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

在西伯利亚东部的永久冻土的陆地生态系统显示出大的年际变化取决于水分条件。为了观察土壤水分和植被的变化，在雅库茨克附近的Spasskaya垫实验林进行了观测。土壤湿度的变化取决于降水和蒸腾之间的平衡。土壤水分收支分析表明，在极端湿润的条件下，径流量很可能是微不足道的。土壤和液水的同位素组成表明，在干旱条件下，活动层下部的土壤水分向上运移，用于蒸腾，而在湿润条件下，雨水下渗，被植物吸收，植被对土壤水分有响应。落叶松针叶的光合活性每年相对稳定，这是由雪融提供的土壤水分的恒定有效性所解释的。另一方面，在后半个夏天，在干旱期间，这是有限的。落叶松GBH生长量与当年土壤含水量也有一定的相关性。落叶松针叶碳同位素比值与前一年夏末的土壤水分呈负相关，表明当年光合作用吸收的碳在储存后即用于次年的针叶生产。13C示踪实验的结果也支持这一点。凋落物产量的增加与土壤水分的增加有2年的时滞，这是前一年夏末有利于土壤水分的携带和辐射的结果。

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.