Researchers demonstrate that tree diversity increases productivity and carbon storage, and strengthens the resilience of young, planted stands.
Long-term studies and a "global synthesis" of 21 experiments, which included research data on 83,000 trees at the University of Western Australia's (UWA) Ridgefield research farm, indicate that a combination of four to five tree species in a stand delivers the greatest productivity and stability. Climate change is helping the spruce bark beetle spread further north, causing unprecedented outbreaks of pest damage that are effectively destroying boreal forests.
A broad international study confirms that mixed-species forestry improves stand productivity, increases carbon uptake and promotes forest resilience, offering practical measures for adapting land management to climate change.
The study, published in the journal Global Change Biology and led by Joel Jensen of the Smithsonian Environmental Research Centre (Smithsonian Environmental Research Centre), brings together the results of long-term field research. The 21 studies, carried out as a single unified experiment, were conducted in various countries around the world, including trials held in 2009 at the University of Western Australia's Ridgefield Pingelly farm. The co-authors are Michael Perring of the UWA Institute of Agriculture and the UK Centre for Ecology and Hydrology, Rachel Standish, an associate professor at UWA and professor at Murdoch University, as well as collaborators from America and Asia. The dataset covered growth measurements for more than 83,000 trees.
The analysis showed that both average productivity and growth stability increased along with tree species diversity. A combination of four to five species delivered the greatest gains in young plantings. Productivity was driven mainly by fast-growing, expansive species that performed well alongside slower-growing, conservative species able to adapt to competitive conditions.
"By combining contrasting resource-use strategies, forests with greater species diversity were not only more productive but also more stable," said M. Perring. "The fast-growing species boosted productivity, while the slower-growing species were able to coexist without significant disruption."
In the study the authors also identified functional diversity – the range of "techniques" species use to capture and use light, water and nutrients – as the main mechanism determining productivity. Structural differences, such as tree height and crown architecture, were smaller and more dependent on context.
"The results indicate that combining contrasting resource-use strategies improves forest productivity," explains Jensen. "It shows that mixed-species forestry can be a sustainable management approach with real benefits for climate resilience."
These conclusions were set out in a form suitable for use in forest planning and forestry policy-making. Including species combinations can increase carbon storage, improve resilience to stress factors such as drought and browsing pressure, and help meet sustainable forestry requirements.
The study provides an evidence-based framework for forest planting schemes that prioritise functional complementarity in order to establish new, productive and climate-resilient forest areas.
The University of Western Australia (UWA) is a publicly owned research university in Western Australia state, Australia. The university's main teaching campus is located in Crawley, a suburb in the local government area of Perth. UWA was founded in 1911 under a dedicated act of the Western Australian parliament. UWA is the oldest university in Western Australia and the sixth oldest in Australia. It is classified as one of the so-called sandstone universities, an informal title given to the oldest university in each state.
UWA is a member of the Group of Eight, which brings together the eight most research-active and most highly rated universities in Australia. The university recently attracted more competitive research funding than any other university in Western Australia. Each year it earns more than 71 million dollars from research. More than 117 million dollars is invested in scientific projects. Every year more than 300 doctoral students obtain a PhD at the University of Western Australia.
In 2013, at an event marking the centenary of the University of Western Australia, its chancellor Michael Chaney announced a long-term goal: by 2050 the university should be among the world's 50 best research universities.