Starter Hedgerows are important in farming as they

Starter Hedgerows are important in farming as they act as sites of refuge for beneficial insects, provide protection for the crop from adverse weather conditions and act as wildlife corridors. Farmers are advised to leave strips of land between hedgerows and the crops in the fields to encourage biodiversity. Describe how you would investigate whether leaving strips of land around fields encourages plant biodiversity.

Measuring Biodiversity Species Richness is the number of species found within the habitat Species Evenness is the abundance of individuals in each species Species Richness • Observe habitat • Count different species • Sample using any of the sampling methods • Record results Plant Species Evenness • Random sampling using quadrats • Count the number of plants of each species per unit area (larger plants) or measure % cover (smaller plants

v To study a habitat, you have to count the number of individuals of a species in a given space. v This is known as abundance. v Very difficult to identify and count every organism – this would be time consuming and may damage the habitat. v Small sections of the habitat are studied in detail. v As long as the sample is representative of the habitat, any conclusions drawn from findings will be valid.

B 2 a – Collection and Sample Size Learning Objectives: -To estimate population sizes - To use keys to identify animals and plants Starter: 1. Look at this picture and guess the percentage of the field that is covered by: a) Bluebells b) Poppies 2. Guess the number of ants in this field…

How easy was it to guess? How accurate do you think you were? There are more accurate ways to make estimations… …e. g. quadrats

Three factors need to be considered when using quadrats; v The size of the quadrat to be used – larger species require larger quadrats. Where a species occurs in small groups rather than being evenly distributed, a large number of small quadrats will give more representative results. v The number of sample quadrats to record within the study area – the larger the number of sample quadrats, the more reliable the results. The greater the number of different species present in the area being studied, the greater the number of quadrats required to produce valid results. v The position of each quadrat within the study area – to produce statistically significant results, random sampling must be used.

Random sampling avoids bias in collecting data. Investigating the effects of grazing animals on the species of plants growing in a field v Choose 2 fields close together – minimises soil, climatic and other abiotic differences. v Take random samples at many sites in each field. v Even with the best of intentions, it is difficult to avoid introducing an element of personal bias. v E. g. are you more likely to stand in a dry area than a wet one? v Will you deliberately avoid areas with nettles and sheep droppings?

A better method of random sampling is to; v Lay out two long tape measures at right angles along 2 sides of the study area. v Obtain a series of coordinates by using random numbers taken from a table or generated by a computer. v Place a quadrat at the point of intersection and record the species within it.

v Occasionally, measuring abundance in a systematic manner as opposed to a random manner can be more informative. v A line transect is made up of a string or tape stretched across the ground in a straight line. v Any organism over which the line passes is recorded. v A belt transect is usually a strip, about a metre wide. The second line is placed parallel to the first. v Species occurring within the belt between the lines are recorded.

v Random sampling with quadrats and counting along transects are used to obtain measures of abundance. v Abundance = number of individuals of a species within a given space. v Can be measured in 2 ways; v Frequency - the likelihood of a particular species occurring in a quadrat. v Percentage cover – an estimate of the area within a quadrat that a particular plant species covers.

v To determine species diversity in a habitat using random sampling v To calculate species diversity index

Once the results of your investigation have been recorded a statistical test is required to determine the diversity of the habitat. A diversity index allows us to estimate the variety of living organisms in a particular area. It takes into account species richness and species evenness.

Simpson’s Diversity Index • Stream 1 appears to be more diverse (it has more species than stream 2, it is more species rich). However it has one species of 85 individuals and 15 species of one individual. Stream 2 has more individuals in each group so this stream appears to be the most diverse (it is demonstrating species evenness). No of species Lugworms Stonefly larvae Mayfly larvae Others Stream 1 (100 animals) 16 85 0 0 15 Stream 2 (100 animals) 10 15 28 32 25 • To stop us making the wrong conclusion we can use the Simpson’s Diversity Index! • The formula is: D = 1 – [∑(n/N)2]

Simpson’s Index of Diversity can be quantified by statistical methods, one of which is Simpson’s Index of Diversity: N(N – 1) D = ∑ n(n – 1) N = the total number of organisms of all species n = total number of organisms of a particular species D = diversity index: the probability that two randomly selected individuals will belong to the same species/group. The lowest possible value of D is 1. The larger the value of D, the greater the diversity.

Two fields were compared and investigated to determine their biodiversity. Data is from 200 point quadrats Species Field A Field B Foxtail Grass 80 96 Clover 9 2 Black Medick 22 12 Daisy 13 0 Dandelion 3 2 Self Heal 14 12 Moss 36 26

Field A n n/N Field B (n/N)2 n Foxtail Grass 80 96 Clover 9 2 Black Medick 22 12 Daisy 13 0 Dandelion 3 2 Self Heal 14 12 Moss 36 26 N 177 150 ∑ (n/N)2 1 –[ ∑ (n/N)2] n/N (n/N)2

Field A n n/N Foxtail Grass 80 Clover Field B n n/N 0. 4519 96 0. 6400 9 0. 0508 2 0. 0133 Black Medick 22 0. 1242 12 0. 0800 Daisy 13 0. 0734 0 0. 0000 Dandelion 3 0. 0169 2 0. 0133 Self Heal 14 0. 0790 12 0. 0800 Moss 36 0. 2033 26 0. 1733 N 177 ∑ (n/N)2 1 –[ ∑ (n/N)2] (n/N)2 150 (n/N)2

Field A n n/N Foxtail Grass 80 Clover Field B n n/N 0. 4519 96 0. 6400 9 0. 0508 2 0. 0133 Black Medick 22 0. 1242 12 0. 0800 Daisy 13 0. 0734 0 0. 0000 Dandelion 3 0. 0169 2 0. 0133 Self Heal 14 0. 0790 12 0. 0800 Moss 36 0. 2033 26 0. 1733 N 177 ∑ (n/N)2 1 –[ ∑ (n/N)2] (n/N)2 150 (n/N)2

Field A Field B n n/N (n/N)2 Foxtail Grass 80 0. 4519 0. 2042 96 0. 6400 0. 4096 Clover 9 0. 0508 0. 0025 2 0. 0133 0. 0001 Black Medick 22 0. 1242 0. 0154 12 0. 0800 0. 0064 Daisy 13 0. 0734 0. 0053 0 0. 0000 Dandelion 3 0. 0169 0. 0002 2 0. 0133 0. 0001 Self Heal 14 0. 0790 0. 0062 12 0. 0800 0. 0064 Moss 36 0. 2033 0. 0410 26 0. 1733 0. 0300 N 177 150 ∑ (n/N)2 0. 2748 0. 4520 1 –[ ∑ (n/N)2] 0. 7252 0. 5480

Analysis and Conclusion What is the Simpson’s Diversity Index for Field A and B Read information on pg 199 What do these figures Indicate?

• The Simpson’s Diversity Index for Field A is 0. 7252 and for Field B is 0. 5480. • A high value for Simpson’s Diversity Index indicates a diverse habitat. The closer to 1 the value, the higher the biodiversity and the more stable the habitat. Small changes in one species may not have a large affect on the other species in the habitat. • A low value for Simpson’s Diversity Index indicates a habitat dominated by fewer species. Therefore small changes to the environment may affect one species but because of its dominance in the community the changes to this species may affect the entire habitat. • Field A is more biodiverse than Field B.