Soil Animals - Top to Bottom

http://xespok.net/arthropoda/main.php/v/Arachnida/Oribatida/

As much is going on below ground as above. Imagine taking a tree 
and shaking it, collecting everything that falls out. Then try and make sense of each of the creatures and their relationships. That is is the problem we face when we have collected our little soil friends. How do we know what they do and how they relate when we cant see them moving around. Instead we have a pile of dead creatures. Finding way to explore this dilema is the fascination of this area of world. And there is much to be discovered. And there must be many ways to do so. Trees and soil animals probably co-evolved over millions of years. Looking at that relationship helps us work out the conundrums going on below our feet.

Most of the creatures are small - just beyond our eye sight. They are like specs. They have to move round either by burrowing or using pores and some other creatures tunnels. In terms of total weight or biomass, worms equal all the 'mesofauna together; it just there are lots more of the latter smaller creatures....



Starting at the top. You see birds like blackbirds, robins and starlings pecking at the ground. They eat worms and beetles and insect larvae.

See Birds Eye View  Having a healthy soil, rich in little creature, brings these birds in. So the presence of birds is a good sign.


On the Surface ..

Worms

Active non-burrowing worms consume decaying plant residues on the soil surface, They are like the ones in wormeries – specifically red manure earthworms, belonging to a group called epigeic.

Beetles 

From soil sample in decaying tree leaves. this is a (Rove beetles) (More)

Ground beetles

Also round rotting wood and in compost heaps, you see this Carabid 
or this Nebria brevicollis and Rhinocerus beetle 

Sinodenron cylindricum roam over the soil surface looking for quite large prey - slugs & snailscricket nymphsinsect larvae and isopods like woodlice, and even centipedes). Having lots of ground beetles around is a good indicator of healthy soil. They need lots of other creatures to live. From Royal Entomological Society "As the name suggests, many ground beetles spend their time on the ground and few can fly. The fusion of their wing cases (elytra) acts as protecting armour. Both larvae and adults are carnivorous and often specialise in eating slugs and snails, as well as eating a range of carrion. Depending on the ground beetle species, they will also attack aphids and other pest insects. Many ground beetles eat by vomiting on their prey and waiting for their digestive enzymes to make their food more fluid and easier to eat. By encouraging them into your garden you can start on the road to a natural method of pest control. Many ground beetles are nocturnal and need some form of shade during the day. Provide them with shelter such as a log pile, leaf litter or just some large stones...

See 'Beetles' for more

Millipedes 

shred plants  whereas centipedes are carnivores, crawling through worm holes looking for smaller creatures like ants

Ants

From Fundamental of Soil Ecology Coleman, Crossley & Hendrix

Ants in turn feed on oribatid mites(see grazing - more about these mites below)...

Just below the surface ..

Springtails 

3 groups..Is the body long with distinct segments? (if 'yes' go to  2). If 'No'..

1 Symphypleona
 Dicrytomidae and Arrhopalitidae. These round bodied (dynamically good for holding water) springtails are often near the surface and some live on the surface in vegetation, like grass.

2 Is the first thoracic segment visible?. If yes..

Poduromorpha - include snow flea often found on water.
and Onychiurids 


Both feed on bits sloughed off roots...and on mycorrhizal fungal

From Fundamental of Soil Ecology Coleman, Crossley & Hendrix

Soil invertebrates influence microbial populations, and hence indirectly affect total metabolism, by 1. Regulating fungal growth (Warnock et al., 1982; Ulber, 1983; Gochenaur, 1987), 

2. Disseminating fungal and bacterial propagules into new substrates (Visser et al., 1981) or 

3. Reactivating senescent microbial colonies (Hanlon, 1981).

Download pdf for lots more

3. Entomobryomorpha 

Folsomia. 


Folsomia (F.candida) are currently used in laboratory tests for the early detection of soil pollution. Acute and chronic toxicity tests have been performed by researchers, mostly using the parthenogenetic isotomid Folsomia candida.[look at source]
ISO Standard for evaluating toxicity to F.candida in lab conditions, as way to determine soil quality

Plant material, mainly from moss, bracken, pine needles and bark is consumed by enchytraeid and lumbricid worms, sciarid larvae (young fungus gnats) and phthiracarid mites (primitive oribatids). Fungal material (+ or - plant material) is ingested by all groups, like camisiid and oppiid mites, some species of Collembola, sciarid and chironomid larvae

Isotomid springtails and chironomid larvae (adult flies for fishing)consume faecal material like this from oribatids... Oribatid faecal pellets inside pine needle

More on soil animals diets

GOING DOWN..

