Treatment 7 Microplot – ANPP Harvest

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Abstract

Above ground net primary productivity (ANPP) in the LTER Trt7 (early successional community) microplots is measured by harvesting the current year’s above ground plant biomass. The harvest is timed to occur at peak biomass for the predominant species in the untilled and tilled fields. The harvested plant material is sorted to species, dried and weighed.

Protocol

The location of the annual ANPP harvest within the center 3 × 3 meter area of the experimental plot is pre-determined and changes each year (refer to the current harvest map document). The total area sampled is 1 m2. The dimensions of the sampled area are 0.5 × 2.0 meters with the 2 meter side positioned in an east-west direction.

  1. Place harvesting frame at the assigned location in the plot by measuring with the frame dimensions from a plot corner post. Place the frame on the ground surface. Straighten the plant stems so that they are not caught under the frame.
  2. Harvest plants rooted inside the frame. Clip plant stems at the ground surface and place harvested material in a paper bag (or bags) labeled “Live”. When all the live biomass is clipped, the litter lying on the ground within the frame boundary is collected. Clip through the litter along the inside edge of the frame. Carefully pick up the surface litter, avoiding soil, and place in a bag labeled “SURFL”.
    • The live biomass collection is the current year’s growth. For woody plants that have more than one year’s biomass, collect only the leaves and shoots that are the current year’s production.
    • Label collection paper bags with PlotID, Contents (e.g. Live, SURFL, SDEAD, etc.) Collection Date, Project (LTER/KLG), and ‘Bag#’ of ‘Total Bags’ (e.g. 1 of 3).
  3. After leaving the field, refrigerate biomass until it is sorted. Ideally harvested material should be sorted within one to two days of collection.
  4. In the lab, pool all ‘Live’ biomass from a given plot and sort to species. Each of the species is placed in a paper bag. All biomass (species, surface litter [SURFL], standing dead [SDEAD]) is dried in a forced air oven at 62°C for a minimum of 72 hours.
  5. Dried biomass is weighed on a balance to ± 0.01 grams.

Plant Identification References:

Gleason, Henry A. and Arthur Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada, Second Edition. New York Botanical Garden: Bronx, NY.

Holmgren, Noel G. 1998. Illustrated Companion to Gleason and Cronquist’s Manual. New York Botanical Garden: Bronx, NY.

Voss, Edward G. 1972, 1985, 1996. Michigan Flora, Parts I, II, III. Regents of the University of Michigan: Ann Arbor, MI.

Barnes, Burton V. and Warren H. Wagner, Jr. 1981. Michigan Trees. University of Michigan Press: Ann Arbor, MI.

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