Prospect Hill Soil Warming Experiment at Harvard Forest since 1991

<para>The soil warming experiment was installed on the Prospect Hill tract in 1991 to allow us to investigate the effects of a 5 deg C temperature increase on soil processes fundamental to the global cycling of carbon and nitrogen. The experiment is located in an even-aged mixed hardwood forest. Six replicates of three treatments, Heated (resistance heating cables buried at 10cm and maintained at a 5 deg C differential from the control plots), Disturbance Control (cables installed but not powered) and Control treatments make up the randomized block design. The temperature differential is maintained with monitoring at five minute increments by an automated thermistor network in the plots, wired to a multiplexer and a datalogger in the control shed. In the plots, measurements of trace gasses (CO2, N2O and CH4), nitrogen mineralization, soil moisture and soil water chemistry have allowed us to quantify changes in the soil system.</para> <para>Ten years of elevated soil temperatures at the Harvard Forest soil warming experiment suggest that there are limits to a positive feedback to the global warming cycle. After many early years of increased CO2 fluxes from the warmed plots, years nine and ten have revealed no significant differences in releases of CO2 between the heated and control plots. Nitrogen mineralization has shown a large response to warming as well, with twice the rate of N mineralized in years 1-4, followed by a gradual decrease in rates to about the 40% level in 1998. Resumption of mineralization measurements in 2001 reveals a continued decrease in mineralization rates.</para> <para>Field results from the soil warming experiment indicate that only a small fraction of the soil carbon in this mid-latitude forest ecosystem will be lost to the atmosphere in response to warming. We find that a 5 deg C warming of the soil for a decade results in a loss of about 11% of the carbon stored in the top 60 cm of soil, with most of this loss occurring in the first four to five years. By the end of the decade, warming no longer stimulates soil carbon loss. In addition, we find that warming accelerates the soil nitrogen cycle, particularly in the early years of warming. This acceleration has the potential to stimulate plant carbon storage.</para> <para>Calculations based on nitrogen uptake in vegetation at the Chronic N Experiment (Magill, Aber et al. 2000) allow us to estimate how much additional carbon might be stored in plants as a result increased N availability at soil warming. Our calculations show that the potential increase in carbon stored is large enough to more than compensate for the soil carbon loss, so that warming may actually stimulate carbon storage at the ecosystem level in this mid-latitude forest.</para> <para>We are currently expanding our research from the original soil warming experiment to investigate this important feedback at the Harvard Forest. The existing 6x6m plots on the Prospect Hill tract are not large enough to allow for the study of treatment effects on trees, so we are installing a larger warming experiment. The new experiment will have two 30x30m plots, a heated and a control plot, in the Slab City Tract of the Harvard Forest. Many aspects of this experiment will be the same as the original. Using resistance heating cables and thermistors, we will maintain a 5 deg C differential between the heated and control plots, year-round. In addition to the trace gas, nitrogen mineralization and soil water parameters measured to date, we will also be measuring woody increment and other vegetation metrics to allow us to investigate the plant response to perturbations in the carbon and nitrogen cycles.