太白山锐齿栎林物种-多度分布格局

Species-abundance distribution patterns of Quercus aliena var. acutiserrata forest in Taibai Mountain, China

以太白山1.5 hm2的锐齿栎原始林和次生林样地中环境因子和胸径≥1 cm的木本植物调查数据为基础,采用统计模型(对数正态模型)、生态位模型(Zipf模型、断棍模型、生态位优先模型)和中性模型,拟合了锐齿栎群落的物种多度分布。结果表明:太白山锐齿栎林物种多度分布格局受到生境异质性的影响。其中,地形因子对原始林物种分布影响较大,在凹凸度较大的生境中,物种分布同时受到中性过程和生态位过程的影响,但中性过程发挥的作用较小;而在凹凸度较小的生境中,中性模型被拒绝,物种的多度分布符合生态位理论的假设。在群落坡度大的区域,群落中生态位过程和中性过程同等重要;而在坡度较小的平缓区域,生态位分化对群落物种分布的影响较大。在次生林中,影响物种分布的因素主要是土壤养分。在次生林土壤速效磷含量高的生境中,生态位过程是影响群落物种分布的主要生态学过程;而在土壤速效磷含量低的生境中,中性过程和生态位过程在群落物种分布中同时存在。太白山锐齿栎林物种多度分布格局存在明显的尺度效应。原始林在20 m×20 m尺度上,生态位模型和中性模型都能预测物种多度分布,而在40 m×40 m和70 m×70 m尺度上,生态位过程可解释物种多度分布格局。在次生林样地20 m×20 m、40 m×40 m、70 m×70 m尺度上,生态位过程和中性过程共同作用于物种的分布,但是生态位过程更为重要。可见,除了尺度和生境异质性外,原始林与受干扰的次生林中的物种多度分布也存在明显的差异。

The statistical model(log-normal model), niche models(Zipf model, broken stick mo-del, niche preemption model), and neutral model were used to fit the species-abundance distribution patterns based on the measurements of environmental factors and inventory data of trees with DBH≥1 cm in a 1.5 hm2 plot in the primary forest(PF) and a 1.5 hm2 plot in the secondary forest(SF). The results showed that species-abundance distribution was affected by habitat heterogeneity in Q. aliena var. acutiserrata forest. Topography had a predominant impact on the species-abundance distribution in PF. Species distribution was affected by both neutral and niche processes, with neutral process having a less prominent effect in large convexity habitats. While the neutral model was rejected by the K-S and Chi-square test in low convexity habitats, the species-abundance distribution satisfied the assumption of niche theory. Niche process and neutral process were equally important in the community in areas with steep slopes, while niche differentiation was the dominant in flat areas. In SF, the main factors affecting species distribution were soil nutrients. The niche process was the mainly ecological process affected species-abundance distribution in habitats with high soil available phosphorus, while the niche and neutral processes existed simultaneously in habitats with low soil phosphorus availability. There was a significant scale effect on the species-abundance distribution pattern of Q. aliena var. acutiserrata forests in Taibai Mountain. The niche and neutral processes could protect the species-abundance distribution at the 20 m×20 m scale in PF, while the niche process could explain the species-abundance distribution at the 40 m×40 m and 70 m×70 m scales. The niche and neutral processes combined acted on the species abundance distribution at the 20 m×20 m, 40 m×40 m and 70 m×70 m scales in SF, with niche process being more important than neutral process. Moreover, besides the scale and habitat heterogeneity, the species-abundance distribution patterns of Q. aliena var. acutiserrata forests differed significantly between primary forest and secondary forest under anthropogenic disturbance.