BNZ-LTER Metadata Catalog

Title:

Leaf leachate chemistry and uptake metrics in headwater streams July 2015

Contacts:

Cocallas, Arianna
Telephone (primary): NA
Telephone (secondary): NA
FAX: NA
Email (primary): acocallas@alaska.edu
Email (secondary): NA
Web URL: NA
Address:

Guerard, Jennifer
Telephone (primary): NA
Telephone (secondary): NA
FAX: NA
Email (primary): NA
Email (secondary): NA
Web URL: NA
Address:

Harms, Tamara
Telephone (primary): (907) 474-6117
Telephone (secondary): NA
FAX: NA
Email (primary): tamara.harms@alaska.edu
Email (secondary): NA
Web URL: http://www.harmslab.org/
Address:
Institute of Arctic Biology, 902 N Koyukuk Ave.
Fairbanks, AK 99775
United States

Jones, Jeremy Boyd
Telephone (primary): (907) 474-7972
Telephone (secondary): NA
FAX: (907) 474-6967
Email (primary): Jay.Jones@alaska.edu
Email (secondary): jbjonesjr@alaska.edu
Web URL: http://www.iab.uaf.edu/people/jay_jones/
Address:
Institute of Arctic Biology; Department of Biology and Wildlife; University of Alaska Fairbanks
Fairbanks, AK 99775
Unites States

Mutschlecner, Audrey
Telephone (primary): (907) 474-6777
Telephone (secondary): NA
FAX: NA
Email (primary): amutschlecner@alaska.edu
Email (secondary): NA
Web URL: NA
Address:
UAF Biology & Wildlife Department, 101 Murie, 982 N. Koyukuk Dr
Fairbanks, Alaska 99775
United States

Abstract:

This dataset contains the results of uptake experiments conducted at Caribou-Poker Creeks Research Watershed in July 2015. The objective of the study was to determine the relative influence of molecular composition and nutrient content of organic matter on the retention of dissolved organic matter (DOM) in boreal streams. We measured in situ rates of carbon uptake in streams following introduction of leachates derived from of alder (Alnus incana ssp. tenuifolia), poplar (Populus balsamifera), and white spruce (Picea glauca) trees subject to long-term fertilization with nitrogen (N) or phosphorus (P). We measured leachate composition through chemical analysis and optical properties (absorbance and fluorescence).

Methods:

FIELD: To determine whether DOM retention is driven by nutrient content or molecular composition, we measured carbon uptake in streams following addition of dissolved organic matter derived from leaf leachates produced from three species of trees subject to long-term nutrient fertilization. Leaves were collected from the Bonanza Creek Experimental Forest (64.82°N, 147.87°W), located approximately 35 km southwest of Fairbanks, AK. The Bonanza Creek Long-Term Ecological Research program maintains plots (20x20 m) of alder (Alnus incana ssp. tenuifolia), poplar (Populus balsamifera), and white spruce (Picea glauca) fertilized with N (100 kg N ? ha–1 ? yr–1 as NH4NO3) or P (80 kg P ? ha–1 ? yr–1 as P2O5) as well as unfertilized control plots (30x30 m). Fertilization has occurred annually since 1997 for N and since 2004 for P (Ruess et al. 2013). Leaves were harvested in September 2013 and 2014 from nine plots: alder control, alder N, alder P, poplar control, poplar N, poplar P, spruce control, spruce N, and spruce P. Leaves were clipped from branches after senescence had begun, so that resorption would have occurred and chemical composition of leaves would include leachable compounds that could be present in streams. Freshly fallen leaves were also collected from the forest floor. We measured uptake of dissolved organic carbon (DOC) following addition of leachates to streams in July 2015. The nine types of leachates were added to each of the five streams, resulting in 45 total experiments. Experiments at each stream were performed over one to two days to maintain constant discharge and antecedent conditions across experiments within each stream, and the leachates were added to each stream in a random order. Reach length at each stream was chosen such that travel time was approximately 30 minutes. We estimated travel time on the day prior to leachate additions by releasing a 300-g slug of sodium chloride (NaCl) and monitoring the resulting change in conductivity. We measured retention of DOC in streams following addition of a slug of each leachate. Prior to the start of experiments, we collected three water samples along the study reach for analysis of ambient stream chemistry. We also measured stream width at 15 transects along the reach. Discharge was measured by NaCl dilution gauging at both the top and bottom of the study reach prior to the first and following the last experiment each day. To measure C uptake, we added a slug containing NaCl as a conservative tracer and one of the nine leachate types to the top of the reach and collected samples through the resulting breakthrough curve at the bottom of the study reach. The mass of NaCl added was adjusted to achieve a target concentration of 10 mg Cl–/L above background concentration at the peak of the breakthrough curve, and the volume of leachate in each slug was adjusted to yield an increase of 1.5 mg DOC/L above background concentration. The target concentration of DOC was selected so that added DOC could be reliably detected above background without elevating DOC concentration such that reaction kinetics would differ significantly from ambient conditions. Arrival of the tracer was monitored using a conductivity probe at the downstream station, and 25 water samples were taken throughout the breakthrough curve. Water samples were filtered in the field (0.7 ?m, Whatman GF/F), placed on ice, and frozen until analysis. The next leachate was added after specific conductivity declined to a stable background value. LAB: Leaves were dried at 60°C to constant mass and stored in paper bags. Leachates were prepared by soaking crushed leaves in deionized water. Alder and poplar leaves were crushed by hand to roughly 1-cm fragments and spruce needles were crushed to the same size using a hammer. Leaves were placed in nylon bags (approximately 200 ?m mesh size), mixed with deionized water (18 M?) at a ratio of 100 g leaves to 1 L water, and continuously stirred at 4°C for 36–48 hours. Resulting leachates were filtered through 0.7 ?m glass fiber filters (Whatman GF/F) and frozen until use (< 7 days). Samples from the uptake experiments were analyzed for concentration of chloride and dissolved organic carbon. Samples of ambient stream water as well as diluted aliquots of each leachate were analyzed for dissolved organic carbon (DOC), total dissolved nitrogen (TN), ammonium (NH4+), nitrate (NO3–), and total dissolved P (TDP). Biogeochemical retention of DOC in the streams, which can be attributed to biological uptake, photochemical reactions, and sorption, was calculated by mass balance using the method described by Covino et al. (2010). First, the mass of tracer recovered (TMR) was calculated for both the conservative (Cl–) and reactive (DOC) tracers by multiplying the time-integrated tracer concentration by discharge. Next, total tracer retention was calculated as the difference between the mass of tracer added and the mass of tracer recovered. Chloride was assumed to be biologically and chemically inactive in the stream, so the proportion of chloride not recovered represents physical retention in slower flowpaths. This proportion was applied to the mass of the added reactive tracer (DOC) to account for hydrologic storage of C. Finally, biogeochemical retention was calculated as the difference between total tracer retention and hydrologic retention. We calculated metrics of nutrient spiraling following the Stream Solute Workshop (1990) to allow comparison with previous estimates of DOC uptake. These metrics describe the simultaneous transport and retention of solutes as they travel downstream. Uptake length (Sw, m), which describes the mean distance a molecule of C travels in dissolved form in the water column before being taken up, was calculated as the negative inverse of the slope of a regression between the natural logarithm of the DOC:Cl– ratios of the injectate and tracer masses recovered (background-corrected) against the reach length (D). Uptake velocity (Vf, mm/min), the vertical rate at which DOC moved from the water column to the benthos due to biological demand, was calculated as stream discharge divided by the uptake length times average stream width. Finally, the areal uptake rate (U, mg m-2 day-1) was calculated by multiplying Vf by the geometric mean of conservative (based on Cl– recovery) and observed background-corrected DOC concentrations throughout the breakthrough curve.

Experimental Design:

We estimated the effects of nutrient content and molecular composition of dissolved organic carbon (DOC) on uptake in boreal streams by measuring in situ rates of C retention following introduction of leachates derived from of alder (Alnus incana ssp. tenuifolia), poplar (Populus balsamifera), and white spruce (Picea glauca) trees subject to long-term fertilization with nitrogen (N) or phosphorus (P). The leachates varied by molecular composition, due to differences in tissue chemistry of plant species, and in nutrient content, because the leaves were collected from plots with different fertilization regimes. The uptake experiments were conducted at five replicate headwaters streams (C1, C2, C3, C4, P6) at Caribou-Poker Creeks Reserach Watershed.

