Phosphate additions have no effect on microbial biomass and activity in a northern hardwood forest

• Published in: Soil biology & biochemistry Vol. 43; no. 12; pp. 2441 - 2449
• Main Authors: Groffman, Peter M., Fisk, Melany C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.12.2011; Elsevier
• Subjects: acid soils; acidification; Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Calcium; carbon; Chemical, physicochemical, biochemical and biological properties; enzymes; eukaryotic cells; experimental forests; Forest; forest soils; Fundamental and applied biological sciences. Psychology; hardwood forests; Microbial; microbial activity; microbial biomass; Microbiology; mineralization; mycorrhizal fungi; Nitrification; Nitrogen; phosphates; Phosphorus; Physics, chemistry, biochemistry and biology of agricultural and forest soils; prokaryotic cells; Soil science; sorption; USA; USA, New Hampshire, Hubbard Brook Experimental Forest; Forest; Phosphorus; Microbial; Calcium; Nitrogen; Nitrification; Phosphates; Deciduous forest; Soil science; Microorganism; Microbial biomass
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2011.08.011

High rates of atmospheric nitrogen (N) deposition have raised questions about shifting patterns of nutrient limitation in northern hardwood forests. Of particular interest is the idea that increased supply of N may induce phosphorus (P) limitation of plant and microbial processes, especially in acid soils where P sorption by Al is high. In this study, we established field plots and plant-free laboratory mesocosms with P and Ca additions to test the hypotheses that 1) microbial biomass and activity are limited by P in the northern hardwood forest soils at the Hubbard Brook Experimental Forest in NH USA; 2) elevated Ca increases inherent P availability and therefore reduces any effects of added P and 3) P effects are more marked in the more carbon (C) rich Oie compared to the Oa horizon. Treatments included P addition (50 kg P ha −1), Ca addition (850 kg Ca ha −1) and Ca + P addition (850 kg Ca ha −1 and 50 kg P ha −1). The P treatments increased resin-available P levels and reduced phosphatase activity, but had no effect on microbial biomass C, microbial respiration, C metabolizing enzymes, potential net N mineralization and nitrification in the Oie or Oa horizon of either field plots or plant free mesocosms, in either the presence or absence of Ca. Total, prokaryote, and eukaryote PLFA were reduced by P addition, possibly due to reductions in mycorrhizal fungal biomass. These results suggest that increased N deposition and acidification have not created P limitation of microbial biomass and activity in these soils. ► Atmospheric N deposition may cause P limitation of forest soil microbial processes. ► P or P plus Ca had no effect on microbial parameters in the field or laboratory. ► P limitation is not likely in soils with significant pools of accessible P.