Effects of Herbicide on the Invasive grass, Cymbopogon nardus

(Franch.) Stapf (Tussocky Guinea grass) and Responses of Native Plants

in Kikatsi subcounty, Kiruhuura district, western Uganda

Final Report on Activity 3.4 of Component 3 of the UNEP/GEF-IAS funded Project

(NARO)

Removing Barriers to Invasive Plant Management in Africa

Paul Ssegawa Makerere University

Faculty of Science Department of Botany Herbarium

P.O. Box 7062 Kampala

April 2007

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Table of Contents

Executive summary 4

1.0 Introduction 5

1.1 Materials and methods 7

1.1.1 Study species 7

1.1.2 Study site 9

1.1.3 Experimental design 9

1.1.4 Herbicide effects on Cymbopogon nardus 11

1.1.5 Herbicide effects on other plant species 12

1.1.6 Community effects 12

1.1.7 Site similarity 13

1.2 Results 14

1.2.1. Floristics 14

1.2.2 Similarity among sites 15

1.2.3 Herbicide effects on Cymbopogon nardus 16

1.2.4 Herbicide effects on other plant species 17

1.2.5 Community effects 18

1.2.6 Community composition 19

1.3 Discussion 20

1.4 Conclusions and Recommendations 22

1.5 Future research perspectives and issues 22

2.0 Identification of Cassia species in Kampala 24

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3.0 Identification of Lantana species in Kakiri, Masindi and Iganga areas 26

4.0 Acknowledgements 29

5.0 References 30

Appendix 32

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Executive Summary The need to control noxious weeds includes management of invasive plants, but little is known about how indigenous plant communities respond to this control. The grass, Cymbopogon nardus (Franch.) Stapf (Tussocky Guinea grass) is one of the most prevalent invasive plants in the pastoral lands of the Ankole region in western Uganda. This study investigated the effects of the herbicide Round-up® (glyphosate) on C. nardus and the response of the plant communities to the herbicide. There was spot application of Round-up® in demarcated stands located in Bukonja, Karuroko, Keikoti, Kikaatsi and Kitazigurukwa villages in Kikatsi subcounty, Kiruhuura district in March 2006, after burning in January 2006. Control plots were also established in Kikaatsi and Bukonja villages. All plant species occurring in 1 x 1 m plots established in both treated and control plots were enumerated. A total of 120 plots were established during the survey. Data were analyzed using MVSP, SPSS and CANOCO software. A total of 137 species belonging to 96 genera and 27 families were recorded in both the control plots and glyphosate treated stands. Most of the species belonged to the families Fabaceae, Poaceae and Asteraceae each being represented by 32, 27 and 15 species respectively. The least common families included Anacardiaceae, Anthericaceae, and Asparagaceae, each represented by one species. Cluster analysis revealed three distinct clusters of stands based on species assemblage compositions, and reflected the effects of herbicide treatment and role of native vegetation types in influencing plant species compositions. Herbicide decreased the C. nardus density and increased the density of other species in the treated plots. Community differences were found in the treated stands after C. nardus reduction, specifically with greater abundance of ephemerals, mainly the forbs. These results indicate that spot spraying with glyphosate reduces C. nardus without negatively impacting indigenous species and that indigenous species respond positively to C. nardus reduction. Future research and management perspectives are also given. The identified Cassia species at the Kampala Golf course is Cassia grandis and the Lantana species identified in Kakiri, Masindi and Iganga are Lantana camara and Lantana trifolia. Lantana camara (an introduced species) is dominant and aggressive in some bushes and abandoned fields whereas Lantana trifolia (an indigenous species) is rare and some times grows alongside Lantana camara. 1.0 Introduction

Invasive plant species have the potential to negatively impact native plant species and communities, including reduction of biodiversity (Lodge, 1993; Woods, 1997), alteration of community structure, function, and composition (Woods, 1997), and changes in dynamic community properties (Huenneke & Mooney, 1989). However, direct impacts of invasive plants on native plants have not been well studied (Parker et al., 1999; D'Antonio & Kark, 2002), with some exceptions (Miller & Gorchov, 2004).

In Uganda, some of the forest reserves and rangelands have gradually been invaded by species of special concern, as some of these forest reserves and rangelands form part of the only remaining representatives of intact plant communities. Because control of

