Submitted to COALTECH Research Association Native Species Trial

The Evaluation of Three Native Grass Species and a Tree Species as a Vegetation Option for Coal Mine Rehabilitation on the Mpumalanga Highveld of South Africa

Martin Platt

ABSTARCT Three field trials were established in early March 2004 on topsoil prepared for seeding at Kleinkopje Colliery, Optimum Colliery and Syferfontein Colliery, all situated on the Mpumalanga Highveld of South Africa. Cynodon dactylon , Themeda triandra , and Hyparrhenia hirta plugs were established in plots and were treated with and without fertilizer. Field measurement of survivorship, cover, and biomass production, were taken until July 2007. Acacia sieberana was also established and was evaluated for survivability, height and basal diameter. The results indicate that Cynodon dactylon out-performed the Themeda triandra and Hyparrhenia hirta , achieving 100% survivability and cover at all sites by 2007, regardless of fertilizer addition. Trees were able to establish at Kleinkopje Colliery attaining 97% survivability by the end of the trial, but performed poorly at Optimum Colliery and Syferfontein Colliery. Establishing plugs as a vegetative option on mined land could be used when slopes for a planter machine is too steep, and in establishing buffers against pasture grass intrusion into ecologically sensitive areas.

TABLE OF CONTENTS ABSTARCT ...... i TABLE OF CONTENTS ...... ii

CHAPTER 1

LITERATUREREVIEW …………………………………………………………………………………………………1 1.1 INTRODUCTION……………………………………………………………………………………………..1 1.2 OPENCAST MINING AND REHABILITATION METHOD…………………………………….2 1.3 SOIL COMPACTION………………………………………………………………………………………..3 1.4 SOIL AMELIORANTS………………………………….……………………………………………………4

CHAPTER 2

MATERILAS AND METHOD.. ……………………………………………………………………………………..5 2.1 EXPERIMENTAL LAYOUT………………………………………………………………………………..5 2.1.1 SITE DESCRIPTION………………………………………………………………………………5 2.1.1.1 KLEINKOPJE COLLIERY…………………………………………………………….5 2.1.1.2 OPTIMUM COLLIERY………………………………………………………………5 2.1.1.3 SYFERFONTEIN COLLIERY……………………………………………………….6 2.2 EXPERIMENTAL DESIGN…………………………………………………………………………………6 2.2.1 TRIAL ESTABLISHMENT………………………………………………………………………6 2.2.2 SPECIES………………………………………………………………………………………………8 2.3 TRIAL SETUP………………………………………………………………………………………………….8 2.3.1 PLANTING………………………………………………………………………………………….8 2.3.2 FERTILIZER APPLICATION…………………………………………………………………..8 MAINTENANCE……………………………………………………………………………………………..9 2.4 FIELD MEASUREMENTS……………………………………………………………………………….10 2.4.1 SURVIVORSHIP…………………………………………………………………………………10 2.4.2 COVER……………………………………………………………………………………………..10 2.4.3 BIOMASS……………………………………………...... 11 2.4.4 TREE SURVIVORSHIP………………………………………………………………………..12 2.4.5 TREE HEIGHT……………………………………………………………………………………12 2.4.6 TREE BASAL COVER………………………………………………………………………….13

CHAPTER 3

RESULTS ………………………………………………………………………………………………………………….14 3.1 KLEINKOPJE COLLIERY………………………………………………………………………………….14 3.1.1 SURVIVORSHIP…………………………………………………………………………………14 3.1.2 COVER……………………………………………………………………………………………..15 3.1.3 BIOMASS…………………………………….…………………………………………………..16 3.1.4 TREE SURVIVORSHIP…………………………………………..……………………………17 3.1.5 TREE HEIGHT……………………………………………………………..…………………….17 3.1.6 TREE BASAL DIAMETER…………………………………………………….………………17 3.2 OPTIMUM COLLIERY……………………………………………………………………………………20

3 3.2.1 SURVIVORSHIP…………………………………………………………………………………20 3.2.2 COVER……………………………………………………………………………………………..21 3.2.3 BIOMASS………………………………………………………………………………………….22 3.2.4 TREE SURVIVORSHIP………………………………………………………………………..23 3.2.5 TREE HEIGHT DIAMETER………………………………………………………………….23 3.3 SYFERFONTEIN COLLIERY…………………………………………………………………….………24 3.3.1 SURVIVORSHIP…………………………………………………………………………………24 3.3.2 COVER……………………………………………………………………………………………..25 3.3.3 BIOMASS………………………………………………………………………………………….26 3.3.4 TREE SURVIVORSHIP…………………………………………………………...... 26 3.3.5 TREE HEIGHT……………………………………………………………………………………27 3.3.6 TREE BASAL DIAMETER…………………………………………………………………….27

CHAPTER 4

DISCUSSION AND CONCLUSIONS ……………………………………………………………………………28 4.1 SURVIVORSHIP…………………………………………………………………………………………….28 4.2 COVER…………………………………………………………………………………………………………30 4.3 BIOMASS………………………………………………………………………………………………...... 31 4.4 TREE DATA…………………………………………………………………………………………………..31 4.5 RECOMMENDATIONS………………………………………………………………………………….33

CHAPTER 5

REFERNCES ………………………………………………………………………………………………………...……3 4

4 CHAPTER 1 LITERATURE REVIEW

1.1 Introduction

Coal is the world’s most abundant and widely distributed fossil fuel and it remains the primary energy source for several countries world-wide. In South Africa, coal mining makes a significant contribution to economic activity, development of sustainable job opportunities and foreign exchange earnings. The coal mining sector contributes 1.8% the South Africa’s GDP.

