Environmental Engineering Reference
In-Depth Information
white oak is able to maintain high soil fertility, through return of nutrient rich litter
and rapid mineralization of nutrients (Singh and Singh
1992
). Total soil N was 0.48
and 0.41 % in valley areas, and 0.38 and 0.39 % in ridge areas (at 0-10 and 10-20 cm
soil depths, respectively). If fi re occurs at the time when other environmental factors
are in favour of oak it regenerates vigorously (Negi
2002
) and paradoxically out
competes pine from the site.
Q. leucotrichophora
has an expanding population structure. As the disturbance
in the form of forest fi re and lopping has been excluded for some time in the past the
oak was able to reestablish and expand. A few years after the oak establishment
several of its associates like
Q. fl oribunda
,
Pyrus pashia
,
Ficus
sp.
L. ovalifolia
have
joined the sites. Most of these species were absent in adjacent pine forest (Garkoti
pers. Communication). It seems that return of white oak ameliorates the habitat
conditions (e.g., N and moisture) which allows these associates to occupy the avail-
able niches in the community.
The establishment of oak after fi re damages the pine poses a question as to how or
what conditions make a climax species (oak) to replace a successional species (pine)
after the disturbance (ecological knowledge so far refl ects the opposite). Severe fi re
in the pine forests removes individuals of all the species present. In the dry and sunny
mountain ridges pine always reoccupies the area after the fi re damages. On dry
slopes especially once the area comes under pine it reduces the available N pool in
the soil through immobilization properties of its decomposing litter (Singh et al.
1984
). As white oak has comparatively higher demand for N and other nutrients than
pine, it is not able to reinvade the areas from where it is displaced by the pine.
However, in certain years, after the fi re that removes pine, oak is paradoxically able
to occupy the sites in moist valley areas. It seems that nutrients required by oak
would be fl owing down to valley sites from the mountain slopes through surface and
subsurface runoff during rainy seasons and sites remain favourable for oak. If fi re
occurs at the time when other environmental factors such as high moisture associated
with lower temperature are in favour of white oak, it regenerates vigorously and out
competes chir pine in those sites. Once the oak gets established it further improves
nutrient status of the habitat and makes habitat favourable for its associates from the
adjacent forests. The wash off of nutrients from the slopes that brings soil and nutri-
ents improves the moisture as well as nutrient status in valley areas. Once estab-
lished, white oak is able to maintain high soil fertility, through return of nutrient rich
litter and rapid mineralization of nutrients (Singh and Singh
1992
).
Conclusion
In both the sites of the present study, white oak has expanding population structure
indicating natural regeneration of oak and restoration of the habitat. It seems that
establishment of white oak results in improvement of soil nutrient capital (as evi-
denced from the soil N) which in turn facilitates the arrival of its several associates
in the community and results in increase in stand diversity. Disturbances are now
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