2006 Fiscal Year Final Research Report Summary
Development of the method for measuring water vapor and carbon dioxide fluxes above forested complex terrain
| Project/Area Number |
17510011
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | KYUSHU UNIVERCITY |
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Principal Investigator |
KUMAGAI Tomo'omi Kyushu University, Faculty of Agriculture, Associate Professor, 農学研究院, 助教授 (50304770)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMIZU Takanori Kyushu University, Forestry and Forest Products Research Institute, Researcher, 九州支所, 研究員 (40353726)
OTSUKI Kyoichi Kyushu University, Faculty of Agriculture, Professor, 農学研究院, 教授 (80183763)
CHIWA Masaaki Kyushu University, Faculty of Agriculture, Research Associate, 農学研究院, 助手 (30380554)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Forest canopy / Transpiration / Sap flow measurement / Watershed / Carbon dioxide / Eddy flux |
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| Research Abstract |
To scale sap flux density (Fd) measurements of individual trees to stand level transpiration (E), the mean stand Fd (JS) is among the most important factors, because E is frequently estimated as a product of JS and stand sapwood area. Major uncertainties in JS estimations are caused by tree-to-tree and radial variations in Fd. Thus, by using the Monte Carlo sampling technique with original tree-to-tree Fd data measured at several depths, we examined how many trees and radial depths need to be sampled for calculation of appropriate JS. The results revealed that the potential error in JS with the largest available sample size was not stable even though radial profiles in Fd for all sample trees were measured. They also showed that to consider radial variation in Fd it might be necessary to sample at least six trees, but not necessarily more than this.
We conducted measurements of tree biometrics and tree-to-tree and radial variations in xylem sap flux density (Fd) in two different stand plots, an upper slope plot (UP) and lower slope plot (LP), during the growing season with significant variations in environmental factors. The manner in which the mean stand sap flux density (JS) and tree stem allometric relationship (diameter at breast height (DBH) versus sapwood area (AS_tree)) vary between the two stands along the slope of the watershed was then investigated. The results demonstrated that a unique or general function allowed description of the allometric relationship along the slope, but the data for its formulation needed to be obtained in both UP and LP. They also revealed that JS in UP and LP were almost the same during the study period despite differences in tree density and size between the two plots. This implies that JS measured in a partial stand within a watershed is a reasonable estimator of the values of other stands, and that stand sapwood area calculated by AS_tree is a strong determinant of water-use in a forest watershed.
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Research Products
(8 results)
