Interactive Effects of Stock Type and Forest Vegetation Management Treatments on Douglas-Fir Seedling Growth and Survival—Ten-Year Results

Abstract

In the Pacific Northwest, the use of forest vegetation management (FVM) and seedling stock type selection are important tools to ensure seedling establishment according to organizational objectives and state laws. Individually, these two reforestation decisions have been shown to increase growth and survival of Douglas-fir seedlings, however, the interaction between seedling stock type and level of vegetation control represents economic and ecologic tradeoffs that are less well understood. This study was designed to test the combined effects of three FVM regimes and three containerized stock types, one of which was experimental at the time, on Douglas-fir growth during the initial ten years of establishment on a site near Belfair, Washington (USA). When compared to the no-action control, FVM treatments reduced competitive plant cover below 20% during the year of application, and differences in vegetation cover persisted through the fifth growing season. Vegetation species diversity recovered quickly after FVM and there were no differences among the treatments by the third growing season. After ten growing seasons, trees in plots treated with FVM were 1.1 m taller with a mean diameter at breast height (DBH) 2.2 cm larger than those in the no-action control. Larger seedlings at the time of planting (styro-60) were 0.6 m taller with a mean DBH 1.1 cm larger than smaller seedlings (styro-8 and styro-15). The only significant stock type by FVM interaction in the experiment occurred with the survival of styro-60 seedlings growing in the no action control which had lower survival than all other treatment combinations (67% vs 91%). The long-term competitive impact of shrub cover was demonstrated by a strong non-linear relationship. Increasing cumulative shrub cover from 10% to 30% during the first two years of establishment reduced stand volume at year 10 by 79%.

Determination of the Environmental Factors that Affect the Growth and Survival of Greek Fir Seedlings

“…The positive effect of individual attributes related to seedling vigour, represented in this study by the values of height at planting, was confirmed in both contexts (Tables 3, 5 and 6 and Figure 3) [36]. However, initial height contributes very little to explaining the variation in annual apical growth.…”

“…In the flysch_mixed site group, in which fir was subdominant prior to fire, growth rate was positively affected in the first year after planting compared to ls_fir and negatively thereafter ( Table 5 and Figure 3). Probably resprouting evergreen and deciduous broadleaf plants had a nurse effect in the first year, which fades later on [39] (see also [36]) and/or the very low clay content of the soils in these sites drastically reduced water stress during the early phase of establishment compared to the other sites, from then on the unsuitability of the sites compared to the others surfaced [20]. The negative effect is stronger in higher quantiles indicating a genuine limiting factor from year 2 of the study onward.…”

Effects of manual brushing on 10-year survival and growth of Douglas-fir in the mixed broadleaf – shrub complex of southern interior British Columbia

“…In the longer term, without additional brushing or thinning treatment it is expected that overall stand productivity of these brushed sites will partition into broadleaf and Douglas-fir components resulting in complex stand dynamics dependent on species productivity, competition intensity, density and canopy occupancy. Also, concerns over climate change and the increased frequency of seasonal drought in southern BC forests have renewed interest in the potential for brushing treatments to increase the availability of soil moisture through reduced evaporative demand and soil moisture stress resulting in significant increases in survival and growth of planted Douglas-fir (Wightman et al 2019). Douglas-fir may utilize carbon assimilated by birch and shared, possibly, through ectomycorrhizal networks (Simard et al 1997); other resources may be shared as well (e.g., Gorzelak et al 2015), potentially providing some resilience to stresses exacerbated under a changing climate.…”

The Influence of Minimal Cultivation Techniques on Growth Rate of Robinia pseudacacia L. Seedlings

“…Substrates have been the subject of several studies over time for coniferous and deciduous species [23][24][25][26][27][28][29][30]. The influence of the substrate on the growth of containerized black locust seedlings was addressed in several studies.…”