þlele6 COMPETITION BETWEEN EARTHWORMS IN HIGH PASTURES IN THE MT. LOFTY RA}iGES, SOUTH AUSTRALIA Paul Reginald Dalby B.Sc. @linders) Thesis submitted for the degree of DOCTOR OF PHILOSOPHY m The Universþ of Adelaide (Faculty of Agricultural and Natural Resource Sciences) Department of Soil Science \Maite Campus The Universþ of Adelaide April 1996 TABLE OF CONTENTS LIST OF F'IGURES tx LIST OF TABLES xtx ST]MMARY xxlv DECLARATION xxvu PT]BLICATIONS I'ROM THE THESIS xxvut ACKNO!VLEDGMENTS xYlx Chapter 1 INTRODUCTION AND LIïT'RATIIRE REVIEIV I 1.1. Introduction I 1.2. Basic biology of earthworms 2 I. 2. I Ecological groupings 2 I. 2. 2 Population biologtt 4 1.2.3 Growth 5 1.2.4 Dispersal I 1.3. Earthworms as keystone species in agricultural soils 9 1.3.1 Changing soil structure 10 I. 3. 2 ModiLving decomposer communilv structure 11 I. 3. 3 Altering energt and nutrient ÍIows 13 1.3.4 Efrects on the composition oÍplant communities t4 1.4. Manipulating earthworm communities for agriculture l4 1.4.1 Irish peat bogs. reclaimed polders in the Netherlands and New Zealand pastures t4 1.4.2 Australian high rainÍall pastures 16 1.5. Potential impediments to introducing earthworms into Australian high rain-fall pastures 18 1.5.1 Abioticfactors 18 1.5.2 BioticÍactors 19 ll I - 5. 2. I Plant communities 19 I. 5. 2. 2 Predators, pathogens and parasites 20 1.5.2.3 Food 20 1.6. Competition - a potential impediment to introducing earthworms 30 1.6. I Competition theory 31 1. 6. I. I Scramble competition 31 1.6.1.1.1 Measuring niche overlap 32 1.6.1.1.2 Coexistence of species using the same resources 33 I . 6. I. 2 Interference competition 35 1.6.2. Detection and measurement of competition 36 1.6.3 Do eartlnvorms compete? 38 1.7. Summary 42 Chapter 2 - SITE DESCRIPTIONS' COMMON METIIODS AI\D VALIDATION OF METHODS. 44 2.1. Introduction. 44 2.2. Description of field sites. 44 2.2.1 Deep Creek Conservation Park 44 2.2.2 Mwonga 47 2.2.3 Maccleqfreld 52 2.2.4 Sprinsmount 52 2.2.5l4toodside 52 2.3. Description of commonly used methods 55 2.3.1 Field cages tt 2.3.2 Undisturbed soil cores for laboratory e periurettrlË 55 3 moisture to saction 59 2.3.3.1 Determiningwater potential using thefilter paper method 60 lll 2.3.3.2 Springmount - mixed soil 6t 2.3.3.3 Springmount, Woodside and Deep Creek - unmixed soil 6t 2. 3. 3. 4 "Artificial" soil 65 2.4. Assessing a "filter paper method" for pre-treatment of earthworms to remove soil from their intestines and to standardise the water content of their tissue 70 2.4.1 Introduction 70 2.4.2 Material and methods 73 2.4.3 Results and Discussion 76 2.5. Assessing the safety of three biocides for use in pot and field experiments 80 2.5.1 Introduction 80 2.5.2 Material and methods 81 2.5.3 Rentlts and Discassion 85 2.6. Obtaining earthworm free, undisturbed soil which is safe to use in pot experiments 87 2.6.1 Introduction 87 2.6.2 Material and methods 89 2.6.3 Results 90 2.6.4 Discussion 94 2.7. Conclusions 95 Chapter 3 - THT'. EFFECT OF SPECIES INIERACTIONS ANI) soIL DTSTURBANCE ON SURVTVAL, GROWTH AND REPRODUCTION OF THREE SPECIES OF EARTHWORMS 96 3.1 Introduction 96 3.2 Laboratory experiments 97 3.2.1 Materials and methods 97 lv 3. 2. I . I Interactions between A. caliginosa. A. trapezoides and A. rosea - 1993 98 3.2.1.2 Interactions between A. caliginosa, and A. trapezoides - 1995 100 3.2.1.3 Data analysis 100 3.2.2 Results 101 3.2.2.1 Interactions between A. caliginosa. A. trapezoides and A. rosea - 1993 101 3.2.2.2 Interactions between A. caliginosa. ønd A. trapezoides - 1995 10ó 3.3Interactions betweenA. trapezoídesrA. calíginasø and A. rosea at Springmount 120 3.3.1 Materials and methods 120 3.3.1.1 1993 - mixed soil L20 3.3.1.2 1994 - mixed soil 122 3.3.1.3 1995 - unmixed soíl t24 3.3.1.4 dnta analysis 124 3.3.2 Results 126 3.3.2.2 contamination by resident earthworms 126 3.3.2.2 1993 - mixed soil 126 3.3.2.3 1994 - mixed soil 129 3.3.2.4 1995 - unmixed soil 133 3.4 Intraspecific competition between individuals of,,4. trapezoídes at Springmount in unmixed soil (1993) 133 3.4. I Materials and methods 133 3.4.2 Results 135 3.5 Interactions between A. trapezoídes and, A. rosea. at Macclesfield and Myponga in unmixed soil (1993) t37 3. 