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# Harvard Forest Data Archive

### HF007

## DIRT Litter Manipulation Experiment at Harvard Forest since 1990

Related Publications### Data

- hf007-01: coarse woody debris (preview)
- hf007-02: litterfall (preview)
- hf007-03: tree inventory (preview)
- hf007-04: soil moisture (preview)
- hf007-05: soil temperature (preview)
- hf007-06: soil respiration (preview)
- hf007-07: root mass (preview)
- hf007-08: soil properties - 1990 (preview)
- hf007-09: soil properties 1991 (preview)
- hf007-10: soil properties - 1995 (preview)
- hf007-11: soil properties - 2000 (preview)
- hf007-12: plot key (preview)

### Overview

**Lead:**Serita Frey, Knute Nadelhoffer, Richard Boone, Richard Bowden, Kate Lajtha, Johannes Rousk**Investigators:**Jacqueline Aitkenhead-Peterson, Jana Canary, Jason Garrison, Jason Kaye, William McDowell, Jerry Melillo, Patricia Micks**Contact:**Information Manager**Start date:**1990**End date:**2004**Status:**ongoing**Location:**Tom Swamp Tract (Harvard Forest)**Latitude:**+42.49 degrees**Longitude:**-72.20 degrees**Elevation:**320 meter**Datum:**WGS84**Taxa:****Release date:**2023**Language:**English**EML file:**knb-lter-hfr.7.25**DOI:**digital object identifier**EDI:**data package**DataONE:**data package**Related links:****Study type:**long-term measurement**Research topic:**large experiments and permanent plot studies; soil carbon and nitrogen dynamics**LTER core area:**organic matter movement, mineral cycling, disturbance patterns**Keywords:**carbon, decomposition, litter, nitrogen, roots, soil, soil organic matter**Abstract:**The DIRT Experiment (Detritus Input and Removal Treatments) is a long-term study of controls on soil organic matter formation. Our goal is to assess how rates and sources of plant litter inputs control the accumulation and dynamics of organic matter and nutrients in forest soils over decadal time scales. Results from 11 years of field and laboratory studies demonstrate the relative importance of above- and belowground sources on soil organic matter (SOM) dynamics and show emerging long-term non-linear changes in soil carbon release and storage.

Treatments established in a mixed hardwood stand in 1990 are: doubling annual aboveground litter (DL), exclusion of aboveground litter (NL), exclusion of root inputs by trenching (NR), and exclusion of aboveground litter and root inputs (NI), on replicated 3m x 3m plots (n=3 for treatments, 6 for controls). The O/A-less treatment, implemented in 1991, tracks the recovery of impoverished soil by replacing O and A horizon soil with B horizon material and allowing normal litter inputs thereafter. Comparison of data among treatments (soil respiration, soil solution chemistry, soil physical and chemical properties, and microfaunal and microbial community structure) allows us to determine the contributions of live roots, above-ground litter, and belowground detritus to SOM and nutrient dynamics in this forest soil. Similar experiments in Pennsylvania, Wisconsin, Oregon, and Hungarian forests provide information on these processes across climate and soil texture gradients.

First-year soil respiration results from the Harvard Forest DIRT plots showed that live root respiration, production of aboveground litter (leaf, twig, other fine litter) and fine root detritus each constitute about one-third of C inputs to soil. Soil respiration is influenced more by root inputs than aboveground litter in this forest. CO2 efflux from root-excluded soils (NR, NI) declined to 32% of controls over the first 11 years of treatments as soil C became more recalcitrant. Excluding aboveground inputs (NI) had little additional negative effect when root inputs were excluded (NR). Doubling or excluding aboveground litter proportionally increased or decreased respiration, respectively, from root-intact soils during the first four years. However, after year 8, DL respiration dropped to near or below control levels, indicating decreasing decomposition rates. O/A-less soil respiration rates in year 11 surpassed the root-excluded treatments.

C and N stocks respectively increased or decreased in response to doubling or excluding aboveground litter inputs to root-intact soil. However, stocks declined only slightly in NI soils relative to NR. Changes in soil respiration relative to total soil C mass indicate changing soil organic matter (SOM) quality across treatments and over time. Root inputs remain the stronger influence on the proportion of respired labile C, which declined to 40% of control levels in the root-free soils. Results suggest that aboveground inputs more strongly influence SOM mass, but root inputs have a stronger effect on SOM quality. 10 years of doubling litter inputs increased total soil C but by year 10 respired labile C declined below controls, demonstrating a long-term negative effect on decomposition. Total C in O/A-less soil did not increase markedly but the large labile proportion dropped by half as the young organic matter became more stabilized after 10 years of decomposition.

