Tue, Aug 16, 2022: 10:15 AM-10:30 AM
512A
Background/Question/MethodsThe production and decomposition of leaf litter is a crucial pathway by which carbon moves from aboveground to belowground pools in eastern temperate forests. As climate change brings warmer temperatures and new precipitation patterns to the eastern US, there may be a mismatch in the response of litter production and decomposition. For example, litter production may increase more slowly than decomposition rates with warming temperatures, with cascading consequences for soil carbon storage. Using a combination of observational data from thirteen eastern US forests in the National Ecological Observatory Network (NEON) and experimental data based on samples taken at six of those sites, we quantified the apparent climate sensitivity of litter production and decomposition at several spatial and temporal scales. First, we asked whether litter production is sensitive to both mean annual climate and interannual climate variation using linear mixed effects models. Next, we used experimental mesocosms of leaf litter inoculated with soil from six forests to ask how litter decomposition (measured as CO2 evolution) responds to a suite of 20 laboratory temperature and moisture treatments, and whether those responses are themselves dependent on the local or regional climate of the locations from which soil inoculum originated.
Results/ConclusionsWe found that, given the same aboveground woody productivity, warmer sites had greater leaf litter production than cooler sites, suggesting greater carbon allocation to leaves in warmer forests and greater allocation to woody growth in cooler forests. However, we found no evidence that leaf litter production is sensitive to interannual variation in temperature. In contrast, litter decomposition was highly sensitive to temperature, with decomposition rates at 25℃ on average 7% higher than at 15℃. The origin of the soil inoculum drove the magnitude of this temperature effect: mesocosms with soil from warmer sites exhibited a greater increase in decomposition due to a higher incubation temperature than those originating from cooler sites. Similarly, decomposition in mesocosms with soil from wetter locations was more sensitive to experimental moisture manipulation. Together, these patterns suggest that while litter production is related to mean annual climate, it is relatively insensitive to interannual climate variation. In contrast, litter decomposition is strongly sensitive to temperature and moisture at various scales, and that sensitivity is itself dependent on prior climate conditions. Therefore as forests experience novel climate regimes, the rates of litter production and decomposition may change independently, generating greater uncertainty for future soil carbon storage.
Results/ConclusionsWe found that, given the same aboveground woody productivity, warmer sites had greater leaf litter production than cooler sites, suggesting greater carbon allocation to leaves in warmer forests and greater allocation to woody growth in cooler forests. However, we found no evidence that leaf litter production is sensitive to interannual variation in temperature. In contrast, litter decomposition was highly sensitive to temperature, with decomposition rates at 25℃ on average 7% higher than at 15℃. The origin of the soil inoculum drove the magnitude of this temperature effect: mesocosms with soil from warmer sites exhibited a greater increase in decomposition due to a higher incubation temperature than those originating from cooler sites. Similarly, decomposition in mesocosms with soil from wetter locations was more sensitive to experimental moisture manipulation. Together, these patterns suggest that while litter production is related to mean annual climate, it is relatively insensitive to interannual climate variation. In contrast, litter decomposition is strongly sensitive to temperature and moisture at various scales, and that sensitivity is itself dependent on prior climate conditions. Therefore as forests experience novel climate regimes, the rates of litter production and decomposition may change independently, generating greater uncertainty for future soil carbon storage.