US EPA

3546864 

Journal Article 

Letter 

Light asymmetry explains the effect of nutrient enrichment on grassland diversity 

Demalach, N; Zaady, E; Kadmon, R 

2017 

Yes 

Ecology Letters
ISSN: 1461-023X
EISSN: 1461-0248 

20 

1 

60-69 

English 

27933739 

10.1111/ele.12706 

WOS:000390026200006 

One of the most ubiquitous patterns in plant ecology is species loss following nutrient enrichment. A common explanation for this universal pattern is an increase in the size asymmetry of light partitioning (the degree to which large plants receive more light per unit biomass than smaller plants), which accelerates the rates of competitive exclusions. This 'light asymmetry hypothesis' has been confirmed by mathematical models, but has never been tested in natural communities due to the lack of appropriate methodology for measuring the size asymmetry of light partitioning in natural communities. Here, we use a novel approach for quantifying the asymmetry of light competition which is based on measurements of the vertical distribution of light below the canopy. Using our approach, we demonstrate that an increase in light asymmetry is the main mechanism behind the negative effect of nutrient enrichment on species richness. Our results provide a possible explanation for one of the main sources of contemporary species loss in terrestrial plant communities.