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Minimum stand densities necessary to achieve crown closure is an important aspect of stocking assessment that merits more attention. Managers concerned with optimizing individual-tree and stand-level responses will benefit from improved guidance on minimum densities when designing intermediate silvicultural treatments. To do so we generated a dataset of crown projection areas using previously published crown width models and considered various assumptions about crown packing and the spatial arrangement of stems. Implied stem densities based on predicted crown sizes were used to determine the minimum stand density index (SDI MIN) by species. These values were integrated with published information about maximum stand density index (SDI MAX) providing estimates of minimum relative density (RD MIN =SDI MIN /SDI MAX). Mixed-effects models were used to predict RD MIN and determine the slope of the minimum size-density relationship (mSDR) for common softwood and hardwood species in northern New England, USA. Large differences in crown-stem allometry were revealed between open- and forest-grown trees (ΔRD ∼0.2). Hardwoods occupied more growing space than softwoods (ΔRD ∼0.05), a finding primarily attributed to differences in crown architecture, though species shade-tolerance may also play a role. Minimum stem densities capable of achieving crown closure span a wide range determined by species composition and stand history. Importantly, the implied slope of mSDR (∼ −1.0) differed substantially from that of the benchmark maximum size-density relationship (MSDR; −1.605), corresponding to lower values of RD MIN for smaller-sized stems and earlier in stand development than when stems are larger and older. Our models and resulting estimates of RD MIN can be used to locate the lower boundary of stocking space on size-density diagrams. • In contrast to maximum stem densities, the quantification of minimum numbers has not received adequate attention. • The slope of the relationship between minimum stem density and average size diverges substantially from that for the maximum. • Full site occupancy is possible at surprisingly low levels of relative density, and more so for hardwoods than softwoods. • tand history is important to consider when interpreting and using size-density management charts. [ABSTRACT FROM AUTHOR]

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Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Determining the optimal timing and type of entry in mid-rotation, unthinned stands can be complicated by a variety of economic and biological factors. In this analysis, long-term data from the Commercial Thinning Research Network was used to project spruce-fir (Picea spp.—Abies balsamea (L.) Mill.) stand growth on six different sites across Maine following six alternative thinning treatments (33% and 50% relative density removal paired with low, crown, and dominant thinning methods). Results showed that the low-thinning treatment performed best in terms of maximum net present value, stand age at time of maximum net present value, and average merchantable stem size. Although the low-thinning resulted in a 10% mean reduction in maximum net present value when compared to the control, the average merchantable stem size more than doubled. Overall, results of this analysis indicate that it may be financially responsible to commercially thin these stands using a low-thinning method and a light removal intensity, as the average merchantable stems size was increased and a mid-rotation financial return provided. [ABSTRACT FROM AUTHOR]