Soil respiration response to soil temperature was strongly and significantly influenced by treatment, and treatment effects increased with time. Respiration by fine roots and associated rhizosphere organisms was more responsive to temperature than was bulk soil respiration. DL Q10 fell steadily from year 4 to year 11 as decomposition rates declined, and was below NL Q10 by year 10. NL Q10 changed little over time. NI Q10 decreased more than NR despite the fact that its respiration rates are similar to or greater than NR. Q10 for NI and NR decreased more over time than any other treatment. O/A-less soil Q10 increased over time, and was higher than the root-excluded treatments’ Q10 in year 11.

Changes in soil solution organic chemistry required at least 5 years of litter manipulation. By year 7, forest floor DOC concentrations were significantly higher in DL plots and significantly lower in O/A-less plots. Response was mixed in the litter and/or root-excluded treatments. Mineral soil solution chemistry was not affected by treatments. The Oea horizon contributed 40% to forest floor soil solution DOC, leaf litter 44%, and root exudate and decay 16%. Roots appeared to be a sink for DON. Oea soil appears to contribute 107% and leaf litter 39% to forest floor soil solution DON. Mean annual DOC flux was strongly related to forest floor C:N ratio but DON flux was not. Mean annual DOC and DON fluxes were positively related to fungal biomass, suggesting that fungal biomass may be responsible for a large proportion of DOC and DON production. Seasonal changes in DOC:DON ratios in root-intact treatments DL, NL, and controls suggest a decoupling of DOC and DON production. Treatment patterns of DOC flux in year 7 correspond to cumulative DOC and CO2 release from incubated organic horizon soils collected in year 5, as did CO2 efflux measured in the field in year 8. DOC losses from the incubated forest floors were 10 percent of CO2-C gas losses.

Total DIN mineralized in the incubated soils collected in year 5 was also influenced by treatments. Lack of net N mineralization response to variations in aboveground litter suggests that microbial immobilization exerts a strong control over soil N dynamics. Although net N mineralization rates were lower in soils from root-excluded plots, nitrification rates were much higher. Incubated soils from the Pennsylvania site showed similar results. These findings suggest that the absence of roots and mycorrhizal hyphae favor nitrifying bacteria.

After 5 years of treatments, microflora appeared to follow patterns of carbon availability and recalcitrance. Data suggest that fungal:bacterial ratios decline with increasing recalcitrance of soil carbon. Total fungal biomass tended to follow patterns of C and N content, being highest in DL and lowest in NL and NI. Fungal biomass was much greater than bacterial biomass in all treatments, yet aboveground litter inputs may be more important substrates for fungi than are roots. Treatments did not affect the active biomass of fungi or bacteria in forest floors. That litter manipulations strongly affected N mineralization and respiration in laboratory incubated soils suggests that the activities of microbial functional types were influenced by treatments. However, microbial populations are poor predictors of process rates.

In summary, results from field data and intersite soil incubations suggest that aboveground inputs exert a stronger influence on SOM mass, but root inputs have a stronger effect on its quality. The pool of turning over N is slow, having a different dynamic than the faster mineralizable C pool. Metabolism of roots and rhizosphere organisms is more temperature-sensitive than bulk soil organisms. Exclusion of roots had a greater effect on microbial processes than either doubling or excluding aboveground inputs. Declining decomposition rates accompanied by increasing soil C in the DL treatment suggests long-term non-linear changes in soil microbial activity which could lead to increased long-term soil C storage beyond expectations. Changes in above- and belowground plant inputs and their influence on temperature-controlled processes will be significant in determining the effects of a warmer world on the net flux of carbon from soils to the atmosphere.

**Methods:***Soil Bulk Density*For sample processing details, see the information for soil sampling in 1991. This file "HF DIRT in 1991" is listed in the Data Catalog under Sampling Information – Soils. Data given are expressed as Mg of oven-dry (105 deg C) soil per hectare. Data could not be expressed as wt/volume of soil because data for the volume of the greater than 5.6 mm material were not available. Mg/ha = mean Mg/ha per plot. Trtmt = treatment. Depth = Oea horizon or the 0-10 cm depth of mineral soil. se = + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n]. n = number of samples.

