| Title: |
Acetylene reduction and 15N2 uptake rates for Alnus tenuifolia and Alnus crispa in six different successional habitats
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| Contacts: |
Ruess, Roger
Anderson, Mike
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| Abstract: |
This study sought to determine the conversion factor between acetylene reduction and N-fixation rates by root nodules excised from naturally-occurring Alnus tenuifolia and Alnus crispa plants in 18 sites in the BNZ-LTER. N-fixation rate was measured via uptake of 15N2 by excised nodule tissue. Sites were chosen to represent three replicates of early, mid, and late successional habitats on the Tanana River floodplain and in surrounding upland areas. A. tenuifolia was sampled in floodplain sites, and A. crispa in uplands. Parameters measured: acetylene reduction rate, N2 fixation rate, ratio of acetylene reduced to N2 fixed, soil temperature, leaf del 15N, and specific leaf weight.
Most of the fixed nitrogen (N) that enters the N cycle in Alaskan forests is fixed biologically by alder (Alnus spp.) in symbiosis with the N-fixing bacterial genus Frankia. Estimates of gross N inputs resulting from this process ultimately rely on accurate measurement of N-fixation by nodule tissue. These rates are typically estimated by measuring rates of acetylene reduction by nodule tissue, then using an empirically determined conversion factor to obtain the corresponding N fixation rate. The purposes of this study were to determine: 1) the conversion factor(s) for Alnus tenuifolia and Alnus crispa in the Bonanza Creek Experimental Forest, and 2) whether the conversion factor varied between plants occurring in different successional habitats.
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| Keywords: |
15N2, Acetylene reduction, actinorhizal, Alder, alnus, Alnus crispa, Alnus tenuifolia, bacteria, frankia, nitrogen fixer, plants, |
| Categories: |
Biogeochemistry
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| Study Period: |
Jun 25, 2001 to Aug 10, 2001
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| Bounding Box: |
West longitude: -148.3790685°
North latitude: 64.7666796°
East longitude: -148.1435205°
South latitude: 64.66966°
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| Site References: |
BP1 -- True balsam poplar stand on the Tanana River floodplain within Bonanza Creek Experimental Forest, Fairbanks, Alaska, USA. Vegetation structure for these sites includes a closed canopy of mature (>100 yrs old) balsam poplar with a dense thin-leaf alder (Alnus
tenuifolia) understory. Basal area for stems larger than 5 cm averages
36.7 m2 ha-1 and 1.8 m2 ha-1 for balsam poplar and alder, respectively, with densities for poplar ranging from 567 to 922 stems ha-1 among the three stands. Total litterfall averaged 279 g m-2 y-1 across the three stands during the 1998–99 growing season. Rose (Rosa acicularis) and high-bush cranberry (Viburnum edule) are prominent within the shrub layer, filling understory canopy gaps previously occupied by decadent alder shrubs. Average daily soil temperatures measured at a depth of 7 cm during the 1998 growing season ranged from a minimum of 3.8°C in May to a maximum of 11.4°C in late July. The soil, classified as typic cryofluvent, consists of an alluvium of fine to medium sand grains overlain by a well-developed organic profile extending to more than 8 cm in some places.
Soil C:N ratios average 19.0 for the organic layer and 16.0 for the mineral soil.
BP2 -- True balsam poplar stand on the Tanana River floodplain within Bonanza Creek Experimental Forest, Fairbanks, Alaska, USA. Vegetation structure for these sites includes a closed canopy of mature (>100 yrs old) balsam poplar with a dense thin-leaf alder (Alnus
tenuifolia) understory. Basal area for stems larger than 5 cm averages
36.7 m2 ha-1 and 1.8 m2 ha-1 for balsam poplar and alder, respectively, with densities for poplar ranging from 567 to 922 stems ha-1 among the three stands. Total litterfall averaged 279 g m-2 y-1 across the three stands during the 1998–99 growing season. Rose (Rosa acicularis) and high-bush cranberry (Viburnum edule) are prominent within the shrub layer, filling understory canopy gaps previously occupied by decadent alder shrubs. Average daily soil temperatures measured at a depth of 7 cm during the 1998 growing season ranged from a minimum of 3.8°C in May to a maximum of 11.4°C in late July. The soil, classified as typic cryofluvent, consists of an alluvium of fine to medium sand grains overlain by a well-developed organic profile extending to more than 8 cm in some places.
