Ecosystem controls on nitrogen fixation in boreal feather moss communities |
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Authors: | Thomas H DeLuca Olle Zackrisson Francesco Gentili Anita Sellstedt Marie-Charlotte Nilsson |
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Institution: | (1) Ecology and Economics Research Department (EERD), The Wilderness Society, Washington, D.C., USA;(2) Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, Umea, Sweden;(3) Department of Plant Physiology, Umea University, Umea, Sweden |
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Abstract: | N fixation in feather moss carpets is maximized in late secondary successional boreal forests; however, there is limited understanding
of the ecosystem factors that drive cyanobacterial N fixation in feather mosses with successional stage. We conducted a reciprocal
transplant experiment to assess factors in both early and late succession that control N fixation in feather moss carpets
dominated by Pleurozium schreberi. In 2003, intact microplots of moss carpets (30 cm × 30 cm × 10–20 cm deep) were excavated from three early secondary successional
(41–101 years since last fire) forest sites and either replanted within the same stand or transplanted into one of three late
successional (241–356 years since last fire) forest sites and the transverse was done for late successional layers of moss.
Moss plots were monitored for changes in N-fixation rates by acetylene reduction (June 2003–September 2005) and changes in
the presence of cyanobacteria on moss shoots by microscopy (2004). Forest nutrient status was measured using ionic resin capsules
buried in the humus layer. Late successional forests exhibit high rates of N fixation and consistently high numbers of cyanobacteria
on moss shoots, but low levels of available N. Conversely, early successional forests have higher N availability and have
low rates of N fixation and limited presence of cyanobacteria on moss shoots. Transplantation of moss carpets resulted in
a significant shift in presence and activity of cyanobacteria 1 year after initiation of the experiment responding to N fertility
differences in early versus late successional forests. |
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Keywords: | Pleurozium schreberi Nitrogen fixation Reciprocal transplant |
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