Land Use Influences Carbon Fluxes in Northern KazakhstanReport as inadecuate

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A mobile, closed-chamber system CC was used to measure carbon and water fluxes on four land-use types common in theKazakh steppe ecoregion. Land uses represented crop wheat or barley, WB, abandoned land AL, crested wheatgrass CW, andvirgin land VL. Measurements were conducted during the growing season of 2002 in northern Kazakhstan at three locationsblocks 15–20 km apart. The CC allowed the measurement of the carbon flux components of net ecosystem exchange NEE,ecosystem respiration RE and soil respiration RS, together with evapotranspiration ET. Nonlinear regression analyses wereused to model gross primary production GPP and ET as a function of photosynthetically active radiation Q; RE and RS weremodeled based on air Tair and soil Ts temperature, respectively. GPP, RE, RS, and ET were estimated for the entire year with theuse of continuous 20-min means of Q, Tair, and Ts. Annual NEE indicated that AL gained 536 g CO2 ?m22, WB lost 2191 gCO2 ?m22, CW was near equilibrium 214 g CO2 ?m22, and VL exhibited considerable carbon accumulation 153 gCO2 ?m22. The lower GPP values of the land-use types dominated by native species CWand VL compared to WB and AL werecompensated by positive NEE values that were maintained during a longer growing season. As expected, VL and CW allocated alarger proportion of their carbon assimilates belowground. Non–growing-season RE accounted for about 19% of annual RE in allland-use types. The results of this landscape-level study suggest that carbon lost by cultivation of VLs is partially being restoredwhen fields are left uncultivated, and that VLs are net sinks of carbon. Estimations of carbon balances have important managementimplications, such as estimation of ecosystem productivity and carbon credit certification.

Author: Saliendra, Nicanor Z.; - Akshalov, Kanat; - Johnson, Douglas A.; - Pérez Quezada, Jorge; - Laca, Emilio A.; -



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