Hi Judy! I’m glad you avoid stepping on our decomposers! They truly are magnificent creatures once we realize how much they do for us and how critical their survival is for our own survival.
I think it is a mix of factors that have resulted in patchy vegetation in certain areas on my land, ranging from 1) over-rest to 2) overgrazing, as well as 3) the use of herbicide. I know that this land was left completely untouched for many years after the owner died in the 80s. I’m not sure if he had cows, but I think he at least had goats and a chicken coop when he was alive.
After he passed, the land was left to his daughters, who ignored it for a long time. My neighbor says the grass would grow six feet tall in the summer but be completely dead in the center of the plant because of the lack of grazing. After a while, the daughters allowed some locals to graze their horses here in the summer. I think the horses probably did an ok job keeping the grass from getting overgrown, but they probably contributed to some overgrazing and compaction (horses are one of the worst for compaction because of their size, shape of hoof, and the way they eat). Compaction worsens with bare ground because rain will compact it further. We also had 3 horses here for a short while before I rehomed them all. I tried hard to have a rotational grazing system to end the cycle of over-rest and overgrazing, but I was not able to keep up with it with a full-time job.
Lastly, herbicide. My—perhaps unpopular—opinion is that, if you’re involved in restoration and you’re promoting herbicide in any way, you’re going about it all backwards. All of the chemicals that we (as in society) use, such as herbicide, fungicide, pesticide, chemical fertilizer, etc., KILL the soil microbiota and create an ecological gap that can only be filled with early colonizing species, AKA weeds! Fertilizers give your plant a temporary boost, but kill the biota and therefore you have to keep using the chemicals to get the yield you want. The “Big Ag” chemical companies only exist to make you addicted to their product. The interesting thing is that if the soil has more fungi than bacteria (measured by biomass per gram of soil), the weeds cannot grow because they cannot process the type of nitrogen that fungi create (ammonium). Weeds thrive on the nitrogen that bacteria create (nitrate), and every time we apply chemicals or till, the fungi are affected the most because they take the longest to repair, and thus we are always reverting back to a state that promotes weeds.
How do soil microbes prevent disease? Beneficial soil microbes coat the surfaces of the plant roots as well as the above-ground surfaces of a plant, creating a layer that prevents pests and diseases. Disease-causing organisms will not be able to penetrate the coatings from the beneficials, and therefore even the disease causers exist in the environment, the plant will be resilient to their attempts to take hold.
How do microbes promote nutrient cycling? Plants also produce specific compounds and excrete them out of their roots and other surfaces to attract the particular decomposing species that it wants… those soil microbes mine the nutrients from the parent material and convert them to a bioavailable form, giving your plant nutrients and making it healthy. A healthy plant is much, much less susceptible to pests and diseases.
The decomposers (bacteria and fungi) are absolutely an important piece to that puzzle, but they don’t actually give the nutrients directly to the plant (except for nitrogen-fixing species, but they actually take from the plant first before they start making enough to give back). In order for nutrient cycling to take place, the decomposers have to get eaten by predators, such as nematodes, amoebae, and other protozoa. Through this process, the nutrients are excreted directly next to the plant’s roots through the predatory waste (the Soil Food Web school calls this the “poop loop”).
Sorry for the long, drawn out explanation. I get pretty passionate about soil microbiology! My plan is to track and document the soil microbiota and how it changes through the seasons this summer by looking at it with a microscope this summer on my own land. I would be more than happy to do the same for anyone else in this course.