Soil nitrate and ammonium: The Small Biodiversity Experiment

Biodiversity I (E123), also called the “small biodiversity experiment,” was designed to determine how the number of species affects the dynamics of ecological processes at the population, community, and ecosystem levels. By experimentally manipulating the number of species and the kinds of species, the amount of plant growth and the change from year to year that result can be examined. Also, the effects of number of species on carbon and nitrogen in the soil and on the ability of other species to invade can be studied. The experiment contains 147 3 x 3m plots that were randomly allocated 1, 2, 4, 6, 8, 12 or 24 plant species. The particular species in a plot were randomly selected from a set of 24 prairie-grassland species which included seven warm-season (C4) grasses, four cool-season (C3) grasses, four legumes, nine non-legume forbs. Each level of number of species has 20 to 24 replicates. In this experiment not all of the species are in monocultures. The study was established in 1994 by lead investigators David Tilman, David Wedin, Peter Reich, and Johannes Knops. Experiment 123 is similar to Experiment 120, but it uses smaller plots and did not categorize by type of plant species prior to randomizing species to plots. This size of plot in Experiment 123 means that the soils are relatively more homogeneous and the desired number of species can be more easily maintained by frequent hand weeding than with larger plots. However, the small size of plots limits sampling and the nesting of other studies within the plots.生物多样性实验I（Biodiversity I，编号E123），又称"小型生物多样性实验"，旨在探究物种类群数量如何影响种群、群落及生态系统层面的生态过程动态。通过实验操控物种类群数量与物种组成，可观测由此引发的植物生物量变化及年度动态；此外，还可研究物种类群数量对土壤碳、氮含量以及外来物种入侵能力的影响。本实验共设置147个3×3米样地，随机分配种植1、2、4、6、8、12或24种植物。每个样地的具体植物物种均从24种草原草本物种中随机选取，该物种库包含7种暖季型（C4）草本、4种冷季型（C3）草本、4种豆科植物以及9种非豆科阔叶草本。各物种类群数量梯度均设置20至24个重复样地，且本实验并非所有物种均设置单种栽培样地。该实验于1994年由首席研究员David Tilman、David Wedin、Peter Reich及Johannes Knops牵头建立。E123实验与E120实验相似，但采用了更小的样地，且在将物种随机分配至样地前未预先按植物物种类型进行分类。E123实验的样地尺寸使得土壤相对更为均质，且相较于大型样地，可通过频繁人工除草更易维持预设的物种类群数量。不过，样地尺寸较小也限制了采样工作以及在样地内嵌套开展其他研究。