Journal of Conference Abstracts

Volume 2 Number 2

BIOGEOMON '97


Effect of Fire on Major Ion Chemistry of Undisturbed New Jersey USA Pinelands Streams

Mark D. Morgan1,2 (mdmorgan@crab.rutgers.edu) & Dennis Gray2

1 Department of Biology, Rutgers University, Camden, New Jersey 08102, U.S.A.

2 Division of Pinelands Research, Rutgers University, Camden, New Jersey 08102, U.S.A.

The New Jersey USA Pinelands covers approximately 400,000 ha in the southern portion of the state. The region consists of mostly undisturbed pine (Pinus rigida) and oak (Quercus spp.) forest and is underlain by highly weathered quartz sands. Surface waters are naturally extremely low in nutrients, acidic, and highly coloured due to high concentrations of iron and organic matter. Although total precipitation is relatively high (114 cm yr-1) and evenly distributed throughout the year, soils are excessively drained so that the upland vegetation experiences prolonged and chronic drought. Periodic wildfire is therefore a natural feature of this system (Forman, 1979). The purpose of this study is to elucidate the effect of fire on the major ion chemistry of undisturbed surface waters.

A major wildfire burned through large portions of the northeastern Pinelands in April, 1995. The fire was intense enough to kill most upland vegetation and burn through wetlands. In early May, 1995 we began monitoring of the major ion chemistry of 4 streams that were impacted significantly by the fire (Factory Branch, Cooks Branch, Cooks Branch West, and Webbs Mill Creek). We measured H+, Ca2+, Mg2+, Na+, K+, NH4+, Cl-, SO42-, NO3-, DOC concentrations, and conductivity. Two of the streams (Factory Branch and Cooks Branch) were also the subject of a previous water chemistry study in 1984-1986.

Previous research on the chemistry of Pinelands surface waters showed that stream chemistry is strongly influenced by season (Morgan and Good, 1988). Virtually all constituents occur at higher concentrations during the cold season (November to April). For the period beginning 6 months after the fire, the average chemistry of the fire impacted streams was virtually identical to the average cold season chemistry of similar streams in 1984-1986 (Morgan & Good 1988). Water chemistry during the warm season immediately after the fire was different than during the earlier period. Hydrogen ion concentrations were about 50 % lower and base cations were higher than expected. This pattern is directly illustrated by comparisons of the two streams common to both studies. Hydrogen ion concentrations were significantly lower and base cations were higher following the fire during the warm season in Factory Branch (P<0.05). Ammonium, Cl-, SO42-, NO3- did not change (P>0.05). Hydrogen ion and base cation concentrations were not different during the cold season (P>0.05). For Cooks Branch, H+ was 30 % lower following the fire, but not significantly (P=0.27). Base cations, however were significantly elevated (P<0.01). These data suggest that active export of base materials and neutralisation of the water occurred for at least six months following the fire.

References

Forman, R.T.T. (ed.), Pine Barrens: Ecosystem and Landscape. Academic Press, NZ (1979).

Morgan, M.D. & Good, R.E., Water Resour. Res. 24, 1091-1100 (1988).


BIOGEOMON '97
21-25 June 1997
Villanova University, Pennsylvania USA

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