Water Stewardship Information Sources
| Citation | Jassal, R.S., T.A. Black, T. Cai, K. Morgenstern, Z. Li, D. Gaumont-Guay and Z. Nesic. 2007. Components of ecosystem respiration and an estimate of net primary productivity of an intermediate-age Douglas-fir stand. Agricultural and Forest Meteorology, 144: 44-57. |
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| Organization | UBC |
| URL | http://www.sciencedirect.com/science/article/pii/S0168192307000366 |
| Abstract/Description or Keywords | Continuous half-hourly chamber-measured belowground (Rs) and eddy covariance (EC)-measured total ecosystem (Re) respiration in a 56-year-old Pacific west coast Douglas-fir stand from 2003 to 2005 were analyzed to study their seasonal and interannual variability. Seasonal variation in both Rs and Re was better predicted by soil temperature at the 5 cm depth than at any other depth and air temperature. Re was more responsive than Rs to changes in temperature and soil water content. While nighttime (Rsn) and daytime (Rsd) soil respiration showed no difference in their response to soil temperature, daytime ecosystem respiration (Red) was less responsive than its nighttime counterpart (Ren) to changes in soil temperature. Half-hourly Red was almost always smaller than Ren possibly due to photoinhibition while daily total Red was higher than daily total Ren during summer and spring months but smaller in winter and autumn months with the latter due to fewer daylight hours. A distinct seasonal pattern in the Rs to Re ratio was observed. The 3-year mean seasonal Rs/Re was at its minimum of 0.52 in spring followed by 0.63 in summer, 0.81 in autumn and a maximum of 0.86 in winter. Both daily total and half-hourly Rsd/Red were larger than Rsn/Ren. It appears that the different responses of Rs and Re to environmental variables arise as a result of seasonal variations in photosynthesis, mobilization and use of stored carbohydrates, and differences in the phenology of aboveground and belowground plant tissues. On an annual basis, Rs accounted for 62% of Re with the latter accounting for 86% of the carbon (C) assimilated in annual photosynthesis or gross primary productivity (GPP), leaving the net C sequestration efficiency (1 − Re/GPP) at 14%. In the relatively dry year of 2003, both Rs and Re as well as GPP were the lowest but with the highest net ecosystem productivity (NEP) of the 3 years. The relatively wetter growing season soil moisture regime in 2005 resulted in the highest Re and GPP. Partitioning of Rs into its autotrophic and heterotrophic components indicated that 54% of GPP was respired back to the atmosphere as autotrophic respiration and an additional 32% was lost in the decomposition of litterfall and soil organic matter. The mean annual estimate of net primary productivity (NPP) at 843 g C m−2 accounted for 47% of the mean annual GPP of 1815 g C m−2. Keywords Ecosystem respiration; Soil respiration; Heterotrophic respiration; Net primary productivity; Gross primary productivity; Carbon sequestration |
| Information Type | article |
| Regional Watershed | Vancouver Island North |
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| Comments | |
| Project status | ongoing |
| Contact Name | Andrew Black |
| Contact Email | [email protected] |