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As per international policy agendas on mitigation of greenhouse gas emission, the impact change in land use on soil organic carbon (SOC) stocks is of major concern. There has been no systematic study carried out to estimate SOC pool in the catchment of hydroelectric reservoirs. An assessment of SOC stock along altitudinal gradient was carried out in the catchment of proposed Kotli Bhel 1A hydroelectric reservoir located in Uttarakhand, India. The SOC stocks were found to be decreasing with altitude, ( i.e. soil under high altitude forests having more SOC and vice versa). The SOC map developed from the normalized difference vegetation index also verified the results and allowed for spatially explicit targeting of potential climate change mitigation efforts through soil carbon sequestration. The results also revealed that the alpine forest soil has a greater potential of C sequestration compared to devdar, oak, and chir species found in the catchment. This information will help policymakers or environmentalists to take preventive measures for afforestation of forest species that can sequester more C. [ABSTRACT FROM AUTHOR]

In a warmer world, soil CO2 emissions are likely to increase. There is still much discussion about which soil organic C (SOC) pools are more sensitive to increasing temperatures. While the temperature sensitivity of C stabilized by biochemical recalcitrance or by sorption to mineral surfaces has been characterized, few studies have been carried out on the temperature sensitivity-expressed as Q10-of C physically protected inside soil macroaggregates (0.2-2 mm). It has been suggested that increasing the availability of labile SOC by exposing C through macroaggregate crushing would decrease Q10, i.e., the temperature dependence of soil CO2 emissions. To test this hypothesis, the temperature dependence of CO2 emissions from C physically protected in macroaggregates was measured through 21-d laboratory incubations of crushed and uncrushed soils, at 18°C and 28°C. 199 topsoil samples, acidic or calcareous, with SOC ranging from 2 to 121 g kg−1 soil were investigated. The CO2 emissions were slightly more sensible to temperature than to C deprotection: about 0.3 mg C g−1 soil (= 13 mg C g−1 SOC) and 0.2 mg C g−1 (= 12 mg C g−1 SOC) were additionally mineralized, in average, by increasing the temperature or by disrupting the soil structure, respectively. The mean Q10 index ratio of CO2 emitted at 28°C and 18°C was similar for crushed and uncrushed soil samples and equaled 1.6. This was partly explained because Q10 of macro-aggregate-protected C was 1. The results did not support the initial hypothesis of lower temperature dependence of soil CO2 emissions after macroaggregate disruption, although a slight decrease of Q10 was noticeable after crushing for soils with high amounts of macroaggregate-protected C. Field research is now needed to confirm that soil tillage might have no effect on the temperature sensitivity of SOC stocks. [ABSTRACT FROM AUTHOR]

Models are important for predicting how soil organic carbon alters with changing environment and management. We tested three different ways of parameterizing the Rothamsted Carbon Model in four treatments from the long-term static fertilization experiment at Bad Lauchstädt. Four bare fallow plots were also used to test different ways of parameterizing the model. Model version 1 used Δ14C to estimate the amount of inert organic matter whereas in versions 2 and 3 a long-term bare fallow treatment was used to estimate this amount. In version 1, C inputs were optimized from the long-term data. In version 2, crop inputs were estimated from published functions that relate C inputs to crop yields. In version 3, C inputs (average or minimum data) were taken from actual measurements of crop and root residues. In both versions 2 and 3, rhizodeposition was included as additional input of 50% (winter wheat, spring barley) or 35% (potatoes, sugar beet) of the C input by crop and root residues. The performance of the three versions decreased in the order 3 > 2 ≫ 1. Model efficiency and root mean square error were 0.86 and 6.1 for version 3 and 0.81 and 7.0 for version 2. Overall, our results indicate the need for a long-term treatment for calibration. Setting total C inputs as a function of crop yield performed satisfactorily. Measurements of crop and root residues gave a good representation of total C inputs when carbon from rhizodeposition was included as additional input. [ABSTRACT FROM AUTHOR]