uid=BNZ,o=lter,dc=ecoinformatics,dc=org all public read knb-lter-bnz.50.10 Roger W. Ruess

Institute of Arctic Biology University of Alaska Fairbanks P.O. Box 757000 Fairbanks AK 99775-0180 United States

(907) 474-7153 (907) 474-6967 rwruess@alaska.edu http://www.iab.uaf.edu/~roger_ruess/ Bonanza Creek LTER Data Manager

Boreal Ecology Cooperative Research Unit University of Alaska Fairbanks P.O. Box 756780 Fairbanks AK 99775 USA

907-474-6364 907-474-6251 jpdowning@alaska.edu http://www.lter.uaf.edu Mike D Anderson (651) 696-6230 (651) 696-6443 Associated investigator 2005-11-20 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. acetylene reduction 15N2 Alnus tenuifolia Alnus crispa alder nitrogen fixer actinorhizal alnus frankia plants bacteria Biogeochemistry

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http://www.lter.uaf.edu/data_detail.cfm?datafile_pkey=50 Site information unavailable -148.3790685 -148.1435205 64.7666796 64.66966 2001-06-25 2001-08-10

Completed

Bonanza Creek LTER Data Manager

Boreal Ecology Cooperative Research Unit University of Alaska Fairbanks P.O. Box 756780 Fairbanks AK 99775 USA

907-474-6364 907-474-6251 jpdowning@alaska.edu http://www.lter.uaf.edu Bonanza Creek LTER

Boreal Ecology Cooperative Research Unit University of Alaska Fairbanks P.O. Box 756780 Fairbanks AK 99775 USA

907-474-6364 907-474-6251 Bonanza Creek LTER

At each site 10 alder plants were chosen haphazardly. Approximately 5 grams of nodule tissue was harvested from each plant, half of which was exposed to acetylene for 2.5 minutes, and half to 15N2 for 10 minutes. A sample of the 15N2 composition of the incubation atmosphere was also taken. Additionally, at each plant soil temperature was measured at a depth corresponding to that at which most nodules occurred, and five leaves were chosen for measurement of specific leaf weight and del 15N. Ethylene production resulting from acetylene reduction by nodules was quantified via gas chromatography. Nodule 15N2 uptake, incubation atmosphere composition, and leaf del 15N were measured via mass spectrometry. Data were entered and double-checked by Mike Anderson. ARA conversion factors for each plant were calculated by dividing the acetylene reduction rate by the rate of N-fixation calculated from 15N2 uptake. 15N2 uptake was converted to an estimate of N-fixation rate by correcting for the 15N2 composition of the incubation atmosphere. Specific leaf weight was obtained by dividing the total area of circular punches taken from leaves by the dry mass of the punches. Leaf del 15N was obtained via mass spectrometry.

geoReference 2001-06-25 2001-08-10

Daily, 1 site (10 plants) per day

226_2060_ARA15N2_ratios.txt Acetylene reduction values, 15N2 uptake rates, leaf del 15N, and specific leaf weights from Alnus tenuifolia in early, mid, and late succession on the Tanana floodplain and A. crispa in early, mid, and late succession in the surrounding uplands. 226_2060_ARA15N2_ratios.txt 2 \n \n column \t http://metacat.lternet.edu/das/dataAccessServlet?docid=knb-lter-bnz..&urlTail=/ascii/files/226_2060_ARA15N2_ratios.txt Land Land Upland or Floodplain site string UP Upland FP Floodplain Species Species Species Code string AC A. crispa AT A. tenuifolia Stage Stage Successional stage string Successional stage Repsite Repsite Replicate site; 3 sites/stage/landscape integer Replicate site; 3 sites/stage/landscape PLNO PLNO Plant number, 1-90 for each species integer Plant number, 1-90 for each species JULDAY JULDAY Julian day of sampling integer ddd Soiltemp Soiltemp Soil temperature at sample degrees Celsius float celsius real ARA ARA Acetylene reduction rate mol float Moles real PERNODN PERNODN Nodule percent nitrogen by mass proportion float dimensionless real N2FIX N2FIX Nitrogen fixation rate from 15N uptake assay mol N2 fixed per gram nodule per hr float gramnoduleperhr real Ratio Ratio RATIO of Acetylene reduction rate/Nitrogen fixation rate float dimensionless real DEL15N DEL15N Leaf del 15N value float dimensionless real NA SLW NA SLW Specific leaf weight cm^2 per gram float cm^2pergram real