Colonisation of wasteland

Explain the processes by which wasteland can be colonised by vegetation.

Areas of wasteland in both urban and rural areas such as brownfield sites and derelict buildings can be colonised by vegetation. The first stage of this colonisation is where pioneer species such as mosses and lichens develop. These species can live where there is a very limited moisture and nutrient supply so are always first to colonise an area. 

When the mosses dies, they decay and leave a very simple soil and humus layer. As this process repeats a protosoil is formed and allows seeds from other plants to settle and develop. Dust and more soil builds and stage two begins. This is where species such as Oxford ragwort sow their seeds and germinate in the cracks of walls, pavements and other shaded niches available on the wasteland. As moisture begins to be retained and soil levels increase, larger and much more ruderal and taller plants such as Buddleia also known as the 'butterfly bush' self-sow and begin to develop as the new dominant species.

 

As soils deepen and nutrients from decayed plants increase the soil's fertility, stage three species such as Rosebay Willowherb colonise the wasteland when taller Ragwort and Buddleia die off. This plant spreads via rhizomes which are like horizontal roots and so easily becomes dominant. 

Stage four species such as grasses then colonise as soil enrichment continues and replace the smaller meadow grasses. The are will then take on the appearance of grassland at this stage. In addition, some invasive species such as Japanese Knotweed may be introduced at this time since the nutrient and moisture retention levels are sufficient enough for the species to grow. Should the area be redeveloped in the future, this invasive alien species may cause serious problems. The land has not been previously managed by this stage and so will have enabled the Knotweed to thrive.

The final stage of colonisation is where woody shrubs and trees such as Willow, Laburnum and Bramble replace the previously dominant plants. These stage five species compete effectively and can grow roots into deeper crevices in rock. Thickets of bramble will develop and the previous wasteland will take on less of a derelict appearance. 

pictures sourced from ::

gloucestershirewildlifetrust.co.uk

ipm.ucdavis.edu

languard.co.uk

Local conservation project

Askham Bog, York

Askham Bog in York is a small scale ecological conservation area in the UK. The aim of this conversational project is to encourage local species growth, protect rare species that are local to the area and provide a sustainable community project for the people of York.

The Yorkshire Wildlife Trust runs the conservation area with the help from volunteer "Board Walkers". The requirement of volunteers means that people participating in the upkeep of the conservation plan are educated about both the native and rare species of the area. This is a positive achievement of the scheme in York and increases local knowledge which will promote the recognition of the species being protected in other areas of York.

Another success of the area is that it acts as a pollution barrier to residences that are located close to the adjacent A64 - a major road transporting thousands of cars per day. Pollution levels are lowered because the bog is peat. This means that it is very efficient of 'scrubbing' carbon out of the atmosphere and trapping it as new mosses grow over older mosses that contain the carbon. Carbon can be held for millennium this way if undisturbed thus reducing pollution levels in nearby Woodthorpe and Askham Bryan.

Previous to its existence as a conservation area, Askham Bog was uses as a municipal dumping ground in the earl 20th Century. In 1946 the bog was bought by famous sweet manufacturers Terry and Rowntree and donated to the newly formed Wildlife Trust. This makes the bog the oldest nature reserve of the Trust and after decades of active management of cutting meadows for hay and grazing Exmoor ponies, the bog's biodiversity has been successfully restored. The area now boast the largest colony of gingerbread sedge in England and some of the largest royal ferns to which is a fantastic achievement of the conservation area. The bog is kept base-rich by water draining from the Moraine and attracts rare specie of water beetle, the rare Fen Square-pot and the spectacular Emperor dragonfly.

Since peat bogs only cover 3% of earth, the preservation of one by the Wildlife Trust in York is a fantastic achievement, Because of this, the are is now an SSSI (Site of Special Scientific Interest) which labels the bog as a successful conservation programme and the Trust is now looking to invest even more into the area.

The area has been described as a "Mosaic of fen, woodland and meadow," by the Trust and boasts a collection of "Magnificent royal ferns, rare gingerbread sedge and spectacular displays of water violets." This shows that the Trust feels Askham Bog is a success and is proud of what the area has achieved since 1946.



references ::
www.wildlifetrusts.org/reserves/askham-bog-nature-reserve

pictures located ::
letterfromnorfolk.wordpress.com
ywt.org.uk

The Tropical Equatorial Rainforest

Tropical Equatorial Rainforest

Tropical equatorial rainforests (TER) lie within the tropic of Cancer and Capricorn, for example the Amazon and the Gabon rainforest. They are the most productive ecosystem and rely on insolation, moisture and nutrients to develop. Several vegetation layers (stratification) characterise the TER as well as the tropical climate, latosol soil and a diverse range of animal species.

