根系及其主要影响因子在森林演替过程中的变化

统计分析了国内外主要森林生态系统演替过程中根系生物量及其分布的变化，并探讨了相关的影响因子及其动态。结果发现，根系生物量随林龄和演替的进行而增加，演替群落的根冠比呈减小趋势。一般来说，根系的垂直分布是较浅的，尤其是细根。根系分布范围与地下部生态位的变化能够反映其可以利用的资源范围以及它在演替过程中的作用和地位。在森林演替初期，群落根系分布较浅，可塑性强，且水平根系发达；演替中期的根系呈镶嵌分布，分布范围加深，根系密度增加；演替后期的根系分布趋于稳定，地下生态位分离程度加剧，根系结构具有相对明显的分层。在演替过程中，根系的这种分布特征受自身条件和生态因子的影响，文章论证了这些影响因子本身在演替过程中也是动态变化的，进一步说明了根系分布动态规律存在的必然性。在演替过程中，根系生物量及其分布动态的研究，可以为森林群落动态学提供新的理论基础，是未来地下生态学研究的焦点之一。最后，分析了根系研究中亟待解决的问题和今后的发展重点，提出新的展望。

Variation of roots and its impact factors in succession

As substantial components in the ecosystem, roots play important roles in protecting the soil against erosion and in supplying the aboveground plant parts with water and nutrients root, also in regulating nutrient and carbon cycles in succession. In this article, we analyzed variation of forest roots and its distribution in succession, and discussed the concerned impact factors and the dynamic of them. We found that roots biomass increased but the ratio of root to shoot decrease with successional stage extend. Distribution of roots would reflect the area where they can absorb resources and the function and the status in succession. In early stage of succession, roots distribute shallowly with strong morphological plasticity, and horizontal roots were numerous. In middle stage of succession, more and more roots distributed deepened and inlaid, and roots density increased. In late stage of succession, roots have obvious layered structure with underground niche separation. These characters of forest root distribution were affected by both the intrinsic factors and ecological factors, so we also analyzed the dynamic of these factors in succession. Further more, the research of root biomass and its distribution in succession can provide the new theoretic bases for forest dynamics, also maybe the one focus of the belowground ecology. At last, we provide several suggestions to boost the root research in succession.