Soil C:N ratios average 19.0 for the organic layer and 16.0 for the mineral soil.
BP3 -- True balsam poplar stand on the Tanana River floodplain within Bonanza Creek Experimental Forest, Fairbanks, Alaska, USA. Vegetation structure for these sites includes a closed canopy of mature (>100 yrs old) balsam poplar with a dense thin-leaf alder (Alnus
tenuifolia) understory. Basal area for stems larger than 5 cm averages
36.7 m2 ha-1 and 1.8 m2 ha-1 for balsam poplar and alder, respectively, with densities for poplar ranging from 567 to 922 stems ha-1 among the three stands. Total litterfall averaged 279 g m-2 y-1 across the three stands during the 1998–99 growing season. Rose (Rosa acicularis) and high-bush cranberry (Viburnum edule) are prominent within the shrub layer, filling understory canopy gaps previously occupied by decadent alder shrubs. Average daily soil temperatures measured at a depth of 7 cm during the 1998 growing season ranged from a minimum of 3.8°C in May to a maximum of 11.4°C in late July. The soil, classified as typic cryofluvent, consists of an alluvium of fine to medium sand grains overlain by a well-developed organic profile extending to more than 8 cm in some places.
Soil C:N ratios average 19.0 for the organic layer and 16.0 for the mineral soil.
FP1A -- FP1A is located on a low early successional terrace (1.8 - 2 m above winter low river level) adjacent to the Tanana River. Vegetation establishment occurred in 1982 to 1983. Significant bank erosion has occurred since the establishment of the study area, resulting in loss of some study plots.
FP1B -- FP1B is located on a low early successional terrace adjacent to the Tanana River.
FP1C -- FP1C is located on a low early successional terrace adjacent to the Tanana River.
FP4A -- Mature white spruce
FP4B -- Mature white spruce
FP4C -- Mature white spruce
UP2A -- Closed Mixed White Spruce - Paper Birch Stand
UP2B -- Closed Mixed White Spruce - Paper Birch Stand
UP2C -- Closed Mixed Aspen - White Spruce Stand
UP3A -- Mature white spruce spruce stand on a south-facing slope
UP3B -- Closed White Spruce Forest
UP3C -- Closed White Spruce Forest
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| Data Columns: |
| Column |
Name |
Units |
Type |
| 1 |
Land |
|
string |
| 2 |
Species |
|
string |
| 3 |
Stage |
|
string |
| 4 |
Repsite |
|
integer |
| 5 |
PLNO |
|
integer |
| 6 |
JULDAY |
ddd |
Datetime |
| 7 |
Soiltemp |
Celsius |
float |
| 8 |
ARA |
Moles |
float |
| 9 |
PERNODN |
Percent |
float |
| 10 |
N2FIX |
gram nodule per hr |
float |
| 11 |
Ratio |
|
float |
| 12 |
DEL15N |
|
float |
| 13 |
NA SLW |
cm^2 per gram |
float |
|
| Data File(s): |
226_2060_ARA15N2_ratios.txt
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| Supplemental Files: |
|
| Metadata Formats: |
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| Public Release: |
Nov 20, 2005
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| Publications: |
Anderson, M.D., R.W. Ruess, D.D. Uliassi and J.S. Mitchell. 2004. Estimating N2 fixation in two species of Alnus in interior Alaska using acetylene reduction and 15N2 uptake. Ecoscience 11:102-112.
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The Bonanza Creek LTER, including this website, is supported by the
National Science Foundation through awards
DEB-0620579,
DEB-0423442,
DEB-0080609,
DEB-9810217,
DEB-9211769,
DEB-8702629
and by the USDA Forest Service, Pacific Northwest Research Station through agreement number RJVA-PNW-01-JV-11261952-231.
Any opinions, findings, conclusions, or recommendations expressed in the
material are those of the author(s) and do not necessarily reflect
the views of the supporting agencies or the program as a whole.
© Bonanza Creek LTER, 2009.
Last modified 23-Nov-09
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Disclaimer
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