5. I Materials and methods 137 3.5.2 Results 137 3.5.2.1 Macclesfield 137 3.5.2.2 M¡tponga 138 3.6 Comparison of growth and survival between experiments 139 3.7 Discussion t4t 3.74.1 Pot experiments t4t 3. 7. 2 Interactions experiments at Springmount 144 3.7.2.1 Contømination 144 37.2.2 Smaller eartlworms gain more weight t45 v 145 145 148 150 152 t55 Chapter 4 - INTERACTIONS BET\ryEEN APORRECTODEA LONGA AI{D OTHER SPECIES IN PASTT]RES 157 4.1 Introduction 157 4.2Pot experiment - Interaction between A. longø and A. cølígínosø 158 4. 2. I Materials and methods 158 4.2.2 Results 159 4.3 Fietd experiment at Springmount - effect of A caligínosø, A. trapezoídes anìl A. roseø on A. longø 163 4. 3. I Materials and methods 163 4.3.1.1 1994 - mixed soil 163 4.3.1.2 1995 - unmixed soil 164 4.3.2 Resuhs 165 4.3.2.1 1994 - mixed soil 165 4.3.2.2 1995 - unmixed soil 168 4.4 Interactions betw een A. longa and M. dubius 173 4.4.1 Materials and methods 173 4.4.1.1 \Yoodside 1994 - Eflect on resident M. dubius t7s 4.4.1.2 Pot experiment - Effect on M. dubius t7s 4.4.2 Results 175 4.4.2.1 Woodside 1994 - Effect on resident M. dubius 175 4.4.2.2 Pot experiment - Effect on M. dubius 175 4.5 Does A. longø consume M. dubìus cocoons? 179 4. 5. I Materials and methods 179 4.5.1.1 Does A. longa consume M. dubius cocoons? L79 4.5.1.2 Can A. longa confltme artificial spheres of similar size to M. dubius cocoons? 181 4.5.2 Results 183 4.5.2.1 Does A. Ionga con&tme M. dubius cocoons? 183 vl 4.5.2.2 Can A. Ionga consume artificial spheres of similar size to M. dubius cocoons? 183 4.6 Discussion 186 4.6.I Interactions between A. longa and other species 186 oÍ A.longa 190 4. 6. 3 Implications -for introducing A. longa 190 4.7 Conclusions 191 Chapter 5 - \VILL APORRECTODEA LONGA POSE A THREAT TO NATIVE STRINGYBARK FORESTS IN THE MOT]NT LOFTY RANGES? I92 5.1 Introduction 192 5.2 Survey of resident populations in forest and pasture soils 194 5.3 Survival, growth and reproduction of A. bngø and its effect on protozoa and mesofauna 194 5.3.1 Materials and methods t94 5.3.1.1 Pot experiment - Performance o/4. Ionga ønd effects on soilfauna 194 5.3.1.2 Field experiment - Performance of A. longa in comparison to 198 5.3.2 Remlts 200 5.3.2.1 Pot experiment - Performance of A. longa ond effects on soilfauna 200 5.3.2.2 Field experiment - Performance of A. longa in comparison to A. caliginosa 203 5.4 Does A. longa affect the native earthworm G. laterølis? 203 5. 4. I Materials and methods 203 5.4.1.1 Optimal density of G. Iateralis 203 5.4.1.2 Interactions between A. Ionga and G. lateralis in pots 208 5.4.2 Results 209 5.4.2.1 Optimal density of G. lateralis 209 5.4.2.2 Interactions between A. longa ond G. Iateralis in pots 215 vll the highest survival, growth and reproduction? 209 5.4.2.2 Interactions between A. longa and G. lateralis in pots 215 5.5 Does A. longa prefer to be in soil from the native area or from the adjacent pasture? 217 5.5.1 Materials andmethods 217 5.5.2 Resalts 219 5.6 Effect oI A. longa on movement of A. fiapezoídes and A. calíginos¿ from pasture soil to native soil 219 5.6.1 Materials andmethods 219 5.6.1.1 Does¿!-longgforce A. trapezoides or A. caliginosa out of pasture soil into native soil? 219 5.6. 1.2 Does A. trapezoides øvoid mucas from A. longa? 222 5.6.2 Results 222 5.6.2.1 Does!,Jengforce A. trapezoides or A. caliginosa out of pasture soil into native soil? 222 5.6.2.2 Does A. trapezoides avoid mucusfrom A. longa? 224 5.7 Discussion 224 5.7.1 Growth. survivalandreproductionoÍA.longa 224 5.7.2 Effect oÍ A.longa on notivefauno 226 5.7.2.1 Effect of A. longa on mesofauna and protozoa 226 5.7.2.2 Survival, growth andreprodttction of G. lateralis 227 5.7.2.3 Effect of A. Ionga on G. Iateralis 227 5.7.3 PreÍerence ol A.longaÍor native soil 228 5.7.4 Efrect oÍ A.longa on movement ol A. trapezoides and A. caliginosa 228 5.8 Conclusions 229 Chapter 6 - WHY DID EARTH1ryORMS PERFORM BETTER IN T]MD(ED SOIL COMPARDD TO MIXED SOIL? 230 6.1 Introduction 230 6.2 Sheep dung: banded at the surface or mixed evenly through the soil 231 6.