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THE LONG-TERM EVALUATION OF RESTORATION TECHNOLOGIES APPLIED

IN THE EASTERN UPPER KAROO (MIDDELBURG, EC)

 

L. van den Berg

 

Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg EC, 5900

E-mail: Loraine vd Berg 



INTRODUCTION

Vegetation changes generally occur unpredictably in the short-term (years) in response to rainfall, and episodically in the long-term (decades) in response to rare events, or due to grazing pressure, climatic changes, altered disturbance regimes or a combination of these factors (Darkoh, 1996; Hoffman et al., 1990).  The complex dynamics of arid and semi-arid ecosystems and especially the mismatch between observation times (years) and time scales of vegetation change (centuries) make it extremely difficult to fully understand their long-term dynamics.  Therefore it is difficult to establish whether an area is undergoing progressive, long-term decline in biodiversity and productivity, or whether it is merely suffering from short-term drought, from which the land may recover.  Before developing management strategies for unsustained animal production and species conservation and diversity, it is necessary to know how resilient arid and semi-arid ecosystems really are, and to assess their potential to recover from serious natural or human induced disturbances or stress (UNCCD, 1995).

 

Realising that the conservation of existing ecosystems is simply not enough to ensure the future of living populations, and that degraded systems will not recover by natural successional processes in arid and semi-arid systems, the restoration of rangelands has become an absolute necessity (Friedel, 1991; Kellner & Bosch, 1992; De Wet, 2001).  Restoration ecology deals with the scientific and ecological background of natural management practices aiming at the re-establishment of locally extinct species.  According to the Society of Ecological Restoration (SER), ecological restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged or destroyed (SER, 2002).  In most cases the general aims of restoration is to increase the biodiversity for higher resilience, increase the vegetation cover to combat erosion and to increase the production potential for higher grazing capacity (Bakker et al., 1996). 

 

Rangelands which have retrogressed beyond a certain threshold and cannot recover by passive technologies, such as the resting from utilisation or the implementation of better grazing strategies, can only be restored by active methods (Snyman, 2003).  Active restoration technologies include cultivation, with or without re-vegetation practices, together with soil disturbance technologies, such as rip ploughing (Allen, 1995; Collins, 2001).  It is generally accepted that compacted substrates must be de-compacted to allow better water infiltration into the soil and therefore water availability for the roots of germinating plants (Montalvo et al., 2002).  Germination of seeds and establishment of seedlings are also enhanced in such a way.  These restoration practices, which include cultivation methods, might also enhance the establishment of species by exposing the dormant seeds in the seed bank to favourable light and aeration conditions, as well as increasing water infiltration rates for better root growth and development (Bakker & Berendse, 1999).  The restoration of the original soil condition and plant communities may be enhanced by the modification of soils and the introduction of species as seeds or plants belonging to the original plant community (McDonald et al., 1996). 

 

Passive restoration technologies entail the removal of the stresses that caused the original land degradation, such as heavy grazing and then allowing natural succession to take place (Milton & Dean, 1995; Whisenant, 1995).  Passive restoration will allow for resting to facilitate seeding, seedling establishment and/or the restoration of stored carbohydrate reserves in desirable plant species.  Resting is also recommended to accumulate fodder reserves to be used during the dormant season or in droughts (Van Heerden, 2002).  The optimum resting period will depend on the range type and condition, environmental and growing conditions, as well as climatic factors (Gambiza, 1996).

 

The aim of this project was to evaluate the longer term effect of active and passive restoration technologies applied in the Eastern Upper Karoo (Middelburg, EC), with special reference to vegetation changes in an established restoration site. 

