Rangelands NRM Blog, News & Resources

Strong relationship found between plant structure and contained carbon

A remarkably strong relationship between particular plant shape measurements and contained carbon has been established following analysis of field and laboratory data from the WA rangelands.
Rangelands NRM has been undertaking a number of field sampling activities as part of the Royalties for Regions-funded Carbon Awareness Program to measure the amount of carbon both above-ground (in plants) and below-ground (in the soil), in different land systems.

Senior Rangelands Scientist at Rangelands NRM, Dr Peter Russell said analysis of field and laboratory data acquired at Meka Station in mid-2013 have been completed and is revealing some very encouraging findings.

“Analysis is showing that the amount of above-ground carbon held in the vegetation is related to plant size and shape, such as height, canopy dimensions and stem diameter(s),” Dr Russell said.
This means that results can be used to reduce the number of plant measurements required and thus the time and effort needed to undertake field work.

“It has been a challenge to develop field techniques to adequately measure above-ground carbon stocks in the mulga shrublands without having to harvest and weigh all plants in each sample plot,” he said.

Additionally, most of the above-ground carbon is held in the ‘woody’ plants such as mulga, compared with the limited amount held by shrubs and grasses.
“Whilst this is reasonably intuitive for those familiar with mulga woodlands, we have established the difference in ratio or percentage terms,” he said.
Dr Russell added that the new data will be used to inform computer (numerical) models of carbon sequestration in order to predict future carbon stocks under a variety of land management scenarios and will also inform or calibrate remotely-sensed biomass data acquired by satellites, unmanned aerial vehicles (UAVs) and light aircraft.
“In the near future, we believe that remotely-sensed estimations of carbon stocks will become routine and very cost-effective,” Dr Russell said.

Dr Russell said although the work is not yet finished, in the not-to-distant future, we believe that the vast rangelands of WA will be in a position to begin contributing substantially to Australia’s carbon abatement targets.
In so doing, several co-benefits such as improved ecological health (through improved vegetation and soil health, and erosion mitigation), improved primary productivity reflected in livestock productivity and flow-on economic and social benefits, should begin to be realised.
This work will also help develop an appropriate CFI-approved rangeland regeneration/restoration methodology, tailored for carbon offset projects in the southern rangelands of WA.
Background information

In 2013, Rangelands NRM commenced a major three-year programme of work called the Carbon Awareness Project. The project is funded by the Western Australian government Royalties for Regions with in-kind assistance from land managers for on-ground work.  It aims to increase awareness of the opportunities, benefits and risks for pastoralists, other land managers and custodians in the Western Australian rangelands who are considering participation in carbon farming activities.

In addition to providing Carbon Farming Initiative (CFI) information, an important part of the programme is the undertaking of demonstration projects with participating pastoralists and others. Each demonstration project consists of a substantial field campaign of soil and vegetation sampling (see photos below) on particular land systems, in areas where a change of land use, management practice or intervention is to be implemented.
An important aspect of this work, known as ‘land system characterisation’, helps us to understand the distribution of sequestered organic carbon stocks in the rangelands.  Different land systems have different proportions and amounts (stocks) of carbon held in the above-ground biomass (vegetation) compared with that held by below-ground (soil) biomass.  This is absolutely essential information for future feasibility studies that will need to be done by carbon credit or offset project proponents.
A remarkably strong relationship between particular plant size/shape and contained carbon has been established following analysis of field and laboratory data from the WA rangelands.

Figure 1.  David Blood and Jess Bibby sampling a Curara (Acacia tetragonophylla) tree for weighing and bagging.  Samples are sent to the laboratory in Perth for analysis.  Photo by Peter Russell, 1 June 2013.
Figure 2.  Soil (drill rig in background) and vegetation sampling field operations at Meka Station, May 2013.  Photo by Peter Russell, 30 May 2013.