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Quantification of carbon in Bukit Timah nature reserve, Singapore
Author
Ngo, Kang Min
Supervisor
Lum, Shawn K. Y.
Abstract
Quantifying carbon stocks of forests is important for understanding the role played by forests in sequestering carbon and also for managing carbon budgets. Major carbon stocks of primary and secondary forests in Bukit Timah Nature Reserve (BTNR), Singapore, were compared. Data from tree measurements, soils and woody debris were collected and compared with forests from other sites. Carbon stocks in primary forests totaled 297 Mg ha-1, with 167 Mg ha-1 found in aboveground biomass (AGB). Stocks in secondary forests were lower at 226 Mg ha-1, with 105 Mg ha-1 found in AGB. Carbon in AGB was 1.5 times higher than soil C in primary forests, but they were of equal proportion in secondary forests. Secondary forests held only 24% less carbon than primary forests, but most of it was found in soil, with AGB making up most of the difference. Secondary forest had more soil C than primary forest. As the secondary forests mature, they will have the potential for a higher AGB. Both AGB and soil accounted for more than 90% of total carbon stocks in both forest types. Coarse woody debris made up 5.2% and 1.8% of total carbon in primary and secondary forests respectively.
AGB in the primary forests of BTNR was lower than other Asian moist tropical forests, but was within the mean for Neotropical forests. Soil C in BTNR was lower than in Neotropical forests. The difference in the ratio of carbon in AGB:soil between Asian and Neotropical forests may be due to geographical history and forest structure. Given this, the magnitude of the response of trees and soil to climate change may differ between forests, and global models for biomass change need to take this into account. The results show that primary forests store more carbon than secondary forests, but because secondary forest cover is higher, they are also important carbon stocks.
Change in carbon stocks in future will depend on tree growth rates. AGB in primary forest has decreased in the 15-year census period, with the greatest decrease in the 1997 El Niño drought. With more data being collected on smaller intervals, fine scale fluctuations in tree growth can be monitored. This data will also be useful in detecting short- term changes in tree growth due to rare weather events like drought or heavy rain. Secondary forests form the majority of forests in Singapore, and are important carbon stocks. However, secondary forests at different stages of recovery can have large variations in carbon stocks. More work on the recovery rates and trajectories of secondary forests will help to narrow carbon estimates in these forests. Urban trees in Singapore are also important because of their sheer number found on streets. Many of them grow to large sizes, so their carbon sink potential is great given that street trees will always be present. Better understanding of carbon accumulation in street trees will allow improved management of tree planting for carbon storage purposes, in addition to aesthetics. Future work can be done on secondary forests in other areas and on urban trees to provide a more comprehensive of carbon stocks in the country.
AGB in the primary forests of BTNR was lower than other Asian moist tropical forests, but was within the mean for Neotropical forests. Soil C in BTNR was lower than in Neotropical forests. The difference in the ratio of carbon in AGB:soil between Asian and Neotropical forests may be due to geographical history and forest structure. Given this, the magnitude of the response of trees and soil to climate change may differ between forests, and global models for biomass change need to take this into account. The results show that primary forests store more carbon than secondary forests, but because secondary forest cover is higher, they are also important carbon stocks.
Change in carbon stocks in future will depend on tree growth rates. AGB in primary forest has decreased in the 15-year census period, with the greatest decrease in the 1997 El Niño drought. With more data being collected on smaller intervals, fine scale fluctuations in tree growth can be monitored. This data will also be useful in detecting short- term changes in tree growth due to rare weather events like drought or heavy rain. Secondary forests form the majority of forests in Singapore, and are important carbon stocks. However, secondary forests at different stages of recovery can have large variations in carbon stocks. More work on the recovery rates and trajectories of secondary forests will help to narrow carbon estimates in these forests. Urban trees in Singapore are also important because of their sheer number found on streets. Many of them grow to large sizes, so their carbon sink potential is great given that street trees will always be present. Better understanding of carbon accumulation in street trees will allow improved management of tree planting for carbon storage purposes, in addition to aesthetics. Future work can be done on secondary forests in other areas and on urban trees to provide a more comprehensive of carbon stocks in the country.
Date Issued
2013
Call Number
QH77.S55 Ngo
Date Submitted
2013