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invasive species is a major concern and cost of management of forest reserves, rangelands and other habitats, as well as a common component of restoration efforts, there is a need for better understanding of the impacts of invaders and the response of plant communities to eradication efforts (D'Antonio & Meyerson, 2002). In western Uganda, particularly in Mbarara and Kiruhuura districts, the rangelands have been gradually taken over by the Cymbopogon nardus, also commonly known as the Tussocky Guinea grass. The grass, Cymbopogon nardus, which is indigenous to Uganda (Phillips et al., 2003) has established there and is perceived to be a problem by the local farmers. It is known to grow in grassland, rocky areas, savanna and deciduous bushland, more rarely on roadsides and seasonally wet places (Phillips et al., 2003). It occurs at altitudes ranging between 915 – 2900 m above sea level (Phillips et al., 2003). About three-quarters of all domestic livestock depend upon grazing lands for survival. However, invasive plants can have negative effects on the plant species composition in the grazing lands. They impact the livestock industry by lowering yield and quality of forage, interfering with grazing, poisoning animals, increasing costs of managing and producing livestock, and reducing land value. They also impact wildlife habitat and forage, deplete soil and water resources, and reduce plant and animal diversity. Numerous mechanical and cultural control options have been developed to manage noxious rangeland weeds, including mowing, prescribed burning, timely grazing, and perennial grass reseeding or interseeding. In addition, several herbicides are registered for use on rangelands and most biological control programs focus on noxious rangeland weed control. Because Round-up® is a nondiscriminatory herbicide, other species with leaves at the time of spraying could potentially be affected. This study monitored representative species to quantitatively determine whether or not they were impacted by Round-up®. The objectives were to determine the extent to which Cymbopogon nardus changes the plant communities on a small scale and whether herbicide application is an effective control mechanism for Cymbopogon nardus —a necessary step before widespread removal attempts are made (Hager & McCoy 1998). In addition, trial removal should reveal other responses to Cymbopogon nardus elimination, such as erosion and invasions of other exotics, and thus inform management and restoration decisions. This study addressed the following questions: (1) What is the effect of Round-up® application on the density of Cymbopogon nardus; (2) What is the effect of Round-up® application on other plant species; and (3) What is the effect of the reduced Cymbopogon nardus density on native vegetation and tree seedlings? 1.1 Materials and Methods 1.1.1 Study species Cymbopogon nardus (L.) Rendle (Synonym: Cymbopogon afronardus Stapf.)

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Description: Tall tufted perennial with narrow leaf-blades. Panicle narrow, 15-30 cm long with racemes 8-10 mm long, often rather villous; sessile spikelets flat or concave on the back with winged keels, awn 5-6 cm long (Napper, 1965). Distribution: Throughout southern and north-eastern tropical Africa, Uganda, Tanzania and Kenya. Also in India, Sri Lanka and Burma. Growth: C. nardus establishes naturally from seed in the highly grazed areas beneath bushes. Response to defoliation: Generally C. nardus is avoided in grazing. Light grazing encourages it, but heavy grazing pressure of one bullock per hectare prevented recolonization of the species (Harrington, 1974). Response to fire: It is very resistant to fire and too-frequent burning is one of the main causes of its increase. Harrington (1974) found that a late burn in the long dry season (usually late August in Uganda) carried out every third year reduced the biomass of C. nardus and encouraged the somewhat better, associated grasses of Brachiaria decumbens, Themeda triandra and Hyparrhenia filipendula. The burn should be against the wind and in weather which would minimize fire temperatures. This would prune the undesirable associated shrub Acacia hockii. Ability to compete with weeds: It is very competitive, and where overgrazing takes place in useful pastures it tends to increase. Palatability: The grass is unpalatable to cattle and cattle have been known to die of starvation when an abundance of it, in green condition, was available (Harrington, 1974). Buffalo will eat it sparingly and elephants will accept it during the dry season (Field, 1971). Economics: Cymbopogon nardus is an unpalatable, unwanted invader of Ankole region pastures in Uganda. Removal of C. nardus from fully stocked pastures improved growth rates by about 30 percent, but the rate of recolonization can be extremely rapid. The knowledge of the ecology of the grass is supremely important in the development of the area (Harrington, 1974). It is a good thatching and mulching material and the grass produces citronella, an aromatic oil. The cultivated form of C. nardus (L.) Rendle (citronella) is grown in Sri Lanka and the West Indies and is derived from an awnless variant (Phillips et al. 2003; Figure 1).

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Animal production: The invasion of a pasture by C. nardus always leads to a reduction in animal production.

Figure 1: A Cymbopogon nardus dominated plant community

1.1.2 Study site Kiruhuura district lies mainly within the pastoral system as the main agroecological zone. There are three farming systems recognized in the district and include livestock farming system, annual crops farming system and the banana farming system. There are two rainy seasons and the average rainfall is estimated to be 1000 mm per annum. The first rainy season is from mid February to end May, while the second rains are from mid August to end December. Two dry spells separate the rainy seasons. The long dry season is from June to mid August and between January and February there is short dry spell. The district thus falls within the Ankole-Southern climatic zone. The soil is mainly comprised of sandy loams and consists of several varieties, including the Bukora series, Rugaga series, Kooki series, Bugamba series, Kazo series Nyabushozi

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catena. Soils on hill tops are generally shallow and those in the valleys are relatively deeper. The reddish brown silty clay loams and yellowish red silt clay loams have medium to low productivity. Shallowness of the soil has led to land degradation. The vegetation in the district can be classified into grass savannas, moist Acacia savannahs, dry Acacia savannahs and permanent swamps. There are several forest reserves including rainforests, Cyprus and Eucalyptus plantations. The district has three main land tenure systems, customary, freehold/mailo and leasehold. Customary tenure is the most common in the district. Land ownership in the district mainly comprises private ownership with the majority of people owning small pieces of land (about 2.5 acres) while a few own excessively large tracts. Agriculture constitutes the main land use in the district, comprising a system of mixed agriculture with perennial and annual crops, as well as grazing throughout the district. Bananas are grown in pure stands or sometimes intercropped with beans and fruit trees like avocado, pawpaw and mangoes. Animals are grazed communally in the hills comprising communal grazing lands. 1.1.3 Experimental design In March 2007, 20 1 X 1-m plots were established in five of the glyphosate treated stands established in Bukonja, Keikoti, Karuroko, Kitazigurukwa and Kikaatsi villages in Kikaatsi subcounty, Kiruhuura district. These had been burnt and spot sprayed with Round-up® (glyphosate) using a knapsack sprayer at various dates as shown in Table 1. Another 10 1 X 1-m plots were established in each of Kikaatsi and Bukonja villages as control plots. The control plots were selected randomly in areas that are used by farmers for grazing with evident human disturbance (e.g., tree cutting) in the localities of Kikatsi and Bukonja. In total, 120 plots including the control plots were established. Table 1: The treatments and their respective dates done to the various stands

Stand Date of burning Date of spraying Glyphosate (gm/l) Karuroko 30-Jan-06 6-Mar-06 3.33 Kitazurugukwa 28-Jan-06 9-Mar-06 4.17 Kikatsi 28-Jan-06 10-Mar-06 3.33 Bukonja 29-Jan-06 11-Mar-06 3.33 Keikoti 29-Jan-06 10-Mar-06 3.33

1.1.4 Herbicide effects on Cymbopogon nardus The number of individual tussocks of Cymbopogon nardus in each plot of the glyphosate treated stands were counted. To determine the effects of treatment and stand on density of Cymbopogon nardus, Kruskal-Wallis tests were carried out on each stand separately using the SPSS Inc. (1999) program.

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1.1.5 Herbicide effects on other plant species Individuals of each species were counted in each plot (Figure 2). Treatment effects on density were analyzed separated for each stand by Kruskal-Wallis tests.

Figure 2: Assessment of 1-m2 plots for species richness in sprayed stands. Inset: A signpost to indicate presence of sprayed stand (i.e. demonstration plot). 1.1.6 Community effects All the plant species less than or equal to 0.8 m tall (including herbs, vines, tree seedlings and shrubs) were enumerated in each of the 1 X 1 m plot (Figure 2). Nomenclature follows Polhill et al. (1954) and Phillips et al. (2003). Voucher specimens of all species that could not be identified in the field were brought to the Makerere University Herbarium for identification. For each plot, species richness (total species detected during enumeration) was determined. The effect of herbicide treatment and stand on richness was determined by Kruskal-Wallis tests. Comparison was made of species diversity between treatments by calculating the Shannon-Weiner diversity (Magurran, 1988). To determine the degree of similarity among the different stands in the different villages, based on species assemblage compositions, cluster analysis (Kovach, 1999) was used. To examine compositional patterns in the grassland community, plots were ordinated using detrended correspondence analysis (DCA) of the abundances of each species (excluding C. nardus) using CANOCO software (version 4.0, ter Braak & Smilauer, 1998). To determine whether control and sprayed plots differed significantly in species composition, plot scores for each of the first two axes of each ordination were analyzed

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using one-way ANOVA. Univariate analyses are appropriate because the DCA axes are, by definition, orthogonal and uncorrelated (McCune & Grace, 2002). 1.1.7 Site Similarity The presence of 137 plant species was recorded in binary (presence or absence) format for each of the seven stands investigated. To determine similarity of stands, the 137 X 7 array was used to calculate Jaccard’s coefficients (JI) (Ludwig & Reynolds, 1988) for each pair (A and B), where JI = a/(a+b+c), where a is the number of species that stands A and B have in common, b as the number of species present in stand A but absent from stand B, and c as the number of species present in stand B but absent from stand A. The JI ranged from near 0 (for a stand pair highly dissimilar with respect to species) to near 1 (stand pair very similar). An agglomerative clustering technique (weighted centroid) provided in the Multivariate Statistical Package (MVSP) of Kovach (1999) was used to produce a dendrogram containing all seven stands including controls. A minimum JI of 0.2 was used for defining clusters. Other measures of similarity and also measures of distance between stands were attempted along with several different methods of clustering (single-linkage and complete-linkage techniques). All techniques provided similar results, with the Jaccard’s index clustering being most meaningful ecologically. 1.2 Results 1.2.1 Floristics A total of 137 species belonging to 96 genera and 27 families were recorded in both the control plots and glyphosate treated stands (Appendix 1; Table 2). Most of the species belonged to the families Fabaceae, Poaceae and Asteraceae each being represented by 32, 27 and 15 species respectively. The least common families incuded Anacardiaceae, Anthericaceae, Asparagaceae, Connaraceae, Oleaceae and Orchidaceae each represented by one species. Table 2: Plant families and their respective numbers of species

Family Number of species Family Number of species Acanthaceae 6 Labiatae 5 Amaranthaceae 2 Malvaceae 4 Anacardiaceae 1 Oleaceae 1 Anthericaceae 1 Orchidaceae 1 Asparagaceae 1 Phytolaccaceae 1 Asteraceae 15 Poaceae 27 Commelinaceae 6 Polygalaceae 1 Connaraceae 1 Sapindaceae 1 Convolvulaceae 5 Scrophulariaceae 2 Cucurbitaceae 2 Solanaceae 3 Cyperaceae 4 Tiliaceae 3 Euphorbiaceae 7 Verbenaceae 2 Fabaceae 31 Vitaceae 2 Hypoxidaceae 2

