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Influence of soil fertility, drought, and host plant on fine root endophytes along a 2-million-year soil chronosequence

Mansfield, Thomas (2019) Influence of soil fertility, drought, and host plant on fine root endophytes along a 2-million-year soil chronosequence. Honours thesis, Murdoch University.

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Understanding of fine root endophytes (FRE) (Planticonsortium tenue) ecology and especially the drivers of colonisation, diversity and community assemblage is limited. Field observations suggest that they are specialised to occur within extreme environmental conditions. I investigated the influences of drought (water availability), soil fertility (chronosequence stage) and host species on colonisation (abundance), diversity, and community assemblage of FRE using a glasshouse experiment. I planted seedlings of Microlaena stipoides Labill (weeping grass) and Trifolium subterraneum L. (subterranean clover) in soils collected from four soil ages of a 2-million-year soil chronosequence, which is phosphorus (P) limited and experiences lower nutrient availability in the youngest and oldest stages. I also included a drought treatment which was initiated for half of the pots from week 4; plants were harvested in week 10. Fine root endophytes showed consistent responses in relation to chronosequence stage. Root colonisation was higher within the two most P-limited stages (i.e. youngest and oldest). Community assemblage was found to change, and richness was highest in the youngest and oldest stages. Fine root endophytes were not observed to colonise M. stipoides Labill when using microscopy. However, FRE were found in the roots via DNA sequencing, suggesting some FRE might not be visible with the staining and microscopy techniques used. Other non-mycorrhizal fungi belonging within Mucoromycotina may also have been present in and around the roots and contributed to this finding. Drought was found to have no effect on FRE, potentially due to P being more limiting than water in this system. Responses of FRE differed to arbuscular mycorrhizal fungi (AMF) and colonisation and richness were consistently lower. Overall, my results show that abundance and diversity of FRE follow the opposite trend than available P across this chronosequence. This shows that FRE can potentially be suited to P limited soils. More studies are needed to understand the generality of these findings. Drought had no influence on FRE in my experiment. My data suggest FRE may have different ecological roles to AMF such as specialisation in highly P limiting soils. However, there is also potential for the co-occurring fungi to share some ecological similarities like preference for low P soils.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): Environmental and Conservation Sciences
Supervisor(s): Standish, Rachel, Ryan, Megan and Albornoz, Felipe
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