Interannual changes in PAR and soil moisture during warm season may be more important than temperature fluctuations in directing annual carbon balance in tundraстатья
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Дата последнего поиска статьи во внешних источниках: 28 мая 2015 г.
Аннотация:The results of 16_year instrumental monitoring (1996–2011) of the state of permafrost, soils, andvegetation influenced by environmental factors in the shrub tundra subzone of northeastern European Russia(Bol’shezemel’skaya Tundra) are described. The field measurement data for CO2 fluxes in 1996 and 1998–1999 have been used to construct regression equations and to simulate intraanual carbon fluxes with a step of3 h. Over the observation period, the average annual and summer air temperatures have been considerablyelevated relative to the local climate norms as of a climatically stable period of 1980–1996. According to ourinstrumental observations, the average winter and annual temperatures, total number of positive degree days,the input of photosynthetically active radiation (PAR), and average seasonal soil moisture increased duringthe next period (1996–2011). Correspondingly, the average annual depth of seasonal soil thawing, and sea_sonal maximum of vascular leaf phytomass stock also increased considerably. According to the model, the net eco_system exchange of carbon (NEE) increased from an equilibrium state in 1996–2002 to a considerable elevation inthe carbon stock in 1998–2011. Thus, the total stock over the 16_year period amounted to 109 g C m–2. An inde_pendent confirmation of the effect assumed by the model is an increase in the aboveground stocks of the liveand dead organic matter in ecosystem. A statistical analysis of the model has demonstrated that, in additionto an increase in PAR and temperature, acting over the long_term period in the observed range in a mode ofmutual compensation relative to NEE, the main reason underlying the observed increase in long_term carbonstock is the amount of vascular plant leaf stock, which has emerged as a major predictor for NEE and, corre_spondingly, acts as an independent parameter of the carbon balance. This increase is most likely determinedby an increase in soil moisture.