Coal extraction is essentially mined by two methods, namely underground and opencast method. Unfortunately, these are very destructive processes, and the environmental implications associated with this very serious. Unfortunately, highly potential agricultural lands, ecologically sensitive environments and surrounds are compromised for development, often resulting in loss of ecosystem value.

A large portion of coal reserves and operation on the Eastern Highveld is situated in the heart of the South African grassland biome. On a global scale, this biome is considered to be one of the most devastated, and the South African grassland biome has been identified as critically endangered (Olsen and Dinerstein, 1998). In South Africa, the grassland biome covers an area of approximately 349 174 km 2 (Neke and Du Plessis, 2004). Approximately 100 000 ha has already been transformed or destroyed by opencast and underground mining on the Eastern Highveld of South Africa (Neke and Du Plessis, 2004). According to Neke and Du Plessis (2004), this could increase to 325 081 ha with the amount economically mineable coal available in the area.

By law (Minerals and Petroleum Resources Act of 2002; National Environmental Management Act) opencast mines have to be rehabilitated and the post mining landscape returned to a sustainable land use. Although the objective of most

5 rehabilitation programs aim to restore land to its pre-mining agricultural land capability (Mentis, 2006) by establishing a pasture with fertilizer-responsive grass species on topsoil replaced topsoil. These pastures are made productive through defoliation management and fertilizer additions. After a few years, reversion to native grassland is opted for by withdrawing fertilizer application and applying defoliation management. However, this is a very slow process of secondary succession and often pre-mining ecological status is not achieved (Mentis, 2006).

1.2 Opencast Mining and Rehabilitation Method

The Vryheid Formation (Ecca Group) of the Karoo Sequence, which is present on the Eastern Highveld of South Africa, attains some 140 m at the thickest point and contains a number coal seam, of which four are considered to have economic potential. Mining this coal is dependent on the economic limit of the depth of over burden above the coal seam, which could reach up to 30 m, and the thickness of the underlying coal seam.

In order to access the coal, the material above the coal seam (known as burden material), is excavated and removed. Once the overburden is exposed, it is drilled, blasted and then removed. This material is placed such that it can be profiled, typically by dozer. The slope and depth of topsoil placed on the profiled burden material, ultimately determines the post mining land class capability for that area.

Before the overburden is removed, topsoil is stripped and is either stockpiled or is placed on profiled overburden material. The placed topsoil is then levelled, thus creating a surface for seeding, and later vegetation establishment.

The seed mix used for seeding typically comprises an annual species such as Eragrostis teff in combination with perennial species. Such species might include Chloris gayana, Cenchrus ciliaris, Cynodon dactylon, Digiteria eriantha, Eragrostis curvula, Eragrostis teff, and Medicago sativa (Mentis, 1999). The ratio of the seed

6 mix used for re-vegetation is usually specified in the mine’s Environmental Management Programme (EMP). 1.3 Soil Compaction

The process by which topsoil is stripped, stockpiled and placed on regarded burden material often results in severe compaction. This is detrimental to the physical, chemical and biological properties of the soil. Consequently, these soils have lower soil aggregate stability, lower infiltration rates, reduced water holding capacity, and a greater capacity to resist root extension (Chapman et al , 1994), all of which inhibit the potential for plant growth and establishment on the rehabilitated soil.

The major cause of soil compaction is trafficking of machinery on re-placed soil. This is further exacerbated by settling under gravity and (Haigh, 2000). As a consequence of this the particle-to-particle contact within the soil increases and the percentage of macro pores decreases (Haigh, 2000). This affects nutrient availability with de- nitrification a result of anaerobic conditions (Davies et al , 1995). Because of these changes, the soil becomes a less favourable environment for soil organisms reducing growth of surface vegetation (Haigh, 2000).

The soil chemical properties of the soil also deteriorate when topsoil is stockpiled. In these stockpiles, oxygen becomes limiting and anaerobic environment is created. As a result, large quantities of nitrogen are lost to the atmosphere as gaseous N 2 or N 2O, through the process of de-nitrification. Loss of nitrogen and other nutrients by leaching also occurs, reducing the capacity for vegetation establishment. Davies et al (1995) reported a 2600kgha -1 loss of nitrogen from reinstated topsoil from a stockpile.

