Dryland ecosystems cover about 40% of the Earth’s land and support more than 2 billion people, and once they’re compromised — from overgrazing or inadequate irrigation — they’re difficult to recover. A technique for restoring native plant ecosystems “direct seeding” is promising, but has many drawbacks.
“For degraded arid areas, only about 10% of directly sown seeds reach establishment,” said lead author of the study published in the Journal of Applied Ecology, Frederick Dadzie, Ph.D. candidate at UNSW Sydney’s School of Biological, Earth & Environmental Sciences. “And since native seeds are expensive and often in short supply at the required scales, this is problematic.”
Because one of the potential problems of degraded arid areas is the absence of native microorganisms in the soil, the research team obtained and grew native bacteria from undisturbed sites. They then introduced them to soil pellets containing the seeds of native plants — a spinifex and the fireflies (an acacia) — and planted them in degraded arid areas.
Microorganisms can have macro benefits
“We found that microorganisms were very beneficial for growing the plants, especially in the early stages when it was just seeds making a seedling. After that, the relationship was less clear,” says Mr. Dadzie.
The success of acacia seed germination, in combination with native microbes, was improved by approximately 50%. Also of the spinifex the germination rate was improved by about 20%, but only in combination with cyanobacteria (bacteria that carry out photosynthesis).
However, after germination, the presence of native bacteria had no positive or negative impact on plant survival. In fact, the average mass of the spinifex was reduced by 11% for those seeds containing cyanobacteria.
“That microbes improve germination in degraded habitats is good news for ecosystem recovery,” said Mr. Dadzie. “And what’s even better, this is a simple two-step process that can be scaled up for restoring ecosystems in arid regions. First, combining the seeds and soil into pellets, and second, grafting those pellets with the microbes.”
Exactly which native bacteria were present in the soil grains was not known, but there are a range of mechanisms by which bacteria can improve (and hinder) the germination and growth rate of plants.
“Microorganisms use different mechanisms to improve plant growth, both directly and indirectly. For example, microorganisms contribute to the infiltration and retention of moisture in the soil for plants, control soil erosion and improve the availability of nutrients for plants. But direct Effects of microorganisms on plant growth include the secretion of plant growth-promoting hormones such as auxins that stimulate plant growth,” says Mr. Dadzie.
Not only are dry areas valuable as food containers for large numbers of people, they also provide other services, Mr. Dadzie says. “Due to the vastness of arid regions, they have the greatest potential to sequester carbon in the atmosphere and thereby contribute substantially to climate change.”
While this study was conducted in a field, the seedlings were given both shade and water. Going forward, the authors say similar experiments should repeat the methodology, but under more natural conditions — with environmentally determined sun and rain.
Seed microorganisms dominate soil microorganisms when colonizing plants
Quote: Local bacteria help native seeds take root in arid landscapes (2022, October 20) retrieved October 20, 2022 from https://phys.org/news/2022-10-local-bacteria-native-seeds-root.html
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