Rangelands invertebrate pitfall trap survey

KEY DETAILS

Principal Investigator
Bjoern Matthies
Date
30 October 2024
Version
0.1.2
Programme
Rangelands Biodiversity Project (RBP)
Study Site
Lewa-Lolldaiga-Borana-Ngare Ndare (LLBN)
Key partners
University of Liverpool
Contact email
b.matthies@liverpool.ac.uk; kate.parr@liverpool.ac.uk

1. PREAMBLE

Natural State’s objectives and activities are detailed by a set of accepted Standard Operating Procedures (SOPs). These documents describe the steps involved in all Natural State projects, from data collection to data processing and storage. Each SOP documents key project details and provides methodological details specific to the project. The objectives and background of the project, features of the study area, and details on survey and sampling design may be found in the project Design Document (DD) which is available in the Related Documents section below.

1.1 SOP PURPOSE

To provide a clear step by step guide to the methods implemented in the project, therefore allowing for consistency in data collection and repeatability of all steps involved in a project’s data collection, processing and storage. This is crucial to Natural State’s mission of facilitating nature restoration at scale by using the latest technology and methods to revolutionise impact monitoring for carbon, biodiversity and human well-being.

1.2 SOP SCOPE

This document details how this project will be implemented. All methodological steps are explained, and the principal team members overseeing the project are listed in case further clarification is required. It also further directs readers to where they can find additional information relevant to the project. This document is intended to be printed out and taken to the field for reference sake.

2. GLOSSARY

BACI
Before-After Control-Impact survey design
CPP
Carbon Pool Plot. A 50m X 50m sampling site within which NS measures aboveground and belowground carbon stocks.
Deployment
The period of time a single remote sensor is active within the environment at a single, defined station as part of a survey.
GEM
Global Ecological Monitoring. A global biological research project to measure ecological processes.
A 50m X 50m sampling site within which NS measures aboveground and belowground carbon stocks and rates of carbon cycling.
Pitfall Trap
A round plastic container containing glycol that is buried approximately 10 cm deep and used to collect ground dwelling invertebrates.
Project
A concerted, data-driven effort to robustly measure variation in Biodiversity, Carbon, or Human-wellbeing in response to one or more sources of heterogeneity in a designated landscape.
S123
Survey123, a field-data collection app from ESRI which NS uses for recording all field observations and survey metadata.
Sampling Protocol
Explicit survey methodology that describes the design, effort, duration, configuration, and operation of a survey.
Sampling Site
A distinct, discrete spatial unit defined in at least two dimensions where sampling occurs.
Station
A point location where sampling occurs in space.
Study Area
A defined geographic region of interest within which one or more surveys investigate ecological patterns at one or more sites.
Survey
A set of simultaneous deployments of remote sensors over a defined period of time at a coordinated set of stations for the purposes of collecting data on the environment and its communities.

3. PROJECT OVERVIEW

3.1 PROJECT AIMS

The Rangelands Invertebrate Pitfall Trapping Survey aims to:

  1. Measure ground invertebrate biodiversity to contribute to the Rangelands Carbon-Biodiversity Survey.
  2. Measure the effect of vegetation structure on invertebrate diversity.
  3. Measure the effect of soil type on invertebrate biodiversity.
  4. Measure the effect of grazing type and intensity on invertebrate biodiversity.

3.2 PROJECT BACKGROUND

NATURAL STATE’s overarching goal is to catalyze big scale ecological restoration globally by revolutionizing impact monitoring, generating innovative, new, nature-based financial mechanisms and developing local leadership capacity. As part of this, NATURAL STATE is attempting to create impact monitoring systems that reduce the cost of measuring change in an environment, and that can provide traceable and verifiable results that can be used to inform financial instruments on the impact of interventions.

Invertebrate communities are an integral component of healthy ecosystems. Given the relatively short life cycles of many invertebrate taxa combined with their rapid progression through life stages, invertebrates are quick to respond to landscape level change and consequently often used as ecological indicators. Despite their small body size, invertebrates such as ants and termites account for the largest share of faunal biomass and act as ecosystem engineers, fundamentally impacting the structure and function of landscapes. They are essential for nutrient cycling and carbon sequestration. An in depth understanding of invertebrate communities therefore provides important insights into ecosystem health and is applicable to almost all landscapes, regardless of intervention type and management regime, which sometimes exclude larger taxa through the use of artificial barriers.

3.3 STUDY AREA

The Rangelands Invertebrate Pitfall Trapping Survey will be conducted across Lewa, Borana, and Lolldaiga conservancies. Sampling will occur at all GEM plots as well as a subset of carbon pool plots with variation in tree cover, soil type and grazing intensity. These will be a subset of plots at which the Carbon-Biodiversity survey takes place. The following is a map of the planned Carbon Biodiversity survey sampling sites.