Worms 

The endogeic earthworms, like L. rubella, pull leaves down into burrows. In soil fauna terms they are like massive earth moving equipment. Earthworm eating plant stem Worms working a field, then themselves

The ones that live deep down belong to the group Anecic, the most famous of which is the earthworm Lumbricus terrestris
Their role as tunnel diggers is vital to many of those creatures we’ve just described. More on identifying worms 

Symphyla

These are related to centipedes, and are their 'living in the dark' cousin. 
They feed directly on plant roots, so can be a pest to crops





Insect larvae

Insect larvae. They are mainly white coloured with many segments and usually a dark head. Like this vine weevil larvae (white brown head), with pupae nearby kicking legs and hatching into adult insect.
eg Bibionid fly larvae
 grow into horrible plagues of these

Leather jackets can be a plague under lawns.

They develop into the familiar daddy long legs.

When leaves fall..  



Proturans 

with virtually no distinguishing features. So much so they weren't discovered till the 20th century. they feed on organic matter released by decay. They are considered the earliest 6-legged creatures to evolve.


Fungi sprout mushrooms which come above ground so we see them at certain times. Fungi, alga and and bacteria work on broken down plant remains coming out of the mites/ worms, turning chemicals like Lignins and cellolose – hard bits, into simpler carbohydrates 

Mites (Key for Mites)

1Oribatids

Worms mangle organic matter but it is the myriad of mites that break down organic matter into v small parcels for fungi and bacteria to act on. The 'mesofauna' break down the leaves – springtails prising apart leaves. But mainly oribatids

The process of 'humification' - turning dead matter into humus, involves many different soil animals. For details see file below 'Humification'
Collembola help prise leaves so small mites can enter and chew dead plant matter, passing it through their systems so better for bacteria to work on. Some also eat algae and fungi. 

Also in the leaf litter are ..

2.Predatory Mites

 Another group of mites – Mesostigmata.have a long proboscis to
feed on nematodes…and yummy springtails (clip form my video). Perhaps they should become the 'Indicator of healthy soils'? Like all great predators - like hawks and buzzards, their presence means there must be prey about - indicating that there are a lot of soil 'bugs' about. 

None of the main soil creatures are 'bugs' in the proper sense of the word - ie belonging to the Order Hemiptera of Insects (like aphids and cicadas). In fact very few insects spend their whole lives underground. This is possibly because insects evolved after mites and springtails, by which time time the soil was pretty well colonised. The key element of classification among insects is their wings. So Hemiptera refers to 'half' (Hemi) wings (Ptera). However wings are no use underground. So did they evolve from other soil arthropods and take flight? Springtails would be most likely ancestors. (New light on oldest insect)

Nematodes 

The third main group of soil mesofauna, alongside springtails and mites, are nematode worms. Pretty boring looking - basically just a sheath covering the guts


See how Nematodes move. Some are directly parasitic on plants but many are bacterivores and fungivores not feeding directly on soil organic matter, but on the bacteria and fungi which have decomposed organic matter



Out of sight..

Protozoa and smallest of all and most numerous.

Fungi
The 'Rhizosphere dynamics' mentioned here indicates the roots and their relationship with bacteria (like nitrogen fixing bacteria - see below) and fungi - particularly Mycorrhiza fungi. These fungi are attached to the root  and take sugars from roots for their own energy and return soluble nutrients in the soil; these will have come as part of the breakdown products of decomposers like oribatids (see below). This is a crucial part of the overall life cycle of the world/earth. It means trees can access mineral nutrients to be fed properly. The fungi also increase the surface area of roots to enable more transfer of chemicals in and out. More

Onychiuridae have the capacity to carry spores of mycorrhizal fungi and mycorrhiza-helper bacteria on their tegument to the roots, so these soil springtails play a positive role in the establishment of plant-fungal symbioses and thus are beneficial to agriculture.[look at source] You could call them 'the bees' of the soil as an indicator of how important they are - and how, like bees, carry out a vital functions, quite accidentally. 

BActeria

Bacteria are tiny, one-celled organisms about (1 µm). A teaspoon of decent soil 100 million - 1 billion bacteria. That is as much mass as two cows per acre. – a tonne.

Bacteria dot the surface of strands

Most are bacteria consume simple carbon compounds, such as root exudates and fresh plant litter, convertingl organic matter into forms useful to the rest of the organisms. Somes can break down pesticides and pollutants in soil. Decomposers prevent the loss of nutrients, such as nitrogen, from the rooting zone.

Bacterial pathogens include Xymomonas and Erwinia species, and species of Agrobacterium that cause gall formation in plants. Chemoautotrophs obtain energy from compounds of nitrogen, sulfur, iron or hydrogen instead of from carbon compounds.

Nitrogen fixing bacteria also live closely with roots. The bacteria invade root hairs and multiply making the nodules (below), where the bacteria convert free nitrogen into nitrates which is like a natural fertiliser for the plant.


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