【摘要】 科学家早已注意到 ,具有长叶寿命的植物通常生长于营养和 (或 )水分较为缺乏的环境 ,而具短叶寿命的植物一般生长在具有较高的营养可利用性地带。国外大量的实验研究结果表明 ,单位重量的叶氮含量 (Nmass)与叶的最大光合速率存在密切正相关 ,而比叶面积 (单位干重量的叶面积 )与植物生产单位叶面积的物质成本呈负相关 ,二者又随叶寿命的增加而降低 ,这种相互关系几乎在所有植物种群和群落中都普遍存在 ,反映了植物对环境适应的趋同进化特征 ,是进一步理解生态系统行为特征的基础。松属 (Pinus)及云杉 (Picea)、冷杉 (Abies)等常绿针叶树种的叶寿命一般随海拔的升高而增大 ,其相关叶性状也普遍存在明显的垂直分布格局 :随着海拔升高 ,单位面积的叶氮含量 (Narea)及最大光合速率增加 ,而比叶面积则减少。一般认为 ,长的叶寿命是对高寒及养分、水分贫乏等胁迫环境的适应 ,而短的叶寿命和 (或 )落叶性被认为是植物为了快速生长以及对干旱或寒冬等季节性胁迫环境的适应结果。根据成本_效益分析理论 ,在特定环境条件下叶寿命大小取决于形成并维护单位叶面积所需要的物质消耗与叶片碳收获的平衡 ,与常绿 /落叶森林植被纬向 /垂直地带性分布存在一种内在联系机理。因此 ,叶寿命及其相关叶性状成为将叶片水平上的更多还原

【Abstract】 It is well known that plants with long leaf lifespans are found to grow mostly in habitats where nutrient availability is low and/or water is limited, while plants with short leaf lifespans usually occur on sites with relatively h igh nutrient availability. Considerable research conducted worldwide indicates t hat leaf mass-based nitrogen concentrations (N mass ) are positively rel ated to ma ximum photosynthetic rates, and specific leaf area (leaf area per unit dry weigh t) shows a negative relationship with leaf construction cost, and both decrease with increased leaf lifespan. These relationships among leaf traits generally ex ist across wide ranges of plant populations, communities and biomes, apparently reflecting convergent adaptation of plants to the given climate and/or other env ironmental constraints. Therefore, knowledge about leaf traits is important t o further understand the structure and function of plant ecosystems. With increasing altitude, leaf lifespan generally increases. Associated leaf tra its also show general altitudinal trends: leaf area-based nitrogen concentration s and maximum photosynthetic rates both increase, whereas specific leaf area dec reases with increasing elevation. Plants with long leaf lifespans are thought to be adapted to environmental stresses, such as low temperatures, short growing s e ason length or low light and nutrient availability, while those with short leaf lifespans tend to be associated with fast rates of relative growth and carbon fi xation in response to seasonal stresses of drought and/or cold winters. Under gi ven environmental constraints, the cost-benefit hypothesis explains that variati ons in leaf lifespan are controlled by the trade-offs between leaf carbon costs and benefits for maximizing carbon gain of plants. Cost-benefit simulations nice ly predict a global bimodal distribution of evergreen forests. Accordingly, leaf lifespan and its related leaf traits appear to provide a conceptual link betwee n processes at short-term leaf scales and long-term whole plant and stand-level scales. Knowledge about patterns of leaf lifespan and associated leaf traits acr oss biomes would help us to develop a processing link between biogeography model s and biogeochemistry models and to further understand mechanisms of vegetation dynamics in response to global change. However, there is limited knowledge on ho w leaf characteristics might be used to deduct ecosystem function information and how this scaling task could be accomplished. The traditional focus of plant ecophysiology, understanding how plants cope with often-stressful habitats, is organism centered. It is still difficult to quantitatively describe the relati onships among community characteristics, climatic factors and leaf characteristi cs due to a lack of field data at the ecosystem level. In China, there has been very little work on the ecology of leaf lifespan and its related traits, so it’s a challenge and fruitful area for the future research.更多还原