- Department of Civil & Environmental Engineering, National University of Singapore, Singapore (kavindra@nus.edu.sg)
Introduction
Soil respiration is an important part of the carbon cycle and is a significant terrestrial carbon source. There is currently very limited research focused on characterising soil respiration in Singapore, and even among studies conducted in Southeast Asia, most of the research focuses on primary forests rather than urbanized soils. The objectives of this study were to assess the variation of soil respiration with land use, characterise the daily cycles of soil respiration and identify the factors which drive soil respiration in an urban catchment.
Methods
Soil Respiration was measured at 7 forests sites and 12 urban park sites in Singapore, using a portable Li Cor Soil Respiration Smart Chamber. Soil samples were also collected from each of the sites and their nutrient concentrations were quantified. Additionally, at one park and one forest, the daily cycle of soil respiration was measured from 7 am to 7pm, where half hourly measurements were taken, along with corresponding measurements of soil temperature and moisture.
Results & Discussion
When comparing soil respiration rates between parks and forests, we found that, on average, respiration rates in the forests were slightly higher than those in the parks (Forests – 3.62, Parks – 3.46 umol CO2.m-2s-1) (Fig 1), but the difference was not statistically significant (Wilcox test p value > 0.05).
Next, the daily variation of soil respiration was characterised and our results revealed that the magnitude of variation in soil respiration throughout the day was small (Forest: 2.34-2.52, Park: 3.80-4.26 umol CO2/m2.s) (Fig 2). This lack of variation can be explained by relatively minor changes in soil temperature and moisture. Soil temperatures in Singapore did not vary much throughout the day (Forest: 26.2 – 28.00C, Park: 27.1 – 30.30C), and as previous research shows, more significant changes in temperature are required to see significant changes in soil respiration.
Finally, in order to determine what factors affected soil respiration, the relationship between soil nutrients and soil respiration was assessed. Results revealed that only NO3- was strongly positively correlated with soil respiration and a linear regression analysis revealed that soil nitrate concentrations explained about 50% of the variation of soil respiration (Adjusted R2 = 0.503, p<0.05). Other nutrients like phosphate, ammonium and dissolved organic carbon has no significant relationship with soil respiration.
Fig 1: Variation of Soil Respiration by Land use
Fig 2: Daily cycle of Soil respiration in a park and forest
In terms of future work, we also plan on conducting soil respiration measurements on managed land use types like agriculture and golf courses. Additionally, we plan on further characterising temporal variations of soil respiration, including diurnal and seasonal variations, across land use types. Finally, we will collect additional data on soil parameters like total organic carbon, microbial populations and community diversity and use these to develop models for soil respiration as well.
Acknowledgements
This research grant is funded by the Singapore National Research Foundation under its Competitive Funding for Water Research (CWR) initiative and administered by PUB, Singapore’s National Water Agency.
How to cite: Senaratna, K. Y. K., Te, S. H., Fatichi, S., and Gin, K. Y.-H.: Characterising Soil Respiration rates across different land uses in a Tropical Urban Catchment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13880, https://doi.org/10.5194/egusphere-egu25-13880, 2025.