This page will take you through the steps of calculating evenness of broad and fine-scale habitat distributions
Diversity, Richness, and Evenness
In ecology, diversity is usually thought of as being composed of richness – the number of kinds of things, and evenness the relative abundance of things. Most commonly these terms are used with reference to species diversity, a concept that includes species richness (the number of species) and species evenness (the relative abundances of the different species). An area with 100 plant species (richness = 100) is considered to be more diverse than an area with only 10 species (richness = 100). But an area with 100 species where each species is reasonably well-represented would also be considered more diverse than an area where 99% percent of the plants are a single species and the other species are all very rare.
Sitecore XP 9.3.0 and SXA 9.3.0 Demo – Habitat Home – Setup Guide December 23, 2019 May 3, 2020 Viet Hoang You're a Sitecore developer and want to know how to implement the website(s) using Sitecore Experience Accelerator 9.3.0 (aka SXA 9.3.0) on Sitecore Experience Platform 9.3 Initial Release (aka Sitecore XP 9.3.0) and following Helix. Conda packages for older versions can installed by explicitly specifying the version, e.g. Conda install habitat-sim=0.1.6 -c conda-forge -c aihabitat. We also provide a nightly conda build for the main branch. However, this should only be used if you need a specific feature not yet in the latest release version.
Similar concepts can be used with reference to the diversity of habitats. Consider landcover in the following two made-up refuges, each of which contain the same four habitat types:
Smoky Pines Wildlife Refuge: 500 ha mud flats, 400 ha wetland, 600 ha deciduous forest, 500 ha scrubland.
Great Auk Wildlife Refuge: 5 ha mudflats, 5 ha wetland, 1960 ha deciduous forest, 20 ha scrubland.
Each of these refuges has a habitat richness of n=4 and each is exactly 2000 ha. But the first refuge contains a roughly equal distribution of the four habitats, whereas the second is almost entirely deciduous forest with only small pieces of the other 3 habitats. One can easily imagine that the first refuge would be more at risk from invasive species than would the second. For this reason, it is important to think of habitat heterogeneity both in terms of the numbers of habitats and the equitability of those habitats. Our analysis will attempt to separate the two.
Calculating Evenness
A number of different metrics are available for calculating evenness (and diversity). We'll use a common index of evenness called Simpson's E. Here's the step-by-step recipe for Simpson's E.
1) First determine the total number of habitats present. For the Smoky Pines Refuge Above, there are 4 habitats.
2) Calculate the proportional representation of each habitat (pi). There are 2000 hectares total, so pmudflats = 500/2000 = 0.25; pwetland = 400/2000 = 0.20, pforest = 600/2000 = 0.30, pscrubland = 500/2000 = 0.25.
3) Square all these proportions (pi's) and sum these squares, i.e. ∑ pi2
For the Smoky Pines refuge, that would be (0.25)2+(0.20)2+(0.30)2+(0.25)2 = 0.255
4) Now take the reciprocal of this, i.e. 1/ ∑ pi2 . Here that would be 1/0.255 = 3.92.
This quantity (1/ ∑ pi2) is known as Simpson's D, and is a measure of diversity. Conceptually, ∑pi2 is an estimate of the probability that any two hectares chosen at random from the reserve will be the same habitat type. So the more habitat types and the more even their distribution (i.e. the greater the diversity), the lower this probability becomes. Taking the reciprocal flips this around so that more diverse areas have a higher value of the index.
5) Now to get evenness (E), we just divide D by the total number of habitats present (which is the maximum possible value for D). E = D/Dmax = 3.92/4 = 0.98. This index ranges from 1/Dmax (in this case 0.25) to 1 (equal distribution of all habitats). 0.98 is very high evenness, which makes sense given that the amounts of each habitat are very similar. For comparison, the evenness (E) of Great Auk refuge turns out to be only 0.26, very close to the minimum.
Using hierarchical data
The landcover data for the actual refuges look like the data above, except that the habitat classifications are hierarchical – that is, there are broader scale classifications and finer scale classifications. To see which of these is more important for predicting plant invasion, we'll calculate habitat richness and evenness at both levels of the hierarchy. Here's a real dataset from the survey.
Refuge Cover Types
Baixar chrome macbook. Vegetation cover types (acres / hectares): acres
Forrest and Woodland:
Evergreen Upland: 0
Evergreen Wetland: 0
Evergreen Desert: 0
Deciduous Upland: 200
Deciduous Wetland: 20
Deciduous Desert: 0
Mixed Evergreen Deciduous Upland: 100
Mixed Evergreen Deciduous Wetland: 0
Mixed Evergreen Deciduous Desert: 0
Plantations, Orchards, Groves: 2
Shrublands and Dwarf Shrublands:
Evergreen Upland: 0
Evergreen Wetland: 0
Evergreen Desert: 0
Deciduous Upland: 0
Deciduous Wetland: 0
Deciduous Desert: 0
Mixed Evergreen Deciduous Upland: 0
Mixed Evergreen Deciduous Wetland: 0
Mixed Evergreen Deciduous Desert: 0
Fruit/Nut, Shrub and Vine: 0
Perennial Grassland:
Upland: 0
Wetland: 0
Desert: 0
Annual Grassland:
Upland: 75
Wetland: 31
Desert: 0
Perennial Forbes:
Upland: 50
Wetland: 31
Desert: 0
Annual Forbes:
Upland: 50
Wetland: 25
Desert: 0
Planted/cultivated grassland or forbes: 1753
Submersed aquatic vegetation: 100
Mud or sand flats: 0
Developed, Industrial, Urban: 5
Open water: 50
Note that the broad scale categories are aligned with the left margin, whereas the fine-scale (within habitat) classifications are indented.
