This level is made up of herbivores: bacteria, fungi, actinomycetes, nematodes, mites, snails, slugs, earthworms, millipedes, sowbugs and worms. Note that some types of mites are carnivores.
The most productive members of your compost pile's food web are the bacteria, which are chemical decomposers. As a group, they can eat nearly anything. Some are so adaptable that they can use more than a hundred different organic compounds as their source of carbon because of their ability to produce a variety of enzymes. Usually, they can produce the appropriate enzyme to digest whatever material they find themselves on.
Every piece of organic matter you place in the pile is covered with varying amounts of bacteria. As they digest the organic material and break it down into its basic elements, they are also reproducing at an incredible rate. One gram of bacteria can become about 450 grams of bacteria in only three hours.
There are many kinds of specialized bacteria operating in different temperature ranges.
Psychrophilic bacteria work best in temperatures of about 13 degrees C
(55 degrees F), but can stay on the job even in near freezing conditions.
This is why you will notice your compost pile sinking in the winter; these
bacteria are busy breaking down organic matter. As these cooler bacteria go
to work, their activity actually begins to heat up the pile. The increased
temperature creates the ideal conditions for the next type of bacteria to
arrive.
Mesophilic bacteria
work best in temperatures of about 21 degrees C to 32 degrees C (70 degrees
F to 90 degrees F), but can stay on the job in even hotter conditions. The
activity of mesophilic bacteria can heat the pile up to even greater
temperatures of 43 degrees C (110 degrees F).
Thermophilic bacteria become active when the temperature reaches between
40 degrees to 93 degrees C (104 degrees F to 200 degrees F). If you notice
your compost pile steaming in the morning or on a frosty day, it's because
these bacteria are busy at work, decomposing your organic waste. These
bacteria generally last for up to five days, and then the pile begins to
cool.
Actinomycetes
go to work next. These fine, gray-colored strands are a cross between the
bacteria and fungi that often excrete vitamins and antibiotics as they
consume the organic waste in your pile.
Molds
and
fungi
get down to business along with the actinomycetes. Molds are actually a form
of fungi. The presence of mold and fungi usually implies decay, although
some molds are deliberately grown in laboratories for the production of
antibiotics
Snails, slugs, millipedes, sow bugs, pill bugs, mites and
earthworms are the larger invertebrates that shred the plant materials,
creating more surface area for action by the microscopic fungi, bacteria
and actinomycetes, which are in turn eaten by organisms such as mites
and springtails. These creatures all excrete "castings" that are very
dark and fine, and great for your plants.
Snails are terrestrial mollusks, typically having a spirally
coiled shell, broad retractile foot, and distinct head. They generally feed
on living plant material but will attack fresh garbage and plant debris and
will therefore appear in the compost heap.
Slugs are basically snails without the shell. They,
too, feed on living plant material, fresh garbage, and plant debris,
and will also show up in the compost heap.
Millipedes are nonpoisonous arthropods with
cylindrical bodies of 20 to 100 segments, with two pairs of legs per
segment. They feed mainly on decaying plant tissue but will also eat
insect carcasses and excrement.
Sow bugs are fat bodied crustaceans with delicate
plate-like gills along the lower surface of their abdomens which
must be kept moist. They move slowly, grazing on decaying
vegetation.
Pill bugs look similar to sow bugs and also graze
on decaying vegetation, but are more flexible. They can roll
themselves into a ball to protect themselves, which gives them their
common nickname: "roly polys.
Mites are the second most common invertebrate found
in compost. They have eight leg-like jointed appendages. Some can be
seen with the naked eye and others are microscopic. Some scavenge in
leaves, rotten wood, fungi, and other organic debris. Others are
predators and feed on nematodes, eggs, insect larvae, and other
mites and springtails.
Earthworms also arrive at this stage and are
generally welcomed by new composters. As a result of the worm's
well-deserved reputation for being excellent decomposers, many
people think that it's a great idea to add extra worms to their
compost pile. This is unnecessary. Let the worms find their own way
into the pile, when the conditions are right. They prefer the pile
when it is cooler, so adding worms could lead to their quick demise
in a hot, steamy pile.