Introduction to Mangroves:
Mangroves are aquatic plants that are usually found on a beach in the intertidal zone (the area between high and low tide lines).
Some live below the tide line and their roots are always in water. This sort of environment would be unsuitable for most plants because of the flooding at high tide and water logging in the roots but mangroves have developed unusual root systems which allow them to live in the harsh conditions.
Habitat:
Mangroves live in tropical and subtropical areas all over the world in places like Australia, where over 30 different species live, Florida, where mangrove swamps can cover as much as 400,000 acres of land and in Asia where there are even larger swamps. Most mangroves are short but some can grow as tall as 12 meters.
Part in the environment:
Mangroves play an important part in their environment. They help to protect coastal areas from erosion throughout storms. They are home to hundreds of species of animals (like fish, crabs, shrimp and other organisms).
Their leaves fall off into the water and decay, which forms a layer of nutritious debris. This layer is a food source for many small animals, fungi and bacteria.
Destruction of habitat:
In the past few years mangrove swamps throughout the world have been disappearing. This is mostly due to human actions. Large areas of mangrove swamps have been cleared to make ponds used for farming of marine shrimp. The swamps have also been destroyed for public leisure, industrial development, to create areas where salt is produced, firewood and even charcoal. New laws have been introduced to protect mangroves in most countries with mangrove swamps.
How Oxygen Gets to Their Root Tissue:
Mangroves live in conditions where their roots are under salt water, most of or all of the time. Unlike most plants which would not survive in these conditions, the mangroves have developed a unique an effective root system to help them adapt to their environment. Most mangroves have more of the plant below the ground than above it, but generally the roots stick to the top 2 meters of soil where the earth is more aerated. But the little oxygen in the aerated soil is not enough for the mangrove to survive so some mangroves raise parts of their roots above the soil, these are called pnuematophores. These roots are covered in special breathing cells which can take in oxygen for the plant. The roots grow vertically upwards to avoid getting buried in the build up of sediment. The roots allow for the transport of oxygen to the underground roots.
Other types of mangroves, like red mangroves, have prop roots, extending from the trunk or even the branches. These roots are exposed to the air in low tide and can draw in oxygen which is then transported to the rest of the underground root tissue.
Mangrove Roots can be very extensive, for example, in Botany Bay, near Sydney, live pnuematophores of a mangrove have been found 28 meters away from the base of the tree.
Introduction to Water Lilies:
Water lilies are water plants which grow all over the world. They belong to the Nymphaeacae (nim-fee-AE-see-ee) family. Most water lilies are perennial, this means that they appear once each year from fleshy underwater stems. The stems, which are called rhizomes, are buried in the mud of shallow waters and they send up long thin stalks to the surface. Water lilies grow large, flat, rounded, wax-coated leaves, the leaves float on the surface and are so strong that some small insects and birds can actually walk across them. The flower of the water lily usually either floats on top of the water like the leaves or is propped up above the surface on long stalks. The flowers of water lilies are unique and beautiful, usually brightly coloured with intricate petals. The stems of the water lily contain air chambers which help them float. In the winter, when it’s cold, the stems and leaves die away but the roots and rhizomes remain buried in the mud.
Habitat:
Water lilies live in shallow temperate and tropical freshwaters, usually at depths of 2m or less. They can only grow in still or slowly flowing waters because of their large size and long sprawling stems which could be easily damaged or tangled in strong currents.
Part in the environment:
Water lilies are important in the environment, they provide food for many animals and shelter for young fish. Whilst the lilies can be good for the environment, they can also be hazardous in large quantities. The lilies can grow so fast and strongly that they can easily clog drainage and irrigation ditches and the smaller flow can cause waterways to silt up and become blocked.
How Oxygen gets to their root tissue:
Water lilies have deep roots and to survive being waterlogged, they use a heat pump to improve their oxygen supply. Their roots have especially large air channels which let oxygen diffuse down from the leaves above. The network of internal air spaces through the water lily has a pressurized flow-through system which forces oxygen to the roots and rhizomes buried in the anaerobic (without any supply of free oxygen) mud. Some water lilies use thermal transpiration (movement of water due to changes in temperature) to supply oxygen to their roots. The air moves down the petioles (the thin stem of the leaf) of young leaves to the rhizome, this flow of oxygen forces a simultaneous flow of carbon dioxide up through the petioles of older leaves and out into the atmosphere. The oxygen which is now in the roots can be diffused into the sediment around them to aerate the mud.
Introduction to River Red Gums:
River red gums are the most widely distributed trees in Australia, with big forests located on the Murray River. The largest forest is on some floodplains in NSW and covers 70,000 hectares. They grow along the banks of rivers and survive flooding and water logging regularly. Although the gums are used to being water logged they cannot survive standing in water on a permanent basis. They can live to be 500-1000 years old very tall.
Part in the Environment:
River Red Gums provide a home for many animals and insects such as aphids, ants, bees, birds, bats, caterpillars, spiders, beetles, cockroaches and lizards. These magnificent trees also help to keep the water table down which minimizes salinity problems.
History:
The early European settlers used the strong wood of the river red gums to build slab huts, bridges, carts, joinery, wharves, fencing, railways and as fuel for steam boats . Before the Europeans came, Aboriginals used the bark to make shields and canoes.
How Oxygen Gets To Their Root Tissue:
The River Red Gums have adapted to their habitat in a few different ways.
Firstly, they have developed the ability to take in oxygen through the trunk, this is handy when their roots are water logged and they still need oxygen to respire.
They also create floating root masses to extract oxygen from the air during floods. The Gums shed their leaves more than most other plants because reduced leaf area means less water is needed in times of moisture stress. Seedlings develop resilience early, they grow long deep roots to deal with starvation resulting from being underwater, although complete immersion, unless for only a short period of time will kill seedlings. As the trees grow older they become better at surviving water logging. At two months old, seedlings can survive water logging for one month while older saplings can survive 4-6 months of water logging by shedding some of their leaves.