虞山次生林三种栎树生态化学计量学特征分析

摘 要: 栎树是北半球温带阔叶树种的重要组成部分，具有很高的经济价值和生态价值。化学计量学是一门用以研究生物体内各种化学元素的耦合关系及其在生态系统中养分循环的科学。通过对叶片、土壤和凋落物进行化学计量学的研究，可以更好地认识栎树养分需求的生理机制。本文综述了国内外植物化学计量学研究的文献，认为植物的生态化学计量特征往往与有机体和环境因子密切相关。植物对化学元素的吸收也与土壤、叶片中的化学计量比有线性关系，但规律性尚不明确，对于植物物种/属的化学计量特征研究较少。以栎属植物为例，各树种的N/P比几乎趋于稳定，而N、P的含量基本随着纬度升高、温度降低而升高，存在一定线性关系。目前，国内外对于不同尺度控制因素的植物化学计量研究还知之甚少，可以具体对栎属进行控制变量的化学计量学研究，探求栎树的化学计量特征和养分需求。为研究栎树养分吸收的生理机制和栎树培育奠定基础。

关键词: 栎属；生态位；C、N、P化学计量；养分循环

Abstrct: As important components of temperate broad-leaved forests in the northern hemisphere, oak species have high economic value and ecological value. Stoichiometry is the study of the coupling of various chemical elements in an organism and their nutrient cycling through the ecosystem. Studying the stoichiometry in leaves, soil and litters is pivotal to study the physiological mechanism of nutrient demand of oaks. This paper reviews the literatures on phytochemometrics at home and abroad, and concludes that the ecological stoichiometric characteristics of plants are often closely related to organisms and environmental factors. The absorption of chemical elements by plants also has a linear relationship with the stoichiometric ratio in soil and leaves, but the regularity is not clear, and there are few studies on the stoichiometric characteristics of a single species/genus. Taking oaks as an example, the N/P ratio of each single species almost tends to be stable, while the content of N and P basically increases with the increase of latitude and the decrease of temperature, showing a certain linear relationship. At present, the phytostoichiometric study on the control factors at different scales at home and abroad is little. The stoichiometric studies on the control variables of this single genus, Quercus, can be carried out to explore the stoichiometric characteristics and nutrient requirements of oaks. It lays a foundation for studying the physiological mechanism of nutrient absorption by oaks and the cultivation of oaks.

Key words: Quercus; Ecological niche; C、N、P stoichiometry; Nutrient cycle

1 研究背景

栎树，又名橡树，为壳斗科栎属(Quercus)植物的通称，常绿或落叶乔木，稀有灌木。栎树分布广泛，南北均有分布，是温带阔叶林的主要树种。喜光、深根性，对土壤条件要求不严，能在干旱瘠薄的山地生长，湿润、排水良好、肥沃的中性微酸性的土壤最适宜生长。栎树常与其它阔叶树组成混交林，有时成小片纯林。它们为其他生物提供栖息地和食物，包括鸟类、松鼠和许多昆虫，而这些生物又为其他种类的野生动物提供食物。它们与外生菌根（ECM）和其他真菌的关系影响微生物组成，影响营养循环和生态系统功能(Cavender-Bares, 2018)。栎树树形高大优美，树皮有发达的木栓层，根系发达，具有园林美化、防风抗火、保持水土的重要作用。除此以外，栎树的木材、栓皮、果实等都有很高的经济价值(张金香等, 2014)。

虞山位于江苏省常熟市，处于北亚热带的边缘，气候温和、四季分明，其森林植被类型以亚热带常绿落叶阔叶混交林为主。虞山最高峰海拔263米，主要土壤类型是黄棕壤，土壤均呈酸性，pH约为5-6。虞山得天独厚的气候环境和土壤条件为栎树的生长以及栎树资源的开发利用创造了优越的地理环境，提供了充足的养分来源。

在栎树的生长发育过程和生理代谢过程中，随着环境因子等多因素的变化，植物叶片内的干物质含量发生变化，植物叶片内各种化学元素的含量和比值呈现出一定的改变，从而引起光合速率、呼吸速率等一系列代谢的变化以及抵御寒冷及强光照等生理机制的响应，对栎树的形态指标、根冠比等产生影响(刘振西, 1994)。