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(and other measures of overstorey density) just after thinning. In thinned stands, the density of
small trees (intermediate crown class overstorey trees and advanced regeneration) was 159/ha,
significantly greater than in unthinned stands (90/ha), but not significantly different from that of
old-growth (204/ha). The live crown ratio of these trees in thinned stands (66%) was greater than
in unthinned (44%) and old-growth (48%) stands. Cover and stem density of shrubs was variable
in all 3 stand types. There was significantly less tall shrub cover in unthinned stands than in either
thinned or old-growth stands, which did not differ. Thinned stands had the most low shrub cover.
Salal (Gaultheria shallon) and bracken fern (Pteridium aquilinum) cover was greater in thinned
stands than in the other stand types, but there was no difference in sword fern (Polystichum
munitum) and Oregongrape [Berberis nervosa] cover. Leaf area index in thinned stands (6.6) was
not significantly different from that in unthinned (6.8) and old-growth stands (7.1); however,
there was more leaf area in shrubs in the thinned stands. Thinning young Douglas-fir stands will
hasten the development of multistorey stands by recruitment of conifer regeneration in the
understorey as well as by enabling the survival of small overstorey trees and growth of advanced
understorey regeneration. Thinning will also help develop the shrub layer by increasing tall shrub
stem density and cover of some low shrubs.
33. Bailey, V.L., J.L. Smith and H. Bolton, Jr. 2002. Fungal-to-bacterial ratios in soils investigated
for enhanced C sequestration. Soil-Biology-and-Biochemistry 34(7): 997-1007.
Keywords: fertilization
soil properties
Abstract: Fungi and bacteria govern most of the transformations and ensuing long-term
storage of organic C in soils. We assessed the relative contributions of these two groups of
organisms to the microbial biomass and activity of soils from five different ecosystems with
treatments hypothesized to enhance soil C sequestration: (1) desert (an elevation gradient allowed
comparison of soil developed in a cooler, wetter climate with soil developed in a warmer, drier
climate), (2) restored tallgrass prairie (land reverted to native prairie in 1979 and neighbouring
land farmed to row crops for ~100 year), (3,4) two forest types (Douglas fir [Pseudotsuga
menziesii] and loblolly pine [Pinus taeda], unfertilized control and N-fertilized plots), and (5)
agricultural land (conventional- and no-till management systems). The selective inhibition
technique, using captan (fungicide) and oxytetracycline hydrochloride (bactericide), was used to
determine the activities (respiration) of fungi and bacteria in each of these soils and substrateinduced
respiration was used to measure total active soil microbial biomass C. Phospholipid fatty
acid analysis was used to determine the composition of the soil microbial biomass and determine
if the activities and structure of the microbial communities were related. Differences in fungal-tobacterial
(F:B) activities between treatments at a site were greatest at the prairie sites. The
restored prairie had the highest F:B (13.5) and high total C (49.9 g C kg-1 soil); neighbouring soil
farmed to maize had an F:B of 0.85 and total C of 36.0 g C kg-1 soil. Within the pairs of study
soils, those that were tilled had lower fungal activities and stored C than those that were managed
to native or no-till systems. In all pairs of soils, soils that had higher absolute fungal activities
also had more total soil C and when two extreme cases were removed fungal activity was
correlated with total soil C (R2=0.85). Thus, in this small set of diverse soils, increased fungal
activities, more than F:B ratios, were associated with increased soil C. Practices that involved
invasive land management decreased fungal activity and stored soil C compared to similar soils
that were less intrusively managed.
34. Ballard, T.M. 1984. A simple model for predicting stand volume growth response to fertilizer
application. Canadian-Journal-of-Forest-Research 14(5): 661-665.
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