More than half of all carbon fixed in the leaves of forest trees during photosynthesis is allocated to the production of fine roots, but the effects of pollution and climate change on the production and longevity of these roots is unknown. We will study the relationship between soil temperature and soil nitrate (a common pollutant in the Great Lakes region) and the production and death of fine roots in sugar maple forests in order to better predict what might happen in pollution increases and/or the climate warms. Our study sites are separated by several hundred kilometers from north to south, and there is a built-in temperature gradient that spans the possible range of temperature increases that may occur due to global warming. In addition, we are going to apply large amounts of nitrate to see what effect this particular pollutant has on the roots. Using small cameras first developed for use during arthroscopic surgery, we will observe the birth, growth and death of roots from small observation tubes permanently installed in the soil. Using this approach, we can compare root activity between colder and warmer forests, and between forests subject to high and low inputs of nitrate. We will also measure rates of root respiration. Because metabolic activity in living cells speeds up as temperatures increase, root respiration rates should be higher in warmer soils. This means that the trees growing on warmer soils must expend more energy to maintain enough living roots to take up water and nutrients. we think that nitrate will also increase root respiration rates, because the nitrate must be converted to ammonium (requiring more energy) before plants can use it as a source of nitrogen for growth. The results form this change and increased pollutant deposition on forest ecosystems.
