Variation of Stem CO 2 Efflux and Estimation of Its Contribution to the Ecosystem Respiration in an Even-Aged Pure Rubber Plantation of Hainan Island

Bo Song, Zhixiang Wu (), Lu Dong, Chuan Yang and Siqi Yang
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Bo Song: College of Ecology and Environment, Hainan University, Haikou 570228, China
Zhixiang Wu: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
Lu Dong: College of Ecology and Environment, Hainan University, Haikou 570228, China
Chuan Yang: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
Siqi Yang: College of Ecology and Environment, Hainan University, Haikou 570228, China

Sustainability, 2023, vol. 15, issue 22, 1-15

Abstract: The stem CO 2 efflux ( Es ) plays an important role in the carbon balance in forest ecosystems. However, a majority of studies focus on ecosystem flux, and little is known about the contribution of stem respiration to ecosystem respiration (Reco) for rubber ( Hevea brasiliensis ) plantations. We used a portable CO 2 analyzer to monitor the rate of Es in situ at different heights (1.5 m, 3.0 m and 4.5 m) in an even-aged rubber plantation from 2019 to 2020. Our results showed that Es exhibited a significant seasonal difference with a minimum value in April and a maximum in September. The mean annual rate of Es at 3.0 m in height (1.65 ± 0.52 μmol·m −2 ·s −1 ) was slightly higher than Es at 4.5 m in height (1.56 ± 0.59 μmol·m −2 ·s −1 ) and Es at 1.5 m in height (1.51 ± 0.48 μmol·m −2 ·s −1 ). No obvious differences in vertical variations were found. An area-based method ( Ea ) and a volume-based method ( Ev ) were used to estimate stem respiration at stand levels. One-way ANOVA showed that Ea had no obvious differences in vertical variation ( p = 0.62), and Ev indicated differences in vertical variation ( p < 0.05). Therefore, the Ea chamber-based measurements at breast height were reasonable and practical extrapolation proxies of stem respiration in an even-aged rubber plantation. With the use of the area-based method, the stem carbon values released from a mature rubber forest were estimated to be 1.214 t C·hm −2 ·a −1 in 2019 and 1.414 t C·hm −2 ·a −1 in 2020. Ea /Reco and Ev /Reco showed seasonal changes, with a minimum value in April and a maximum value in December. The leaf area index (LAI) and soil volumetric moisture content (VWC) were the major impact factors of Ea /Reco in an even-aged pure rubber plantation.

Keywords: rubber tree; stem CO 2 efflux; leaf area index; ecosystems respiration; Hainan Island (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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