Evidence-based global yield benchmarks in unthinned industrial plantation eucalypts

Abstract

There is increasing global demand for wood and wood products for a growing diversity of applications. Even-aged plantation forests are efficient in providing goods and services from relatively small areas of land. Eucalypt plantations have been an important component of wood supply worldwide and planted area expansion and productivity improvements have increased significantly over three decades, yet the opportunity may still exist for yield improvements per unit of land area. Increases in eucalypt productivity have resulted largely from an extensive network of field trials and studies published by researchers across the world and particularly in Brazil. This study collates eucalypt yield data primarily from studies of planting density and site factors, both as trials and as plantation sample plots. Studies selected for inclusion are those planted with successful genotypes and under conditions of standard silvicultural practice at the time. The final dataset comprises 309 records of eucalypt mean annual increment (MAI) at rotation age from 61 published sources across 129 locations in 18 countries worldwide. The MAI data are used to derive a benchmark eucalypt yield for high, moderate and low site quality in Kӧppen–Geiger climate zones across a stand density gradient from 200 to 2 500 trees ha⁻¹. The benchmark provides a comparison for plantation eucalypt growers to gauge their own productivity. A gap between benchmark and yield flags the opportunity for improvement and provides a focus for strategies to improve yield. Gap analysis can help foster co-operation, shared solutions and technology transfer across geographically separated growers sharing similar climatic conditions. Of particular significance is support for small-scale and medium-scale tree farmers who are becoming increasingly important in the supply chain. In places where expansion of a eucalypt plantation area is contemplated, it is envisaged that the yield benchmark will provide input to the cost benefit, risk analysis and sustainability planning considerations that are essential before planting starts.