</para> </section> </abstract> <keywordSet> <keyword>carbon</keyword> <keyword>carbon dioxide</keyword> <keyword>climate change</keyword> <keyword>methane</keyword> <keyword>nitrogen</keyword> <keyword>nitrogen mineralization</keyword> <keyword>nitrous oxide</keyword> <keyword>soil moisture</keyword> <keyword>soil respiration</keyword> <keyword>soil temperature</keyword> <keyword>soil warming</keyword> <keywordThesaurus>LTER controlled vocabulary</keywordThesaurus> </keywordSet> <keywordSet> <keyword>inorganic nutrients</keyword> <keyword>disturbance</keyword> <keywordThesaurus>LTER core area</keywordThesaurus> </keywordSet> <keywordSet> <keyword>Harvard Forest</keyword> <keyword>HFR</keyword> <keyword>LTER</keyword> <keyword>USA</keyword> <keywordThesaurus>HFR default</keywordThesaurus> </keywordSet> <intellectualRights> <section> <para>This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.</para> </section> </intellectualRights> <licensed> <licenseName>Creative Commons Zero v1.0 Universal</licenseName> <url>https://spdx.org/licenses/CC0-1.0.html</url> <identifier>CC0-1.0</identifier> </licensed> <distribution> <online> <url function="information">https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf005</url> </online> </distribution> <coverage> <geographicCoverage> <geographicDescription>Prospect Hill Tract (Harvard Forest). Coordinates based on WGS84 datum.</geographicDescription> <boundingCoordinates> <westBoundingCoordinate>-72.18</westBoundingCoordinate> <eastBoundingCoordinate>-72.18</eastBoundingCoordinate> <northBoundingCoordinate>+42.54</northBoundingCoordinate> <southBoundingCoordinate>+42.54</southBoundingCoordinate> <boundingAltitudes> <altitudeMinimum>365</altitudeMinimum> <altitudeMaximum>365</altitudeMaximum> <altitudeUnits>meter</altitudeUnits> </boundingAltitudes> </boundingCoordinates> </geographicCoverage> <temporalCoverage> <rangeOfDates> <beginDate> <calendarDate>1991</calendarDate> </beginDate> <endDate> <calendarDate>2021</calendarDate> </endDate> </rangeOfDates> </temporalCoverage> </coverage> <maintenance> <description> <para>ongoing</para> </description> </maintenance> <contact scope="document"> <positionName>Information Manager</positionName> <organizationName>Harvard Forest</organizationName> <address scope="document"> <deliveryPoint>324 North Main Street</deliveryPoint> <city>Petersham</city> <administrativeArea>MA</administrativeArea> <postalCode>01366</postalCode> <country>USA</country> </address> <phone phonetype="voice">(978) 724-3302</phone> <electronicMailAddress>hf-im@lists.fas.harvard.edu</electronicMailAddress> </contact> <publisher scope="document"> <organizationName>Harvard Forest</organizationName> <address scope="document"> <deliveryPoint>324 North Main Street</deliveryPoint> <city>Petersham</city> <administrativeArea>MA</administrativeArea> <postalCode>01366</postalCode> <country>USA</country> </address> <phone phonetype="voice">(978) 724-3302</phone> <phone phonetype="fax">(978) 724-3595</phone> <onlineUrl>https://harvardforest.fas.harvard.edu</onlineUrl> </publisher> <methods> <methodStep> <description> <section> <para>Gas measurements were made by placing chamber lids over anchored collars for 15 min and sampling the headspace at 5-min intervals. Samples were analyzed for trace gas concentrations by gas chromatography or infrared analysis, and the changes in concentration were used to calculate net flux rates. On each sampling date, fluxes were measured at early morning and afternoon intervals. N2O and CH4 fluxes were measured from 1991 to 1995 along with the CO2 measurements using the same static chamber method.</para> <para>Soil temperatures were measured at the surface and 2 and 4cm at the time of each gas sampling. Plot temperatures were also constantly monitored by an automated thermistor system, allowing comparison between control and heated plots at 5 minute intervals, with according powering up or down of the plots as needed.</para> <para>Soil moisture measurements were conducted using gravimetric techniques for the first 4 years of the study and by time domain reflectometry (TDR) from 1995-2002.</para> <para>Net N mineralization and nitrification were measured for the forest floor and mineral soil using an on-site buried bag incubation. Incubations were for 6 weeks, April- November, and for 5 months through the winter. Initial samples were collected and analyzed for extractable (2N KCl, 48 hours) NH4+ and NO3- content. The same analysis was carried out on the incubated samples. The difference in total mineral N content between initial and incubated soils is the net mineralization rate.