Fertilisers 'reducing diversity'

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From the BBC:


Fertilisers 'reducing diversity'

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.

A team from the University of Zurich, writing in Science, warned that tighter controls were needed in order to prevent widespread biodiversity loss.

Estimates suggest that the global level of nitrogen and phosphorous 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.

"You would think that more [nutrients] would lead to more biodiversity," said co-author Andrew Hector, a researcher at the University of Zurich's Institute of Environmental Sciences.

"Yet it is considered to be one of the main threats to biodiversity this century."

'Winner takes all'

Professor Hector explained that there were two main hypotheses: "One is that the presence of more resources led to a general increase in the strength of competition among plants.

"The other is a little bit more mechanistic," he told BBC News.

"When you get an increase in fertilisation, you get an increase in productivity, leading to increased plant biomass and increased shading.

"This shifts the idea to light being the critical resource, with shorter species being shaded out by taller species, resulting in a loss in diversity."

Professor Hector's team, led by PhD student Yann Hautier, fitted lights to the understory of grass in boxes containing fertilised soil.

"Additional understory light compensated for the increased shading caused by the greater above-ground biomass production," they explained.

The supplementary light "prevented the loss of species and maintained… levels of diversity".

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.

"We have done the critical experiment that has been asking to be done for the past 35 years," said Professor Hector.

"If it all depends on light levels, then if you put the light back then you should prevent a loss of biodiversity."

However, he added that their findings did not offer a "magic bullet" for conservationists.

"What our research shows is that competition for light is very asymmetric.

"So if a plant can get between the sun and its competitors, not only can it get all the light it needs but it can also block its competitors' access to light.

"Because this competition for light is such a 'winner takes all', it emphasises how important it is that we control nutrient enrichment."
I don't mind if the plant I'm trying to cultivate is a the "winner who takes all" at least it will reduce the incidence of weeds in my garden, what do you all think?
I think in a cultivated setting like a garden it's the goal to have some plants out compete others, and that as gardeners we stack the deck in the favor of the plants we want. I believe what the article was referencing was less formally cultivated settings, and even wild areas. The amount of fertilizers we humans are injecting into the ecosystem is huge, just look at the problems with dead zones and algae blooms in waterways. Think of wild fields as more of collateral damage than as the targets of the excess fertilizer.

There's a wild portulaca that grows around here. It pops up all over my yard. It's a low growing plant, though, and if indiscriminate fertilization made the grasses grow taller than usual, it would be crowded out.

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Additional nutrients to enable rapid growth of the plants that dominate the habitat, blocking the access of small animals vital to sunlight, the researchers found. Consequently, many species disappear from the affected areas. Stricter controls are needed to prevent widespread loss of biodiversity.
Hmmmmm. Good points on both sides. While I do not use commercial fertilizers I see changes in my yard from cultivation not just supplements to the soils. Managed controls need to come at the production level to have a widespread positive impact. In other words the use of chemicals needs to be stopped at production level allowing for more enviornmentally friendly products for use and to eliminate most if not all harmfull chemicals that alter a plant or animals as a means of control. All things good and evil will be effected by any change in environment and therefore anything you do should be considered with caution untill you know the outcome of your actions. Just a thought.

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