Hammond, M., K. Tindall, and K.L. Gross
Presented at the All Scientist Meeting (1999-07-20 to 1999-07-21 )
The change to the use of chisel plowing for conventional tillage in the LTER has prompted the need for an additional seed bank study. This study will investigate possible differences in the total number and species composition of seeds in different annual communities. Soil samples (15 cm depth) were collected from each of five stations in the following treatments: high input corn conventional till (T1), high input corn no till (T2), low input corn with cover crop (T3), zero input corn with cover crop (4), and historically tilled successional community (T7). All six replications in the LTER were sampled. These cored soil samples were then divided into 0-5 cm and 5-15 cm depths. The soil from each of these depth ranges was weighed with half of the sample dedicated to a greenhouse direct germination study and the second halve to an elutriation study.The change to the use of chisel plowing for conventional tillage in the LTER has prompted the need for an additional seed bank study. This study will investigate possible differences in the total number and species composition of seeds in different annual communities. Soil samples (15 cm depth) were collected from each of five stations in the following treatments: high input corn conventional till (T1), high input corn no till (T2), low input corn with cover crop (T3), zero input corn with cover crop (4), and historically tilled successional community (T7). All six replications in the LTER were sampled. These cored soil samples were then divided into 0-5 cm and 5-15 cm depths. The soil from each of these depth ranges was weighed with half of the sample dedicated to a greenhouse direct germination study and the second halve to an elutriation study.In the direct greenhouse study, the soil was spread on top of a soil-less medium, and a census of the germinating seedlings is currently underway. In the second component of this study, an elutriation system is currently being used to separate the seeds from the soil. These seeds are then dried, collected and will be identified in the near future. Together, these two aspects of the study provide an accurate method to estimate weed seed densities. The total number of species, total number of seeds, and similarity indexes will be analyzed to test for differences in the seed bank between agricultural treatments. Lastly, a field census of the weed seedling emergence is being conducted to complete the seed bank study. This census will provide data to compare the composition of emergent weed seedlings in the field to the composition of the mature weed community harvested in the fall. Although much of the data collection and analysis has yet to be completed, striking differences between the number of monocot and dicot seedlings have already been observed in the greenhouse study.In the direct greenhouse study, the soil was spread on top of a soil-less medium, and a census of the germinating seedlings is currently underway. In the second component of this study, an elutriation system is currently being used to separate the seeds from the soil. These seeds are then dried, collected and will be identified in the near future. Together, these two aspects of the study provide an accurate method to estimate weed seed densities. The total number of species, total number of seeds, and similarity indexes will be analyzed to test for differences in the seed bank between agricultural treatments. Lastly, a field census of the weed seedling emergence is being conducted to complete the seed bank study. This census will provide data to compare the composition of emergent weed seedlings in the field to the composition of the mature weed community harvested in the fall. Although much of the data collection and analysis has yet to be completed, striking differences between the number of monocot and dicot seedlings have already been observed in the greenhouse study.
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