Last season we started a new survey in an attempt to gain an understanding of the biodiversity within various habitats of a regenerative landscape. During this post I'll introduce the garden we carried out the surveys in, overview the habitat types within the garden that we looked at, I'll present the survey protocol, share the results with you from the late Summer Survey and end with some discussion of the survey and results.
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| The Polyculture Project Habitat Survey |
So let's start with what's the point of recording biodiversity in the first place.
Why do we need to record biodiversity in the first place?
Our project mission is to develop and promote practices that can produce food and other resources for humans while enhancing biodiversity. To encourage biodiversity in our gardens, we include a variety of habitat into the landscape design, including native wild habitats (at various stages of succession) and cultivated habitats. The gardens are, essentially, a mosaic of habitat. Seeing as we are looking to enhance biodiversity within our gardens we must have the means to record the diversity within the various habitats. Our aim is to use this information to guide our land management practices specifically in terms of what ratio of land we should dedicate to wild native succession habitats and to what degree we can work within these habitats without disturbing the suitability of the habitat for other organisms i.e without disrupting the biodiversity. Furthermore, we would like to see how our cultivated habitat types i.e annual and perennial polyculture, compare to the wild habitat.
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| Various habitats within our Polyculture Market garden Plot - Aponia (Aquatic habitat not included) See here for this gardens location on our project map. For habitat, description see below |
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| Just a few of the organisms that inhabit our gardens |
For now, I will focus on what I can immediately do and so have aimed to develop a super simple low tech method to survey invertebrate diversity within our garden habitats. The goal of the survey is that it should be simple enough that anyone can use it and that the data collected should be good enough to draw some useful conclusions.
First, an overview of the garden where we are carrying out the Surveys.
Garden Overview
Location: Shipka, Bulgaria, Southeast Europe
Climate: Temperate
Köppen Climate Classification - Dfc borderline Cfb
USDA Hardiness Zone: 5b (conservative) - 7a (risky)
Latitude: 42°
Elevation: 565 m
Average Annual Rainfall: 588.5 mm
Prevailing Wind: NW & NE
Garden Name: Aponia - Polyculture Market Garden
Garden Location on our Project Map - See here
Climate: Temperate
Köppen Climate Classification - Dfc borderline Cfb
USDA Hardiness Zone: 5b (conservative) - 7a (risky)
Latitude: 42°
Elevation: 565 m
Average Annual Rainfall: 588.5 mm
Prevailing Wind: NW & NE
Garden Name: Aponia - Polyculture Market Garden
Garden Location on our Project Map - See here
Within this garden, we have identified a number of pre-existing habitats and have created some habitats. What follows is a description of those habitat types within the garden.
Habitat Types
Habitat types refer to distinctly different regions within an area and in this case, are determined by the composition and age of the plant species within those areas. We have identified 6 habitat types within this garden that fall under the following categories - Wild Habitat, Semi Wild Habitat, Semi Cultivated Habitat, and Cultivated Habitat.
Wild Habitat Type
Late Scrub
Early Scrub
Semi Wild Habitat Type
Mixed Species Meadow
Semi Cultivated Habitat Type
Mixed Species Hedgerow
Cultivated Habitat Type
Perennial Polyculture
Annual Polyculture
Annual Polyculture
It should be noted that the cultivated habitat types as presented above were abandoned horticultural land and were heavily grazed by tethered horses before we started the development of the garden. This land, if left unattended, would succeed to a habitat very similar to the other habitats on the site namely - Mixed Species Meadow to Early Scrub to Late Scrub and would eventually form Woodland. When working with habitat types within your landscape it's important to have a good understanding of the successional pathway of the vegetation in order to properly appreciate the dynamics of the land and the species that inhabit each successional stage. This information will help you manage the land, specifically the potential for biodiversity, properly.
An excellent classification system for habitat type has been developed The UK Habitat Classification and can be downloaded from the bottom of their homepage here. Our classification system follows this broadly but I have made some adaptions to make it more relevant to our polyculture design, implementation, and management strategy.
The map below shows these various habitat types within our 8-year-old Market Garden, Aponia.
