Soil nitrate and ammonium: Tree Competition Garden

This experiment was set up adjacent to E055 in the high disturbance, garden area. 1.75 inches of black soil was added to the CCNHA sandy soil to make four 10 feet x 54 feet plots. The soil was rototilled and aluminum flashing was installed to edge the plots and divide them into 48, 5 feet x 9 feet plots. Equal amounts of MgSO4, CaCO3, P2O5 and K2O are added to the plots each year in early May and late June. For a describtion of fertilizer added, see fertilization details. Seeds were planted with 6 replicates of each of the following treatments:

1. Agropyron repens monoculture
2. Schizachyrium scoparium monoculture
3. Pinus strobus monoculture
4. Quercus ellipsoidalis monoculture
5. Agropyron repens + Quercus ellipsoidalis on half
6. Agropyron repens + Pinus strobus on half
7. Schizachyrium scoparium + Quercus ellipsoidalis on half
8. Schizachyrium scoparium + Pinus strobus on half

The competition plots were split, with half invaded by seed and half to be invaded by seedling. For treatments 5-8, the right or left sides were chosen at random, to plant the tree seeds. The plots were watered throughout the growing season to keep water from becoming a limiting resource.

本实验设置于高干扰园区内紧邻E055的区域。向CCNHA砂质土壤中添加1.75英寸厚的黑土，构建4块10英尺×54英尺的样地。对样地土壤进行旋耕，并安装铝制封边条以划分样地边界，随后将其拆分为48块5英尺×9英尺的子样地。每年5月初与6月末，向各子样地施加等量的硫酸镁（MgSO4）、碳酸钙（CaCO3）、五氧化二磷（P2O5）与氧化钾（K2O）。关于施加肥料的具体说明，详见施肥细则。
本实验针对以下8种处理各设置6次重复，采用播种方式进行种植：
1. 匍匐冰草（Agropyron repens）单优群落
2. 小须芒草（Schizachyrium scoparium）单优群落
3. 北美白松（Pinus strobus）单优群落
4. 椭圆叶栎（Quercus ellipsoidalis）单优群落
5. 半侧配置匍匐冰草与椭圆叶栎
6. 半侧配置匍匐冰草与北美白松
7. 半侧配置小须芒草与椭圆叶栎
8. 半侧配置小须芒草与北美白松
竞争处理样地被拆分为两部分，一半通过种子直接入侵，另一半待幼苗入侵。针对处理5至8，随机选取样地的左侧或右侧区域播种乔木种子。在整个生长季对样地进行补水作业，以避免水分成为限制因子。