Measuring nutrient uptake by roots of sugar maple, red pine, and Norway spruce trees in situ (Acer saccharum, Pinus resinosa, Picea abies)

Freshly excavated intact roots often release nutrients in nutrient uptake experiments, possibly due to disturbance caused during excavation. I tested the effect of four pre-experiment treatments on net uptake of nutrients by sugar maple (Acer saccharum Marsh.), red pine (Pinus resinosa Ait.), and Norway spruce (Picea abies (L.) Karst.) in monospecific plantations in central New York. Roots were (1) "trained" to grow in a sand-soil mixture, (2) excavated and exposed to nutrient solution for two or (3) four days, or (4) freshly excavated. Roots were then exposed sequentially to three concentrations of nutrient solutions for 2 hours each. Net uptake rates increased with concentration for ammonium, nitrate, phosphate, potassium, sodium, and aluminum for all species. Net efflux of calcium increased with increasing concentration. Magnesium was not consistently taken up or released by all species. None of the pre-treatments improved uptake measurements consistently across all combinations of nutrients and species studied.