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hbr0197
Microbial Biomass Climate Gradient
Long-term measurements of microbial biomass and activity at the Hubbard Brook Experimental Forest, climate gradient plots, 2010-2012
Peter M.
Groffman
Cary Institute of Ecosystem Studies
Box AB
Millbrook
NY
12545
USA
GroffmanP@caryinstitute.org
Hubbard Brook Experimental Forest
LTER
234 Mirror Lake Road
North Woodstock
NH
03262
USA
Phone: (603) 726-8902
http://hbrook-dev.sr.unh.edu
Lisa
Martel
associated researcher
Jorge
Duran
associated researcher
Charles
Driscoll
associated researcher
Timothy
Fahey
associated researcher
Melany
Fisk
associated researcher
Lynn
Christenson
associated researcher
Natalie
Cleavitt
associated researcher
Pamela
Templer
associated researcher
2018
Long-term monitoring of soil nitrate (NO3-) and ammonium (NH4+)
concentrations, microbial biomass carbon (C) and nitrogen (N) content,
microbial respiration, potential nitrification and N mineralization
rates, and denitrification potential has been ongoing at the Hubbard
Brook Experimental Forest since 1994. Samples have been collected in the
Bear Brook Watershed (west of Watershed 6) beginning in 1994. In 1998,
our sampling regime was extended to Watershed 1 in an effort to monitor
and quantify microbial response to a whole-watershed calcium addition.
ammonium
carbon
denitrification
HBEF Watershed 1
HBEF Bear Brook Watershed
HBR
Hubbard Brook LTER
microbe
microbial biomass
mineralization
nitrate
nitrification
nitrogen
respiration
soil
Hubbard Brook Ecosystem Study LTER
inorganic nutrients
primary production
LTER Core Research Areas
Data from 1994-1996 have been published (Bohlen et al.
2001), data from 2001 are published in Fiorentino et al. (2003),
data from 1998 – 2003 comparing the Ca treated watershed (watershed
1) and the long-term sites “west of watershed 6” are published in
Groffman et al. (2006). Other data will be published in manuscripts
that are currently in preparation by the investigators. Other
Hubbard Brook microbial biomass and activity data can be found in
Groffman et al. (2001, 2010). People are free to use these data for
informational purposes but they cannot be used in any publication
without permission of the author. Contact Linda Pardo (USDA Forest
Service, PO Box 968, Burlington, VT 05402; 802-951-6771 x1330;
lpardo@fs.fed.us) for questions about, and before using, all 1997
data.
Data Use Policy
The re-use of scientific data has the potential to greatly
increase communication, collaboration and synthesis within and
among disciplines, and thus is fostered, supported and
encouraged. Permission to use this dataset is granted to the
Data User free of charge subject to the following terms:
1) Acceptable use. Use of the dataset will be restricted to
academic, research, government or other not-for-profit
professional purposes.
2) Redistribution. The data and metadata are provided for
use by the Data User. The Data User will not redistribute the
original Data Set or metadata to others without the explicit
permission of the Principal Investigator.
3) Citation. It is considered a matter of professional
ethics to acknowledge the work of other scientists. Thus, the
Data User will properly attribute the Data Set in any
publications or in the metadata of any derived data products
that were produced using the Data Set. Citation should take the
following general form: Creator, Year of Data Publication, Title
of Dataset, Publisher, Dataset identifier.
Citation example: Holmes, R.T. 2012. Bird Abundances at
Hubbard Brook (1969-2010) and on three replicate plots
(1986-2000) in the White Mountain National Forest. Durham, NH.
Hubbard Brook Data Archive [Database].
http://data.hubbardbrook.org/data/dataset.php?id=81 (23 July 2012)
4) Acknowledgment: The Data User should acknowledge any
institutional support or specific funding awards referenced in
the metadata accompanying this dataset in any publications where
the Data Set contributed to its content. Acknowledgments should
identify the supporting party, the party that received the
support, and any identifying information such as grant
numbers.
Acknowledgment example: Data on [topic] were provided by
[name of PI] on [date]. These data were gathered as part of the
Hubbard Brook Ecosystem Study (HBES). The HBES is a
collaborative effort at the Hubbard Brook Experimental Forest,
which is operated and maintained by the USDA Forest Service,
Northern Research Station, Newtown Square, PA. Significant
funding for collection of these data was provided by
[agency]-[grant number], [agency]-[grant number], etc.
