基于细根形态结构和生理功能探讨栓皮栎萌蘖力衰退机理

Resprouting in woody plants is an important mechanism that allows plants to regenerate after the elimination of the aboveground biomass in natural secondary forest and plantations. The stumps with none resprouting, weak resprouting or high post-resprouting mortality are observed in multiple generation coppice forests. Roots are considered as the complete remain parts after the disturbance. Fine roots play a vital function on the bud and growth of sprouts because of their vitality. The decline of resprouting ability of Quercus variabilis has limited the regeneration of secondary forest and decreased the earning of oak planters. To detect fine roots structure and physiological characteristics associated with the ability to resprout, the typical secondary forests of Q. variabilis were selected based on our previous works. Through the field investigation in the next three years, the growth and morphological characteristics of fine roots were monitored with minirhizotron methods, the anatomical structures were observed with paraffin sections methods, and the nutrient contents and roots vigor were analyzed with biochemical methods. The diversity of fine roots in stumps with different resprouting ability was compared. After simulating stem cutting in nursery, three types of plant hormone were posited in apical roots with immuno-colloidal gold technology during the sprouting process. The relationship between fine roots growth and shoots photosynthesis was analyzed. The main reason limiting the overall resprouting success were explained by fine roots, which provide a new train of thought for the research of resprouting mechanism in woody plants. The results take an important scientific significance on sustainable forest regeneration and a practical significance on the theory for Q. variabilis coppice management and secondary forests rejuvenation.

木本植物的萌蘖再生是天然次生林恢复和人工林经营的重要方式。多代萌生个体常表现出无萌芽、萌蘖苗生长孱弱和枯死等衰退现象。根系是干扰后保留的完整器官，细根是根系最活跃的部分，对萌蘖苗生长起关键作用。栓皮栎萌蘖力衰退已造成林地更新困难、种植户经济损失。为探明栓皮栎细根的形态和生理与萌蘖力衰退之间的关系。在前期工作基础上，本课题选择典型栓皮栎次生林，拟连续三年野外调查，应用微根管原位监测技术记录细根形态、石蜡切片技术观察解剖结构、常规生化实验测定营养物质和根系活力，比较不同萌蘖力伐桩的细根差异；在苗圃模拟茎干采伐，应用免疫胶体金技术定位分析不同萌蘖阶段根尖植物激素分布；分析细根生长与光合作用强度的联系。从细根角度解释栓皮栎萌蘖力衰退的原因，为木本植物萌蘖机制的研究提供新思路，对维持森林可持续更新具有重要科学意义；为栓皮栎矮林经营和次生林复壮技术研究提供理论支撑，具有重要实践意义。

在天然次生林恢复与人工林经营中，萌蘖再生是一种重要的更新方式。细根是林地采伐后保留的根系中最活跃的部分，对萌蘖苗生长起关键作用。为阐明细根与萌蘖更新的关系，采用控制实验和野外调查相结合的方法，探究细根形态和生理对地上光合水平的响应。结果发现：采用主成分法将栓皮栎细根根据功能划分为2 mm以下的吸收根群和2 mm以上的运输根群；在华北地区，与蒙古栎和槲栎相比，栓皮栎根系水分疏导效率高而抗栓塞能力较弱，抗旱性差；去除地上部分后，栓皮栎细根在30 d内表现出可溶性糖、淀粉含量下降，碳含量变化不显著，氮含量增加，碳氮比降低，而木质素和纤维素含量增加，不同激素含量先后在12—36 h达到最低，随后吲哚丁酸和赤霉素代偿性增加；萌蘖苗的生长后的7 d细根中保护酶的清除和渗透调节作用达到最大；栓皮栎采伐后的前3年萌蘖苗生长较快，3月、9月的降雨和8月适宜温度能够促进萌蘖苗生长；由于缺少有效光辐射，1年生栓皮栎萌蘖苗光合能力较低，光补偿点和饱和点均低于多年恢复植株；与长期恢复林分（40年）相比，短期恢复林分（8年）的根系可溶性糖和淀粉含量均降低、二者比值下降，碳浓度降低、氮浓度升高、碳氮比显著较低，说明根系死亡率增加、周转加快；分析认为栓皮栎次生林恢复期越短，林冠盖度越低，光合水平下降、土壤干热化是造成细根死亡的外部因素。针对这一问题，项目组提出开沟埋青、疏松土壤、增施氮磷肥、覆草保墒等以提高根系质量为目标的次生林经营技术。通过项目的实施，基本探明地上部分干扰对栓皮栎细根生长、内含物以及相关生理的影响，深入分析了不同萌蘖恢复期的根系碳氮和激素代谢的特点，丰富了细根相关的理论研究，对揭示根系在林地恢复和经营中的作用具有重大意义，为今后次生林健康评价和更新恢复提供了重要参考依据。依托本项目发表论文3篇，其中2篇核心期刊；SCI收录期刊在审一篇，在写一篇；申请专利2项；编纂科普读物1部；获人才称号1项，培养研究生2名。