Evidence that Northern Pioneering Pines with Tuberculate Mycorrhizae are Unaffected by Varying Soil Nitrogen LevelsReport as inadecuate




Evidence that Northern Pioneering Pines with Tuberculate Mycorrhizae are Unaffected by Varying Soil Nitrogen Levels - Download this document for free, or read online. Document in PDF available to download.

Microbial Ecology

, Volume 64, Issue 4, pp 964–972

First Online: 08 June 2012Received: 04 May 2012Accepted: 24 May 2012

Abstract

Tuberculate mycorrhizae on Pinus contorta lodgepole pine have previously been shown to reduce acetylene, but an outstanding question has been to what degree these structures could meet the nitrogen requirements of the tree. We compared the growth, tissue nitrogen contents, and stable nitrogen isotope ratios of P. contorta growing in gravel pits to the same species growing on adjacent intact soil. Trees growing in severely nitrogen deficient gravel pits had virtually identical growth rates and tissue nitrogen contents to those growing on intact soil that had nitrogen levels typical for the area. δN values for trees in the gravel pits were substantially lower than δN values for trees on intact soil, and isotope ratios in vegetation were lower than the isotope ratios of the soil. The form of soil nitrogen in the gravel pits was almost exclusively nitrate, while ammonium predominated in the intact soil. Discrimination against N during plant uptake of soil nitrate in the highly N-deficient soil should be weak or nonexistent. Therefore, the low δN in the gravel pit trees suggests that trees growing in gravel pits were using another nitrogen source in addition to the soil. Precipitation-borne nitrogen in the study area is extremely low. In conjunction with our other work, these findings strongly suggests that P. contorta and its microbial symbionts or associates fix nitrogen in sufficient amounts to sustain vigorous tree growth on the most nitrogen-deficient soils.

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Author: William Kenneth Chapman - Leslie Paul

Source: https://link.springer.com/







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