5) Consultation and questions. Data users are strongly
encouraged to consult with the Principal Investigator(s) who
collected these data for further information. Also, when
appropriate, Data Users should consider including the Principal
Investigator as a collaborator and/or co-author in the use of
these data.
6) Notification. The Data User will notify the Principal
Investigator of any publication or derivative work based on the
Data Set. The Data User will also provide the Principal
Investigator and/or the administrator of the Hubbard Brook
Ecosystem Study with a pdf or two reprints of any publication(s)
resulting from use of the Data Set.
7) Disclaimer. While substantial efforts are made to ensure
the accuracy of data and documentation contained in this Data
Set, complete accuracy of data and metadata cannot be
guaranteed. All data and metadata are made available "as is".
The Data User holds all parties involved in the production or
distribution of the Data Set harmless for damages resulting from
its use or interpretation.
8) Terms of Agreement. By accepting this Data Set, the Data
User agrees to abide by the terms of this agreement. The Data
Owner shall have the right to terminate this agreement
immediately by written notice upon the Data User's breach of, or
non-compliance with, any of its terms. The Data User may be held
responsible for any misuse that is caused or encouraged by the
Data User's failure to abide by the terms of this agreement.
http://data.hubbardbrook.org/data/dataset.php?id=197
IL1: Intensive Low Elevation Plot 1. Aspect:
South. UTM: X= 282144, Y= 4869478
-71.71479424
-71.71479424
43.94617659
43.94617659
375
375
meter
IL2: Intensive Low Elevation Plot 2. Aspect:
South. UTM: X= 281685, Y= 4869704
-71.72060047
-71.72060047
43.94807308
43.94807308
401
401
meter
IL3: Intensive Low Elevation Plot 3. Aspect:
South. UTM: X= 280887, Y= 4869966
-71.73064174
-71.73064174
43.95019236
43.95019236
511
511
meter
IH1: Intensive High Elevation Plot 1. Aspect:
North. UTM: X= 277790, Y= 4868286
-71.7684914
-71.7684914
43.93415543
43.93415543
539
539
meter
IH2: Intensive High Elevation Plot 2. Aspect:
North. UTM: X= 277888, Y= 4868064
-71.76717913
-71.76717913
43.93218854
43.93218854
555
555
meter
IH3: Intensive High Elevation Plot 3. Aspect:
North. UTM: X= 278314, Y= 4867892
-71.76180633
-71.76180633
43.93077007
43.93077007
595
595
meter
E1: Extensive Plot 1. Aspect: North. UTM:
X=277410, Y=4867546
-71.77291084
-71.77291084
43.92738579
43.92738579
588
588
meter
E2: Extensive Plot 2. Aspect: North. UTM: X=
277111, Y= 4867074
-71.77643367
-71.77643367
43.92305067
43.92305067
687
687
meter
E3: Extensive Plot 3. Aspect: North. UTM: X=
276485, Y= 4850906
-71.77745584
-71.77745584
43.91985666
43.91985666
770
770
meter
E4: Extensive Plot 4. Aspect: North. UTM: X=
277986, Y= 4867455
-71.76570567
-71.76570567
43.92674122
43.92674122
632
632
meter
E5: Extensive Plot 5. Aspect: North. UTM: X=
278055, Y= 4866940
-71.76463237
-71.76463237
43.92213059
43.92213059
724
724
meter
E6: Extensive Plot 6. Aspect: North. UTM: X=
281632, Y= 4870329
-71.72151804
-71.72151804
43.95368099
43.95368099
536
536
meter
E7: Extensive Plot 7. Aspect: South. UTM: UTM: X=
281869, Y= 4870458
-71.71862125
-71.71862125
43.95490408
43.95490408
609
609
meter
E8: Extensive Plot 8. Aspect: South. UTM: X=
281785, Y= 4870899
-71.71984434
-71.71984434
43.95885229
43.95885229
630
630
meter
E9: Extensive Plot 9. Aspect: South. UTM: X=
281650, Y= 4871108
-71.72161276
-71.72161276
43.96068944
43.96068944
670
670
meter
E10: Extensive Plot 10. Aspect: South. UTM: X=
281068, Y= 4870840
-71.72874928
-71.72874928
43.95810127
43.95810127
698
698
meter
E11: Extensive Plot 11. Abandonded in Fall 2011
and replaced with 11-B. Aspect: South. UTM: X= 279820, Y=
4870325
-71.74407265
-71.74407265
43.95310239
43.95310239
706
706
meter
E11-B: Extensive Plot 11-B. Replacement for E11
started in Fall 2011. Aspect: South. UTM: X= 279957, Y=
4870590
-71.74247222
-71.74247222
43.95552778
