荒漠环境梯度下红砂-珍珠混生群落种间根系相互作用关系的研究

The research and argument is very active which is about the relative change of interspecific positive and negative interactions along with environmental gradient, but from the root to knowing the response regularity and driving mechanism of interaction type and interaction strength in plants along with environmental stress, remain to be revealed. Reaumuria soongorica and Salsola passerina are typical desert shrubs and they often mutually assembled for a mixed community, they widely distribute in the eastern desert of China and desert steppe, and the significant gradient of light-temperature-humidity and various water and heat combination is formed from the east to west in the distributed regions, thus the distributed pattern from desert steppe, typical desert to extremely desert along with desert environmental gradient is formed in China, and they have prominent resources advantages and ecological advantages. In this study, we used the mixed community of Reaumuria soongorica and Salsola passerina as a research subject, the change characteristics of spatial distribution and morphology of root in mixed community along with desert environmental gradient is ascertained, the differentiation regulation of root ecological niche in mixed community along with desert environmental gradient is illuminated, the law and driving mechanism of interspecific interaction of root in mixed community responding to desert environmental gradient is revealed and the stress gradient hypothesis is tested. It has important academic values for understanding the transition from negative interaction to positive interaction of plant under stress environments and improving this theory, and has important guiding for the restoration of vegetation under stress environments; it also provides more theory for knowing species coexistence mechanism from root.

植物种间正负相互作用沿环境梯度相对变化的研究和争论十分活跃，但从根系入手来认识植物种间互作类型和互作强度随环境胁迫的响应规律及驱动机理，有待揭示。红砂和珍珠为典型荒漠灌木，两者常互为共建种组成混生群落，广布我国荒漠东部和荒漠草原区，其分布区气候由东向西形成光-温-湿的明显梯度和多种多样的水热组合,在我国形成了沿荒漠环境梯度从荒漠草原区、典型荒漠区、到极端荒漠区的分布格局，具有突出的资源优势和生态优势。本项目以红砂-珍珠混生群落为研究对象，查明不同荒漠环境梯度下混生群落根系空间分布和形态结特征，阐明混生群落根系生态位沿荒漠环境梯度分化的规律，揭示混生群落种间根系相互作用响应荒漠环境梯度的规律和驱动机理，验证胁迫梯度假说。对深化理解环境胁迫驱动的植物相互作用负/正的转变和完善该理论有重要学术价值，对胁迫环境下植被的恢复有重要指导意义，也为从地下根系入手来认识物种共存机制提供更为丰富的理论支撑。

从根系入手来认识植物种间互作类型和互作强度随环境胁迫的响应规律及驱动机理有待揭示。项目以红砂与珍珠混生群落为研究对象，测定了荒漠环境梯度下混生红砂与珍珠光合、荧光、根系分布、形态与构型指标；同时采取人工模拟降水和根系分隔实验，测定了不同降水和根系分隔方式下红砂和珍珠混生幼苗地上、地下形态指标。遵照项目任务书的研究内容和任务，已经完成了预期目标，取得了主要成果如下：1）混生促进了红砂和珍珠比根长和比表面积增加，根系相互作用关系表现为互惠。不同荒漠生境条件下红砂与珍珠占据不同生态位，且随荒漠环境胁迫增强混生红砂与珍珠根系生态位分离越明显，验证了环境胁迫梯度假说。“地上聚生，地下分离”的混生方式是红砂和珍珠混生群落适应干旱胁迫环境的生长策略。2）与单生相比，混生红砂光合能力增强，对光能有高效的捕捉能力，可通过种间互惠更好地利用养分资源适应种间竞争及干旱胁迫环境；混生珍珠竞争作用加强，更多的选择以热量的方式散失光能。荒漠环境梯度下红砂通过维持较高净光合速率、较高蒸腾速率和低水分利用效率来生存，属于避旱型；而珍珠则通过高水分利用效率来更好的生存于水资源不太丰富的荒漠，属于耐旱型。3）荒漠环境胁迫梯度下红砂和珍珠均表现为碳素积累、氮磷素限制的格局，它们对于氮和磷的养分利用不活跃，受到氮和磷养分的限制较为均衡。4）不同降水条件下红砂和珍珠混生幼苗因地下根系竞争激烈，生长受到抑制。红砂幼苗更多将生物量分配给茎以适应叶片休眠和地上竞争，而珍珠幼苗将更多生物量分配给叶，以进行光合作用适应干旱及种间竞争。不同降水梯度下混生更有利于珍珠幼苗塑造良好的根系形态，且主要通过调整幼苗细根根系形态来适应水分变化。5）不同根系分隔方式下红砂和珍珠混生幼苗根系表现出了一定的互补，但并没有发生明显的根系生态分离现象。6）发表论文25篇，其中SCI 3篇，培养博士研究生1名，硕士研究生4名，项目主持人晋升教授。