Agriculture Reference
In-Depth Information
Fungi
In some forests, the total mass of fungi outweighs the trees! Fungi provide many of the
same services for plants as bacteria. They may be single-celled (such as the yeast that
makes your bread, yogurt, wine and beer), or they may have billions of cells (like in a
mushroom).
A mushroom is the fruit of certain types of fungi, but the majority of mushroom biomass
is actually underground, winding through the soil kind of like a microscopic root. They
form string-like hyphae, many of which join together and form a mycelium. In one minute,
some fungi can grow five times further than a bacterium will travel in its whole life, though
that's still too small for us to see with our naked eye.
Fungi generally eat by excreting digestive enzymes that dissolve their food, which they
then absorb through their cell wall like bacteria. They eat complex organic materials that
most other living things can't easily digest (such as lignin), and they harvest minerals from
rocks that are virtually inaccessible to other organisms until released by the fungi (such as
phosphorus). It's a good thing because plants need this phosphorus, and often can't get it
themselves.
Some fungi form a special relationship with plants and actually attach to the plant root.
Some of them go right inside the root, and even inside the cells of the plant. They are called
mycorrhizal fungi (“myco” means fungus and “rhiza” means root). These fungi are espe-
cially good at harvesting and bringing minerals up to the plant, but they also bring nitrogen
and even water.
Like bacteria, fungi get food in the form of carbohydrates from the plants in exchange
for their services. Sure, some of them such as powdery mildew also eat plants, but in the
big picture this is a good thing. Someone has to eat the unhealthy plants in our garden, and
we sure don't want to. I haven't gone into detail yet about how microorganisms don't like
to eat healthy plants. I'm saving that for later.
Some fungi also eat bacteria, and others eat the microscopic worm-like animals called
nematodes. Some bacteria and some nematodes turn the tables and eat fungi, too. Everyone
has to eat right?
Fungi dominate forest soils. In a grassland, the total biomass of bacteria is more than that
of fungi, or is occasionally even at a 1:1 ratio. In a deciduous forest, by contrast, the fungi
to bacteria ratio may be 10:1 or more, and in a coniferous forest, 100:1 or even 1,000:1.
Knowing that grassland soil is dominated by bacteria and forest soil is dominated by
fungi helps us understand why it isn't always true that a field will eventually become a
forest. Until the soil community changes, the plant community won't change. Where these
two systems come together at the edge of the forest, a drastic change in the soil food web
can occur in as little as a six inch distance. If you have a field that can't seem to grow any-