 

MATERIALS AND METHODS

Study site location

The restoration plot was established on the farm Thornsprings which is situated 25 km south-east of Middelburg in the Eastern Cape Province of South Africa (31°40'00" S and 25°06'00" E).  The study site is situated in the Eastern Upper Karoo (Mucina & Rutherford, 2006) and is characterised by so-called "brak kolle" (brackish or saline patches).  The salinisation of the soil usually causes a decrease in vegetation cover, loss of topsoil, decreased water infiltration and the formation of hard crusts, which increases the rate of erosion and reduces the establishment of seedlings.  The area receives a long-term average rainfall of 347 mm per annum with the most significant rains falling in the summer months between October and April.

 

Experimental layout (design)

The restoration plot was established in November 1999.  A site of 150 m x 50 m was selected in a bare, denuded area on a highly compacted saline patch, with no or very little vegetation cover. The site was fenced to exclude any grazing by large herbivores.  The area was subdivided into 10 m x 10 m (100 m2) sub-plots and different restoration treatments were randomly applied in each sub-plot (Table 1; Figure 1).  At least three replications of each treatment were applied, resulting in 74 blocks. 

 

Restoration treatments

Brush-packing (B) included the covering of the experimental site with branches of woody vegetation to a height of 0.5 m.  Branches from the spiny Acacia karroo Hayne (Sweet thorn) tree that invades the riverbanks near the study area were used.

 

The application of organic material (O) involved the spreading of cow and horse manure (dung) at a rate of approximately 88 kg/100 m2 on each experimental sub-plot receiving the organic material treatment.  The application of organic material does not only potentially increase the carbon content of the soil, but could also help in the aeration and retention of water of the degraded soil.  Addition of organic material also increases the establishment and growth rate of over-sown and existing plants (De Wet, 2001; Van der Merwe, 1997).

 

The rip plough treatment (R) implies a cultivation action with a one-tine sub-soiler implement (ripper) to a depth of at least 200 mm and 100 mm wide.  The ripping action was used to break the hard, compacted crust of the surface soil in the bare patches and to create furrows in order to increase the water infiltration and root moisture and promote seedling establishment.

 

After consultation with local farmers, a combination of grass and shrub species were selected for the over-sowing treatments (S).  Seeds of perennial, large tufted and palatable grass species were selected for the over-sowing trials, i.e. Chloris gayana Kunth (Rhodes grass), Digitaria eriantha Steud. (Finger grass), Eragrostis curvula  Nees (Love grass) and Themeda triandra Forssk. (Red grass).  With the exception of T. triandra all the other species originated from commercial pasture seed in an area in a high rainfall zone.  Seeds from T. triandra were collected in two different rainfall zones.  The first was a T. triandra ecotype collected locally, near the study site in the Middelburg area and the second a T. triandra ecotype collected in a much higher rainfall zone near Potchefstroom (500 – 600 mm/a).  Seed of dwarf shrubs that was used in the over-sowing trials, included species which occur naturally in the area, i.e. Eriocephalus ericoides Druce (Kapok Bush) and Tripteris sinuata Norl. (Bietou).  It is advised to make use of indigenous, locally adapted ecotypes of species, but since seeds of these species are often not available in large quantities and the harvesting of local seed is very time consuming and costly, commercial seed which is readily available is often used in over-sowing practices.  The over-sowing took place at a rate of 120 g/species/100 m2 for all of the species. 

 

The combinations of all the restoration treatments including the control (C), together with their abbreviations, are given in Table 1.

 

Table 1. Summary of restoration treatments applied at the study site, with abbreviations

Restoration treatment

Abbreviations

Control – no treatment

C

Brush packing

B

Organic material

O

Ripping

R

Ripping & organic material

RO

Ripping & over-sowing with commercial Themeda triandra seed

RSCT

Ripping, over-sowing with local Themeda triandra seed

RSLT

Ripping & brush-packing

RB

Ripping, brush-packing, organic material & over-sowing with commercial Themeda triandra seed

RBOSCT

Ripping, brush-packing, organic material & over-sowing with local Themeda triandra seed

