Nottingham Trent University Different Land Use Effect
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NOTTINGHAM TRENT UNIVERSITY DIFFERENT LAND USE EFFECT ON EARTHWORMS AT SAFE PROJECT SITE IN SABAH, BORNEO by SRI VENKATESWARA RAO Dissertation submitted in partial fulfilment of the MSc. Endangered Species Recovery & Conservation 2013 Abstract Earthworms are a major component of the soil biota as ‘ecosystem engineers’ sensitive to disturbance and the impact of deforestation on earthworms remains as one the least studied subject in tropical Borneo whose rainforest is fast disappearing due to logging and intensive agriculture. As such, this study investigated the impact of land use disturbance on earthworms by comparing their abundance per m2 across forest modification gradient and measured changes in environmental variables across the gradient and their subsequent effect on earthworms. Old growth (OG2), secondary logged forest (B and F) and oil palm (OP2 and OP3) sites were surveyed in SAFE Project site in Sabah, Borneo. Transect and monolith digging methods were employed to sample earthworms from soil. At each monolith, environmental variables were measured to characterise each land use by canopy exposure, litter depth and forest quality and soil samples were taken to analyse soil properties. Earthworm abundance was highest in OG2 and decreased across the disturbance gradient and was significantly lower in OP2 indicating some level of tolerance between old growth and secondary forest system. However, functional group response and changes in functional group composition varied significantly between land uses and corresponded significantly to variation in environmental variables which also significantly differed between land uses. Changes in functional group response potentially show greater implication for soil function and the ecosystem services derived from the processes. Therefore, further investigation on impact of functional group composition changes on soil function due to different land use is needed. i Acknowledgements I would like to express my gratitude to Stability for Altered Forest Ecosystem (SAFE) and Sime Darby Foundation for granting permission and providing funding to support my study. I also appreciate the support and advice from my project supervisor Dr Samantha bremner-Harrison and Dr Rob Ewers, SAFE Science Director. Special thanks to Dr Glen Reynolds from SEARRP for sorting out my permit issues – without which this project could not have taken place. Also, thanks to Dr Somsak Panha from Chulalongkorn University who has generously offered his assistance to do the specimen identification. I am also grateful to Khoo Min Sheng, Project Coordinator; Sarah Watson, Deputy Project Coordinator and Johnny Larenus, Field Manager for arranging all my logistics, last minute requests and for providing me additional research assistants that crucially helped me make up for lost time. Another special thanks goes to Dr Ed Turner and Sarah Luke from Cambridge University; Dr Paul Eggleton and Dr David Jones from Natural History Museum; Dr Rory Walsh from Swansea University; Dr Patrick Lavlle for sharing their research data, expertise and making suggestions. My heartfelt thanks to all research assistants especially Harbin, Sabri, Melvin, James, Daniel, Matiew, Siun, Zinin and Alex – for assisting me to get all the data I needed within a short period of time. My personal thanks to my family, Sharmila, Viv, Katie, Susan, Brian, Abby, Graham, Jose, Judy and Marcelle for all you moral support. Finally, special thanks to Dena, Rosa, Katie, Anand, Hardy, Gilbert, Architrek and other fellow researchers at SAFE for making my stay at Maliau and SAFE a memorable one. ii Abstract i Acknowledgements ii Table of Contents iii List of Figures v List of Tables vi List of Photographs vii Chapter 1 Introduction, literature review, aims 1 1.1 Introduction 1 1.2 Literature review and aims 2 1.2.1 Background 2 1.2.2 Earthworm communities and role 3 1.2.3 Land use impact on earthworms 5 Chapter 2 Materials and methods 7 2.1 Study site 7 2.2 Land use characteristics 9 2.3 Data collection 10 2.3.1 Earthworm sampling 11 2.3.2 Earthworm functional group identification 12 2.3.3 Measurement of environmental variables 13 2.4 Analyses 17 2.4.1 Difference in earthworm and functional 18 group abundance 2.4.2 Difference in environmental variables 18 between land use 2.4.3 Relationship between earthworm abundance 19 and environmental variables 2.4.4 Relationship between environmental variables 19 Chapter 3 Results 20 3.1 Earthworm abundance between land use type 20 3.1.1 Total abundance 20 3.1.2 Functional group abundance 20 3.2 Changes of environmental variables across different 23 land use 3.3 Association between environmental variables and 25 earthworm abundance 3.4 Association between environmental variables 25 3.5 Relationship between environmental variables and 28 earthworm abundance iii Chapter 4 Discussion 30 4.1 Land use effect on