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Most of the species recorded were forbs representing 62.8% (86 species) of all the species recorded. The graminoids, shrubs, trees and climbers were represented by 26, 12, 2 and 6 species respectively. 1.2.2 Similarity among sites Species presence or absence was scored in the seven stands as shown in Appendix 1 and provided the basis for cluster analysis. Cluster analysis provided evidence of likeness of species assemblages among seven stands investigated (Figure 3). Bukonja and Kikaatsi stands had the highest Jaccard’s similarity index (JI) of 0.442, followed by Karuroko and Kitazigurukwa pair; and Bukonja control and clustering with Kikaatsi control at JI of 0.437 and 0.41 respectively. Using a minimum JI of 0.2 for defining clusters, the analysis produced three distinct groups of sites A, B and C as shown in Figure 3. Observed species richness as recorded in sampling plots for cluster A was 39; B (101); and C (78).

Figure 3: Cluster analysis of seven stands investigated represented by the respective villages in which they are located. Stands groupings (A - C) were defined using a Jaccard’s coefficient of 0.2 (dotted line). 1.2.3 Herbicide effects on Cymbopogon nardus After spraying, there was significant treatment effect on the density of C. nardus. The sprayed plots averaged (mean ± SE) 2.36 ± 0.14 Cymbopogon nardus tussocks whereas the control plots averaged 3.73 ± 0.47 (Figures 4 & 5). However, there was no significant difference in densities of C. nardus in the treated stands (Kruskal-Wallis test: H = 0.333, p = 0.564).

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00.5

11.5

22.5

33.5

44.5

5

Bukonja

Bukonja

- Con

trol p

lots

Karurok

o

Keikoti

Kikaatsi

Kikaatsi

- Con

trol p

lots

Kitazig

urukw

a

Stand

C. n

ardu

s de

nsity

(ind

/sq.

m.)

Figure 4: Density of Cymbopogon nardus in the respective stands Figure 5: Different sections of the surveyed areas showing glyphosate treated stands almost devoid of Cymbopogon nardus (A) but dominated by Loudetia kagerensis and Hyperthelia dissoluta and other sites dominated by Cymbopogon nardus especially in the control plots (B). Figure 5: 1.2.4 Herbicide effects on other plant species There was a lower species density in the control plots (mean ± SE) 22 ± 4.1 compared with the treated plots (34.6 ± 2.5; Figure 6). However, there were no significant differences between the treated and control plots (Kruskal-Wallis: H = 0.631, p = 0.816).

A B

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05

1015202530354045

Karurok

o

Kitazu

ruguk

waKika

tsi

Bukon

ja

Keikoti

Bukon

ja -co

ntrol

Kikatsi

-contr

ol

Stand

Den

sitie

s (In

d/sq

. m.)

Figure 6: Densities of other species recorded in the treated and control plots 1.2.5 Community effects There were no significant differences in species richness between the sprayed and the control plots with means (± SE) of 56.7 ± 3.51 and 27.5 ± 0.50 respectively (ANOVA: F=7.73; Table 3). This was furrher confirmed by ANOVA, which revealed no treatments effects on plot scores on axis 1 or 2 generated by detrended correspondence analysis ordination. Species richness was higher among the sprayed plots compared to the control plots. Similarly, the Shannon-Weiner species diversity index for the sprayed plots was higher (4.12) compared to the control plots (3.25). Table 3: Mean species richness per 1-m2 plot for control and herbicide treated plots Stands Total number of species Species richness per sq.m. Bukonja 56 2.8 Karuroko 67 3.35 Keikoti 45 2.25 Kikaatsi 55 2.75 Kitazigurukwa 58 2.9 Bukonja_Control 28 2.8 Kikaatsi_Control 27 2.7

1.2.6 Community composition Control and sprayed plots differed in community composition based on ordinations although there were no significant differences in species richness (Figure 7). It was recognizable in the DCA ordination biplot in Figure 7 that the control plots were separated from the sprayed plots.

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Axis

2

Axis 1+0.0 +4.0

+0

.0

+3

.0

Kikaatsi control

KikaatsiBukonja

Kitazigurukwa

Keikoti

Bukonja control

Karuroko

Figure 7: Detrended correspondence analysis (DCA) ordination of sprayed (open circles) and control plots (filled triangles) based on the abundances of all species except Cymbopogon nardus. Eigenvalues: Axis 1 = 0.378, Axis 2 = 0.210. 1.3 Discussion In comparison with the control plots, spot application of the Round-up® reduced the density of the C. nardus by 55%. This reduction inevitably changes the floristic composition of the plots by allowing other previously suppressed plant species to grow. However after the removal efforts, reestablishment of C. nardus population by seeds from the seed bank or immigration is likely due to the newly created space and resources. In fact seedlings were observed in the sprayed plots although in very few numbers. Herbicide treatment enhanced the growth of many herbaceous native species by 36% compared to the control plots. The descriptive species particularly in the Keikoti, Kitazigurukwa and Karuroko of cluster B (Figure 3) included Zornia diphylla, Brachiaria platynota, Asparagus africanus, Paspalum scrobiculatum, Achyranthes aspera, Vigna multinervis, Cyphostemma adenocaule, Leucas deflexa and Themeda triandra. The descriptive species for the Bukonja and Kikatsi stands of cluster C (Figure 3) included Hyperthelia dissoluta, Loudetia kagerensis, Tephrosia linearis, Hypoxis angustifolia, Leonotis nepetifolia, Evolvulus alsinoides, Clerodendrum rotundifolium, Bidens pilosa, Grewia similis, Eleusine indica, Conyza floribunda and Vigna kirkii. However the control plots were characterized by quite different communities of plants. The species typical of the control plots (cluster A, Figure 3) included Loudetia kagerensis, Cymbopogon nardus, Eragrostis racemosa, Brachiaria brizantha, Emilia coccinea, Brachiaria decumbens, Glycine wightii, Acalypha villicaulis, Digitaria longiflora and Crotalaria axillaris. These results demonstrate the role of herbicide in determining plant species composition. However, it should be noted that application of herbicide could negatively

