The Ridgefield Tree Experiment is a long-term study of ecological restoration in which trees and shrubs have been planted in various combinations to examine how these different combinations perform a variety of services, including carbon sequestration, in the face of ongoing environmental change.
Initiated in 2010 by Australian Laureate Fellow and Professor Richard Hobbs, the project is located in the Wheatbelt region of South-Western Australia, where researchers were allocated 21 hectares of land that had previously been grazed or cropped. This parcel of land was fenced (rabbit-proof) and 124 experimental plots were ripped, weed sprayed and planted with combinations of 8 species of native vegetation along 11 rip-lines within each 23m long plot.
The species used were Eucalyptus loxophleba, Eucalyptus astringens, Acacia acuminata, Acacia microbotrya, Banksia sessilis, Hakea lissocarpha, Calothamnus quadrifidus and Callistemon phoeniceus. These were planted in ten different combinations in each of the 10 blocks, categorised according to soil type, moisture and aspect.
Ridgefield’s unique contribution is to simultaneously investigate trade-offs among services, environmental change impacts, and the contribution of novel components of the flora to the provision of multiple ecosystem services. It seeks to answer pertinent ecological questions, such as whether the restoration of former agricultural land can achieve multiple outcomes, including carbon sequestration, soil erosion control, biotic resistance, nutrient cycling, pollination and biodiversity.
As a long-term study, the project will also help address what Professor Hobbs sees as one of the great ecological challenges of our time: how to set and achieve realistic restoration goals within a rapidly changing world.
This is one of the biggest such experiments in Australia, and it links into a growing worldwide network of experiments exploring the way that ecosystem diversity affects function. It is likely that these projects will increase in number and in scale as different ecosystem services become increasingly valued by humanity.