Compaction is accelerated in the presence of percolating water especially following intensive rains (Haigh, 2000). This is often the case in stockpiled soil, which may be stockpiled for tens of years (Lipiec et al , 2003). When water percolates through the soil, the aggregates disperse and trapped air within the soil is displaced. As a result, the soil loses structure and after drainage, tight packing of the soil particles occurs

7 (Haigh, 2000). In addition to this, the soil may become waterlogged resulting in an anaerobic environment. This leads to increased anaerobic bacteria activity, which attack the organic materials that bind the aggregates together, thus lowering the stability of the soil, and increasing its potential for compaction (Haigh, 2000).

1.4 Soil Ameliorants

Substrates can be added soil to alleviate the severity of soil compaction. These might include sewage sludge, pine bark, earthworms, and microbes. Many studies have illustrated the use of these additives as ameliorants of soil compaction. Earthworms improve soil physical structure. Their burrowing activity results in the production of increased macro pores. This improves hydraulic processes in the soil, improves aeration (Tian et al, 2000) and can decrease the bulk density of a soil (Jascho et al, 1989; Whalley et al, 1995). Additions of pine bark have been reported to decrease then bulk density of a soil. Brown et al (1975). They showed that increased additions of pine bark to sand decreased the bulk density of the media. Illera et al (1999) showed a decrease in soil bulk density from 1.22cm -3 – 1.06gcm -3 with addition of municipal sewage sludge compared to a control soil.

8 CHAPTER 2 MATERIALS AND METHODS

2.1 Experimental Layout

2.1.1 Site Description

2.1.1.1 Kleinkopje Colliery

Kleinkopje Colliery is situated approximately 20km south of Witbank and is owned by Anglo American. The trial site (26 o00’S; 29 o12’E) was established on 21 March 2004 on topsoil prepared for seeding operations.

According to the mine’s EMPR, the average yearly rainfall is 696 mm. Summer temperature ranges between 12 oC to 29 oC, while winter temperatures range from - 3oC to 20 oC.

The dominant soils in the area are Avalon, Hutton, Glencoe, Mispah, Clovelly, and Wasbank.

2.1.1.2 Optimum Colliery

Optimum Colliery, now owned by Optimum Coal Holdings (PTY) LTD, is a coal mine situated 30 km south east of the town Middelburg. The trial site (25 o59’S; 29 o37’E) was established on 20 February 2004 on topsoil prepared as part of the rehabilitation program.

The area receives an annual rainfall of 682 mm with a mean maximum temperature of 22.5 oC and mean minimum temperature of 7.7 oC.

The dominant soils in the area are Hutton, Clovelly, Glencoe, Avalon, Fernwood, Kroonstad and Glenrosa (Lachenicht, 2005).

9 2.1.1.3 Syferfontein Colliery

Syferfontein Colliery is a Sasol owned coal mine operating an opencast and underground section. It is situated 20 km south east of Secunda in the Mpumalanga Province (Republic of South Africa). The trial site (26 o27’S; 29 o16’E) was established on 20 March 2004 on topsoil placed on profiled spoil that formed part of the rehabilitation program.

The area receives 689 mm rainfall per annum with an average summer temperature ranging between 10 oC and 30 oC, with an average temperature of 20 oC. Average winter temperature varies between -3oC and 21 oC.

The soil in the area is generally a heavy clay soil (55%) with an average bulk density of 1.4 Mg m -3 (Beletse, 2004).

2.2 Experimental Design 2.2.1 Trial Establishment

The trial was established at Optimum colliery on 20 February 2004. Planting at Syferfontein Colliery and Kleinkopje Colliery was postponed until 20 March following intensive rains and subsequent waterlogged soil at the trial sites.

The trial was setup as a random bock design, with plugs grown in 5 m x 5 m plots. In each plot, 272 plugs were planted at 18 cm intervals. The trial layout at the various sites is given in Figure 1.

10 Kleinkopje Colliery Optimum Colliery Syferfontein Colliery

H T Ct Ct T Ht C Tt C

Tt Tt C CHC H Ct Ct

Ht T H Ht H C HTH

Ht Tt Ct T Tt Ht Ht Tt Ht

T Ht Ct Ct T Ct Ht T C

CCH H Tt Tt T Tt Ct

AAA AAA AAA

Figure 1: A diagram of the trial set up at Kleinkopje Colliery, Optimum Colliery, and Syferfontein Colliery. Refer to Table 1 for abbreviations.

Table 1: A key of abbreviations for the different species and treatments used in Figure 1.

Key T Themeda triandra No fertilizer Tt Themeda triandra With fertilizer H Hyparhennia hirta No fertilizer Ht Hyparhennia hirta With fertilizer C Cynodon dactylon No fertilizer Ct Cynodon dactylon With fertilizer A Acacia sieberana With fertilizer

11 2.2.2 Species

Three native species were used in the trial namely Themeda triandra , Hyparrhenia hirta and Cynodon dactylon . Two treatments were applied, one with fertilizer and the other without. Each treatment and species was replicated three times (refer to Figure 1).

