Seed Bank Composition
Sampling Frequency: Every third year initially; every sixth year currently [amended 5-17-2002 TTB]
The soil seed bank is sampled triannually by elutriating soil samples (Gross and Renner 1990) from each plot . Soil cores are collected from 0-5 and 5-15 cm depth increments.
Samples are taken from each of the 5 sampling stations in each treatment replicate in
the LTER main site (7 trts * 6 reps; in 1994 the forested sites were added to the sampling
regime). The sampling location is 1 m to the southwest of the sampling flag; 10 cores (1
inch diameter) to a depth of 15 cm are taken from a quadrat area of 25*25 cm. Cores are
uniformly distributed in the quadrat.
Each core is divided into 2 depth intervals: 0-5 cm and 5-15 cm. The 10 cores from each
quadrat are composited and placed in separately labeled paper bags. Each bag is labeled
with the trt/rep/sample location and depth. The 2 bags from each sample location are
placed in a ziplock bag. Samples are stored in the dark at 5 degrees C until elutriated
following methods in Gross and Renner (1989). Storing the samples at cool temperatures
should prevent germination and facilitate elutriation as the samples will not form "
peds" as a consequence of drying.
A single location is sampled from the center of each of the 4 microplots (+/-
fertilizer; +/- herbicide) at 30" row spacing in all reps of trts 1 and 2
(conventional and notill). In the no fertilizer treatments, the samples are taken from the
middle of the first 6 rows to avoid areas that were accidentally fertilized in 1989. All
other samples are taken form the center of the 12 row microplot.
Treatment 8 was not sampled. Treatment 1 (conventional till) will be resampled after it
is plowed to determine how tillage effects the distribution and viability of seeds in the
seed bank. If these samples are taken more than 2 weeks after the main site sampling was
done, the no-till plots will be resampled f or a comparison of time effects.
Gross, K.L. and K.A. Renner. 1989. A new method for estimating seed
numbers in the soil. Weed Science 37:836-839.