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Human Impact
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The formerly extensive network of roads contributed to significant
soil compaction in the Giant Forest.
© NPS photo.
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Mature Sequoias
Scientific studies conducted in Giant Forest by Richard
Hartesveldt showed that development harmed mature sequoias
where major roots had been pruned for road or building
construction. In other situations, little or no negative
effects were detected on survival or growth rate of
individual mature sequoias, at least in the short term. There
were likely longer-term effects of development on mature
sequoias that had not been detected. Hartesveldt found that
soils under asphalt or in highly compacted areas were wetter
and warmer than in natural sites. This increase in soil
moisture and temperature may increase soil pathogens,
contributing to root-rot and tree failure in the long term.
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Photo center: cut surfaces of sequoia roots protrude
from a road cut in the Giant Forest. © NPS Photo by
Athena Demetry. |
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Continued development in Giant Forest would have greatly
increased the overall negative effect on the health of mature
sequoias. Replacing underground water and sewer systems would
have required additional cutting of mature sequoia roots.
Young giant sequoias, as well as many other trees, shrubs,
and wildflowers, would fail to regenerate because of impacts
to the soil and the absence of fire. Future generations would
see a forest radically different from what we see today.
Although the overall effect of development on the Giant
Forest grove is strongly negative, Hartesveldt found that in
some cases development increased the growth rates of mature
sequoias in the short term. He attributed this increased
growth in heavily used areas to higher soil moisture and
temperature. Soils are wetter and warmer in developed areas
because covering by asphalt and soil compaction help to
maintain soil moisture deep in the rooting zone throughout
the growing season, both by reducing evaporation from the
soil and by preventing growth of competing vegetation. In
addition, many of the competing trees surrounding monarch
sequoias were cleared when buildings and parking lots were
constructed, making a greater proportion of the limited soil
moisture and nutrients available for the mature sequoias.
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