C and N availability affects the 15N natural abundance of the soil microbial biomass across a cattle manure gradient

European Journal of Soil Science - Tập 57 Số 4 - Trang 468-475 - 2006
Paul Dijkstra1, O. V. Menyailo1,2, Richard R. Doucett3, Stephen C. Hart4,5, Egbert Schwartz1, Bruce A. Hungate1,4
1Department of Biological Sciences, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA,
2Institute of Forest SB RAS, Krasnoyarsk, 660036, Russia
3Colorado Plateau Stable Isotope Laboratory, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA,
4Merriam-Powell Center for Environmental Research, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA
5School of Forestry, Northern Arizona University, PO Box 15018, Flagstaff, AZ 86011, USA, and

Tóm tắt

SummaryThe availability of C and N to the soil microbial biomass is an important determinant of the rates of soil N transformations. Here, we present evidence that changes in C and N availability affect the 15N natural abundance of the microbial biomass relative to other soil N pools. We analysed the 15N natural abundance signature of the chloroform‐labile, extractable, NO3–, NH4+ and soil total N pools across a cattle manure gradient associated with a water reservoir in semiarid, high‐desert grassland. High levels of C and N in soil total, extractable, NO3–, NH4+ and chloroform‐labile fractions were found close to the reservoir. The δ15N value of chloroform‐labile N was similar to that of extractable (organic + inorganic) N and NO3– at greater C availability close to the reservoir, but was 15N‐enriched relative to these N‐pools at lesser C availability farther away. Possible mechanisms for this variable 15N‐enrichment include isotope fractionation during N assimilation and dissimilation, and changes in substrate use from a less to a more 15N‐enriched substrate with decreasing C availability.

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Thông tin xuất bản

European Journal of Soil Science

Tập 57 Số 4

468-475

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