Predicting tree growth at specific sites and for general regions in Southeast Asia

• Royal Forest Department, Thailand
• Research Institute of Forestry, China

For many years, the ACIAR Forestry program has given high priority to the evaluation and domestication of Australian trees and shrubs with potential to meet the diverse needs of forestry and agroforestry in developing countries. However, while the introduction and testing of a wide range of new species with potential for use in reforestation has benefited both developing country partners and Australia, the program has been slowed by not always knowing where a particular species or provenance is likely to grow and how well it is likely to grow there. The barriers have been a lack of readily accessible soil and climate data across each country and the means to interpret these data quickly.
In the course of an earlier ACIAR project (8808), microcomputer-based climatic and simulation mapping programs were developed for Africa using interpolation analyses, which allowed climatic conditions to be estimated reliably for locations some distance from meteorological stations. While this proved useful for defining trees' climatic requirements, predicting how well trees would grow in different environments proved more difficult. It became obvious during the African project that soil information was necessary, and this was subsequently included in the promising GROMAP simulation mapping program. More work is needed to develop and test this program in Australia and overseas.
In the current project, the programs developed for Africa will be modified to run with data from China and Thailand. (Prototype climatic mapping and simulation mapping programs have already been developed for Australia.) 'Climatic mapping' programs will help indicate regions where particular provenances can grow; and 'simulation mapping' programs will predict how well particular trees will grow in different parts of each country. The programs will allow evaluation of conditions in hundreds of locations, and generate maps indicating regions suitable for particular provenances. Interpolation analyses will provide the necessary climatic data, and digitised soil data will be extracted from maps.
Data on the climatic, soil and topographical environments will be correlated with the growth of selected provenances of at least six different Australian tree species (including Eucalyptus camaldulensis, Acacia mangium and Acacia auriculiformis) from trials in China, Thailand and Australia. These will be used to determine limitations to the growth of each provenance.
A major part of the program development and testing will take place in Australia at the CSIRO Division of Forestry, which has both expertise on land evaluation for forestry and experience obtained from participation in many previous ACIAR projects. The project leader will visit both collaborating countries regularly, and in the third year his visit will be timed to include a final project workshop in Bangkok. The Centre for Resource and Environmental Studies, Australian National University, will carry out the interpolation analysis of climatic data; and CSIRO Division of Soils will provide soil data for Australia, and advice on its interpretation and inclusion into mapping programs.
Chinese and Thai scientists will collate results from trials involving provenances of the target species in their own countries and assemble tree growth and climatic data. They will make detailed measurements of soil conditions at each site. A considerable amount of climatic data for China has already been gathered, but additional information for solar radiation and evaporation will be required. The collation of climatic data for Thailand will be a major task. The climatic and simulation mapping programs will be tested in both countries, and results evaluated by local experts. The two main collaborators from China and Thailand will visit Australia for training and collaborative research sessions.
The problem of predicting where and how well different trees will grow is fundamental to forestry, and global in extent, so the methods used in this project are expected to have a high spillover effect. Making an appropriate tree selection can double or triple yields for virtually no additional establishment cost. The information generated will be particularly useful to seed centres and decision makers who are selecting trees for trials in different regions.
The work will greatly strengthen the research being done in China and Thailand by providing access to the latest facilities and methods; and Australia will learn more about the ability of its native plants to adapt to different conditions.