Random Sampling 
Each element within the subject matter (within statistics this is called a population) has an equal chance of being selected. The selection of any individual is totally independent of any other selected, or non-selected, individual.
The use of random numbers tables can assist in selecting which individual is to be included in a survey. Excel has the ability to produce random number tables.
If, for example, you had an area of 10,000m² (one hectare) with low growing vegetation and wanted to use the quadrat sampling technique. On the assumption you weren't going to use a 1m x 1m quadra
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Reduction
The loss of an oxygen molecule from a mineral and which can make it become more stable. This can also commonly result in a less red soil, as ferric oxide is converted to ferrous oxide. This is the reverse of Oxidation.
Relative Growth Rate
The quantity of plant growth which takes place over a defined amount of time for a defined quantity of vegetation. It is usually measured as growth in dry mass in relation to the current dry mass, for example increase in grams / existing mass of grams in 24 hours. A high relative growth rate is an indication of a plant's ability to more rapidly utilise a range of resources, e.g water, nutrients and light in particular.
Relative Humidity
The amount of water vapour within the air. It is expressed as a percentage of its closeness to the air being saturated. For example, where air is fully saturated it is said to be at 100% relative humidity. Lower temperatures will typically result in a rise in relative humidity because the air cannot hold as much water vapour when compared with higher temperatures. See also Dew Point.
Residual Wetting Agent
A substance which reduces surface tension within a soil profile and persists for a longer period of time than a penetrant wetting agent. These are often used as wetting agents as part of routine maintenance practices, helping to maintain a balance between water retention and water removal from a soil profile.
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Resilience
This can have several interpretations and can also be termed Resiliency.
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Resistant
Something which is less likely to be influenced or affected by an external condition. For example, some grass species are more resistant to football type wear than others.
Resources [2]
In the science of ecology resources which are consumed and depleted, so resources in this context will be nutrients (food resources), especially N, P and K (which will typically be supplied to turfgrass swards by the application of a fertiliser), but also other macro-nutrients and micro-nutrients, many of which will be steadily released into a soil solution through weathering of the soil mineral material.
Light is an essential energy resource for green plants, being consumed to build carbohydrates for growth. This resource can be enhanced and extended over the winter period by supplementa
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Resources [3]
Environmental focused aspects such as soil nutrients, light, water, temperature, relative humidity, or air flow.
Rhizoid
A very small and short root like feature of mosses and algae.