MCSE: Aboveground Net Primary Productivity

Overview

Above ground net primary productivity (ANPP) is measured at the KBS LTER in habitats ranging from annual cropping systems to deciduous forests. The diverse plant communities in these habitats require different harvest and/or sampling methods. All measurements are taken pre-harvest at peak annual biomass for major community components. This generally means physiological maturity for annuals, prior to incorporation for cover crops, pre-senescence for perennials, and pre-harvest for alfalfa.

For Treatments 1, 2, 3, 4, 6, 7 and SF (successional field) ANPP is assessed by harvesting all the above ground portion of plants that are rooted within the bounds of the harvest quadrat. The quadrat size used typically totals 1 m² but the dimensions vary depending on the crop row spacing in the annual systems (T1-4) and are described in Table 1. The quadrat size for T6, 7, and SF is 0.5 by 2.0 m (1m²). Quadrats are oriented with the long side in an east – west direction. This direction is perpendicular to the crop rows (in planted systems) and allows for assessment of both the row and inter-row plant communities. All plants within the quadrat are clipped at ground level and either sorted to species in the field or bagged and stored at 4 degrees C until botanical separations are performed. Five letter codes are used to label non-woody species and six letter codes are used for woody species. The first three letters of the genus and first 2 or 3 letters of the species are typically used to create a unique code. In some cases plants are composited into crop and non crop plant components. Crops are further separated into seed and stover. Plants are dried at 60 degrees C for a minimum of 48 hours and dry weights recorded along with the date of harvest, field replicate, treatment, sampling station and species code.

In Treatment 5 (poplar plantation) biomass estimates are derived from measurements of basal diameter using an allometric relationship between diameter and biomass determined from a subset of harvested trees. In the DF (deciduous forest) and CF (conifer forest) plots, wood annual growth is estimated by changes in stem diameter using an allometric equation available in Tritton and Hornbeck (1982). Leaf production in sites with trees is estimated with five 0.5 × 0.95 m litter traps placed on the forest floor of each site.

Details for the ANPP estimates for all treatments are provided below.

Treatment 1, 2: Conventional, No tillage

Corn / Soybean / Wheat rotation.

Crop

Plants are hand harvested using a 1 m² quadrat (see Table 1) at each of the five sampling stations at physiological maturity of the crop:

• Corn : harvest (mid October).
• Soybeans : harvest (late September).
• Wheat: kernel entering dough stage (mid-July).

Plant tissue is dried and the total biomass of the plot is recorded. The tissue is then threshed (Almaco corn or small grain thresher) to separate the seed from stover. Seeds are dried at 60 ° C and the biomass is recorded. Seed and stover tissue sub samples are collected, combined by tissue type over stations, ground and archived for further analysis.

• Calculate the mean total, seed and stover biomass per plot on a dry weight basis.
• Report for ANPP: mean total biomass (g/m² /y) and standard error (SE) with n=6 reps (blocks).

Non crop plant biomass

Plants are hand harvested using a 1 m² quadrat at each of the five sampling stations before harvest of the crop plants. Botanical separations are performed by species by station, dried, and the dry biomass for each species at each station is obtained.

• Calculate the sum of the total non crop plant biomass (over species) at each station; calculate the mean total non crop plant biomass per plot.
• Report for ANPP : mean total non crop plant biomass (g/m²/y), SE, with n=6 reps (blocks).

Total

sum each plot crop and non crop plant biomass.

• Report mean total biomass (g/m²) and SE with n=6 reps (blocks).

Treatment 3, 4: Low Chemical Input / Annual tillage, Zero Chemical Input / Annual tillage

Corn / Cover crop (CC) / Soybean / Wheat / CC rotation

Crop

Identical to Treatment 1

Non crop plant biomass

Identical to Treatment 1

Cover Crop (CC)

Plants are hand harvested using a 1 m² quadrat at each of the five sampling stations just prior to plowing and planting of the annual crop. The CC has often not reached physiological maturity by this time (typically mid- to late-May). Non crop plant biomass is separated from CC for separate analysis (below).

• Calculate the mean total CC biomass per plot on a dry weight basis.
• Report for ANPP: mean total biomass (g/m²/y) and standard error (SE) with n=6 reps (blocks).

CC Non crop plant biomass

Botanical separations are performed by species by station, dried, and the dry biomass for each species at each station is obtained.

• Calculate the sum of the total non crop plant biomass (over species) at each station; calculate the mean total non crop plant biomass per plot.
• Report for ANPP : mean total non crop plant biomass (g/m²/y), SE, with n=6 reps (blocks).

Total

sum each plot crop, non dominant plant biomass, CC, and CC non dominant plant biomass.

• Report mean total biomass (g/m²) and SE with n=6 reps (blocks).

Table 1.

Crop	Treatment	Row spacing (in)	Quadrat dimensions
Corn	T1-T4	30 inch	1.5 m x 0.65 m
Soybeans	T1-T2	7.5 inch	2.0 m x 0.5 m
Soybeans	T3-T4	30 inch	1.5 m x 0.65 m
Wheat	T1-T4	7.5 inch	2.0 m x 0.5 m

Treatment 5

Populus Plantation. Poplar trees (with grass cover crop 1990 – 2007)

Crop (effective through 2007)

Poplar woody biomass has been estimated using a regression equation developed from a destructive harvest each fall prior to fall leaf drop. Historically basal tree diameter squared has been the best predictor of total tree biomass.

• Allometric measures of basal tree diameter (mm) at 15 cm above the soil surface are taken in December. The measurements are made on 5 randomly chosen trees in the 2 × 1 m density plots. Data for rep, tree #, diameter (mm) are entered into a poplar allometric spreadsheet. A histogram of tree diameter is generated to establish the range of diameters and to develop size classes used in the destructive harvest to follow. The regression equation developed in the destructive harvest is used in conjunction with the diameter measures to estimate the biomass.

• Mean woody tree biomass (kg/tree) is converted to mean woody areal extent on the basis of 0.5 trees per m².

The 2 × 1m density trees are a matrix of 86 trees (EW) by 27 trees (NS) within a 88.3 by 53.2 m area = 2322 trees/ 4697.56 m² = 0.49 trees/m²

• Calculate woody growth increment: The difference of the mean woody tree biomass between successive growing seasons (g/m²/y) for each plot

Regression Equations for Estimated Woody Biomass

The following predictive equations for poplar woody or total biomass have been generated using the destructive harvest technique. Reported are equations pertaining to the main site 2 × 1 m spacing, however equations specific to tree density spacings and non dominant plant biomass/non dominant plant biomass free growth may be available from the investigating lab for that season. Diameter is measured as mm from 15 cm from the ground unless specified otherwise. Trees were planted as 25 cm cuttings in 1989.

Year	Equation	r2	Lab
1989	Not applicable (whole tree harvests)	NA	Core
1990	wdbmass (Kg/tree) = 0.0054 (diam mm 2) + 168.5	0.98	Gross (updated 3/31/95 sjh)
1991	wdbmass(Kg/tree) = 0.09 (diam cm 2) – 0.6	0.925	Pregitzer/ Maas thesis
1991	totbmass(Kg/tree) = 0.099 (diam cm 2) – 0.667	0.93	Pregitzer/ Maas thesis
1992	wdbmass(Kg/tree) = 0.00935 (diam mm 2) -491.07 totbmass(Kg/tree) = .01086 (diam mm 2) – 816.96	0.95	Core/Halstead
1993	wdbmass(Kg/tree) = .0011 (diam mm 2) – 0.829 totbmass(Kg/tree) = 0.0012 (diam mm 2) – 0.97	0.96	Core/Halstead
1994	Wdbmass (kg/tree) = 0.00139 (diam mm 2) -1.867	0.92	Core/Halstead	Does not work for trees with diam < 37.66 mm
1995	Wdbmass (kg/tree) = 0.00205 (diam mm 2) – 3.366	0.983	Core/Halstead
1996	Wdbmass (kg/tree) = 0.0022 (diam mm 2) – 5.844	0.929	Core/Halstead	Drought year- high tree mortality
1997	Wdbmass (g/tree) = 1.5784 (diam mm 2) + 187.853 Note units are in Grams per tree!	0.853	Core/Halstead
1998	Wdbmass (kg/tree) = 0.0016 (diam mm 2 ) – 0.276	0.975	Core/Halstead

Leaf

Poplar leaves drop throughout the growing season. Leaf litter is collected in 0.8 × 1.2 m wooden litter trap frames (size was designed to fit within or between poplar rows ). Two traps are placed in each plot prior to leaf fall in late August. Leaves within the traps are collected weekly throughout the season, dried, weighed, ground and archived for tissue analysis.

• Calculate the mean litter biomass (g/m²) per plot per collection date.
• Report for ANPP: Mean seasonal (sum over dates) litter drop (g/m²/y), n=6 reps (blocks).

Total Crop ( Populus ) ANPP:

• Calculate on a per plot basis the sum of woody growth increment and leaf fall by plot, SE, and n=6 reps (blocks).
• Report for ANPP the mean sum, SE, and n=6 reps (blocks).

Grass cover (present 1990 – 2007)

Grass Festuca rubra (red fescue) is hand harvested from two 0.8 × 1.2 m stations per plot in late August (Litter traps [above] are placed on the harvested area). Plants are separated by species, dried and weighed. Fescue is ground and archived separate from all other species that are pooled for grinding and archiving.

• Calculate the mean fescue biomass (g/m²) per plot.
• Report for ANPP: Mean fescue biomass (g/m²), SE, and n=6 reps.

Total ANPP

• Calculate on a per plot basis the sum of total Populus ANPP (woody growth increment + leaf fall), grass cover, and non crop plant biomass.
• Report for ANPP the mean sum, SE, and n=6 reps (blocks).

Treatment 6

Continuous Alfalfa

Crop

Alfalfa is hand harvested using a 0.5 × 2.0 m quadrat at each of the five sampling stations at one-tenth bloom (just prior to agronomic harvest) 3 to 4 times per year: late May, early July, mid-August and mid-October. Alfalfa is separated from non crop plant biomass prior to drying.

• Calculate the mean biomass (g/m²) per plot by harvest date and the total seasonal biomass (g/m²) per plot.
• Report for ANPP : Mean seasonal biomass (g/m²/y), SE, and n=6 reps (blocks)

Non crop plant biomass

Non crop plant biomass is collected from the crop sample noted above. Botanical separations are performed by species by station, dried, and weighed. Non crop species are combined for grinding and archive.

• Calculate the sum of the total non crop plant biomass (over species) at each station for each harvest date; the mean total non crop plant biomass per plot (g/m²) by harvest date; and the total seasonal non crop plant biomass per plot (over harvest dates).
• Report for ANPP : mean total seasonal non crop plant biomass (g/m²/y), SE, with n=6 reps (blocks).

Treatment 7

Successional Community

Plant biomass

Plants are hand harvested using a 0.5 × 2.0 m quadrat at each of the five sampling stations at physiological maturity of the majority of the non dominant plant biomass community in early August. Botanical separations are performed by species by station, dried, weighed, ground and archived.

• Calculate the sum of the total non dominant plant biomass (over species) at each station; and the mean total non dominant plant biomass per plot (g/m²).
• Report for ANPP : mean total non dominant plant biomass (g/m²/y), SE, with n=6 reps (blocks).

Treatment 8 Never Tilled Community

Plant biomass

Plants are hand harvested using a 0.5 × 0.5 m quadrat at each of the five sampling stations. A reduced harvest area is used due to the smaller plot size. The dominant plants have primarily perennial life histories and mature over a range of the summer months. Cool season grasses (e.g. Bromus sp.) and late season perennials (e.g. Solidago sp.) are dominants, and a harvest in early August allows for reasonable assessment of both types of communities. Botanical separations are performed by species by station, dried, weighed, ground and archived.

• Calculate the sum of the total non dominant plant biomass (over species) at each station; the mean total non dominant plant biomass per plot (g/m²).
• Calculate the sum of the total non dominant plant biomass (over species) at each station; the mean total non dominant plant biomass per plot (g/m²).
• Report for ANPP : mean total non dominant plant biomass (g/m²/y), SE, with n=6 reps (blocks).

Treatment SF

Successional Community – Old Field for 20+ years

Non dominant plant biomass

Identical to Treatment 7

Leaves

Leaf litter is collected in two 0.5 x 0.95 m litter traps placed on the forest floor prior to leaf fall in early September. Traps are emptied weekly, dried, and composited by plot over the season, ground and archived at the end of each season.

• Calculate total seasonal leaf fall per site.

Treatment DF and CF

Deciduous/Conifer Forest Community

Wood

Annual growth is estimated by changes in stem diameter for all trees over 5 cm dbh within each of the three DF/CF stands. Stem diameters are measured in the winter with dbh tape at 4 points on the stem. The 4 points are established by hanging a measuring chain from a nail at 5 feet from the ground. Average diameters are used to estimate individual tree mass based on allometric equations available in Tritton and Hornbeck (1982):

Example equations:

Species	Equation	applies within diameter range:
Acer rubrum	wt (lb)=2.0772(dbh)^2.5080	2-20 in
Acer saccharum	wt (lb)=2.4439(dbh)^2.5735	2-20 in
Carya glabra	wt (lb)=2.034(dbh)^2.6349	2-20 in
Fraxinus americana	wt (lb)=2.3626(dbh)^2.6174	2-20 in
Prunus serotina	wt (lb)=1.8082(dbh)^2.6174	2-20 in
Quercus alba	wt (lb)=1.5647(dbh)^2.6887	2-20 in
Quercus rubra	wt (lb)=2.4601(dbh)^2.4572	2-20 in
Picea abies	ln wt=0.8079+2.3316*(ln dbh)	1-26 in
Pinus resinosa	ln wt=0.7157+2.3865*(ln dbh)	1-20 in
Pinus strobus	ln wt=0.4080+2.4490*(ln dbh)	1-26 in
Prunus serotina	wt(lb) 1.8082 * (dbh)^2.6174	2-20 in

• Calculate woody growth increment as summed differences in individual tree masses between successive growing seasons or a per site basis.

Leaves

Leaf litter is collected in two 0.5 x 0.95 m litter traps placed on the forest floor prior to leaf fall in early September. Traps are emptied weekly, dried, and composited by plot over the season, ground and archived at the end of each season.

• Calculate total seasonal leaf fall per site.

Total Tree ANPP

Sum of woody growth increment and total seasonal leaf fall (g/m²/y), SE, n=3 sites.

Herbs and shrubs

Herbs and shrubs are a minor part of these DF communities; shrub leaf litter (if any) is included in the leaf litter (above).

Citations

Cattelino, P.J., C.A. Becker and L.G. Fuller . 1986. Construction and installation of homemade dendrometer bands. Northern J. Appl. Forestry 3(2):73-75.

Fuller, L.G., P.J. Cattelino, D.D. Reed . 1988. Correction equations for dendrometer band measurements of five hardwood species. Northern J. Appl. Forestry 5(2):111-113.

Tritton, L.M. and J.W. Hornbeck . 1982. Biomass equations for major tree species of the northeast. Broomall, PA: Northeast. For. Exp. Stn.; USDA For. Serv. Gen. Tech. Rep. NE-69.

Weed Science Society. 1984. Weed Science composite list of weeds. Weed Science Vol. 32 Supplement 2.