One of the nicest things about blogging is that sometimes you get unexpected contacts with knowledgeable readers. In June of 2004 I found an interesting blurb about a paper, but didn't have access to the paper itself. Still, I posted about it and lamented lack of access. One of the authors read the post and sent me a copy for personal use.

That old post, Biotope Space, discussed one of the important reasons why polycultures are so productive.

Using diverse plant mixtures instead of monocultures can increase yield and other ecosystem goods and services on which humans depend. Recent studies showed that such beneficial effects of biodiversity depend on complementarity between species in resource use, as is the case if species root in different soil depths. This knowledge led to the further hypothesis that the biotope space, for example the soil volume in which species can root, should also matter. With increasing biotope space more species occupying different niches can be "packed" into the environment. Therefore, complementarity and beneficial biodiversity effects should increase.

Their paper demonstrated that this is so. The biotope space, the physical space associated with a species' niche, varies by species and so allows niche complementarity between species. For example, some are deeper rooted than others, allowing two species to stand side by side drawing water and nutrients from different soil levels, and so both thrive where they would compete if they were the same species.

The paper was especially interesting since the experiment used 10 grassland species. Some were short, some were tall, some were deep rooted perennials, some were shallower rooted annuals, some were nitrogen fixers and others not. This is a common mix, understated if anything. My pastures have many, many more species, and the mix varies seasonally. It's a trial to name them all, and some remain mysterious to me. To make it worse (or better) I plant stuff too. I carry a small bag of seeds and if I find bare dirt I scrape the dung off my boots on that spot and drop a few seeds.

I carry different seeds at different times of the year. This is important since different species and different cultivars of the same species grow at different times. It further increases sward productivity. My focus for a couple of years has been on winter active species, those that don't go dormant when it is cold and the days are short. At my latitude and altitude I can grow grasses year round if I have a good mix. It seldom freezes or snows. Right now my pastures still produce though most of my neighbors have brown swards of dormant grasses. They don't produce as well as when the days are long, but the forage I produce in the dead of winter is valuable. It reduces the amount of stored forage needed to support my herd, or said another way, it raises my stocking rate. I produce more per acre over the year. With the same land area and inputs I get more production. Seeds, though expensive, are cheaper than bought hay. It pencils.

I think there is tremendous opportunity. That may be one of the few benefits of the current bio-fuel craze. Researchers and breeders may put more effort into developing more productive cultivars intended to be grown in polyculture. Mixed use as well as mixed species may support food and fuel production on the same swards. Multi-species grazing on multi-species swards with seasonal excesses harvested for cellulosic bio-fuel production could greatly increase productivity. Said another way, it could reduce the land area needed, leaving more wild lands, to support a growing population hungry for energy as well as food.