Productivity of Eucalyptus pellita in Sumatra: Acacia mangium Legacy, Response to Phosphorus, and Site Variables for Guiding Management

Abstract

We report on experimental studies conducted in South Sumatra with interrelated objectives to (i) examine the trends in production covering 30 years, including three rotations of Acacia mangium followed by Eucalyptus pellita which replaced A. mangium for managing the widespread threat of diseases; (ii) understand the effects of inter-rotation slash and litter management applied to acacia (legacy effects) on E. pellita growth; (iii) assess the long term changes in the top soil layer arising from above; (iv) evaluate, through a network of experiments, across the landscape, the nature and extent of growth responses to additional phosphorus. This data was also used to explore some of the critical site and stand variables which determine the variations in productivity and responses to management. The current growth rates of E. pellita are lower than those achieved in A. mangium. The management-legacy effects by conserving site resources provides a sustainable base for the growth of E. pellita, but for further increase in productivity, additional management actions are necessary. Changes in soil pH, carbon, N and extractable P were relatively small after four rotations. Supply of P at planting gave wood volume gains at harvest, ranging from 16 to 66% across sites. The plinthite layer in the soil profile was related to productivity, with higher growth rates of E. pellita occurring when the plinthite was at deeper layers. There is much scope for increasing productivity per unit area in this landscape, and available knowledge can be synthesized into a package of best practices for application. Management should aim to improve the quality of inter-rotation management to ensure more than 90% survival, and fast growth rates during the first 2 years. We provide a framework for further research and for refining management to produce the much needed additional domestic wood supply for the local industry.

Growth Response to Weed Control and Fertilisation in Mid-Rotation Plantations of Eucalyptus pellita in South Sumatra, Indonesia

“…It has been well documented that the addition of P at planting time markedly improves the early growth of E. pellita and that the growth response is sustained towards the end of rotation, although the proportional response declines over time [3,4]. In contrast, we found that application of P at age 1 year (in addition to P fertiliser given at establishment) did not result in any further additional growth of E. pellita throughout the rotation.…”

“…The lack of response and decline in response to P fertiliser applied at 1 year after planting is influenced by high internal nutrient retranslocation rates for P (54.6-73.2%), N (24.9-33.0%), and K (40.2-49.0%), while there was minimal retranslocation of Ca and Mg [17]. External cycling through litter after canopy closure is also important, with litterfall of E. pellita at Sodong being measured at 8.7 ± 0.4 Mg ha −1 year −1 [4]. Litter decomposition of E. pellita in this environment was rapid, with 91.0% of leaves, 71.0% of twigs, and 71.2% of noncommercial stems (diameter < 5 cm) being completely decomposed within 18 months [18].…”

“…A. mangium had been the main species grown for pulp and paper for the previous two decades, but, in the third rotation, a fast-spreading canker-wilt disease caused by Ceratocystis fungi rendered A. mangium plantations no longer viable [1,2]. E. pellita has been found to be more resistant to Ceratocystis and is a good prospect for wood production, so it has become the species of choice in the region [3,4].…”

“…However, there is little information publicly available about the management of these plantations. In South Sumatra, the current growth rates of E. pellita are lower than that of A. mangium [3][4][5]. However, recent inventory data from operational plantings of E. pellita revealed that its productivity has improved due to better silviculture practices, including nutrient management and weed control [4].…”

“…In South Sumatra, the current growth rates of E. pellita are lower than that of A. mangium [3][4][5]. However, recent inventory data from operational plantings of E. pellita revealed that its productivity has improved due to better silviculture practices, including nutrient management and weed control [4]. It is likely that management practices need to be further refined to be able to achieve productivity levels similar to that of A. mangium.…”