*Soil pH*Our method of pH determination was based on the method published in: Methods of Soil Analysis. Part 3: Chemical Methods. 1996. Published by Soil Science Society of America, Inc., and American Society of Agronomy, Inc. Madison, WI, USA. We modified that method as follows: 1) Soils were mixed with 0.01M CaCl2 instead of water. 2) We used a 2:1 liquid:soil ratio for mineral soils and a 4:1 ratio for organic soils. Measurements were made using air-dry soil. pH was measured on replicate soil cores at each depth in each plot for Bousson Forest 1996 soils and for Univ. of Wisconsin Arboretum 1997 soils. Only one sample per depth per plot was measured for pH for the Harvard Forest 1991 and 1995 soils. Where replicate samples were measured, the average pH of the replicates and the standard error are given. Avg = mean of replicate samples. se = + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n]. n = number of samples. trt = treatment (if given). blk = block (if given).

*Root Mass Determination*After the Oea, 0-10 cm mineral and 10-15 cm mineral soils were passed through a 5.6 mm sieve (see Methods for 1991 soil sampling), the roots were picked out and separated into three categories. Two of the categories were fine tree roots and woody tree roots. The third category for the Oea soils was "tubers etc."roots (mainly Mianthemum canadense). The third category for the 0-10 cm soils was "herb" (herbaceous) roots, and for the 10-15 cm soils the third category was designated "other" roots. Roots were rinsed in reverse-osmosis quality water and dried at 70 deg C and weighed. Data were initially expressed as g oven-dry roots per surface area of soil, for each of the depths sampled. Oea data were calculated using a surface area of 225 cm2, the area of the 15 cm x 15cm template. Mineral soil calculations used an area of 20.78 cm2, the area of a 2" diameter core. These values were then scaled up and expressed as kg oven-dry roots per hectare, which is the format of the data file posted here. Data given: Avg = mean root mass expressed as kg/ha per plot for each category and depth//horizon. se = + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n]. n = number of samples. trt = treatment (if given). blk = block (if given).

*Soil Temperature*Soil temperature is collected hourly at 5 cm and 15 cm depths in the mineral soil each plot with a Campbell Scientific data logger and temperature probes. Data collection began on June 9, 1994 (Day of Year 159), and was collected continuously through December 1997. Gaps in data exist for much of 1997, 1998, and 1999 due to datalogger malfunction. Therefore, soil temperature data are not given for 1997 and 1998. The continuous data record resumed in April 1999. In August , 1999, Campbell Scientific probes were removed from No Roots and No Inputs plots (exception: probes were left intact in plot 8, No Roots). An Onset Optic Stowaway datalogger was installed in each No Roots and No Inputs plot to record soil temperature at 10 cm depth. These data are given from August 8, 1999 through October 30, 2001. On November 21, three probes previously installed in plots 4 and 16 (TOX) were mounted on a tree near each of these two plots at breast height, shielded from direct sun, to record air temperatures. These air temperature data are listed in the last (right-hand most) columns in all yearly soil temperature data files beginning November 1999. On October 31, 2001, the rest of the plots received an Onset Optic Stowaway datalogger. Onset dataloggers in all 21 plots were positioned to record soil temperature at a depth of 12 cm. These data are included in the data files for November 2001 and after. NOTE: Frost heaving may partially eject probes from the soil and cause some probes to read air temperature. Probes are repositioned in early spring.

*Data*Data presented are the average of hourly temperature readings for each day of the year. Hourly temperatures are also available in raw form. Data are given in deg C. Only data for functioning probes are given. Treatment: Block = block number. Plot = plot number. Depth = cm below mineral soil surface. Probe = denoted by plot number and depth: a = 5 cm, b = 15 cm, c = 12 or 15 cm as noted; air temp = probes recording air temperature at 1.4 m height above the ground. DOY = Day of year. YEAR. Soil temperature = expressed as deg C. Air temperature = expressed at deg C. nd = no data.