43.95552778
766
766
meter
E12: Extensive Plot 12. Aspect: South. UTM: X=
290093, Y= 4870317
-71.74066667
-71.74066667
43.95311111
43.95311111
688
688
meter
E13: Extensive Plot 13. Aspect: South. UTM: X=
280252, Y= 4870034
-71.73857446
-71.73857446
43.95061447
43.95061447
601
601
meter
E14: Extensive Plot 14. Aspect: South. UTM: X=
281277, Y= 4870177
-71.72587194
-71.72587194
43.95220301
43.95220301
487
487
meter
2010-11-19
2012-08-07
Information Manager, Hubbard Brook LTER
234 Mirror Lake Road
North Woodstock
NH
03262
USA
(603) 726-8902
hbr-im@lternet.edu
http://hbrook-dev.sr.unh.edu
Hubbard Brook Experimental Forest
LTER
234 Mirror Lake Road
North Woodstock
NH
03262
USA
(603) 726-8902
http://hbrook-dev.sr.unh.edu
Hubbard Brook LTER
LOCATION DESCRIPTION
We have initiated a long-term effort to monitor
soil nitrate (NO3-) and ammonium (NH4+) concentrations,
microbial biomass carbon (C) and nitrogen (N) content, microbial
respiration, potential nitrification and N mineralization rates,
and denitrification potential in the experimental watersheds at
Hubbard Brook. In 1994 we began sampling in the Bear Brook
Watershed (west of Watershed 6). In 1998, we added Watershed 1
to our sampling regime in an effort to monitor and quantify
microbial response to a whole-watershed calcium addition
(http://www.hbrook.sr.unh.edu/current/new_current.htm).
In the Bear Brook Watershed we used the “west of
watershed 6 litter trap transects” described by Hughes and Fahey
(1994). These are four 100 m transects, 50 m apart with five
traps per transect located at low, mid, upper and high
elevations - 20 traps per elevation. We sampled within 1.5 m of
five traps at each elevation. Litter quality, quantity and
composition have been monitored on these transects since 1984.
In 1997 we sampled at the upper and high elevations and also at
four locations just above and to the west of Rain Gauge 9 in a
mixed stand dominated by red spruce and balsam fir. In 1998 we
began regularly sampling more extensively in the spruce/fir
zone, and discontinued our sampling at the "upper" site. We
sampled within 1.5 m of the center of each of 5 randomly chosen
sites in this spruce/fir area. Vegetation in the Bear Brook
Watershed is roughly equivalent to that in Watershed 6, which is
an approximately 80 year old “reference” watershed dominated by
northern hardwoods (American beech, sugar maple, yellow birch)
at the lower elevations with moderate amounts of red spruce,
balsam fir and white birch at the “high” elevation sites.
In Watershed 1 we sampled near a subset of the
lysimeter sites established for the calcium addition study. Our
sites included the "spruce/fir" Lysimeter Site 2 at the top of
Watershed 1, the "high" Lysimeter Site 3, the "mid" Lysimeter
Site 4, and the "low" Lysimeter Site 6. These site types and
elevations correspond to those in the Bear Brook Watershed. At
each lysimeter site we chose 5 replicate plots that were all
within ~30 m of the center lysimeter stake. We revisited the
same approximate plot during each sampling date. In 1999 we
marked out 2 X 3 m plots in these areas, covered them during the
helicopter wollastonite addition, then uncovered them and
hand-applied wollastonite. We have sampled entirely within these
marked plots since the application.
SAMPLING DESIGN
Samples were collected three times each year (note
the above exceptions) to correspond with key plant phenological
stages: pre-green, peak green, and senescence. Sampling dates
were generally in May, July, and October. We also sampled once
in December 1999, two months after the wollastonite addition, to
determine if there were immediate responses to the calcium. In
1994, May and July 1995, May and July 1996, and from July 1998
to July 1999 we sampled soils using a bulb corer method. In
October 1995 and 1996, all of 1997, and in May 1998 we used a
pin block method. From May 2000 to 2010 we sampled using a
split-PVC corer method.ay 2000 on we have sampled using a
split-PVC corer method.