RBOSLT

Ripping, brush-packing & over-sowing with commercial Themeda triandra seed

RBSCT

Ripping, brush-packing & over-sowing with local Themeda triandra seed

RBSLT

Ripping, organic material & over-sowing with commercial Themeda triandra seed

ROSCT

Ripping, organic material & over-sowing with local Themeda triandra seed

ROSLT

Ripping, brush-packing & organic material

RBO

Organic material & brush-packing

OB

 

 

 

 

 15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

A

7

6*

1

4

9*

1

7

6>

2

4

9>

1

4

8*

Gate

B

5

8*

1

11

10*

2

5

8>

1

5

10>

12

5

10*

3

C

7

6*

1

4

9*

1

4

6>

1

4

9>

1

4

4

1

D

4

9*

1

4

6*

1

4

9>

1

4

6>

2

5

8>

12

E

11

10*

1

5

8*

1

11

10>

1

5

8>

3

5

10>

3

 

Legend:

*     Potchefstroom Themeda triandra used in seed mixture

>    Middelburg Themeda triandra used in seed mixture

N    number of replicates per treatment

1    Control (N = 15)

2    Brush (N = 3)

3    Organic (N = 3)

4    Rip (N = 13)

5    Rip + Organic (N = 7)

6    Rip + Seed (N = 3*, N = 3>)

7    Rip + Brush (N = 3)

8    Rip, Brush, Seed + Organic (N = 3*, N = 3>)

9    Rip, Brush +Seed (N = 3*, N = 3>)

10   Rip, Organic + Seed (N = 3*, N = 3>)

11   Rip, Brush + Organic (N = 3)

12   Organic + Brush (N = 3)

 

Figure 1. Plot layout at the Middelburg study site showing the repetitions and different treatments applied

 

Data collection

The initial surveys were carried out near the end of the growing seasons of April 2000 and 2001.  The site was again surveyed in 2009 using similar data collection techniques to obtain comparable results.  The new results were combined with the previous results to compile a long-term data set for this restoration site. 

 

The relative abundance of grass and dwarf shrubs was measured in all the sub-plots by using the descending point technique.  A point was lowered at one meter intervals and rooted plants within a radius of 300 mm were recorded (Sutherland, 1996).  If no plant occurred within a radius of 300 mm, it was noted as bare ground.  A total of 50 points were recorded in each 100 m2 sub-plot and the percentage abundance of each species per treatment determined.  The cover abundance data for each sampling year were analysed by using a CA ordination (Correspondence Analysis) to indicate the association between seeded and non-seeded restoration treatments.  A PCA ordination (Principal Component Analysis) was used to determine the associations between species abundance in the restoration treatments at each of the sampling events (2001, 2002 and 2009).

 

RESULTS AND DISCUSSION

It is important to note that prior to establishment (August to October), little or no rain had fallen.  The first significant rain (12 mm) was however recorded in the week after completion of the restoration application.  The good rainfall that followed establishment of the trial in 2000 could have favoured the germination and establishment of the over-sown species as only a small amount of water is necessary for seedling germination and establishment in arid and semi-arid areas (Sutherland, 1996).  The total annual rainfall for the year 2001 was also higher than the long-term annual rainfall recorded in this area, which could have aided the establishment of vegetation.  The area has received rainfall higher than the long-term average for most of the years since 1999 (Figure 2).  This could have played an important role in vegetation establishment during natural successional processes. 

Figure 2.  Total annual rainfall (1999 – 2008) as well as average long-term rainfall (1900 – 2008) received at the experimental site

 

Frequency (abundance) of all species

A total number of 29 species was recorded in 2001, 21 in 2002 and 37 species in 2009.  This increase in species numbers from 2001 to 2009 can be explained by the fact that local non-seeded species have established in the seeded plots.  This could also be as a result of secondary dormancy of seeded species which was not broken during the initial establishment of the trial. 

