This thesis investigates the invasion of Austroeupatorium inulifolium in degraded grasslands in the Knuckles Conservation Area of Sri Lanka. Several field and laboratory studies were conducted to examine the eco-physiological traits of A. inulifolium, map its distribution using satellite imagery, analyze its impacts on existing vegetation and soil nutrients, study litter decomposition rates and nutrient release patterns, assess the regeneration potential of A. inulifolium through soil seed banks and standing vegetation, and evaluate potential management interventions. The results showed that A. inulifolium is well-adapted to the heterogeneous environment, competes strongly with native species, alters soil properties and nutrient cycling, and may

1. INVASION OF AUSTROEUPATORIUM INULIFOLIUM IN
DEGRADED GRASSLANDS IN KNUCKLES CONSERVATION
AREA: ECOLOGY, IMPACTS AND IMPLICATIONS
INOKA PADMAKANTHI KUMARI PIYASINGHE
PhD 2017

2. ii
INVASION OF AUSTROEUPATORIUM INULIFOLIUM IN
DEGRADED GRASSLANDS IN KNUCKLES CONSERVATION
AREA: ECOLOGY, IMPACTS AND IMPLICATIONS
A THESIS PRESENTED BY
INOKA PADMAKANTHI KUMARI PIYASINGHE
To the Board of Study in Earth Sciences of the
POSTGRADUATE INSTITUTE OF SCIENCE
In partial fulfilment of the requirements
for the award of the degree of
DOCTOR OF PHILOSOPHY IN EARTH SCIENCES
of the
UNIVERSITY OF PERADENIYA
SRI LANKA
2017
DECLARATION

3. iii
I do hereby declare that the work reported in this thesis was exclusively carried out by me
under the supervision of Prof. H.M.S.P. Madawala, and Dr. A.A.J.K. Gunatilake. It
describes the results of my own independent research except where due reference has been
made in the text. No part of this thesis has been submitted earlier or concurrently for the
same or any other degree.
Date:
……………………………….. ……………………………
Signature of the Candidate
Certified by:
1. Supervisor (Name): Prof. H.M.S.P. Madawala Date: ………………………………..
(Signature): ………………………………
2. Supervisor (Name): Dr. A.A.J.K. Gunatilake Date: ….....…………………………..
(Signature): ………………………………
PGIS Stamp
INVASION OF Austroeupatorium inulifolium IN DEGRADED
GRASSLANDS IN KNUCKLES CONSERVATION AREA: ECOLOGY,
IMPACTS AND IMPLICATIONS

4. iv
I. P.K. Piyasinghe
Postgraduate Institute of Science, University of Peradeniya, Peradeniya, Sri Lanka
Department of Botany, University of Peradeniya, Peradeniya, Sri Lanka
Over the last decade, Austroeupatorium inulifolium (Asteraceae) has been aggressively
invading many landscapes in the Knuckles Conservation Area (KCA) in Sri Lanka.
Cymbopogon nardus dominated grasslands are the most vulnerable. The present study
aimed at investigating ecological impacts of its invasion on these highly degraded
grasslands. The distribution mapping of A. inulifolium was also attempted using High
Resolution Satellite Images (HRSI), Worldview 2. Potential management interventions to
restore these highly invasive grasslands were investigated. Several glasshouse- and field-
based studies were conducted to explore ecological impacts of A. inulifolium.
Austroeupatorium inulifolium responded positively to temporal nutrient pulses, with high
intra-specific competition. A. inulifolium showed high competitive advantage over
Cymbopogon, confirming its high phenotypic plasticity. The use of HRSI to construct
distribution of A. inulifolium showed promising results. The study revealed that the invasion
has altered the grassland vegetation and some edaphic properties, with higher values of soil
pH, organic C, N and P reported in highly invaded grasslands (HIG). Organic C and cations
showed a significant decline from the forest interior towards the HIG. The surface litter and
standing litter biomass were significantly higher in HIG compared to less invaded
grasslands (LIG), suggesting higher litter inputs following invasion. A. inulifolium also
produced high quality litter, decayed and released nutrients rapidly than C. nardus. The
litter mixing influenced the decomposition rates and nutrient release patterns. The soil seed
bank in HIG was more abundant and richer during the wet season than that in the dry
season. Dry season soil seed bank was dominated by native species (78%) and wet season
by exotics (52%) with the highest contribution from A. inulifolium. Some management
interventions showed positive impacts on the forest regeneration. The scarcity of tree
seedlings was noticed in all treatments. However, the lack of tree seedlings was more
conspicuous in A. inulifolium removed (-Aus) treatment, further supporting the facilitative
role of the invader in the forest regeneration.
A. inulifolium seems to possess plant traits to suit the environmental heterogeneity and
disturbances prevail in these highly degraded grasslands at KCA, explaining its successful
invasion and establishment. The Worldview 2 showed promising outcome in discriminating
A. inulifolium invaded areas from the rest of the landuse types. Overall, the evidence
suggests that A. inulifolium invasion has the potential to facilitate the forest re-growth,
especially along the forest-grassland borders. With time, this ‘nursing effect’ may favour
the forest expansion towards open grassland. Changes in higher litter inputs and their
decomposition rates following invasion may influence the nutrient dynamics, ultimately
converting these highly degraded grasslands into more fertile habitats over time. The study
concludes that A. inulifolium invasion seems to incur some positive impacts on this
degraded grassland with a potential to convert it into a forested landscape eventually.
ACKNOWLEDGEMENTS

