ROW: Nutrient Uptake and Growth in Eastern Deciduous Tree Seedlings

本研究将研究一系列森林树种的离子吸收率、相对生长率和土壤养分依赖性之间的关系，这些树种的相对生长率和冠层间隙定殖能力差异很大。 假设： 1）具有高相对生长速率的间隙定殖物种将比生长缓慢的物种具有更高的最大离子吸收能力； 2) 相对生长速率较低的耐荫物种在低养分浓度下比快速生长的间隙定植物种具有更高的根系吸收能力； 3) 对于土壤可移动离子（例如 NO3 和 K），这些差异最大，而对于土壤不可移动离子（例如 PO4 和 NH4），这些差异较小； 4）适应低营养条件的幼苗的养分吸收率高于适应高营养条件的幼苗，并且对于相对生长率高的物种，这种可塑性更大； 5) 在田间，间隙定植幼苗比生长缓慢、耐荫的物种更敏感，不仅对间隙地点的光照增加，而且对受精地点养分的增加也更敏感。 东部落叶林的六种树种将从种子中生长出来。 其中三个物种代表具有高相对生长率的间隙定殖物种（Prunus serotina、Quercus coccinea 和 Betula populifolia），另外三个代表具有低相对生长率的耐荫物种（Fraxinus americana、Carya ovata 和 Quercus borealis）。 将进行三个独立的实验来检验这些假设。

This study will examine the relationship between ion absorption rate, relative growth rate, and the soil nutrient dependence of a suite of forest tree species that vary widely in both relative growth rate and canopy gap colonization ability. It is hypothesized that: 1) Gap colonizing species with high relative growth rates will have higher maximum ion absorption capacities than slowly growing species; 2) Shade tolerant species with low relative growth rates will have higher root absorption capacities at low nutrient concentrations than fast growing, gap colonizing species; 3) These differences will be greatest for soil mobile ions such as NO3 and K and less for soil immobile ions such as PO4 and NH4; 4) Nutrient uptake rates will be greater for seedlings acclimated to low nutrient conditions than to high nutrient conditions, and that this plasticity will be greater for species with high relative growth rates; 5) In the field, gap colonizing seedlings will be more responsive than slowly growing, shade tolerant species not only to increased light availability in gap sites but also to increased nutrient availability in fertilized sites. Six tree species of the eastern deciduous forest will be grown from seed. Three of these species represent gap colonizing species with high relative growth rates (Prunus serotina, Quercus coccinea, and Betula populifolia), and three represent shade tolerant species with low relative growth rates (Fraxinus americana, Carya ovata, and Quercus borealis). Three separate experiments will be performed to test the hypotheses.