earthworm abundance 30 4.2 Influence of environmental variables on earthworms 32 4.2.1 Soil temperature and moisture 32 4.2.2 Soil pH 33 4.2.3 Habitat quality 33 4.2.4 Interdependence between forest quality, 34 Canopy cover, SOM and effect on earthworm abundance 4.2.5 Effect of soil compaction on earthworms 35 4.2.6 Top soil influence on earthworms 36 4.2.7 Different management in oil palm effect 37 on earthworms 4.3 Earthworms and soil function 37 4.3.1 Feeding behaviour – Selection of soil 38 particles 4.3.2 Compacting vs decompacting action by 39 earthworms 4.3.3 Burrowing, ingestion and cast production 39 effect on soil 4.3.4 Turnover of soil 41 4.3.5 Earthworms effect on decomposition, SOM, 42 above ground vegetation and forest ecology 4.4 Study limitations & future recommendations 43 4.4.1 Transport permit and species ID issues 43 4.4.2 Sampling design 44 4.4.3 Exclusion of earthworm biomass data 45 4.4.4 Bulk density estimation 45 4.4.5 Soil chemical properties analysis 46 4.5 Potential future studies 46 Chapter 5 Conclusion 47 References 48 Appendix I 57 Appendix II 58 Appendix III 59 Appendix IV 60 Appendix V 62 iv List of Figures Figure 2.1 Location of sampling sites at SAFE project site. Page 8 Figure 2.2 Detailed location of 2nd order sampling points. Page 9 Figure 2.3 Schematic representation of transect Page 12 Figure 2.4 Spectrum of increasing SOM level with respective Page 16 score. Figure 2.5 Different level of data used for analyses. Page 18 Figure 3.1 (a) Changes in mean abundance of earthworm functional Page 22 groups per land use. Figure 3.1 (b) Comparison in mean abundance per m2 of total, adults Page 22 and juveniles per land use. v List of Tables Table 2.1 Land use intensity gradient per land use. Page 10 Table 2.2 SAFE project standardised forest quality scale. Page 17 Table 3.1 Mean earthworm abundance per m2 comparison between Page 23 land use. Table 3.2 Difference in environmental variables between land use. Page 24 Table 3.3 Association between environmental variables and Page 26 earthworm abundance. Table 3.4 Association between environmental variables. Page 27 Table 3.5 Relationship between earthworm abundance and Page 29 environmental variables. vi List of Photographs n/a vii Chapter 1 Introduction, literature review, aims 1.1 Introduction The tropical rainforest of Borneo is a megadiverse region that is fast disappearing due to logging and intensive agriculture that have caused significant changes to species diversity and composition across the modification gradient (MCMorrow & Talip, 2001). Many taxa that make up the natural ecosystem are being lost due to this process while their natural patterns and ecological significance is little understood. One of such taxa is the earthworm - a major component of the soil biota as ‘ecosystem engineers’ and their presence plays a dominant role in the regulation of soil processes, fertility and function (Nellemann et al. 2007). Studies have shown that despite patchy distribution and low densities in the tropics, earthworms occur in high diversity and represent an important biomass of the food web in soil while playing vital role as soil engineers in soil ecosystem influencing soil processes (Fragoso & Lavelle, 1987, 1992, 1995; Lavelle & Spain, 2001). Moreover, earthworms are also sensitive to land use changes as communities can be modified both at functional and taxonomic level over different land conversion (Senapati, 1980; Lavelle & Pashanasi, 1989; Julka, 1988; Fragoso et al. 1993; Lavelle et al. 1994a; Decaëns & Jiménez, 2002; Nunes et al. 2006; Susilo et al. 2009). Of particular interest is the response of earthworm functional/ecological groups: epigeic, anecic and endogeic which are classified based on their feeding and how deep they burrow in the soil (Bouché 1977, Lavelle 1981). Epigeic are litter dwelling species that feed at the surface level; endogeic are soil dwelling species that feed in the mineral soil and build their semi- permanent burrows to about 50cm depth; anecic are deep burrowing species that can go down to 2 meters depth but feed on surface by pulling down fresh litter into its burrow. The different activities of each group can cause different effects on the soil and studies confirm that functional 1 group response to disturbance may differ greatly and alter biogeochemical processes (Lee, 1985; Lavelle, 1983; Blanchart et al. 1997; Fargoso et al. 1997; Lavelle et al. 1998). 1.2 Literature review and aims 1.2.1 Background Forest clearance for land development continues throughout the world and the increasing human population puts more and more pressure for land needed for cultivation, residence and industry. As such, study on the impact of forest clearance, land use type and subsequent practises are relevant and valuable in assessing the impact and extend of such activities on flora and fauna. Earthworms are one of the taxa greatly impacted by changing land use and first started to become widely studied in temperate regions.