25 Acacia sieberana trees were planted in three tree 6m x 6m plots at 1.5m spacing. Each plot was treated with a fertilizer application.

The plugs and trees were raised at Topcrop Nursery, which is situated 30 km East of Pietermaritzburg. These plugs were transported to the three collieries and planted.

2.3 Trial Setup 2.3.1 Planting

Holes were dug at 18 cm interval, in which a plug was inserted. Prior to placement, the hole was filled with hydrated tera-sorp, a powder that forms a thick gel when hydrated, and which enhances establishment of plugs and seedlings by supply of water during the first two weeks of establishment. The roots of the plug were also dipped in the tera-sorp solution prior to planting.

2.3.2 Fertilizer Application

Soil samples from each site were taken in November 2003. These samples were sent to Cedara Soil Research Laboratories and a fertilizer recommendation given. Prior to planting, each treated plot received an application of fertilizer which was broadcasted by hand. Using a rake, this fertilizer was then worked into the soil to a depth of 3 cm – 5 cm. The amount of fertilizer applied at each site is given in Table 2 and Table 3.

12 Table 2: Fertilizer application for Kleinkopje Colliery and Optimum Colliery.

Fertilizer kg/ha kg/plot Lime Ammonium Nitrate 1200 3 Diammonium Phosphate 90 0.225 Potassium 210 0.525

Table 3: Fertilizer application for Syferfontein Colliery.

Fertilizer kg/ha kg/plot Lime Ammonium Nitrate 1200 3 Diammonium Phosphate 280 0.700 Potassium 125 0.313

2.3.3 Maintenance

Once the trial was established, the trial was left to its own devices. Irrigation was supplied by rainfall. Weed control at the three sites was conducted in March 2005, where weeds were physically removed by hand. Kleinkopje Colliery received additional weed removal in March 2006. The other sites did not receive this additional activity.

2.4 Field Measurements

Measuring and sampling at did not necessarily occur at the same time owing to constraints by the mine and by the research team. Constraints included decline in access to the mine. The various sampling dates are given in Table 4.

13 Table 4: A schedule indicating the dates that the various trials were sampled.

Colliery Key Date Kleinkopje Optimum Syferfontein March 2004 Sampled November 2004 April 2005 Not April 2006 Sampled June 2007

2.4.1 Survivorship

Survivorship was measured by counting the number of plugs in each plot, dividing by 272 and expressing as a percentage. During sampling, wilted plugs were not counted as ‘survived’.

2.4.2 Cover

Basal cover was assessed using two different methods depending on the growth morphology (i.e. tufted and stoloniferous growth forms) of the grass being assessed. Basal cover of the tufted growth forms (i.e. Themeda triandra and Hyparrhenia hirta ) was measured once the plugs had been harvested. Using a measuring rule, the diameter of the exposed tuft was measured. Two measurements were taken, one along the head axis, and another along the body axis of the plot. Plots were divided into four quadrants and measurements were taken from 10 random samples within each quadrant. This was then expressed as a percentage cover over the entire plot. A photo illustrating measuring the diameter of a Themeda triandra tuft is depicted in Figure 2.

For the stoloniferous growth form (i.e. Cynodon dactylon ), a 30 cm x 30 cm quadrat with nylon string strung from corner to corner to form a ‘cross hair’ was placed at the centre of the plug. The percentage area in each sub quadrant of the quadrant was then estimated and recorded. Forty random samples were taken from each plot. This was then expressed as percentage cover of the plot.

Figure 2: A photo of basal diameter measurement of a Themeda triandra tuft.

2.4.3 Biomass

At the end of each growing season, each plot was harvested. Using a pair of shears, each plug within the plot was cut approximately 10 cm from above the ground surface. All above ground matter was collected and placed into 9 litre potato bags. These bags were then transported from the mine and placed in a drying oven for a period of 48 hours at 70 oC at the Anglo Coal Environmental Services laboratories.

Once the bags had been oven dried, they were allowed to equilibrate to room temperature over a period of 24 hours. Thereafter, each bag containing oven dried material was weighed. Next, the material was removed from the bag and the bag weighed separately. The difference between the bag holding the dry material and the empty bag represented the biomass produced. All biomass figures in each plot were summed and expressed in g ha -1. A photo of a cropped trial at Optimum Colliery is given in Figure 3.

Figure 3: A photo illustrating a trial harvest at Optimum Colliery.

2.4.4 Tree Survivorship

Each tree that survived was counted. These were totalled and divided by 75, and expressed as a percentage.

2.4.5 Tree Height

Using a steal taped tape measure, each tree was measured from the ground surface to the highest point on the tree. After each winter, and once the trees had re- coppiced, the same measuring principle was applied. A picture illustrating measuring is shown in Figure 4.

Figure 4: Photos showing tree height measuring at Optimum Colliery.

2.4.6 Tree Basal Diameter

Using a pair of vernier callipers, the diameter of each tree was measured approximately 5 cm from the ground surface.

