Plant Litter
Decomposition
- Project Goal
- To examine the fate of each yearly litter cohort (respired as CO2 or incorporated into
soil organic matter) and quantify the effects of initial litter quality, crop rotation, and irrigation
on decomposition in an agroecosystem.
- Project Description
- Each year carbon in fixed (photosynthesis) and is incorporated into above and belowground biomass.
This biomass senesces at the end of the growing season and decomposes. As plant litter decomposes it
is either respired back into the atmosphere or is converted into stable soil organic matter. The
amount of carbon transferred to this stable soil organic matter pool is the essence of carbon storage (Fig. 1).
Fig. 1A Theory predicts that litter decomposition declines exponentially
over time and the largest mass loss occurs in the first few years.
Fig. 1B The input of litter can be visualized as annual cohorts, following the
trajectory of 1A and all these cohorts contribute to the total soil carbon pool.
The transformation of litter follows a continuum with soil organic matter as the endpoint.
- Steps:
- Annually, harvest above and below ground biomass from each field within each IMZ.
- Separate the biomass into leaves, stalks, cobs, pods, root stalks, coarse roots and fine root depending upon
the crop.
- Determine initial tissue quality: C/N content, soluble, cellulose, hemicellulose, and lignin.
- Decompose litter in litter bags (20 cm x 20 cm, 1mm mesh size) and below ground capsules (2 cm x 2.5 cm,
2 mm mesh size)
- Determine mass loss and analyze litter at 6 months, 1 year, 1.5 years, 2 years, 2.5 years, and 3 years.
- Progress
- At the 6 month harvest, there are some initial decomposition differences because of management practices,
but this difference disappears by 12 months (Fig. 2). By 30 months, we see that between 60-80% of the carbon is lost.
Fig. 2 % C loss for 2001 litter cohort by tissue type for 6-30 month harvest.
Significant differences between fields for each harvest noted by a,b,c (p< 0.05).
- In 2002, Fields 2 and 3 were soybean. We see that in general, pods decompose more rapidly than cobs
(by 18 months over 80% of carbon is lost for pods compared to 40% carbon loss for cobs) (Fig. 3). There
are no consistent differences between corn and soybeans or management practices for the other tissue types.
Fig. 3 % C loss for 2002 litter cohort by tissue type for 6-18 month harvest.
Significant differences between fields for each harvest noted by a,b,c (p< 0.05).
- In 2003, there were no apparent management differences as in 2001 (Fig. 4).
Fig. 4a % C loss for 2003 litter cohort by tissue type for the 6 month harvest.
Significant differences between fields for each harvest noted by a,b,c (p< 0.05).
Fig. 4b % C loss for 2001 litter cohort by tissue type for the 6 month harvest.
Significant differences between fields for each harvest noted by a,b,c (p< 0.05).
- Staff
- Johannes Knops
is a professor in the School of Biological Sciences specializing in ecosystem and plant ecology.
- Amy Kochsiek is a graduate student in the School of Biological
Sciences and is working on projects related to plant community composition and carbon cycling.
- Kate Stoysich (2003 - present) and Kenneth Elgersma
(2002 - 2003) are invaluable technicians on the CSP project. They organize and process all of the samples.
- Sougata Bardhan is now a graduate student at Ohio State University
and worked on the CSP project from 2000-2002.
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