不同生活型树种苗木对弱光和干旱胁迫的响应

The abilities of trees to cope with weak light and drought stresses are the key factors to determine the survival and growth of seedlings in reforestation and low-yield forest improvement. Therefore, the mechanisms of respond to weak light and drought stresses for seedings have been the focus of many studies. Previous studies confirmed that plants can cope with weak light and drought stress by regulating physiology and phenology characteristics, morphological structure ,biomass allocation. There are differences in the plasticity of similar traits among different species and have positive or negative relationships among functional traits. Therefore, there has a large divergence of results and cannot form a universal law in the mechanism of trees coping with stress from a single species and a single kind traits. In this project, we propose the hypothesis that different tree species will trade-off and/or synergize different traits to form a system response strategy in response to resource changes. To test our hypothesis, we set control experiments with different light intensity and soil water, and propose to study the dynamic response laws of physiological characteristics, phenology and life span, organ morphological structure, biomass distribution of subtropical seedlings with different life forms. We will clarify the strategies to cope with stresses by trading off and/or synergizing function traits, and reveal the system response mechanism of seedlings with different life forms coping with light and water stress. The results could provide the theoretical basis for the forests construction and sustainable management.

对弱光和干旱的适应能力是决定造林和低产林改造中苗木成活和生长的关键因素，因此，苗木应对弱光和干旱胁迫的机制备受关注。前期研究证实植物通过调节生理特性、物候、形态结构、生物量分配等性状应对弱光和干旱等胁迫，但不同物种的同类性状可塑性存在差异，且功能性状间存在正或负向关系，因此，仅从单一物种和单一类性状揭示树木应对胁迫的机制，导致结果分歧较大，无法形成普适性规律。本项目中我们提出不同树种在应对资源变动时会权衡和（或）协同不同性状而形成系统应对策略的假说。为验证假说，我们以亚热带不同生活型树种苗木为对象，设置不同光照强度和土壤水分控制实验，研究不同生活型树种苗木的生理特性、物候、器官形态结构、生物量分配等性状对光照强度、土壤水分变化的动态响应规律，明晰不同生活型树种苗木权衡和（或）协同功能性状应对胁迫的策略，揭示不同生活型树种应对光和水分胁迫的系统响应机制，为森林营造及可持续经营提供理论依据

苗木对弱光和干旱的适应能力是决定造林和低产林改造中苗木成活和生长的关键因素。本项目选择不同生活型（常绿与落叶、针叶与阔叶）树种苗木为研究对象。采用大棚盆栽控制实验，研究不同生活型树种苗木的生物量分配、形态结构、生理特性、养分特征以及光合特性在不同光照强度和土壤水分下的响应规律。 .结果表明：①干旱对于4种生活型苗木的负面作用更强，而适度的遮荫能够促进植株生长。②在双重胁迫作用下，遮荫始终能够减轻干旱对刺柏、栓皮栎和楠木形态结构、生理特性和光合特性不利影响，且随着遮荫程度增加，缓解效果增加；落羽杉形态结构和光合特性在双重胁迫作用下始终低于单一胁迫，生理特性高于单一胁迫。③落羽杉通过增加渗透物质含量和酶活性抵抗干旱环境；弱光环境下，通过增加光合色素，提高光合能力，增大茎生物量占比来适应。④刺柏通过增加枝条和冠幅，降低叶生物量占比，提高比根长与比表面积，减小细根组织密度，升高渗透物质和酶活性，将更多的磷储存在细根中，增加光合色素，以此减轻胁迫造成的损害。⑤栓皮栎受胁迫时会提高比根长与比表面积、细根组织密度、渗透物质含量和酶活性、光合色素，净光合速率，提高气孔导度和蒸腾速率，将氮向细跟转移，达到自我保护。⑥楠木干旱胁迫下，通过提高茎生物量占比、细根组织密度，增加各渗透物质含量和酶活性，减少细根直径，向细根转移氮素，以此适应环境。本研究可丰富森林生产力动态变化理论，为森林营造和可持续经营提供科学指导，具重要理论和实践价值。