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impact plant species if application is less discriminating or if species composition at the time of spraying differs due to interyear differences in weather and phenology. Species richness was not significantly affected by the treatment of C. nardus (Table 3) because of the little difference in species diversity with or without reduced C. nardus biomass. In general, the diversity is reduced by the presence of C. nardus and so will not change until the C. nardus is completely eliminated. Future years of data are needed to test this hypothesis in this system. The separation of the control versus sprayed stands in the ordination can be attributed the community changes resulting from the herbicide treatment. Although cumulative effects of species abundance changes since the spraying were responsible for the plot separation in the ordinations, specific responses of growth form groups and species are also important in understanding how C. nardus affects other species communities. For example, it is possible that the removal of C. nardus increased abundance of species with seed banks (e.g. annuals), high seed input (e.g. trees) especially in Keikoti and Kitagurukwa, or high vegetative growth (e.g. vines). There were no observable effects on the growth of the tree, Acacia hockii, which is quite common, or abundance of tree seedlings or annuals, and vines were too sparse in our plots for analysis. Another plausible cause of differences in ordination is the difference in inherent vegetation types in Kikaatsi subcounty. Different areas in Kikaatsi have different vegetation types ranging from the Cymbopogon nardus dominated grasslands to the Allophyllus africanus, Acacia abyssinica and Acacia hockii dominated wooded grasslands. These too, influence the herbaceous species composition. 1.4 Conclusions and recommendations A single application of herbicide in the various stands significantly reduced the density of C. nardus but resulted in only modest responses of the native community and representative species. It is possible that C. nardus does not have a large competitive effect on native plants. Alternatively, the modest effects may be due to the short duration of this study. Therefore it would be appropriate to have continued studies to ascertain whether continued C. nardus reduction via annual herbicide application results in greater responses of native plants. 1.5 Future research perspectives and issues It should have been a good idea to do surveys in the various stands before the treatments with glyphosate were done. This would have given us a clear understanding of the role of glyphosate in influencing species diversity. Establishment and fencing of control plots, devoid of grazing, human disturbance and with no glyphosate spraying will help to come up with results that are comparable. The control plots, as used in this report, cannot not give scientifically reliable results but only an impression of what would be expected.

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Successful management of Cymbopogon nardus on rangelands or pasture lands will require the development of a long-term strategic plan incorporating prevention programs, education materials and activities, and economical and sustainable multi-year integrated approaches that improve degraded rangeland communities, enhance the utility of the ecosystem, and prevent reinvasion or encroachment by other noxious weed species. The provision of farmers with planting material such as Eleusine indica, Centrosema sp. and Chloris gayana is a good strategy so far. It is recommended that future surveys should have well demarcated and fenced control plots similar in size and vicinity to the Round-up® (glyphosate) spot sprayed plots in all localities/sites. Some visible colouring should be put in the diluted glyphosate to avoid repeated spraying. It is also recommended that regular monitoring, through plant surveys, of the native species survival, growth and reproduction, including the response of Cymbopogon nardus to glyphosate spot spraying should be done, three to four times a year to coincide with the drier and wetter seasons in both control and treated plots. 4.0 Acknowledgements The visit to Kiruhuura district, Kikatsi subcounty was made possible with help from the Mbarara ZARDI Office. Special thanks to Dr. Byenya Steven for the discussions we shared. My sincere thanks to Mr. Kasigwa Howard for his time and help in the identification of study sites and liaising with local authorities and farmers. I also extend my gratitude to the Staff of UNEP/GEF-IAS/NARO for their continuous support to finalise the consultancy in the short time available. I would also like to thank Dr. Gadi Gumisiriza and Mr. Bayo Richard for their invaluable comments on the manuscript. 5.0 References D'Antonio, C., and L. A. Meyerson. 2002. Exotic plant species as problems and

solutions in ecological restoration: a synthesis. Restoration Ecology 10: 703– 713. Hager, H. A., and K. D. McCoy. 1998. The implications of accepting untested

hypotheses: a review of the effects of purple loosestrife (Lythrum salicaria) in North America. Biodiversity and Conservation 7: 1069– 1079.

Huenneke, L. F., and H. A. Mooney. 1989. The California annual grassland: an overview. In (Eds. L. F. Huenneke and H. A. Mooney). Grassland structure and function. pp 213– 218. Kluwer Publishers.