 

The results from the 2001 and 2002 surveys indicated that none or very little of the over-sown dwarf shrub species established in the trial, but results from 2009 showed some establishment of these species (Figure 3).  In all three years D. eriantha and T. triandra showed the highest average abundance for all seeded treatments.  In 2001 and 2002, C. gayana and E. curvula also had relatively high abundances, while these two species seemed to disappear in 2009.  One possible explanation for this is the fact that C. gayana is classified as a weak perennial grass species which easily dies off when in competition with other climax perennial species (Van Oudtshoorn, 2002).  It might also be attributed to the seasonal rainfall impacts (non-equilibrium characteristics of these systems) during this specific survey season.

Figure 3Graphs indicating the frequency (abundance) of the sown-in species in the different treatments over the survey period

 

Correspondence Analyses (CA)

From the CA results of 2001 it is clear that of the treated plots, the largest difference occurred between the over-sown (seeded) and not over-sown (non-seeded) plots.  According to the first CA axis (X-axis) all the seeded plots are clustered towards the right and all the non-seeded plots to the left of axis 1 (Figure 4).  This indicates a definite difference in species composition between the seeded and non-seeded plots.  Two of the seed plots (Rip and Seed (local seed)) however, are lying very close to the centre of axis 1.  According to the second CA axis (Y-axis) some variation exists between the different non-seeded plots.  The figure also indicates that two of the non-seeded plots (Organic material and Brush-packing) were not associated with the non-seeded plots.

Figure 4.  Ordination showing the difference in cover abundance between seeded (●) and non-seeded (○) treatments in 2001

 

 

The CA ordination for 2002 shows very similar results to that of 2001 with the exception that one of the seeded plots (Rip and Seed (local seed)) is lying to the left of axis 1 (Figure 5).  This indicates that the species composition has changed to an extent where the association is much higher with the non-seeded plots.  The variance on the second axis (Y-axis) is much smaller than for 2001, causing the plots to group together. 

 

Figure 5.  Ordination showing the difference in cover abundance between seeded (●) and non-seeded (○) treatments in 2002

 

The CA ordination for 2009 shows the convergence of seeded plots (treatments) towards the non-seeded plots (treatments) (Figure 6).  This could be an indication that the natural successional processes have started causing more non-seeded (natural) species to establish in the seeded plots (treatments).  It could also be explained by the non-equilibrium effects of climate also impacting during this specific season.  The variance on the first axis (X-axis) has remained similar for all three of the survey years.  Similarly to 2001, some variance is seen between the non-seeded plots on the second axis (Y-axis) for 2009.  As was the case in 2001, two non-seeded plots (Organic material and Brush-packing) showed higher variance on the second axis and is clearly not associated with the non-seeded treatments.  This could possibly be explained by the fact that the trial area is slightly sloped in a westerly direction, causing higher moisture content in some of the Organic material and Brush-packing plots, resulting in a higher abundance of annual herbaceous species such as A. congesta.

Figure 6.  Ordination showing the difference in cover abundance between seeded (●) and non-seeded (○) treatments in 2009

 

Principal Component Analyses (PCA)

 

The indirect PCA ordination for 2001 indicated a strong positive association between treatments and seeded or non-seeded species (X-axis) (Figure 7).  It appears that species such as D. eriantha, T. triandra and E. curvula were the strongest associated with the Rip, Brush-packing and Seed treatment as well as the Rip, Brush-packing and Organic material treatments.  The Control species showed only a slight positive association with non-seeded species such as C. incompletes.  This is explained by the fact that in 2001 the Control treatment plots were characterised by a high abundance of bare ground and very little vegetation occurred in these plots.  The rest of the non-seeded treatments, however, showed a positive association with local non-seeded species such as A. congesta and E. obtusa.

Figure 7.  PCA ordination showing the species relative frequency by treatment association for the different sub-plots in 2001.  See Appendix A for abbreviations of species

 

The PCA ordination for 2002 showed very similar results to that of 2001 with a strong positive association between species such as D. eriantha, T. triandra and E. curvula and the Rip, Brush-packing, Organic Material and Seed treatments (Figure 8).  The strong positive association between non-seeded treatments and non-seeded species continued in 2002.  In addition, more vegetation established in the Control treatment resulting in a stronger association between the Control treatment and non-seeded species than observed in 2001.

