Components of soil respiration and its temperature sensitivity in four types of forests along an elevational gradient in Shennongjia,China

Aims Quantifying forest soil respiration(Rs),its components of heterotrophic respiration(RH) and autotrophic respiration(RA),and their responses to temperature are vital to accurately evaluate response of the terrestrial car-bon balance to future climate change.Our specific objectives were to(1) compare patterns of soil respiration of four types of forests,(2) evaluate relationships among soil respiration and temperature and water content and(3) find the regulation of Q10 value in relation to elevation.Methods Four types of forests along an elevational gradient at Shennongjia were investigated.The trenching plot approach was used to partition soil respiration into autotrophic respiration and heterotrophic respiration.Rates of soil respiration were measured twice a month from July 2009 to June 2010.Soil temperature and soil water content were measured at the same time.Important findings Annual soil respiration of the four types of forests was 1.63,1.79,1.74 and 1.35 μmol CO2·m-2·s-1,and annual heterotrophic respiration was 1.13,1.12,1.12,0.80 μmol CO2·m-2·s-1.Soil respiration and its components displayed obvious seasonal dynamics,with maximum values in summer and minimum values in winter.The soil respiration flux of broad-leaved forest was significantly higher than that of coniferous forests,but there was no obvious differentiation between broad-leaved forests.Soil temperature was the main factor that affected soil respiration and its components,and there were significant exponential relationships between them.There was no significant relationship between soil water content and soil respiration flux,except in broad-leaved forest with a mild inhibition phenomenon.Q10 values of four types of forests were 2.38,2.68,2.99 and 4.24.Soil respiration was more sensitive to temperature along the elevation gradient,while Q10 value increased with eleva-tion increase.