Department of Ecology and Evolutionary Biology, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA.
Ecol Lett. 2011 Apr;14(4):380-8. doi: 10.1111/j.1461-0248.2011.01599.x. Epub 2011 Feb 21.
Many researchers hypothesize that plant richness declines at high soil fertility (and high productivity) due to light limitation. We tested this hypothesis in an old-field by independently manipulating fertilization and light levels via shade cloth (decreased light), vegetation tie-backs (increased light) and vegetation clipping (increased light). Droughts occurred during two of the four years of the study, and we found that higher light levels were generally associated with decreased plant richness in drought years but increased plant richness in wet years. Most importantly, fertilization decreased richness whether light availability limited richness (wet years) or did not limit richness (drought years), and the effects of fertilization and light manipulation treatments were additive. These results suggest that effects of fertilization on plant richness are at least partly independent of light levels and that competition for resources other than light plays a substantial role in the decline of plant richness after fertilization.
许多研究人员假设，由于光照限制，植物丰富度会在高土壤肥力（和高生产力）下降。我们通过使用遮阳网（减少光照）、植被系绳（增加光照）和植被修剪（增加光照）来独立地操纵施肥和光照水平，在一片旧农田中验证了这一假设。在研究的四年中有两年发生了干旱，我们发现，在干旱年份，较高的光照水平通常与植物丰富度的降低有关，但在湿润年份，光照水平的增加与植物丰富度的增加有关。最重要的是，无论光照是否限制了丰富度（湿润年份），施肥都会降低丰富度，而且施肥和光照处理的效果是累加的。这些结果表明，施肥对植物丰富度的影响至少部分独立于光照水平，并且除光照以外的资源竞争在施肥后植物丰富度下降中起着重要作用。