5. v
First and foremost, I am extremely grateful to my supervisors Prof. H.M.S.P Madawala,
Department of Botany, Faculty of Science, University of Peradeniya, and Dr. A.A.J.K.
Gunatilake, Department of Geology, Faculty of Science, University of Peradeniya, Sri
Lanka for their invaluable guidance and constant encouragement throughout the entire
study.
I would like to extend my sincere thanks to Prof. D.M.D. Yakandawala, Head of the
Department of Botany, University of Peradeniya and Prof. Rohana Chandrajith, Head of the
Department of Geology, University of Peradeniya for providing me facilities to carry out
this study and to all academic and technical staff for their assistance in various ways..
I am very grateful to Prof. P.R.G. Seneviratne and Dr. R. Rathnayake at the National
Institute of Fundamental Studies (NIFS), Kandy, Sri Lanka for their advices and support
during chemical analyses of soil and plant samples. I am also much grateful to the
laboratory staff at the Biological Nitrogen Fixation (BNF) Research Group including Mr. A.
Pathirana, Mrs. R.C.K. Karunarathne and all other staff at the NIFS, Kandy, Sri Lanka for
their numerous assistances. I also would like to acknowledge the support by the staff of the
Rhizobium Project, Mr. E.M.H.G.S. Ekanayake, Ms. Nayomi Ekanayake, Mrs. Dilahara
Abeyrathne, and Mr. R.K.G.K. Kumara.
I would be much appreciate the help given by Mr. S. Sivanantharajah, Senior
Superintendent of Surveys Department of Sri Lanka and Dr. Senani Karunarathne, Faculty
of Agriculture, University of Wayamba, for their assistance to conduct remote sensing
analysis. I am also grateful to Dr. Lal Samarakoon and Dr. Kavinda Gunasekara, Asian
Institute of Technology (AIT), Thailand for their assistance during the collection of spectral
signatures of Austroeupatorium using a spectrometer. Also, I am thankful to the Digital
Globe, for providing the WorldView-2 satellite imageries to be used in the study.
I would like to extend my sincere gratitude to Department of Education, for granting me
with study leave to complete my studies. I am indeed grateful to Mr. Dampiya Wanasinghe,
Former Principal, St. Thomas’ College (National School), Matale for the immense support
and encouragements given to make this effort a reality. My thanks are also extended to Ms.
Ridmi Wijerathne for covering my duties at the St. Thomas’ College (National School),
Matale during my study leave period. I am also grateful to the present Principal, Mr. K.A.J.
Kulasooriya, all former and the present staff at the St. Thomas’ College (National School),
Matale for their limitless inspirations.
I also would like to extend my thanks to the Department of Forestry, Sri Lanka for granting
me with necessary permission to conduct the field work at KCA.
I am also thankful to Dr. A.M.T.A. Gunarathne, Dr. Asanga Wijethunge, Dr. S.S. Fernando
and Mr. N. Narampanawa for helping me in numerous ways during my study. I would also
like to thank those who helped me in the field including Mr. Viduranga
Rukkaththanadeniya, Mr. Dhananjaya Wanninayake, and Mr. M.G. Jayarathne, Mr.

