Twelve-year responses of planted and naturally regenerating conifers to variable-retention harvest in the Pacific Northwest, USA

Urgenson, Lauren S.; Halpern, Charles B.; Anderson, Paul D.

doi:10.1139/cjfr-2012-0323

Cited by 26 publications

(24 citation statements)

References 35 publications

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“…These results contrast with reductions in stem density and biomass observed in P. tremuloides-dominated systems with 40% basal area retained [38]. However, our results align with findings that retention level (up to 50% basal area retained) had little effect on total or specifically aspen/birch sapling densities [22] and that stem density may be less impacted by retained overstory trees than growth rates [27]. Comparable eucalypt densities and growth rates between harvests with aggregated retention compared to clearcuts also suggests negative impacts on crop tree regeneration may be less of a concern in some systems [60].…”

Section: Discussionsupporting

confidence: 78%

Influence of Mature Overstory Trees on Adjacent 12-Year Regeneration and the Woody Understory: Aggregated Retention versus Intact Forest

Curzon

Baker

Kern

et al. 2017

Forests

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Abstract:Retention harvesting, an approach that intentionally retains legacy features such as mature overstory trees, provides options for achieving ecological objectives. At the same time, retained overstory trees may compete with the nearby recovering understory for resources, and much remains to be learned about potential trade-offs with regeneration objectives, particularly over extended time periods. We assessed the influence of aggregated retention (reserved mature overstory and understory patches) versus intact forest on structure and productivity (standing biomass) of the adjacent woody understory and regeneration 12 years after harvest in northern Minnesota, USA. Each site was dominated by Populus tremuloides Michx., a species that regenerates prolifically via root sprouts following disturbance. Overall, fewer differences than expected occurred between the effects of intact forest and aggregated retention on regeneration, despite the small size (0.1 ha) of aggregates. Instead, harvest status and distance from harvest edge had a greater influence on structure and standing woody biomass. Proximity to aggregates reduced large sapling biomass (all species, combined) relative to open conditions, but only up to 5 m into harvested areas. This suggests the trade-off for achieving productivity objectives might be minimal if managers use retention aggregates in this region to achieve ecological objectives and meet management guidelines.

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Section: Discussionsupporting

confidence: 78%

Influence of Mature Overstory Trees on Adjacent 12-Year Regeneration and the Woody Understory: Aggregated Retention versus Intact Forest

Curzon

Baker

Kern

et al. 2017

Forests

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“…Previous research in stands harvested with partially retained overstories has demonstrated a negative correlation between regeneration growth and understory shrub cover (e.g., Harrington 2006, Mitchell et al 2007, Urgenson et al 2013, Palik et al 2014. Our results seem to support this argument, because we found a negative correlation of current regenerated tree density to both shrub biomass 2 yr and shrub biomass 2-10 yr .…”

Section: Effect Of Understory Vegetation Treatmentssupporting

confidence: 84%

Long-Term Regeneration Responses to Overstory Retention and Understory Vegetation Treatments in the Northern Rocky Mountains

Jang¹,

Keyes²,

Page‐Dumroese³

2017

Forest Science

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Classic regeneration cuttings retaining trees at harvest (shelterwood with reserves, group selection) can be analyzed as analogs of variable-retention harvesting. A 1974 silvicultural experiment in the northern Rocky Mountains was analyzed at 38 years to evaluate the long-term effects of retention harvests on stand development, with a focus on both regeneration and retention tree responses. The postharvest understory treatments (understory removed and broadcast burned) effects were also evaluated. Results indicate that overstory retention results in relatively long-term regeneration growth reduction. Compared with the overstory-free condition (clearcut), the shelterwood with reserves and group selection overstories both reduced the regenerated cohort's basal area, 63 and 44%, respectively. Postharvest burning increased regeneration stem density and also decreased mean regenerated tree size; consequently, these treatment effects were somewhat offsetting, as they produced a zero net difference in regenerated cohort basal area. Considerable regeneration growth reduction associated with retained overstory trees in the shelterwood with reserves was partially mitigated by understory vegetation protection measures that conserved advance regeneration. We conclude that both retention treatments somewhat suppressed regenerated cohort development, but that these impacts were lessened when overstory trees were aggregated and cuttings were in groups, rather than regularly dispersed through the cutting unit.

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“…The variability in stand conditions prior to restoration treatments was reflected in a high variability in the spatial distribution of advanced regeneration. The species composition and densities of the cohorts that initiated after the restoration treatments were highly variable at small spatial scales [51]. However, the densities of tree regeneration did not differ sufficiently to result in statistically significant differences between treatment averages.…”

Section: Tree Regeneration (Natural)mentioning

confidence: 87%

Forest Restoration Using Variable Density Thinning: Lessons from Douglas-Fir Stands in Western Oregon

Puettmann

Ares

Burton

et al. 2016

Forests

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A large research effort was initiated in the 1990s in western United States and Canada to investigate how the development of old-growth structures can be accelerated in young even-aged stands that regenerated following clearcut harvests, while also providing income and ecosystem services. Large-scale experiments were established to compare effects of thinning arrangements (e.g., spatial variability) and residual densities (including leave islands and gaps of various sizes). Treatment effects were context dependent, varying with initial conditions and spatial and temporal scales of measurement. The general trends were highly predictable, but most responses were spatially variable. Thus, accounting for initial conditions at neighborhood scales appears to be critical for efficient restoration. Different components of stand structure and composition responded uniquely to restoration thinnings. Achieving a wide range of structures and composition therefore requires the full suite of silvicultural treatments, from leave islands to variable density thinnings and creation of large gaps. Trade-offs among ecosystem services occurred as result of these contrasting responses, suggesting that foresters set priorities where and when different vegetation structures are most desirable within a stand or landscape. Finally, the results suggested that foresters should develop restoration approaches that include multiple treatments.

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Twelve-year responses of planted and naturally regenerating conifers to variable-retention harvest in the Pacific Northwest, USA

Cited by 26 publications

References 35 publications

Influence of Mature Overstory Trees on Adjacent 12-Year Regeneration and the Woody Understory: Aggregated Retention versus Intact Forest

Influence of Mature Overstory Trees on Adjacent 12-Year Regeneration and the Woody Understory: Aggregated Retention versus Intact Forest

Long-Term Regeneration Responses to Overstory Retention and Understory Vegetation Treatments in the Northern Rocky Mountains

Forest Restoration Using Variable Density Thinning: Lessons from Douglas-Fir Stands in Western Oregon

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