</para> <para>Concentrations of inorganic N in water leaching below the rooting zone were measured using high-tension lysimetry. Soil water samples were collected from one porous cup lysimeter per plot on two occasions every month for the first 2 years of the experiment, then monthly. Lysimeters were installed at a depth of 50 cm and evacuated to 15 in Hg 24 h before sampling. Samples were frozen until they were analyzed for NH4+ and NO3-.</para> </section> </description> </methodStep> </methods> <project> <title>Harvard Forest Long-Term Ecological Research Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu https://ror.org/059cpzx98 pointOfContact The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210. hf005-01-trace-gas.csv trace gas flux hf005-01-trace-gas.csv 96166 7c46d5da8bde695d1669313b3b7508a1 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-01-trace-gas.csv year year YYYY NA missing value rep replicate number replicate number NA missing value date sample date YYYY-MM-DD NA missing value treatment treatment code 1 control 2 disturbed control 3 heated 5 deg C NA missing value block block number. There are 3 blocks, each with 6 plots grouped in a randomized block design. block number. There are 3 blocks, each with 6 plots grouped in a randomized block design. NA missing value co2_flux CO2 flux (mg C/m2/hr). Samples collected every 5 min for 15 min using a static chamber method. Samples analyzed by infrared analysis milligramPerMeterSquaredPerHour 0.01 real NA missing value ch4_flux CH4 flux (mg C/m2/hr). Samples collected every 5 min for 15 min using a static chamber method. Samples were analyzed by gas chromatography. milligramPerMeterSquaredPerHour 0.01 real NA missing value n2o_flux N2O flux (ug N/m2/hr). Samples collected every 5 min for 15 min using a static chamber method. Samples were analyzed by gas chromatography. microgramPerMeterSquaredPerHour 0.01 real NA missing value temp_2cm soil temperature at 2 cm depth taken at the time of gas sampling celsius 0.01 real NA missing value temp_4cm soil temperature at 4 cm depth taken at the time of gas sampling celsius 0.01 real NA missing value grav_h2o_org organic gravimetric soil water (g H2O/g soil) gramsPerGram 0.01 real NA missing value grav_h2o_min mineral gravimetric soil water (g H2O/g soil) gramsPerGram 0.01 real NA missing value vol_h2o soil water (cm3 H2O/cm3 soil) measured using time domain reflectometery (TDR) cubicCentimetersPerCubicCentimeters 0.01 real NA missing value 1593 hf005-02-lysimeter.csv lysimeter hf005-02-lysimeter.csv 62772 a59b4f62fec5586fc4ec4005626dc0dd 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-02-lysimeter.csv date sample date YYYY-MM-DD NA missing value year year YYYY NA missing value plot plot number plot number NA missing value treatment treatment code C control DC disturbed control H heated 5 deg C NA missing value lys_no3 samples were collected from a high-tension lysimeter installed at a depth of 50cm. Samples were analyzed for dissolved NO3- milligramsPerLiter 0.001 real NA missing value lys_nh4 samples were collected from a high-tension lysimeter installed at a depth of 50cm. Samples were analyzed for dissolved NH4+ milligramsPerLiter 0.0001 real NA missing value volume volume of sample collected milliliter 0.1 real NA missing value notes notes notes NA missing value 1561 hf005-03-nmin.csv nitrogen mineralization hf005-03-nmin.csv 167450 c9d88d041ea8c6ffc724b3a187019adc 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-03-nmin.csv year year YYYY NA missing value rep replicate number replicate number NA missing value date sample date YYYY-MM-DD NA missing value horizon soil horizon 0 organic 3 mineral NA missing value treatment treatment code C control DC disturbed control H heated 5 deg C NA missing value plot plot number plot number NA missing value net_no3 net N mineralization in the form of NO3- (mg N/kg) released during incubation period milligramPerKilogram 0.01 real NA missing value net_nh4 net N mineralization in the form of NH4+ (mg N/kg) released during incubation period milligramPerKilogram 0.01 real NA missing value net_ion combined net mineralization (mg N/kg) released during incubation period milligramPerKilogram 0.01 real NA missing value days_incu number of days of on-site buried bag incubation number 0.1 real NA missing values depth depth of soil horizon centimeter 0.001 real NA missing value bd bulk density greater than 2mm gramPerMeterCubed 0.001 real NA missing value 2942 hf005-04-soil-temp.csv soil temperature hf005-04-soil-temp.csv 2742575 cb203bbf914a1de75e8572a4daf17dea 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-04-soil-temp.csv date date YYYY-MM-DD NA missing value year year YYYY NA missing value doy Julian date nominalDay 1 whole NA missing value month month month of measurement NA missing value day day day of measurement NA missing value plot1h temp measured at 5 cm depth in plot 1 (heated) celsius 0.001 real NA missing value plot6h temp measured at 5 cm depth in plot 6 (heated) celsius 0.001 real NA missing value plot8h temp measured at 5 cm depth in plot 8 (heated) celsius 0.001 real NA missing value plot12h temp measured at 5 cm depth in plot 12 (heated) celsius 0.001 real NA missing value plot15h temp measured at 5 cm depth in plot 15 (heated) celsius 0.001 real NA missing value plot16h temp measured at 5 cm depth in plot 16 (heated) celsius 0.001 real NA missing value plot3d temp measured at 5 cm depth in plot 3 (disturbance control) celsius 0.001 real NA missing value plot5d temp measured at 5 cm depth in plot 5 (disturbance control) celsius 0.001 real NA missing value plot9d temp measured at 5 cm depth in plot 9 (disturbance control) celsius 0.001 real NA missing value plot10d temp measured at 5 cm depth in plot 10 (disturbance control) celsius 0.001 real NA missing value plot13d temp measured at 5 cm depth in plot 13 (disturbance control) celsius 0.001 real NA missing value plot17d temp measured at 5 cm depth in plot 17 (disturbance control) celsius 0.001 real NA missing value plot2c temp measured at 5 cm depth in plot 2 (control) celsius 0.001 real NA missing value plot4c temp measured at 5 cm depth in plot 4 (control) celsius 0.001 real NA missing value plot7c temp measured at 5 cm depth in plot 7 (control) celsius 0.001 real NA missing value plot11c temp measured at 5 cm depth in plot 11 (control) celsius 0.001 real NA missing value plot14c temp measured at 5 cm depth in plot 14 (control) celsius 0.001 real NA missing value plot18c temp measured at 5 cm depth in plot 18 (control) celsius 0.001 real NA missing value avg_heat average temp in Heated plots celsius 0.001 real NA missing value avg_cont average temp in Control plots celsius 0.001 real NA missing value avg_dcon average temp in Disturbance Control plots celsius 0.001 real NA missing value shed_air average air temp taken at the Prospect Hill Soil Warming site celsius 0.001 real NA missing value 11138 hf005-05-soil-respiration.csv soil respiration hf005-05-soil-respiration.csv 357576 0e0421231d6b073688ada446d804e137 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-05-soil-respiration.csv datetime date and time YYYY-MM-DDThh:mm 1 minute NA missing value year year that the data was collected YYYY month month that the data was collected month of measurement NA missing value day day the data was collected day of measurement NA missing value time time data was collected rounded to the nearest hour hh:mm NA missing value treatment treatment code C control DC disturbance control H heated plot NA missing value plot Plot ID Plot ID NA missing value co2_flux CO2 flux in mg C m-2 h-1 milligramPerMeterSquaredPerHour 0.01 real NA missing value temp_4cm soil temperature at 4 cm depth celsius 0.1 real NA missing value moisture soil moisture (% volumetric moisture content) dimensionless 0.01 real NA missing value rainflag whether or not sampling was likely affected by a respiration pulse from a recent (within 2 days) significant precipitation event 0 not