Soil Nitrogen Availability following Long-Term Burning in an Oak-Hickory Forest1
- Eric D. Vance and
- Gray S. Henderson2
Seasonal levels of extractable ammonium and nitrate in the surface soil of oak-hickory (Quercus spp. and Carya spp.) forest plots subjected to 30 yr of annual and periodic (4-yr) prescribed burning were studied. Laboratory incubations were also carried out for 4-, 14- and 28-d periods at each of six dates to determine the effect of the burning treatments on mineralizable N. Ammonium was the predominant N form regardless of treatment. Burning significantly (P = 0.05) reduced quantities of extractable NH+4 over all sampling dates, with annual burning resulting in lower amounts than burning every 4 yr. Burning also significantly reduced the quantity of N mineralized during incubation. Since previous studies have not shown decreases in total N on the burned plots, the lower extractable N concentrations appear to be the result of an adverse effect of long-term burning on substrate quality that reduced rates of mineralization. The treatment influence on mineralizable N was more apparent during the latter 24 d of laboratory incubation, whereas the initial 4 d reflected the influence of sampling date to a greater degree. From this pattern, it is hypothesized that the initial 4 d of incubation are more indicative of field environmental conditions, whereas the latter 24 d reflect the quantity of mineralizable substrate present. Although treatment differences in extractable and mineralizable N were statistically significant overall, the lack of statistical differences at some dates indicates the importance of seasonal sampling.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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