The Ecological Society of Australia congratulates Mr Giancarlo Chiarenza on being awarded the 2021 Wiley Fundamental Ecology Award. Gian is a PhD candidate at the University of New South Wales, within the School of Biological, Earth and Environmental Sciences. He is investigating the role of plant-soil interactions in delayed greening.

Have you ever noticed how the expanding leaves of some plant species are shades of red, white, pink or purple? This phenomenon is called delayed greening and results from plants delaying chlorophyll deployment until the leaves are fully grown. As young leaves are not mechanically protected by toughness, they suffer substantially more herbivory than mature leaves. Therefore, delaying the input of chlorophyll may greatly reduce the loss of nutrients to herbivores.

“Although delayed greening might be an important part of a plants leaf deployment and carbon capture strategy, we have remarkably little quantitative evidence about its cross-species and biogeographic patterns,” said Gian.

“This project will improve our fundamental understanding of the biotic and abiotic factors that shape the strategies plants use in deploying their leaves, but also shed light on the role soil might have in shaping plant ecological strategies.”

Gian originally began his tertiary studies focused on geology but “a very grumpy but very lovely professor got me interested in plants.”

“This is the perfect project for me because I love soil and plant-soil relationships. I’m also colour blind so it’s funny, me studying the colour of leaves!”

Gian’s project will see him sample sites throughout New Zealand and the east coast of Australia, from Tasmania to Queensland. These samples will allow him to investigate three key hypotheses, including whether delayed greening is a continuous or binary state, whether it is confined to the tropics and the extent to which it is influenced by soil fertility.

Historically, it has been accepted that plants are subject to more intense herbivory in the tropics and that this might favour strategies that reduce losses to herbivory, such as delayed greening. This idea, combined with delayed greening being frequently observed in tropical plants and infrequently observed in plants in North America and Europe, led to delayed greening being thought of as a tropical phenomenon. However red expanding leaves can be seen in temperate Australia, such as on some Banksia and Eucalyptus species, suggesting that delayed greening is not limited to tropical plants.

It is also thought that the deployment of chlorophyll to young leaves depends on soil nutrients. This is based on the observation that delayed greening seems to be particularly common in tropical regions and Australia, both of which are renowned for their low-nutrient soils.

“If my sample points in New Zealand, which enjoys relatively highly fertile soils, show lower levels of delayed greening than the points in Australia with low fertility soils, that suggests that delayed greening is somehow related to soil nutrients,” said Gian.

“The theory is that if the soil has limited nutrients the plants won’t put them in young leaves that are very vulnerable.”

“The Wiley Fundamental Ecology Award will be an invaluable support to transform this project from financially impossible to doable, helping me unravel a question in ecology still unanswered after over a century,” said Gian.

“I want to raise awareness about how important soil is for plants because I see ecologists loving plant-insect interactions and plant-animal relationships in general; also, plant-climate interaction is a big thing. Sadly, soil is very little studied. There is almost nothing because usually people associate soil with agriculture.”

“If I can just get one person interested in how soils relate to plants it would be amazing.”