Introduction: what grassland habitats are found in urban areas?

Lawns and urban squares

These grassy areas are generally quite small. Boundary fences, buildings, hedges, trees and shrubs may affect the whole area, making the environment more sheltered and less varied.

However variation in the plant community may still occur however, for example due to the presence of trees or shrubs. There may also be trampled areas where people sit or children play and where trackways lead across the grass. Street lights may have an effect, particularly in urban squares.

Playing fields

The area of grass is often extensive and you may see differences due to variation in climatic conditions. Open areas will be much more exposed to extremes of climatic conditions than areas sheltered by boundary fences, hedges or buildings.

A school playing field showing an exposed open area and a sheltered boundary

A trampled area around the goalmouth of a football pitch

Isolated trees affect local climatic and soil conditions, but may also form a focal point where people gather, so changes in soil conditions due to trampling may be a factor. On playing pitches there is also often variation in the amounts of trampling.

Fieldwork: what abiotic factors could you investigate?

It is possible to plan a fieldwork investigation which compares the plant communities between two or more different areas of grassland or along an environmental gradient. The tables below describe those abiotic (non-living) factors that are reasonably easy to measure and that may be affected by the differences discussed above. Remember that:

• the success or failure of species is often related to abiotic conditions over a period of time. Try to think how the factors you are measuring might change throughout the year
  
• try to measure climatic conditions as close to the plants as possible. You may need to think about the microhabitat.

The effects of abiotic (non-living) factors are of course closely linked to biotic factors, in particular to human management and activity. Click for more information about the influence of these biotic factors, in particular mowing and trampling.

Measuring soil conditions

Factor	What to measure	Variation due to:
Water content Directly affects plant growth and other biological soil processes e.g. decomposition	Field moisture content The total soil moisture at a given moment. Some of this water drains away as soil dries and is not available to plants but measurement can provide useful comparative data	Changes in soil structure, climatic conditions, artificial irrigation and vegetation cover
	Infiltration rate : the rate at which water enters the soil	Changes in soil structure, soil water content and vegetation cover
Soil depth	Distance from the soil surface to the bedrock below: only useful on shallow soils e.g. on chalk	Factors that cause compaction e.g. mechanical rolling and trampling
Soil penetration	The depth penetrated by a weighted pin, dropped from a set height
Soil pH Directly affects plant growth as well as the availability of mineral salts	Acidity or alkalinity of the soil: small differences can be important to plants but may be difficult to detect without sophisticated equipment	Use of chemicals, e.g. fertilisers; use of materials e.g. limestone chippings for pathways; closeness to bonfire sites

Measuring climatic conditions

Factor	What to measure	Causes of variation:
Light: directly affects plant growth but also temperature and relative humidity	Data can be difficult to interpret (see Comparing shaded and unshaded woodland) Also considering measuring: - amount of shade - under trees - canopy cover	Prevailing weather conditions The closeness of trees and other plants, buildings, street lamps and other human artefacts Moss growing on a lawn, shaded by trees and buildings. Is relative humidity high here?
Rainfall: affects soil moisture and relative humidity	Amount of rain over a set period of time. Long term data particularly useful
Temperature: influences plant growth directly, also affects relative humidity	Air temperature. Long term data most useful Maximum and minimum temperatures often
Relative humidity: Particularly important to plants such as algae, mosses and liverworts.	Relative humidity of air: consider microhabitat measurements
Wind: affects temperature and relative humidity. May cause direct physical damage to plants	Wind speed Wind direction