uid=HFR,o=lter,dc=ecoinformatics,dc=org
all
public
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doi:10.6073/pasta/c9c607f39797fd87bd275dac95a8ab02
Extracellular Enzyme Activity in Rhizosphere Soil at Harvard Forest and Pisgah State Forest 2010
Edward
Brzostek
https://orcid.org/0000-0002-2964-0576
Adrien
Finzi
https://orcid.org/0000-0003-2220-4533
John
Drake
Researcher
Allison
Greco
Researcher
2023
English
The exudation of carbon (C) by tree roots stimulates microbial activity and the production of extracellular enzymes in the rhizosphere. Here, we investigated whether the strength of rhizosphere processes differed between temperate forest trees that vary in soil organic matter (SOM) chemistry and associate with either ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi. We measured rates of microbial and extracellular enzyme activity, and nitrogen (N) availability in samples of rhizosphere and bulk soil influenced by four temperate forest tree species (i.e., to estimate a rhizosphere effect). The magnitude of the rhizosphere effects could not be easily characterized by mycorrhizal associations or SOM chemistry. Ash had the lowest rhizosphere effects and beech had the highest rhizosphere effects, representing one AM and one ECM species, respectively. Hemlock and sugar maple had equivalent rhizosphere effects on enzyme activity. However, the form of N produced in the rhizosphere varied with mycorrhizal association. Enhanced enzyme activity primarily increased amino acid availability in ECM rhizospheres and increased inorganic N availability in AM rhizospheres. These results show that the exudation of C by roots can enhance extracellular enzyme activity and soil-N cycling. This work suggests that global changes that alter belowground C allocation have the potential to impact the form and amount of N to support primary production in ECM and AM stands.
amino acids
microbes
mycorrhizae
nitrogen
rhizosphere
soil water content
LTER controlled vocabulary
organic matter
LTER core area
Harvard Forest
HFR
LTER
USA
HFR default
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.
Creative Commons Zero v1.0 Universal
https://spdx.org/licenses/CC0-1.0.html
CC0-1.0
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf251
Prospect Hill Tract (Harvard Forest), Pisgah State Forest (NH). Coordinates based on WGS84 datum.
-72.45
-72.18
+42.87
+42.50
2008
2010
genus
Acer
species
saccharum
sugar maple
genus
Fagus
species
grandifolia
american beech
genus
Fraxinus
species
americana
white ash
genus
Quercus
species
rubra
red oak
genus
Tsuga
species
canadensis
eastern hemlock
complete
Information Manager
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
hf-im@lists.fas.harvard.edu
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
(978) 724-3595
https://harvardforest.fas.harvard.edu
Site Description
This research was conducted at two sites, the Harvard Forest and the Pisgah State Forest. The sites have similar land use history and stand age. Soils at both sites are inceptisols classified as Typic Dystrochrepts derived from glacial till overlying granite-schist-gneiss bedrock. Study plots dominated by one of five target tree species were identified at each site. Plots of sugar maple (Acer saccharum) and American beech (Fagus grandifolia) were located in Pisgah State Forest. Plots of eastern hemlock (Tsuga canadensis), red oak (Quercus rubra), and white ash (Fraxinus americana) were located in the Harvard Forest. These species differed in mycorrhizal association, with ash and sugar maple supporting AM fungi and hemlock and beech supporting ECM fungi. Further, hemlock and beech have recalcitrant leaf litter and SOM that is characterized by higher ratios of C-to-N and lower pH than sugar maple and ash. At each site we located six replicate, 8-m radius, monodominant plots within larger mixed hardwood/conifer stands where the target tree species constituted 100 % of standing basal area in the inner 5-m core and 80 % in the entire 8-m radius plot.
Soil Sampling Protocol
Soil samples were collected in May, June, and August of 2010 from each of the six replicate plots for each species. We chose the May, June and August time-points because they span the majority of the growing season and are coincident with major phenological events, including leaf out, peak leaf area index, and the start of the seasonal decline in C uptake at the Harvard Forest, respectively. At each sampling point, we collected the top 15 cm of mineral soil using a 5-cm diameter soil bulk-density sampler from each plot. The samples were processed in the laboratory within 24 h of collection. We separated the mineral soil horizons into rhizosphere and bulk soil fractions. Fine roots were removed from each sample. Soil adhering to fine roots was operationally classified as rhizosphere soil.The remaining soil was defined as the bulk soil fraction. After separation, the bulk soil fraction was then sieved through a 2-mm mesh.
