Dd. Reed et al., EFFECTS OF 76 HZ ELECTROMAGNETIC-FIELDS ON FOREST ECOSYSTEMS IN NORTHERN MICHIGAN - TREE GROWTH, International journal of biometeorology, 37(4), 1993, pp. 229-234
Since 1984, the possible effects of extremely low-frequency electromag
netic (EM) fields generated by a 76 Hz communication antenna on the gr
owth and productivity of four deciduous and one coniferous species hav
e been studied in the Upper Peninsula of Michigan. Results from two re
search sites are discussed here: one site near an antenna element and
a control site located 50 km from the communication system. Growth mod
els for individual tree diameters were developed for northern red oak
(Quercus rubra), paper birch (Betula papyrifera), aspen (Populus tremu
loides with a few individuals of P. grandidentata), and red maple (Ace
r rubrum). A growth model for individual tree height was developed for
young red pine (Pinus resinosa). Average differences between the obse
rved and predicted growth were calculated for each growing season and
then compared between the study sites and across the study periods to
evaluate changes in growth patterns which could be attributed to EM fi
eld effects. For aspen and red maple, the results showed a stimulation
of diameter growth at magnetic flux density levels of 1 to 7 milliGau
ss; height growth of red pine was increased at about the same exposure
levels. There are no clear indications of an EM field effect on total
annual diameter growth for either of the other two species.