喀斯特极度侵蚀区菌根真菌提高树木耐旱性机理研究

In extreme erosion karst area, surface soil is barren and discontinuity. Because this area exsiting ground-underground double layer hydrological structure, surface soil extremely easy to be dry, while drought stress becoming the key factor of restricting the tree growth and vegetation restoration. Inoculated mycorrhizal fungi can improve the drought resistance of plants, and enhance the survival rate of afforestation, but the improvement of drought resistance and the mechanism of mycorrhizal fungi on the trees in extreme erosion area in karst is not clear. This project will research the drought resistance mechanism of mycorrhizal fungi to improve the important four afforestation tree species such as Zenia insignis, Cipressus duclouxiana, Toona sinensis and camptotheca acuminata through greenhouse simulation, stable isotope tracer method combined with field investigation, clearify moisture transmission process of hyphal network between trees root-root, root-soil and their characteristics. This study will reveal the hyphae network impact on trees moisture absorption, transmission and utilization mechanism. Meanwhile, this project also analysed regulation and promotion of mycorrhizal fungi on plant photosynthesis, nutrient uptake, host endogenous hormone, osmotic substances, and the activity of antioxidant enzymes, demonstrated physiological action mechanisms of mycorrhizal fungi on karst drought tolerance of trees. Additionally, the project clearified the correlation of mycorrhizal network, soil microstructure formation, activation of phosphorus and root uptaking of nutrient. Popularization and application of mycorrhizal seedling afforestation in extreme erosion area of karst is also significant. The results of this study has important theory and realistic significance to the karst mountain area of vegetation restoration and ecological environment construction.

喀斯特极度侵蚀区土层瘠薄，土体不连续，存在地上、地下双层二元水文结构，表层土壤极易干旱，干旱胁迫成为制约树木生长和植被恢复的关键因素。接种菌根真菌能提高植物的耐旱性、提高造林成活率，但在喀斯特极度侵蚀区菌根真菌提高树木的耐旱性机理还不清楚。本项目通过室内模拟、稳定同位素示踪与野外调查相结合方法，研究菌根真菌提高任豆、滇柏、香椿、喜树等重要造林树种的耐旱机理，明确树木间根系-根系、根系-土壤间通过菌丝网络水分传输的过程、特征，揭示菌丝网络对树木水分吸收、传输、利用的影响机制；分析菌根真菌对宿主植物光合作用、养分吸收、内源激素、渗透物质和抗氧化酶活性的调节和促进作用，阐明菌根真菌对喀斯特树木耐旱性作用的生理机制；明确菌根网络与土壤微结构形成、磷的活化和根系养分吸收的的相关关系；在喀斯特极度侵蚀区推广应用菌根化苗木造林。研究结果对于喀斯特山区的植被恢复与生态环境建设具有重要的理论和现实意义。

喀斯特极度侵蚀区土层瘠薄，土体不连续，存在地上、地下双层二元水文结构，表层土壤极易干旱，干旱胁迫成为制约树木生长和植被恢复的关键因素。接种菌根真菌能提高植物的耐旱性、提高造林成活率，但在喀斯特极度侵蚀区菌根真菌提高树木的耐旱性机理还不清楚。本项目通过野外调查、室内模拟和稳定同位素示踪相结合方法，筛选出耐旱性优势菌根真菌菌种，研究菌根真菌提高造林树种的耐旱机理。.（1）野外调查表明菌根真菌可以侵染大部分野生植被，形成良好的共生关系；菌根真菌菌种资源丰富，球囊霉属是喀斯特地区优势属；土壤磷含量是影响树木菌根侵染的最主要因素，土壤碳含量和pH是影响菌根真菌多样性最主要的因子。.（2）茶条木、降香黄檀、香椿、喜树和任豆等菌根苗木成活率、生物量、苗高、基径比未接菌处理显著增高，5个树种中，香椿苗木菌根依赖性最高，任豆苗木最低，菌根苗在石漠化生境下的成活率和生长速度高于非菌根苗。接种G. mosseae（Gm）、G. intraradices和P. tinctorius和混合接种均能有效侵染青冈栎幼苗根系，形成菌根共生体；在干旱胁迫下，青冈栎对菌根真菌的依赖性较高；.（3）接种处理均能显著促进青冈栎总氮、总磷和总钾的含量改善体内营养状况；接种菌根真菌使青冈栎体内提高可溶性糖含量，提高渗透吸水能力；提高超氧化物歧化酶、过氧化物酶和过氧化氢酶活性，有利于清除活性氧和过氧化氢；.（4）接种处理能提高土壤碱解氮、速效磷、有机质、土壤微生物量碳和水稳性团聚体含量，增强土壤脲酶和酸性磷酸酶活性，其中，菌根网络对土壤矿质元素有效性和营养元素活化主要作用于低养分含量的氮、磷、钾，较高含量的钙、镁活化作用不明显。菌根真菌对青冈栎的水分利用效率具有促进作用，Gm促进效果最明显。同位素示踪结果表明，干旱期间，青冈栎根系具有水分提升和水分再分配功能，相邻青冈栎之间能够通过菌根网络传输水分。根据混合线性模型公式估算，干旱期间，受体室青冈栎体内水分有1.66%的比例是通过菌根网络吸收。.