Variation in Decomposition Rates Across a Playa Wetland in Eastern Nebraska

Rachel Clarkson Author

07/30/2021 Added

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Wetlands are optimal environments for carbon sequestration due to their anoxic conditions slowing decomposition rates. Decomposition being exceedingly dynamic across different climates makes it critical to understand. Therefore, the testing of decomposition rates through this study allows for data to be gathered to determine what effects the different zones of the wetland have on decomposition rates.

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[00:00:01.830]Hello, my name is Rachel Clarkson.
[00:00:04.980]I am a sophomore Agronomy student.
[00:00:08.370]This is my presentation on my summer.
[00:00:11.460]UCare research project variation in decomposition rates
[00:00:16.320]across a Playa wetland in Eastern Nebraska.
[00:00:20.880]In
[00:00:21.300]introduction,
[00:00:22.440]wetlands are anoxic or lacking oxygen due to highly
[00:00:26.820]saturated soils.
[00:00:28.770]These anoxic conditions allow for natural sequestration of carbon
[00:00:33.210]dioxide and provide an optimum environment for long-term carbon storage.
[00:00:38.280]Sequestration is the capture and storage of carbon dioxide within the soil.
[00:00:43.560]This being said 20 to 30% of Earth's soil carbon pool is
[00:00:48.300]stored within wetlands. To the left are two pictures of the wetland used for this
[00:00:52.650]decomposition study.
[00:00:54.270]The top photo is the site in the summer when the basin is not ponded and the
[00:00:58.500]bottom photo is the site in the spring, when the basin is ponded.
[00:01:03.210]Decomposition is explained as a biogeochemical process,
[00:01:07.500]fundamental to regulation of storage and losses of nutrients
[00:01:12.270]from the soil. This being said,
[00:01:15.300]decomposition can be split into two parts early stage and late stage.
[00:01:20.520]Early stage consists of zero to 40% mass loss characterized by leaching
[00:01:25.380]of soluble compounds as well as the decomposition of cellulose materials.
[00:01:30.750]Whereas the late stage consists of 40 to a hundred percent mass loss
[00:01:35.340]characterized by the degradation of wood-like or lignified
[00:01:39.810]tissues.
[00:01:41.340]The amount of organic carbon in the soil is determined by the balance
[00:01:45.960]between carbon inputs and outputs.
[00:01:50.040]Our objective in this study was to determine how decomposition rates vary in
[00:01:54.900]relation to landscape position
[00:01:56.910]in a playa wetland and our hypothesis was
[00:02:01.650]the decomposition rates of organic material
[00:02:05.190]when placed the hydric soil of a wetland will be slower.
[00:02:09.750]Following is the test site for the experiment.
[00:02:13.860]The white arrow points to the location of the small Playa wetland,
[00:02:17.880]which is located at the Eastern Nebraska Research and Extension Center, or
[00:02:22.680]ENREC, located in Eastern Nebraska.
[00:02:26.220]The blue arrows signified the Upland, the orange, the base and edge,
[00:02:31.530]and the light green, the basin floor.
[00:02:35.820]Continuing,
[00:02:37.020]the methods for field installation include burying 6 tea
[00:02:41.910]bags at each type at a depth of five to eight centimeters at each of the nine
[00:02:46.620]different plot locations.
[00:02:48.840]The teabags were left in the field for a period of 34 and 90 days.
[00:02:53.460]The diagram below shows the formation in which the teabags were buried.
[00:02:58.930]The red circle is the rooibos tea and the green circle
[00:03:02.170]the green tea. To the right of that diagram are
[00:03:07.120]two photos from the field.
[00:03:09.790]The top photo is of me placing rooibos tea
[00:03:15.400]into a five to eight centimeter hole in the soil.
[00:03:19.660]And the bottom is a photo of me retrieving one of the preliminary rooibos teabags
[00:03:24.190]after 34 days leaving the other five in the soil for retrieval
[00:03:28.870]after the full 90 day time period.
