Rehabilitation of the Finn Road gravel rehabilitation site and trial area

Rehabilitation of the Finn Road gravel rehabilitation site and trial area

Dr Sean BellairsSenior Lecturer Restoration Ecology.

October 2022

Unpublished Report

School of Environment,

Charles Darwin University

Summary

The Finn Road site is a rehabilitated gravel extraction site or mine which is located between Palmerston and Berry Springs, south of Darwin in the NT, Australia (Figure 1, Figure 2). Topsoil was stripped, and gravel was removed in 2012 and 2013. Rehabilitation treatments were applied to portions of the Finn Road gravel site in August 2013 as part of a CDU, Greening Australia, Extractive Industry Association and NT Government project. Twenty-four large plots were established across the different rehabilitation treatment types and vegetation establishment treatments were applied at the end of January 2014. Some plots had a broadcast seed mix applied and other plots had seedlings grown in a greenhouse as tubestock, and were planted out with the seedlings.

The plots that were planted with tubestock have had plant survival monitored in September 2014 and annually until 2021. The tubestock plots, together with plots sown with broadcast seeds and control plots with no treatment, have been used as an educational site for environmental science students and overseas mining restoration officers, among others. The data you have is based on the unmined vegetation surrounding the site, plus either the old stockpiled topsoil treatment (FO1, FO2, FO3 are the three locations where the plots are on Figure 4) or the untreated bare gravel base (FU1, FU2, FU3).

Figure 1. Map of route (in blue) from CDU Casuarina Campus to the Finn Road site

10668005029200Berry Springs

00Berry Springs

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Figure 2. Location of the Finn Road gravel extraction and trial site shown in orange.

Details of treatments applied to the Finn Road siteOn the southeastern edge of the site, topsoil was stripped to a depth of about 10 cm in December 2012 and was stockpiled over the wet season before being spread on top of the gravel base in August 2013. On the western edge of the site, topsoil was stripped in March/April 2013 at the beginning of the dry season and spread later in the dry season in August 2013. The topsoil that was stockpiled for longer and over the wet season is described as old, while the topsoil that was only stockpiled for a few months is described as new. To process the gravel, oversized material is sieved out, and then the saleable gravel is sieved out. The fine sand textured material remains.

Following gravel extraction, a range of substrate treatments were applied to the site (Figure 3). The two ages of topsoil, the oversized material, the fine material, and the bare gravel base, were all used as rehabilitation substrate treatments.

Figure 3. Approximate areas where various media treatments were applied over the gravel base by Keith Joy of Tomazos Group in 2013.

New topsoil treatment areas (Mixed newest) had the topsoil that was stripped in March/April 2013 applied on the western side of the site in August 2013. Topsoil was spread out as low 2 m x 2 m mounds and because the amount of soil was limited, this treatment had the topsoil interspersed with similar sized mounds of fines and oversize material.

The older stockpiled topsoil that was stripped in December 2012 (Mixed oldest; Mixed) was applied on the southeastern edge in August 2013. Again, the topsoil was spread out as low 2 m x 2 m mounds and this treatment had the topsoil interspersed with similar sized mounds of fines and oversize material.

The fines treatment was the sieved material which was finer than the grade of saleable gravel removed from the site. It was applied on its own as a 20 30 cm deep layer in three areas.

These larger areas (mixed newest topsoil, mixed old topsoil and fines) were large enough to establish nine 10 m x 20 m plots in three blocks (Figure 4). Nine 10 m x 20 m plots were also established in the bare gravel base which remained after the gravel was removed, as a media control to assess the effectiveness of the other treatments versus planting in the bare gravel base. For each of these media treatments three plots were planted with tubestock, three plots had broadcast seed applied and three plots did not have any additional seeds or tubestock applied, to assess the seeds present in the media.

Other small trial areas were placed along the eastern edge. This included an area of small and an area of large oversize material. Oversize material was sieved out because it was too large for saleable gravel. A third small trial area included older stockpiled topsoil as a continuous layer. These areas were relatively small and were only large enough to establish six 10 m x 10 m plots, of which three were sown with broadcast seeds.

Figure 4. Locations of the monitoring plots. Plots planted with tubestock are in green and plots sown with a broadcast seed mix are in yellow. Control plots which received the same media treatment but did not receive additional seed or tubestock are in pink.

