Temperature sensitivity of soil organic matter decomposition in response to land management in semi-arid rangelands of Iran

Abstract

The biotic and abiotic factors can alter the temperature sensitivity of soil organic matter (SOM) decomposition in rangeland areas. This is a key issue that directly affects soil fertility and productivity. On the other hand, most of the rangelands in Iran are involved overgrazing. However, there is a lack of information about these effects, especially, in semi-arid environments. Therefore, the aim of this study was to assess the effect of land management on soil nutrient contents and their stoichiometry on the temperature sensitivity of SOM decomposition (Q10) in semi-arid rangeland ecosystems. Soil samples (at three different soil depths) were collected in adjacent rangeland areas with different management in Iran. Soils were incubated at three different temperatures. The soil heterotrophic respiration was measured using an Alkali absorption method and then was calculated Q10. The decrease in Q10 values was observed with increasing carbon (C), nitrogen (N) and phosphorus (P) of soil content. Changes of Q10 in relation to stoichiometry C:N and P:N showed a linear model and a second-order polynomial model in grazed and ungrazed rangeland respectively. Ungrazed rangeland had the lower Q10 value (0.97) compared to grazed rangeland (1.21). Labile C variability at soil due to effects in land management such as trampling and erosion, altering plant biomass and microbial communities may be able to partly explained variation of Q10 values. Overall, trend of decreasing Q10 values associated with increasing C, N and P contents of soil in all rangeland management can be explained by the high microbial CUE. The obtained results presumably indicated that stoichiometry of C:P:N can play as an important determinant in increase CUE and decrease Q10 in rangeland ecosystems. Overall, the results of this research will valuable for prediction of the condition and succession trend via Q10 and C losses in various grazing management in semi-arid rangeland ecosystems.