Kovach, W. I. 1999. A multivariate statistical package for windows, version 3.1. Kovach computing services, Pentraeth, Wales.

Lodge, D. M. 1993. Biological invasions: lessons for ecology. Trends in Ecology and Evolution 8: 133– 137.

Ludwig, J.A. and Reynolds, J.F. 1988. Statistical ecology: a primer on methods and computing. John Wiley and Sons, New York.

Magurran, A. E. 1988. Ecological diversity and measurement. Princeton University Press, Princeton.

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McCune, B., and J. B. Grace. 2002. Analysis of ecological communities. MjM Software Design.

Miller, K. E., and D. L. Gorchov. 2004. The invasive shrub Lonicera maackii, reduces growth and fecundity of perennial forest herbs. Oecologia 139: 359– 375.

Parker, I. M., D. Simberloff, W. M. Lonsdale, K. Goodell, M. Wonham, P. M. Kareiva, M. H. Williamson, B. Von Holle, P. B. Moyle, J. E. Byers, and L. Goldwasser. 1999. Impact: toward a framework for understanding the ecological effects of invaders. Biological Invasions 1: 3– 19.

Phillips, S., Namaganda, M., and Lye, K.A. 2003. 115 Ugandan grasses. Makerere Herbarium Handbook no. 1. Makerere University Herbarium, Department of Botany. Makerere University, Kampala.

Polhill, R.M., Milne-Redhead, E., Turrill, W.B., and Hubbard, C.E. (from 1954 onwards). Flora of Tropical East Africa (in many parts). Crown Agents, London and Balkema, Rotterdam.

SPSS Inc. 1999. SPSS Base 11.0 for Windows User's Guide. SPSS Inc., Chicago IL. Ter Braak, C. J. F. and Smilauer, P. 2002. CANOCO reference manual and CanoDraw

for windows user’s guide: Software for canonical community ordination (version 4.5) Ithaca, NY, USA, Microcomputer Power.

Woods, K. D. 1997. Community response to plant invasion. In: (Eds. J. O. Luken, and J. W. Thieret). Assessment and management of plant invasions. pp 56– 67. Springer Publishers.

Appendix 1: List of species recorded in the sampled plots located in the various villages indicated 1 = presence; 0 – absence of species from stand/locality

Stands/Plot locations Family Species Habit/life

form Bukonja Bukonja (‘Control

plots’) Karuroko Keikoti Kikaatsi Kikaatsi (‘Control

plots’) Kitazigurukwa Total

Acanthaceae Asystasia gagentica Forb 0 0 0 1 0 0 0 1 Acanthaceae Crabbea velutina Forb 0 1 1 0 1 1 0 4 Acanthaceae Dyschoriste radicans Forb 0 1 1 1 1 1 1 6 Acanthaceae Justicia flava Forb 0 0 0 1 0 0 0 1 Acanthaceae Justicia matamensis Forb 0 0 1 1 0 0 0 2 Acanthaceae Monechma subsessile Forb 1 1 1 1 1 1 1 7 Amaranthaceae Achyranthes aspera Forb 0 0 1 0 0 0 0 1 Amaranthaceae Psilotrichum axilliflorum Forb 0 0 0 0 1 0 0 1 Anacardiaceae Rhus natalensis Shrub 0 0 1 1 0 0 0 2 Anthericaceae Chlorophytum micranthum Forb 1 0 0 0 1 0 0 2 Asparagaceae Asparagus africanus Forb 1 0 1 0 1 0 1 4 Asteraceae Ageratum conyzoides Forb 1 0 1 0 0 0 0 2 Asteraceae Aspilia Africana Forb 1 0 0 1 0 0 0 2 Asteraceae Bidens pilosa Forb 0 0 0 0 1 0 0 1 Asteraceae Conyza floribunda Forb 1 0 1 0 0 0 0 2 Asteraceae Crassocephalum sarcobasis Forb 0 0 1 0 0 0 0 1 Asteraceae Emilia coccinea Forb 1 1 1 1 1 1 1 7 Asteraceae Erlangea cordifolia Forb 0 0 1 0 0 0 1 2 Asteraceae Helichrysum sp. Forb 0 1 0 0 0 0 0 1 Asteraceae Lactuca lasiorhiza Forb 0 1 0 0 0 0 0 1 Asteraceae Launaea cornuta Forb 0 0 0 0 0 0 1 1 Asteraceae Microglossa pyrifolia Forb 0 0 0 0 0 0 1 1 Asteraceae Tagetes minuta Forb 0 0 1 0 0 0 1 2 Asteraceae Vernonia conferta Forb 1 0 0 0 0 0 0 1 Asteraceae Vernonia schweinfurthii Forb 1 1 1 1 1 1 1 7 Asteraceae Vernonia smithiana Forb 0 0 0 0 0 0 1 1 Commelinaceae Commelina Africana Forb 1 0 1 1 1 1 1 6 Commelinaceae Commelina benghalensis Forb 1 1 0 0 0 0 0 2 Commelinaceae Commelina purpurea Forb 1 0 1 1 1 0 0 4 Commelinaceae Cyanotis lanata Forb 0 1 0 0 1 1 0 3 Commelinaceae Cyanotis nodiflora Forb 0 0 0 1 0 0 0 1 Commelinaceae Ipomoea blepharophylla Creeper 0 0 0 0 1 0 0 1 Connaraceae Rourea patra Forb 1 1 1 1 1 1 1 7 Convolvulaceae Astripomoea malvacea Forb 0 0 0 0 1 1 0 2 Convolvulaceae Evolvulus alsinoides Climber 1 0 0 0 0 0 0 1 Convolvulaceae Ipomoea eriocarpa Creeper 0 0 0 0 0 0 1 1 Convolvulaceae Ipomoea obscura Creeper 0 0 0 0 1 0 0 1 Convolvulaceae Ipomoea sp. Creeper 0 0 0 0 0 0 1 1 Cucurbitaceae Cucumis sp. Climber 0 0 1 0 0 0 0 1