6. vi
Sameera Nawarathne, Mr. Wajira, Mr. Chathura Marasinghe, Mr. Lakshitha Jayasekara,
Mr. Wijitha Ekanayake, Mr. Suranga Bandara, Dingiri and Ruwan. Special thank also goes
to Mr. T. Wickramasinghe (Wicks) for taking us to the field safely and also his readiness to
help whenever the necessity arose in the field. I, undoubtedly, could not have done this
without your help under very trying conditions in the field.
I also would like say a big thank you to all my friends, Mrs. Chanaki Weerasinghe, Mrs.
Iresha Karunarathne, Ms. Supun Galappaththi, Ms. Tharangi Herath, Mrs. Vishaka
Uduwela, Mrs. Chathurika Munasinghe, Mr. Kelum Saumyasiri, Mr. Tharanga
Wijewickrama, Mr. Asanka Thilakerathna, Mr. Sripal, Mr. Tharanga Aluthwaththa and Mr.
Aravinda Bogahapitiya for their countless encouragements and support to make my study a
success.
Lastly, I would like to express my sincere thanks to all my school teachers, who
encouraged, supported and guided me to show the right direction from Grade 1 until I
entered the University. I am deeply grateful to my parents who raised me with their
unlimited love and encouragement in all aspects of my life. I would like to thank my sister,
Dr. Medha Piyasinghe and cousin brothers, Nilanga Sandaruwan, Ishara Eranga, Chanaka
Bandara, Gayan Indika and all the relations for their love and help.

7. vii
This thesis is dedicated to my loving Appachchi and Amma
TABLE OF CONTENTS
CHAPTER Page

8. viii
Declaration iii
Abstract iv
Acknowledgement v
Table of Contents viii
List of Tables x
List of Figures xi
List of Appendices xiv
List of Abbreviations xv
1 INTRODUCTION 1
2 LITERATURE REVIEW
2.1 INVASIVE PLANTS 5
2.2 ECO-PHYSIOLOGICAL TRAITS OF INVASIVE PLANTS 7
2.2.1 Plastic Responses 10
2.2.2 Effect of Density 13
2.3 PLANT INVASIONS vs SOIL NUTRIENT AVAILABILITY 13
2.4 LITTER QUALITY, LITTER LOADING AND DECOMPOSITION 14
2.4.1 Decomposition Dynamics 15
2.4.2 Chemical Composition in Leaf Litter and Nutrient Release… 16
2.5 SOIL SEED BANK UNDER INVASIONS 18
2.6 MANAGEMENT AND MITIGATION OF INVADED ECOSYSTEMS 20
2.7 KNUCKLES CONSERVATION AREA (KCA) 22
2.8 INVASION OF Austroeupatorium inulifolium IN KCA 23
3 ECO-PHYSIOLOGICAL TRAITS OF AUSTROEUPATORIUM
3.1 INTRODUCTION 25
3.2 OBJECTIVES 27
3.3 MATERIALS AND METHODS 27
3.3.1 Study Species 27
3.3.2 Experimental Design 29
3.4 RESULTS 35
3.5 DISCUSSION 45
3.6 CONCLUSIONS 50
4 MAPPING THE DISTRIBUTION OF AUSTROEUPATORIUM
4.1 INTRODUCTION 52
4.2 OBJECTIVES 54
4.3 MATERIALS AND METHODS 54
4.4 RESULTS 64
4.5 DISCUSSION 74
4.6 CONCLUSIONS 78
5 IMPACTS OF AUSTROEUPATORIUM FOR EXISTING VEGETATION
5.1 INTRODUCTION 80
5.2 OBJECTIVES 81
5.3 MATERIALS AND METHODS 81
5.4 RESULTS 83
5.5 DISCUSSION 91
5.6 CONCLUSIONS 95