In the pin block method, long (13.2 cm) nails are
driven through holes along the edge of a 15 X 15 cm square of ~1
cm plywood that has been placed on the forest floor. There are 4
holes on each side of the pin block. These nails firmly attach
the block to the soil, and enclose a "box" of soil for sampling.
We use a small saw to cut away roots and soil from the edge of
the nails and from underneath the block. We then remove the soil
contained by the block and the nails (15 X 15 X 13.2 cm). In
1997 Oe and Oa were collected as a single horizon, and mineral
soil was discarded. In other years we separated the organic soil
into two layers (Oi/Oe and Oa/A horizons), discarded the mineral
soil from the pin block, and used a bulb corer to take a 10 cm
mineral core directly under the (removed) soil block.
In the bulb corer method, a typical flower planting
and gardening bulb corer is used. These corers are metal, have a
handle on top, and have a diameter that gets slightly narrower
from top to bottom. The diameter at the bottom of the corer we
used is 6.5 cm. Typically, anywhere from 2-8 cores are taken at
a given site, depending on horizon depth and density of soils.
The corer is inserted 10 cm into the soil and removed with an
intact core. The core is pushed out through the top of the corer
onto a plastic sheet, where horizon depths are noted and
horizons are separated. The mineral soil is discarded and the
remaining soil is split into two layers (Oi/Oe and Oa/A
horizons). Each layer is measured and placed into a sample bag,
with all cores composited by horizon. To obtain a mineral sample
we dig down to the first sign of mineral soil (E or B, depending
on the site) and attempt to take a full 10 cm core. If it is not
possible to obtain a full 10 cm mineral core we take 2-3 partial
mineral cores and combine them.
In the split-PVC corer method, a 5 cm diameter
split PVC corer is used to take all samples. A split PVC corer
consists of a piece of 2 inch (5 cm) PVC pipe, about 15-20 cm
long, split lengthwise on both sides. The corer is actually in
two pieces. We put the corer together along the cuts, and
duct-tape one side -- the "hinge" side. Holding the corer firmly
together, we hammer it 10-15cm into the ground. The corer is
removed and then opened with the intact soil core inside. The
soil is split into three layers (Oi/Oe, Oa/A, and mineral
horizons). Each horizon is measured and placed into a sample
bag. We typically collect 2-8 cores per site, compositing all
cores by horizon.
DATA DESCRIPTION
In most cases, Oi and Oe horizons were composited
into one sample, as were Oa and A horizons. Mineral samples
generally consist of the top 10 cm of mineral soil beginning
below the A horizon. In 1994 and May and July 1995, only Oi/Oe
and Oa/A horizons were sampled. In 1997 only Oe and Oa horizons
were collected, and they were composited into one sample.
Samples are either collected once (July) or three times a year
(May, July, and October). Samples were also collected in
December 1999.
NOTE ON OUTLIERS IN THE DATA SET
All outliers were left in the data set unless it
was evident that there was a contamination or laboratory
procedure problem. In 2005, at the W1 high site, rep 3 of the
Oi/Oe sample had biomass C, Respiration, Biomass N,
Nitrification, Mineralization and DEA that were values that
were, in some cases, 10 times higher than the next highest
value. It was determined that since this pattern was evident in
multiple lab analyses it was not due to laboratory errors, and
must represent a "hot spot" of activity in the soil. These data
were left in the dataset. In 2001, at the Bear Brook high
elevation site, the mineral horizon had extremely high NH4
levels. This mean is the result of 5 data points, 2 of which
were very high. These data were also left in the dataset.
LABORATORY PROCEDURES
Samples were stored at 4o C between sampling and
analysis (from less than 1 week to up to three weeks). From 1994
to 1996 soils were sieved (>4 mm). From 1997 to 2010 soils were
manually homogenized: all large rocks, roots, and other
non-decomposed organic material were removed, and samples were
thoroughly mixed. No more than three minutes were spent
homogenizing any sample. All samples were held at field moisture
before analysis. Soil water content was determined
gravimetrically.
