|ZHANG, MINGCHU - University Of Alaska|
|ZHAO, AIQIN - University Of Alaska|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/21/2014
Publication Date: 5/1/2014
Citation: Zhang, M., Zhao, A., He, Z. 2014. Distribution and biodegradability of water soluble organic carbon and nitrogen in subarctic Alaskan soils under three different land uses. In: He, Z., Zhang, H., editors. Applied Manure and Nutrient Chemistry for Sustainable Agriculture and Environment. Amsterdam, the Netherlands: Springer. p. 313-332.
Interpretive Summary: Climate change and demand of bioenergy have stimulated new aspirations on agricultural production in the subarctic regions. The Delta Junction area is a major small grain production region in the subarctic Alaska, USA. The arable land was developed in 1978 by clearing native forest. Later, part of the arable land was converted to grassland through the Conservation Reserve Program (CRP) administrated by United States Department of Agriculture (USDA). As increased understanding of impact of different land uses on characteristics and biodegradability of soil water extractable organic matter (WEOM) will provide information for future land and water quality management in the subarctic region, this chapter systematically presents and discusses the quantity, distribution, and features of soil WEOM, especially its critical components, organic C and N, as affected by the three land uses in the subarctic Alaskan region. Data presented in this chapter revealed that the impact of land uses was mainly on the quantity, rather than on the composition, of WEOM. Laboratory incubation data demonstrated that the biodegradability of cold or hot water extractable organic was significantly correlated with the protein-like component, indicating that a protein-like fluorophore represented a labile fraction in cold and hot WEOM pools. Knowledge and insight derived from this work may be helpful in enhancing the sustainability of the agricultural land management in other climatic regions.
Technical Abstract: Water-extractable organic matter (WEOM) contains labile organic carbon (C) and nitrogen (N) and is sensitive to soil management. However, knowledge about quantitative changes of water soluble organic C (WSOC) and N (WSON) impacted by land use conversion is still limited. In this chapter, the level and degradability of WSOC and WSON in soils sampled from subarctic Alaska under three different land use managements (i. e. forest, agriculture; and grassland converted from agricultural use and under a Conservation Reserve Program-CRP) were examined. There was no statistical difference of WSOC and WSON among three land uses . Furthermore, WSOC was dominated by large (>0.45 µm) and small (<1 kDa) size molecules in CRP and forest soils, while small molecules predominated in agricultural soils. All WEOM fractions displayed three similar fluorophore components (two humic acid-like, fulviclike and a protein-like), indicating that they were major components of WSOC and WSON, and the impact of land uses was mainly on the quantity, rather than on the composition, of WEOM. Laboratory incubation revealed that the biodegradability of cold or hot WEOC was significantly correlated (p<0.01) with the protein-like component, indicating that a protein-like fluorophore represented a labile fraction in cold and hot WEOM pools. High correlation was found between cold and hot WSON and other chemically extracted potential mineralizable N indexes, showing that hot WSON was a part of acid or alkaline hydrolysable N. Information derived from this chapter increased understanding of subarctic soil WEOM properties and its biodegradability