between the height stages of Ⅱ and Ⅲ (40-60 cm) in the Huocheng and Xinyuan populations were 29% and 32%, respectively, which were significantly lower than the 78% in the Tekesi population. Results showed that the B. atrocarpa seeds in the Western Tianshan Wild Fruit Forest were easily retained on the surface of the soil and the seed mildew rate in the soil was high, which may help explain the difficulty in the natural regeneration of B. atrocarpa.