Microbial biomass C and N content was measured
using the chloroform fumigation-incubation method (Jenkinson and
Powlson 1976). Soils were fumigated to kill and lyse microbial
cells in the sample. The fumigated sample was inoculated with
fresh soil and sealed in a jar, and microorganisms from the
fresh soil grew vigorously using the killed cells as substrate.
The flushes of carbon dioxide (CO2) and 2 M KCl extractable
inorganic N (NH4+ and NO3-) released by the actively growing
cells during a 10-day incubation at field moisture content were
assumed to be directly proportional to the amount of C and N in
the microbial biomass of the original sample. A proportionality
constant (0.41) was used to calculate biomass C from the CO2
flush in the fumigated samples. Biomass N is the total inorganic
N flush in the fumigated samples.
Inorganic N and CO2 production were also measured
in "control" samples. Control samples were prepared in the same
fashion as those listed above, but were not fumigated. These
incubations provided estimates of microbial respiration and
potential net N mineralization and nitrification. Microbial
respiration was quantified from the amount of CO2 evolved over
the 10-day incubation. Potential net N mineralization and
nitrification were quantified from the accumulation of NH4+ plus
NO3- and NO3- alone during the 10-day incubation. We measured 2
M KCl extractable inorganic N in the fresh soil samples to
determine the initial soil NO3- and NH4+ concentrations. Carbon
dioxide was measured by thermal conductivity gas chromatography.
Inorganic N was measured colorometerically using an
autoanalyzer.
Denitrification enzyme activity was measured using
the short-term anaerobic assay described by Smith and Tiedje
(1979). Sieved soils were amended with NO3- (100 mg N kg-1),
dextrose or glucose (40 mg kg-1), chloramphenicol (10 mg kg-1)
and acetylene (10 kPa) and were incubated under anaerobic
conditions for 90 minutes. Gas samples were taken at 30 and 90
minutes, stored in evacuated glass tubes and analyzed for N2O by
electron capture gas chromatography. For more information on any
of the methods described above, refer to Standard Soil Methods
for Long-Term Ecological Research (1999).
CALCULATIONS
All results are expressed on a per gram of dry soil
basis. Values can be converted to a “per area” basis using data
on the mass of different soil horizons found elsewhere on the
data page of this website.
Plant-soil-microbial interactions in a northern hardwood
forest
P.J.
Bohlen
P.M.
Groffman
C.T.
Driscoll
T.J.
Fahey
T.G.
Siccama
2001
english
Ecology
82
965-978
Initial responses of phosphorus biogeochemistry to calcium
addition in a northern hardwood forest ecosystem
I.
Fiorentino
T.
Fahey
P.
Groffman
C.
Driscoll
C.
Eagar
T.
Siccama
2003
Can. J. For. Res.
33
1864-1873
Effects of mild winter freezing on soil nitrogen and carbon
dynamics in a northern hardwood forest
P.M.
Groffman
C.T.
Driscoll
T.J.
Fahey
J.P.
Hardy
R.D.
Fitzhugh
G .L.
Tierney
2001
english
Biogeochemistry
56
191-213
Climate variation and nitrogen and carbon cycle processes in a
northern hardwood forest
P.M.
Groffman
J.P.
Hardy
M.C.
Fisk
T.J.
Fahey
C.T.
Fahey
2009
english
Ecosystems
12
927-943
Calcium additions reduce nitrogen cycling in a northern
hardwood forest
P.
Groffman
M.
Fisk
C.
Driscoll
G.
Likens
T.
Fahey
C.
Eagar
L.
Pardo
2006
Ecosystems
9
1289-1305
Litterfall dynamics and ecosystem recovery during forest
development
J.W.
Hughes
T.J.
Fahey
1994
Forest Ecology and Management
63
181-198
The effects of biocidal treatments on metabolism in soil V. A
method for measuring soil biomass
D.S.
Jenkinson
D.S.
Powlson
1976
Soil Biology and Biochemistry
8
209-213
Soil Microbiology and Biochemistry
E.A.
Paul
F.E.
Clark
1996
Academic Press
New York
2nd Edition
Standard Soil Methods for Long-Term Ecological Research
G.P.
Robertson
D.C.
Coleman
C.S.
Bledsoe
P.
Sollins
1999
Oxford University Press
New York
Phases of denitrification following oxygen depletion in
soil
M.S.
