Photosynthetic Responses of Invasive Acacia mangium and Co-Existing Native Heath Forest Species to Elevated Temperature and CO₂ Concentrations

ABSTRACT

The impacts of climate change, in particular via elevated temperature and atmospheric CO₂ concentrations, cause differential photosynthetic responses between native and invasive alien plants, often resulting in varying magnitudes of plant growth and productivity. This study investigated variations in photosynthetic responses of an invasive alien Acacia species and two successional groups of tropical heath forest species: early secondary (Buchanania arborescens and Dillenia suffruticosa) and secondary (Calophyllum inophyllum and Ploiarium alternifolium) groups at elevated temperature (25 to 30°C) and CO₂ levels (400 to 700 ppm). Invasive A. mangium appears better adapted to higher temperature and CO₂. High temperature improved CO₂ assimilation of A. mangium compared to heath species, which was attributed to increased transpiration rate and stomatal conductance but decreased water-use efficiency. Photosynthetic responses showed no differences in early secondary species at elevated temperature and CO₂ but invasive A. mangium and P. alternifolium were stimulated by elevated CO₂. The greater maximum net photosynthesis of A. mangium coincided with lower light compensation point and electron transport rate for RuBP regeneration, to a certain extent. Findings provide insights into possible underlying ecophysiological mechanisms contributing to the invasion success of Acacias in degraded tropical heath forests in response to future climate change.

KEYWORDS:

• Acacia
• Borneo
• climate change
• CO₂ response curves
• Kerangas forest
• light response curves
• photosynthesis

Data deposition

Data on leaf gas exchange and biochemical parameters of photosynthesis of invasive Acacia mangium and tropical heath forest species are available at Dryad Digital Repository (https://doi.org/10.5061/dryad.d51c5b00d).

Acknowledgments

We thank Muhammad Najib, Salwana Md. Jaafar, Nurul Naqibah Rosli, Shamira A. Matali, Wang H Chak and Shaahidah Marjik for their assistance with field and lab work. We are grateful to the Brunei Darussalam Meteorological Department, Ministry of Transport and Infocommunications for weather data and the Forestry Department, Ministry of Primary Resources and Tourism, Brunei Darussalam for entry and collection permits ([99]/JPH/UDN/17 PT.1). We thank anonymous reviewers for their constructive comments on earlier and revised versions of the manuscript. The authors have no conflicts of interest to declare.

Additional information

Funding

This work was funded by the Brunei Research Council [UBD/BRC/11]; the UBD research grant [UBD/PNC2/2/RG/1(204)]; and the Universiti Brunei Darussalam (UBD) Graduate Research Scholarship to MHI.