17 CHAPTER 3

RESULTS

3.1 Kleinkopje Colliery

3.1.1 Survivorship

Figure 5: Plug survivorship at Kleinkopje Colliery. Refer to Table 1 for abbreviations.

Cynodon dactylon achieved 100% survivorship throughout the duration of the trial for both treated and untreated plots.

Treated Hyparrhenia hirta decreased from 100% to 44% over the four seasons. However, survivability remained constant around 60% for three season (2004 -2006) but this decreased by 20% in 2007.

Both treated and untreated Themeda triandra behaved similarly in that survivability decreased from 100% to about 65% from the first to the second season. However, both treatments were able to recover to 80% and 87% respectively by the end of the trial period.

3.1.2 Cover

Figure 6: Cover percentage at Kleinkopje Colliery. Refer to Table 1 for abbreviations.

Overtime, both untreated and treated Cynodon dactylon attained 100% cover. In the second season, untreated Cynodon dactylon attained 86% cover, and by the third season cover had levelled off at 100%. Treated Cynodon dactylon had a 98.75% cover in the second season and reached 100% in the following season.

Hyparrhenia hirta within the untreated plots covered 1.73% in the second season of the trial and increased to 2.75% in the following season. 2.65% was recorded in the final season of the trial period. Treated Hyparrhenia hirta achieved a maximum cover of 7.51% in the third season from a first season measurement of6.19%. Cover subsequently decreased to 4.09% in the fourth season.

Themeda triandra cover within the untreated plots increased stepwise year on year, from 1.61% in the second season, to 3.41% in the final season (2007). Maximum cover of 4.36% for treated Themeda triandra was achieved in the third season of the

19 trial period from an initial cover of 3.64%. Cover decreased to 3.86% in the final season (2007).

3.1.3 Biomass

Figure 7: Biomass production at Kleinkopje Colliery. Refer to Table 1 for abbreviations.

Treated Cynodon dactylon produced more above ground year on year compared to untreated plots. The biomass produced from the untreated Cynodon dactylon plots reached a maximum of 74.66 g m-2 in the 2007 season, from an initial 49.13 g m-2 in 2005. Treated plots decreased overtime from 443.73 g m-2 produced in 2004 to 174.47 g m-2 in 2007.

Biomass more than doubled in year 2 from 393.59 g m-2 to 961.40 g m -2, but reduced to 419 g m -2 in the third season. Untreated Hyparrhenia hirta in 2005 measured 176.71 g m-2. This increased to 508.58 g m-2 in 2006. However, this decreased to 444.85 g m-2 in 2007.

20 Treated Themeda triandra increased year on year, with the second harvest producing three times more material than the first (64.77 g m -2 to 248.32 g m -2). Aboveground biomass produced in the third harvest increased slightly from the second, with 248.32 g m -2 being produced. Untreated plots increased from 42.27 g m-2 to 206.71 g m-2 to 199.10 g m-2 during the trial duration.

3.1.4 Tree Survivorship

Tree survivorship at Kleinkopje Colliery remained fairly consistent throughout the trial period. In the last season, tree survivorship measured 97.33%. Survivorship dipped to 97.33% in September 2005, and it this it remained for the next two years.

3.1.5 Tree Height

The average tree height increased from 42.79 cm to 172 cm at the end of July 2007. In the two seasons after this there was no significant increase in height, however, in the fourth and fifth seasons, there was a substantial increase in tree height with trees averaging 172 cm.

3.1.6 Tree Basal Diameter

The same relationship exhibited for height over time is shown for tree diameter. In the first two seasons, the diameter of the trees hovered between 0.48 cm and 0.65 cm. However, over the next three seasons the tree diameter increased significantly from 0.65 cm (March 2005) to 2.17 cm (September 2005) to 4.67 cm (August 2006) to 3.67 cm (July 2007).

Figure 8: Tree survivorship at the Kleinkopje Colliery, Optimum Colliery, and Syferfontein Colliery.

Figure 9: Tree height at the Kleinkopje Colliery, Optimum Colliery, and Syferfontein Colliery.

Figure 10: Tree diameter at the Kleinkopje Colliery, Optimum Colliery, and Syferfontein Colliery.

23 3.2 Optimum Colliery

3.2.1 Survivorship

Figure 11: Plug survivorship at Optimum Colliery. Refer to Table 1 for abbreviations.

Cynodon dactylon was able to record 100% survivability by the end of the trial period for both treatments. At the end of the first season, survivability decreased to 77% and 85% for untreated and treated plots, however, both treatments increased to 100% the following season, and it remained that way for the duration of the trial.

Hyparrhenia hirta decreased overtime from 100% in the first season to 28% and 22% for untreated and treated plots. A drastic drop of 40% and 60% for untreated and treated plots occurred after the first winter. Thereafter, species died off at a much slower rate, with a 28% and 22% survivorship being recorded at the end of the trial period.

