元江流域干热河谷灌草丛土壤种子库与地上植物群落的物种组成比较

Comparisons of species composition between soil seed banks and aboveground plant communities in the dry-hot valley of the Yuanjiang River

土壤种子库与地上植被之间的关系和相似性是长期争议的群落生态学问题之一。本研究旨在通过比较元江流域干热河谷典型灌草丛群落与其土壤种子库的物种组成,探讨土壤种子库与地上植物群落存在怎样的相似性关系。在元江干热河谷上、中、下游选取典型灌草丛群落,采用典型样地调查法进行植物群落调查,同时在样方内采集0–5 cm、5–10 cm、10–15 cm三层土壤样品,采用萌发实验研究土壤种子库的种子数量和物种组成,并与地上植物群落进行比较。结果表明:(1)全部调查样方的地上植被中共包含种子植物76种,隶属于25科64属,主要集中在豆科、禾本科、菊科、大戟科,群落物种组成以多年生草本为主、灌木为辅;(2)土壤种子库中共发现33种植物,隶属于14科32属,以旱生型禾本科、豆科、菊科物种为主;(3)土壤种子库中的植物种子密度在表层土壤中最高,随着土层的加深而递减;(4)各样方的土壤种子库与地上群落共有物种数较少,相似性较低;土壤种子库密度与地上群落的种群密度没有显著的相关性。总体而言,本研究发现元江流域干热河谷典型灌草丛群落其土壤种子库与地上群落之间没有显著的相关性,并且地上群落和土壤种子库都有外来入侵种类。

The relationship between the seed bank and aboveground communities has attracted much interest among plant community ecologists. The objective of this study was to address the relationships between soil seed banks and aboveground plant communities by comparing the species composition in the dry-hot valley of the Yuanjiang River. Typical shrub-grass communities in the dry-hot valley were selected and five plots were established in upper, middle, and lower sections of the Yuanjiang River watershed. A total of 100 sampling quadrats were collected, and plant communities were surveyed. In addition, soil samples were collected in three layers（0–5 cm, 5–10 cm, and 10–15 cm） in each community sample. The seed banks from the soil samples were germinated in the lab and species were identified. The results showed that（1） 76 plant species belonging to 25 families and 64 genera were found in the aboveground plant communities. These species mainly belonged to Fabaceae, Poaceae, Asteraece and Euphorbiaceae.（2） 33 plant species belonging to 14 families and 32 genera were found in the soil seed banks. These species mainly belonged to xeromorphy Gramineae.（3） In three soil layers, the proportion of the surface soil seed banks was the largest, and the numbers of seeds decreased as the depth of soil increased.（4） For each plot, few common species were found between the soil seed banks and plant communities, and thus their similarity is low. In summary, there were no significant correlations between the soil seed banks and aboveground plant communities. Moreover, several invasive species can be found both in the seed banks and aboveground plant communities.