To investigate the characteristics of plant diversity in the understory of eucalyptus plantations in Hainan, vegetation surveys were conducted in different areas of eucalyptus plantations, and the biomass of the upper part of the interior of the sample plots was measured by combining the standard wood method and the harvesting method, then theα-diversity index of the irrigation and grass layers was combined with the biomass of the above-ground part to construct a comprehensive functional index, and the new index was compared with the α diversity index. There were 101 species of understory plants in eucalyptus plantation, among which 49 species appeared in shrub layer, belonging to 45 genera of 31 families, and 52 species appeared in herb layer, belonging to 48 genera of 28 families. There was no significant difference in the diversity index of understory shrub layer in different regions of eucalyptus plantations. The α diversity index of herbaceous layer in Lingao was significantly higher than that of other areas. It means the diversity level of shrub layer was similar, while the diversity level of herb layer was more affected by environment. There were significant differences in aboveground biomass allocation between shrub layer and grass layer in different regions. Although shrub layer was larger than herb layer, the distribution ratio fluctuated widely. Yd indices of shrub layer of eucalyptus plantations in different areas had no significant difference, and Yd indices of herb layer in Lingao and Ding'an were significantly higher than those in Tunchang and Dongfang. It means that the ecological functions of shrub layer in different areas were similar, while the ecological functions of herbaceous layer were obviously stronger than those of Lingao and Ding'an. The Yd index of the shrub layer was strongly correlated with the α-diversity index; the Yd index of the herb layer was generally correlated with the α diversity index and strongly correlated with above-ground biomass. The results show that the plant diversity characteristics of the eucalyptus understory are influenced by the regional environment, with the herbaceous layer being more susceptible than the shrub layer; the α-diversity index of the shrub layer has a greater influence on the Yd index, while the above-ground biomass of the herbaceous layer has a greater influence on the Yd index. The Yd index can reflect both the α-diversity level and biomass of the understory, and is a good complement to evaluate the ecological functions of the understory vegetation of eucalyptus plantations.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |