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- Title
Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers.
- Authors
Shen, W.; Jenerette, G. D.; Hui, D.; Scott, R. L.
- Abstract
The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground primary production (ANPP) and soil respiration. How the PPT legacy influences whole ecosystem-level carbon (C) fluxes has rarely been quantitatively assessed, particularly at longer temporal scales. We parameterized a process-based ecosystem model to a semiarid savanna ecosystem in southwestern US, calibrated and evaluated the model performance based on 7 years of eddy covariance measurements, and conducted two sets of simulation experiments to assess interdecadal and interannual scale PPT legacy effects over a 30 year simulation period. The results showed that decreasing the previous period/year PPT (dry legacy) always imposed positive impacts on net ecosystem production (NEP) whereas increasing the previous period/year PPT (wet legacy) had negative impacts on NEP. The simulated dry legacy impacts were mostly positive on gross ecosystem production (GEP) and negative on ecosystem respiration (Re) but the wet legacy impacts were mostly negative on GEP and positive on Re. Although the direction and magnitude of GEP and Re responses to the simulated dry and wet legacies were influenced by both the previous and current PPT conditions, the NEP responses were predominantly determined by the previous PPT characteristics including rainfall amount, seasonality and event size distribution. Larger PPT di erence between periods/years resulted in larger legacy impacts, with dry legacies fostering more C sequestration and wet legacies more C release. By analyzing the resource pool (C, N, and H2O) responses to the simulated dry and wet legacies, we found that the carryover of soil N between periods/ years was mainly responsible for the GEP responses while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the Re responses. These simulation results suggest that previous PPT conditions can exert substantial legacy impacts on current ecosystem C balance, which should be taken into account while assessing the response of dryland ecosystem C dynamics to future PPT regime changes.
- Subjects
ARID regions; ECOSYSTEMS; METEOROLOGICAL precipitation; BIOGEOCHEMICAL cycles; SOIL respiration
- Publication
Biogeosciences Discussions, 2015, Vol 12, Issue 13, p9613
- ISSN
1810-6277
- Publication type
Article
- DOI
10.5194/bgd-12-9613-2015