W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI, 49060, USA,
Oecologia. 2013 Dec;173(4):1513-20. doi: 10.1007/s00442-013-2722-8. Epub 2013 Jul 10.
Declines in species richness due to fertilization are typically rapid and associated with increases in aboveground production. However, in a long-term experiment examining the impacts of fertilization in an early successional community, we found it took 14 years for plant species richness to significantly decline in fertilized plots, despite fertilization causing a rapid increase in aboveground production. To determine what accounted for this lag in the species richness response, we examined several potential mechanisms. We found evidence suggesting the abundance of one functional group-tall species with long-distance (runner) clonality-drove changes in species richness, and we found little support for other mechanisms. Tall runner species initially increased in abundance due to fertilization, then declined dramatically and were not abundant again until later in the experiment, when species richness and the combined biomass of all other functional groups (non-tall runner) declined. Over 86 % of the species found throughout the course of our study are non-tall runner, and there is a strong negative relationship between non-tall runner and tall runner biomass. We therefore suggest that declines in species richness in the fertilized treatment are due to high tall runner abundance that decreases the abundance and richness of non-tall runner species. By identifying the functional group that drives declines in richness due to fertilization, our results help to elucidate how fertilization decreases plant richness and also suggest that declines in richness due to fertilization can be lessened by controlling the abundance of species with a tall runner growth form.
由于施肥导致物种丰富度下降通常是迅速的，并伴随着地上生物量的增加。然而，在一项长期实验中，我们研究了施肥对早期演替群落的影响，发现尽管施肥导致地上生物量迅速增加，但植物物种丰富度在施肥小区显著下降却需要 14 年的时间。为了确定物种丰富度响应滞后的原因，我们研究了几种潜在的机制。我们发现有证据表明，一个功能群——具有长距离（runner）克隆特性的高大物种——的丰度变化驱动了物种丰富度的变化，而其他机制的证据很少。高大的 runner 物种最初由于施肥而增加了丰度，然后急剧下降，直到实验后期才再次变得丰富，此时物种丰富度和所有其他功能组（非高大 runner）的生物量都下降了。在我们的研究过程中发现的 86%以上的物种是非高大 runner，非高大 runner 和高大 runner 生物量之间存在很强的负相关关系。因此，我们认为施肥处理中物种丰富度的下降是由于高大 runner 丰度的增加，这降低了非高大 runner 物种的丰度和丰富度。通过确定由于施肥导致丰富度下降的功能群，我们的结果有助于阐明施肥如何降低植物丰富度，同时也表明通过控制具有高大 runner 生长形式的物种的丰度，可以减轻由于施肥导致的丰富度下降。
