Productivity and profitability potential for non-native Eucalyptus plantings in the southern USA
Renewed interest in non-native Eucalyptus species for planting in the southern US has been spurred by projections suggesting they are more productive than the widely cultured Pinus species, by warming temperatures, and by attempts to identify frost-tolerant species as well as developing genetically modified Eucalyptus for frost tolerance. In addition to questions of environmental suitability, the economic viability of Eucalyptus is a significant hurdle to widespread adoption for commercial plantings. We sought to assess the potential obtainable yields and economic feasibility of Eucalyptus grandis Hill ex. Maiden and E. benthamii Maiden et Cambage, two species suitable for the southern United States. Using the process-based growth model 3PG, we projected potential yields at the sub-county level for E. grandis in Florida where it is operationally grown and E. benthamii in USDA Plant Hardiness Zones 8a and 8b where it has shown tolerance to occasional low temperatures. The 3PG model estimated mean annual volume increment, inside bark (MAI) that was used to estimate land expectation value (LEV) and internal rate of return (IRR). The MAI of E. grandis ranged from 18 to 119m3 ha−1year−1 (9 to 59.5 dry Mg ha−1 year−1) with a mean of 42.6m3 ha−1year−1 (20.8 dry Mg ha−1 year−1) for sites in peninsular Florida. The lower growth projections came from north Florida areas where annual frosts occur. Excluding urban areas, the LEV of E. grandis ranged from $-1264 to $1710 ha−1 with a mean of $424 ha−1. The estimated IRR ranged from −9.7% to 16.9% with a mean of 8.2%. Eucalyptus benthamii MAI ranged from 3.3 to 76 m3 ha−1year−1 (1.8 to 41.8 Mg ha−1year−1), with a mean of 21.9m3 ha−1year−1 (11.9 Mg ha−1year−1). The higher yields were primarily located in coastal regions of USDA Plant Hardiness Zone 8b. Excluding urban areas, LEV ranged from $-2707 ha−1 to $1532 ha−1. The maximum estimated IRR was 15.9%. Our results show that Eucalyptus is potentially profitable as a bioenergy crop in the southern USA, but potential profitability of E. benthamii was limited by low temperature; positive LEV was obtained where productivity was 30m3 ha−1year−1 or more. Profitability was restricted to a small percentage (12%) of sites theoretically within the operational range in the southern U.S. indicating that a wholesale conversion of Pinus taeda plantations is unlikely.