封育草地根系功能性状演变及其对土壤碳蓄积的作用机制

Grassland degradation is a main problem that is threatening the sustainable development of grasslands and animal husbandry in our country. Grazing exclusion is an effective measure for restoring vegetation and increasing soil carbon accumulation of degraded grasslands. However, most of studies on the responses of vegetation to grazing exclusion have focused on plant community composition and structure, rather than that of roots. The comprehensive evaluation of vegetation restoration is an urgent question in current time. Songnen grasslands with different grazing exclusion ages will be selected as study areas in this project. The theories of functional ecology and restoration ecology will be employed. Both field survey and laboratory analysis will be conducted. The WinRHIZO root analysis system also will be used to determine variations of root functional traits. Furthermore, the indicating functions of root functional traits for grassland restoration will be clarified. According to the analytical hierarchy process, the root functional traits will be incorporated into the restoration evaluation. In addition, the relationship of root functional traits and soil carbon accumulation will be quantified basing on the data of soil samples analysis. Finally, the effect of root functional traits to root decomposition and turnover will be studied to reveal the mechanism of carbon accumulation. The work is benefit for the enrichment of restoration theories, and will provide a reliable reference for evaluating vegetation restoration and carbon cycle of regional grassland.

草地退化是我国天然草原面临的突出问题，严重威胁草牧业的可持续发展。围栏封育是恢复退化草地植被和增加土壤碳蓄积的重要措施之一。目前有关植物对封育响应的研究主要集中在群落组成和结构方面，对根系层面的关注相对不足。本项目针对草地植被恢复亟待全面评估的问题，以松嫩平原不同封育年限草地为研究对象，以功能生态学和恢复生态学的基本理论为指导，野外调查与室内分析相结合，借助WinRHIZO根系分析系统，研究封育草地植物根系功能性状随封育时间的演变规律。参考层次分析方法，明确根系功能性状对草地恢复进程的指示作用，并将根系功能性状纳入恢复效果评价。结合时间序列土壤样品数据，阐明根系功能性状与碳蓄积量之间的关系，找出关键的驱动性状。在此基础上，探讨根系功能性状对根系分解和周转的影响，揭示封育草地土壤碳蓄积量变化的根系作用机制。该项目的执行为强化草地生态系统恢复评价和预测区域碳循环趋势提供科学依据。

草地退化是我国天然草原面临的突出问题，严重威胁草牧业的可持续发展。围栏封育是恢复退化草地植被和增加土壤碳蓄积的重要措施之一。本项目以松嫩地区放牧和封育6年、11年、15年、23年草地为研究对象，在植被和土壤调查的基础上，测定了不同封育年限优势物种羊草和伴生植物的根系功能性状，找到了对封育措施响应敏感的性状和性状组合。结合草地土壤碳蓄积量的变化特征，探索了根系功能性状变化对土壤碳蓄积的作用机制。研究结果表明：1）随着封育时间的延长，草地植物群落形成一年生群落—杂草群落—羊草群落的演替序列，盖度和高度逐渐增加，物种数和多样性先降低后升高；2）草地封育降低了pH和电导率和提升了养分含量增加；3）羊草根重、根长、根表面积和碳磷比随封育年限延长而呈线性增加趋势，比根表面积和碳含量逐渐降低；4）封育措施促进羊草根表面积和比根体积的种内变异程度远大于群落内种间变异程度；5）放牧干扰导致比根长、比根表面积和比根体积的群落加权平均值保持较高水平，表征了群落对地下水分和资源较高的获取能力；根重、根长、根表面积、根体积和根直径的群落加权平均值与草地生物量显著正相关，封育15年达到最高，而封育23年有所降低；6）草地长时间封育并不利于根系的生长，封育23年草地根系生产量和周转率均较低；7）根系周转与群落平均根长、根重、根表面积以及优势物种根直径和碳磷比显著负相关；8）羊草根组织密度、碳磷比、碳氮比、比根表面积和磷含量决定了土壤碳蓄积量。综上所述，封育草地优势物种羊草的根系功能性状和群落平均性状共同影响土壤碳蓄积过程。本项目研究了封育草地根系功能性状演变特征及其对土壤碳蓄积的作用机制，对分析和评价草地生态系统恢复进程和预测区域碳循环过程具有重要科学意义。