9. ix
6 IMPACTS OF AUSTROEUPATORIUM ON SOIL EDAPHIC NUTRIENTS
6.1 INTRODUCTION 96
6.2 OBJECTIVES 97
6.3 MATERIALS AND METHODS 97
6.4 RESULTS 100
6.5 DISCUSSION 113
6.6 CONCLUSIONS 118
7 DECOMPSOTION RATES AND NUTRIENT RELEASE PATTERNS
7.1 INTRODUCTION 119
7.2 OBJECTIVES 120
7.3 MATERIALS AND METHODS 120
7.3.1 Quantification of Surface Litter and Standing Litter 121
7.3.2 Quantification of Litter Decomposition Rates 121
7.4 RESULTS 125
7.4.1 Surface Litter and Standing Litter 124
7.4.2 Quality of Austroeupatorium and Cymbopogon 126
7.5 DISCUSSION 137
7.6 CONCLUSIONS 140
8 REGENERATION POTENTIAL OF AUSTROEUPATORIUM
8.1 INTRODUCTION 141
8.2 OBJECTIVES 143
8.3 MATERIALS AND METHODS 143
8.4 RESULTS 146
8.4.1 Soil Seed Bank 146
8.4.2 Standing Vegetation 152
8.5 DISCUSSION 157
8.6 CONCLUSIONS 161
9 MANAGING AUSTROEUPATORIUM INVASION
9.1 INTRODUCTION 163
9.2 OBJECTIVES 165
9.3 MATERIALS AND METHODS 165
9.4 RESULTS 169
9.5 DISCUSSION 180
9.6 CONCLUSIONS 182
10 GENERAL DISCUSSION 183
REFRENCES 187
APPENDICES 225
LIST OF TABLES
Caption Page No.

10. x
Table 2.1 Causes of succession, contributing processes 21
Table 3.1 Probability values after GLM 42
Table 4.1 The WorldView-2 multispectral bands 58
Table 4.2 The area covered by different landuse classes by unsupervised
classification (ISODATA) 66
Table 4.3 The area covered by different landuse classes, given in hectares
by supervised classification 69
Table 4.4 Accuracy assessment report of the supervised classification 71
Table 5.1 Basic characteristics of the vegetation 85
Table 5.2 Abundance of plants belonging to different ecological status 89
Table 5.3 Species richness belonging to different ecological status 90
Table 5.4 Shannon-Weiner’s Index and evenness 91
Table 6.1 Pearson correlation matrix between soil nutrients 109
Table 6.2 Eigen value and accumulated proportaions of soil nutrients 109
Table 6.3 Eigen vectors of soil variables 110
Table 6.4 Factor score coefficients of selected soil variables 111
Table 6.5 Un rotated factor loadings and communalities 112
Table 6.6 Percent sand, silt and clay contents in degraded grassland 113
Table 7.1 The chemical composition and their ratios of Austroeupatorium
and Cymbopogon leaf litter 127
Table 7.2 Decay rate (days) and % nutrient remaining in LIG and HIG sites 128
Table 7.3 The chemical composition of Austroeupatorium, Cymbopogon
and mixed litter samples 131
Table 7.4 Repeated measures ANOVA results for Austroeupatorium,
Cymbopogon and their mixtures 133
Table 7.5 Decay rate (days), mass and nutrients remaining in leaf litter 134
Table 8.1 Density of germinable seeds (per m2
) 148
Table 8.2 Shannon-Weiner’s diversity index, Margalef Index 150
Table 8.3 Abundance of species and families of the standing vegetation 152
Table 8.4 The density (per m2
) of the standing vegetation 154
Table 8.5 Diversity, species richness, and evenness (Pileou’s index) 156
Table 8.6 Species richness and abundance in wet and dry soil seed banks 160
Table 9.1 Total abundance and species richness of the vegetation 170
Table 9.2 Exclusive species in each treatment 171
Table 9.3 Shannon’s diversity, evenness and species richness 173
LIST OF FIGURES