*Soil Respiration*Soda Lime. In 1991, 1992, 1993, and 1994, soil respiration was measured using the soda lime technique (Edwards et al. 1982, Raich et al. 1990). Carbon dioxide emitted from soil was absorbed in 60 g of 105 deg C-oven-dry soda lime contained in an open tin on the soil surface, underneath a white plastic bucket approximately 20 cm tall and 28 cm in diameter. The bucket's upper surface was covered with aluminum foil to minimize solar heating. Rocks (~5 kg) placed on top of each bucket held it firmly against the forest floor. Buckets were seated no more than 1 cm deep to avoid severing live roots. After 24 hours, the soda lime tins were removed, oven-dried (105 deg C), and reweighed. CO2 efflux was measured simultaneously in all 21 plots on each collection date. The same location within each plot was sampled on each date. The weight gain of the soda lime during the 24 hours of CO2 absorption was used to calculate the CO2 efflux from the soil surface. Soil respiration was measured approximately once a week from May-September, and every two weeks or once per month in the fall and spring. The period of time over which measurements were made varied from year to year. Measurements were not made when snow covered the ground. Soda lime results underestimated high fluxes and overestimated low fluxes as compared with IRGA data collected in 1994. All soda lime collected data (1991-1994) have been corrected to IRGA-based numbers, according to the relationship between IRGA- and soda lime-measured fluxes in 1994.

Infrared Gas Analyzer (IRGA). In 1994, soil respiration data was collected with an IRGA (LI-COR model 6262) in addition to the soda lime measurements. The IRGA was fitted with a pump and chamber to create a closed-loop system. Measurements were made twice daily at the times of minimum and maximum flux (morning and afternoon). The two measurements were averaged to obtain daily soil CO2 flux. All soil respiration data from 1995 on were collected only with the IRGA.

Description of data. Average daily fluxes for each plot, expressed as mg CO2-C/m2/day, for each collection date.

**Organization:**Harvard Forest. 324 North Main Street, Petersham, MA 01366, USA. Phone (978) 724-3302. Fax (978) 724-3595.**Project:**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. (ROR).**Funding:**National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.**Use:**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.**License:**Creative Commons Zero v1.0 Universal (CC0-1.0)**Citation:**Frey S, Nadelhoffer K, Boone R, Bowden R, Lajtha K, Rousk J. 2023. DIRT Litter Manipulation Experiment at Harvard Forest since 1990. Harvard Forest Data Archive: HF007 (v.25). Environmental Data Initiative: https://doi.org/10.6073/pasta/192e7dd6acab3c325ebe2139ef314989.

### Detailed Metadata

**hf007-01: coarse woody debris**

- date: collection date
- plot: plot number
- block: block number
- cwd.mass: coarse woody debris mass, oven-dry weight (unit: gram / missing value: NA)
- cwd.per.m2: coarse woody debris density (unit: gramsPerSquareMeter / missing value: NA)
- cwd.per.ha: coarse woody debris density (unit: kilogramsPerHectare / missing value: NA)

**hf007-02: litterfall**

- date: collection date
- lf.1.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.2.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.3.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.4.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.5.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.6.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.7.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.8.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.9.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.10.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.11.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.12.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.13.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.14.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.15.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.16.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.17.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.18.iii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.19.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.20.ii: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)
- lf.21.i: litterfall mass by plot and block (unit: kilogramsPerHectare / missing value: NA)

**hf007-03: tree inventory**

- species: species name
- ba.1992: basal area of live trees by species, m2 tree basal area per m2 ground area in 1992 (unit: meterSquaredPerMeterSquared / missing value: NA)
- n.1992: number of live trees by species in 1992 (unit: number / missing value: NA)
- ba.2001: basal area of live trees by species, m2 tree basal area per m2 ground area in 2001 (unit: meterSquaredPerMeterSquared / missing value: NA)
- n.2001: number of live trees by species in 2001 (unit: number / missing value: NA)

**hf007-04: soil moisture**

- year: year collected
- doy: day of year (unit: nominalDay )
- soilm.2: soil moisture expressed as average cc H2O per cc soil - treatment 2X (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)
- soilm.c: soil moisture expressed as average cc H2O per cc soil - treatment C (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)
- soilm.ox: soil moisture expressed as average cc H2O per cc soil - treatment OX (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)
- soilm.t: soil moisture expressed as average cc H2O per cc soil - treatment T (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)
- soilm.tox: soil moisture expressed as average cc H2O per cc soil - treatment TOX (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)
- soilm.oa: soil moisture expressed as average cc H2O per cc soil - treatment O/A- (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)

**hf007-05: soil temperature**

- year: year collected
- doy: day of year (unit: nominalDay )
- soilt.1a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.2a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.3a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.4a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.5a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.6a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.7a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.8a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.9a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.10a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.11a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.12a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.13a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.14a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.15a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.16a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.17a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.18a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.19a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.20a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.21a: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.1b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.2b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.3b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.4b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.5b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.6b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.7b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.8b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.9b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.10b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.11b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.12b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.13b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.14b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.15b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.16b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.17b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.18b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.19b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.20b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.21b: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.1c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.2c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.3c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.4c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.5c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.6c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.7c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.8c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.9c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.10c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.11c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.12c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.13c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.14c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.15c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.16c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.17c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.18c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.19c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.20c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)
- soilt.21c: soil temperature. Probe denoted by plot number and depth: a = 5 cm, b = 15 cm, c = Onset datalogger (unit: celsius / missing value: NA)

**hf007-06: soil respiration**

- year: year flux data collected
- doy: day of year (unit: nominalDay )
- flux.2x.1: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.2x.2: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.2x.3: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.c.1: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.c.2: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.c.3: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.c.4: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.c.5: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.c.6: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.ox.1: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.ox.2: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.ox.3: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.t.1: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.t.2: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.t.3: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.tox.1: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.tox.2: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.tox.3: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.oa.1: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.oa.2: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)
- flux.oa.3: average daily soil CO2 efflux by treatment (2X, C, OX, T, TOX, O/A-less) and chamber/plot number (unit: milligramPerMeterSquaredPerHour / missing value: NA)

**hf007-07: root mass**

- plot: plot number
- fine10.avg: mean mass of fine tree roots at 0- 10 cm. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- fine10.se: standard error of fine tree root mass at 0 - 10 cm. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- fine10.n: number of samples - fine tree roots at 0 -10 cm (unit: number / missing value: NA)
- woody10.avg: mean mass of woody tree roots at 0- 10 cm. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- woody10.se: standard error of woody tree root mass at 0 - 10 cm. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- woody10.n: number of samples - woody tree roots at 0 - 10 cm (unit: number / missing value: NA)
- herb10.avg: mean mass of herbaceous roots at 0- 10 cm. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- herb10.se: standard error of herbaceous root mass at 0 - 10 cm. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- herb10.n: number of samples - herbaceous roots at 0 - 10 cm (unit: number / missing value: NA)
- fine15.avg: mean mass of fine tree roots at 10 - 15 cm. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- fine15.se: standard error of fine tree root mass at 10 - 15 cm. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- fine15.n: number of samples - fine tree roots at 10 - 15 cm (unit: number / missing value: NA)
- woody15.avg: mean mass of woody tree roots at 10 - 15 cm. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- woody15.se: standard error of woody tree root mass at 10 - 15 cm. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- woody15.n: number of samples - woody tree roots at 10 - 15 cm (unit: number / missing value: NA)
- other15.avg: mean mass of roots not in fine tree or woody tree categories. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- other15.se: standard error of mean mass of roots not in fine tree or woody tree categories at 10 - 15 cm. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- other15.n: number of samples - roots not in fine tree or woody tree categories at 10 - 15 cm (unit: number / missing value: NA)
- fineo.avg: mean mass of fine tree roots in Oea soils. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- fineo.se: standard error of fine tree root mass in Oea soils. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- fineo.n: number of samples - fine tree roots in Oea soils (unit: number / missing value: NA)
- woodyo.avg: mean mass of woody tree roots in Oea soils. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- woodyo.se: standard error of woody tree root mass in Oea soils. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- woodyo.n: number of samples - woody tree roots in Oea soils (unit: number / missing value: NA)
- tubero.avg: mean mass of tuberous roots in Oea soils. Mean root mass per plot, category, and depth//horizon (unit: kilogramsPerHectare / missing value: NA)
- tubero.se: standard error of tuberous root mass in Oea soils. + 1 standard error of the mean, calculated as: [standard deviation (sample) of the mean /square root of n] (unit: number / missing value: NA)
- tubero.n: number of samples - tuberous roots in Oea soils (unit: number / missing value: NA)

**hf007-08: soil properties - 1990**

- date: date soils were collected
- type: source of sample
- Pit: pit
- Plot: plot