For the ENV303 ENV503 assignment you are using data from plots which had tubestock planted. The tubestock included five species, Acacia lamprocarpa, Cochlospermum fraseri, Eucalyptus miniata, Eucalyptus tetrodonta and Syzygium eucalyptoides subsp. bleeseri. They were planted at 67 plants per 200 m2 plot (Appendix 1).

Data is either from the fresh topsoil plots FN1, FN2, FN3 or from the untreated gravel base plots FU1, FU2, FU3.

Other plots had a broadcast seed mix applied, which included 13 species with 1700 seeds sown per plot (Appendix 2) or did not have a seed/seedling treatment. Later, the central area of the site had topsoil and fines material spread after the trial plots had been set up, probably in 2016.

Appendix 1. Initial planting density per tubestock plot (10 m x 20 m) in late January 2014.

Acacia lamprocarpa20

Cochlospermum fraseri20

Eucalyptus miniata14

Eucalyptus tetrodonta7

Syzygium eucalyptoides subsp. bleeseri5

Appendix 2. Broadcast seed mix applied per 10 m x 20 m broadcast seed plot.

Species # seeds per 10g # seeds per plot Seed weight (g) Seed mix sown per plot (g)

Acacia holosericea1,304 100 0.0077 0.77

Acacia lamprocarpa271 100 0.0369 3.69

Brachychiton diversifolius62 100 0.16 16.00

Cochlospermum fraseri200 100 0.05 5.00

Eucalyptus miniata 286 100 0.0350 3.50

Eucalyptus tetrodonta 1909 100 0.0052 0.52

Petalostigma pubescens 250 100 0.04 4.00

Alloteropsis semialata3432 200 0.0029 0.58

Aristida inaequiglumis7178 200 0.0014 0.28

Heteropogon triticeus135 150 0.0741 11.11

Sorghum intrans360 200 0.0278 5.56

Sorghum plumosum698 200 0.0143 2.87

Erythrophleum chlorostachys67 50 0.1502 7.51

Appendix 3. Maps of the location of the study site near Finn Road, north of Berry Springs, NT.

Species for C-S-R (competitive, stress, ruderal adapted) assessment

Undisturbed site

Trees Shrubs and herbs Grasses

Acacia aulacocarpaAcacia oncinocarpaBuchanania obovate

Cochlospermum fraseriCycas amstrongii

Eucalyptus miniata

Planchonia careyaErythrophleum chlorostachys Grevillea pteridifoliaXanthostemon paradoxus Euphorbia schultziiGoodenia armstrongianaHibbertia complanataPetalostigma pubescens

Heteropogon contortusHeteropogon triticeusThemeda triandraDisturbed site

Trees Shrubs and herbs Grasses

Acacia lamprocarpaAlstonia actinophylla

Cochlospermum fraseriEucalyptus miniata

Eucalyptus tetrodonta

Grevillea pteridifoliaSyzygium eucalyptoidesAcacia holosericeaBreynia cernua

Calytrix exstipulataGrevillea dryandriAndropogon gayanus (Gamba grass)

Cenchrus pedicellatus (annual mission grass)

2023 instructions for Assessment Item 3 (ENV303 and 503)

Description/Focus: Field project report effect of disturbance on vegetation structure and composition

Value: 20%

Due date: Monday, Week 9

Length: 2,000 words

Task: Prepare a report using data collected by past students and photos of sites disturbed by gravel mining and undisturbed sites.

Introduction to Assignment 3

You will prepare a report that assesses the vegetation in an area of woodland that is relatively undisturbed and compares it to vegetation in adjacent woodland that has been disturbed by gravel mining.

Previous students monitored three replicate 10 m x 20 m plots in both the disturbed and the undisturbed sites (Figure 1). They used a 10 m x 20 m plot to measure tree height, health, diameter, density and composition. Within each plot they used twenty 1 m x 1 m plots to assess shrub density and composition (see the attached Figure 2) and the frequency of Gamba grass, an important introduced grass weed, was also recorded in those twenty quadrats. They also recorded the herb and grass species that were present within five of the 1 m x 1 m quadrats within each plot. In those same five quadrats per plot, they measured the proportion of total herb foliage cover, grass foliage cover, bare ground and litter.

