Population models indicate that managing agroecosystems to reduce weed seed survival in soil seedbanks has the potential to decrease weed populations. A series of bioassays was conducted in soil collected from the Long Term Ecological Research site at the Kellogg Biological Station in Hickory Corners, MI. We determined the effect of 1) contrasting agricultural management, 2) burial method, 3) surface sterilization, and 4) mechanical damage to seed coats on the proportion of weed seeds surviving a 28 d incubation in soil at 25 C and 330 kPa matric potential. Weed species included common lambsquarters (Chenopodium album), field pennycress (Thaspi arvense), giant foxtail (Setaria faberi), kochia (Kochia scoparia), velvetleaf (Abutilon theophrasti), and yellow foxtail (Setaria glauca). Each of the four factors studied significantly (P < 0.05) affected weed seed survival. Seed survival rates of both giant foxtail and velvetleaf were 10 to 20% lower in conventionally managed soils than in soils managed with low, or no, chemical inputs. Burying seeds in mesh bags, a common experimental practice, increased velvetleaf seed mortality due to an increase in fatal germination, but had the opposite effect on giant foxtail seeds. Surface sterilization of the seed coat with 5% bleach for 5 minutes decreased velvetleaf seed survival by 7%, but increased giant foxtail seed survival by 40%. Survival of all six weed species was reduced by mechanical damage to the seed coat, with large declines in velvetleaf and kochia seed survival (77 and 83%, respectively). The wide range of weed seed survival rates in response to altered abiotic and biotic conditions holds promise for the development of agricultural management practices that reduce weed seed survival in soil seedbanks. Ianuzzi, James (REU Student), Adam Davis, and Karen Renner. 2003. Factors Affecting Weed Seed Survival in Soil Seedbanks. 508 5 2003 I examined the effects of adding ammonium nitrate fertilizer in late successional and mid successional ecosystems in Southwestern Michigan. Fertilizer was added to two plots in replicate communities over the course of five years (1994-1999) at levels of 10 kg/ha/yr and 30kg/ha/yr, respectively. Potential nitrification rates were measured using an enzyme inhibition method. I was not able to detect any difference between fertilizer levels. However, I found a significant difference between the potential nitrification rates of mid-successional and late successional ecosystems. The mid-successional ecosystem had a significantly (p<0.05) lower amount of mean potential nitrification (0.0176 (&mu;g/g dry soil/day) occurring in the top 16cm of soil than did the late successional ecosystem (0.0869 (&mu;g/g dry soil/day). This result suggests that successional lands may serve as a valuable pollution buffer that sequesters atmospheric deposition Case, Michael (REU Student). 1999. Nitrification Rates in Soils from a Mid Successional and Late Successional Ecosystem 509 5 1999