IntensIve sIlvIculture - Forest Science Labs - Research Network ...

201
provided by litter. These findings suggested that other biological factors stimulated the growth of
conifer seedlings and (or) activity of mycorrhizal fungi.
459. Perry, D.A., C. Choquette and P. Schroeder. 1987. Nitrogen dynamics in conifer-dominated
forests with and without hardwoods. Canadian-Journal-of-Forest-Research 17(11): 1434-1441.
Keywords: release treatments
soil properties
tree morphology
Abstract: In studies on the E. slopes of the Oregon Coast Range, contents of N and C in the
surface 12 cm of mineral soil, N in leaf litterfall, anaerobic N mineralization rates in the soil and
forest floor, and root and N accretion to sand traps placed in surface soil layers were studied in
stands dominated by Douglas fir trees, from which the broadleaved component had been partially
or completely removed during thinning 3 yr earlier. Contrary to expectations, stands without
broadleaved species had more N in mineral soil, a greater rate of anaerobic soil N mineralization
and a lower soil C : N ratio than stands with broadleaved species. These variables did not differ
between thinned and unthinned mixed stands. From litterfall and sand trap data, it is suggested
that N was redistributed in the coniferous system after removal of the broadleaved species.
460. Petersen, T.D. and M. Newton. 1983. Growth of Douglas-fir following release from snowbrush
and forbs in the Oregon Cascades. Proceedings-of-the-Western-Society-of-Weed-Science:58-59.
Keywords: release treatments
chemical release
growth
Abstract: Ceanothus velutinus and other weeds such as Epilobium angustifolium, Rubus
ursinus and Pteridium aquilinum suppressed the growth of Douglas fir in plantations of the
central Cascades of W. Oregon. Stem vol. increases of Douglas fir after 4 yr were greatest when
all competing vegetation had been controlled for 1 growing season with herbicides. It is
suggested that C. velutinus competes with Douglas fir by depleting soil moisture although the
cause of competition by other weeds is unknown. The best time for releasing Douglas fir from
competition is discussed.
461. Petersen, T.D., M. Newton and S.M. Zedaker. 1988. Influence of Ceanothus velutinus and
associated forbs on the water stress and stemwood production of Douglas-fir. Forest-Science
34(2): 333-343.
Keywords: release treatments
chemical release
tree physiology
soil properties
growth
Abstract: In studies in the central Cascade Mts., Oregon, three regimes were established in
1978 around individual trees in four 5-yr-old and four 10-yr-old stands, viz. no treatment
(control), elimination of C. velutinus with 2,4-D or elimination of C. velutinus and forbs with 2,4-
D and glyphosate. Seasonal and diurnal variation in stem and soil water potentials were measured
during 1979. Soil water potential during late summer was