Habitat Type Detail
The following information only includes a sample of the diversity of plant species within each habitat for the month that we carried out the survey i.e August. We intend to make a full record of all the species in each habitat across the season (to account for the seasonal succession of annual and ephemeral species) next year during our Polyculture Study 2020 and provide labeled illustrations of the placement of plants within the cultivated habitats.
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Micro habitat
Our garden designs also include a variety of microhabitats such as rock piles, small and large ponds, gravel pathways, stick piles, rotten log piles, helping mats, tree stumps. These are often placed within a variety of habitat types and are not considered in the survey. A survey of our microhabitats will make a good continuation of this study for the future.
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| Micro habitat from the gardens |
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So now let's look at the Survey Design and how we aim to gain a measure of biodiversity within each habitat type.
Our Survey
Each of the 6 habitat types are surveyed for the number of unique species observed in 2 pitfall traps within each habitat type and 10 canopy observations at different locations within each habitat type. These surveys are carried out at the same time every first and second Monday and Tuesday of the months April to September over a period of 3 years.
The time and date - weather conditions (cloud cover - temperature - wind ) and rainfall received since the last survey are all recorded before we start. (rainfall received since the last survey is only recorded for weeks 2 and 3 of each month)
The Pitfall Traps
Two pitfall traps are set within each habitat type. Each trap is labeled for recording purposes. The traps are set on Monday morning, left overnight and emptied onto white trays on Tuesday morning.
The pitfall traps labeled ready to take a position in the habitats.
The number of unique species is counted within each trap and an average of the two traps per habitat is taken to provide the average number of unique species found within each habitat type. After emptying the traps, lids are placed on the jars and the survey is repeated the week after. The below image shows the locations of the traps within each habitat type.
Simon setting a pitfall trap
Shahara Khaleque made a couple of videos that show the habitat types and how we undertake the pitfall traps surveys. You can find part 1 here and part 2 here. Thank you Shahara :)
Canopy Observations
A 50 m trail within each habitat is determined as shown by the red dotted lines in the below image and 10 locations labeled 1-10 are fixed 5 m apart along the trail.
At each location the observer stands and observes within their 2 -3 m field of vision (without turning head) for 2 minutes -1 min standing - 1 min kneeling and records the number of unique species they can see on the plant vegetation and on the ground.
Protocol Invertebrate Survey - Canopy Observations
- Find your starting mark
- Set timer to 2 minutes
- Face the habitat and count the number of different species* within your 2-3 m field of vision without turning head. 1-minute standing and 1-minute kneeling
- After 2 minutes walk to the next mark
- Repeat 2 to 4 until you have completed 10 surveys.
Species you have seen in previous locations are counted again (start new species-count after every change of location)
*Different species = Do not count individuals, count visibly different species, e.g. :
3 black ants and 1 red ant = 2 species
1 big black spider and 1 small black spider, hard to say if it is young/old or male/female = 2 species
1 small spider and 1 big spider that are clearly the same species = 1 species
Flying species: Bypassing flying insects do not count. Insects hovering (to feed on nectar/pollen) or landing in your field of vision do count.
Here is Shahara taking canopy observations in the Early Scrub Habitat
To account for discrepancies between individuals' vision and interpretation of what should be counted as individual species we undertake the canopy survey twice with a different person counting a different habitat and rotate who does which habitat each week.
The data for both surveys are recorded on printed sheets as seen below. If you would like copies of the sheets, contact us via the form at the end of the post.
How we process the data
The data gathered for all of the surveys in each habitat is averaged. For example, in the Late scrub if five unique species were counted in pitfall trap 1 and three unique species counted in trap 2 the total record for pitfall traps in this habitat would be 4. Likewise, if eight species were counted during canopy obs 1 and four species were counted during canopy obs 2 the total record for the canopy observations for this habitat would 6 species.
We then take an average of both the pitfall trap and the canopy surveys within each habitat for the overall species diversity of each habitat type.
Finally, the results from each month are averaged to give us a monthly average of the number of unique species in each habitat and the monthly results are averaged to give a season average for each habitat.
Hope that all makes sense
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The August survey revealed that the Annual Polyculture was the habitat that showed the highest levels of unique invertebrate diversity and that Late Scrub showed the lowest levels of diversity.
