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Net Nitrogen Mineralization in Natural Ecosy.tems across the Conterminous US

International Journal of Geosciences 2013年第9期4卷 1300-1312页

作者： leeanna y. chapman Steven G. McNulty.Ge Sun y.ng Zhang Department of Marine Earth and Atmospheric Sciences North Carolina State University Raleigh USA Eastern Forest Environmental Threat Assessment Center United States Department of Agriculture—Forest Service Raleigh USA

Nitrogen is the primary.nutrient limiting ecosy.tem productivity.over most of the US. Although soil nitrogen content is important, knowledge about its spatial extent at the continental scale is limited. The objective of this study.was to estimate net nitrogen mineralization for the conterminous US (CONUS) using an empirical modeling approach by.scaling up site level measurements. Net nitrogen mineralization and total soil nitrogen data across the CONUS were obtained from three different ecosy.tems: low elevation forests, high elevation forests, and grasslands. Equations to predict net nitrogen mineralization were developed through stepwise linear regression using total Kjeldahl nitrogen, air temperature, precipitation, and nitrogen deposition as predictor variables for four categories: low elevation high temperature forests (coefficient of determination, R2 = 0.83), low elevation low temperature forests (R2 = 0.74), high elevation forests (R2 = 0.80), and grasslands (R2 = 0.88). A map of net nitrogen mineralization was developed in GIS using these equations and national-scale databases for the CONUS. The result shows that net nitrogen mineralization varies widely.across the US. Grasslands were predicted to have the lowest net nitrogen mineralization, while low elevation forests in the east had the highest. Mean values were 14.3 kg·ha-1·y.-1 for grasslands, 22.6 kg·ha-1·y.-1 for high elevation forests, 58 kg·ha-1·y.-1 for low elevation low temperature forests, and 82.9 kg·ha-1·y.-1 for low elevation high temperature forests. This continental scale estimation of net nitrogen mineralization provides a means of comparing net nitrogen mineralization across regions, and the databases developed from this study.are useful for accounting for nitrogen limitations in large scale ecosy.tem modeling.

关键词： Nitrogen Limitation Total Kjeldahl Nitrogen Forest Grassland Linear Regression Plant Available Nitrogen

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