Figure 8.  PCA ordination showing the species relative frequency by treatment association for the different sub-plots in 2002.  See Appendix A for abbreviations of species

 

In 2009 the seeded species were still very strongly associated with the seeded treatments and the non-seeded species with the non-seeded treatments (Figure 9).  It seems, however, that the association between the seeded and non-seeded treatments became stronger with regard to species relative frequency.  This is in concurrence with the results obtained from the CA ordinations.

Figure 9.  PCA ordination showing the species relative frequency by treatment association for the different sub-plots in 2009.  See Appendix A for abbreviations of species

 

CONCLUSION

The complex dynamics of vegetation change in semi-arid ecosystems makes it extremely difficult to understand the long-term restoration dynamics of degraded areas.  The results from this trial give some insight into the successional change of vegetation ten years after the implementation of different restoration technologies in the Eastern Upper Karoo.

 

The fact that good rainfall followed the establishment of the trial and the fact that the area received above average rainfall for the duration of the trial, could have favoured the germination and establishment of seeded and non-seeded species.  A total number of 53 species were recorded during the three years with an increase in the number of species during the 2009 survey period.  This was as a result of the fact that a number of local non-seeded species established in the seeded and non-seeded treatments after initial establishment of the trial.

 

Digitaria eriantha and Themeda triandra showed the highest abundance of all the over-sown species for the study period, while Chloris gayana and Eragrostis curvula had high abundances early in the trial period but seemed to disappear in 2009.  The shrub species (Eriocephalus ericoides and Tripteris sinuata) that was sown in, did not establish in the first years, but showed some establishment in 2009.

 

The results of the direct Correspondence Analyses (CA) of the various years indicated that the largest difference occurred between the seeded and non-seeded plots as a result of differences in species composition between these plots.  Some variance also existed between the species composition of the different non-seeded plots.  The 2009 CA results showed the movement of seeded plots towards the non-seeded plots.  This could be an indication that the natural successional processes, in combination with seasonal climatic events, have induced more non-seeded species to establish in seeded plots. 

 

The indirect Principal Component Analyses (PCA) showed strong positive associations between different treatments and specific seeded or non-seeded species.  The seeded species showed a positive association to the majority of the seeded treatments, while the non-seeded treatments were correlated to the local non-seeded species.  In 2009, however, it was observed that the association between the seeded and non-seeded treatments became stronger with regards to species relative frequency.  This concurred with results from the CA ordinations.

 

These results provide a clearer understanding of the long-term vegetation dynamics of restored areas in the Eastern Upper Karoo.  It also provides some insight into the most suitable species and treatments to be used for the restoration of degraded areas in similar environmental conditions.

 

REFERENCES

Allen, E.B., 1995.  Restoration ecology, Limits and possibilities in arid and semi-arid lands.  IN:  Roundy, B.A., McArthur, A.D., Haley, J.S. & Mann, D.K. 1995.  Proceedings:  Wild land shrub and arid land restoration symposium, 19 – 21 October 1993, Las Vegas. NV, General Technical Report, INT-GTR-315.

Bakker, J.P. & Berendse, F., 1999.  Constraints in the restoration of ecological diversity in grassland and heathland communities, Tree, 14(2), 63 – 68.

Bakker, J.P., Poschlod, P., Strydstra, R.J., Bekker, R.M. & Thompson, K.  1996.  Seed banks and seed dispersal: important topics in restoration ecology, Acta Botanica Neerlandica, 45(4), 461 – 490.

Collins, J., 2001.  Desertification,  Website:  http://botany.uwc.ac.za/Envfacts/ facts/desertification.htm

Darkoh, M.B.K., 1996. Combating desertification in Zimbabwe, Desertification Control Bulletin 13, 17 – 28.

