2007 Fiscal Year Final Research Report Summary
Inter-relationships between Forest stand structure and nitrogen dynamics in Siberian taiga
| Project/Area Number |
16405010
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 海外学術 |
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| Research Field |
Ecology/Environment
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| Research Institution | Kyoto University (2006-2007)
Ryukoku University (2004-2005) |
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Principal Investigator |
OSAWA Akira Kyoto University, Grad. Sch. Agriculture, Professor (90288647)
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| Co-Investigator(Kenkyū-buntansha) |
KAJIMOTO Takuya Kyoto University, Forestry & For Prod. Res. Inst, Senior Researcher (70353638)
MATSUURA Yojiro Kyoto University, Forestry & For Prod. Res. Inst, Senior Researcher (20353857)
TOKUCHI Naoko Kyoto University, Field Science Ed. & Research Center, Associate Prof (60237071)
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| Project Period (FY) |
2004 – 2007
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| Keywords | Larix gmelinii / Russia / Siberia / permafrost / forest ecosystem / biomass / fertilization / nitrogen dynamics |
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| Research Abstract |
Biomass increases gradually in a predictable pattern with decrease in stand density in general plant populatioins when growing in relatively dense condition. This quantitative relationship is called the "Self-thinning rule." However, data analysis from larch stands of Siberia that grow on permafrost show that decrease in stand density is associated with leveling-off of aboveground biomass at constant values, which is against the "common sense" in ecology. We consider that the permafrost limits the depth of frozen soil that can be thawed in the summer, leading to limitation of sail nutrients, thus limiting the value of the attainable aboveground biomass. We termed this phenomenon "the biomass limitation hypothesis." This research investigated the changes in nitrogen dynamics and that in forest structure and function that are associated with a controlled fertilization experiment in larch forests with nitrogen fertilizers.
We confirmed that the larch forests on permafrost are ecosystems where the patterns of nitrogen dynamics are rather difficult to described accurately. The general levels of nitrogen mineralization are very small, and their spatial variation was very large. Also immobilization of mineralized nitrogen was suggested to have occurred due to uptake of mineralized nitrogen by soil micro-organisms. Four seasons of nitrogen fertilization showed increase in nitrogen concentration of some forest floor plants ; however, the structure of larch forests was unchanged. It was strongly indicated that nitrogen is a limiting nutrient element for tree growth in this forest. Results of the present investigation were published in proceedings of international conferences and in scientific journals. Additional papers are also being published in the near future. Findings of the present research are being published as a monograph in the Ecological Studies Series of Springer-Verlag, a German publisher. Its manuscript is near-completion.
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