洞庭湖青山垸退耕地不同水位土壤种子库特征

Characteristics of soil seed banks in different water level areas after returning farmland into lake in Qingshanyuan of Dongting Lake

研究退耕地土壤种子库的组成特点和分布规律是评价受损湿地生态恢复效应的重要组成部分.本文以洞庭湖典型退田还湖区——青山垸为对象,研究了不同水位及湿地土壤(0～2、2～5和5～10cm)种子库的大小、物种组成多样性及其与地上植被的关系.结果表明:青山垸土壤种子库密度、丰富度指数以及地上植被与土壤种子库的相似性系数沿低-中-高水位梯度呈"V"型变化.常淹区种子库密度最高,为(36943±5207)粒·m-2,偶淹区最低,为(18618±6977)粒·m-2,洪淹区居中,为(30572±5329)粒·m-2;地上植被与土壤种子库的相似性系数(Sorensen系数)为常淹区(0.76)>洪淹区(0.53)>偶淹区(0.41).种子库密度、物种多样性指数和物种丰富度指数沿土壤剖面呈递减趋势,但不同水位的递减幅度存在差异.种子库密度、物种丰富度以及地上植被与湿地种子库的相似性系数沿水位梯度呈规律性变化,与其所处的地理位置水文波动和植被的物种生活型组成等密切相关.

To study the composition and distribution of soil seed bank in the areas after returning farmland into lake is of significance in evaluating the ecological restoration effect of damaged wetlands. In this paper, the composition and diversity of seed bank in soil profile （0-2, 2-5, and 5-10 cm） and their relationships with above-ground vegetation in different water level areas in Qingshanyuan, a typical region after returning farmland into lake in Dongting Lake, were investigated. A V- type variation pattern was observed in the seed density and species richness of soil seed bank and in the similarity coefficient of soil seed bank and above-ground vegetation along a gradient of low- medium-high water level. As for the seed density, it was the highest （36943 ± 5207 seeds · m^-2） in frequently flooded area, followed by in heavily flooded area （30572 ± 5329 seeds · m^-2）, and in incidentally flooded area （18618 ±6977 seeds · m^-2） ; for the similarity coefficient, it was also in the order of frequently flooded area （0. 76） 〉 heavily flooded area （0. 53 ） 〉 incidentally flooded area （0. 41 ）. The seed density, species diversity, and species richness of soil seed bank decreased along soil profile, but the decrements differed in different water level areas. The regular variation patterns of the seed density and species richness of soil seed bank and of the similarity coefficient of soil seed bank and above-ground vegetation along the water level gradient were closely related to the water-level fluctuation and the life-form composition of the vegetations in study area.