- num: pit or plot number (unit: number / missing value: NA)
- depth: depth or soil horizon
- avg.per.c: % soil C, average of replicates (unit: number / missing value: NA)
- se.per.c: standard error of the mean of % C (unit: number / missing value: NA)
- n.per.c: number of replicates (unit: number / missing value: NA)
- avg.per.n: % soil N, average of replicates (unit: number / missing value: NA)
- se.per.n: standard error of the mean of % N (unit: number / missing value: NA)
- n.per.n: number of replicates (unit: number / missing value: NA)

**hf007-09: soil properties 1991**

- date: date soils were collected
- plot: plot number
- treatment: treatment
- depth: depth or soil horizon
- ph: see method for pH (unit: number / missing value: NA)
- soil.mass: soil carbon and nitrogen content (unit: gramsPerSquareMeter / missing value: NA)
- se.soil.mass: standard error of soil carbon and nitrogen content (unit: gramsPerSquareMeter / missing value: NA)
- avg.per.c: % soil C, average of replicates (unit: dimensionless / missing value: NA)
- se.per.c: standard error of the mean of % C (unit: dimensionless / missing value: NA)
- avg.per.n: % soil N, average of replicates (unit: dimensionless / missing value: NA)
- se.per.n: standard error of the mean of % N (unit: dimensionless / missing value: NA)
- avg.d.15n: average d 15 nitrogen, expressed as positive or negative deviation from the atmospheric standard (unit: dimensionless / missing value: NA)
- sem.d.15n: sem of d 15 nitrogen (unit: dimensionless / missing value: NA)
- avg.d.13c: average of d 13 carbon, expressed as positive or negative deviation from the PDB standard (unit: dimensionless / missing value: NA)
- sem.d.13c: sem of of d 13 carbon (unit: dimensionless / missing value: NA)

**hf007-10: soil properties - 1995**

- samp: unique sample number
- depth: depth or horizon
- Oea: Oea organic horizon
- 0-10 cm: 0-10 cm mineral soil

- treatment: treatment (2X, C, OX, T, TOX, O/A-less)
- plot: plot number
- rep: replicate sample from plot
- db.0to10: bulk density (unit: gramsPerCubicCentimeter / missing value: NA)
- soild: soil weight per meter squared. Used sample weight to calculate mass/area for Oea soils, because Db was not measured directly. Mineral soil: soil mass is calculated as Db * 105 (unit: kilogramsPerSquareMeter / missing value: NA)
- ashfree.dw.per: % ash-free dry weight (unit: number / missing value: NA)
- ashfreec.est.per: estimated % ash-free % carbon; calculated as (% ash free dry weight)/2 (unit: number / missing value: NA)
- c.per: % C determined by Elemental Analyzer (unit: number / missing value: NA)
- n.per: % N determined by Elemental Analyzer (unit: number / missing value: NA)
- c.n: ratio of %C/%N (unit: number / missing value: NA)
- soil.c: soil carbon content, g C per m2 ground area (unit: gramsPerSquareMeter / missing value: NA)
- soil.n: Soil nitrogen content, g N per m2 ground area (unit: gramsPerSquareMeter / missing value: NA)
- exch.ca: exchangeable calcium, centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- exch.mg: exchangeable magnesium, centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- exch.k: exchangeable potassium, centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- exch.na: exchangeable sodium, centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- exch.bases: sum of exchangeable cations, centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- exch.al: exchangeable aluminum, centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- exch.h: exchangeable acidity (H+), centimoles of charge per kg dry weight soil (unit: centimolePerKilogram / missing value: NA)
- total.acidity: exchangeable acidity + exchangeable aluminum (unit: centimolePerKilogram / missing value: NA)
- cec: sum of exchangeable bases and acidity (unit: centimolePerKilogram / missing value: NA)
- base.sat: (Exchangeable bases* 100)/CEC (unit: number / missing value: NA)
- ph: see method for pH (unit: number / missing value: NA)
- h: [H+],the inverse log of pH (unit: number / missing value: NA)

**hf007-11: soil properties - 2000**

- type: sample type
- treatment: treatment
- plot: plot number
- rep: replicate sample from plot
- horizon: depth or horizon
- Oea: Oea organic horizon
- 0-10cm: 0-10 cm mineral soil

- c.per: % C corrected for 105 deg soil wt (unit: number / missing value: NA)
- n.per: % N corrected for 105 deg soil wt (unit: number / missing value: NA)

**hf007-12: plot key**

- plot: plot number
- treatment: treatment
- block: block number
- description: treatment description