Comparing benefits of tree planting vs natural colonization for future resilience of UK woodlands

In a new study published in the journal Evolutionary applicationsScientists from royal botanical gardens, Kew and forestry research have a detailed analysis of genetic diversity and the health of comparative trees for young British woods, revealing the advantages and disadvantages of planting compared to natural colonization.

This is the first research publication of the Center for Forest Protection, a joint venture between RBG Kew and Forest Research. The CFP brings together the expertise of the United Kingdom and the rest of the world in the joint creation of knowledge and research to protect and improve the future health and resilience of our forests, woods and trees.

While England seeks to stop the decline of nature and reach the coverage of the canopy of 16.5% in England by 2050, political decision -makers want to know if natural colonization or the planting of trees is the way to follow. Having strong and healthy forests is a particularly salient problem in the wake of the wasting of ashes, which has destroyed millions of trees across the country in the last decade.

Dr. Guillermo Friis, postdoctoral researcher in health and adaptation of plants at RBG Kew and the first author of the article, says: “Through the country, trees of the same species have slight genetic differences that have evolved to help them develop better in these places.

Kew and forest researchers have examined sites with natural and planted English oak and silver birch colonizations to compare the conditions of young trees and assess small differences in DNA between tree populations. Genetic diversity is crucial if the Forests of the United Kingdom must prosper, because although many trees will undoubtedly fail, some will have resilience integrated into pathogens and stress factors such as drought that can be transmitted to future generations.

The good news is that planting and natural colonization can create a healthy and diversified forest when analyzed at the local level, strengthening recent results in a Surrey forest where natural selection evolved resilience to the decline of ashes.

However, natural colonization is not a solution to the problem, due to the small and fragmented nature of the woods of the United Kingdom. Scientists have found that many young trees are very closely linked, which covers the risk of consanguinity and the drawbacks associated with this.

Dr. Friis says: “A remarkable conclusion of our study was that the consanguinity – the loss of genetic diversity that occurs when closely related individuals reproduce – was twice as high in young forests naturally colonized compared to planted people. This is probably due to the lack of connectivity between forest plots, often isolated by large areas of the farm.

Likewise, planted sites seemed more similar than scientists expected, when seen nationally. For example, the genetic variation between the sites was five times higher between the populations of naturally colonized than the populations planted in oak, probably due to seeds from few stands. More diverse seeds were used in birch plantation, which has helped maintain population differences.

In a distinct part of the study, the researchers found that planted trees too often come from a handful of seeds of seeds. This contributes to the lack of variability between planted woods.

A proposal which will be presented to the government and the sector of the supply of seeds and the nursery consists in prioritizing the collection of seeds from a wider range of healthy parent trees of the regions through regions to balance genetic diversity and local adaptation during the propagation of plants for planting, an approach launched by the national seed of Kew trees.

Dr. James Borrell, leader in health research and adaptation of plants at RBG Kew, said: “Working in close collaboration with trees has shown that scientists and industry are really on the same wavelength. We need more diverse sources of seed to maximize the resilience of our future forests. If the seeds come from the same number of stands, could erode the genetic diversity of our native trees. “

Dr. Nadia Barsoum, senior forest environmentalist at Forest Research, said: “Although overall, we found the health of young birch and oaks evaluated as good, we found higher incidents of leaf pathogens on the causes of planted birch compared to the trend trend, but a monitoring monitoring project (but a monitoring project. is based on this research.

Climatic forecasts for the United Kingdom suggest that trees planted today will face drier and two, three or even four warmer conditions, without even taking into account the increased risks of pests and diseases. Securing healthy forests for the future will most likely require a holistic approach to the planting of targeted trees with mixed natural colonization.

Dr. Friis says: “To move forward, it is not only the number of trees we plant, but to make sure that those we plant are equipped to prosper in today’s environment and that their offspring can keep the rhythm of the environmental challenges of the future.”

Dr. Barsoum says: “Our results suggest that, for the United Kingdom, a hybrid approach to increase wood coverage – using both natural colonization and planting of trees using various seed sources – could be the most effective strategy for forest culture which could have greater resilience to pests, diseases and climate change.”