19

Stands/Plot locations Family Species Habit/life

form Bukonja Bukonja (‘Control

plots’) Karuroko Keikoti Kikaatsi Kikaatsi (‘Control

plots’) Kitazigurukwa Total

Cucurbitaceae Oreosyce Africana Creeper 1 0 0 0 0 0 0 1 Cyperaceae Abilgaardia ovata Forb 0 1 0 0 0 0 0 1 Cyperaceae Cyperus cyperoides Forb 1 0 1 1 1 0 1 5 Cyperaceae Fimbristylis dochotoma Forb 0 1 0 0 0 0 0 1 Cyperaceae Kyllinga sp. Forb 1 0 1 1 1 0 0 4 Euphorbiaceae Acalypha lanceolata Forb 0 0 1 0 0 0 0 1 Euphorbiaceae Acalypha villicaulis Forb 1 1 0 0 0 1 1 4 Euphorbiaceae Erythrococca trichogyne Forb 0 0 1 1 0 0 0 2 Euphorbiaceae Euphorbia inaquilatera Forb 0 0 1 0 0 0 0 1 Euphorbiaceae Flueggea virosa Shrub 0 0 0 1 0 0 0 1 Euphorbiaceae Phyllanthus ovalifolius Forb 0 0 1 0 0 0 0 1 Euphorbiaceae Phyllanthus pseudoniruri Forb 0 0 0 0 0 0 1 1 Fabaceae Acacia abyssinica Tree 0 0 0 1 0 0 0 1 Fabaceae Acacia hockii Tree 0 0 1 1 1 0 1 4 Fabaceae Alysicarpus rugosus Forb 0 1 0 0 0 0 0 1 Fabaceae Cassia kirkii Forb 0 1 0 0 0 0 0 1 Fabaceae Cassia mimosoides Forb 1 1 0 1 1 1 1 6 Fabaceae Centrosema pubescens Forb 1 0 1 0 1 0 1 4 Fabaceae Crotalaria axillaries Forb 0 0 1 0 0 1 1 3 Fabaceae Crotalaria brevidens Forb 1 0 0 0 0 0 0 1 Fabaceae Crotalaria glauca Forb 1 0 0 0 1 0 0 2 Fabaceae Desmodium hirtum Forb 0 0 0 0 1 0 0 1 Fabaceae Dolichos sericeus Forb 0 1 0 0 0 0 0 1 Fabaceae Glycine wightii Forb 1 1 1 1 1 0 1 6 Fabaceae Indigofera arrecta Forb 0 0 0 1 0 0 0 1 Fabaceae Indigofera circinella Forb 1 1 1 1 1 1 1 7 Fabaceae Indigofera dendroides Forb 1 0 1 0 1 0 1 4 Fabaceae Indigofera spicata Forb 1 0 1 1 1 1 1 6 Fabaceae Indigofera spinosa Forb 0 0 0 1 0 0 0 1 Fabaceae Macrotyloma axillare Forb 0 0 1 0 0 0 0 1 Fabaceae Pseudarthria hookeri Shrub 0 0 1 0 0 0 1 2 Fabaceae Pycnospora lutescens Forb 0 1 0 0 0 0 0 1 Fabaceae Rhynchosia sp. Shrub 0 0 1 0 0 0 0 1 Fabaceae Tephrosia linearis Forb 0 1 0 0 1 0 1 3 Fabaceae Tephrosia sp. Forb 0 0 0 0 0 0 1 1 Fabaceae Vigna kirkii Forb 1 0 0 0 0 0 0 1 Fabaceae Vigna multinervis Forb 1 0 0 0 0 0 1 2 Fabaceae Vigna parkeri Forb 1 0 1 0 1 0 1 4 Fabaceae Vigna schimperi Forb 0 0 0 0 1 1 0 2 Fabaceae Vigna sp. Forb 1 0 1 1 1 0 1 5 Fabaceae Zornia diphylla Forb 0 0 0 0 1 1 1 3 Fabaceae Zornia pratensis Forb 1 1 0 0 1 0 0 3 Fabaceae Zornia setosa Forb 1 1 1 0 1 1 1 6

