Mon, Aug 02, 2021:On Demand
Background/Question/Methods
Soils are the largest terrestrial carbon (C) stock and therefore provide one of the most promising opportunities for enhanced C sequestration. Yet, global change factors, such as nitrogen (N) deposition, have uncertain implications for the terrestrial C sink. N fertilization experiments across independent sites indicate conflicting soil organic matter responses to N addition, ranging from soil C gains to soil C losses. Nitrogen added in excess is a probable cause of this variability, as it can lead to soil acidification. Therefore, there is a threshold at which N addition transitions from increasing soil C to causing soil C losses. The magnitude and direction at which N addition effects soil C stocks is dependent on interactions between microbial physiology, soil mineralogy, and soil acidity, which varies across ecosystems and is further complicated by opposing responses of separate soil C pools (particulate and mineral-protected organic matter). To better understand the mechanisms driving soil C pool responses to N deposition, we recorded soil C and N cycle changes in long term fertilization sites throughout North America and employed a lab incubation experiment to decouple the effects of N addition from acidification.
Results/Conclusions Soils were collected from tundra, desert, shrub steppe, temperate forest and tropical forest ecosystems with mean annual temperature and precipitation ranging from -3 to 38 oC and 305 to 1500 mm, respectively. Preliminary results demonstrate that C mineralization was highest in control soils, lowest under N treatments, and intermediate under acid addition, although the magnitude at which nitrogen addition and acidification effect soil C is site specific. Because the magnitude of microbial responses to N fertilization was site dependent, other factors, such as soil mineralogy or microbial community composition, may influence soil C pool responses to N addition. Reconciling the conflicts between site-to-site soil C responses is vital to mitigating global change. This work will influence biogeochemical and terrestrial ecosystem models by increasing our ability to project C sequestration potentials, and through helping shape on the ground climate change mitigation strategies.
Results/Conclusions Soils were collected from tundra, desert, shrub steppe, temperate forest and tropical forest ecosystems with mean annual temperature and precipitation ranging from -3 to 38 oC and 305 to 1500 mm, respectively. Preliminary results demonstrate that C mineralization was highest in control soils, lowest under N treatments, and intermediate under acid addition, although the magnitude at which nitrogen addition and acidification effect soil C is site specific. Because the magnitude of microbial responses to N fertilization was site dependent, other factors, such as soil mineralogy or microbial community composition, may influence soil C pool responses to N addition. Reconciling the conflicts between site-to-site soil C responses is vital to mitigating global change. This work will influence biogeochemical and terrestrial ecosystem models by increasing our ability to project C sequestration potentials, and through helping shape on the ground climate change mitigation strategies.