格氏栲种子萌发对林窗与凋落物协同影响的权衡策略研究

The combination of physical, chemical and microbiological effects of litter is one of the key factors in determining seed germination and natural regeneration. At present, the study on the effects of forest litter on seed germination is limited to a single mechanism, and it is difficult to clarify the multi-factors coupling mechanism and trade-off strategy of seed germination process without considering the cooperative effect of gap environmental heterogeneity and litter on seed germination. Therefore, taking Castanopsis kawakamii natural forest in subtropical area as the object, we study the differences of litter effect, including the physical blockade, nutrient release, allelopathic effect and pathogen invasion to the seed germination of C. kawakamii in forest gap and non-gap by field random zone design and indoor control experiment. Besides, we quantitatively analyze the effects of gap disturbance on the seed germination of C. kawakakii, and reveal the proportion of positive and negative effects of litter. We also discuss the direct and indirect effects of positive and negative effects of gap and non-gap litter. Moreover, we ascertain the decisive factors that effected the seed germination in the gaps and non-gaps, and to verify the seed germination whether had different trade-off strategy to the litter effects in forest gap and non-gap. Therefore, we clarify the coupling mechanism of multiple factors by combining the cooperative effect of environmental heterogeneity and litter to the process of C. kawakamii seed germination. The research will enrich the research methods and theories of the feedback mechanism of gap - litter - seed germination, and provide an important theoretical support and practical reference for natural regeneration and sustainable development of natural forest.

凋落物的物理、化学与微生物的综合效应是决定种子萌发与自然更新的关键因素之一。目前森林凋落物对种子萌发影响研究局限于单一效应机制研究，并未考虑林窗微环境与凋落物协同作用影响种子的萌发过程，难以明确种子萌发过程多因素耦合机制及其权衡策略。为此，以中亚热带格氏栲天然林为对象，采用野外随机区组与室内控制实验探讨林窗与非林窗凋落物的物理阻断、养分释放、化感效应与病原菌侵害对格氏栲种子萌发的影响是否存在差异，定量分析林窗干扰增加或降低凋落物正负效应的比例，阐述凋落物正负效应因子间直接作用与间接作用，确定影响林窗与非林窗种子萌发的决定性因子，验证种子萌发对林窗与非林窗凋落物的权衡策略是否存在差异，从而阐明林窗与凋落物协同作用下的格氏栲种子萌发过程多因素耦合机制。该研究将丰富林窗-凋落物-种子萌发的反馈机制的研究方法与理论，为实现天然林自然更新与可持续发展提供重要理论支撑与实践参考。

凋落物的物理、化学与微生物的综合效应是决定种子萌发与自然更新的关键因素之一。目前森林凋落物对种子萌发影响研究局限于单一效应机制研究，并未考虑林窗微环境与凋落物协同作用影响种子的萌发过程，难以明确种子萌发过程多因素耦合机制及其权衡策略。为此，以中亚热带格氏栲天然林为对象，采用野外随机区组与室内控制实验探讨林窗与非林窗凋落物的物理阻断、养分释放、化感效应与病原菌侵害对格氏栲种子萌发的影响是否存在差异，阐述凋落物正负效应因子间直接作用与间接作用，确定影响林窗与非林窗种子萌发的决定性因子，验证种子萌发对林窗与非林窗凋落物的权衡策略是否存在差异，从而阐明林窗与凋落物协同作用下的格氏栲种子萌发过程多因素耦合机制。结果表明：（1）凋落物覆盖降低了种子萌发，提高了幼苗生长阶段的形态可塑性，且不同覆盖厚度下幼苗均表现为多元且稳定的资源获取策略。同时，中林窗对种子更新起显著促进作用，随面积增加抑制作用增强。（2）林窗形成通过改变林内微环境异质性等影响凋落物分解，其中土壤pH、土壤全碳、土壤全磷和空气温湿度是影响林窗地表凋落分解的主要因素。（3）林窗-凋落物化感作用对格氏栲种子更新存在一定的交互效应。随林窗面积减小，不同浓度凋落物浸提液对格氏栲幼苗生长的影响呈先升再降后上升趋势，而中林窗不同浓度凋落物浸提液均促进格氏栲种子萌发及幼苗生长。（4）随林窗面积增大，林窗提高了土壤细菌多样性、生长季土壤微生物多样性及非生长季土壤真菌多样性，使森林土壤生态系统朝着健康稳定的方向发展。（5）凋落物化感物质木糖含量和棕榈酸含量对格氏栲种子萌发影响的相对贡献较高，而凋落物分解速率和土壤全碳含量对胚根生长的相对贡献较高于其它环境因子。该研究将丰富林窗-凋落物-种子萌发的反馈机制的研究方法与理论，为实现天然林自然更新与可持续发展提供重要理论支撑与实践参考。