南亚热带退化草坡上先锋灌木与移栽乔木之间种间关系随时空因素的变化规律及机理

Results from NSFC-Young Scientists Fund (NO. 30901148) showed that the shrub resource island on south subtropical degraded shrubland accumulated soil nutrients, soil water, as well as buffered solar radiation and air temperature which are key factors for tree seedling establishments. However, the relationships between the shrub (Rhodomyrtus tomentosa) and tree seedlings are changed along with plant developments and soil environments, which need further investigations. The study achieved a series of academic progresses including 2 published SCI papers, 2 accepted SCI papers, and 1 SCI paper in revision. . Based on the NSFC-Young Scientists Fund, the current project is aiming to investigate the changes in interactions between the dominant shrub (Rhodomyrtus tomentosa) and its underneath regional tree seedlings (or saplings) by spatio-temporal factors in south subtropical degraded lands. In combinations with the primary findings (year 1 to year 3) based on shrub-tree seedlings (or saplings), this research is going to extend the study to a longer period (4 to 7 years) in order to further analyze changes in plant interactions along with time (plant development). Meanwhile, this research will find out the effects of the spatial factor (soil environment gradient) on interactions of shrub-tree seedlings. This study attempts to further understand the pioneer shrub and transplanted tree species interactions regulated by spatio-temporal factors and its mechanisms in south subtropical degraded shruland. The current project will improve the theories of plant interaction study and instruct forest restoration in south subtropical region.

青年科学基金（30901148）的研究发现，南亚热带退化草坡灌木资源岛的土壤及光温条件是有利于乡土乔木幼苗成功定居的关键因子，但资源岛构建植物桃金娘与乔木幼苗种间关系会随个体发育和土壤环境而改变，有必要跟踪研究。项目取得了一系列学术进展，正式发表SCI论文2篇，接收SCI论文2篇，修回SCI论文1篇。.本项目在青年科学基金的基础上，分析时间和空间因素如何影响南亚热带退化草坡上优势先锋灌木与移栽在其冠幅下的乔木幼苗/幼树之间的种间关系。在已开展的桃金娘与乔木幼苗/幼树种间关系研究工作（1-3年）基础上，将研究时间扩展到4-7年，跟踪观测二者的种间关系随时间因素（个体发育）的发展方向。同时，分析空间因素（土壤环境梯度）对桃金娘和移栽乔木幼苗种间关系的影响。研究试图深入理解南亚热带退化草坡上先锋灌木与移栽乔木的种间关系随时空因素的变化规律及机理。本项目将完善植物种间关系理论，指导森林恢复。

南亚热带退化草坡先锋灌木桃金娘有效聚集的土壤养分和水分，缓解的太阳辐射和气温是促进乔木幼苗成功定居和森林植被恢复的关键因子。然而，受时间和空间因素的影响，桃金娘与乔木幼苗的种间关系存在着不确定性，有待于进一步揭示。为此，本项目在调查了南亚热带典型退化草坡环境因子及植物群落特征的基础上，分析了先锋灌木与移栽乔木种间关系随时间因素（个体发育等）和空间因素（环境梯度等）的变化机理。研究发现（1）荷木幼苗的存活率主要受土壤养分和土壤酸度的影响，而其生长则更多受到桃金娘冠幅遮阴的影响。这一结果部分支持了判定植物种间关系的经典理论——胁迫梯度假说。（2）桃金娘对乔木幼苗定居和生长的影响主要取决于土壤养分和水分的可获取性、对夏季强光胁迫的减弱程度以及乔木幼苗的特定需求等。（3）桃金娘冠幅下的湿地松需要更长的偿还时间以构建所需的碳化合物，但桃金娘冠幅下的荷木则需要更短的时间构建所需的碳化合物。因此，荷木具有取代桃金娘群落，加速南亚热带退化草坡向地带性森林恢复的潜力。（4）桃金娘冠幅下松树生长受到抑制的主要原因是桃金娘遮阴引起松树叶肉细胞类囊体的膨胀、叶绿素含量的降低和光合系统II电子传递速率的下降。基于上述研究结果，我们提出在利用先锋灌木桃金娘进行南亚热带退化草坡植被恢复时，需要慎重考虑环境因素的影响，了解环境中的植物定居限制因子（如土壤养分、光照和水分等），分析备选乔木植物的主要生物学特性。同时，长期观测和大量的树种筛选对退化生态系统的植被恢复工作尤为重要。研究对指导南亚热带地区森林恢复具有重要的科学意义，对世界各地的植被恢复实践具有重要的参考价值。本项目的前期研究还推动了乡土植物的推广应用，产生了良好的社会经济效益。