Soil bulk density: 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花园区域内E055样地附近。向CCNHA砂质壤土中施加1.75英寸厚的黑土，构建4块10英尺×54英尺的大型样地。随后对土壤进行旋耕处理，并安装铝制包边对大型样地进行分隔，最终将其划分为48块5英尺×9英尺的次级样地。每年5月初与6月末，向所有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）。关于本次实验所用肥料的详细说明，请参阅施肥细则。

以下各处理组均设置6次重复，播种方案如下：
1. 偃麦草（Agropyron repens）单作群落
2. 须芒草（Schizachyrium scoparium）单作群落
3. 北美乔松（Pinus strobus）单作群落
4. 椭圆叶栎（Quercus ellipsoidalis）单作群落
5. 半边种植偃麦草与椭圆叶栎的混作群落
6. 半边种植偃麦草与北美乔松的混作群落
7. 半边种植须芒草与椭圆叶栎的混作群落
8. 半边种植须芒草与北美乔松的混作群落

竞争类样地采用分区设计：一半区域通过种子入侵定殖，另一半则通过幼苗入侵定殖。针对处理组5至8，随机选取样地的左侧或右侧区域进行乔木种子播种。整个生长季均对样地进行灌溉，以避免水分成为实验的限制性资源。