喀斯特峰丛洼地植物时空分布的生理生态适应及群落构建机制

It is crucial to controlling rocky desertification that adaptability of vegetation to stressed environments in depressions between karst hills, such as strong heterogeneity, fragile environment, poor soils, and serious loss of soil and water, and so on. However, it has been neglected in the previous researches. Four successional stages (i.e., grass, brush, secondary forest, and primary forest) and 20 typical communities are chosen to build four dynamic monitoring plots and 120 auxiliary quadrats, respectively. Based on the comprehensive investigation, the research intends to reveal the differences of photosynthetic physiological features among plants at population and individuals scales, and to clarify temporal-spatial pattern evolution of vegetation along community succesions at community and landscape scales. Principal component analysis (PCA) and canonical corresponding analysis (CCA) are applied to find out the major factors of influencing vegetation temporal-spatial distribution and photosynthetic physiological features of typical plants, and to show interaction relationships between groups of vegetation, soil physic and chemical properties, soil microbe, soil mineral nutrients, topography, and human activities, and further to structure their coupling coordinative models. Detrended canonical correspondence analysis (DCCA) is used to demonstrate vegetation distribution along ecological environmental gradients and to construct neutral model. Variation partitioning quantifies the contribution rates of each group to vegetation temporal-spatial distribution, and then evaluates the suitability of neutral theory and niche theory. The research finally aims to explore a community assembly method or theory suited to depressions between hills in karst region. This would promote the development of community ecology and provide guide for vegetation quick recovery and ecological restoration in depressions between karst hills.

植物对喀斯特峰丛洼地异质性高、生态环境脆弱、土壤瘠薄、水土流失严重等胁迫环境的适应性是石漠化治理的关键，但这却被以往研究所忽视。本项目选择喀斯特峰丛洼地草丛、灌丛、次生林和原生林4个演替阶段及20个典型群落，建立4块动态监测样地和120块辅助性样方，基于全面调查分析，从种群(个体)尺度探讨不同植物光合生理特征的差异，从群落和景观尺度分析植被随群落演替的时空格局变化，用PCA、CCA等方法找出影响植被时空分布和典型植物光合生理特性的主要因子，揭示植被与土壤理化性状、土壤微生物、土壤矿质养分、地形、人类活动等集团因子之间的关系，构建其耦合协调度模型；用DCCA表征植被沿生态环境梯度的分布，建立中性模型，量化各集团因子对植被时空分布的贡献率，综合评价中性理论和生态位理论的相对适宜性，揭示喀斯特峰丛洼地植物群落的构建机制，为群落生态学发展、喀斯特峰丛洼地植被迅速恢复和生态重建提供理论依据。

植物生长对环境胁迫的响应是生态治理的关键。本项目基于典型植物、群落样方和动态监测样地的系统调查与分析，获得结论如下：.1）黄荆和盐肤木的净光合速率日变化为“双峰”曲线，有“午休”现象，八角枫和红背山麻杆为“单峰”曲线；4种植物均为阳生植物，光补偿点均较低，而光饱和点都较高，能很好地适应喀斯特环境。.2）狗骨木、南酸枣在5和150 mmol•L-1的钙离子浓度下各项生长和生理指标处于较高水平，表现出较好的适应性；在300 mmol•L-1的钙离子浓度下受到了胁迫，狗骨木适应性较好。.3）喀斯特地区单子叶和双子叶植物、落叶和常绿植物的叶片有不同的防御缺水结构，其形态结构对干旱响应模式不同。.4）不同森林生态系统的主要影响因子不同，植被与土壤的空间分布格局不同，物种共存机制不同。在环境条件恶劣及群落演替初级阶段，生态位分化理论占有较重要的地位，而在环境条件优越，群落发展到稳定的顶极群落，物种共存机制更符合中性理论。.5）退耕还林还草时限短，不同模式处于低物种分布的较高水平状态，生物量很小；土壤生态系统的主要影响因子是土壤主要养分；不同模式的植被土壤耦合度和耦合协调度模型不同，均没有达到良好协调发展状态。.6）沿植物群落的顺向演替发展，重要值＞10.00的科、属、种及物种多样性最大值出现在次生林，群落结构最佳值出现在原生林；各生态系统影响因子不同，土壤微生物处于主导地位，其次为灌丛；植物多样性与土壤N、Al2O3、Fe2O3、MBC、真菌和细菌关系密切。.7）喀斯特原生森林样地内胸径≥1 cm的木本植物独立个体共10，9728株，隶属于227种59科144属；木本植物径级分布和物种相对频度均呈倒“J”型分布，主要优势树种均呈聚集型分布，且形成互补；物种多样性表现出较强的区域性分布特征，具有尺度依赖性。.发表论文31篇，其中SCI/EI 论文5篇；专著1部；申请专利3项，授权1项；培养研究生12名。.建议：坚持25公顷动态监测样地的长期监测，深入研究喀斯特植物多样性的构建机制和森林生态系统的稳定机制。