黄土高原典型小流域草地群落功能性状对土壤水分的响应

植物功能性状可以响应生境的变化并决定生态系统的功能,探究植物功能性状间的关系及其随土壤有效水分梯度的变化规律,对认识不同水分条件下植被在群落水平碳水代谢关系和维持水分平衡的生理生态学机制具有重要意义。以甘肃定西典型半干旱黄土小流域草地群落为研究对象,采用排序分析和回归拟合方法,分析了30个代表性草地样地中7个植物功能性状加权均值对土壤有效水分的响应以及响应性状间的相关关系。结果显示:(1)7个性状中,除叶宽与土壤有效水分无明显相关外,叶长、株高、叶面积、比叶面积、叶厚和叶干物质含量均与土壤有效水分显著性相关,可识别为草地在群落水平对土壤水分的响应性状。(2)草地群落通过降低株高,减小叶长、叶面积和比叶面积,增加叶厚和叶干物质含量以适应土壤有效水分减少;其中叶干物质含量的解释度最大,是土壤水分的最优响应性状。(3)除叶厚与叶长无显著相关外,其余功能性状均存在显著相关,说明草地群落的功能性状在土壤水分梯度上已基本形成了一个相互权衡或协同变化的功能性状组合。

Response of grassland community functional traits to soil water in a typical the Loess Plateau watershed

Plant functional traits can respond to habitat variation and also determine ecosystem functions. Therefore, studying the relationship between plant functional traits and their variation along soil available water gradients is of great significance for understanding the relationship between plant carbon and water metabolism and the physiological and ecological mechanism underlying the maintenance of water balance under different water conditions. The study was conducted using a typical semi-arid loess watershed grassland in Dingxi, Gansu Province, China, where the responses of community functional traits to soil available water at 30 representative grassland sites were analyzed. (1) All seven of the plant functional traits examined (leaf width, leaf length, leaf area, specific leaf area, plant height, leaf thickness, and leaf dry matter content), except leaf width, were significantly correlated with soil available water, which could be identified as the response of grassland to soil water at community level.(2) Grassland communities can adapt to the decreasing soil available water by reducing plant height, leaf length, leaf area, and specific leaf area and increasing leaf thickness and leaf dry matter content. In the present study, the leaf dry matter content exhibited the greatest explanation capacity and was the optimal response trait of soil water. (3) With the exception of leaf thickness and leaf length, all other pairs of the functional traits were significantly correlated. This indicates that the functional traits of grassland communities have either formed a functional trait combination that is a mutual trade-off or have synergistically changed along the soil water gradient.