ESJ58 企画集会 T22-4

Delay of ecosystem response through nitrogen cycling in Siberian Taiga

*Popova A., Sugimoto A., Tei Sh. （Hokkaido Univ.）, Tokuchi, N. （Kyoto Univ.）, Maximov, T.C. （IBPC SB RAS）

Northern regions are known to be poor in nitrogen (N) which may limit plant growth. Therefore, it is important to know availability and allocation of N in ecosystem and labeling experiment with ¹⁵ N is useful tool to do this. We conducted observation on N cycle in boreal forest ecosystem in Eastern Siberia, where vast area is covered by the largest and the deepest permafrost in the world, and not so many studies on N cycle have been done.

The study site is Spasskaya Pad station, 40 km from Yakutsk city in Republic of Sakha, Russia, the main specie foming the forest stand is larch, which is deciduous conifer. Observed amounts of inorganic N available to plants occurred to be low comparing to it’s demand.

We used ¹⁵ N isotopic label to trace N. In the beginning of growing season it is used for needles and new shoots formation. And N uptaken in the middle of summer is accumulated in storage organs (buds, branches) to be used in the coming year, when soil is still frozen and soil nutrient uptake is limited. 1 year time lag of plant response on N uptake was found. The tracing material applied on tree needles after 1 year was found in another tree parts that shows the possibility of needle N uptake and the high rate of N reuse and reallocation.