Table showing the Number of unique species recorded within each Habitat Type
It's obviously too early to draw any conclusions based on 1 month of surveying but it looks like a promising start for our cultivated habitats. I think a significant part of the reason why invertebrate diversity was higher in the cultivated areas is that they are irrigated at least bi-monthly and water is probably the single most important factor concerning biodiversity especially the ground invertebrates. I expect that the early spring surveys will tell a different story with the abundant rainfall bringing life to the Scrub areas. The mixed-species meadow results were as expected and even without irrigation were teaming with flying insects taking advantage of the pollen and nectar resources on offer.
Shortcomings of the Surveys
Our aim is to keep the survey as simple and replicable as possible without sacrificing the validity of the data. It seems to me that the barriers to entry for the majority of people when carrying out such a survey will be costs, expertise and time. I believe we have certainly addressed the cost and expertise barriers with the design of this survey and have reduced the amount of time needed to carry out the survey to something that is quite manageable providing you have a small team of 4- 6 people that are willing to give 40 minutes or so of their time 12 times a year and you are prepared to co-ordinate the group and process the data. (I've designed the sheets to do the math and punch out the results so all you need to do is enter the data). It's also possible for one person to complete the survey alone but it's almost certainly going to be tedious. Of course, surveying six habitats is not necessary and you could carry out the survey on however many you may have. Let's have a look at the shortcomings of the survey.
Here are the main shortcomings we have identified so far. If you can see more please do let us know and better still provide a solution that fits within the aim of the survey design.
- Perhaps that biggest shortcoming is that we do not gather information about the species. For future surveys we will develop a simple category ID list for i.e ants - bees - winged insect - snail - slug - beetle, etc. based on the most common species in order to have a better understanding of the organisms within each habitat and hopefully to identify how these organisms relate to productive capacity i.e pests, borgs (beneficial organisms), neutrals.
- As we are not identifying the species and have limited knowledge of entomology we may be counting unique species when in fact they are male or female, larvae/adult or at different instar stages. I expect reliable identification apps for invertebrates will be available in the not too distant future, at least for identification to the group level which can be very helpful for our purposes.
- Because we are not using ethanol in the pitfall traps (commonly used to kill what falls in the traps), it's possible that predators may fall in and eat prey species before we can count them.
- The canopy observations do not account for nocturnal invertebrates
- The canopy observations from the habitat types with tall shrubs and trees do not account for invertebrates in the higher canopy. We could use a "beating tray" observation for this but for some of the habitat such as early scrub and hedgerow, it will be difficult to set this up.
- It could be misleading to think that just because some of the wild native habitats have lower invertebrate diversity that it is of lower value as in some cases uniformity of habitat type, although, may not support a wide range of invertebrate diversity could be essential for certain mammals or bird that may only inhabit the area at certain intervals of the year. More study and understanding of how different organisms relate to the habitat type is required before making decisions on altering the habitat.
- Obviously, the biodiversity metric alone cannot be used to signify environmental health. Soil health - water quality - air quality and the productive capacity in terms of meeting human needs and the stability/resiliency of the state should also be considered
I've really enjoyed thinking about this survey and carrying it out and hope that we have managed to at least catch a glimpse of the diversity within our garden habitats and look forward to gathering a full season of data next year and beyond. If you have any suggestions on how we can improve the survey please do let us know and if you would like to try the survey yourself, send us an email and I'll send you the record-keeping templates and protocols. You can find the complete records of the survey along with protocols, maps and habitat types here. You can access the different sheets via the blue tabs at the top of the sheet.
Support Our Project
If you appreciate the work we are doing you can show your support in several ways.
Become a member of the Bloom Room. A $70 annual or $7 per month subscription to our Substack provides you with access to live sessions, design tutorials, a members forum and more, see details here.
Make a purchase of plants or seeds from our Nursery or Online Store
Joining us for one of our Practical Courses or Online Courses
Comment, like, and share our content on social media.
If you appreciate the work we are doing you can show your support in several ways.
Become a member of the Bloom Room. A $70 annual or $7 per month subscription to our Substack provides you with access to live sessions, design tutorials, a members forum and more, see details here.
Make a purchase of plants or seeds from our Nursery or Online Store
Joining us for one of our Practical Courses or Online Courses
Comment, like, and share our content on social media.
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