Supplemental Documentation:

Chloride and nitrate (NO3–) concentrations were measured on an ion chromatograph (Dionex ICS 2100, AS18 column, Thermo Fisher Scientific) with limits of quantification (LOQ) of 0.03 mg Cl–/L and 0.5 ?g NO3– -N/L. DOC concentration was measured as non-purgeable organic C by non-dispersive, infrared gas analysis following combustion on a total organic C analyzer (TOC-L CPH, Shimadzu Scientific Instruments, LOQ = 0.1 mg C/L) connected to a TN module with detection of N by chemiluminescence (TNM-L, LOQ = 0.02 mg N/L). NH4+ was measured by automated colorimetry (Smartchem 170, Westco Scientific Instruments, LOQ = 0.01 mg N/L) using the phenol hypochlorite method (Solórzano 1969). TDP was measured following persulfate digestion using the molybdate blue method (Murphy and Riley 1962) on a spectrophotometer with a 5-cm cell (Shimadzu UVmini 1240, Shimadzu Scientific Instruments, LOQ = 0.6 ?g P/L). Nitrite is not detectable in the study streams and concentration of dissolved organic N (DON) was therefore determined by difference of TDN and NO3– -N + NH4+-N. C and N content of dry leaf tissue was determined using an elemental analyzer (CHNS-O, Costech Analytical Technologies Inc., LOQ = 0.03 mg C and 0.01 mg N). P content of dry leaf tissue was measured as for water samples described above. When measured values were below the LOQ, one half of LOQ was used in data analysis. To characterize the molecular composition of the leachates, we measured absorbance of UV and visible light as well as fluorescence spectra on filtered samples (0.45 ?m, Pall GN-6) using a fluorometer (Jobin-Yvon Horiba Aqualog-800-C, Horiba Instruments) with a 1-cm quartz cuvette (Firefly Scientific). Excitation-emission matrices (EEMs) were collected over an excitation range of 240–600 nm every 3 nm and an emission range of 247–847 nm every 2.33 nm with an integration time of 0.1 seconds and a medium gain. The excitation-emission matrices (EEMs) derived from sample fluorescence were instrument-corrected, blank-subtracted, Raman-normalized, and corrected for inter-filter effects. Parallel factor analysis (PARAFAC) was applied to resolve fluorescing components using the DOMFluor toolbox (version 1-7, Stedmon and Bro 2008) in Matlab (version R2015b, MathWorks). The dataset included a total of 229 samples including the 45 leachates samples as well as 184 stream samples from boreal and arctic Alaska (Mutschlecner et al., in prep.). A model including five components was best supported by the data as determined by inspection of residuals for random variation and model validation. Component descriptions are presented in the following file “Fluorescent components identified in leachates July 2015.csv”

Corrections:

None on file.

Supplemental Acknowledgements:

Funding support was provided by the Institute of Arctic Biology Summer Graduate Research Award, the Midnight Sun Symposium Presentation Award, and the Nicholas F. Hughes Memorial Scholarship, as well as the Bonanza Creek Long-Term Ecological Research program (funded jointly by NSF grant DEB-1026415 and USDA Forest Service, Pacific Northwest Research Station grant PNW01-JV-11261952-231).

Keywords:

carbon cycling, decomposition, dissolved organic matter, nutrients, streams

Categories:

Biogeochemistry, Decomposition, Stream Ecology

Study Period:

2015-07-01 to 2015-07-30

Sampling Frequency:

Irregular

Bounding Box:

West Longitude: -147.388939°
North Latitude: 65.14329713°
East Longitude: -147.647846°
South Latitude: 65.184791°
Datum: NAD83

Site References:

Site ID: C1
Description: The C1 basin is the western-most headwater tributary of Caribou Creek.
Directions: C1 can be reached on foot from the C2 flume. Head up the basin that is directly to the west of the flume.
Site History: Data have been collected from C1 starting in 1969 and continuing at least through 1977. There is currently no data collection effort occurring in C1.
Location: NA

Site ID: C2
Description: The tributary basins of Caribou Creek are all arbitrarily designated with a "C". The C2 basin is the sub-basin with the least amount of permafrost of the CPCRW sub-basins. As such, it has been often been studied intensively in conjunction with C3, the sub-basin with the greatest amount of permafrost. The basin trends to the south, with well-drained slopes and permafrost-underlain treeless muskeg in valley bottom. Although an extensive fire history has not been done, there was probably a stand-replacing fire early in this century (ca. 1925), with some large white spruce stands that survived from the earlier vegetation.
Directions: The C2 site is accessible by all-terrain vehicle or snow machine by a trail that runs west from the confluence of Caribou and Poker Creeks. Stay to the right at the "T" junction about 3 miles up the valley: the left turn goes to the CB and C3 sites, and the trail to Haystack Mountain. The passable portion of the trail ends at the flume in the C2 valley bottom, and an unmaintained, impassable trail goes up into the headwaters of the main C2 tributary. The latitude and longitude listed below refer to the flume.
Site History: The flume at C2 was first installed in about 1974.
Location: The basin is located in the northwestern "corner" of CPCRW.

