Losing life’s variety

[tabatha]

Drought inspired the longest-running of the post-treaty wave of biodiversity experiments, says David Tilman of the University of Minnesota in St. Paul. For reasons that had little to do with biodiversity, he and his colleagues were monitoring grassland plots at the university’s Cedar Creek Ecosystem Science Reserve. Then a drought hit.

In looking at the pathetic, shriveled plants, Tilman and his team found that plots with 20 or so species had about half the living matter, or biomass, recorded in the same plots in a normal year. But plots with one or two produced only one-tenth of the biomass of a normal year.

“We actually didn’t believe the results when we first saw them,” Tilman says.

Tweaking the analysis this way and that still produced the same findings. So Tilman set up an experiment as a deliberate test of the effects of species number on biomass. With 168 plots of one to 16 species, the experiment has been running for 16 years. In the early years it led to a paper presenting evidence that yes, under the same conditions, plots with more species of plants eventually tend to yield more biomass than plots with fewer species.

A 2006 paper in Nature by Bradley Cardinale of the University of California, Santa Barbara and his colleagues supports these findings. The team concludes that, overall, tests have shown that greater diversity in systems from grassland plants to rock-hugging marine invertebrates increases the basic productivity of an ecosystem.

What causes that burst of productivity has led to lively debate. Having more species may increase the chances of getting one super-producing plant that plumps up biomass. That scenario, called a sampling effect, could play out in some systems, but Tilman says he thinks his plots are getting an extra boost from the powers of competition. When species crowd into an area, they compete for resources and become efficient at using them.

http://www.sciencenews.org/view/feature/id/56602/title/Losing_life%E2%80%99s_variety

[Warpy]

1. That must be why I was able to get so much food

out of a 10x10 kitchen garden, digging weeds and straw alike back into the ground at the end of the growing season. I never got particularly bent out of shape about weeds, preferring to cut them down and mulch them if they started to get in the way. I do know the heavy clay soil got better every year, although I never got rid of all the wretched rocks that would work their way to the surface after every rain.

The only stuff I used on that garden were wood ashes from the wood heater and fish emulsion (the cats were fun to watch) twice a growing season.

While I never grew space intensive things like sweet corn, I had plenty of bush beans and tomatoes to can every year, plus green peas to freeze.

[YOY]

2. This is what I've got going in my back yard.

http://www.eburgess.com/detail.asp?pid=7593

[kestrel91316]

4. Wouldn't have hurt to put dilute pee on it, either. Just sayin'!

[kestrel91316]

3. No species is an island. Apologies to John Donne.

[XemaSab]

5. It's easy to see how animals co-exist in a diverse ecosystem

and it's fascinating that plants are able to co-exist in the same way, each species exploiting its own niche.

[tabatha]

6. I noticed with plants,

that a whole bunch of different species grow in the same place, but some grow later than others. I wondered about it.