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Long-term effects of nitrogen (N) additions on boreal forest

From, Fredrik (2016). Long-term effects of nitrogen (N) additions on boreal forest. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2016:89
ISBN 978-91-576-8680-0
eISBN 978-91-576-8681-7
[Doctoral thesis]

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The studies presented in this thesis aim to increase our understanding of the long-term effects of anthropogenic nitrogen (N) input via fertilization or atmospheric N deposition on tree growth and forest understory in boreal forest.

Firstly, I studied the effects of low annual N addition simulating atmospheric N deposition on tree growth and variables linked to site fertility in two different forest ecosystems, i.e. on one Norway spruce (Picea abies [L.] H. Karst.) dominated site and on one Scots pine (Pinus sylvestris L.) dominated site (Paper I and II). On the P. abies dominated site tree growth and needle N concentration were higher on plots treated with 12.5 and 50 kg N ha⁻¹ year⁻¹ than on control plots, which only received background N deposition (1 to 2 kg N ha⁻¹ year⁻¹). P. abies growth increased linearly with 1.2% for every kg of N added, which corresponded to a net tree carbon (C) sequestration of approximately 19 kg C per kg N (Paper II). On the P. sylvestris dominated site tree growth increased linearly with 1.6% per kg N added.

Secondly, I studied carry-over effects of forest fertilization (150 kg N ha⁻¹) between tree generations. Growth of 10 years old trees on sites fertilized during the previous tree generation was measured (Paper III). On sites that were previously fertilized twice (25 and 33 years prior to my study), the young P. abies and P. sylvestris trees were on average 24% taller than trees on sites that had never been fertilized. Furthermore, the soil N mineralization rates were nearly four times higher and the amount of plant available soil-N two times higher on sites that were previously fertilized twice than on the other sites.

Thirdly, I studied the interaction effects between N form and N dose on tree growth, mycorrhizal fungi and on forest floor vegetation in a c. 50 year old pine forest (Paper IV). Five years after adding 50 and 150 kg N ha⁻¹ tree growth responded similarly on plots treated with the amino acid arginine (ARG) and on plots treated with ammonium-nitrate (AN). The basal area growth was c. 40% higher on the N addition plots than on control plots. The abundance of sporocarps (fruit bodies) of mycorrhizal fungi was significantly reduced in AN treated plots compared to ARG treated plots and the control. Both ARG and AN affected the forest floor vegetation, there was rapid increase of wavy hair-grass (Avenella flexuosa [L.] Parl.) following N addition, which remained throughout the study period. Also, at the end of the study period there was a decrease in lingonberry shrub (Vaccinium vitis-idaea L.) abundance on N treated plots.

In conclusion, I found linear relationships between N addition, up to 50 kg N ha⁻¹ year⁻¹, and P. abies and P. sylvestris growth. Also, I present data suggesting that the mechanisms affecting tree growth, on an ecosystem level, can be changed in the long-term by repeated N fertilization with 150 kg N ha⁻¹ occasion⁻¹. That is, N addition can promote a positive long-term effect on an ecosystem’s nutritional status. In addition, I show that inorganic and organic N additions to a forest ecosystem after five years have rather similar effects on tree growth and understory vegetation, whereas organic N addition has significantly less negative effects on sporocarp production of mycorrhizal fungi than inorganic N addition.

Authors/Creators:From, Fredrik
Title:Long-term effects of nitrogen (N) additions on boreal forest
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2016
Depositing date:9 November 2016
Number of Pages:65
IFrom, F., Lundmark, T., Mörling, T., Pommerening, A., Nordin, A. (2016). Effects of simulated long-term N deposition on Picea abies and Pinus sylvestris growth in boreal forest. Canadian Journal of Forest Research. DOI: 10.1139/cjfr-2016-0201.
IIGundale, M.J., From, F., Bach, L.H., Nordin, A. (2014). Anthropogenic nitrogen deposition in boreal forests has a minor impact on the global carbon cycle. Global Change Biology, 20(1), pp. 276-286. DOI: 10.1111/gcb.12422
IIIFrom, F., Strengbom, J., Nordin, A. (2015). Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest. Forests, 6(4), pp. 1145-1156. DOI: 10.3390/f6041145.
IVHedwall, P-O., Gruffman, L., Ishida, T., From, F., Lundmark, T., Näsholm, T., Nordin, A. (2016). Interplay between N-form and N-dose influences ecosystem effects of N addition to boreal forest. (Manuscript).
Place of Publication:Umeå
Publisher:Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8680-0
ISBN for electronic version:978-91-576-8681-7
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F04 Fertilizing
K Forestry > K10 Forestry production
P Natural resources > P35 Soil fertility
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Forest Science
Agrovoc terms:boreal forests, nitrogen, fertilizer application, arginine, forest soils, picea abies, pinus sylvestris, forest trees, growth, nitrogen cycle, carbon sequestration, models, sweden
Keywords:Annual nitrogen (N) addition, N deposition, Arginine, Carbon (C) sequestration, N fertilization, Forest growth, N turnover
Permanent URL:
ID Code:13838
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Genetics and Plant Physiology
External funders:Future Forests
Deposited By: Mr. Fredrik K. J. From
Deposited On:11 Nov 2016 06:54
Metadata Last Modified:10 Sep 2020 13:41

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