2006 Fiscal Year Final Research Report Summary
Soil Salinization due to forest disturbances in eastern Siberia and its effect on the carbon cycle.
| Project/Area Number |
17510018
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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 impact assessment/Environmental policy
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| Research Institution | Hokkaido University |
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Principal Investigator |
LOPEZ Larry Hokkaido Univ., Inst. of Low Temp. Sci., Postdoctoral Fellow, 低温科学研究所, 博士研究員 (20374712)
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| Co-Investigator(Kenkyū-buntansha) |
MACHIMURA Takashi Osaka Univ., Graduate School of Engineering, Asso. Prof., 大学院工学研究科, 助教授 (30190383)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Permafrost / Active Layer / Salt concentration / Carbon Dioxide / Forest Fires / Disturbance / Climate Change / Grassland. |
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| Research Abstract |
Forest canopy (larch and birch) indirectly prevent the active layer from deepening because of the cooling effect it imposes on soil temperatures. However, it is not only canopies that protect the active layer depth but, as it was found in this study, also wet areas within the grasslands with dense vegetation and high organic matter content.. High water content results in high ice content in the soil during winter which during spring requires more energy to thaw. During the short growing season of 100 days, in Central Yakutia, the active layer depth of this wet soil is similar to the active layer in the forest. The results of analyzing the profile of the active layer and upper permafrost showed that the active layer has a very low content of salts whereas this concentration increases linearly with depth. This is the main reason why the grasslands, known as alas, have not been reforested by the surrounding trees. Furthermore, it was found that birch acted as a buffer between forest and a
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las, representing the gradual increase in salt concentration in the soil of the larch forest, birch forest and grasslands. At present, the permafrost in Central Yakutia has a high content of salts and for that reason; few centimeters of permafrost degradation implies that large amounts of salts would be transported from the lower layers to the upper soil layers where the root zone distribute and thus impeding the growth of larch forests. Present global warming is increasing soil temperature to the point that in the coming years, due to water and salt movement, the landscape can change from forest to grassland. In this study, it was found that the absorption of CO2 in the forest is three times higher than the absorption capacity in the grassland and thus the change from forest to grassland will decrease the sink characteristics of this region by 75%. Moreover, evapotranspiration from the tree canopy and the understorey is evenly divided approximately between 50-50%. Therefore, a change in the landscape will have a strong effect on the overall water balance of this region bringing as a consequence the change in many other environmental processes taking place in this region.
Finally, fire in the forest, which is one of the major disturbances, has been playing a very important ecological role. After stand replacing fires, the active layer and permafrost recovers approximately 15 years later along with vegetation recovery aboveground. A change in fire return can have irreversible consequences in the sensible ecosystems of eastern Siberia. Less
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