Catchments and Land capability – where forest restoration begins
” . . . This map displays the inherent physical capacity of the land and its soils to sustain a range of land uses and management practices in the long term. It can be defined as the ability of the land and the soil to absorb disturbance and still retain its basic function and structure. This soil and land data and the associated descriptions for each class are drawn from OE&H (2012b).”
“The land and soil capability assessment scheme – Second approximation” from which the map of land capability in the Southern Rivers Catchment Action plan is derived places forestry in all categories even though Class seven and eight land invariably does not support commercial forests.
The graphic below shows these Classes in the Dry/Murrah and Cuttagee catchments where low capability land dominates, the upper and middle reaches have very or extremely low capability and land with moderate to low capability has been cleared.
Due to BMAD watercourses have given a fifty metre buffer and tagged as Class 8. The cleared areas contributed most of the original post European sediment to the Dry/Murrah River although this has since been greatly increased with erosion from lands of lower capability.
The variation in land capability also defines the vegetation likely to occupy any given area and the variation in capability at a catchment scale is consistent with land capability at a sub-catchment scale.
The declining health, structure and resilience of native forests poses a long term threat to arboreal herbivores, especially Koalas and Greater Gliders and ultimately because soils are becoming more erodible, potable water supplies in South East Corner Bio-region.
This situation requires a different appreciation of estimations of land capability and an more sensitive approach to management aimed at restoring the forests.
A requirement of a more sensitive approach means that with the exception of established roads or as required for the restoration of cleared land, the impacts of motorized wheeled and tracked vehicles on lands from Class 4 through to Class 7 can no longer be considered acceptable due to the long term detrimental effects these machines have on soil structure and fertility.
Vegetation – knowing what’s there
” . . . The community has raised concerns regarding two environmental issues that were not identified as issues by SKM in their biodiversity assessment, being the potential impacts of the proposal on Bell Minor Associated Dieback and Myrtle Rust. RMS has requested that SKM further investigate these issues and details will be provided in the REF when it is placed on display for public comment in mid 2013.”
The quote above is from the Dignams Creek issues report on the proposed Princes Highway re-alignment published in May 2013. The photo below was taken on freehold land at the junction of Knights Creek and the Murrah River where Bell-Miner Associated Dieback (BMAD) has been evident since 1994.
There is no reference to BMAD in the Southern Rivers Catchment Action Plan and in its River Priorities map Knights Creek catchment, almost entirely in Mumbulla State Forest, is suggested as a ‘priority to maintain in good condition’.
” . . . Other interesting projects in the pipeline for the biodiversity team include identifying areas of forest in poor condition that could be rehabilitated. “These could be areas that have failed to regenerate properly,” OEH biodiversity conservation manager for Southern NSW Michael Saxon press release dated November 2012,
On March 1 2013 the following condition became operative as part of Amendment No. 6 to the Integrated Forestry Operations Approvals for the Eden Region.
 Condition 5.6 (j) i. and ii
Omit condition 5.6 (j) i. and ii (now 5.6 (k) i. following amendment 18 above).
Insert instead the following:
i. Damage to the following types of trees or shrubs must be avoided or
minimised to the greatest extent practicable during harvesting operations:
all stands of Allocasuarina or Casuarina spp.,
individual shrubs or trees of Allocasuarina or Casuarina spp. where there is
evidence that glossy black-cockatoos have been feeding on them, such as
chewed cones at the base of the trees.
The photo above is of an unlogged coupe in compartment 2179 of Mumbulla State Forest, an outcome of the Murrah/Mumbulla Residents Group organizing soil sampling and chemical and physical analysis in the compartments in 1994. The photo below was taken less than 50 metres away in the adjacent coupe that was subjected to integrated logging in 1980.
Most of the trees that have grown back in the logged coupe are the mid-storey species Black Forest Oak (Allocasuarina littoralis).
As indicated in the map below trees are subject to BMAD in gullies and in seven of eight plots surveyed to date in ‘Coastal Foothills Dry Shrub Forest’, threatened by extensive canopy dieback are dominated by Black Forest Oak including supposedly unlogged coupes in the exclosure catchment.
Addressing soil degradation and increasing the area of land managed within its capability is a major priority and to do so requires an understanding of soil limitations and the negative impacts from reduced biodiversity and decades of industrial logging and inappropriate burning.
In logged or otherwise degraded forests, the trees that initially grow back, like Black forest oak and Silvertop Ash, are susceptible to and frequently killed by even low intensity fire.
‘Regrowth forests’ are deliberately burned at around fifteen years after logging, killing many trees and putting tonnes of CO2 and a list of other pollutants into the atmosphere. Black forest oak is a shallow rooting mid-storey tree that on the one hand increases the potential for a crown fire in eucalyptus by filling the gap between the ground litter and tree tops. Secondly where they grow without eucalyptus trees, the benefits of large trees provide in reducing the rate at which water passes through the soil have been lost and whether large trees can grow back is uncertain.
Physical thinning of these trees in dry eucalyptus forests is possible without using machinery that the land cannot support and as indicated below, one use of Black Forest Oak timber may help replace the use of eucalyptus for some products, in this case Spotted Gum (Corymbia maculata).