De Wet, S., 2001. The dynamics of certain grass species used during the restoration of degraded semi-arid rangelands, M.Sc., Thesis, Potchefstroom University for Christian Higher Education, South Africa.

Friedel, M.H., 1991. Range condition assessment and the concept of threshold: a viewpoint, Journal of Range Management 44, 422 – 426.

Gambiza, J., 1996.  Rangeland management.  IN:  Smith, T. & Wangari, E.O., 1996.  Desertification control and natural resources management:  Case studies from SADC Countries, UNESCO, Dakar.

Hoffman, M.T., Barr, G.D. & Cowling, R.M., 1990. Vegetation dynamics in the semi-arid eastern Karoo, South Africa—the effect of seasonal rainfall and competition on grass and shrub basal cover, South African Journal of Science 86, 462 – 463.

Kellner, K.K. & Bosch, O.J.H., 1992. Influence of patch formation in determining the stocking rate for southern African grasslands, Journal of Arid Environments 22, 99 – 105.

Milton, S.J. & Dean, W.R.J., 1995. South Africa’s arid and semiarid rangelands: why are they changing and can they be restored? Environmental Monitoring and Assessment 37, 245 – 264.

McDonald, A.W., Bakker, J.P. & Vegelin, K., 1996. Seed bank classification and its importance for the restoration of species – rich flood meadows.  Journal of Vegetation Science, 7, 157 – 164.

Montalvo, A.M., McMillan, P.A. & Allen, E.B., 2002. The relative importance of seeding method, soil ripping, and soil variables on seeding success, Restoration Ecology 10(1), 52 – 67.

Mucina, L. & Rutherford, M.C., 2006.  The vegetation of South Africa, Lesotho and Swaziland, Strelitzia 19,  SANBI,  Pretoria.

Snyman, H.A., 2003. Revegetation of bare patches in a semi-arid rangeland of South Africa: an evaluation of various techniques, Journal of Arid Environments 55, 417 – 432.

Society for Ecological Restoration Science and Policy Working Group (SER)., 2002. The SER Primer on Ecological Restoration, Website: www.ser.org

Sutherland, W.J., 1996. Ecological Census Techniques, a handbook, Cambridge University Press, Cambridge.

United Nations Convention to Combat Desertification (UNCCD)., 1995. United Nations Convention to Combat Desertification in Those Countries Experiencing Serious Drought and/or Desertification Particularly in Africa, United Nations Environment Program, Geneva.

Van der Merwe, J.P.A., 1997. The development of a data base and expert system for rangeland reinforcement practices in southern Africa, M.Sc. Thesis, Potchefstroom University for Christian Higher Education, South Africa.

Van Heerden, M.C., 2002.  Changes in grass species composition and production systems:  A LandCare Initiative in the North West Province, South Africa,  M.Sc. Thesis.  Potchefstroom University for Christian Higher Education, Potchefstroom, South Africa.

Van Oudtshoorn, F.,  2002.  Gids tot die grasse van suider Afrika,  Briza Publikasies.

Whisenant, S.G., 1995.  Landscape dynamics and arid land restoration.  IN:  Roundy, B.A., McArthur, A.D., Haley, J.S. & Mann, D.K., 1995.  Proceedings:  Wild land shrub and arid land restoration symposium, 19 – 21 October 1993, Las Vegas, NV, General Technical Report, INT-GTR-315.

 

APPENDIX

 

Appendix A – Complete list of species with their desirability classes / ecological classification and grazing value.

