Field sampling in a newly established Kiwifruit site in Te Kaha
Soils are vulnerable to disturbances such as land-use change and climate change, which can impact their health and function. Microbial communities can help to mitigate these impacts, but our knowledge of which microbial populations are important for soil resistance and resilience, and whether these populations can be stimulated or transferred, is lacking.
PhD student Alana Thurston is looking for answers to these questions by studying soil microbes under maize and kiwifruit sites across Te Kaha in the eastern Bay of Plenty. The area has been largely covered in a maize monoculture since the early twentieth century. Some areas have more recently been converted to kiwifruit, resulting in a patchwork of agricultural uses, ideal for studying the effect of land use on soil microbes.
Alana’s first stage of research aimed to characterise the baseline soil microbe communities under maize and kiwifruit. She measured the chemical and physical properties of the soil, the size and activity of the microbial populations, and the diversity of the microbial populations across different seasons.
Her data shows that soils under kiwifruit have higher carbon and nitrogen levels, as well as micronutrients like calcium, than maize. Kiwifruit soils also have a higher total biomass of soil microbes than maize soils.
Alana is currently analysing the soil community composition, which may be important because resilient soils tend to have higher microbial diversity and thus functional similarity. Functional similarity means that multiple organisms conduct the same job (such as carbon cycling or nitrogen fixing), so if one species goes extinct, the other organisms can still maintain those functions.
Alana is especially interested to see whether microbial communities in her samples taken right after 2023 Cyclone Gabrielle are different from the other samples, which could hint at the potential longer-term impacts of climate change on soil microbial diversity.
Alana’s next step will be to conduct lab experiments to monitor how soil microbes recover over time after being disturbed by a simulated drought, which is one predicted impact of climate change in Te Kaha.
PhD student Alana Thurston (Lincoln University) bagging research samples
To do this, Alana transported 40kg bags of soil back to her lab at Lincoln University, where she simulated the impacts of drought. At specific time intervals post-drought, she measured the carbon dioxide respiration of the soils, which is a proxy for how active the microbial community is.
Alana is now doing genetic analyses to determine the effects of the simulation on community composition, as well as testing the impacts of multiple drought events, which might select for certain organisms that are drought tolerant.
Alana describes this as a good first step to look at how microbes respond to potential changes to climate. It will help us predict whether agricultural soils are likely to bounce back after disturbances, and how soil microbial diversity can be enhanced, especially under monocultures.
Alana will be submitting her PhD in February. She says that one of the things she has enjoyed the most about Bioprotection Aotearoa is the dialogue that has been fostered between scientists and Indigenous communities.
“The Te Kaha community has been excellent to work with, and they really helped to shape my research questions,” Alana says.
She says that Bioprotection Aotearoa has also taught her the importance of being on the ground, making connections and taking the time to build relationships.
“It’s quite easy as a scientist to just read the literature and feel you know what is going on, but talking with people about their lived experiences with the land and the history of the land makes you realise there are some things you can’t find online.”
More Information
Dive deeper into this fascinating research of soil microbial communities here > Microbial communities and their relationships to soil resistance and resilience
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