Oak trees can live for hundreds of years, but climate change causes drought, poor soil, and disease to occur at a much faster rate. Scientists now think that tiny microorganisms that live on and inside oak trees may help protect them from such stresses.

Recent forest research focused on the sessile oak, Quercus petraea. The results showed that microbial communities associated with leaves, stems, and roots are surprisingly stable even under harsh environments. pressure.

Microorganisms that live in oak trees

All oak supports millions of bacteria and fungi. Each part of the plant has its own group. Different microorganisms are present in the leaves, inner bark, roots and surrounding soil. community.

Most bacteria in leaves belong to a group called Proteobacteria. The stems contain a mixture of Proteobacteria and Actinobacteria. Roots show a different pattern. Actinobacteria predominate in the root zone.

Fungi also vary by tissue. The leaves and stems mainly contain ascomycetes. The root zone contains more basidiomycetes. Many fungi in the root zone form ectomycorrhizal partnerships that help trees absorb nutrients and water from the soil.

Specific bacterial families may play important roles. Beijerinchiaceae often occurs on leaves and stems. Members of that group can fix nitrogen, which may support leaf growth and metabolism.

In the root zone, Acidothermaceae thrives in acidic soils and helps break down organic matter. Since oak roots often grow in acidic conditions, such microorganisms could improve nutrient cycling.

Test by stressing trees

Researchers studied 144 oak trees growing in forests in Norfolk, England. Each tree was approximately 35 to 40 years old. Scientists created stressful situations in three ways.

Rain shelters reduced soil moisture and simulated drought. Ring barking disrupted nutrient transport by shedding thin strips of bark. bacteria Also, beetle larvae associated with the rapid decline of oaks have been added to some trees.

Soil moisture surveys confirmed the effects of severe drought. There was a time when the soil water under the rain shelter was reduced to more than half. Humidity in the stems also decreased, indicating real physiological stress.

Despite these physical changes, the microbial community remained largely stable.

Why stability is important

Old trees are often stable microbiome. Long-lived plants are likely to develop strong partnerships over time. The study found that microbial diversity did not change much after drought or chirping.

Even in trees showing early symptoms of acute oak decline, no significant microbiome disruption was seen in healthy tissue.

“As environmental stressors increase, one of the key adaptations that trees have is their microbiome,” said James McDonald, senior author of the study. University of Birmingham.

“A better mechanistic understanding of how host-microbe interactions help trees move and survive drought may open opportunities to improve tolerance, for example by inoculating trees with beneficial microbes.”

“Climate change is happening very rapidly, but trees are long-lived sessile organisms that take a long time to adapt to change, and many of our trees are ill-equipped,” added Sandra Denman. forest researchBritish Forestry Commission.

Drought changes root microbes

Although most microbial communities remained stable, long-term drought caused subtle changes in the roots. After long periods of rainfall exclusion, actinobacteria increased in the root zone.

Actinomycetes often occur in dry soils. Members of that group have thick cell walls and can form spores. Such properties help them survive in harsh conditions. Research on crops has linked the group to drought tolerance.

Other bacterial groups, including Acidobacteriota, also increased in the root zone during drought. Some members produce a sticky substance that helps the soil retain water and stay attached to the roots.

At the genus level, the drought-enriched bacteria are: nocardia, actinomycetes, Acidothermusand acidocera.

Many exhibit properties that promote plant growth. Some break down nutrients. Some produce hormones such as indole-3-acetic acid, which support root growth.

Fungi respond to drought

Fungal partners have also changed. Penicillium and aureobasidium Increases in roots affected by drought. Both groups include species known to support plant growth.

“Despite the trees showing physiological changes and the soil becoming considerably drier, its microbiota remained very stable,” said Usman Hussain, lead author of the study. bangor university University of the West of England (UWE).

“This highlights the potential role of oak-associated microbial communities in maintaining forest ecosystem stability.”

Oak stem microorganisms under stress

The microorganisms on the stems responded more than those on the leaves. Under drought and soil stripping, certain fungal genera associated with rot and disease increased. At the same time, some beneficial endoparasitic bacteria were also reduced.

Such a pattern suggests that long-term stress may weaken the internal defenses of woody tissues. However, the overall structure of the microorganism did not collapse.

Semi-mature oak trees have a complex tissue-specific microbial network that can withstand significant disruption. Long-term exposure to drought resulted in small but meaningful changes, especially in the root zone.

Future research will explore the molecular signals that guide the recruitment of beneficial microorganisms. Scientists also plan to compare trees of different ages and locations.

Forests store carbon and support biodiversity. Stable microbial partners could help oak trees withstand climate stress and continue to play an important role in the ecosystem for decades to come.

The research will be published in a journal Cell hosts and microorganisms.

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