Hobbie Sarah E, Gough Laura
Department of Ecology, Evolution and behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN, 55108, USA.
Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, 35487, USA.
Oecologia. 2002 May;131(3):453-462. doi: 10.1007/s00442-002-0892-x. Epub 2002 May 1.
We compared foliar and soil nutrients in tundra between two different landscapes in the foothills of the Brooks Range, Alaska, that were deglaciated >50,000 and >11,500 years ago, respectively. Our goal was to determine whether foliar nutrients reflect differences in soil nutrient availability, or whether species and/or growth forms have characteristic foliar nutrient concentrations regardless of soil nutrient availability. Sites are located less than 2 km from one another, and both are dominated by moist tussock tundra. However, forbs are less common and deciduous and evergreen shrubs more common at the older site. Soils at the older site had higher net nitrogen (N) mineralization rates, but lower pH, cation exchange capacity, percent base saturation, exchangeable calcium (Ca) and magnesium, total Ca, and inorganic N and phosphorus than the younger site. Foliar nutrients generally reflected differences in soil net N mineralization rates and exchangeable base cations, with higher foliar N at the older site, and higher foliar Ca at the younger site. However, large differences in foliar nutrients also occurred among growth forms, and the magnitude of the site differences in foliar nutrients between sites was growth form-dependent. In general, species with short leaf lifespans (deciduous shrubs, sedges, and forbs) had higher foliar nutrient concentrations than evergreen species. Thus, foliar nutrients were a function both of underlying variation in soil nutrient availability and of species and growth form composition.
我们比较了阿拉斯加布鲁克斯山脉山麓两个不同景观中苔原的叶片和土壤养分，这两个景观分别在5万多年前和1.15万多年前经历了冰川消退。我们的目标是确定叶片养分是否反映了土壤养分有效性的差异，或者物种和/或生长形式是否具有特征性的叶片养分浓度，而不受土壤养分有效性的影响。两个研究地点相距不到2公里，均以湿润草丘苔原为主。然而，在较古老的地点，草本植物较少见，落叶和常绿灌木更为常见。较古老地点的土壤净氮（N）矿化率较高，但pH值、阳离子交换容量、碱饱和度百分比、可交换钙（Ca）和镁、总Ca以及无机N和P均低于较年轻的地点。叶片养分总体上反映了土壤净N矿化率和可交换碱性阳离子的差异，较古老地点的叶片N含量较高，较年轻地点的叶片Ca含量较高。然而，不同生长形式之间的叶片养分也存在很大差异，而且不同地点之间叶片养分的差异程度取决于生长形式。一般来说，叶片寿命较短的物种（落叶灌木、莎草和草本植物）的叶片养分浓度高于常绿物种。因此，叶片养分既是土壤养分有效性潜在变化的函数，也是物种和生长形式组成的函数。