3.4 PROJECT TIMELINE

The temporal design of the survey should track the temporal sampling from the corresponding carbon survey. Where long-term monitoring of carbon occurs (i.e., GEM plots) invertebrate monitoring can be replicated seasonally. Where carbon sampling is replicated over time (e.g., CP plots that are part of any exclosure BACI survey, usually where an intervention has been imposed), invertebrate sampling should occur whenever the carbon is sampled. Where carbon is only sampled once, invertebrate sampling should occur for a single deployment.

The Invertebrate survey will therefore be comprised of a number of sub-surveys:

Critical Sub-Surveys

  1. GEM wet 2023/2024 (October – April 2024): sampling at all GEM 18 GEM plots
  2. CPP dry 2024 (May/June - July 2024): sampling at a subset of CPP plots, specifics still to be determined

Ideally, all invertebrate sampling should be done during the wet season or soon afterwards, as invertebrate activity in the dry season will be low. Invertebrate sampling during or at the end of a long dry season should be avoided.

Sub-surveys are subject to change as the NS carbon sampling efforts and resources evolve. Additional sub-surveys will be added on in due course.

4. SAMPLING PREPERATION

The equipment mentioned in the list below needs to be gathered, checked and packed before sampling begins. If any sensors need to be configured prior to commencing sampling this will be documented below the equipment list.

4.1 EQUIPMENT LIST

Deployment

  1. Tablet with Survey123
  2. Soil Auger
  3. 3 X 50m measuring tapes
  4. 1m X 1m quadrat
  5. Disc pasture meter
  6. 15 pitfall traps (plastic containers) per plot
  7. 1.5L of Propylene Glycol (50% solution) per plot
  8. 15 plastic plates (only in rainy season) with metal pegs per plot
  9. Large plastic tote bin for carrying traps
  10. Marking tape
  11. Marking pen
  12. Bamboo sticks (6 per plot)

Retrieval

  1. Tablet with Survey123
  2. 15 plastic lids for the containers per plot
  3. Paper and pencil for writing labels to go into samples
  4. Large plastic tote bin for carrying traps
  5. Extra pitfall traps in case of need for redeployment
  6. Extra Propylene Glycol (50% solution) in case of need for redeployment
  7. Extra plastic plates or marking tape in case of need for redeployment

4.2 DEVICE CONFIGURATION

Each plastic container acting as a pitfall trap needs to have a QR code sticker stuck on the bottom of itself.

Plastic plates acting as lids should be prepared by painting the top green/tan and inserting two metal legs on opporite sides of the plate. These lids can be reused until they break and need to be replaced.

5. SAMPLING PROCEDURES

Pitfall trapping is a passive collection technique designed to capture ground-active invertebrates. The method involves digging open containers (e.g. plastic cups) into the ground in a way that the opening of the container is level with the surface level. The containers are filled with a fixative (e.g. propylene-glycol) that acts both as a killing agent and preservative for any invertebrates that are falling into these containers. The pitfall traps are open in the field for a standardized time period after which they are collected and the captured invertebrates will be identified by experts. In rainy seasons, a rain cover should be placed over the pitfall traps to reduce the chance of them filling up with water.

At each plot, 15 pitfall traps should be deployed. The spatial design should be as follows: Three parallel transects (A, B, C) with 5 traps each. The transects go from North to South and should be placed 15m apart from each other (see Fig.1: Transect A is placed 10m from the western border, Transect B 25m from the western border (in the center of the plot) and transect C 40m from the western border of the plot. Within each transect, traps are placed at least 10m apart from each other, with the first traps (A1, B1, C1) placed 1m into the plot from the northern border of the plot. This is to prevent interferance with the GEM sampling that happens in the 1m wide transect alonng the edges of the plot.

In cases where obstacles prohibit pitfall trap placement as described above the entire pitfall trap array can be shifted in any direction to avoid the obstacles. Examples of obstacles that would require shifting the pitfall traps include rivers, river beds and drainage lines as well as very uneven ground or soil erosion.

Obstacles and termite mounds: The traps should be placed in regular intervals. However, it is more important that the traps are not placed in conditions that are likely to change the sampling results. This would be the case if the trap would be placed directly on or in a termite mound, or on a game path. In these cases, it is better to place the trap 1-2m away (ideally either west or east) from the planned position. In the rainy season, it is also important to avoid placing the traps in visible waterways (especially when placed on a slope) to avoid the flooding of the trap.

