02310nas a2200145   4500008004100000245007600041210006900117300001500186490000700201520180500208100001502013700001902028700001702047856010002064       2005                        eng d00aPartitioning of nitrogen over five growing seasons in tallgrass prairie0 aPartitioning of nitrogen over five growing seasons in tallgrass   a1280 -12870 v863 aAnnual spring burning of tallgrass prairie increases plant biomass production despite losses of N and lower net N mineralization. To better understand how burning influences the cycling of N in prairie, 15N was injected to soil as NH4+, and the partitioning between plant and soil N pools was followed over five growing seasons in annually burned and unburned prairie. Applied 15N was rapidly immobilized with <2% and 11% of the 15N remaining in inorganic forms six days after application in burned and unburned prairie, respectively. Seventy-seven percent (burned prairie) and 70% (unburned prairie) of the applied 15N was initially recovered as soil organic N (oN), with a majority accounted for in microbial biomass. Plants contained ∼20% of the applied N with the largest portion recovered from roots regardless of burning. At the end of the first growing season, only 55% of the applied 15N was recovered from the unburned prairie, while 85% was recovered from burned prairie. The total 15N content of the plants changed little during the first growing season, but the portion recovered in the rhizomes increased, indicating belowground N storage. Total recovery and distribution of applied N changed little from the end of the first to the end of the second season growing season. Accumulations of 15N within the plants decreased greatly between the second and fifth growing seasons, but N lost from plants was accounted for in oN. Conservation of N by plants and tight cycling of N within the root zone suggest mechanisms by which prairie can be a highly productive ecosystem despite limited N availability. The immobilization of potentially mineralized N within the root zone increased with burning, offsetting the loss of N to fire probably by reducing leaching and denitrification losses.1 aDell, C.J.1 aWilliams, M.A.1 aRice, C., W.  uhttp://129.130.186.12/content/partitioning-nitrogen-over-five-growing-seasons-tallgrass-prairie02094nas a2200133   4500008004100000245007300041210006900114300001300183490000700196520162900203100001501832700001701847856009601864       2005                        eng d00aShort-term competition for ammonium and nitrate in tallgrass prairie0 aShortterm competition for ammonium and nitrate in tallgrass prai  a371 -3770 v693 aThe availability of N limits productivity in tallgrass prairie. Spring burning is common because it results in greater plant productivity despite reducing net N mineralization. To better explain how burning affects inorganic N availability in tallgrass prairie, the partitioning of 15N among plant and soil pools was measured in June and August 1994. Approximately 2.5 μg N g−1 soil was injected as either NH4 or NO3 to a depth of 15 cm within cores in burned and unburned prairie. Cores were removed from the field 6 d after injection, and 15N recovery in plant and soil N pools was determined. No more than 14% of the applied 15N remained in inorganic form 6 d after application. The largest portion of the applied 15N (35–80%) was recovered in the soil organic nitrogen pool (No). Burning significantly increased the immobilization of both NH4 and NO3 within No, and microbial biomass accounted for ≥50% of the 15N recovered in No Accumulation of 15N in plants accounted for ≤35% of the applied 15N with a majority recovered from roots. Burning had little effect on 15N recovery in plants; however, 15N accumulations in roots were significantly greater when NO3 was used. Results indicate that immobilization within soil organic matter (SOM) controls the availability of both NH4 and NO3 to plants. Increased immobilization in soils with burning probably results largely from increased microbial N demand resulting from greater litter inputs with wider C to N ratios. Further research is needed to determine if abiotic mechanisms for N immobilization also significantly influence N availability in prairie soils.1 aDell, C.J.1 aRice, C., W.  uhttp://129.130.186.12/content/short-term-competition-ammonium-and-nitrate-tallgrass-prairie02223nas a2200157   4500008004100000245013000041210006900171300001300240490000700253520161100260653002201871100001501893700001501908700001701923856012501940       1999                        eng d00aChanges in enzyme activities and microbial biomass of tallgrass prairie soil as related to burning and nitrogen fertilization0 aChanges in enzyme activities and microbial biomass of tallgrass   a769 -7770 v313 aMicrobial biomass and enzyme activities are affected by management practices and can be used as sensitive indicators of ecological stability. Microbial biomass C (MBC), microbial biomass N (MBN) and eight enzyme activities involved in the cycling of C, N, P and S were studied in the surface (0–5 cm) of an Irwin silty clay loam soil (fine, mixed, mesic, Pachic Arguistoll) in a tallgrass prairie ecosystem. Treatments of annual spring burning and N fertilization were initiated in 1986 and encompassed: (1) unburned–unfertilized, (2) burned–unfertilized, (3) burned–fertilized, and (4) unburned–fertilized. Activities of dehydrogenase, β-glucosidase, urease, deaminase, denitrifying enzyme, acid phosphatase, alkaline phosphatase, and arylsulfatase were assayed. Long-term burning and N fertilization of the tallgrass prairie soil reduced MBC and MBN relative to the unburned–unfertilized treatment. The effects of burning and N fertilization varied among the enzymes and the time of sampling. Long-term burning significantly (P<0.05) increased activities of urease and acid phosphatase, but decreased activities of β-glucosidase, deaminase and alkaline phosphatase. Long-term N fertilization significantly increased activities of β-glucosidase and acid phosphatase but decreased urease activity. This study found that several soil enzyme activities can be used as indicators of ecological changes caused by N fertilization and long-term burning management practices. The relevance of these changes in surface soil to the long-term sustainability of this ecosystem needs further evaluation.10atallgrass prairie1 aAjwa, H.A.1 aDell, C.J.1 aRice, C., W.  uhttp://129.130.186.12/content/changes-enzyme-activities-and-microbial-biomass-tallgrass-prairie-soil-related-burning-and00458nas a2200133   4500008004100000245004800041210004800089260004300137300001100180490002100191653002200212100001500234856007500249       1998                        eng d00aNitrogen cycling in tallgrass prairie soils0 aNitrogen cycling in tallgrass prairie soils  aManhattan, KSbKansas State University  a1 -1520 vPhD Dissertation10atallgrass prairie1 aDell, C.J.  uhttp://129.130.186.12/content/nitrogen-cycling-tallgrass-prairie-soils