 

Species

Abbreviation

Desirability class

Ecological classification

Grazing Index Value

Dwarf and woody shrubs

Atriplex semibaccata

Atr sem

Desirable

n/a

4.9

Asparagus africanus

Asp afr

Undesirable

n/a

1

Chrysocoma ciliata

Chr cil

Undesirable

n/a

1.5

Delosperma tuberosum

Del tub

Desirable

n/a

5.6

Drosanthemum hispidum

Dro his

Desirable

n/a

5.4

Eberlanzia ferox

Ebe fer

Less desirable

n/a

2.7

Eriocephalus ericoides

Eri eri

Desirable

n/a

5

Felicia muricata

Fel mur

Desirable

n/a

6.5

Geigeria ornativa

Gei orn

Undesirable

n/a

2

Helichrysum dregeanum

Hel dre

Desirable

n/a

6.3

Helichrysum zeyheri

Hel zey

Less desirable

n/a

4.1

Limeum aethiopicum

Lim aet

Highly desirable

n/a

7.1

Lycium cinerium

Lyc cin

Less desirable

n/a

3

Pentzia globosa

Pen glo

Less desirable

n/a

4.8

Pentzia incana

Pen inc

Desirable

n/a

5.7

Phyllobolus junceum

 

 

 

 

Phymaspermum parvifolium

Phy par

Desirable

n/a

6.2

Psilaucolon absimile

 

 

 

 

Salsola calluna

Sal cal

Highly desirable

n/a

7.2

Salsola kali

Sal kal

Undesirable

n/a

1.5

Trichodiadema pomeridianum

Tri pom

Desirable

n/a

6.5

Tripteris sinuatum

Tri sin

Highly desirable

n/a

7.2

Walafrida geniculata

Wal gen

Highly desirable

n/a

7

Zygophyllum incrustatum

Zyg inc

Undesirable

n/a

2

 

 

 

 

 

Grasses

Aristida canescens

Ari can

Less desirable

Increaser II

4

Aristida congesta

Ari con

Undesirable

Increaser II

1.3

Bothriochloa insculpta

Bot ins

Desirable

Increaser II

4.4

Cenchrus ciliaris

Cen cil

Highly desirable

Decreaser

7.9

Chloris gayana

Chl gay

Desirable

Decreaser

6.6

Chloris virgata

Chl vir

Undesirable

Increaser II

1.8

Cymbopogon plurinodis

Cym plu

Highly desirable

Increaser III

7.6

Cynodon incompletus

Cyn inc

Less desirable

Increaser II

4.1

Digitaria eriantha

Dig eri

Highly desirable

Decreaser

8.9

Enneapogon scoparius

Enn sco

Less desirable

Increaser III

4.4

Eragrostis curvula

Era cur

Desirable

Increaser II

6.7

Eragrostis lehmanniana

Era leh

Desirable

Increaser II

5.4

Eragrostis obtusa

Era obt

Less desirable

Increaser II

4

Fingerhuthia africana

 

 

 

 

Heteropogon contortus

Het con

Highly desirable

Increaser II

7.2

Hyparrhenia hirta

Hyp hir

Desirable

Increaser I

6.3

Setaria verticillata

Set ver

Undesirable

Increaser II

1.6

Sorghum bicolor

Sor bic

 

 

 

Tetrachne dregei

Tet dre

Highly desirable

Decreaser

10

Themeda triandra

The tri

Highly desirable

Decreaser

9.3

Tragus koelerioides

Tra koe

Undesirable

Increaser II

2.2

Tragus racemosus

Tra rac

Undesirable

Increaser II

1.3

Urochloa mosambiscensis

Uro mos

Desirable

Increaser II

5

 

 

 

 

 

“Opslag” (Ephimerals)

Bidens bipinnata

Bid bip

Undesirable

n/a

1

Conyza albida

Con alb

Undesirable

n/a

0.7

Solanum nigrum

Sol nig

Undesirable

n/a

1.6

Tagetes minuta

Tag min

Undesirable

n/a

1

Tribulus terrestris

Tri ter

Undesirable

n/a

0.5

Trichodiadema pomeridianum

Tri pom

Desirable

n/a

6.5

 

Published

Grootfontein Agric 10 (1)