Interannual variation in carbon uptake by vegetation of Taiga in Eastern Siberia and its response to global warming

东西伯利亚永久冻土带陆地生态系统年际变化较大，取决于湿度条件。在雅库茨克附近的Spasskaya垫地试验林进行了土壤水分和植被的变化观测。土壤湿度的变化取决于降水和蒸腾之间的平衡。径流通常可以忽略不计，然而，土壤水分收支分析表明，它可能发生在极端潮湿的条件下。土壤和树液的同位素组成表明，干旱条件下，活动层下部土壤水分向上运移用于蒸腾，湿润条件下雨水则被植物渗透吸收。植被对土壤湿度有反应。落叶松针叶的光合活性每年相对稳定，这与积雪融化提供的土壤水分持续有效有关。另一方面，由于干旱，夏季后半期的产量受到限制。落叶松的GBH增量也与当年土壤湿度呈相关关系。落叶松针叶碳同位素比值与前一年夏末土壤湿度呈负相关，说明光合作用吸收的碳曾经储存起来，次年用于制针。13C示踪实验结果也支持这一观点。针叶凋落物产量的增加与土壤水分的增加有2年的时滞关系，这与前一年夏末土壤水分携带和辐射的有利条件有关。

Terrestrial ecosystem on permafrost in Eastern Siberia shows large interannual variation depending on moisture condition. In order to observe the variation observations on soil moisture and vegetation were carried out at Spasskaya Pad Experimental Forest near Yakutsk. Soil moisture varied depending on the balance between precipitation and transpiration. Runoff was negligible usually, however, analysis of soil moisture budget suggested that it probably occurred in extremely wet condition. The isotopic composition of soil and sap water showed that during drought soil water in lower part of active layer was transported upward and used for transpiration, while under wet condition rainwater infiltrated and taken up by plants.Vegetation responds to the soil moisture. Photosynthetic activity of larch needle was relatively constant every year, which is elucidated by constant availability of soil moisture supplied from snow thaw. On the other hand, that in latter half of summer was limited during drought. GBH increment of larch also showed correlation with the soil moisture at the year. Carbon isotope ratio of larch needles showed negative correlation with the soil moisture in the late summer of the previous year, indicating that carbon taken up by photosynthesis once stored then used for needle production in the following year. Results in 13C tracer experiments also supported this. Needle litter fall production increased with two-year time-lag from the increase in soil moisture, which was elucidated by the favorable conditions in the late summer of the previous year on the soil moisture carried over and radiation.