Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions
If increases in net primary productivity (NPP) caused by rising concentrations of atmospheric CO<sub>2</sub> (<i>C</i><sub>a</sub>) are to be sustained, key N processes such as soil mineralization, biological fixation, root uptake and nutrient conservation must al...
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2013-11-01
|
| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/10/7703/2013/bg-10-7703-2013.pdf |
| _version_ | 1830483370532929536 |
|---|---|
| author | R. F. Grant |
| author_facet | R. F. Grant |
| author_sort | R. F. Grant |
| collection | DOAJ |
| description | If increases in net primary productivity (NPP) caused by rising
concentrations of atmospheric CO<sub>2</sub> (<i>C</i><sub>a</sub>) are to be sustained, key N
processes such as soil mineralization, biological fixation, root uptake and
nutrient conservation must also be increased. Simulating the response of
these processes to elevated <i>C</i><sub>a</sub> is therefore vital for models used to
project the effects of rising <i>C</i><sub>a</sub> on NPP. In this modelling study,
hypotheses are proposed for changes in soil mineralization, biological
fixation, root nutrient uptake and plant nutrient conservation with changes
in <i>C</i><sub>a</sub>. Algorithms developed from these hypotheses were tested in the
ecosystem model <i>ecosys</i> against changes in N and C cycling measured over several
years under ambient vs. elevated <i>C</i><sub>a</sub> in Free Air CO<sub>2</sub> Enrichment
(FACE) experiments in the USA at the Duke Forest in North Carolina, the Oak Ridge
National Laboratory forest in Tennessee, and the USDA research forest in
Wisconsin. More rapid soil N mineralization was found to be vital for
simulating sustained increases in NPP measured under elevated vs. ambient
<i>C</i><sub>a</sub> at all three FACE sites. This simulation was accomplished by priming
decomposition of N-rich humus from increases in microbial biomass generated
by increased litterfall modelled under elevated <i>C</i><sub>a</sub>. Greater nonsymbiotic
N<sub>2</sub> fixation from increased litterfall, root N uptake from increased
root growth, and plant N conservation from increased translocation under
elevated <i>C</i><sub>a</sub> were found to make smaller contributions to simulated
increases in NPP. However greater nutrient conservation enabled larger
increases in NPP with <i>C</i><sub>a</sub> to be modelled with coniferous vs. deciduous
plant functional types. The effects of these processes on productivity now
need to be examined over longer periods under transient rises in <i>C</i><sub>a</sub> and
a greater range of site conditions. |
| first_indexed | 2024-12-21T17:49:57Z |
| format | Article |
| id | doaj.art-a20a50b83b5c4a3d9221cda77c6890e2 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-21T17:49:57Z |
| publishDate | 2013-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-a20a50b83b5c4a3d9221cda77c6890e22022-12-21T18:55:22ZengCopernicus PublicationsBiogeosciences1726-41701726-41892013-11-0110117703772110.5194/bg-10-7703-2013Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditionsR. F. Grant0Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, CanadaIf increases in net primary productivity (NPP) caused by rising concentrations of atmospheric CO<sub>2</sub> (<i>C</i><sub>a</sub>) are to be sustained, key N processes such as soil mineralization, biological fixation, root uptake and nutrient conservation must also be increased. Simulating the response of these processes to elevated <i>C</i><sub>a</sub> is therefore vital for models used to project the effects of rising <i>C</i><sub>a</sub> on NPP. In this modelling study, hypotheses are proposed for changes in soil mineralization, biological fixation, root nutrient uptake and plant nutrient conservation with changes in <i>C</i><sub>a</sub>. Algorithms developed from these hypotheses were tested in the ecosystem model <i>ecosys</i> against changes in N and C cycling measured over several years under ambient vs. elevated <i>C</i><sub>a</sub> in Free Air CO<sub>2</sub> Enrichment (FACE) experiments in the USA at the Duke Forest in North Carolina, the Oak Ridge National Laboratory forest in Tennessee, and the USDA research forest in Wisconsin. More rapid soil N mineralization was found to be vital for simulating sustained increases in NPP measured under elevated vs. ambient <i>C</i><sub>a</sub> at all three FACE sites. This simulation was accomplished by priming decomposition of N-rich humus from increases in microbial biomass generated by increased litterfall modelled under elevated <i>C</i><sub>a</sub>. Greater nonsymbiotic N<sub>2</sub> fixation from increased litterfall, root N uptake from increased root growth, and plant N conservation from increased translocation under elevated <i>C</i><sub>a</sub> were found to make smaller contributions to simulated increases in NPP. However greater nutrient conservation enabled larger increases in NPP with <i>C</i><sub>a</sub> to be modelled with coniferous vs. deciduous plant functional types. The effects of these processes on productivity now need to be examined over longer periods under transient rises in <i>C</i><sub>a</sub> and a greater range of site conditions.http://www.biogeosciences.net/10/7703/2013/bg-10-7703-2013.pdf |
| spellingShingle | R. F. Grant Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions Biogeosciences |
| title | Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions |
| title_full | Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions |
| title_fullStr | Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions |
| title_full_unstemmed | Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions |
| title_short | Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO<sub>2</sub> and contrasting site conditions |
| title_sort | modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric co sub 2 sub and contrasting site conditions |
| url | http://www.biogeosciences.net/10/7703/2013/bg-10-7703-2013.pdf |
| work_keys_str_mv | AT rfgrant modellingchangesinnitrogencyclingtosustainincreasesinforestproductivityunderelevatedatmosphericcosub2subandcontrastingsiteconditions |