Discoveries about the diversity and workings of our gut bacteria have come on so thick and fast in the last couple of years, you can hardly open a newspaper or visit a grocery store without encountering the word 'microbiome' or hearing people talk 'probiotics'. This is a scientific revolution equivalent to the transformation of a horse- drawn cart to the automobile.

A pinch of rich topsoil contains tens of millions of bacteria and scientists are working hard to understand what most of them are up to. All plants have a microbiome, a cosmos-like mass of microbes that coats their roots, leaves, shoots, fruits and seeds. Plants can't get the nutrition they need from soil without the help of microbes - particularly bacteria and fungi - which create nitrogen, phosphorous, potassium and other nutrients in a form the plant cells can absorb.

It turns out the complex microbial world in the soil may protect plants much like our gut microbiome protects our bodies. In a classic experiment, researchers grew plants in two types of soil. They sterilized one soil to kill all the microbes and left the other soil unsterilized. Then they introduced a pathogen to each type of soil. Plants grown in the sterilized soil succumbed to the pathogen, while the plants grown in unsterilized soil did fine. Researchers found when pathogens attack a plant, it responds by releasing chemicals into the soil that attract a number of microbial species. As those microbes gather around the plant, they release compounds that kill the pathogen. One can't help but see the parallels between soil immunity and our own immune system.

How can you establish a favorable microbial ecosystem? Just as antibiotics indiscriminately kill both good and bad bacteria in the gut, you should avoid fertilizers, pesticides and herbicides which disrupt soil biology. Incorporate organic matter such as compost and manure to the soil. Use mulch, leaf litter or plantings to cover bare soil. And increase diversity, for a diverse garden is a resilient garden. Whether microbes are multiplying in the soil or going gangbusters in our guts, they are everywhere and will outlive us by an eternity.

Natural soils are thriving with life. They contain an incredible diversity of microscopic bacteria, fungi, viruses and other organisms. A single handful of soil can contain tens of thousands of different species.  

The simplest solution for restoring fertility to the soil is to follow a prebiotic strategy and feed the beneficial microbes. Nature relies on prebiotics; organic matter, compost, and mulch to build fertile soil . 

   Yep, it's dead. The absence of microbes and mycorrhizal fungi make it difficult to establish trees in the city. This has profound implications for human quality of life. 

For more information on the micobiome in soil 

The decline of the conifers and concurrent expansion of hardwoods represents one of the most important distributions of plant life on Earth. Today less than 1% of all plant species are conifers, but they cover 30% of Earth's forested land. Conifers are the largest (giant sequoia), tallest (coast redwood), and oldest (bristlecone pine) living things. They're still here and the dinosaurs are long gone.