Resultant survivorship was much higher in untreated Themeda triandra (51%) than was for treated Themeda triandra (32%). A severe decrease was exhibited after the first winter. Untreated species decreased to 65% and treated Themeda triandra

24 decreased to 48%. Another severe drop in numbers was experienced in the second season where untreated Themeda triandra decreased to 43% and treated Themeda triandra 25%. Numbers remained consistent for two seasons, after which an increase in numbers occurred in the last season for both treatments (untreated 50%, treated 30%).

3.2.2 Basal Cover

Figure 12: Cover percentage at Optimum Colliery. Refer to Table 1 for abbreviations.

Both untreated and treated Cynodon dactylon plots achieved 100% cover throughout the duration of the trial.

Untreated Hyparrhenia hirta plots achieved maximum cover of 3.29% in the third season of the trial, up from 1.98% in the second season of the trial. Cover measured in the final season of the trial was 2.18%.

Cover in the untreated Themeda triandra plots increased stepwise from 1.98% in 2005 to 2.51% in 2006 to 3.04%. Treated Themeda triandra increased year on year from 1.03% in 2005 to 1.80% in 2007.

25 3.2.3 Biomass

Figure 13: Biomass production at Optimum Colliery. Refer to Table 1 for abbreviations.

Treated Cynodon dactylon plots achieved a higher aboveground biomass year on year compared to the untreated plots. Production produced in the untreated plots decreased overtime from 199.71 g m-2 in 2005 to 126.70 g m-2 in 2007. Production in the treated plots peaked after the second harvest at 358 g m-2 up from 296.13gm-2 in 2006. Biomass reduced to 288.14 g m-2 in the third season.

Untreated and treated Hyparrhenia hirta plots showed similar biomass production trends. Production for both treatments peaked after the second harvest with 145.81 g m-2 and 358.71 g m-2 produced for untreated and treat plots respectively, up from 237.99 g m-2 and 235.072 g m-2 after the first harvest. Biomass production decreased after the final harvest to 187.29 g m-2 and 228.86 g m-2.

Untreated Themeda triandra increased from 60.31 g m-2 in 2005 to 302.77 g m-2 in 2006, but decreased in 2007 to 204.19 g m-2. Biomass produced under treated plots increased year on year from 50.71 g m-2 in 2005 to 135 g m-2 in 2007.

26 3.2.4 Tree Survivorship

Tree survivability at Optimum decreased form 96% in the first season to 78.66% in the fifth and final season. An annual 10% loss of trees was experienced from 2004 and 2005, with a 77.33% being recorded at the end of 2005. This remained consistent into the next season with a final 78.66% survivorship being.

3.2.5 Tree Height

Over the first three seasons tree height remained fairly consistent, decreasing only slightly from 47.28 cm to 43.44 cm. However, in the season of 2006, tree height increased significantly to 108.08 cm and a final height of 119.59 cm was recorded in the final season (2007).

3.2.6 Tree Basal Diameter

Basal diameter remained relatively low during the first three seasons, ranging from 0.61 cm to 0.91 cm. In the fourth season, basal diameter increase considerably to 2.12 cm. However, in the final season the basal diameter decreased to 1.58 cm.

27 3.3 Syferfontein Colliery

3.3.1 Survivorship

Figure 14: Plug survivorship at Syferfontein Colliery. Refer to Table 1 for abbreviations.

Both untreated and treated Cynodon dactylon attained 100% survivability by the end of the trial period. However, both treatments experienced a decrease in survivorship after the first winter, but increased to 100% by 2005.

Hyparrhenia hirta achieved 44% and 45% survivability by the end of the trial period. Numbers did not decrease radically after the first winter period with only a 4% and 2% decrease recorded for untreated and treated treatments. Untreated Hyparrhenia hirta decreased substantially over the next three seasons with 75% recorded at the end of 2005, and 45% by the end of 2006. Treated plots decreased significantly from 2004 to 2005, with a 50% decrease recorded. Survivorship remained consistent thereafter, with a similar survivability was measured in the final season.

28 Untreated and treated Themeda triandra decreased to 38% and 25% respectively by the end of the trial. After the first winter Themeda triandra had decreased by 12%. By the third season, survivability decreased to 55% and 71% for untreated and treated plots respectively, after which a further decrease to 35% and 25% occurred in the final season.

3.3.2 Cover

Figure 15: Cover percentage at Syferfontein Colliery. Refer to Table 1 for abbreviations.

Cover in the both untreated and treated Cynodon dactylon plots maintained 100% for the two seasons it was measured.

Untreated Hyparrhenia hirta increased from 6.84% to 7.01% from 2004 to 2005. Treated Hyparrhenia hirta plots increased from 4.87% to 4.17%.

Themeda triandra decreased in cover over the two seasons for both treatments. Untreated Themeda triandra decreased from 3.98% to 2.38% from 2005 to 2006.

29 Treated Themeda triandra plots decreased from 4.31% to 1.70% during the same period.

3.3.3 Biomass

Figure 16: Biomass production at Optimum Colliery. Refer to Table 1 for abbreviations.