To calculate richness for the broad-scale, look for all the habitat types that have some non-zero acreage. I see this for 1) Forest and Woodlands, 2) Annual Grassland, 3) Perennial Forbes, 4) Annual Forbes, 5) Planted/cultivated grassland, 6) Submersed aquatic vegetation, 7) Developed, and 8) Open Water. That makes 8 habitat types.
Ultracompare 20 00 0 164. For fine-scale richness, count all the total number of habitat types that are represented by summing the indented types and the non-indented habitats which have no finer-scale classification (e.g. Open water and Developed). So, now we count 1) Deciduous Upland Forest, 2) Deciduous Wetland Forest, 3) Mixed Evergreen Deciduous Upland Forest, 4) Plantations, 5) Annual Grassland Upland, 6) Annual Grassland Wetland, 7) Perennial Forbes Upland, 8) Perennial Forbes Wetland, 9) Annual Forbes Upland, 10) Annual Forbes Wetland, 11) Planted, 12) Submersed aquatic, 13) Developed, and 14) Open Water. That makes 14 habitat types.
Now for evenness. If you add up the totals of all the habitat types, you get 2492 acres. In this case, that matches the total refuge size entered by the manager (which is good). But don't necessarily assume this is the case: when calculating evenness, always use the total of all the habitat areas entered rather than the total area given by the manager.
For the broad-scale classification, we'll first calculate the pi's for each habitat
Forest and Woodlands = 200+20+100+2 = 322, 322/2492 = 0.13
Annual Grassland = 75+31= 106, 106/2492 = 0.043
Perennial Forbes = 50+31=81, 81/2492 = 0.033
Annual Forbes = 50+25 = 75, 75/2492 = 0.030
Planted/cultivated grassland = 1753, 1753/2492 = 0.703
Submersed aquatic vegetation = 100, 100/2492 = 0.040
Developed = 5, 5/2492 = 0.0020
Open Water = 50, 50/2492 = 0.020
Now, the sum of all the pi2 = (0.13)2 + (0.043)2 + (0.033)2 + (0.030)2+ 0.703)2+ (0.040)2+ (0.002)2+ (0.020)2 = 0.517.
Take the reciprocal, to get D = 1/0.571 = 1.93
And evenness E = D/Dmax or 1.93/8 = 0.24. Most of the habitat is either cultivated grassland or forest, so this low value seems reasonable.
For the fine-scale classification, we use the same set of steps with the 14 habitats that are represented.
Deciduous Upland Forest = 200, 200/2492 = 0.080
Deciduous Wetland Forest = 20, 20/2492 = 0.0080
Mixed Evergreen Deciduous Upland Forest = 100, 100/2492 = 0.040
Plantations = 2, 2/2492 = 0.00080
Annual Grassland Upland = 75, 75/2492 = 0.030
Annual Grassland Wetland = 31, 31/2492 = 0.0124
Perennial Forbes Upland = 50, 50/2492 = 0.020
Perennial Forbes Wetland = 31, 31/2492 = 0.0124
Habit 101
Annual Forbes Upland = 50, 50/2492 = 0.020
Annual Forbes Wetland = 25, 24/2492 = 0.010
Planted/cultivated grassland = 1753, 1753/2492 = 0.703
Submersed aquatic vegetation = 100, 100/2492 = 0.040
Developed = 5, 5/2492 = 0.0020
Open Water = 50, 50/2492 = 0.020
Summing all the pi2 = (0.080)2 + (0.008)2+(0.040)2 + (0.0008)2 + (0.030)2 + (0.0124)2 + (0.020)2 + (0.0124)2+ (0.020)2+ (0.010)2+ (0.703)2+ (0.040)2 + (0.0020)2 + (0.020)2 = 0.506
So D= 1/0.506 = 1.97 and E = 1.97/14 = 0.14
Comparing the values from the fine-scale to the values for the broad-scale you'll see that the diversity is a little higher but the evenness is lower. By breaking things up, we've added new habitats but generally in small amounts.
Now that you understand all of this, here are some tools that will hopefully make your life much easier:
Excel spreadsheet for calculating habitat richness and evenness (directions are embedded) Tasks 1 0 3 – manage your daily tasks.
And
Example spreadsheet (shows what everything should look like when you've used the spreadsheet successfully)
Habitat 1 0 1
Document Actions
Shared code for the Habitat config system. Includes:
-Micro durable document repository implementation
-File system facade built around SystemWrapper
-Config data DTOs for easy serialization/deserialization
- Newtonsoft.Json(>= 6.0.0 && < 7.0.0)
- SystemWrapper-sn(= 0.5.3)
NuGet packages
This package is not used by any NuGet packages.
GitHub repositories
This package is not used by any popular GitHub repositories.
| Version | Downloads | Last updated |
|---|---|---|
| 1.0.1 | 983 | 5/10/2014 |
| 1.0.0 | 948 | 5/4/2014 |
-Updated tests to use latest Habitat.Core.TestingLibrary
-Fixed Moq version
-Added Path property to DurableMemoryRepository
-Added missing unit tests from old codebase
2014
