Journal of Environmental Biology

Growth responses of light demanding and shade tolerant peat swamp forest saplings to elevated CO₂

M.N.L. Wahidah^1,4, M.S. Nizam^1,3, C.M.Z. Che Radziah¹ and W.A. Wan Juliana²* 

¹Department of Biological Sciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, 43600, Malaysia

²Department of Earth Sciences and Environment, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, 43600, Malaysia

³Institute of Climate Change, Universiti Kebangsaan Malaysia, Bangi, 43600, Malaysia

⁴School of Biology, Faculty of Applied Sciences, Universiti Teknologi MARA Pahang, Jengka, 26400, Malaysia

*Corresponding Author Email : ayie@ukm.edu.my

Received: 14.11.2020                                                                   Revised: 17.03.2021                                                         Accepted: 26.03.2021

Abstract

Aim: To determine the growth responses of two peat swamp forest species, Shorea platycarpa, a shade-tolerant slow-growing species and Macaranga pruinosa, a light-demanding fast-growing species under elevated atmospheric CO₂ concentration.

Methodology: The saplings of both species were grown in a shade house at ambient (400±50 µmol mol^-1) and in an open roof ventilation greenhouse at elevated atmospheric CO₂ concentration 800±50 µmol mol^-1 for seven months. The temperature in both environments ranged between 25-33^°C with 55–60% sunlight transmittance and the saplings were thoroughly watered twice a day. Plants growth measurements were estimated at frequent intervals. Saplings biomass characteristics were examined using destructive methods after seven months of treatment and non-destructive method was used for determination of leaf area.

Results: Elevated CO₂ enhanced all the growth characteristics in M. pruinosa with a significant increase was observed particularly on both height and diameter relative growth rate and biomass characteristics. The height relative growth rate and leaf area were significantly reduced under elevated CO₂ in S. platycarpa but did not affect the shoot or root diameter and biomass significantly. A positive correlation (r =0.77, p>0.05) between stem biomass and basal diameter for plants under elevated CO2 was recorded for M. pruinosa, but not in S. platycarpa. Both species showed negative correlation (S. platycarpa; r = -0.53, M. pruinosa; r = -0.46, p>0.05) between stem growth and stem biomass at elevated CO₂.      

Interpretation: These results unveiled profound effects of elevated CO₂ on the growth of light-demanding species M. pruinosa, while shade-tolerant species S. platycarpa was not relatively affected by elevated CO₂. This underscored the necessity to analyse different species performance to elevated CO₂, thereby improving the ability to predict tropical swamp forest ecosystem responses to rising CO₂.      

Key words: Carbon-di-oxide, Growth responses, Macaranga pruinosa, Peat swamp species, Shorea platycarpa

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