uid=BNZ,o=lter,dc=ecoinformatics,dc=org all public read knb-lter-bnz.208.10 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 2003-10-18 Fine root processes play a prominent role in the carbon and nutrient cycling of boreal ecosystems due to the high proportion of biomass allocated belowground and the rapid decomposition of fine roots relative to aboveground tissues. To examine these issues in detail, major components of ecosystem carbon flux were studied in three mature black spruce forests in interior Alaska, where fine root production, respiration, mortality and decomposition, and aboveground production of trees, shrubs and mosses were measured relative to soil CO2 fluxes. Fine root production, measured over a 2-year period using minirhizotrons, varied from 0.004 ? 0.001 mm cm-2 d-1 over winter, to 0.051 ? 0.015 mm cm-2 d-1 during July, with peak growing season values comparable to those reported for many temperate forests using similar methods. On average, 84% of this production occurred within 20 cm of the moss surface, although the proportion occurring in deeper profiles increased as soils gradually warmed throughout the summer. Monthly rates of production and mortality were somewhat asynchronous because mortality tended to peak during fall and be minimal during periods of peak production. Production and mortality were, however, positively correlated across all tubes and time periods (r2 = 0.42, P < 0.0001). Annual fine root production averaged 2.45 ? 0.31, 8.01 ? 1.39, and 2.53 ? 0.27 mm cm-2 yr-1 among the three sites, when averaged across years. Fine root survival and decomposition were measured by tracking and analyzing the fate of individual fine roots using mark-recapture techniques. Fine root survival was greatest during periods of peak root growth, and least over winter (?time). Roots first appearing in the middle of the growing season had higher survival rates than those first appearing early or late in growing season, or over winter (?cohort), and risk of mortality decreased with root age (?age). Survival estimates translate to mean life spans of 108 ? 4 days during the growing season. While these values are in striking contrast to needle longevity and rates of aboveground litter decomposition, they are similar to many values found for temperate systems, supporting the notion that there are basic morphological and physiological traits of first-order roots that are common to most woody plant root systems. During the growing season, monthly fine root decomposition rates averaged 0.46 ? 0.01 month-1, while decomposition rates over winter averaged 0.73 ? 0.01 winter-1. These growing season estimates translate to 49 ? 2 days from the time a root was first observed as dead, to the time it disappeared. For roots that decomposed during the growing season, those with longer life spans decomposed more slowly after death. Comparing these results with other minirhizotron studies suggests that life-history traits of black spruce first-order roots are similar to those from temperate (and perhaps most) forest ecosystems. Annual production of fine roots averaged 228 ? 75 g biomass m-2 yr-1, constituting approximately 56% of total stand production. Aboveground production of trees (50 ? 14 g biomass m-2 yr-1, 13%) and shrubs (40 ? 2 g biomass m-2 yr-1, 11%) contributed similarly to total production, while mosses (73 ? 14 g biomass m-2 yr-1, 20%) accounted for the largest component of aboveground production. Soil temperature had a strong control over both soil respiration (Q10 = 2.21 ? 0.31) and root respiration (Q10 = 2.30 ? 0.37). During the growing season (15 May to 15 September), approximately 56% of soil CO2 efflux (580 ? 40 g C m-2) was derived from fine root respiration (329 ? 54 g C m-2). Although apparent rates of heterotrophic respiration (May - September) and total production did not differ, definitive estimates of net ecosystem production are impossible given the potentially large, unmeasured components of NPP, such as root exudation and mycorrhizal production. Nevertheless, rates of fine root production, mortality, and decomposition indicate that in these black spruce ecosystems, fine roots are much more dynamic than would be predicted from patterns of aboveground processes, and that carbon, and presumably nutrients, are cycling through fine roots at rates several orders of magnitude faster than through aboveground tissues. soil respiration Biogeochemistry

While metadata will be freely available to those requesting it, the data manager will assure that any restrictions on access to data sets in the database will be enforced. Data will not be released without proper permission first being obtained from the investigator who generated the data.

Researchers should receive adequate acknowledgment for the use of their data by others and should be provided with copies of publications using their data. Users of data from the data base must be aware that data is not to be sold or redistributed.

It is considered a matter of professional ethics to acknowledge the work of other scientists. Thus, the Data User will properly cite the Data Set in any publications or in the metadata of any derived data products that were produced using the Data Set.

http://www.lter.uaf.edu/data_detail.cfm?datafile_pkey=208 Site information unavailable -148.2640747 -148.1426888 64.7241989 64.68195711 1998-06-10 1999-08-18

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

Soil respiration (?mol CO2 m-2 s-1) was measured throughout the growing season at all sites during 1998 and 1999 using a LICOR 6000-09 Soil Respiration System (LICOR, Lincoln, NE). Ten sampling locations were randomly located at each site and marked with lathe stakes at the beginning of each season. During sampling periods (5 times each growing season), an undisturbed location was randomly selected within 2 m of each stake and the top layer of live moss was carefully removed immediately prior to soil respiration measurements to eliminate the influences of either moss photosynthesis or respiration on fluxes. This method has been employed previously (Schlentner and Van Cleve 1985) and recently shown to be effective in eliminating moss influences (O’Connell et al. (A), in press). Due to the density of fine root growth within the upper fibric surface soil layers, we elected not to install soil rings for the LICOR-6009 chamber. For each measurement, the LICOR-6009 chamber was inserted 1.3 cm into the dead moss layer, and CO2 was drawn down 40 ?mol mol-1 below ambient and allowed to increase 10 ?mol mol-1 prior to logging 4 flux measurements as determined by a 10 ?mol mol-1 change in CO2 within the chamber. The flux reading taken closest to ambient CO2 concentration was that used in analyses. Soil temperature was recorded at the time of measurement using the LICOR temperature probe positioned to 6 cm below the lower limit of live moss, within the humic layer. Seasonal relationships between the soil respiration and temperature were generated by non-linear regression, as described above, by combining data across sampling dates and sites, using the mean of the ten sampling stations from each of the 3 sites at each time period. We scaled instantaneous measurements (?g CO2-C m-2 s-1) to estimates of growing season efflux (15 May – 15 September) by summing daily respiration estimates predicted from the non-linear relationship using daily soil temperature means measured for each site. The relationship between soil respiration and soil temperature did not differ among sites or between years (see below); therefore, one exponential relationship was generated using data from all sites and both years. Seasonal soil temperature data from each site was then used with this equation to estimate seasonal soil CO2 efflux for each site.

geoReference 1998-06-10 1999-08-18

2-year sampling

208_BS_Soil_Respiration_1998_1999.csv 208_BS_Soil_Respiration_1998_1999.csv 1 \n \n column , http://metacat.lternet.edu/das/dataAccessServlet?docid=knb-lter-bnz..&urlTail=/ascii/files/208_BS_Soil_Respiration_1998_1999.csv Site Site Site Id string Site Id Date Date Date of sample string mm/dd/yyyy Year Year Year of Sample integer yyyy Month Month Month string WWW Day Day Day of year integer dd Plot Plot Plot ID integer Plot ID Respiration Respiration Respiration value float molCO2m-2s-1 real Soil Temp Soil Temp Soil Temperature float celsius real JULDAY JULDAY JULDAY string JULDAY