QUANTIFYING TEMPERATURE SENSITIVITY OF SOIL RESPIRATION ACROSS A RANGE OF SEMI-ARID BIOMES

Soils in semi-arid regions store approximately 10% of earth’s soil organic carbon, the substrate which microbes oxidize, resulting in the largest source of carbon to the atmosphere from terrestrial ecosystems. Semi-arid regions are expected to experience increased temperatures and altered precipitation regimes over the next 100 years, altering soil temperature and water, the two predominant drivers in soil respiration processes. In this study we quantify the temperature sensitivity of soil respiration in five semi-arid biomes ranging from desert grassland to ponderosa pine forest along an elevational/climate gradient in central New Mexico. We measured statistically similar temperature sensitivities in 4 of 6 biomes ranging from 3-7 % with a mean of 5± 0.9 % increase in soil respiration (Rs) per degree increase in soil temperature. Temperature sensitivity at the desert shrubland site was an exception with a minimal 1% increase, and we measured no significant relationship in the ponderosa pine forest. The integration of water into the response models yielded minimal change in the sensitivities between sites except at the juniper savanna site where SWC was the dominant abiotic factor regulating Rs. Potential mechanisms driving this convergence of temperature sensitivity are the multi-year temporal scale of our measurements which dampen out any short-term responses, as well as mediation due to interacting co-varying controls on temperature sensitivity , and selection pressures for microbial populations that maximize growth under prevailing resource and temperature conditions across our gradient. Implications for global models are discussed.MS BiologyMastersUniversity of New Mexico. Biology Dept.Litvak, MarcyCollins, ScottSinsabaugh, Rober