Sabais, Alexander Christian Wolf
Collembola in a plant diversity gradient: Interactions between the aboveground and belowground system.
Technische Universität, Darmstadt
[Ph.D. Thesis], (2012)
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|Item Type:||Ph.D. Thesis|
|Title:||Collembola in a plant diversity gradient: Interactions between the aboveground and belowground system|
During the past few decades, there has been growing understanding that human well-being is fundamentally linked to the state of the environment. The rapid decline of global biodiversity and its consequences for ecosystem functioning therefore has become a focal point of scientific interest and prompted a multitude of biodiversity studies aiming to investigate the complex relationship between plant species richness and ecosystem functioning in terrestrial grassland ecosystems. However, the majority of these studies predominantly focused on the aboveground aspects of terrestrial ecosystems such as plant productivity, neglecting the role of the belowground decomposer community as an important driver of fundamental ecosystem processes. Soil microorganisms and decomposer animals control decomposition processes and nutrient mineralization in soil, processes that are key determinants for plant performance and ecosystem functioning. Collembola are among the most important microarthropods in terrestrial ecosystems as they are known to affect ecosystem processes and plant nutrition by a variety of direct and indirect mechanisms. The present thesis was conducted within the framework of the Jena Experiment, a large biodiversity experiment aiming to investigate the impacts of declining plant diversity on ecosystem processes and trophic interactions in grassland ecosystems. The overall objective of my thesis was to investigate the effects of plant species richness, plant functional group richness and particular plant functional groups on Collembola communities in temperate grassland and to explore the main mechanisms by which Collembola in turn affect plant communities. These questions were addressed in a field study and two greenhouse experiments. The intentions of the field study were to assess the effects of plant species richness, plant functional group richness and plant functional identity on the structure of Collembola communities in temperate grassland and if plant community effects on Collembola vary with season. Collembola density and diversity significantly increased with plant species and plant functional group richness, highlighting the importance of the singular hypothesis for soil invertebrates. Generally, grasses and legumes beneficially affected Collembola density and diversity, whereas effects of small herbs usually were detrimental. These impacts were largely consistent in spring and autumn. The results indicate a distinct time-lag of the response of Collembola to vegetation manipulations, suggesting that effects of plant functional group identity on the belowground system are more immediate whereas effects of plant species and plant functional group richness will become important in the long-term. The first greenhouse experiment investigated how plant productivity and decomposition processes are influenced by Collembola diversity and if effects of Collembola vary with plant functional group identity. Collembola decreased soil surface litter decomposition whereas root litter decomposition was enhanced. Furthermore, Collembola diversity changed root depth distribution in a plant functional group specific way, indicating distinct changes in plant competition due to changes in Collembola diversity and composition. However, effects of Collembola on plant performance appeared to be idiosyncratic and point to strong context-dependent interactions among Collembola species, such as facilitation or competition for nutrients and living space. The results therefore suggest that changes in Collembola diversity may have unpredictable consequences for ecosystem functioning. The aim of the second greenhouse experiment was to investigate effects of Collembola and arbuscular-mycorrhizal fungi (AMF) on plant competition and the performance of Lolium perenne, Plantago lanceolata and Trifolium pratense representing three dominant plant functional groups (grasses, herbs and legumes). Further, we investigated variations in Collembola performance and AMF colonization rates of plant roots as influenced by the different plant communities. Collembola did not affect total colonization of roots by AMF but increased the number of mycorrhizal vesicles in P. lanceolata. AMF and Collembola both enhanced the amount of N and P in plant shoot tissue, but impacts of Collembola were less pronounced in the presence of AMF. Overall, the results suggest that AMF and Collembola interact in affecting plant competition. Presence of AMF modulated plant specific effects on Collembola and increased the competitiveness of P. lanceolata and T. pratense against L. perenne, pointing to a loose inter-kingdom mutualistic relationship between plant, mycorrhiza and Collembola. The results demonstrate that Collembola and AMF interactively impact the competition between plant species by differentially but concordantly affecting nutrient acquisition of the plant. The insights of the present thesis corroborate the importance of the belowground community for ecosystem functioning and human well-being by highlighting the interactions within the different levels of soil biota.
|Place of Publication:||Darmstadt|
|Collation:||XXIV, 135 S.|
|Uncontrolled Keywords:||Biodiversity, Collembola, Springtails, Plant Species Richness, Plant Functional Groups, Diversity, Mykorrhiza, The Jena Experiment, Greenhouse Experiment|
|Classification DDC:||500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
500 Naturwissenschaften und Mathematik > 580 Pflanzen (Botanik)
500 Naturwissenschaften und Mathematik > 590 Tiere (Zoologie)
|Divisions:||10 Department of Biology|
|Date Deposited:||29 May 2012 09:12|
|Last Modified:||07 Dec 2012 12:05|
|Referees:||Scheu, Prof. Dr. Stefan and Blüthgen, Prof. Dr. Nico and Schwabe-Kratochwil, Prof. Dr. Angelika and Schüth, Prof. Dr. Christoph|
|Refereed:||16 April 2012|