Soil ::

In an undistrubed biome, the underlying soil will have developed naturally over a long period of time and be in balance with its natural environment. It is a mature soil and its characteristics strongly reflect the climate and vegetation.

A latosol is a zonal soil type associated with the TER. Ferralitisation may occur here which is a process by which bedrock is broken down into clay minerals by chemical weathering. 

The top of the latosol shows a thick humus layer made up of decaying leaves and animals. Nutrients for vegetation come from here thus vegetation has shallow roots. As break down continues a humus layer is created. Many active biota can be found here such as ants and worms.

Eluviation or leaching is common due to the high amount of rainfall and percolation. Mainly the leaching is of silica and dissolved salts. There is a build up of iron and aluminium oxides thus turning the soil red in colour. As silica becomes left behind a yellow tone will be given tot he soil.

Soil begins to get more clay-like further down the horizons. The parent material lies at the bottom where ferralitisation occurs.

Vegetation ::

The emergent layer is the top layer with trees around 30-40m high such as Mahogany and Ebony. The trunks are thin to allow for movement in harsh winds. Evaporation is rapid here since these trees have the most contact with the sun, to cope with this, the trees here have non-drip tip leaves so to retain water instead of lose it. There is nearly continuous cover here and since there is a year round growing season, an evergreen appearance is given to the rainforest. 

The canopy layer is the most productive and absorbs 25% of the available energy. There is a thin nutrient layer in rainforest soil and so deep roots are not required. Therefore buttress roots help to stabilise the tall and slender trees. The trees have huge crowns so to absorb as much sunlight as possible via a larger surface area. Leaves can often become saturated here so leaves have developed drip tip leaves to shed water quickly and efficiently.

The under canopy is where less substantial trees are found that are taller than the shrub layer and are far more tolerant of the shade than those above them. The vegetation here only gets a glimpse of sun and often has interlocking spindly branches that allow lightweight animals to travel along them,. The growth of under storey trees is restricted to several metres below the base of the canopy and so a prominent gap can be seen. 

The shrub layer is made up of woody plants and young trees. The lower layers receive around 10% of the available energy and 1% sunlight thus there is little shrub and forest floor vegetation. However ferns and Pygmy trees may be present. There is a layer of rotting leaves and dead animals called litter. This decomposes quickly (within 6 weeks) due to the humidity. Fungi and decomposers therefore thrive here and create a humus layer that is rich in nutrients. Down here the buttress roots themselves can be seen.

Climate ::

The rainforest has a low dijurnal temperature range. The average temperature being 28 degrees celcius daily falling to around 22 degrees celcius at night. Overlying clouds restrict temperatures to around 32 degrees celcious. Rain falls all year round at the equator becuase of the inter-tropical convergence zone (ITCZ) which dominates the conditions. The ITCZ consists of the NE and SE trade winds which meet and force winds to be uplifted at the equator. Evapotranspiration is rapid die to humid conditions and low pressure above the rainforest. This allows air to be uplifted rapidly and large cumulonimbus clouds form from the condensation. Cumulonimbus clouds are the biggest rain clouds and allow for heavy rainfall.

Vegetation and Animal adaptations ::

A tropical equatorial rainforest, such as the Amazon in Brazil, is home to more than 80% of the world’s population of insects as well as hundreds of species of fauna. Some examples include the Crab spider, Orangutan, Gliding Leaf frog and the Colugo. Their moist and humid climates also contain 750 different species of vegetation per hectare; some examples of flora include pitcher plants, fig trees and orchids.

Each of the above examples has adapted amazingly to life in the jungle. 

Crab spiders and pitcher plants have a symbiotic relationship, in which the crab spider feeds off the

pitcher plant’s own prey and still leaves enough nutrients for the plant itself. The pitcher plant has acclimatised to live within infertile soil conditions by arranging a snare. Its flower has a sticky surface to catch passing insects that are attracted to its brightly coloured petals.  The enzymes within the water-filled pitcher digest trapped insects. The crab spider, having adapted the ability to enter and leave the pitcher via its silk thread, can feed off the dying insects also without taking the whole of the available nutrients provided.

Orchids are epiphytes and grow off the surrounding trees of the rainforest. They have a non-parasitic relationship with their host and intend only to survive with assistance from their host. When the epiphytes are higher up, there is more energy available from the sun and they are more likely to flourish compared to if they were on the forest floor.

Some fungi have a parasitic relationship with their host, for example cordyceps. These deadly fungi grow within a host insect, maybe an ant or and prevent a species from becoming too dominant. They drug the insect from within and control their brain. With an ant, the cordycep forces it to climb high where it shall die attached to a vine of a tree. Spores then grow out of the corpse’s head which help to spread the cordyceps' ability to infect other insects.

