海南甘什岭热带低地雨林不同演替阶段根系的生物量特征

热带地区植物根系生物量的研究对预测气候变化条件下土壤碳库的变化和热带雨林次生演替地下生态学过程的认识具有重要意义。在海南三亚市甘什岭自然保护区内，选取4个植被恢复阶段（草本群落、灌木群落、40 年次生林和60 年次生林），利用平均标准木机械布点法采集0～100 cm根系样品，研究根系生物量、不同根系径级组成结构以及地下垂直分布规律。研究结果表明:（1）甘什岭热带低地雨林不同演替阶段根系生物总量在5.23～28.98 t·hm?2，植被恢复演替（正向）显著地增加了根系生物量，其中草本至灌木阶段不显著；（2）木本植物群落根系生物量以粗根（>2 mm）为主，最高占其总生物量的89.76%，草本则以细根（≤2 mm）为主，占其总生物量的53.53%以上；随着甘什岭植被的恢复，粗根占根系生物量的比例逐渐增加，细根占根系生物量的比例逐渐减小。（3）甘什岭热带低地雨林近80%的根系生物量集中分布在 0～20 cm 土层中，随着土壤剖面深度的增加，根系生物量大幅度减少，草本群落生物量在土壤剖面中的垂直变化规律呈指数回归，其余各恢复演替阶段呈幂函数回归。（4）根系生物量模型中，树高、D2H（胸径的平方与树高的乘积）与根系生物量拟合最好，在实践应用中，可根据林木的树高和D2H估测甘什岭地区植被根系生物量。本研究结果为进一步研究甘什岭热带低地雨林植物群落地下碳素分配及土壤碳库变化奠定基础，还可为估算我国热带低地雨林地区植被根系生物量和生产力提供参考。

Characteristics of Root Biomass in the Tropical Lowland Rain Forest at Different Succession Stages in Ganshiling Natural Reserve,Hainan Island

Plant root biomass in tropical regions plays an important role in predicting the change of soil carbon pool under climate change and understanding the ecological process of secondary succession of tropical rain forest. Four vegetation communities at different restoration stages (herb community, shrub community, secondary forest with 40 years, secondary forest with 60 years) were selected in Ganshiling Natural Reserve, and their root samples in the soil 0～100 cm deep were collected by the average-tree-specific sampling method. The root biomass and the structure and vertical distribution of underground roots with different diameters were analyzed. The results show that the total root biomass of plants at different succession stages ranged from 5.23 t·hm?2 to 28.98 t·hm?2 in the tropical lowland rain forest in Ganshiling Natural Reserve, and that vegetation restoration succession (forward) significantly increased root biomass at various vegetation stages except the root biomass at the succession stage from the herb to shrub, which decreased and was not significantly different. The root biomass of the woody plant community consisted mainly of thick roots (>2 mm), which accounted for 89.76% of the total root biomass, whereas that of herbaceous plant community consisted mainly of fine root (≤2 mm), which accounted for 53.53% of the total root biomass. With the restoration of vegetation in Ganshiling Natural Reserve the proportion of the thick roots in root biomass gradually increased, while the proportion of the fine root in root biomass gradually decreased. About 80% of the root biomass in the tropical lowland rain forest was mainly produced in the soil layer between 0～20 cm. With the increase of the soil depth in the soil profile the root biomass decreased significantly. The root biomass in the herb community showed a vertical change with exponential regression in the soil profile, while the root biomass in the woody and shrub communities at the restoration succession stages had a vertical change with power function regression. The tree height and D2h were best fitted to the root biomass in the root biomass model, and the root biomass could be estimated according to the tree height and D2h in Ganshiling Natural Reserve. This study can provide a reference for estimating the root biomass and productivity of the tropical lowland rain forest in China, and it also lays a foundation for further study of carbon distribution and soil carbon pool change of the plant communities in the tropical lowland rain forest in Ganshiling.