Human affect on plant growth and distribution.

Key words: Distribution: Dispersion or distribution patterns show the spatial relationship between members of a population within a habitat. Growth: Growth is defined as the irreversible increase in the dry mass of an organism. It is brought about by an increase in cell size or number.

The different factors include: Trampling: areas which have been walked on cause plants to grow unevenly; which in turn, leads to an uneven distribution. Habitat destruction: this includes deforestation or clearing of areas for development. Pollution: acid rain can cause the soil to become to acidic, killing the plants and/or inhibiting the growth of others. Use of chemicals: can affect the growth and distribution of plants, which can reduce biodiversity. Monocultures: this is the growth of single type of plant, which repeatedly depletes the soil of the same mineral; which are crucial for healthy growth.

Pollution Humans, commercial and industrial activities lead to air pollution, which has drastic effects on both plants and animals. Air pollution leads to losses in crops, trees, vegetation and ornamental plants. Other symptoms include mottling, bronzing, reddening and stunted growth. When sulfur dioxide and nitrogen oxides combine with water in the atmosphere, they form acid rain, which intoxicates the soil and waters where it falls, causing damage to plants.

Pollution and the causes: Acid rain forms because of atmospheric sulfur dioxide and nitrogen dioxide, which are emitted from natural and human-made sources. These include volcanic activity and burning fossil fuels. These compounds interact with common atmospheric chemicals, including hydrogen and oxygen, to form sulfuric and nitric acids in the air.

How pollution affects plants: Acid rain weakens trees by destroying their leaves, decreasing the nutrients available to them. The toxic substances released from the soil also poisons the plants. Acid water dissolves nutrients and other important minerals in the soil and washes them away before they can be consumed by plants. Additionally, Ozone holes in the upper atmosphere allow excessive infiltration of ultraviolet radiation from the sun to the Earth causing harm to plants. Similarly, Ozone in the lower atmosphere prevents plant respiration by clogging stomata and hinders plant’s photosynthesis rates, hence stunting the plant's ability to grow.

The affects can be seen: Through foliage develops injuries that, with time, appear as necrotic lesions. Yellowing of leaves (chlorosis) may also be an effect of acidification. Other symptoms include mottling, bronzing, reddening and stunted growth.

Chemicals (herbicides) Several different terms are used to describe the actions of weed killers, and these may overlap. Nonselective herbicides destroy or prevent plant life in general regardless of species. Selective Herbicides are more toxic to some species than to others. Broadleaf herbicides are effective against broadleaf (dicot) plants, and are not generally effective against weedy grasses (monocots). They are often used in lawns. Grass herbicides kill grassy (monocot) plants, and usually do not kill broadleaf plants.

Plan: method 1. Place the gridded quadrat on the ground. 2. For each plant count the number of squares the plant is found in. Use the Playing Field Plants chart to help you to find out the names of plants you find. 3. Use a metre rule to measure the height at rest of the highest plant in the quadrat. 4. To measure soil hardness (a) Hold a metal pin at arm’s length above the quadrat and let it fall through you fingers. (b) Measure the depth of entry into the soil. Makes sure the same person takes all the soil hardness measurements. Be careful to hold the metal pin at the same height each time.