A comparison of the foliar nutrient status of elfinwood and symmetrically formed tall trees, Colorado Front Range, USA

We tested the hypothesis of nutrient limitation in the trees of the alpine forest - tundra ecotone by comparing the foliar nutrient status of windsculpted elfinwood (also called krummholz) growing at the upper limit of tree success with symmetrically formed tall trees growing at the nearby timberline. The species investigated included Picea engelmannii (Parry) Engelmann, Abies lasiocarpa (Hooker) Nuttall, Pinus flexilis James, and Pinus aristata Bailey. The foliar nutrient concentrations of the ecotone trees were similar to other healthy montane forests. Most of the significant differences in mean foliar nutrient concentrations between elfinwood and tall trees indicate lower concentrations in elfinwood trees. We found significantly lower mean phosphorus concentrations in Picea engelmannii and Abies lasiocarpa elfinwood compared with tall trees, but the mean nitrogen-phosphorus ratios were within the normal range. The foliar nutrient status of Pinus aristata elfinwood was similar to tall trees, while Pinus flexilis had considerably more significant differences in nutrient concentrations between the tree forms. Although there are many theoretical processes that could cause nutrient deficiencies at treeline, this study suggests that the elfinwood along the Colorado Front Range is not currently nutrient deficient. We discuss the potential differences in nutrient ecology between elfinwood and tall trees.