Smith
J.M.
Tiedje
1979
Soil Biology and Biochemistry
11
262-267
Determination of kc and kn in situ for calibration of the
chloroform fumigation-incubation method
R.P.
Voroney
E.A.
Paul
1984
Soil Biology and Biochemistry
16
9-14
micbio_snowgradient
Microbial biomass and activity at the Hubbard Brook
LTER site, Snow Gradient plots.
micbio_snowgradient.txt
ASCII
1
0
\r\n
column
0x2c
http://data.hubbardbrook.org/data/data_policy.php?target=micbio_snowgradient.txt
uid=HBR,o=LTER,dc=ecoinformatics,dc=org
all
public
read
DATA DESCRIPTION
Data from 1994-1996 have been published (Bohlen et
al. 2001), data from 2001 are published in Fiorentino et al.
(2003), data from 1998 – 2003 comparing the Ca treated watershed
(watershed 1) and the long-term sites “west of watershed 6” are
published in Groffman et al. (2006). Other data will be published
in manuscripts that are currently in preparation by the
investigators. Other Hubbard Brook microbial biomass and activity
data can be found in Groffman et al. (2001, 2010). People are free
to use these data for informational purposes but they cannot be
used in any publication without permission of the author. Contact
Linda Pardo (USDA Forest Service, PO Box 968, Burlington, VT
05402; 802-951-6771 x1330; lpardo@fs.fed.us) for questions about,
and before using, all 1997 data. The data is physically located at
the Cary Institute of Ecosystem Studies in Millbrook, NY
Project
Project Name
SnowGradient
Snow Gradient plots
Date
Sample date
YYMMDD
1 day
941014
Year
Year
YYYY
1 year
1994
Season
Season sample collected
F
Fall
W
Winter
SP
Spring
SU
Summer
Treatment
Plot treatment
NA
not applicable
Elevation
Elevation
meter
1
integer
-999
Data missing or not taken at this time
Sample
Sample location
IL1
Intensive Low Elevation Plot 1
IL2
Intensive Low Elevation Plot 2
IL3
Intensive Low Elevation Plot 3
IH1
Intensive High Elevation Plot 1
IH2
Intensive High Elevation Plot 2
IH3
Intensive High Elevation Plot 3
E1
Extensive Plot 1
E2
Extensive Plot 2
E3
Extensive Plot 3
E4
Extensive Plot 4
E5
Extensive Plot 5
E6
Extensive Plot 6
E7
Extensive Plot 7
E8
Extensive Plot 8
E9
Extensive Plot 9
E10
Extensive Plot 10
E11
Extensive Plot 11
E11-B
Extensive Plot 11-B
E12
Extensive Plot 12
E13
Extensive Plot 13
E14
Extensive Plot 14
Horizon
Soil horizon
Oi/Oe
Oi and Oe horizons combined
Oa/A
Oa and A horizons combined
O
The entire O horizon: Oi, Oe, and Oa combined
Min
The first 10 cm of mineral soil below the A
horizon (E and/or B)
BIOC
Microbial biomass C
milligramPerKilogram
.01
real
-9999.99
Data missing or not taken at this time
RESPC
Soil respiration
milligramPerKilogramPerDay
.01
real
-9999.99
Data missing or not taken at this time
BION
Microbial biomass N
milligramPerKilogram
.01
real
-9999.99
Data missing or not taken at this time
NO3
Soil nitrate
milligramPerKilogram
.01
real
-9999.99
Data missing or not taken at this time
NH4
Soil ammonium
milligramPerKilogram
.01
real
-9999.99
Data missing or not taken at this time
NIT
Potential net nitrification
milligramPerKilogramPerDay
.01
real
-9999.99
Data missing or not taken at this time
MIN
Potential net N
mineralization
milligramPerKilogramPerDay
.01
real
-9999.99
Data missing or not taken at this time
DEA
Denitrification enzyme
activity
microgramPerKilogramPerHour
.01
real
-9999.99
Data missing or not taken at this time
H2O
Denitrification enzyme
activity
microgramPerKilogramPerHour
.01
real
-9999.99
Data missing or not taken at this time
A mass per mass per unit time measure of enzyme
activity
milligram of element per kilogram of
soil
Measure of a change in some soil property, such
as carbon concentration