Site ID: C3
Description: The tributary basins of Caribou Creek are all arbitrarily designated with a "C". The C3 basin is the sub-basin with the most permafrost of the CPCRW sub-basins. As such, it has been often been studied intensively in conjunction with C2, the sub-basin with the least amount of permafrost. The basin trends to the northeast, with black spruce/feather moss slopes and permafrost-underlain treeless muskeg in valley bottom.
Directions: NA
Site History: NA
Location: NA

Site ID: C4
Description: This is a weather station in the C4 watershed in the Caribou Poker Creeks Research Watershed.
Directions: NA
Site History: NA
Location: NA

Site ID: P6
Description: Basin in Caribou-Poker Creeks Research Watershed
Directions: NA
Site History: NA
Location: Caribou-Poker Creeks Research Watershed, north of Fairbanks, Alaska, USA

Data Columns:

Column: 1
Variable Name: Site
Description: Name of site where uptake experiment was conducted
Units: NA
Type: string
Measurement Scale: nominal
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 2
Variable Name: Leachate Species
Description: Species from which leaves were collected to create leachate
Units: NA
Type: string
Measurement Scale: nominal
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 3
Variable Name: Leachate Fertilzation Treatment
Description: Fertilzation regime for the plot from which the leaves were collected to create leachate
Units: NA
Type: string
Measurement Scale: nominal
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 4
Variable Name: Date
Description: Date the uptake experient occurred
Units: mm/dd/yyyy
Type: string
Measurement Scale: date-time
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 5
Variable Name: DOC mg/L
Description: Dissolved organic carbon concentration of the leachate
Units: mg/L
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 6
Variable Name: TN mg/L
Description: Total dissolved nitrogen concentration of the leachate
Units: mg/L
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 7
Variable Name: DON mg/L
Description: Dissolved organic nitrogen concentration of the leachate
Units: mg/L
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 8
Variable Name: NH4 mg/L
Description: Ammonium concentration of the leachate
Units: mg/L
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 9
Variable Name: NO3 mg/L
Description: Nitrate concentration of the leachate
Units: mg/L
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 10
Variable Name: TDP uM
Description: Total dissolved phosphorus concentration of the leachate
Units: uM
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 11
Variable Name: Dry Mass C %
Description: Percent of carbon in the leaves from which the leachate was created
Units: %
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 12
Variable Name: Dry Mass N %
Description: Percent of nitrogen in the leaves from which the leachate was created
Units: %
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 13
Variable Name: Dry Mass P %
Description: Percent of phosphorus in the leaves from which the leachate was created
Units: %
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 14
Variable Name: A254
Description: Absorbance at 254 nm of the leachate
Units: no units
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 15
Variable Name: SUVA
Description: Specific ultraviolet absorbance at 254 nm of the leachate
Units: L mgC-1 m-1
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 16
Variable Name: SlopeRatio
Description: Spectral slope ratio, calculated from sample absorbance
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 17
Variable Name: FI
Description: Flurescence index, calculated from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 18
Variable Name: HI
Description: Humification index, calculated from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 19
Variable Name: BIX
Description: Biological index, calculated from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 20
Variable Name: BA
Description: Beta:alpha (freshness index), calculated from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 21
Variable Name: Component 1
Description: The loading of Compoent 1, which was statistically resolved from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 22
Variable Name: Component 2
Description: The loading of Compoent 2, which was statistically resolved from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 23
Variable Name: Component 3
Description: The loading of Compoent 3, which was statistically resolved from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 24
Variable Name: Component 4
Description: The loading of Compoent 4, which was statistically resolved from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 25
Variable Name: Component 5
Description: The loading of Compoent 5, which was statistically resolved from sample fluorescence
Units: NA
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 26
Variable Name: DOC retention %
Description: Biogeochemical retention of leachate dissolved organic carbon added to streams, which can be attributed to biological uptake, photochemical reactions, and sorption
Units: %
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 27
Variable Name: Sw
Description: Uptake length of leachate dissolved organic carbon added to streams
Units: m
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 28
Variable Name: Vf
Description: Uptake velocity of leachate dissolved organic carbon added to streams
Units: mm/min
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Column: 29
Variable Name: U
Description: Areal uptake rate of leachate dissolved organic carbon added to streams
Units: mg/(m2*day)
Type: float
Measurement Scale: ratio
Value Codes: NA
Error Codes: NA
Minimum Valid Value: NA
Maximum Valid Value: NA
Output Precision:
Calculations:

Public Release:

2017-04-03