11. xi
Caption Page No.
Figure 3.1 The pots holding A. inulfifolium plants 29
Figure 3.2 A schematic diagram showing the nutrient application 30
Figure 3.3 A. inulfifolium seedlings were placed in different density levels 31
Figure 3.4 Planting patterns of seedlings of A. inulfifolium and C. nardus 33
Figure 3.5 Root, shoot weights (g) and total weights (g) of A. inulfifolium 36
Figure 3.6 Root:shoot and root weight ratio (RWR) of A. inulfifolium 36
Figure 3.7 Relative growth rate of A. inulfifolium 37
Figure 3.8 Plant height and RHR of A. inulfifolium 37
Figure 3.9 Total biomass, mean shoot and root biomass, Root Weight
Ratio (RWR) and Relative growth rate of A. inulfifolium
38
Figure 3.10 Average shoot and root biomass (g) of A. inulfifolium 39
Figure 3.11 Average total biomass and relative growth rate A. inulfifolium 40
Figure 3.12 Root weight ratio (RWR) of A. inulfifolium 40
Figure 3.13 Total biomass (g) per plant of A. inulfifolium and C. nardus 41
Figure 3.14 Root weight ratios (RWR) of A. inulfifolium and C. nardus 42
Figure 3.15 Relative growth rates of A. inulfifolium and C. nardus 43
Figure 3.16 Relative Interaction Index for A. inulfifolium and C. nardus 44
Figure 3.17 Relative Yield (RY) of A. inulfifolium and C. nardus 44
Figure 3.18 Relative height ratio (RHR) of A. inulfifolium 45
Figure 4.1 The extensive spread of A. inulifolium in and around grasslands
at KCA.
55
Figure 4.2 Location of the study site in the Knuckles Conservation Area 56
Figure 4.3 Recording of spectral measurements 57
Figure 4.4 Different band combinations in WorldView-2 multispectral
imagery
59
Figure 4.5 Dendogram generated in Knowledge Engineer 63
Figure 4.6 Flow chart indicating the methodology used in the study for
prepare the map of A. inulfifolium invaded area in KCA
64
Figure 4.7 Spectral reflectance and % spectral reflectance of A.
inulfifolium
65
Figure 4.8 A: The image produced after the Normalized differential Index
(NDVI)
65
Figure 4.9 The image produced after performing the ISODATA
clustering; After identifying different classes in KCA
66
Figure 4.10 After identifying landuse classes by unsupervised method 67
Figure 4.11 A feature space image considered; x and y axes between 1 and
8 bands in WorldView-2 imagery (0.5 m resolution)
68
Figure 4.12 Contingency Error matrix report of the supervised
classification
69
Figure 4.13 The final map produced at the end of supervised classification 70
Figure 4.14 Different band combinations of PCA image highlight different
landuses
72
Figure 4.15 Image produced after performing a DVI classification using
NIR (band-8) and RED (band-1)
73
Figure 4.16 Histogram of DVI image 73
Figure 4.17 Resultant image from the Knowledge base classification 74
Figure 5.1 Average abundance of A. inulfifolium and C. nardus 83
Figure 5.2 Stems abundance and plant densities of A. inulfifolium 84

12. xii
Figure 5.3 % Cover of A. inulfifolium 84
Figure 5.4 Average abundance of life forms in three habitats categories 86
Figure 5.5 Species richness of life forms 87
Figure 5.6 A Venn diagram showing the composition of species 89
Figure 5.7 Species accumulation curves for the all plants recorded 90
Figure 6.1 Samples were collected at different distances across the forest-
grassland edge towards the open grassland
98
Figure 6.2 Collecting soil samples in field sites 99
Figure 6.3 Percentage soil organic C, pH levels, percentage total Nitrogen
and total Phosphorus contents in KCA
101
Figure 6.4 C:N, C:P, N:P ratios at Forest grassland edge (FGE), less
invaded (LIG) and highly invaded (HIG) habitats in KCA
102
Figure 6.5 % soil organic C contents, mean soil pH and mean total
Phosphorus, in KCA.
103
Figure 6.6 Nitrate-N, Ammonium-N and percentage total N.. 104
Figure 6.7 Total mineral Nitrogen and the Nitrate : Ammonium ratios 105
Figure 6.8 C:N ratios, C:P ratios, N:P ratios, C:N:P ratios 106
Figure 6.9 Magnesium (Mg), Calcium (Ca) and Potassium (K) 107
Figure 6.10 Magnesium, Calcium and Potassium ratios with Ammonium,
Nitrate and total Phosphorus
108
Figure 6.11 Principal components of soil nutrients 111
Figure 6.12 Factors of soil nutrients (Ca, total P, C:P and N:P) 112
Figure 7.1 The single and mixed litter bags were distributed in less- and
highly-invaded grasslands
124
Figure 7.2 Surface litter biomass 125
Figure 7.3 Above ground total biomass 125
Figure 7.4 Average contribution of A. inulfifolium and C. nardus 126
Figure 7.5 Remaining mass (%) of A. inulfifolium and C. nardus 127
Figure 7.6 Decomposition rate (k) of A. inulfifolium and C. nardus 128
Figure 7.7 Remaining organic Carbon (%), Nitrogen (%) and Phosphorus
(%) of A. inulfifolium and C. nardus
129
Figure 7.8 The changes of C:N, C:P and N:P ratios of A. inulfifolium and
C. nardus
130
Figure 7.9 Decomposition rate (k) of A. inulfifolium and C. nardus 132
Figure 7.10 Remaining mass (%) as a proportion of initial weight of A.
inulfifolium and C. nardus
132
Figure 7.11 Remaining organic Carbon (%), Nitrogen (%) and Phosphorus
(%) of A. inulfifolium and C. nardus
135
Figure 7.12 Remaining C:N ratio (%), C:P ratio (%) and N:P ratio (%) of A.
inulfifolium and C. nardus
136
Figure 8.1 The locations of the four sampling sites in highly invaded
grasslands at Riverston
143
Figure 8.2 Plastic trays containing soil samples arranged in the
shadehouse
144
Figure 8.3 Monitoring and thinning of seedlings 145
Figure 8.4 A venn diagram showing the composition of species in the soil
seed bank during wet and dry season soil seed banks
149
Figure 8.5 The density of A. inulifolium seeds recorded during wet and
dry season soil seed banks
151
Figure 8.6 Cumulative and total number of A. inulfifolium germinable 152

