Nutrient Use Efficiency of Three Fast Growing Hardwood Species across a Resource Gradient

Abstract

Attitudes regarding traditional energy sources have shifted toward renewable resources. Specifically, short-rotation woody crop supply systems have become more prevalent for biomass and biofuel production. However, a number of factors such as environmental and inherent resource availability can limit tree production. Given the intensified demand for wood biomass production, forest and plantation management practices are focusing on increasing productivity. Fertilizer application, while generally one of the least expensive silvicultural tools, can become costly if application rates exceed nutrient uptake or demand of the trees especially if it does not result in additional biomass production. We investigated the effect of water and varying levels of nitrogen application (56, 112, and 224 kg?N?ha–1?yr–1) on nutrient content, resorption efficiency and proficiency, N:P and the relationship with ANPP, as well as leaf- and canopy-level nutrient use efficiency of nitrogen, phosphorus, and potassium for Populus deltoides, Quercus pagoda, and Platanus occidentalis. P. deltoides and P. occidentalis reached their maximum nitrogen budget with the application of water suggesting old agricultural fields may have sufficient nutrient levels to sustain short-rotation woody crops negating the application of additional nitrogen for these two species. Additionally, for P. deltoides and Q. pagoda application of nitrogen appeared to increase the uptake of phosphorus however, resorption efficiency for these two species were more similar to studies conducted on nutrient poor sites. Nutrient resorption proficiency for all three nutrients and all three species were at levels below the highest rates of nitrogen application. These findings suggest maximum biomass production may not necessarily be tied to maximum nutrient application.