Many trees will not be suitable for value adding and the development of ‘slow pyrolysis’ technology provides the opportunity to use this otherwise polluting biomass to produce ‘bio-char’ for returning to the soil, while using the ‘syngas’ generated in the process to produce carbon negative electricity and with other processes the production of liquid fuels to reduce consumption of and dependence on fossil fuels.
The CSIRO’s fact sheet on biochar provides an integrated view of biochar production, the difference with forest restoration requirements is that organic matter taken from forests is to be returned to forests to increase soil fertility on ridges.
There is also significant potential to grow biomass on cleared private land, in particular industrial hemp, that improves soil structure and will provide the feedstock to produce bio-char for incorporation into these soils.
Such an approach would benefit from integrating biomass management from forestry, agricultural and urban sources.
In the interim and without the benefit of a more controlled process, it is possible to make bio-char in the back yard as illustrated below .
Restoring Fauna Biodiversity
Funded under the Natural Heritage Trust in 2000, the exclosure encompasses an area of about 200 hectares and is intended to aid in the controlled re-introduction of locally extinct native species that are necessary to maintain soil fertility and forest health. These species include but are not restricted to the Pademelon, Long-footed Potoroo and the Bettong.
The list of flora identified in the catchment numbers 140 species and 39 of these are classified as trees. About half of the tree species are associated with riparian and rain forest areas and the other half with the threatened ‘wet and dry’ eucalyptus forests.
Water and Nutrients
To survive, koalas require eucalyptus leaves with sufficient water and nutrients. The presence and density of koalas in forests reflects both the level of nutrients and water available for trees and therefore koalas at that location.
With regard to water the Bega and Eurobodalla Shire Councils are involved with South East Water Quality Monitoring Project although Bega Council “does not have a formal Water Monitoring Program in place, it implements monitoring in response to perceived issues associated with water quality and river health”
“The Healthy Rivers Commission report into the Bega River (May 2000) recognised that there may be a lack of information regarding surface water quality but only recommends additional monitoring which “is targetted and well directed…to secure river health” (HRC 2000 p84). This approach will see Council continue to develop its water quality monitoring program and this will be reported further in the next comprehensive State of Environment report.”
The NSW Department of Land and Water Conservation was monitoring water quality at three locations in the Brogo, Bega and Towamba catchments but sampling was only undertaken on bi-monthly basis and was not aimed at sampling turbidity for individual flood events.
While methods and equipment to continuously measure water turbidity and other contaminants have been available for some time and despite the fact that the NSW Environment Protection Authority’s main concern is water pollution, current testing is mostly aimed at determining the spread of sewerage on beaches.
Sedimentary rock forms the basis of Category A koala habitat and in the short to medium term, attempting to increase soil fertility of the generally stony soils derived from local sedimentary rocks, given the surface area of rock available to breakdown is proportionally greater than that in soils derived from igneous rocks is more likely to produce measurable outcomes.
Changes to turbidity levels in a given catchment may demonstrate either increasing or decreasing soil fertility depending on management.
There may also be the opportunity to compare soil loss against the rates at which each rock type breaks down to form soil. In the catchments from Dignams to Wapengo igneous rocks are generally associated with former primary or Category B, koala habitat.
Critical to such an approach is recording rainfall and the automatic monitoring of flood water turbidity.
Pictured below is the OBS-5+ High Suspended Sediment Concentration Monitoring System with Pressure Sensor available from Campbell Scientific. The manual indicates “The OBS-5+ monitors high sediment concentrations using an infrared laser and a proprietary dual photo detection system (U.S. Patent No. 5,796,481). The probe transmits sediment concentration and depth to a PC via an RS-232 or RS-485 link. Data is also stored internally.”
Comparing and contrasting standards
In order to analyze social, economic and environmental values together , the Queensland Flood Commission proposes a Monte Carlo framework suggesting –
“Common sense dictates that when a large amount of rain has fallen, it is more likely that the dams will be full and the catchment will be saturated. The relationships between factors must be reflected by ascribing mutually consistent values to them. This correlation between data sets must be determined before the Monte Carlo analysis can be performed.”
The need for natural resources information is a global issue and water catchments are the fundamental unit to determine whether the land’s productive capacity is being maintained, improved or otherwise. Such issues form part of the requirements forest managers are supposed achieve to qualify for certification.
Criterion 4 of the Australian Forestry Standard requires:-
“(4.4.1). . . The forest manager shall identify existing productive uses of the defined forest area to support the maintenance of the land’s long-term productive capacity and ensure it is not compromised by wood production.”
However, Criterion 5 of the Australian Forestry Standard states:-
” (4.5.3) . . . Forest managers managing native forests shall, where appropriate, use fire and other disturbance regimes that are applicable to the forest type or community to support the protection and maintenance of biological diversity values.”
Introducing a management system based on biomass retention and soil enhancement at a catchment scale, provides the opportunity to scientifically test this system against current management, where maintenance of the long-term productive capacity of forests is based on the use of fire and other disturbance regimes.
A fully integrated approach to sustainable land management requires extensive monitoring of various environmental values and the collection of a large amount of data, the collection of these data will be greatly assisted with the rollout of the National Broadband Network.
Last modified June 18 2013 – To be continued/ added to.