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西天山野果林准噶尔山楂土壤种子库海拔梯度分布格局

Distribution patterns of the soil seed bank of Crataegus songarica K. Koch with altitude in the western Tianshan wild fruit forest

  • 摘要: 通过野外调查采样和室内实验的方法,对西天山野果林中新疆特有珍稀植物准噶尔山楂(Crataegus songarica K. Koch)土壤种子库组成、空间分布特征及其幼苗更新情况进行分析,并对该物种土壤种子库海拔梯度分布格局进行探讨。结果显示:(1)准噶尔山楂土壤种子库中虫蛀种子、实心种子和饱满种子分别占总种子数的50.83%、46.22%和2.95%;各海拔内饱满种子数量极少,随着海拔上升基本呈现先降后增再降的波动变化趋势,最高密度为(2.36 ± 0.71)粒/m2,出现在海拔1400 ~ 1500 m处。(2)土壤种子库垂直分布中,各土层内以虫蛀种子居多,其次为实心种子,饱满种子密度极显著低于前二者,且各土层间饱满种子密度差异不显著;水平分布上,随着离母树距离的增加,土壤种子库虫蛀、实心和饱满种子密度基本上呈递减的趋势,约94%的饱满种子分布在距母树3 m冠幅范围内。(3)幼苗为近母树分布(2.5 m内),幼苗数量少,实生苗更少,不足1株/50 m2,种苗转化率仅为5‰,趋向于以萌生的无性繁殖为主,实生的有性繁殖为辅。研究结果表明,自然条件下准噶尔山楂种子密度受海拔梯度影响小,种子更新能力差。可以通过调节立地环境因子、改善种子的着地生境,从而提高种苗转化率,促进种群的良好更新。

     

    Abstract: We studied the composition and spatial distribution characteristics of the soil seed bank and seedling renewal rate of the rare Crataegus songarica plant in the Western Tianshan Wild Fruit Forest in Xinjiang along the altitudinal gradient, combining field sampling, laboratory experiments, and data analysis. Results showed that: (1) Wormy seeds, solid seeds, and plump seeds accounted for 50.83%, 46.22%, and 2.95% of the total C. songarica soil seed bank, respectively. The number of plump seeds at each altitude was very low, but showed a fluctuating trend with altitude (first decreasing, then increasing, then decreasing again), reaching a maximum density of (2.36 ± 0.71) grains/m2 at 1400–1500 m. (2) For vertical distribution of the soil seed bank, wormy seeds were dominant in each soil layer, followed by solid seeds, with the density of plump seeds significantly lower than both. The density of plump seeds did not differ significantly between soil layers. For horizontal distribution, the density of wormy seeds, solid seeds, and plump seeds in the soil seed bank showed a decreasing trend with increasing distance from the C. songarica mother plant, with 94% of plump seeds distributed within 3 m of the mother plant. (3) Seedlings were also distributed near the mother plant (within 2.5 m). There were few seedlings, and the number of seed seedlings was even less (< one strain/50 m2). The seedling conversion rate was only 5‰, dominated by emergent asexual reproduction supplemented with native sexual reproduction. In conclusion, C. songarica seed density was not significantly affected by the altitudinal gradient and seed renewal ability was poor under natural conditions. Thus, C. songarica seedling conversion and renewal could be promoted by regulating environmental factors and improving seed habitat.

     

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