The raw data is provided and needs to be summarised into figures and tables. Use scientific conventions for the presentation of figures and tables, with figure titles below the figures and table titles above the tables. Look at ecological journals and note the presentation of figure titles, axis titles of graphs, table headings, the inclusion of measurement units in column or row headings in tables and on axes in graphs. Note the results text needs to highlight the key findings that are presented in tables and figures.

In the discussion, consider the following three points when discussing the results.

Discuss the variation in vegetation composition and structure between the mined and unmined areas and discuss any implications for rehabilitation success.

Discuss the sustainability of the rehabilitation and any ecological function. (Ecological functional issues would include issues such as pollination, recruitment, hydrology, nutrient cycling, and responses to disturbance, but you would not have information to assess all these issues.)

Select two plant species from the disturbed site and two species from the undisturbed site of vegetation. Discuss the characteristics of the four species qualitatively in terms of whether they have ruderal, competitive and/or stress selected features (see the study guide Topic 7 and the paper by Grime for more information).

References should be in the APA style, and the unpublished reports provided for Assignment 3 can be cited like any other report. The data need not be referenced.

Report structure

Introduction

The purpose of the introduction is to highlight important features and issues that are affecting the study and it should focus on local and regional factors rather than global factors. So for Assignment 2. I would expect that bauxite, the cause of the red mud being that it is a by-product of the Bayer process. I would expect red mud to be generally introduced as a harsh medium because of its chemical, physical and biological attributes. I would expect Eucalyptus camaldulensis to be introduced in a paragraph. For Assignment 1, I would expect that the use of models of vegetation development in ecology to be introduced, along with a brief introduction to the disturbance and scenario.

I want the introduction to be succinct and focused on key local or regional issues about the study that an NT environmental scientist would want to know so that they can orientate themselves to key information about the study. Avoid presentation of global issues, unless essential.

A report aim is essential and it is to be concise. It should be clear and comprehensively identify the focus and scope of the study but no more than two sentences.

Methods

Use the video that I have recorded to learn about the methods and to write up the methods section, such that there is sufficient detail for an environmental professional to go and repeat the monitoring using the same techniques.

Results

Firstly, prepare a graph showing the average tree height per plot for trees over 1 metre in height. Two graphs are to be prepared, one for the disturbed site and one for the undisturbed site. They are to be column graphs with three columns/bars representing the three plots for each species (the data for the same species across the three plots are to be grouped together), and all tree species at the site are to be included on the same graph.

Secondly, present the other vegetation and ground cover data as you wish, other than the following requirements.

Tree abundance should be presented as number of plants per hectare. One tree in 200 m2 = 1 x 10,000/200 trees ha-1 = 50 trees ha-1.

Shrub abundance should also be presented number of plants per hectare.

I want the results to show the variation from plot to plot, and other than the graph that is to be presented as has been described, the variation can be presented as either be the values for each of the three plots, or it can be the mean and a measure of variation. Either is fine.

The data I will send out may vary between students. The data I have provided does not need to be referenced.

Discussion

Focus on the three discussion points.

Effect of disturbance on vegetation structure and composition.

Implications for ecological sustainability of the rehabilitation.

Application of the C-R-S scheme of Grime (1979) to the four species.

References

Use the APA style, though if you generally get it correct and most importantly, are consistent, that is fine.

https://libguides.cdu.edu.au/cdureferencing/apaAny questions? Please email me or post them on the discussion board.

Assessment

criteria: Introduction

Did the introduction clearly and concisely outline the nature and scope of the problem investigated and have a clear aim? 12%

Methodology

Has the method of investigation been adequately explained in sufficient detail to repeat the study? 16%

Data treatment and analysis

Were the results clearly and correctly presented?

Were the tables and figures clearly able to be understood without reference to the text?

Are key results emphasized in the results section? 24%

Understanding of the significance of work

Assessment of the judgment of the author in highlighting pertinent information.

Interpretation of results with respect to Study Guide notes, Readings and other material.

Logical presentation of arguments. 32%

Clarity and concise style of presentation

Correct spelling and grammar; accuracy of referencing; concise logical style 16%

Total 100%

Figure 1. Sampling strategy for undisturbed and disturbed woodland; Plots were positioned randomly through the vegetation community type to be assessed.

Brown plots are the plots in the mined area; blue plots are in the unmined vegetation.

Figure 2. Diagram of the set up for the individual monitoring quadrats.