A return field trip to Muggon and Meka Stations in the Murchison has been necessary to gather further measurements to fill gaps in rangelands carbon data.
This, and previous data gathered, is part of a continuing effort to acquire essential data about above-ground and below-ground carbon concentrations and stocks in various land systems. It will allow carbon stocks for each trial site to be calculated and the effect of the grazing trial on carbon sequestration to be properly estimated in the future.
Adrian Williams, principal vegetation scientist, identified some major gaps in the data from two of the sites during analysis of data from four previous Carbon measurement expeditions. Subsequently, consultants David Blood and Bill Currans returned to the sites in July to relocate 80 sites on Muggon and 30 sites on Meka and record the missing data.
During analysis of existing data collected in 2012 and 2013, it became evident that important aspects of the ecosystems being measured had been overlooked.
“The process of designing the field methods for assessment of above ground carbon was always an evolution, as there was little in the way of proven existing methodology, so the Rangelands Carbon team of Peter Russell, Adrian Williams and myself, had to develop techniques for shrubland sites based on existing research,” Mr Blood said.
This evolution of course resulted in elements of the early surveys being omitted in some cases.
One of the major elements that had been overlooked in the first two was the presence of dead standing trees.
The carbon in a standing dead tree is obviously a static or declining quantity, but is still an important and significant component of the total carbon stock of arid ecosystems and must be accounted for in any assessment.
“Future modelling will determine the rates of decline in various species and landscapes,” Mr Blood said.
The reassessment of the Muggon and Meka sites involved the counting and classification of all intact and recognisable standing dead trees and shrubs.
Long dead trees were identified only to genus level where species was not obvious and all intact dead plants were counted and classified into pre-determined size classes. Live plants were also classified into size classes at Muggon as this was a recent addition to the method after the first Muggon survey in 2012.
“An interesting aspect of the resurvey at Muggon was the degree of change evident in the vegetation between 2012 and 2014,” Mr Blood said.
Seasonal conditions have been very dry, but simultaneously the absence of feral goats has allowed a dramatic increase in small palatable shrubs.
Mr Blood said a curious effect noted at most sites was the number of species that resprouted or coppiced after being cut for sampling in 2012.
All Eremophila and Senna species had formed dense coppices in all land systems, whereas only one species of Acacia had resprouted – A.subtessaragona (spreading gidgee or Gascoyne gidgee) on the stony footslopes of the Sherwood land system near Errabiddy Bluff.
Litter cover was recorded at all carbon surveys, but only as a presence or absence. Due to the dry seasons since 2012, much litter had been lost as a result of thunderstorms, but the analysis will use the distributions of litter recorded in 2014 to allocate classes to the existing data.
As usual, the hospitality of Chris Graham at Muggon and the Grinhams at Meka was exemplary and very much appreciated.
Image: Bill Currans measures out a plot to record light, medium and heavay litter (©DBlood)