Carbon and Nitrogen Contents of Expanding Pinyon-Juniper Woodlands
Rau, B.M., Tausch, R., Reiner, A., Johnson, D.W., Chambers, J.C. and Blank, R.R. 2012. Developing a model framework for predicting effects of woody expansion and fire on ecosystem carbon and nitrogen in a pinyon-juniper woodland. Journal of Arid Environments 76: 97-104.
Working in Underdown Canyon in the Shoshone Mountain Range on the Humboldt-Toiyabe National Forest in Nye and Lander Counties of Nevada (USA), Rau et al. developed a biomass, carbon (C) and nitrogen (N) spreadsheet model that uses tree cover, soil chemistry, soil physical properties and vegetation chemistry to estimate biomass, carbon and nitrogen accumulation on the landscape in response to woodland expansion, as well as the C and N losses associated with prescribed burning, in order to further explore this ongoing landscape-transforming phenomenon, which many believe is primarily driven by the ongoing rise in the air's CO2 content. See, in this regard Range Expansion in our Topical Archive.
In describing their results, the six scientists say their observations-based model indicates that in treeless sagebrush-steppe ecosystems, biomass accounts for less than 10% of total estimated ecosystem C and N to a soil depth of 53 cm; but they indicate that as tree cover increases to near-closed-canopy conditions, aboveground biomass may account for nearly 53% of total estimated ecosystem C and 13% of total estimated ecosystem N to a soil depth of 53 cm.
Given such findings, as the air's CO2 content rises, it is apparent that the phenomenon studied by Rau et al. provides its own negative feedback to CO2-induced global warming, as the CO2-driven expansion of trees onto sagebrush-steppe ecosystems greatly increases the amount of carbon that those ecosystems remove from the atmosphere and store in the plants that comprise them, and which they transfer to the soil beneath them for even more secure and voluminous storage.
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