likely affected by rain pulse 1 likely affected by rain pulse NA missing value measurement measurement type Li8100-a automatic LI-COR measurement static static chamber gas syringe measurement NA missing value 5681 hf005-06-fine-root-biomass.csv fine root biomass hf005-06-fine-root-biomass.csv 7732 3f3ca9c4a51f0ecc5de6ea0437a7090d 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-06-fine-root-biomass.csv date sample date YYYY-MM-DD NA missing value plot plot number plot number NA missing value treatment treatment code DC disturbed control H heated NA missing value horizon soil horizon M mineral O organic NA missing value sorter technician who sorted roots into live and dead pools 1 technician 1 2 technician 2 1,2 both techician 1 and technician 2 worked on this sample NA missing value live_dead whether live or dead roots Live live roots Dead dead roots NA missing value size_class root diameter size class (mm) root diameter size class (mm) NA missing value biomass root biomass gramsPerSquareMeter 0.01 real NA missing value n_per percent nitrogen content of bulked roots of this class, expressed as a decimal dimensionless 0.0001 real NA missing value c_per percent carbon content of bulked roots of this class, expressed as a decimal dimensionless 0.0001 real NA missing value d15n nitrogen isotope ratio content of bulked roots of this class, expressed as d15N (o/oo vs. AIR) dimensionless 0.01 real NA missing value d13c carbon isotope ratio of bulked roots of this class, expressed as d13C (o/oo vs. PDB) dimensionless 0.01 real NA missing value 132 hf005-07-soil-moisture.csv soil moisture hf005-07-soil-moisture.csv 468571 ae74877ae86a43a6bbdbfbff2f1dcd98 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-07-soil-moisture.csv date date YYYY-MM-DD 1 day NA missing value p1_sm TDR volumetric soil moisture in Plot 1 (Heated) dimensionless 0.000000001 real NA missing value p2_sm TDR volumetric soil moisture in Plot 2 (Control) dimensionless 0.000000001 real NA missing value p3_sm TDR volumetric soil moisture in Plot 3 (Disturbance Control) dimensionless 0.000000001 real NA missing value p4_sm TDR volumetric soil moisture in Plot 4 (Control) dimensionless 0.000000001 real NA missing value p5_sm TDR volumetric soil moisture in Plot 5 (Disturbance Control) dimensionless 0.000000001 real NA missing value p6_sm TDR volumetric soil moisture in Plot 6 (Heated) dimensionless 0.000000001 real NA missing value p7_sm TDR volumetric soil moisture in Plot 7 (Control) dimensionless 0.000000001 real NA missing value p8_sm TDR volumetric soil moisture in Plot 8 (Heated) dimensionless 0.000000001 real NA missing value p9_sm TDR volumetric soil moisture in Plot 9 (Disturbance Control) dimensionless 0.000000001 real NA missing value p10_sm TDR volumetric soil moisture in Plot 10 (Disturbance Control) dimensionless 0.000000001 real NA missing value p11_sm TDR volumetric soil moisture in Plot 11 (Control) dimensionless 0.000000001 real NA missing value p12_sm TDR volumetric soil moisture in Plot 12 (Heated) dimensionless 0.000000001 real NA missing value p13_sm TDR volumetric soil moisture in Plot 13 (Disturbance Control) dimensionless 0.000000001 real NA missing value p14_sm TDR volumetric soil moisture in Plot 14 (Control) dimensionless 0.000000001 real NA missing value p15_sm TDR volumetric soil moisture in Plot 15 (Heated) dimensionless 0.000000001 real NA missing value p16_sm TDR volumetric soil moisture in Plot 16 (Heated) dimensionless 0.000000001 real NA missing value p17_sm TDR volumetric soil moisture in Plot 17 (Disturbance Control) dimensionless 0.000000001 real NA missing value p18_sm TDR volumetric soil moisture in Plot 18 (Control) dimensionless 0.000000001 real NA missing value 2304 hf005-08-swlayout.gif soil warming layout hf005-08-swlayout.gif 17538 a1fcf529f207b890bf8a8db1821a1766 gif https://harvardforest.fas.harvard.edu/data/p00/hf005/hf005-08-swlayout.gif image plot soil long-term measurement 4 https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf018 milligramPerMeterSquaredPerHour microgramPerMeterSquaredPerHour gramPerMeterCubed