20

Stands/Plot locations Family Species Habit/life

form Bukonja Bukonja (‘Control

plots’) Karuroko Keikoti Kikaatsi Kikaatsi (‘Control

plots’) Kitazigurukwa Total

Hypoxidaceae Hypoxis angustifolia Forb 1 0 0 0 1 0 0 2 Hypoxidaceae Hypoxis obtuse Forb 0 0 0 1 0 0 0 1 Labiatae Hoslundia opposite Shrub 0 0 1 0 0 0 1 2 Labiatae Leonotis nepetifolia Shrub 1 0 1 1 0 0 1 4 Labiatae Leucas deflexa Forb 0 0 0 0 0 0 1 1 Labiatae Ocimum grattisimum Shrub 0 0 0 1 0 0 0 1 Labiatae Solenostemon forskohlii Forb 0 0 1 0 0 0 0 1 Malvaceae Hibiscus aethiopicus Forb 1 0 0 0 0 0 0 1 Malvaceae Hibiscus fuscus Forb 0 0 1 0 0 0 0 1 Malvaceae Hibiscus vitifolius Forb 0 0 1 0 0 0 0 1 Malvaceae Sida cordifolia Forb 0 0 1 0 0 0 1 2 Oleaceae Jasminum fluminense Climber 0 0 1 1 0 0 0 2 Orchidaceae Eulophia cucullata Forb 0 0 0 0 1 0 0 1 Phytolaccaceae Phytolacca dodecandra Climber 0 0 1 0 0 0 0 1 Poaceae Andropogon sp. Graminoid 0 0 0 0 1 0 0 1 Poaceae Brachiaria brizantha Graminoid 1 0 0 0 1 1 1 4 Poaceae Brachiaria decumbens Graminoid 1 1 1 1 1 1 1 7 Poaceae Brachiaria jubata Graminoid 1 0 0 0 0 0 0 1 Poaceae Brachiaria platynota Graminoid 1 0 0 0 1 1 1 4 Poaceae Brachiaria ternate Graminoid 0 0 0 0 0 0 1 1 Poaceae Chloris gayana Graminoid 1 0 1 1 1 0 1 5 Poaceae Chloris pycnothrix Graminoid 0 0 1 0 0 0 0 1 Poaceae Cymbopogon afronardus Graminoid 1 1 1 1 1 1 1 7 Poaceae Cynodon dactylon Graminoid 1 0 0 0 0 0 1 2 Poaceae Digitaria abyssinica Graminoid 0 0 1 0 0 0 1 2 Poaceae Digitaria longiflora Graminoid 1 1 1 0 1 1 1 6 Poaceae Digitaria ternate Graminoid 1 0 0 1 1 0 1 4 Poaceae Eleusine indica Graminoid 1 0 1 1 0 0 1 4 Poaceae Eragrostis racemosa Graminoid 0 0 1 0 1 1 1 4 Poaceae Eragrostis tenuifolia Graminoid 1 0 0 0 0 0 0 1 Poaceae Hyparrhenia filipendula Graminoid 1 0 1 1 1 1 1 6 Poaceae Hyperthelia dissolute Graminoid 1 1 0 1 1 1 0 5 Poaceae Loudetia kagerensis Graminoid 1 1 1 1 1 1 1 7 Poaceae Microchloa kunthii Forb 1 0 0 0 0 0 0 1 Poaceae Panicum maximum Graminoid 1 0 1 1 0 0 1 4 Poaceae Paspalum scrobiculatum Graminoid 1 0 1 0 0 0 0 2 Poaceae Setaria incrassate Graminoid 1 0 0 0 0 0 0 1 Poaceae Setaria kagerensis Graminoid 0 0 1 0 0 0 0 1 Poaceae Setaria sphacelata Graminoid 0 0 0 0 0 0 1 1 Poaceae Sporobolus Africana Graminoid 1 0 1 1 1 1 1 6 Poaceae Themeda triandra Graminoid 1 0 0 0 1 0 1 3 Polygalaceae Polygala polygoniflora Forb 0 0 0 0 1 0 0 1 Sapindaceae Allophyllus africanus Shrub 0 0 0 1 0 0 0 1

21

Stands/Plot locations Family Species Habit/life

form Bukonja Bukonja (‘Control

plots’) Karuroko Keikoti Kikaatsi Kikaatsi (‘Control

plots’) Kitazigurukwa Total

Scrophulariaceae Craterostigma pumilum Forb 0 0 1 0 0 0 0 1 Scrophulariaceae Cycnium tubulosum Forb 0 0 0 0 1 0 0 1 Solanaceae Physalis peruviana Forb 1 0 0 0 0 0 0 1 Solanaceae Solanum dasyphyllum Forb 0 0 0 1 0 0 0 1 Solanaceae Solanum incanum Shrub 0 0 1 1 1 0 1 4 Tiliaceae Grewia similis Shrub 0 0 1 0 1 0 0 2 Tiliaceae Grewia trichocarpa Shrub 0 0 1 0 0 0 0 1 Tiliaceae Triumfetta rhomboidea Forb 0 0 1 0 0 0 1 2 Verbenaceae Clerodendrum rotundifolium Shrub 0 0 1 0 1 0 1 3 Verbenaceae Lippia abyssinica Forb 0 0 1 0 0 0 0 1 Vitaceae Cyphostema adenocaule Climber 0 0 1 1 0 0 0 2 Vitaceae Cyphostema serpens Climber 0 0 0 1 0 0 0 1 Total 56 28 67 45 55 27 58 336