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Pasture Biomass Protocol

Last modified by Bec Farrell on 2019/11/06 13:27

The following protocol document details the steps involved in collecting pasture biomass at a standard remote sensing star transect field site. It also details a number of ancillary data collected to inform further pasture and ground-cover modelling.
    

Site Selection

Pasture Biomass data is usually collected in conjunction with Star Transect field data, so the same protocol applies for site selection.
The following points need to considered when locating sites:

  • Plot areas should be homogeneous, minimising within site variation;
  • The edge of a site should be at least 100 metres from roads, power lines or other features not characteristic of the plot;
  • Sites should be located away from water run-on areas as moisture can affect reflectance characteristics; and
  • Sites should be located on level or near level ground. If a sloped site is necessary, avoid western and southern slopes as these can be affected by shadow.

Description of plot layout

Each site is 1 ha in size and should consist of three transects laid out in a star shape, with 6 quadrats placed along each (18 pasture collections in total).  The first transect runs from north to south, the second from 60º to 240º and the third from 120º to 300º. The quadrats are placed at 15 metre intervals along each of the transects, starting at the 15 metre mark on the right hand side of the tape in relation to the centre point.

protocol_biomass.JPG
Figure 1. Layout of pasture biomass quadrats on star transect.

Data Collection Process

Basic data required

The following data must be recorded for each plot, for data management purposes.

  • Geographic coordinates (easting, northing, zone) at plot centre
  • Operators: who collected the data
  • Date: consistent format (dd/mm/yyyy)
  • Time: consistent format (hh:mm)
  • Plot name: name of specific plot

Field equipment checklist

  • GPS (differential preferred)
  • 3 x 100 m measuring tapes
  • Stake or star picket
  • Hammer
  • Compass
  • 18 x 0.25 square metre quadrats
  • Clippers/Shears
  • Paper bags (all the same size/type)
  • Marker Pen
  • Measuring Pole (preferably 1 metre in length), for measuring pasture height
  • Digital camera
  • Paper data collection form or Mobile device with electronic site forms
    • An ODK form similar to the Auscover Forms is available on the JRSRP ODK portal titled 'Biomass Clip Form'. Instructions on how to install and used the form is available in the Field Data Collection Forms.

Site set-up

1. Lay out transect

  • Hammer stake into ground at centre of site.
  • Use compass to find 0° bearing and run a tape out at this bearing for 50 metres. The tapes should be placed on the ground underneath vegetation and be straight and follow a constant bearing. The operator should sight from the centre of the tapes along the bearing, and choose a landmark like a tree, to walk towards. Avoid trampling along the transects where observations will be made.
  • Return to centre and twist tape once around the stake to secure in place. Run remaining 50 metres of tape out at 180°.
  • Repeat for the second and third tapes, at 60°-240° and 120°-300° respectively.
  • Average GPS readings to obtain site centre coordinates.

2. Lay out quadrats

  • Start at the northern end of the 0°-180° and place Quadrat #1 at 15 metres from the end of the tape.
  • The quadrat should be placed  as flat as possible on the right hand side when facing outwards from the centre point, lining the centre of the quadrat side with the 15 metre mark on the tape measure.
  • Place Quadrat #2 through to #6 at 15 metre intervals along the tape, at 30m, 45m, 60m, 75m and 90m respectively, on the right-hand side facing from the centre point.
  • Quadrats #7 to #12 are placed at the same intervals along the 60°-240° tape, while Quadrats #13 to #18 are placed along the 120°-300° tape.

Data collection

It is recommended to follow the Star Transect data collection for gathering information about the site. This project expands the method used to collect star transect point intercept measurements for the purpose of distinguishing tree / shrub litter from grass and forb litter. Three additional classes have been added to the electronic ODK form including:

  • Grass or forb litter (un-attached dead leaf or stem material)
  • Tree or shrub litter (un-attached dead leaf, stem or branch material upto a thickness of 50mm)
  • Course woody debris (Un-attached dead tree / shrub stem or branch material greater than 50mm diameter)

The following data collection steps relate to each of the 18 quadrats only.

1. A paper form or electronic form on a mobile device is used to record the following information: 

  • GPS location of the quadrat 
  • Size of the quadrat 
  • A pre-clip photo of the quadrat at waist height, to depict ground cover inside the quadrat
  • Visual estimates of 'Green Cover', 'Total Standing Dry Matter Cover' and 'Total Cover' percentages of the ground cover inside the quadrat
  • Weight of paper bag used to collect and store pasture biomass samples
  • Height of ground cover/pasture inside the quadrat, in centimetres

2. Collect pasture biomass sample

  • Collect ground cover inside the quadrat using shears when necessary and sort into 3 different sample types: 'Standing Matter', 'Litter' and 'Forb' if present.
  • Use shears to clip grass off at ground level.
  • Place the samples into paper bags labelled with the site name, date, quadrat number and sample type. 
  • Weight each of the sample types and record in grams. 

3. Collect post-clip photo

  • Take a post-clip photo of the quadrat to depict if any pasture cover was left behind after the clipping, such as the root clump of grass. 

4. Repeat the above steps for all 18 quadrats. 

5. Post-field sample processing

  • Place all samples into drying oven at 60 degrees Celsius for 3 to 4 days.
  • When the samples are dry, weigh each of the samples and record in grams to determine the moisture content.

Optional field data collection

The following data collection types at site level are recommended in conjunction with the Pasture Biomass collections.

 Pasture Height 

 Soil Moisture 

 Soil Penetrometer 

Data Recording and Storage

Data in the field will either be directly entered into specially prepared ODK forms, or into field sheets and then transcribed later.  

Data is stored in the AusCover PostGIS database, located on the AusCover UQ server. Data is downloadable from the AusCover spatial portal.

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Created by Bec Farrell on 2019/10/28 11:14

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