Treated plots showed a higher biomass production compared to untreated plots for all species. Treated Cynodon dactylon produced 505.17 g m-2 compared to 216.17 g m-2 in the untreated plots. Treated Hyparrhenia hirta produced 902.19gm-2, while untreated plots produced 654.81 g m-2. Treated Themeda triandra produced 171.06 g m-2 with 163.58 g m-2 produced from the untreated plots.

3.3.4 Tree Survivorship

Survivorship decreased to almost half, from the first to the final season (100% to 56%). The trees suffered a 4% loss after the first winter spell, after which there was a major drop of 17% in the second season. Another substantial decrease of 25% occurred in the final season, reducing survivability to 56%.

30 3.3.5 Tree Height

In the first three season of growth, tree height did not increase much. Initially, a tree height of 38cm was recorded. This decreased to 20 cm in the second season, and then attained a height of 37cm in 2005. However, in the fourth season, the trees grew by 100 cm to attain a height of 137cm.

3.3.6 Tree Basal Diameter

Over the four seasons, tree diameter increased from 0.58 cm to 0.95 cm.

31 CHAPTER 4 DISCUSSION AND CONCLUIONS

4.1 Survivorship

The main objective for establishing vegetation on restored soils of mined areas is to create a cover against soil erosion by wind and rain (Tanner, 2007). A major factor in achieving this is to firstly get vegetation to establish, and thereafter ensure that the cover remains sustainable over time.

In this study, Cynodon dactylon exhibited the highest survivability with 100% achieved throughout the trial period regardless of fertilizer additions. Themeda triandra performed well at Kleinkopje Colliery under both treatments attaining 87% and 80% survivorship for untreated and amended treatments. However, Themeda triandra did not perform well at Optimum and Syferfontein collieries for both treatments, attaining only 28% and 22% respectively at Optimum Colliery and 35% and 25% at the Syferfontein site (refer to Figure 5, 11 and 14).

The stoloniferous growth form of Cynodon dactylon may have favoured the success over the tufted growth forms of Hyparrhenia hirta and Themeda triandra , as the network radiating from the central planting point may have been able to attain more nutrients available in the soil and from the fertilizer applied.

Interestingly, Themeda triandra performed better in the untreated plots than in the fertilizer amended plots, and indicates that this species favours lower fertility environments on reclaimed soil. This is consistent with Le Roux and Mentis (1986) work conducted at the University of Kwa-Zulu Natal’s Agricultural research farm, uKulinga, where they showed that Themeda triandra responded poorly to nitrogen fertilizer application.

32 In a study conducted Baer, Blair, Collins and Knapp (2004), the affect of three fertility three levels of nitrogen availability (ambient, enriched, and reduced fertilization) on species diversity and richness response was measured. The study revealed that total diversity and richness declined over time in the ambient nitrogen and enriched nitrogen, but increased in the reduced nitrogen soil in the second and third year of the study.

Hyparrhenia hirta performed the poorest at all the sites except at Syferfontein. An interesting point to note is the increase in survivability in the last season in the untreated plots at Kleinkopje and Optimum sites, as well as the treated site at Syferfontein. This was attributed to the ability of this species in the said plots to ‘self-seed’. Masses of seed are produced after it flowers from September to March (van Oudshoorn, 1999), were able to germinate and establish, and in so doing, increased the ‘survivability’ (Figure 17).

Figure 17: A photo illustrating the ‘self-seeding’ effect of Hyparrhenia hirta at Kleinkopje Colliery.

The poor survivability of the Hyparrhenia hirta and Themeda triandra may also be attributed to weed infestation, especially at the Optimum and Syferfontein sites where only once weed control was undertaken as compared to two at Kleinkopje Colliery.

33 The low survivability of plugs at the three trial sites is not unique to survivability on restored soils. In a study carried out by Harwood, Hacker and Mott (1999) at Saraji mine in Queensland Australia, almost half of the seedlings that had emerged from seeded topsoil, died after two weeks. Seven weeks after seedling emergence, the highest survivability achieved in the study was only 44%.

4.2 Cover

Generally, treated plots showed a higher basal diameter than untreated plots at the various sites. However, at the Optimum site Themeda triandra showed better basal cover in 2006 and 2007 than its treated counterpart at Optimum Colliery. Hyparrhenia hirta achieved better basal cover for treated plots at Kleinkopje Colliery and Optimum Colliery throughout the trial period. An isolated case of better greater basal cover of Hyparrhenia hirta occurred in 2006 at Syferfontein.

Basal cover as a measure of determining the effectiveness of a cover against soil protection can be used in isolation. Basal cover of the individual species expressed as a cover of the entire plot is more valuable in determining the effectiveness of a cover. This was achieved by multiplying the average basal cover recorded by the number of plugs survived in each plot, and expressed a percentage.

