Ignition Grant Round 7 (July 2017)

• Elle Bowd, ANU PhD student
• David Lindenmayer, ANU
• Sam Banks, ANU
• Andrew Bissett, CSIRO
• Tom May, Royal Botanical Gardens, VIC

In this project, we will use DNA and RNA-based metabarcoding approaches to characterize spatial and temporal variability in the soil communities of montane eucalypt forests.

We have designed a sampling regime to test the impacts of natural and human disturbance (fire and logging), and post-disturbance succession, on these critical yet poorly understood communities. As part of the research, we will evaluate RNA-based metabarcoding approaches for evaluating temporal changes in the ‘genomically-active’ component of these communities under different ecological conditions.

The project will form part of Elle Bowd’s PhD and link with a long-term biodiversity research program in Victorian mountain ash forests led by David Lindenmayer and Sam Banks, as well as the nationwide Biome of Australia Soil Environments (BASE) project.

This project examines two important, yet often overlooked underground communities: soil seed-banks and fungi. Frequently neglected in ecological monitoring, conservation and research, these communities underpin many processes influencing above ground communities and broader ecosystem health. For example, mycorrhizal fungi form symbiotic relationships with approximately 86% of plant species, assisting in nutrient acquisition, in turn, increasing plant productivity and seedling survival.

Soil seed-banks also play an important role in the succession, composition and persistence of plant species, particularly following disturbance. Disturbances such as fire and logging can alter fungal communities and soil seed-banks by mechanical disturbance, sterilisation of the soil, or indirectly by affecting soil composition and chemistry. Due to the interconnectedness of these underground and aboveground communities, changes in species composition will produce a cascading effect on ecosystem function.

The aim of this project is to fill research gaps by addressing the following questions:

1. What is the effect of time since fire on soil seed-banks and fungal communities along a chronosequence spanning 150 years in Mountain Ash forests? and
2. How does the composition of fungal communities and soil seed-banks compare post-fire to the composition of communities in areas subject to clear-fell logging in similarly aged Mountain Ash forests?

These questions are important from a ‘pure discovery’ perspective because very little is known about the biodiversity of soil communities. Further, they are important from a conservation perspective because the natural and anthropogenic disturbance regimes in montane eucalypt forests are changing rapidly.

Natural fire regimes are integral to the function of Australian ecosystems. However, when fire severity or frequency occurs outside ‘normal’ conditions an ecosystem can become compromised. This effect is amplified when additional disturbances are evident, such as in the Mountain Ash forests of the Victorian Central Highlands. These forests are highly disturbed, having experienced frequent wildfire over the past century and clear-fell logging since the 1960’s. In addition, rainfall in the region has decreased and temperatures have risen consistently over the last century. As a result of this intensive disturbance regime, previous research has indicated adverse effects in above ground communities. However, little is known about the effects of disturbance on below-ground soil communities.

Soil seed-banks and fungal DNA will be collected from 90 sites, ten replicates of Victorian Mountain Ash forest last burnt in 2009, 1983, 1939, 1850, forest last clear-felled in 2009 and 1980 and salvaged logged in 2009. Data collection has been separated into two field seasons. The first was conducted from November 2016-Feburary 2017, where soil samples were collected to analyse fungal communities. The second field season to sample soil seed-banks will commence in late 2017/early 2018 before the onset of seeding of standing vegetation, to ensure seeds have persisted in the soil since summer 2016 or earlier.

This project takes advantage of next generation DNA sequencing technologies, allowing the novel identification of fungal communities from soil sample. Alongside DNA samples, additional samples of soil were taken to analyse RNA, allowing the identification of the most active fungal communities. Soil seed-banks will be germinated under a variety of greenhouse conditions to stimulate germinant growth. Additionally, the projective cover of all vascular plants will be recorded and extensive soil chemistry analysis conducted for each site to examine possible interactions.

This research will generate crucial baseline data on the successional trajectories of fungal communities and soil seed-banks, and test the long-term effects of fire and logging on these communities. Contributing to 34 years of long-term monitoring in these Australian Mountain Ash forests, this research will provide important new insights into forest and land management, particularly with respect to the conservation of fungal communities and soil seed-banks and, in turn, the maintenance of the vitally important functional services they provide.