Tạp chí
CARBON SINKS OF VIETNAM’S FORESTS AND CLIMATE CHANGE MITIGATION
Do Dinh Sam1*, Vu Tan Phuong2 and Ngo Dinh Que2
[1] Vietnam Society of Soil Science2 Vietnamese Academy of Forest Sciences
* Email: dodinhsam@gmail.com
SUMMARY
1. Forests play an essential role in the sequestration of CO2 through photosynthesis by plants. Vietnam’s tropical forests are rich in species and canopy layers, contributing to a high carbon sequestration ability. According to statistics in 2022, Vietnam has 14,790,075 hectares of forests, with 10,134,082 hectares of natural forests and 4,655,993 hectares of plantation forests. Therefore, calculating the carbon sequestration of forest ecosystems is necessary for the national emission reduction strategy.
2. The forest ecosystem has 5 carbon sinks: the above-ground sink (high trees, shrubs, and fresh vegetation); the under-ground sink (mainly live root system); dead wood sink in the forests (vines and large branches, trunks, roots); decay sink and soil carbon sink (within a 30 cm soil depth).
3. Forest carbon sequestrations in sinks are estimated by two methods: The direct method is the method based on survey data in standard plots and laboratory analysis, estimated for 5 carbon sinks, and the indirect method through factors, correlation equations, data on forest reserves…, usually determined with two carbon sinks (i.e., above- and below-ground sinks) and on a large scale as in a most ecological area.
4. The results of direct field determination show that the carbon sequestration of forest types in Central Highlands (i.e., 158.4 tC/ha of deciduous forests, 179.9 tC/ha of semi-evergreen forest, 244 to 282 tC/ha of rich evergreen broad-leaved forests, even up to 625 tC/ha) is much higher than other regions (170-200 tC/ha). The natural forests of Rhizophora apiculata in Ca Mau have a very high carbon sequestration capacity of 484 tC/ha.
Carbon sequestration in plantation forests widely varies depending on tree species, density, age, and soil class. The 30-year-old Pinus massoniana forests in soil class I is 179.4 tC/ha, Pinus merkusii forests is 148.8 tC/ha, which is almost equivalent to the deciduous forests in the Central Highlands, the 7-year-old Acacia hybrid forests is 108.6 tC/ha and Eucalyptus Urophylla forests is 95.6 tC/ha. Plantation forests of Rhizophora apiculata in Can Gio is 203 tC/ha.
Calculated results using factors are lower than estimated from direct studies because representative samples are widely different and often in two sinks. For example, the carbon sequestration of rich evergreen broad-leaved forests in the Central Highlands is estimated using factors varying from 166 to 183 tC/ha. If carbon sequestration in the soil is added, the value is similar.
5. The total carbon in decay and soil accounts for a small proportion compared with living biomass and total forest carbon, which follow a general rule in tropical forests. Compared to total forest carbon, soil carbon accounts for 30-35%, except for deciduous forests, 41%, which may be due to coal mixing because forests are always burning. Including decay, this rate is 35 – 38%. Mangroves in the Mekong Delta in many places present an increase in organic matter by soil depth, up to 120 cm, leading to a higher carbon in the soil than in the living biomass (proportion of 56.2%).
6. Forest carbon sinks are essential in mitigating climate change and participating in the global carbon trading market. Vietnam has planted forests under a Clean Development Mechanism and recently joined the REED+ with a program to reduce emissions from forests in 6 North Central provinces.
Keywords: Forest carbon sequestrations, carbon sinks.
Reviewer: Prof.Dr. Vo Quang Minh
Email: vqminh@ctu.edu.vn
Received: 03/3/2024
Review completed: 01/11/2024
Accepted: 07/11/2024
