Scientists have identified why excessive fertilisation of soils is resulting in a loss of plant diversity. Extra nutrients allow fast growing plants to dominate a habitat, blocking smaller species’ access to vital sunlight, researchers have found. As a result, many species are disappearing from affected areas.
It was reported in Science that a team from the University of Zurich has warned that tighter controls were needed in order to prevent further loss to plant biodiversity. It is estimated that the global level of nitrogen and phosphorus available to plants has doubled in the past 50 years. Looking at grasslands, the researchers said it was widely recognised that an increase of chemical nutrients in an ecosystem led to a loss of diversity, but the mechanism of how it was occurring had been difficult to determine.
It would be logical to think that the more nutrients there are in the soil, the more biodiversity is possible, but the research has found that the presence of such resources led to a general increase in the strength of competition among plants. This means that Light becomes the critical resource, with shorter species being shaded out by taller species, resulting in a loss in diversity.
Experiments carried out by PhD student Yann Hautier at the University of Zurich’s Institute of Environmental Sciences used boxes containing fertilised soil and grasses. Additional light was used to compensate for the increased shading caused by the taller species.The findings led the team to conclude that it was the lack of access to light that affects diversity, not an increase in the strength of competition.