Nutrient Dynamics of Forest Communities in Central Illinois

144 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.Four separate investigations of nutrient cycling in forests were conducted at Robert Allerton Park, 7 km southwest of Monticello in east central Illinois. Research was conducted in the two dominant forest types of the region: (1) a floodplain community (Acer saccharinum dominant), and (2) an upland community (Quercus spp. and Carya spp. dominant).(I) Litterfall and Decomposition. Inputs from litterfall occurred in pulses, and annual variations resulted from irregular phenomena such as ice storms, mast fruiting, and herbivory. Annual floodplain and upland litter inputs were 7971 kg ha('-1) and 8092 kg ha('-1) respectively, and were higher than litterfall for other similar forest communities. Floodplain and upland nutrient inputs through litterfall were comparable and were in the order Ca > N >> K > Mg > P > Na. Leaf litter decomposition was rapid at the floodplain site with 95% of original dry weight lost after one year. Upland leaf litter lost 60% of original dry weight in two years, and was characterized by assimilation of N, moderate retention of P and Ca, and leaching of K, Mg and Na.(II) Seasonal Variation in Soil Nutrients. Total N did not fluctuate greatly at either the floodplain or upland site, although there was some evidence of a spring decrease, especially in upland soils. Available P in floodplain soils was dependent on pH, which was in turn influenced by flooding patterns. There was no evidence of seasonal variation in available P for upland soils. Exchangeable base concentrations in floodplain soils were correlated with pH to some extent, and K may have been subject to leaching and plant uptake. Soil pH was strongly correlated with exchangeable base concentration, especially Ca and Mg, in upland soils. Exchangeable Na was variable at both sites and may have been influenced by leaching and variation in root exudation.(III) Aqueous Nutrient Fluxes. Although litterfall contained the largest fraction of elemental input to the forest floor, aqueous inputs were substantial, particularly for K and Mg. Throughfall and stemflow nutrient inputs to the forest floor are important for individuals of the plant community, since they are mostly in ionic form and are readily available in the soil solution for plant uptake. There was considerable interannual and seasonal variation with respect to allocation of rainfall among throughfall, stemflow, and canopy retention. Nutrient inputs were comparable for the floodplain and upland forests and were in the order K > Ca > N > Mg > P. Stemflow characteristics were determined for three floodplain species and nine upland species.(IV) Herbaceous Vegetation. Nutrient uptake and subsequent release through decomposition of aboveground plant parts were examined for six herbaceous species (four spring ephemerals and two summer herbs) in the upland forest and three herbaceous species in the floodplain forest. Nutrient uptake by herbs was in the order K > N > Ca > P > Mg > Na at both sites. At the upland site, uptake of N, P, and K were especially high relative to potential losses of these elements to streamflow; this suggests that the retention of nutrients by herbaceous vegetation especially during the spring flushing period, helps to minimize the depletion of the soil nutrient pool. Nutrient uptake patterns of floodplain herbs were affected by flooding, which caused early senescence in some species. Uptake of P, Ca, Mg, and Na were greater than in the upland forest despite this early senescence. Uptake and release of nutrients by herbs are small compared to inputs such as net annual gains through sedimentation, suggesting that herbaceous species may have only a minor role in the nutrient cycling regime of floodplain forests.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD