GLBRC089: Below Ground Net Primary Production- GLBRC BCSE Sites

Active

Replaces Below Ground Net Primary Production- GLBRC Intensive Sites

In use from 2008-01-01

Abstract

Perennial crops

Surface fine-root production: Root in-growth cores

Fine root production is estimated from root in-growth cores (Bledsoe 1999, Fahey et al. 1999). Two 2-mm mesh cores that measure 5-cm diameter × 13-cm long containing native soil medium are installed at each permanent station within treatment plot at the beginning of the growing season (April/early May). The cores are placed randomly in the interstitial space among vegetation. To determine an approximate peak standing crop, one of the two cores at each sampling station is harvested at mid-season (mid-July) and the other is harvested at the end of the season (October). The roots are washed free of soil over a 2-mm sieve, dried at 60 °C for 48 h, and weighed. Root in-growth cores were discontinued after 2014.

Subsurface standing stock

To allocate fine root production to depths below 13-cm, we will sample standing stock of live and dead root biomass to ~1 m at season’s end (November). One set of 3 cores (each 7.6-cm diameter × 1-m long) will be removed from each treatment plot. Cores will be segmented by soil depth (0-10, 10-25, 25-50, and 50-100 cm). At Arlington, roots are washed free of soil over a 2-mm sieve, dried at 60 °C for 48 h, and weighed. At KBS, cores are air-dried, sieved over a 2-mm sieve, washed to remove any remaining soil, dried at 60 °C for 48 h, and weighed. To account for spatial variability in fine root production, these 1-m deep cores will be removed along plant density gradients moving out from the center of a bunchgrass into the interstitial space. Differences in the distribution of root biomass beneath plants and in the interstitial areas will be modeled as a function of plant functional type cover. Standing stock deep cores were discontinued after 2013.

Note: A 6-cm diameter x 1-m long core was used in 2009.

Annual crops

Annual fine and tap root production

In annual crops, plant excavations at the time of plant physiological maturity are used to index belowground primary productivity. At KBS, 1 plant is selected from the area clipped for ANPP, and the roots associated with that plant are removed to the laboratory. At Arlington, all plants in a 1 m2 area are excavated, aboveground biomass discarded, and the soil and roots removed to the laboratory. At both sites, the roots are washed free of soil over a 2-mm sieve, dried at 60 °C for 48 h, and weighed. Annual crop root production was discontinued after 2014.

Cover crop root production

In cover crops, plant excavations at time of cover crop ANPP sampling are used to index belowground primary productivity. One plant is selected from within the area clipped for ANPP, and the roots associated with that plant are removed to the laboratory, washed free of soil over a 2-mm sieve, dried at 60 °C for 48 h, and weighed. The plants within the quadrat are counted, and that number is multiplied by the weight of the roots of the single plant to get areal BNPP.

Protocol

Equipment

Perennial crops

Surface fine-root production: Root ingrowth cores

  1. Soil core hammer w/bit – Model 77557 (Forestry Suppliers – www.forestry-suppliers.com)
  1. Plastic soil core inserts (1 per core) – 77848  Butyrate Plastic Liner; 2″ × 6″L (Forestry Suppliers)
  1. Soil core insert caps (2 per core) – 77483  2" Polyethylene Liner Caps (Forestry Suppliers)
  1. 2-mm mesh cores (2 per station)
  1. Tape measure
  1. Compass
  1. Location data sheet
  1. 2 – mm sieve w/tray
  1. Aluminum foil or plastic wrap
  1. Clean sand

Procedure

Field

  1. Locate plot station and determine root ingrowth core locations, orient so that they are not in the ANPP quadrat location (ANPP protocol). Measure 1 and # – m in a pre-determined compass direction away from the plot marker and note locations on the data sheet.

At KBS:

  1. Place plastic soil core sleeve in the hammer bit and remove soil core from determined location – mark location with a flag.
  1. Remove core from insert – hand drill with bit works well
  1. Remove rocks and roots over a 2 – mm sieve.
  1. Add enough sand to replace the roots and rocks. Cores are typically 75% native soil and 25% sand, but may be up to 1/3 sand and 2/3 soil if soil is particularly wet or rocky.

At Arlington:

  1. Mix sieved soil from fallow plot (untreated Plano silt loam, from West Madison Agricultural Research Station) with sand in a 75% soil, 25% sand ratio.

At both sites:

  1. Fill core with soil/sand mixture.
  1. Install root ingrowth cores flush with soil surface at appropriate location.

Making root ingrowth cores

  1. Cut #5 mesh canvas into 15 × 18 – cm rectangles (Fig. 1) – #5 Plastic mesh canvas (Blue Ribbon Crafts – www.blueribboncrafts.com) and 1 – soil core insert cap with holes poked in for drainage (see above for cap info.)
  1. Staples edges with 2 hole overlap (Fig. 2).
  1. Apply a small bead of hot glue to soil core insert cap and place into pre-formed mesh core (Fig.3).

number 5 plastic mesh canvas

stapled edges

hot glued cap inserted in mesh core

ready to install

Subsurface standing stock (discontinued after 2013)

  1. Truck with hydraulic soil corer
  1. 1 – m plastic soil core inserts (1 per location) – Giddings Machinery Co. (Arlington) or Geoprobe (KBS)
  1. Soil core insert caps (2 per location) – Giddings Machinery Co. (Arlington) or Geoprobe (KBS)
  1. Marker or label to mark plastic soil core insert

Field

  1. Choose coring location (1 location per plot). Locate core in a representative part of the plot, but minimize disturbance to the plot from the truck.
  1. At each coring location, remove 1-m deep cores (3) along plant density gradients moving out from the center of a bunchgrass into the interstitial space (one core at center, one on the edge of the plant, and one in the interstitial space).
  1. Remove to lab or processing station. Place in refrigerator until processing occurs.

Lab

  1. Split plastic soil core insert (Fig. 1).
  1. Segment into appropriate soil horizons.
  1. Roots are washed free of soil over a 2-mm sieve.
  1. Separate into live and dead components.
  1. Dry at 60 °C for 48 h.
  1. Weigh and record.

split core inserts

Equipment

Annual crops

Annual fine and tap root production

Quadrat as per ANPP protocol
Shooter shovel
Clippers
Large 50lb. paper sack.

Procedure

Field

At Arlington:

  1. Locate quadrat as per ANPP protocol.
  2. Excavate all plants in a net 1 × 1 m area (quadrat size per ANPP protocol).
  3. Aboveground biomass is clipped and discarded and the root ball is placed into pre-labeled paper sacks.
  4. Soil and roots are removed to the laboratory.

At KBS:

  1. Choose one plant within quadrat used for ANPP collection.
  2. Excavate all roots associated with that plant and place in pre-labeled paper sack.
  3. Remove soil and roots to laboratory.

Lab

  1. Roots are washed free of soil over a 2-mm sieve.
  2. Roots are oven dried at 60 °C for 48 h.
  3. If desired, tap root can be separated from fine roots.
  4. Weigh and record.

Calculations

At KBS, the roots associated with one plant are sampled.
g/plant x plant population/m2 = g roots/m2

At Arlington, all plant roots in a 1 m2 area are excavated, therefore plant population is not needed for this calculation.

Authors:

Datatables