ARS | Publication request: Land-Use Influences Carbon Fluxes in Northern Kazakhstan

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 10, 2008
Publication Date: January 8, 2010
Citation: Perez-Quezada, J.F., Saliendra, N.Z., Akshalov, K., Johnson, D.A., Laca, E.A. 2010. Land-Use Influences Carbon Fluxes in Northern Kazakhstan. Rangeland Ecology and Management. 63: 82-93.

Interpretive Summary: A mobile, closed-chamber system (CC) was used to measure carbon and water fluxes on four land-use types common in the Kazakh steppe ecoregion. Land uses represented crop (wheat or barley, WB), abandoned land (AL), crested wheatgrass (CW) and virgin land (VL). Measurements were conducted during the growing season of 2002 in northern Kazakhstan at three locations (blocks) 15 to 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 were used to model gross primary production (GPP) asnd ET as a function of photosynthetically active radiation (Q); RE and RS were modeled based on air (Tair) and soil (Ts) temperature, respectively. GPP, RE, RS and ET were estimated for the entire year using continuous 20-minute means of Q, Tair and Ts. Annual NEE indicated that AL gained 536 g CO2.m-2, while WB lost -191 g CO2.m-2, CW was near equilibrium (-14 g CO2.m-2), and VL exhibited considerable carbon accumulation (153 g CO2.m-2). The lower GPP values of the land-use types dominated by native species (CW and VL) compared to WB and AL were compensated by positive NEE values that were maintained during a longer growing season. As expected, VL and CW allocated a larger proportion of their carbon assimilates belowground. Non-growing season RE accounted for about 19% of annual RE in all land-use types. The results of this landscape-level study suggest that carbon lost by cultivation of virgin lands is partially being restored when fields are left uncultivated, and that virgin lands are net sinks of carbon. Estimations of carbon balances have important management implications such as estimation of ecosystem productivity and carbon credit certification.

Technical Abstract: An understanding of carbon cycling is important to maintain sustainable rangeland ecosystems. Rangelands in the western U.S. are similar to those in Central Asia. We used a combination of meteorological and computer modeling techniques to quantitatively assess carbon loss and gain for four major land-use types in northern Kazakhstan. The land uses represented wheat/barley cropland, abandoned cropland, crested wheatgrass, and native rangeland (virgin land). Measurements were conducted during the growing season of 2002 in northern Kazakhstan at three locations. Results showed that the greatest carbon gain occurred on abandoned land followed by rangeland. Carbon gain equaled carbon loss on land planted to crested wheatgrass. Wheat-barley croplands suffered a net loss of carbon. Soil organic carbon and nitrogen contents were highest for rangeland and decreased with greater cultivation. Our results suggest that carbon and nitrogen lost by cultivation on rangelands are being partially restored when croplands are abandoned. Analysis of carbon balances has important management implications for biomass production and carbon sequestration.