Pitfall traps should be deployed for exactly three days, e.g. when placed on Monday they have to be collected on Thursday. This should be kept in mind when placing them, so pitfall traps should not be placed on a Wednesday as they will not be collected on the weekend. Pitfall traps that are left in the field for longer than 3 days cannot be included in the study and must be repeated. In extraordinary circumstances, e.g. in the rainy season with limited access to the sites, pitfall traps that have been exposed for 4 days instead of 3 might also be included in the study, but this should be avoided if possible.

Two environmental variables should be measured when placing the traps: grass biomass and percentage of bare ground. These variables can be measured either when the pitfall traps are being deployed or collected.

When retrieving pitfall traps, the QR code of all successful traps should be scanned into S123. When a trap did not work, was destroyed or disappeared, this information should be entered into Survey123, but the QR code need not be scanned.

During our trial phase of using S123 to record pitfall trapping data, we also include paper labels to identify the pitfall traps, in addition to QR codes. This is a temporary step and will likely be dropped in the future. Labels should be written by pencil on paper. The labeling should be as follows: “PLOT NAME – TRAP ID”, so for the pitfall trap placed at the position “A1” in the GEM-Plot “OW1” the label would be “OW1 - A1”.

It is very likely that the pitfall sampling will not be successful every time, as the success of the sampling can be influenced by humans, animals and weather conditions. The following steps should indicate when the sampling has to be repeated and when not. In general, if at least 13 of the 15 pitfall traps have been exposed for three days and contain a similar amount of chemical as when they were deployed, the sampling can be deemed successful and does not need to be repeated. In cases where a number of traps fail and sampling needs to be repeated, the traps that were successful should still be collected and processed. It could be that in the first sampling round 8 of 15 traps worked, and in the second sampling round again 7 of 15, and this would bring the number of successful samples above the required amount of 15.

When to repeat the sampling:

  • If more than two traps are destroyed, pulled out, have disappeared or are not functional: This could mean they are full of soil, fully flooded, have been pulled out by humans or baboons or have lost all their liquid
  • If the traps have been left in the field for more than 4 days

When not to repeat the sampling:

  • There are no or not many invertebrates in the traps

5.1 PITFALL TRAP DEPLOYMENT

  1. Locations of the 15 traps should be determined according to the figure above. The distance between the traps can be measured by steps (a measure tape is not necessarily required). If it is difficult to find the corners of the plot, find the central point using a GPS, and mark out a cross with measuring tapes pointing north to south and east to west. Then use a third measuring tape to find the corners of the plot.
  2. Use an auger to dig a hole to the depth of the container. Place the soil from digging next to the hole.
  3. Take two empty containers and place them on top of each other.
  4. Place the two containers in the hole and check that opening of the lower container is level with the soil surface. Use the soil from digging the hole to fill in around the container and make sure that there is no gap between the container opening and the surface. By keeping the second container on top during this process, soil is prohibited from falling into the lower sampling container. This is important as it speeds up processing later in the lab.
  5. Remove the upper container. Fill this container up to a depth of 2cm (~50ml) with Propylene Glycol and then transfer it to the lower container placed in the soil. By adding this step instead of pouring the Propylene Glycol directly into the container placed in the ground, we limit the risks of a) spilling chemical on the ground by pouring directly from a 2l bottle into a hole in the ground and b) pouring too much chemical into the container.
  6. Place a bamboo stick with marking tape tied around and the name of the trap written on the marking tape (eg A1), for traps A1, B1, C1, A5, B5, C5. The bamboo stick should be placed next to the pitfall trap, pointing towards the inside of the plot. In other words, for trap A1 the bamboo stick should be placed on the side of the pitfall trap that is closest to trap A2. For trap A5 the bamboo stick should be placed on the side of the pitfall trap that is closes to trap A4. This willl help you to locate the traps during retrieval.
  7. a. During rainy season: Place a plastic plate as a raincover roof over the container in the ground. The height of the plate should be ~10 cm above the ground. This should reduce the chance of the traps getting filled up with rain while still allowing invertebrates access to the trap.
  8. b. During dry season: place marking tape next to the trap, by tying it to same grasses or wood so that the traps can be found again easily. In the wet season the raincovers mark the location of the traps hence no marking tape is needed.
  9. Record all information in the Survey123 form: “Pitfall Trap Survey”. This will include information about sampling location, number of Pitfall traps deployed, and use of raincovers.

5.2 DISC PASTURE METER DATA COLLECTION

  1. Use the DPM to collect 100 readings from the plot in which the pitfall traps were deployed, spaced evenly across the plot (25 measurements per subplot).
  2. Record the data in the “Bare Ground and DPM Survey” S123 form.
  3. This can be done on the day that pitfall traps are deployed or the day that they are collected.

