Habitats: Forest-floor

Geetha Iyer

Descriptions about forests generally revolve around what trees are to be found within, what kinds of animals and plants reside and about what type of forests they are. But within the forests exist habitats, micro-habitats and niches that play an important role in maintaining the characteristics of the forest. However, it is the population of large mammals found in the forests that one often learns about while discussing a forest. In this article, I bring to your attention some of the habitats within the forests that have a significant role to play in harbouring biodiversity.

Trees being the point of reference for a forest, the types of trees present, their growth and abundance take centre stage in most descriptions. In a tropical evergreen forest or a rainforest, where there are abundant and well-established trees towering in height, well-differentiated areas based on their location vis-à-vis the height of the trees are habitats each supporting a community of diverse flora and fauna. Beginning from the ground, there is the forest floor followed by the herb layer, shrub layer, understory of the forest, canopy to end in the emergent layer. Each of these layers have their own unique fauna species that cannot exist in other layers, thereby establishing an ecosystem therein. This article focusses on the forest floor habitat found in different types of forests.

Forest floor: As the name indicates this is the part of the forest we walk on, with the soil beneath our boots. Their abiotic composition is determined by a number of factors with sunlight, temperature and humidity playing significant roles, in turn influencing the fauna and flora adapted to these conditions.

In an established rainforest or a tropical evergreen forest, sunlight barely reaches the forest floor. It is littered with organic matter – remains of flowers, fruits, seeds, food remains and faecal matters of animals. This is where the decomposers of a food chain are active, feeding on these remains of plant parts, excreta, etc., to build the soil. Different types of fungi are common here. They are also the places where invertebrates are abundant, be they insects like termites, ants, beetles, or others such as millipedes, worms, etc. These in turn attract vertebrates such as anteaters, wild pigs, rodents, frogs, reptiles, etc. Other than microorganisms and fungi, several species of invertebrates such as termites, millipedes and worms help in decomposition of organic matter either directly or indirectly. Giant centipedes, spiders, scorpions and burrowing worms also live here. Forest floors may have small streams flowing nearby, thereby creating diverse micro-habitats that allow a multitude of organisms especially several semi-aquatic and aquatic insects, amphibians such as caecilians and frogs, larvae of fish among other aquatic organisms, to flourish. A few examples of wet evergreen forests – forests in the states of Assam, Arunachal Pradesh or Meghalaya in the north and in Kerala, southern Tamil Nadu and Karnataka in the south.

Forest floors of a temperate evergreen forest present a different diversity due to the difference in the climatic conditions influencing the flora found here. Temperate forests are found in higher altitude areas, between tropical and boreal regions. There is a marked difference in temperatures and the annual rainfall ranges between 50-150 cm, unlike tropical evergreen forests where it is more than 200cm. Temperate evergreen forests could be either broad leaved forests (situated at a lower altitude), coniferous, with needle shaped leaves (at a higher altitude) or a mix of both. These evergreen forests can be seen in the Western and Eastern Himalayas, such as in the hills of West Bengal, Assam, Arunachal Pradesh, Sikkim, Nagaland in the north and higher hilly regions of Tamil Nadu and Kerala in the south. Oak species are in abundance in the broad-leaved forests, as arecedar, chestnut, birch, etc. Cinnamomum camphora from which camphor is produced is found in these forests. The coniferous forests are populated with blue-pines, hemlock, firs and spruces. A mixed forest would generally have a mix of the two kinds, predominantly cedars, pines, hemlock, etc.

More than 50 species of rhododendrons are found in the temperate forests of Sikkim. Biotic components in these forest floors differ from those in wet evergreen forests. Sunlight, higher temperature, differing humidity and availability of light are factors that allow flowering flora to be present, in turn different kinds of faunal species to thrive. Ferns, mosses, shrubs and herbs that produce berries are common on the forest floor. Presence of flowering plants brings pollinating insects and birds to this habitat. Food availability being more, mammals, birds, snakes, lizards and burrowing vertebrates are common; the invertebrate species though may also have the same members described above, the species found here, for example, of millipedes, termites or worms would be different due to the difference in the abiotic factors.

A few years ago, two new species of Cinnamomum – C mathewianum and C agasthyamalayanum were discovered from Southern Western ghats of Kerala, the latter from the Agasthyamalai Biosphere reserve. The leaves and stem of this species have a strong smell of camphor leading researchers to believe that camphor could perhaps be extracted. Several species of Cinnamomum are found in the forests of Southern Western Ghats.

Moist deciduous forests at a casual glance may appear to look like evergreen forests. However, a closer observation of tree species will help differentiate between the two. When these forests occur along with trees that are typical to an evergreen forest, then such forests are also described as semi-evergreen forests. Monsoon forest is another name used to refer to them. Annual rainfall here can occur upto 200cm. Deciduous trees shed leaves thereby allowing for a lot more sunlight to penetrate the various levels and reach the forest floor. Thus, it hosts within it a large diversity of flora and fauna. Some familiar and commonly found trees here are various species of Terminalia, Lagerstroemia, Dalbergia, Dillenia, Pterocarpus, Grewia, etc. Teak and sal trees as wellas bamboo are common both in moist and dry deciduous forests. These forests provide us with several products such as kadukai or Indian hog plum, gooseberry, jamun, etc.

