青藏高原黑土滩人工草地植物群落分层-分异演替机制及适应性调控

Through the study activities of former 4 projects supported by National Natural Science Foundation (NSFC), the applicant (Dr. Zhanhuan Shang) has more than 10 years academic experience of the subject of ‘bare-land’ degraded grassland on Tibetan plateau. During the long-term field monitoring of ‘bare-land sown grassland’ (>10 years) by the research team, we found out the plant community succession had the special phenomenon that is synusia stratification and successional differentiation with top layer and lower-layer of grassland community. Then we called this new scientific question as the ‘synusia stratification- succession differentiation’. Its ecological driving mechanism is key to deeply understand the long term ecological theory of ‘bare-land sown grassland’ sustainable management and adaptive regulation. Definitely, this new potential project is key base for the bare-land degraded grassland’s ecological restoration on Tibetan plateau. Then in this proposal, we designed four years field and laboratory work in the series of years ‘bare-land sown grassland’ plots (>10 years) with different successional stages to conduct the following ecological mechanisms. They are, (1) the mechanism of plant-regeneration bank’s different contribution to the above-ground vegetation’s succession by different plant group (such as grasses, forbs and sedge etc.); (2) interacting function of soil nutrition between soil microorganism and its effect on the above community and root system’s change; (3) different utilization efficiency of nutrition by different living type and function groups of plants species, that will cause the different response of above community to the soil nutrition form and content during the grassland succession; (4) allelopathy mechanism of among plants and plant-soil- microorganism, especially for the effect of herbs on forbs, and poisonous-weed forbs’ on grasses through the release of biological volatile organic chemicals (BVOCs). Based above the research of ecological mechanism, we also will do the model synthesize about the convergence succession of top and lower layers of the community with the years elapse and make sure the key parameters, such as the time, community, and soil etc. Meanwhile, we will combine the background information of study plots’ building methods, cost to analysis the low-cost model for the sustainable regulation of the sown grassland restoration with long time. This ecological experiment proposal will be conducted by long-term field and controlling method, then it will product the excellent study result ad outcome as international level, and it has cogent practical guidance function for the ‘bare land degraded grassland’ restoration about more than 70 million Chinese Mu and national ecological building engineering on Tibetan plateau

黑土滩人工草地植物群落的分层-分异演替是黑土滩人工草地长期演变的特殊现象，其生态学机制和适应性调控是青藏高原黑土滩退化草地有效治理的重要科学基础。拟通过课题组已经建立的中长期黑土滩人工草地样地（>10年）的连续定位实验，以及对不同年限、演替阶段黑土滩人工草地样地调查，研究驱动黑土滩人工草地分层-分异演替的（1）植被繁殖体库更新机制，（2）土壤养分-微生物互作机制，（3）植物养分利用效率差异性机制，（4）植物化感作用机制等主要生态学机制。通过分析黑土滩人工草地群落上、下层实现趋同恢复性演替的时间模型，群落、土壤调控因素调控模型；结合黑土滩人工草地建植、管理技术背景信息，研究黑土滩人工草地实现恢复性演替的低成本、可持续的调控技术模式。该课题基于长期恢复生态学控制实验，不仅在高寒草地生态学领域能产生高水平科研成果，并能切实指导青藏高原7000多万亩黑土滩退化草地效治理和生态建设工程。

项目通过定位控制实验和调查研究，对不同建植年限黑土滩人工草群落结构，土壤特征，以及生态功能等方面进行了系统分析，重点对对黑土滩人工草地从建植初期，中期，长期的群落分层现象下，生态系统功能变化特征和机制进行的解析，为深入理解黑土滩人工草地变化和可持续管理提供了参考。课题主要得到以下结论和成果：.（1）长期围栏封育降低了短暂种子库与地上植被的相似性，但增加了持久种子库与地上植被的相似性。土壤种子库对黑土滩人工草地地上植被更新的贡献较低，短暂种子库对植被更新的贡献高于持久种子库。.（2）黑土滩人工草地植物群落垂直层次的上、下两层片植物群落组成、结构和变化速率均呈现出异质性现象。长期人工恢复造成了植物群落多样性显著下降（分别降低了物种丰富度Richness、α-diversity、β-diversity的40%、37%和68%）、尤其是草地群落垂直下片层的生物多样性。.（3）土壤细菌丰度和α-diversity指数，随着恢复年限增长显著下降。长期人工恢复过程土壤系统碳库稳定性增强，有机碳的固持速率逐渐变慢；经过10年以上的人工恢复，草地系统总碳库恢复到了未退化高寒草地总碳储量的60%。.（4）不同形态氮素添加处理对禾草植株氮含量和非豆科杂类草植株碳含量具有显著影响（P < 0.05）。土壤真菌、细菌群落组成随黄帚橐吾密度变化而显著变化。.（5）草地排放的挥发性化合物以异戊二烯和单萜类化合物为主。非毒草植物群落（高山嵩草和垂穗披碱草群落）的挥发性化合物种类显著少于毒草植物群落。黄帚橐吾、冷蒿、夏河紫菀叶片和根系中萜类化合物的种类和相对含量均显著高于高山嵩草和垂穗披碱草。.（6）黑土滩草地人工恢复过程中，地上植被优先恢复，土壤有机碳库滞后恢复；土壤微生物多样性相对于植物群落具有较强的恢复力。黑土滩人工草地恢复的8-10年左右是关键期，应加强再次恢复调控，阻止生物多样性的锐减、加速土壤碳库固持。.（7）该课题共发表相关论文20篇，专著1部；授权国家发明专利1件，获批咨询报告1份。参加5次国内外学术会议，毕业硕士研究生3名，博士研究生2名。课题结果为青藏高原1.65亿亩“黑土滩”的人工生态恢复、有效治理提供科学依据。