Impacts of anthropogenic N additions on nitrogen mineralization from plant litter in exotic annual grasslands

• Published in: Soil biology & biochemistry Vol. 39; no. 1; pp. 24 - 32
• Main Authors: Sirulnik, Abby G., Allen, Edith B., Meixner, Thomas, Allen, Michael F.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2007; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; anthropogenic activities; atmospheric deposition; Biochemistry and biology; biodegradation; Biological and medical sciences; Bromus diandrus; carbon; Chemical, physicochemical, biochemical and biological properties; Decomposition; fertilizer application; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; grasses; introduced species; lignin; Litter; Mineralization; Nitrogen; nitrogen content; nitrogen fertilizers; Nitrogen, phosphorus, potassium fertilizations; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant litter; Soil science; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Stable isotope; stable isotopes; California; Stable isotope; Decomposition; Litter; Nitrogen; Mineralization; Grassland; Soils; Nitrogen fertilization; Soil science; Isotopes; Anthropogenic factor
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2006.04.048

Urban regions of southern California receive up to 45 kg N ha –1 y –1 from nitrogen (N) deposition. A field decomposition study was done using 15N-labelled litter of the widespread exotic annual grass Bromus diandrus to determine whether elevated soil N is strictly from N deposition or whether N mineralization rates from litter are also increased under N deposition. Tissue N and lignin concentrations, which are inversely related in field sites with high and low N deposition, determine the rate at which N moves from plant litter to soil and becomes available to plants. The effect of soil N on N movement from litter to soil was tested by placing litter on high and low N soil in a factorial experiment with two levels of litter N and two levels of soil N. The litter quality changes associated with N deposition resulted in faster rates of N cycling from litter to soil. Concentrations of litter-derived N in total N, NH 4 +, NO 3 −, microbial N and organic N were all higher from high N/low lignin litter than from low N/high lignin litter. Litter contributed more N to soil NH 4 + and microbial N in high N than low N soil. At the end of the study, N mineralized from high N litter on high N soil accounted for 46% of soil NH 4 + and 11% of soil NO 3 −, compared to 35% of soil NH 4 + and 6% of soil NO 3 − from low N litter on low N soil. The study showed that in high N deposition areas, elevated inorganic soil N concentrations at the end of the summer N deposition season are a result of N mineralized from plant litter as well as from N deposition.