Forest floor is diverse in flowering plants; climbers with thick woody stems – referred to as lianas – are common in these forests. Different species of bracket fungi may be seen inhabiting fallen tree trunks. The fallen tree trunk in fact provides a habitat for a wide variety of species, from orchids to ants, beetles, burrowing worms, planaria, etc. A wide diversity of insects may be observed on the forest floor. Butterflies, day-flying moths, bugs, larvae of neuropteran insects; millipedes and centipedes, snails and slugs, worms, planaria are some examples of invertebrates that may be found at the ground level. Vertebrates’ diversity is good too. Insectivorous birds, ground feeders, diverse reptile species and ground dwelling mammals are common. One of the endemic mammal species that resides in the monsoon forests of southern western ghats, in the canopy region is the Lion-tailed Macaque. The hydro-electric project planned in Silent Valley, Kerala, was aborted in order to protect this highly endangered species.

Dry deciduous forests as the name indicates occur in regions with prolonged dry season and low precipitation. Quite widespread in India, these may be seen in the rain shadow regions of eastern ghats, southern Deccan plateau and regions in Bihar, Jharkhand, Chattisgarh, Madhya Pradesh to name a few. The Nagarjunasagar-Srisailam Tiger Reserve in Andhra Pradesh represents a typical habitat in the eastern ghats. Gir National Park is one of the best examples of dry deciduous forests in the western part of India.

Whereas the forests in central Deccan plateau are dominated by Hardwickia, Acacia, teak, neem, palash, peepal, wood apple, etc., are also quite common. When the trees have shed their leaves, the forests present an appearance of scrub and grassland. Fire hazards are high in these forests. Some plants in these regions are seen to possess thorns and prickles. Climbers are quite common as the trunks of the trees here are quite thick and provide a firm support for them.

Dry deciduous forests are rich in bird fauna. The grey hornbill is common in these forests. Among the rare species of birds found here is the Jerdon’s courser.

Diverse small mammal fauna such as leopard cat, jungle cat, striped hyena, barking deer, jackal, flying squirrel, etc., reside here. The mammals, reptiles and other vertebrates that live here have to adapt to the low availability of water in the dry months. Thus, seasonal migration, hibernation, nocturnal activity are some of the ways by which animals overcome adverse conditions.

One needs to remember that the demarcation of forests into evergreen, deciduous is not firm or inviolate. These forests often flow from one kind to another. Thus there will be some regions where it will be hard to claim forests as one or the other kind. It is for this reason that classification of forests done based on the altitude and latitude into tropical, temperate or boreal is a more defined approach than based on climatic conditions. However, be they temperate or tropical, the kinds of forests I have described above exist in these regions and the forest floor in each of them sustains unique flora and fauna.

The forest floors may not often give you direct sightings of flora and fauna, but there are plenty of clues that will help you learn what animals and plants live there. Plant parts, especially seeds and fruits are a great way of knowing the flora of the region. Scats, dungs or faecal remains of animals are clues to knowing which animal was there and sometimes even when. Feathers on the forest floor will help you know about the presence of birds.

Given here are the droppings (scats/dungs) of several animals seen on the forest floor. Use them when you visit the forest next to find out whether the animals are found there or not.

Activity – Scatology – Tips to teachers
Take a printout of the images and exhibit them on your class display board for at least a week before your outing to the forest.

Ask students to make a sketch of each image. This will help them pay attention to small details important for identification.

When you see the droppings in the forests, take some measurements – of length, width or mass. These details help researchers to calculate the age or health of the animals. Animal droppings are food for several creatures such as dung beetles, flies, and butterflies sip minerals from them.

Do you know?

1. Scatology is the science of study of faeces.
2. Dung coffee: Civet coffee is the most expensive coffee in the world. It is produced from the half-digested coffee beans found in the dung of civets. The civet’s faeces are collected, the beans from them removed and cleaned and used for making coffee powder. In India this kind of coffee is produced in Coorg.
3. Coprophagy is the consumption of faeces, as dung beetles or rabbits do.

Once the droppings have been observed, a discussion can take place to understand more about the animals. A few discussion questions are given below:

1. What are the biological and ecological data, one can know from dung (scat/dropping)? Hint: species present, diet, territory, behaviour, etc.
2. Can scat data help in conservation? How?
3. What is coprophagy? Construct a coprophagous food chain likely to be found in forests. What is the significance of this kind of food chain, in a forest?

References
• https://www.wildlifetrusts.org/wildlife/how-identify/identify-poo – Guide to identify animal droppings.
• https://tspace.library.utoronto.ca/html/1807/21358/oc03014.html – Data one can gain from mammalian dung.

The author is a consultant for science and environment education. She can be reached at scopsowl@gmail.com.