Abstract
The variation of different ecosystems on the terrestrial carbon balance is predicted to be large. We investigated a typical arid region with widespread saline/alkaline soils, and evaluated soil respiration of different agricultural and natural ecosystems. Soil respiration for five ecosystems together with soil temperature, soil moisture, soil pH, soil electric conductivity and soil organic carbon content were investigated in the field. Comparing with the natural ecosystems, the mean seasonal soil respiration rates of the agricultural ecosystems were 96%–386% higher and agricultural ecosystems exhibited lower CO2 absorption by the saline/alkaline soil. Soil temperature and moisture together explained 48%, 86%, 84%, 54% and 54% of the seasonal variations of soil respiration in the five ecosystems, respectively. There was a significant negative relationship between soil respiration and soil electrical conductivity, but a weak correlation between soil respiration and soil pH or soil organic carbon content. Our results showed that soil CO2 emissions were significantly different among different agricultural and natural ecosystems, although we caution that this was an observational, not manipulative, study. Temperature at the soil surface and electric conductivity were the main driving factors of soil respiration across the five ecosystems. Care should be taken when converting native vegetation into cropland from the point of view of greenhouse gas emissions.
Highlights
The dynamics of the amount of global carbon is the key issue of global warming, and soil carbon pools are correlated with carbon dioxide flux emission from soils [1]
Quantifying the seasonal and spatial variations in the CO2 efflux of different ecosystems is critical to understanding climate change
The mean carbon dioxide flux in the nine repeated measurements of in every observation time was always positive, with fluxes being lowest in the early morning and highest at 12:00 or 14:00, which coincided with changes in the soil temperature at the surface (0 cm depth) better than changes in the temperature at 10 cm soil depth (Table 2)
Summary
The dynamics of the amount of global carbon is the key issue of global warming, and soil carbon pools are correlated with carbon dioxide flux emission from soils [1]. Soil respiration is considered the largest terrestrial–atmospheric carbon exchange [2]. Any alterations in soil CO2 efflux could potentially exacerbate greenhouse-gas-induced climate warming [3]. Quantifying the seasonal and spatial variations in the CO2 efflux of different ecosystems is critical to understanding climate change. The temporal variations in soil respiration (Rs) can be characterized as diurnal/weekly, seasonal, annual, and centennial [4]. Because of the great variability on a temporal scale and the resulting measurement errors [5], it is necessary to measure Rs in situ in every month of growing season to accurately estimate annual Rs of different ecosystems
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