The BNZ LTER maintains an extensive program for monitoring climate, biota, and physical processes at long-term research sites across interior Alaska (Table 1). Many of these data sets predate the establishment of the BNZ LTER in 1987. All data are archived online and can be retrieved through the searchable BNZ Data Catalog. In addition to our local data catalog, we also publish our data to larger data repositories, most notably the Environmental Data Initiative (EDI), where climate data are most accessible to the research community.The BNZ LTER monitoring program is the responsibility of the Site Management team, led by Jamie Hollingsworth (Site Manager) and Karl Olson (Lead Technician), but individual PIs and the Information Manager work closely with the team to assist with data collection, processing, and archiving.
Data are collected at long-term sites within the Bonanza Creek Experimental Forest (BCEF), the Caribou-Poker Creek Research Watersheds (CPCRW), the Regional Site Network (RSN), the Eight Mile Lake area (EML), and at long-term experiments such as the Alaska Peatland Experiment (APEX). Detailed information are provided online for these BNZ Research Areas, and for locations/interactive maps of individual BNZ Study Sites. In addition, hundreds of other locations throughout interior Alaska have/are being monitored for numerous other parameters, and are described within individual data files.
A brief overview of the main components of the monitoring program are listed below Table 1, while detailed methods can be found within the metadata descriptions listed for individual data sets.
Table 1. Parameters measured by BNZ LTER monitoring program.
|Air & Soil temperature||BCEF, CPCRW||1984-||Hollingsworth & Olson1|
|RH & Evaporation||BCEF, CPCRW||1984-||Hollingsworth & Olson1|
|Precipitation||BCEF, CPCRW||1984-||Hollingsworth & Olson1|
|Wind speed & direction||BCEF, CPCRW||1984-||Hollingsworth & Olson1|
|Solar radiation (global)||BCEF, CPCRW||1984-||Hollingsworth & Olson1|
|UV, PAR||BCEF, CPCRW||1984-||Hollingsworth & Olson1|
|Short & Long wave in/out||CPCRW||1988-||Hollingsworth & Olson1|
|Sun photometer||BCEF,||1994-||Hollingsworth & Olson1|
|Snow depth||BCEF, EML, CPCRW||1968-||Hollingsworth & Olson1|
|Thaw depth||BCEF, EML, CPCRW||1992-||Hollingsworth & Olson1|
|Snow water equivalents||BCEF, CPCRW||1983-||Hollingsworth & Olson1|
|Permafrost temperature||BCEF, EML, CPCRW2||1980-||Romanovsky, Schuur|
|Vegetation, Insects, Pathogens, and Herbivores||
|Tree density, biomass||RSN, BCEF||1989-||T. Hollingsworth, Ruess|
|Tree seedling density||RSN, BCEF||1989-||T. Hollingsworth, Juday|
|Understory cover, biomass||RSN, BCEF||1989-||T. Hollingsworth|
|Insect defoliators||BCEF||1976-||Wagner, Juday|
|Aspen and alder canker||BCEF2||2005-||Ruess, Winton|
|Snowshoe hare populations||BCEF||1999-||Kielland|
|Carbon and nutrient stocks||
|Trees||RSN, BCEF||1989-||Mack, Ruess|
|Soils||RSN, BCEF||1989-||Turetsky, Mack|
|Soil respiration||BCEF, CPCRW||*||Ruess, Valentine|
|N mineralization||BCEF, CPCRW||*||Kielland|
|Nitrogen deposition (NADP)||CPCRW||1993-||Jones|
|Litterfall||RSN, BCEF||1975-||Ruess, Mack|
|Browse consumption||RSN, BCEF||*||Kielland|
|Net Ecosystem Exchange||RSN||2015-||Euskirchen|
1Jamie Hollingsworth (site manager) and Karl Olson (technician) are responsible for the climate monitoring program
2Monitoring network includes sites throughout interior Alaska
*Several parameters have been monitored periodically
Climate:BNZ LTER maintains Level 1 climate stations within BCEF (LTER1 = uplands; LTER2 = floodplain) and CPCRW (CRREL) that stream real-time climate data. Current weather at these sites and detailed information regarding instrumentation can be found online. In addition, Level 2 climate stations are maintained at the "A" floodplain ("FP") and upland ("UP") research sites with BCEF. We also maintain an NADP monitoring station located in CPCRW.Current and historical climate data for all of these sites can be visualized and downloaded through the interactive BNZ Meteorological Data Vision Network portal: (http://bnznet.iab.uaf.edu/vdv/). The BNZ LTER Site Management team is in the process of relocating the "FP" and "UP" climate stations to sites within the Regional Site Network.
Permafrost: Annual thaw depths are measured at the time of maximum thaw at all long-term vegetation sites that have permafrost, as well at several sites within the region where thaw depth monitoring began in the early 1970s, such as the Wickersham Fireline Sites.Snow addition experiments at EML have been monitoring thaw depth and permafrost temperatures since the early 2000s.BNZ LTER also collaborates with the UAF Geophysical Institute Permafrost Laboratory, who maintains a network of sites where permafrost temperature up to 75m in depth is being monitored continuously.
