Trees may work together to form resource-sharing networks with root grafts

by University of Glasgow

A length of steel pipe and a heart monitor are the unlikely tools underpinning new research which suggests that trees may work together to form resource-sharing networks, helping the group collectively overcome environmental challenges.

The findings, laid out in a paper published today in Communications Biology, offer fresh insight into how forests around the world might adapt to the increasing environmental stresses of climate change.

Researchers from universities in the UK, Germany, France and Mexico partnered on the project, which investigated how mangrove trees form networks of root grafts in a Mexican coastal lagoon.

Root grafts are physical connections between tree roots which can allow them to exchange water, carbon and mineral nutrients. Trees with less access to sunlight have been shown in previous studies to survive by sharing resources supplied from root grafts with better positioned neighboring trees. Very little research has been conducted into resource-sharing in more extensive networks, however, because mapping root grafts between trees requires costly, time-consuming and difficult excavation work.

The research team set out to gain a broader understanding of how root grafts are formed in larger networks of trees in resource-challenged environments. To do so, they studied black mangrove trees, a coastal species which plants shallow roots in soft underwater sediments, in the La Mancha lagoon, in the Veracruz region of Mexico.

For most of the year, the lagoon is separated from the salty waters of the Gulf of Mexico by a sandbar which closes off a narrow inlet between the two bodies of water. However, during spring, fresh water runoff eventually overcomes the sandbar, bursting it open within one day and seawater from the Gulf floods into the lagoon. The Gulf waters add salt to the freshwater lagoon, doubling or sometimes even tripling the salinity of the sediments during the dry season—lasting several months each year-.

The shifting cycle of salinity makes it more difficult for the mangrove trees to consistently draw water and nutrients they need to survive from the earth. The researchers hypothesized that this salt stress could spur mangrove trees into forming root grafts across groups of trees, known as stands. Active root grafts could allow stands to spread resources across a network of separate trees to help keep each one alive, but even non-functional grafts could help to make the group more stable against tides and high winds, providing a yet uncalculated contribution to forest resilience when it comes down to coastal protection services.

> Source: PHYS.ORG