黑松和刺槐混交对生产力及其时间稳定性的影响机理研究

Forests are increasingly exposed to climate-driven biotic and abiotic disturbances. Mixed-species forests are considered as one of the main options for adapting to and reducing risks of climate change. Both theory and evidence suggest that species mixtures enhance the productivity and its temporal stability in forests. However, the effect of species mixing on the productivity and its temporal stability, and the relative importance of the associated mechanisms, e.g. niche complementarity, inter-specific interaction or asynchrony, remain poorly understood in forests. Moreover, the mixing effect on productivity and its temporal stability depends on species compositions and varies from community, population to individual tree level. Therefore, the trade-off among the underlying mechanisms on these levels needs further understanding. This project will study what is the species mixing effect of Japanese black pine (Pinus thunbergii Parl.) and black locust (Robinia pseudoacacia L.) on the productivity (basal area increment), its temporal stability and their patterns at the community, population and individual tree levels in the Laoshan Mountain, Qingdao. This will be done by coring tree-ring in the two-species mixed forest plantations and their corresponding monocultures in a triplet design to explore the effect of species differences in crown architecture, shade tolerance and leaf phenology on species interactions. Furthermore, inter-specific competition or inter-specific facilitation caused by the annual growing conditions will be analysed. Finally, the differences and linkages of mechanisms of species mixing effects on productivity and its temporal stability will be revealed. This will help us deeply understand the effect of the mixture of Japanese black pine and black locust on the productivity and its temporal stability and provide a theoretical basis for sustainable forest management.

森林日益受到气候驱动的生物和非生物干扰的影响。混交林被认为是适应和降低气候变化风险的主要选择之一。尽管经验和理论研究表明混交林比纯林可能具有更高的生产力及其时间稳定性，并将这种现象归因于生态位互补、树种间相互作用或树种对生长条件的异步性等，但影响机理因树种组成及其在不同组织水平上的差异有待进一步深入研究。本项目以青岛崂山为研究地点，以黑松-刺槐人工混交林及其对应黑松人工纯林和刺槐人工纯林为研究对象，通过钻取生长芯的方法，在不同组织水平（群落、种群和个体水平）上量化对比生产力（以胸高断面积的增量为单位）及其时间稳定性的格局，探讨组成树种因树冠结构、耐荫性、叶物候期等差异对树种间相互作用的影响。此外，探索种间竞争或种间促进随年生长条件的变化规律，阐明树种混交对生产力及其时间稳定性的作用机制的区别与联系，揭示在不同组织水平间影响机理的权衡，为黑松-刺槐人工混交林可持续经营提供理论依据。

大量经验与模拟研究表明树种多样性可能提高森林生态功能水平，包括生产力、稳定性等，混交林被认为是适应和降低气候变化风险的主要选择之一。本项目以青岛崂山为研究地点，以13个三元组（即黑松-刺槐人工混交林及其对应黑松人工纯林和刺槐人工纯林）共39块样地为研究对象，通过钻取生长芯的方法，在不同组织水平（群落、种群和个体水平）上量化对比生产力（以胸高断面积的增量为单位）及其时间稳定性的格局。研究发现黑松-刺槐人工混交林生产力高于黑松和刺槐纯林生产力，这是由于混交林中黑松比刺槐表现较高的径向生长和高生长，表明黑松和刺槐两树种因耐荫性、叶物候期等生态位差异对而产生林冠层对光资源的互补利用。混交林中黑松生产力在不同林分发展阶段（0~60年）均高于其纯林，但混交林中刺槐生产力在林龄20~25年后高于其纯林，这由于混交林中刺槐的径向生长和高生长均高于其纯林。此外，研究结果发现随林分发展混交林中的刺槐胸径较黑松快，表明两树种对生长条件的异步性。最后，黑松和刺槐混交提高了生产力的时间稳定性，阐明两树种通过种间竞争或种间促进而产生的时间生态位互补。这些结果为黑松-刺槐人工混交林可持续经营提供理论依据。

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