Fig trees fruit all year round within the tropical rainforest; they are feeding ground for many species of monkey such as the spider monkey and gibbon. They often have buttress roots to stabilise them since the soil in a rainforest is often lacking sufficient nutrients and so buttress roots help to extend the area over which a tree can absorb nutrients from. 

Pictures sourced from ::

buzzle.com

latosols-rendzinas.wikispaces.com

warrenphotographic.co.uk

carnivorous--plants.com

gorgeouswall.com

tnhsprgteam.blogspot.co.uk

Case Study :: Montserrat

Chances Peak, Montserrat

The volcanic island of Monserrat is located in the Caribbean and is part of a group of islands known as the Lesser Antilles. The country is classed as an LIC (low-income country) with a GDP per capita of $3,400 compared to the UK's GDP per capita of $38,920. The plate boundary where it is situated is known as a destructive plate boundary. This means that two tectonic plates are colliding and that one is sub-ducting under the other. The melting of this sub-ducting plate causes magma to reach the surface in the form of a volcano. At this particular boundary the Atlantic plate is sub-ducting under the Caribbean plate. The volcano here is classified as a composite volcano and so has been built up in layers of cooled ash and magma from previous eruptions. We know that there had not been an eruption in Montserrat for over 500 years and so pressures and tension would have built up. These pressures were released firstly in July 1995. The volcano then catastrophically erupted in April 1997 and the island was at risk of pyroclastic flows and large quantities of ash. 

Montserrat is only 16km long and 10km wide. It was previously home to 12,000 inhabitants, now only 5,000 remain. Many of the young residents chose to stay away when evacuated in April 1996 and this lead to a top heavy population in Montserrat. Many inhabitants moved to parts of America, Antigua and the UK as Montserrat is a British colony. The entire population was forced to move out of the then capital Plymouth as this area was located South-West of the volcano - a prime target for pyroclastic flows. Indeed the south of Montserrat was the worst affected after 1997 and so this preparation method proved successful. 

When the dome of Chances Peak collapsed, millions of cubic metres of ash, tephra and gases ran down the sides of the Soufriere Hills (hills where the volcano was situated). The south of the Island was covered (in some areas of up to 10m) in ash, smothering precious farmland and destroying peoples livelihoods. 

Previous eruptions had left fertile soil behind for the people of Montserrat to farm. An impact of the 1997 eruption was the loss of this farmland thus questioning what would families who remained there do without this land. Since the last eruption was centuries ago, nobody who had experienced the power of the volcano then was alive to help locals deal with the situation. Many thought the volcano was extinct because of the lack of activity and so little attention had been paid to this small island.

In the 500 years since the last eruption the island had been colonised by beautiful woodland and tropical vegetation, making for an attractive site for the rich and famous. Luxurious villas and hotels were home to musicians such as Paul McCartney and The Rolling Stones. Now however, similar villas can be purchased to the North of the island at around a third of their previous price. 

Other impacts of the 1997 eruption included the immediate death of 19 people who were killed in fires as a result of heated pyroclastic flows. There were also a number of burn and inhalation injuries reported and two thirds of houses were covered by ash or destroyed by rock fall. Infrastructure was destroyed along with the capital of Plymouth. The airport and port in Plymouth were closed and valleys became blocked with ash.

The Montserrat Volcano Observatory (MVO) was established in 1995 after it was decided that the volcano was not extinct as previously thought. Scientists here are from the British Geological Survey and the University of the West Indes. This seismic research unit has responsibility for all seismic and volcanic activity in English-speaking eastern Caribbean countries. Ground movements due to magma moving beneath the ground are detected using laser beams and GPS, local earthquakes and dome collapses in addition. Topography of the volcano is frequently re-drawn in order to figure out rate of growth of the volcano. Gas samples are also taken from hot springs surrounding the area in also via Correlation Spectrometers. This centre saved thousands of lives as it successfully predicted the large eruption of 1997. 

Responses to the 1997 eruption included the set up of temporary schools and shelters by the Red Cross. Medical support and food were provided by this NGO and £17m was given in aid from the UK government to pay for water purification systems and building construction. Troops from the British navy and USA came to assist the evacuation process and extra warning systems were set up to contact inhabitants of the volcano's state. 

In the long term, a redevelopment programme to help with the rebuilding of houses, schools, medical centres, infrastructure and agriculture was funded with help from the UK. Plymouth remains an exclusion zone and approximately 5500 people currently live on the island. The island is trying to establish a capital at Little Bay in the North of the island.

Montserrat August 2012 :: useful to see what the island is like in the Plymouth area

https://www.youtube.com/watch?v=FVPo6EM3FKU




Pictures located from ::
www.bgs.ac.uk
www.montserratvolcano.org
www.emeraldtrendsetters.org