TREE GROWTH

other words, the long series of very narrow

Disease, damage, or climatic factors could

interval of injection mining.

A twenty year sequence of unusually wide

rings began about 1960 or shortly thereafter

(fig. 1), indicating that conditions for tree

growth improved strikingly and quickly. The

onset of this "growth release" in wetland

pines coincides with closure of the eastern

part of the brine field in 1957 and the

brine and the absence of injected waters

reduced flow to the bedrock fractures and

thus reduced the flow of brackish springs as

far north as the wetland. Flow patterns of the

precipitation-driven freshwater springs were

not altered, however, resulting in the

progressive drying of waterlogged soils

an upland than a wetland. Ifthis

interpretation is correct, wetland trees that

started to grow after 1960 would be expected

to have very wide rings rather than the

narrow rings typical of trees established

during the interval of injection mining, and

indeed this was the finding.

The growth of some trees declined during

the early 1980s, apparently as the result of

regional drought. However, instead of

recovering from drought when conditions

improved in following years, many trees

continued to grow even more poorly from the

late 1980s to the present (fig. 1). Some trees

died during the mid 1990s and others show

signs of poor health suggesting that they too

may soon die. Although it might appear that

the demise of trees is due simply to

overwatering, this does not seem to be the

case. Chemical analysis indicates that

formed during the early to mid 1990s.

Moreover, affected trees grow closest to the

brackish springs, those intermediate in

distance show mild symptoms, and those

most distant appear healthy.

Thecessationofbrinewithdrawalsin

1988 reestablishedflowtobedrock

frac turesinthemining areaandto the

brackishsprings. Thus, the growthoftrees

againslowed assaturatedsoilconditions

persistedlongerinto thegrowingseason.

Unlikeirrigationofthewetland from lost

injectedwaters,however,the newflows

brinecavities. Thedemiseofwetlandtrees

seemingly is related more to this change in

water quality than to the quantity of

increased flows. To strengthen this

contention, chloride was measured in the

oldest trees in rings that formed before,

during, and after mining. As expected,

chloride concentrations were low in rings

that formed before the onset of mining,

higher in rings that formed during the 1890-

1960 period of injection mining, lower again

thereafter during the 1960-1986 period, and

highest following the cessation of mining.