Question
I'm currently undertaking a research project investigating the effects of lawn mowing on plant species diversity. My results have shown that an unmanaged (not mowed) lawn has lower species diversity as compared to a managed lawn. I've been trying to think of reasons why this is so.. Do you have any idea why this is so? Thank you :)  

Answer
Hi Marjorie;
I have never conducted a long term analysis, but some reasons I can see for this would be the fact that weeds will eventually crowd out grass and other plants.
If chemical fertilizers are used, they feed weeds as well as grass, and other desirable plants, so that gives the weeds a boost to overrun the grasses, and some weeds will crowd out other, weaker weeds.
You could end up with a field of crabgrass or dandelions, for instance.
The chemicals kill off the beneficial insects, microbes, and nemetodes, so that leaves a clear way for other harmful insects that invade a lawn, to get a head start.
If you follow a chemical program, you will find that diversity.
If you follow an otrganic program, the soil will be richer, and undesirable weeds will die out, and you will have less diversity.
Charlotte