Soil respiration at mean annual temperature predicts annual total across vegetation types and biomes

Abstract

Soil respiration (SR) constitutes the largest flux of CO₂ from terrestrial ecosystems to the atmosphere. However, there still exist considerable uncertainties as to its actual magnitude, as well as its spatial and interannual variability. Based on a reanalysis and synthesis of 80 site-years for 57 forests, plantations, savannas, shrublands and grasslands from boreal to tropical climates we present evidence that total annual SR is closely related to SR at mean annual soil temperature (SR_MAT), irrespective of the type of ecosystem and biome. This is theoretically expected for non water-limited ecosystems within most of the globally occurring range of annual temperature variability and sensitivity (<i>Q</i>₁₀). We further show that for seasonally dry sites where annual precipitation (<i>P</i>) is lower than potential evapotranspiration (PET), annual SR can be predicted from wet season SR_MAT corrected for a factor related to <i>P</i>/PET. Our finding indicates that it can be sufficient to measure SR_MAT for obtaining a well constrained estimate of its annual total. This should substantially increase our capacity for assessing the spatial distribution of soil CO₂ emissions across ecosystems, landscapes and regions, and thereby contribute to improving the spatial resolution of a major component of the global carbon cycle.