Assessing the spatial variability in peak season CO2 exchange characteristics across the Arctic tundra using a light response curve parameterization

[摘要] This paper aims to assess the spatial variability in the response ofCO₂ exchange to irradiance across the Arctic tundra during peak seasonusing light response curve (LRC) parameters. This investigation allows us tobetter understand the future response of Arctic tundra under climaticchange. Peak season data were collected during different years (between 1998and 2010) using the micrometeorological eddy covariance technique from 12circumpolar Arctic tundra sites, in the range of 64–74° N.

The LRCs were generated for 14 days with peak net ecosystem exchange (NEE)using an NEE–irradiance model. Parameters from LRCs represent site-specifictraits and characteristics describing the following: (a) NEE at light saturation(F_csat), (b) dark respiration (R_d), (c) light use efficiency(α), (d) NEE when light is at 1000 μmol m⁻² s⁻¹(F_c1000), (e) potential photosynthesis at light saturation(P_sat) and (f) the light compensation point (LCP).

Parameterization of LRCs was successful in predicting CO₂ flux dynamicsacross the Arctic tundra. We did not find any trends in LRC parametersacross the whole Arctic tundra but there were indications for temperatureand latitudinal differences within sub-regions like Russia and Greenland.Together, leaf area index (LAI) and July temperature had a high explanatory power of thevariance in assimilation parameters (F_csat, F_c1000 and P_sat,thus illustrating the potential for upscaling CO₂ exchange for thewhole Arctic tundra. Dark respiration was more variable and less correlatedto environmental drivers than were assimilation parameters. This indicatesthe inherent need to include other parameters such as nutrient availability,substrate quantity and quality in flux monitoring activities.

[学科分类] 地球化学与岩石