Abstract
Although soil respiration is the largest contributor to C flux from terrestrial ecosystems to the atmosphere, our understanding of its characteristics and carbon budget in alpine meadow is rather limited because of extremely geographic situation. This study was designed to examine soil CO2 efflux characteristics of diurnal and seasonal variation, thus obtaining estimates of carbon balance of Kobresia pygmaea meadow in Qinghai-Tibet plateau. The results showed that the soil respiration of diurnal and seasonal rate changed little in growing season and was mainly affected by temperature, and single peak curve that showed afternoon appeared. Composite model which was set by soil respiration rate, soil moisture content and temperature (atmospheric temperature and soil temperature) could explain better the variations of soil respiration rate. The variation range of Q10 ranged from 1.28 to 2.34, which was sensitive to temperature in green-up period and late growth stage, and decreased in growth peak period. Meanwhile, during the growing seasons the observed amount of annual carbon fixation via primary production for Kobresia pygmaea meadow ecosystem was about 120.21 g C·m-2·a-1. The carbon dioxide output via soil heterotrophic respiration was about 37.54 g C·m-2·a-1. So carbon budget had more input than output. The Kobresia pygmaea meadow ecosystem has stronger potential to absorb carbon dioxide, it was a sink of atmospheric CO2, and the plant community had a net carbon gain of 82.67 g C·m-2·a-1.
Highlights
An increase in the emission of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the soil surface to the atmosphere has been of worldwide concern over the last several decades [1]
The results showed that the soil respiration of diurnal and seasonal rate changed little in growing season and was mainly affected by temperature, and single peak curve that showed afternoon appeared
The peak of daily CO2 flux occurred during Beijing time 13:00-15:00 in June, and the bathos appeared during 1:00-3:00, the average diurnal CO2 fluxes were 1.82
Summary
An increase in the emission of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the soil surface to the atmosphere has been of worldwide concern over the last several decades [1]. Soils are of particular importance in the atmospheric CO2 budget and a large reservoir of terrestrial ecosystem, which is recently estimated at 1600 Pg and more than twice the atmospheric CO2-pool, 750 Pg [3] [4]. Soil respiration (Rs) plays a large role in carbon (C) cycling in terrestrial ecosystems, including root respiration and microbial respiration [7]. Microbial respiration primarily depends on the availability of substrate and community composition [7]. Both components are affected by temperature and moisture [8]. Interest in grassland and forest ecosystem that controls soil CO2 respiration is growing because of the potential for climatic change in a certain region of China to affect net soil CO2 productivity and exchange between soil and atmosphere [9]. Knowledge about its characteristics and carbon budget in alpine meadow of Qinghai-Tibet plateau is still rudimentary
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