[00:03:33.100]In the lab, the tea was carefully removed from the bags
[00:03:36.790]then oven dried up temperature of 70 degrees Celsius for 40 to 48 hours.
[00:03:42.310]Then weighed to find the mass,
[00:03:44.530]which was then subtracted from the original mass of two grams to calculate the
[00:03:48.670]total mass loss.
[00:03:50.680]The image above shows the mass loss of the tea sample from each zone,
[00:03:55.600]the top row being the Upland, then basin edge.
[00:04:00.370]Then finally, the base in floor,
[00:04:02.800]the lighter reddish samples are the rooibos tea and the darker brown samples
[00:04:07.660]are green tea. These two types of team were used
[00:04:12.280]due to their different organic matter makeups. Green tea,
[00:04:16.000]which has a lower C to N ratio breaks down more quickly. And rooibos
[00:04:20.530]which has a higher C to N ratio,
[00:04:22.840]is more resistant to decomposition. Together
[00:04:26.770]these teas can be used to measure the rate of decomposition and the
[00:04:30.910]stabilization endpoint.
[00:04:33.910]These are the results from my study.
[00:04:36.010]The upper left graph represents the difference in stabilization factor between
[00:04:40.360]the three zones Stabilization factor is
[00:04:44.050]indicative for long-term carbon storage.
[00:04:49.160]The lower right graph represents the decomposition rate between the three zones.
[00:04:54.070]Decomposition rate,
[00:04:55.480]being the short term dynamics of new input.
[00:05:00.670]In discussion of the results,
[00:05:04.810]the Upland and basin floor
[00:05:06.130]have similar S and K values, though
[00:05:09.910]the basin edge stands out as the most potentially different,
[00:05:13.390]but not quite significantly different.
[00:05:16.380]Reflecting upon our initial hypothesis,
[00:05:18.850]the results were not as predicted since we believed the saturated soil of the
[00:05:23.140]basin floor would cause decomposition to slow. This faster rate of
[00:05:28.150]decomposition in the basin floor
[00:05:30.220]may be an effect of significant leaching within the profile,
[00:05:34.690]which impacts the formation
[00:05:36.100]of E horizons. E horizons are
[00:05:39.940]lighter strips of soil where clay and nutrients have been leached down into the
[00:05:43.810]lower horizons of the profile.
[00:05:46.450]These E horizons are visible within the profile of the wetland soil,
[00:05:51.670]as marked with the white arrow in the basin edge soil core photo.
[00:05:58.040]In conclusion,
[00:05:59.330]the decomposition rate appears to be the same throughout three zones and is not
[00:06:04.310]significantly different.
[00:06:06.620]Although within the base edge, decomposition stabilizes at
[00:06:10.700]a lower mass than the other two zones in the wetland. Our next
[00:06:15.620]step in this experiment is to go back out to the field
[00:06:19.610]to collect the remaining teabags from the site. Currently,
[00:06:22.970]there are still five of each type in each location in the
[00:06:27.950]field, which will be collected after the full 90 day length of the experiment.
[00:06:33.080]The current data collected and analyzed is preliminary
[00:06:37.880]based upon one of the 6 tea bags at each location collected after a
[00:06:42.860]shorter than usual
[00:06:44.780]incubation period.
[00:06:47.390]Finally, I would like to thank my UCare mentor, Dr.
[00:06:51.740]Judith Turk for teaching me
[00:06:55.010]how to write a research paper and helping me complete the different
[00:06:59.930]steps of my research project this summer.
[00:07:03.740]I would also like to thank my lab group: Trinity,
[00:07:06.830]Aldi and Aubrey for helping me with different aspects of my project.
[00:07:12.620]And I would also like to thank the UNL UCare program for providing me
[00:07:17.450]with the opportunity to complete a research project during the summer.
[00:07:21.410]Thank you.

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Variation in Decomposition Rates Across a Playa Wetland in Eastern Nebraska

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