State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing 100093, China.
Ann Bot. 2011 Jan;107(1):145-55. doi: 10.1093/aob/mcq219. Epub 2010 Nov 17.
Changes in supplies of resources will modify plant functional traits. However, few experimental studies have addressed the effects of nitrogen and water variations, either singly or in combination, on functional traits.
A 2-year field experiment was conducted to test the effects of nitrogen and water addition on leaf longevity and other functional traits of the two dominant (Agropyron cristatum and Stipa krylovii) and three most common species (Cleistogenes squarrosa, Melilotoides ruthenica and Potentilla tanacetifolia) in a temperate steppe in northern China.
Additional nitrogen and water increased leaf nitrogen content and net photosynthetic rate, and changed other measured functional traits. Leaf longevity decreased significantly with both nitrogen addition (-6 days in 2007 and -5·4 days in 2008; both P < 0·001) and watering (-13 days in 2007 and -9·9 days in 2008; both P < 0·001), and significant differences in leaf longevity were also found among species. Nitrogen and water interacted to affect leaf longevity and other functional traits. Soil water content explained approx. 70 % of the shifts in leaf longevity. Biomass at both species and community level increased under water and nitrogen addition because of the increase in leaf biomass production per individual plant.
The results suggest that additional nitrogen and water supplies reduce plant leaf longevity. Soil water availability might play a fundamental role in determining leaf longevity and other leaf functional traits, and its effects can be modified by soil nitrogen availability in semi-arid areas. The different responses of species to resource alterations may cause different global change ramifications under future climate change scenarios.
资源供应的变化会改变植物的功能特征。然而，很少有实验研究探讨过氮素和水分的变化，无论是单独作用还是联合作用，对功能特征的影响。
进行了为期两年的田间实验，以测试氮素和水分添加对中国北方温带草原两种优势种（冰草和羊草）和三种常见种（赖草、草木樨状黄芪和委陵菜）叶片寿命和其他功能特征的影响。
氮素和水分的添加增加了叶片的氮含量和净光合速率，并改变了其他测量的功能特征。叶片寿命随氮素添加（2007 年减少 6 天，2008 年减少 5.4 天；均 P < 0.001）和水分添加（2007 年减少 13 天，2008 年减少 9.9 天；均 P < 0.001）显著减少，而且在不同物种之间也存在显著差异。氮素和水分之间存在交互作用，影响叶片寿命和其他功能特征。土壤水分含量解释了叶片寿命变化的约 70%。由于每个植物个体的叶片生物量增加，在水和氮添加下，物种和群落水平的生物量都增加了。
结果表明，额外的氮素和水分供应会缩短植物叶片的寿命。土壤水分的有效性可能在决定叶片寿命和其他叶片功能特征方面起着根本作用，并且在半干旱地区，其效应可以被土壤氮素的有效性所改变。在未来气候变化情景下，不同物种对资源变化的不同响应可能会导致不同的全球变化后果。