Cynodon dactylon demonstrated the 100% cover by the end of the trial at all the sites. Cynodon dactylon success as a cover compared to Themeda triandra and hyparrhenia hirta may be attributed to its growth form. Cynodon dactylon has a stoloniferous growth form, whereby lateral shoots grow along the soil surface. The main apex of the lateral stem elongates indefinitely as nodes, with roots and shoots developing at these nodes (Tainton, 1999). As growth is continuous, a resultant network of stolons and shoots radiating from the central planting point and this creeping effect allows for a greater area of the soil surface to be covered. However, in the tufted species, roots grow to depth in the soil, and even though tillering did occur after the first harvest (increase in basal diameter), the extent of this did not result in the cover achieved by Cynodon dactylon .

Ultimately, survivability has the greatest influence on cover when comparing the tufted species. Generally, better survivability results in better cover. At Kleinkopje Colliery, treated Hyparrhenia hirta showed best cover by the end of the trial period of 4.09% compared to 2.66% of untreated Hyparrhenia owing to greater survivorship of 43.75% (treated) compared 31% (untreated).

Themeda triandra showed better cover in the untreated plots at Optimum throughout the trial period, owing to approximately 40% higher survivability year on year of the untreated plots compared to treated plots. This trend occurred at both the Syferfontein and Kleinkopje sites (refer to Figure 6, 12, and 15).

4.3 Biomass

Biomass production was generally greater in treated plots compared to untreated plots. This is especially so for Cynodon dactylon plots across all the sites, where the yield year on year was greater in treated plots compared with untreated plots. This is consistent with research conducted by Longhurst and O’Connor (1999) in the Waikato coal fields, where they showed that relative yields increased with increased fertilizer additions. Relative yields of 72%, 100%, 126% and 147% were produced from 250, 500, 1000, and 2000 kg ha -1 fertilizer additions.

In an experiment conducted by Ebelhar, Barnhisel, Akin and Powell (1982) at a site in Western Kentucky, the effects of lime, N, P, and K fertilizer amendments on bermudagrass growth and development was tested. Results showed that dry matter yields increased significantly with each additional increment of nitrogen applied. 0 kg Nha-1 produced 371 kg ha -1; 50 kg Nha -1 produced 537 kg ha -1; and 100 kg Nha -1 produced 834 kg ha -1.

4.4 Tree Data

35 Tree survivability only proved successful at Kleinkopje Colliery with 97% survivability by the end of the trial period. Survivability at Optimum Colliery and Syferfontein Colliery did not prove very successful with 79% and 56% recorded at the end of the study. Poor survivorship at the Optimum and Syferfontein sites could be attributed to the high incidence of frost that occurs at these sites. Not chemically treating the area for weeds may also have contributed to the lowered survivability of the trees.

Other studies have also demonstrated the difficulty in establishing trees on reclaimed mine soils. In a 12 year study conducted by Chaney et al (1995), it was demonstrated that the most rapid decline in seedling survival occurs during the first four years after planting. It also showed that survival continues to decline gradually thereafter.

Treatment of weeds in tree rows is vitally important to the success of trees. Chaney et al (1995) reported that chemical control of ground cover in the first two years of seedling establishment was the most important factor that influences seeding survival. Their study indicated that after 12 growing seasons on a mined site, black walnut and northern red oak survival was 61% and 39% respectively with chemical plant-control. Without chemical plant control, these two trees showed a survivability of 2% and 0.2% after 12 growing seasons.

This could be attributed to the high incidence of frost experienced at the various sites as well as and cold winter temperatures. Over the first three growing seasons, although tree height was low, the roots might have stabled well which allowed for eventual growth in the fourth season.

Soil condition resulting from soil bed preparation also has a major influence on tree survival and performance. In a study conducted by Conrad et al (2002), soil compaction as a result of topsoil placement for seedbed preparation, was shown to be most detrimental for establishment and survivability of trees. The study indicated that with an increase in bulk density, tree-survival rate decreases. Data from the study showed that when dry bulk density in the top 50mm of the soil was greater

36 than 1723 kg m-3, tree survivability averaged less than 50%. This report does not indicate any soil data from the sites, but it can be assumed that high compaction as a result of current topsoil placement practice would have influenced the survivorship of the trees.

4.5 Recommendations

Planting plugs as a vegetative option on mined out land is too expensive and impractical if applied to the vast areas that area mined out throughout the life of a coal mine. However, there might be application for re-vegetation technique, especially in areas inaccessible to planters, and in ecologically sensitive areas.

In areas that are inaccessible to tractor and planters, such as on steep coal dumps and protection berms, plugs can be planted by hand. Cynodon dactylon appears to be the species of choice for this owing to its effective creeping ability and survivability. This species is able to establish cover very quickly and would reduce the potential of erosion in steep areas.

Themeda triandra and Hyparrhenia hirta could be used in establishing buffers between ecologically sensitive areas and rehabilitated areas. Because these species don’t spread aggressively compared to species used in rehabilitation seed mixes, these buffers would prevent or reduce current pasture grasses from intruding into such areas. This practice could form part of a biodiversity management plan.

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