Vegetation and ANPP: Long-term changes in vascular and non-vascular species composition are monitored within one 50 X 60 m plot at all sites within BCEF, CPCRW and the RSN.Each plot is gridded into 35 10 X 10 m subplots identified with numbered corner stakes, whereby the interior 12 sub-plots are used for monitoring trees (individuals with a diameter > 2.5 cm at 1.27m), with perimeter subplots serving as a buffer.All trees within these 12 interior plots are individually tagged, measured, and characterized (live, dead, leaning, topped, down, etc.) to enable for the determination of recruitment, growth, and mortality over time. The number and size of shrubs (>1m), tree seedlings/saplings (<2.5 cm at 1.37 m) are monitored within a 2 m strip extending along the outside edge of two sides of the 50 X 60 m plot. From 1989 to 2007, species cover was visually estimated as % cover in 1 m2 plots nested within each of the 12 interior subplots. In 2007 we transitioned to the point bar method as a more objective method of assessing vegetation cover. A laser is used to measure the intercept of vegetation cover at each point along two ten point transects; one transect per diagonal of the 1 m2 plot. Additionally, we record the height of each intercept to measure vegetation structure.
The protocol, layout, numbering system for these long-term vegetation plots can be found here (Research Site Installation Methods).Full vegetation inventories are conducted every 3-10 years depending on stand age.Litterfall mass by species and snowshoe hare pellet counts are monitored using 6 1m 2 litter trays/site from sites within BCEF and CPCRW; beginning in 2015, locations for litterfall collection were moved to core sites within the RSN.Seedfall monitoring includes seed counts and germination rates of trees (P. glauca, P. mariana, B. neoalaskana, L. laricina) and shrubs (A. viridis and A. tenuifolia) from 0.25 m2 seed trays emptied annually from selected sites within BCEF and CPCRW. We also maintain tree-bands on 10-20 individual trees of dominant species at each of 9 floodplain and 6 upland sites in order to assess annual diameter increment growth across the successional sequence.All vegetation data are online and can be converted to biomass and AGNPP metrics using published allometric equations (Yarie et al. 2007).
Insects and Pathogens: Aspen foliar herbivory and densities of the aspen leaf miner (Phyllocnistis populiella) are surveyed annually at BNZ LTER and multiple additional sites near Fairbanks. Foliar herbivory of willow species is monitored annually as part of an experiment established in 2012 along the Tanana River to study the independent and interactive effects of insect herbivory and mammalian browsing. BNZ LTER established a network of sites for monitoring a fungal stem canker (Valsa melanodiscus) in thin-leaf alder (Alnus tenuifolia) in 2005 with sites in Fairbanks, Eagle River, and on the Kenai Peninsula.In 2015, we initiated a monitoring program for an as yet to be identified fungal stem canker in aspen (Populus tremuloides), with 88 site scattered across 8 ecoregions of interior Alaska.
Snowshoe Hares: Snowshoe hare population abundance and density are being measured twice a year, in May-June to estimate end-of-winter densities and in Aug-Sep to estimate finite population growth over the summer. The population estimates are monitored in conjunction with other snowshoe hare population estimates by federal agencies based on pellet and road counts elsewhere within the state (Tetlin NWR, Denali NPP, Gates of the Arctic NPP). Snowshoe hare populations are currently on the rise across the Interior with densities of 2-4 hares/ha depending on location. BNZ investigators are also monitoring movements of ~70 GPS-collared lynx across the state in collaborations with the Fish & Wildlife Service and the National Park Service.
Stream Discharge and Chemistry: Stream discharge is measured in 3 streams draining sub-catchments of the CPCRW with catchment areas of 5.2 km2 (C2), 5.7 km2 (C3), and 10.0 km2 (C4), and underlying permafrost extents of 3, 53 and 19%, respectively. Parshall flumes were installed in the C2, C3, and C4 sub-catchments in 1977, 1978, and 1979, respectively, with stage measurements recorded at regular intervals ranging from 15 to 60 minutes. Flow rate through flumes is determined by regular manual measurement of stream discharge and the development of rating curves, which are used to generate a continuous discharge record. Spring snowmelt is usually the major hydrological event of the year. However, discharge measurements during this period are difficult to obtain due to extensive aufeis (icing) formations at the gauging stations, which often disperse the flow outside the main stream channel. Stream water is collected daily from five sub-catchments (C1, C2, C3, C4 and P6) using autosamplers.Samples in autosamplers are collected biweekly, at which time a grab sample is collected to compare point estimates of stream water chemistry to autosampler data.Most anions (Cl-, Br-, NO2-, NO3-, SO42-) and cations (NH4+, Na+, Mg2+, K+, Ca2+) are analyzed by ion chromatography, soluble reactive phosphorus colorimetrically (American Public Health Association 1998), and dissolved organic carbon, dissolved inorganic carbon and total dissolved nitrogen on a Shimadzu TOC-5000 analyzer plumbed to an Antek nitric oxide chemoluminescent detector.