Amino Acid Concentrations
The 2 M KCl extractable pool size of amino acids was determined for every soil sample across the three sampling dates. Eight grams of each mineral soil fraction were extracted in 30 mL of 2 M KCl. The concentration of amino acids for all extracts was quantified using the o-phthaldialdehyde and b-mercaptoethanol (OPAME) method. Concentrations of amino acid N were determined by comparing the fluorescence of the samples relative to a standard curve composed of glycine.
Extracellular Enzyme Activity
We assayed proteolysis following a method modified from Watanabe and Hayano (1995) and Lipson et al. (1999) for every soil fraction and sample date. Initial and incubated subsamples (2–3 g) received 10 ml of a 0.5 mM sodium acetate buffer (pH 5.0) with a small volume of toluene (400 μL) added to inhibit microbial uptake. After the reagent addition, the initial samples were immediately terminated and the incubated subsamples were incubated at 23°C for 4 h. Enzyme activity in all the initial and incubated subsamples was terminated through the addition of 3 mL of a trichloroacetic acid solution. Proteolytic rates for each soil were calculated from the difference between amino acid concentrations in the incubated and initial subsamples of each soil assayed using the OPAME method. For every soil fraction at each sample date, we also assayed the potential activities of the chitinolytic enzyme, n-acetyl-glucosaminidase (NAG) and acid phosphatase and the lignolytic enzymes, phenol oxidase and peroxidase. All the assays were run using a 1 g subsample of each soil homogenized in a pH 5.0 sodium acetate buffer at 23°C. NAG and acid phosphatase activities were determined using a fluorometric microplate assay, while phenol oxidase and peroxidase activities were determined using a colorimetric microplate assay.
Soil Moisture
Subsamples of fresh soils (5-10g) were weighed and then dried in an oven at 60°C for 48 hours to determine soil moisture content.
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.
hf251-01-soil-moisture.csv
soil moisture
hf251-01-soil-moisture.csv
1964
d0b46ca1b6ccb50d257f68c89d915011
1
\r\n
column
,
https://harvardforest.fas.harvard.edu/data/p25/hf251/hf251-01-soil-moisture.csv
species
tree species
ACSA
sugar maple
FAGR
American beech
FRAM
white ash
TSCA
eastern hemlock
NA
missing value
horizon
soil horizon
B
mineral soil (bulk)
O
organic horizon
NA
missing value
site
site
site
NA
missing value
year
year of measurement
YYYY
1 year
NA
missing value
may.avg
soil moisture content measured in May, average of 6 plots
(%)
dimensionless
0.00000001
real
NA
missing value
may.se
standard error on soil moisture content average of 6 plots, measured
in May (%)
dimensionless
0.000000001
real
NA
missing value
june.avg
soil moisture content measured in June, average of 6 plots
(%)
dimensionless
0.00000001
real
NA
missing value
june.se
standard error on soil moisture content average of 6 plots, measured
in June (%)
dimensionless
0.000000001
real
NA
missing value
august.avg
soil moisture content measured in August, average of 6 plots
(%)
dimensionless
0.00000001
real
NA
missing value
august.se
standard error on soil moisture content average of 6 plots, measured
in August (%)
dimensionless
0.000000001
real
NA
missing value
18
hf251-02-enzyme-activity.csv
enzyme activity
hf251-02-enzyme-activity.csv
23331
a1e1d333dfaf5114fdf4049f79eb0061
1
\r\n
column
,
https://harvardforest.fas.harvard.edu/data/p25/hf251/hf251-02-enzyme-activity.csv
year
year of sampling
YYYY
1 year
NA
missing value
month
month of sampling
month of sampling
NA
missing value
site
site
site
NA
missing value
species
tree species
ASCA
sugar maple
FAGR
American beech
FRAM
white ash
TSCA
eastern hemlock
QURU
red oak
NA
missing value
plot
plot number
plot number
NA
missing value
soil
soil
B
mineral soil (bulk)
O
organic horizon
R
mineral soil (rhizosphere)
NA
missing value
proteolysis
proteolysis, the rate of protein depolymerization into free amino
acids (converted to μg amino-acid-N/g dry soil/per hour)
microgramPerGramPerHour
0.000000001
real
NA
missing value
aa
extractable amino acid concentration
microgramsPerGram
0.000000001
real
NA
missing value
nag
b-N-acetylglucosaminidase activity
micromolePerGramPerHour
0.000000001
real
NA
missing value
ap
acid phosphatase activity
micromolePerGramPerHour
0.000000001
real
NA
missing value
phenox
phenol oxidase activity
micromolePerGramPerHour
0.000000001
real
NA
missing value
perox
peroxidase activity
micromolePerGramPerHour
0.000000001
real
NA
missing value
234
soil
short-term measurement
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf180