Cyanolichens: a link between the phosphorus and nitrogen cycles in a Hawaiian montane forest. Benner, J. W. & Vitousek, P. M. Journal of Tropical Ecology, 28(1):73–81, January, 2012.
Cyanolichens: a link between the phosphorus and nitrogen cycles in a Hawaiian montane forest [link]Paper  doi  abstract   bibtex   
Abstract: Low phosphorus (P) supply frequently has been shown to limit the abundance and activity of nitrogen (N)-fixing organisms, potentially constraining N inputs to ecosystems. Previous research in a montane Hawaiian forest has shown that ground-level P-fertilization led to significant increases in the population size of epiphytic N-fixing lichens (cyanolichens), as well as a shift in community composition from crustose to leafy species. In this study, we ask whether these changes in the cyanolichen community have resulted in increased N inputs to the forest, and also whether the very high levels of P in the canopy of P-fertilized forest stimulate individual lichen fixation rates over those of lichens from a nearby unfertilized reference forest. We used acetylene reduction (AR) assays to measure the fixation rates of 14 cyanolichen species from P-fertilized forest, and calibrated these rates by measuring 15 N 2 fixation incorporation in four species. We found that the ratio of acetylene reduced to N fixed ranged from 2.4 ± 0.4 in Pseudocyphellaria crocata to 9.3 ± 2.4 in Leptogium denticulatum . Nitrogen fixation rates in the P-fertilized forest ranged from 0.64 ± 0.05 nmol N cm −2 h −1 in Nephroma helveticum to 3.97 ± 1.48 nmol N cm −2 h −1 in Parmeliella nigrocincta . Fixation rates did not vary greatly among species from P-fertilized forest. We compared these P-fertilized rates to those of 10 species from the reference forest, and found that mass-based fixation rates of P-fertilized lichens were not greater than those of lichens from the unfertilized forest. Using the measured AR rates, we estimate that the P additions increase cyanolichen N inputs to the forest 30-fold, from ~0.3 kg N ha −1 y −1 to ~9 kg N ha −1 y −1 . These results suggest that P additions to this ecosystem increase N inputs primarily by increasing the abundance of cyanolichens, and that shifts in cyanolichen community composition and changes in individual fixation rate were of lesser importance in determining ecosystem N inputs.
@article{benner_cyanolichens_2012,
	title = {Cyanolichens: a link between the phosphorus and nitrogen cycles in a {Hawaiian} montane forest},
	volume = {28},
	copyright = {https://www.cambridge.org/core/terms},
	issn = {0266-4674, 1469-7831},
	shorttitle = {Cyanolichens},
	url = {https://www.cambridge.org/core/product/identifier/S0266467411000605/type/journal_article},
	doi = {10.1017/S0266467411000605},
	abstract = {Abstract:
            
              Low phosphorus (P) supply frequently has been shown to limit the abundance and activity of nitrogen (N)-fixing organisms, potentially constraining N inputs to ecosystems. Previous research in a montane Hawaiian forest has shown that ground-level P-fertilization led to significant increases in the population size of epiphytic N-fixing lichens (cyanolichens), as well as a shift in community composition from crustose to leafy species. In this study, we ask whether these changes in the cyanolichen community have resulted in increased N inputs to the forest, and also whether the very high levels of P in the canopy of P-fertilized forest stimulate individual lichen fixation rates over those of lichens from a nearby unfertilized reference forest. We used acetylene reduction (AR) assays to measure the fixation rates of 14 cyanolichen species from P-fertilized forest, and calibrated these rates by measuring
              15
              N
              2
              fixation incorporation in four species. We found that the ratio of acetylene reduced to N fixed ranged from 2.4 ± 0.4 in
              Pseudocyphellaria crocata
              to 9.3 ± 2.4 in
              Leptogium denticulatum
              . Nitrogen fixation rates in the P-fertilized forest ranged from 0.64 ± 0.05 nmol N cm
              −2
              h
              −1
              in
              Nephroma helveticum
              to 3.97 ± 1.48 nmol N cm
              −2
              h
              −1
              in
              Parmeliella nigrocincta
              . Fixation rates did not vary greatly among species from P-fertilized forest. We compared these P-fertilized rates to those of 10 species from the reference forest, and found that mass-based fixation rates of P-fertilized lichens were not greater than those of lichens from the unfertilized forest. Using the measured AR rates, we estimate that the P additions increase cyanolichen N inputs to the forest 30-fold, from {\textasciitilde}0.3 kg N ha
              −1
              y
              −1
              to {\textasciitilde}9 kg N ha
              −1
              y
              −1
              . These results suggest that P additions to this ecosystem increase N inputs primarily by increasing the abundance of cyanolichens, and that shifts in cyanolichen community composition and changes in individual fixation rate were of lesser importance in determining ecosystem N inputs.},
	language = {en},
	number = {1},
	urldate = {2025-07-10},
	journal = {Journal of Tropical Ecology},
	author = {Benner, Jon W. and Vitousek, Peter M.},
	month = jan,
	year = {2012},
	pages = {73--81},
}
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