太白山土壤种子库储量与物种多样性的垂直格局

通过野外植被调查和室内试验，从1 220份土样中，挑选土壤中的种子，进行分类统计，研究秦岭太白山南坡土壤种子库储量与物种多样性沿海拔梯度的变化。研究结果如下：(1) 太白山南坡土壤种子库中的植物种为172种；从总体上看，土壤种子库中的物种丰富度 (S) 随着海拔的上升呈下降趋势。土壤种子库生物多样性特征表现为在2个海拔段发生较明显的变化：一是从低海拔到中等海拔 (1 500~2 500 m)，二是从中等海拔到高海拔 (2 500~3 500 m)。在?琢多样性方面，生态优势度在海拔2 500 m处最大；在海拔2 400 m以下 (包含2 400 m) 的样地中，种子库生态优势度大于海拔2 500 m以上 (含2 500 m) 的样地种子库的生态优势度。 H′(Shannon-Wiener指数)与生态优势度的变化趋势相反。(2) 太白山南坡土壤种子库储量最大值出现在海拔2 600 m的样地，为2.24×104 Ind./m²；种子库储量最小值出现在海拔3 500 m的样地，为4.43×102 Ind./m²。储量沿海拔梯度的变化趋势表现为：在海拔2 600 m以下，种子库储量沿海拔的上升呈逐渐增加的趋势；在海拔2 600 m以上，种子库储量沿海拔的上升呈逐渐下降的趋势。(3) 土壤种子库的种子储量与种子密度的变化规律基本一致。而用单位面积土壤中的种子储量来表示种子库的大小特征比用种子密度来表示更为实用和方便，而且采集具有不同性质的土壤研究种子库，考虑到了土壤性质等因素的影响，更能客观反映土壤种子库的特点。

Changes in Soil Seed Banks and Biodiversity along an Altitude Gradient in Taibai Mt.

Soil seed bank is the pool for species composition of a plant community. It plays a critical role in succession of the community and maintenance of the community structures and functions. In this paper, we studied the distribution of soil seed banks along an altitudinal gradient (1500-3500 m asl) on the southern slope of the Taibai Mountain. The main results are summarized as follows: (1) Reserves of the soil seed bank increased with an increase of elevation, reached its maximum at an altitude of about 2600 m, and then decreased with increasing altitude. Above the altitude of 2000 m, the distribution of seed reserves in the soil profile can be generally characterized by the fact that most of soil seeds occurred in litter-fall layer, and smallest reserves were in the subsurface soil layer. Below the altitude of 2000 m, most of soil seeds occurred in humus layer. (2) A total of 172 plant species from the soil seed banks were accounted in 21 plots. The number of species was reduced along an altitudinal gradient. The community characteristic of soil seed banks varied obviously in two altitudinal ranges, 1500-2500 m and 2500-3500 m. (3) The reserves and density of seed banks showed a similar pattern along the altitudinal gradient. It was better to use reserves to indicate the size of soil seed banks. In this study, the soil samples were divided into three layers: litter-fall layer, humus layer and subsurface soil layer.