13. xiii
seeds over the incubation period
Figure 8.7 A venn diagram showing the composition of species (A) and
plant families (B) in the sampling of standing vegetation
153
Figure 8.8 Average abundance of trees and shrubs, seedling (< 0.5 m) and
saplings (< 2m)
155
Figure 8.9 Average abundance of seedlings and saplings of total and A.
inulfifolium in the standing vegetation
157
Figure 9.1 Average temperature (ºC), precipitation (cm), Humidity and
Wind speed Km/H
166
Figure 9.2 Layout of quadrats in each plot located 167
Figure 9.3 Preparation of field plots including establishment of fire belts,
demarcation of quadrates and setting up of fences
168
Figure 9.4 Average abundance of different families in each treatment 171
Figure 9.5 Average abundance of trees and shrubs in different families. 172
Figure 9.6 Average density of different life-forms 174
Figure 9.7 Average density of different ecological status 175
Figure 9.8 Mean richness of different life forms 176
Figure 9.9 Cumulative density of different life-forms 177
Figure 9.10 Cumulative density of native, exotic and endemics 178
Figure 9.11 Some of the tree seedlings recorded at forest grassland edges 179
LIST OF APPENDICES

14. xiv
Annexure 1 Ground reference points collected from the study locations
Annexure 2 List of plant species in three habitat categories studied
Annexure 3 List of plant species recorded in wet and dry soil seed bank
Annexure 4 List of plant species recorded in the standing vegetation
Annexure 5 Plant families and species recorded in each treatment made
Annexure 6 Life form, ecological status and their conservation status
Annexure 7 List of exotic species recorded in forest grassland edges in KCA
LIST OF ABBREVIATIONS

15. xv
ANOVA Analysis of Variance
AOI Area of Interest
DVI 'Difference Vegetation Index
FGE Forest-Grassland Edge
GIS Geographic Information System
GISP Global Invasive Species Programme
GLM General Linear Model
GPS Global Positioning System
Ha Hectare
HIG Highly-Invaded Grasslands
IAS Invasive Alien Species
IHS Intensity, Hue, Saturation
ISDB Invasive Species Data Base
ISODATA Self-Organizing Data Analysis Technique
KCA Knuckles Conservation Area
LIG Less-Invaded Grasslands
NDVI Normalized Differential Vegetation Indices
NIFS National Institute of Fundamental Studies
NIR Near Infra-Red
NISIC National Invasive Species Information Center
OCC Organic Carbon Content
PCA Principal Component Analysis
R/S Root to Shoot ratios
RGR Relative Growth Rate
RHR Relative Height Ratio
RII Relative Interaction Index
RS Remote Sensing
RWR Root Weight Ratios
RY Relative Yield
UNESCO United Nations Educational, Scientific and Cultural Organization
US United Estates
UTM Universal Transverse Mercator