5.3 BARE GROUND DATA COLLECTION

  1. Collect 20 bare ground estimates from the plot in which the pitfall traps were deployed. 10 estimates should come from transect F1C1 – F1C2 and 10 estimates should come from transect F1C4 – F1C3. Estimates should occur every 5m along each transect.
  2. Estimate the perfectage of bare ground, with no vegetation or rock cover.
  3. Record the data in the “Bare Ground and DPM Survey” S123 form.
  4. This can be done on the day that pitfall traps are deployed or the day that they are collected.

5.4 PITFALL TRAP RETRIEVAL

  1. Check pitfall trap to determine if functional or not
  2. Remove pitfall trap from ground
  3. If not functional record this in S123
  4. If functional scan QR code into S123
  5. Place paper label in container
  6. Close container with lid and make sure lid seals properly
  7. Close the hole in the ground (by stepping on it, packing soil back in)

5.4 PITFALL TRAP REDEPLOYMENT

  1. If the traps have been left in the field for more than 4 days: Repeat the whole sampling process
  2. If all traps have been destroyed / did not work: repeat the whole sampling process
  3. If 0, 1 or 2 pitfall traps at a single site failed: no need for any redeployments
  4. If 3 or more pifall traps at a single site failed: replace these traps + 3 extra traps in case some traps don’t work again

6. POST PROCESSING

This section details all steps that need to be followed after returning to the office from the field to ensure that samples are properly processed and stored and that data is uploaded and saved to the correct location.

6.1 SAMPLE PROCESSING AND STORAGE

Upon return to the lab the contents of each pitfall trap need to be transferred into a whirlpack bag containing ethanol.

Timeframe The samples should be processed as quickly as possible after being retrieved from the field, but at least within 7 days after collecting the traps. In an emergency, this period can be extended up to 14 days, but this should not be the norm. If the samples are not being transferred within 7 days, it may be necessary to add more Propylene Glycol to the traps to ensure all invertebrates are fully covered.

Equipment

  1. Tablet with Survey123
  2. QR codes
  3. Tea strainers
  4. Washbottle with Ethanol (70%)
  5. Petri dishes
  6. Forceps
  7. Whirlpack bags
  8. Empty plastic bottle
  9. Plastic container

Procedure

  1. Log sample into the lab using the “Lab Log” Survey123 form.
  2. Put a tea strainer on top of a clean, empty plastic container
  3. Pour the contents of a pitfall trap into the strainer, the propylene glycol should be captured in the container underneath
  4. Transfer the propylene glycol into a plastic bottle/container
  5. Gently rinse the contents of the strainer containing the invertebrates with water
  6. Flip the strainer on top of the empty plastic container and flick with a finger against it to get all invertebrates from the strainer into the container
  7. Check if any invertebrates are left in the sieve and if so, transfer them with the forceps into the container
  8. Attach a QR code to the outside of the whirlpack bag
  9. Pour a small amount of ethanol into the container and transfer the specimens from the container into the whirlpack back
  10. Check that the paper label is in the whirlpack bag
  11. Close the whirlpack bag with as little air inside as possible
  12. Document the Sample transfer in Survey123 using the “Lab Sample Exchange” form
  13. Put all whirlpack bags from the same sampling location in a larger ziploc bag and include a label with the location ID written in pencil
  14. Store the samples in larger plastic containers that can be closed with a lid (to stop any ethanol from evaporating), away from direct sunlight.

Preparation and use of the chemicals

  • EtOH 70%: Use washbottles and make sure that they are labeled correctly.
  • Propylene Glycol 50%:
    • Mix 100% Propylene Glycol with equal amount of water to get a 50% solution. Add a few drops of dishwashing detergent to break surface tension.
    • For the recycled Propylene Glycol from previous traps: Fill the plastic bottles up to ¾ with the recaptured Propylene Glycol and fill up the remaining ¼ with 100 Propylene Glycol. Add some drops of dishwasher detergent.

6.2 DATA ENTRY AND UPLOADS

All data entry for this project is done via Survey123. There is no other data to upload.

7.1 DESIGN DOCUMENT

[In Progress]

7.2 OTHER RELEVANT SOPS

7.3 DATA ELEMENTS

Survey Design

Data Collection

8. REVISION AND VERSION HISTORY AND DESCRIPTION

==XXX==

9. SIGNATURES OF CONFIRMATION

Principal Investigator: ______________             Date: ___________

Director of Impact Insights: ____________             Date: ___________

10. APPENDICES

None currently available