The Effects of Soil Temperature and Nitrate on Fine Root Construction and Maintenance Costs in Northern Hardwood Forests

森林树木在光合作用过程中固定在叶片中的碳有一半以上被分配给细根的生产，但污染和气候变化对这些根的生产和寿命的影响尚不清楚。我们将研究土壤温度和土壤硝酸盐（五大湖地区常见的污染物）与糖枫林细根产生和死亡之间的关系，以便更好地预测污染增加和/或气候变暖时可能发生的情况。我们的研究地点南北相隔数百公里，并且有一个内置的温度梯度，跨越了由于全球变暖可能发生的温度升高的可能范围。此外，我们将施用大量的硝酸盐，看看这种特殊的污染物对根部有什么影响。使用最初用于关节镜手术的小型摄像机，我们将从永久安装在土壤中的小型观察管中观察根的出生，生长和死亡。使用这种方法，我们可以比较较冷和较暖森林之间的根系活动，以及硝酸盐输入高和低的森林之间的根系活动。我们还将测量根呼吸速率。由于活细胞的代谢活动随着温度的升高而加快，因此在较温暖的土壤中，根呼吸速率应该更高。这意味着生长在温暖土壤上的树木必须消耗更多的能量来维持足够的活根来吸收水分和养分。我们认为硝酸盐也会增加根呼吸速率，因为硝酸盐必须转化为铵（需要更多的能量），植物才能利用它作为氮的来源来生长。结果形成了这种变化和森林生态系统中污染物沉积的增加。

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.