Forests are being planted in large numbers all over the world. Many of them are intended to remove CO2 from the air in order to reduce global warming. New research has shown that variation in the characteristics of trees plays a particularly important role in this.
International research published in Nature Ecology & Evolution has shown that in the long term, diversity plays a decisive role in CO2 absorption. In particular, species with different functional traits (the plant characteristics that determine growth, survival, adaptation and reproduction) together deliver higher productivity and absorption.
It had long been thought that a favourable average of these kinds of traits determined productivity in biomass and CO2 capture. And that is indeed the case in the first years after planting. But this changes after a few years, when the variation in traits becomes the primary driver of productivity.
“When we plant trees, it is better to do it properly and efficiently to ensure this contributes to meeting the climate goals we set,” lead author Dr. Franca Bongers explains. “And variation in traits in the planted trees plays a crucial role in this.”
Unique forest experiment
Franca Bongers, who received her doctorate at Wageningen, has been working for the past four years as a post-doctoral researcher at the Biodiversity and Ecosystem Functioning Experiment China (BEF-China), a collaborative project involving Chinese, German and Swiss researchers. In an area of 38 hectares in China’s Jiangxi province, more than 500 plots have been planted with various combinations of species of trees and shrubs. The development of the more than 200,000 trees has been tracked and monitored for ten years. This is the world’s largest and most comprehensive forest planting experiment, in which the effects of biodiversity are being studied at various levels: forest components, soil and microclimate, and interactions (between plants, plants and animals, and plants and fungi).
Variation is win-win
The outcomes underline the importance of short-term versus long-term goals in forestation. If you want to have well-developed vegetation within a few years, you plant species mainly with the same favourable growth and development traits. But if you want high productivity and carbon capture levels over a long period of time, you need to plant mixed forests with a spread of traits.
Co-author Professor Frans Bongers, tropical forest ecologist at Wageningen University & Research: “Within the current discussions on climate, biodiversity and ecosystem restoration, different types of new forest are important. Natural regrowth is relatively cheap and needs time to get started. Planting new trees is quicker in the first few years but is more expensive. So it is important to ensure that planting will contribute efficiently to your goals. In addition, variation attracts other diversity such as insects, birds, mammals and fungi. Variation is therefore a win-win!”
Apart from the fact that this publication plays an important role in drawing attention to the need to restore forest functions when planting new forests, it was also an opportunity for daughter Franca and father Frans to work together. Frans: “It was wonderful to be able to have a detailed discussion with my daughter on a subject we both find so interesting.” Franca adds: “Yes, it is lovely to be in contact with your father in a different way, and on something so fascinating. We also had the opportunity to go and see the BEF-China experiment for ourselves – it was wonderful and educational, going into the field together.”