Growth and physiology of Hopea odorata planted within gaps in an acacia plantation acting as a nurse crop

Abstract

Background: Mixtures of tropical acacia nurse crops and understorey native species have been established to aid forest restoration in Vietnam, but with partial success. Knowledge of physiological mechanisms underlying competitive interactions remains limited.

Aims: To examine growth and physiological responses of Hopea odorata, a shade-tolerant dipterocarp, established within an Acacia hybrid (Acacia mangium × Acacia auriculiformis) nurse-crop plantation.

Methods: H. odorata seedlings were planted within three 22-m diameter gaps in a 3-year-old Acacia hybrid plantation in Central Vietnam. Growth and physiology responses to an environmental gradient in gaps were examined over 2 years.

Results: Growth rate and maximum rates of photosynthesis and stomatal conductance of H. odorata saplings increased significantly with increases in relative daily incident photosynthetically active radiation from 24% at the gap perimeter (GP) to 61% at the gap centre. Leaf N, P, and chlorophyll concentration were unaffected by position in the gap. At the end of dry season, there were significant reductions in leaf water potential for saplings close to the GP suggesting interspecific competition for water.

Conclusions: Despite naturally regenerating in shade, the strong ability of H. odorata to acclimate to high light environments suggests that its re-establishment on degraded sites, using Acacia hybrid as a nurse crop should be possible, provided that competition for light and water are managed.

Keywords:

• dipterocarp
• light response
• native species planting
• shade tolerance
• water competition

Acknowledgements

TLD, CB, and DCK conceived this study. TLD, DW, KC, and DCK carried out the field work. AE and DIF assisted with the analysis and interpretation of the results. TLD led the writing process with assistance from CB, AE, DIF, and RD. We thank the late Mr Nguyen Van Phan and Mr Nguyen Van Minh for their permission to use the acacia plantation for this experiment, Dr Jane Medhurst for helping in biomass data analyses, Mr Nguyen Huy Hoang and Mr Nguyen Xuan Giap of the Silviculture Research Institute for field assistance, and the anonymous reviewers for their helpful comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Australian Centre for International Agricultural Research (ACIAR) through a John Allwright Fellowship to the senior author and ACIAR Project FST/2006/087.

Notes on contributors

Tran Lam Dong

Tran Lam Dong is a silviculturist with interests in landscape restoration using planted native and exotic species.

Chris Beadle

Chris Beadle is a plant physiologist with interests in the effects of silviculture and environment on planted acacias and eucalypts.

Alieta Eyles

Alieta Eyles is a physiologist/pathologist with interests in whole-plant physiology and chemical ecology.

David I. Forrester

David I. Forrester is a silviculturist with interests in interactive effects in mixed-species plantations.

Richard Doyle

Richard Doyle is a soil scientist and academic supervisor of the senior author during this study.

Dale Worledge

Dale Worledge and Keith Churchill are senior technical staff with, respectively, expertise in the collection of light and gas-exchange data in the field.

Keith Churchill

Dale Worledge and Keith Churchill are senior technical staff with, respectively, expertise in the collection of light and gas-exchange data in the field.

Dao Cong Khanh

Dao Cong Khanh is an expert on the establishment of mixed-species plantations in Vietnam.