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The abundance of Picea jezoensis, a major conifer tree species in Hokkaido, northern Japan, is currently decreasing due to the lack of suitable conditions for recruitment and intensive harvests. To contribute to the development of sustainable forest management in Hokkaido, suitable substrates for natural regeneration of P. jezoensis were evaluated during a 4-year experimental study using seed additions in a natural coniferous forest. The environmental conditions (moss height, log hardness, extent of the humus layer, and light conditions) of fallen logs were measured. Moss height was categorized into three groups: 0 mm, Bark; 0 - 20 mm, Mthin; and ≥ 20 mm, Mthick. The germination rates of P. jezoensis were highest on Mthin, intermediate on Bark, and lowest on Mthick. Survival rates were low on Mthick, did not differ between Bark and Mthin, and increased with enhanced light. Growth increased with light, but the root allocation of seedlings was not affected by any environmental conditions. From these results, we determined that fallen logs with no or thin moss cover under bright conditions were most suitable for P. jezoensis regeneration. We discussed the generality of our results in relation to a co-occurring tree species in Hokkaido and the results of other regions

Citation: Kosugi, R., M. Shibuya, and S. Ishibashi. 2016. Sixty-year post-windthrow study of stand dynamics in two natural forests differing in pre-disturbance composition. Ecosphere 7(11):e01571. 10.1002/ecs2.1571Abstract. We examined the dynamics of stand structure and composition over 60 years in two natural secondary forest plots in central Hokkaido, Japan, that had been severely disturbed by a stand-replacing windthrow in 1954. We determined temporal trends in tree density, species richness, species diversity, successional composition, and stand developmental stage. One of the plots contained a coniferous stand prior to the disturbance; the second plot contained a mixed stand. Tree density and species richness increased after the windthrow, and peaked in both stands in 1991, 37 years after the windthrow. Based on the dynamics of tree density and species richness, the stand development phase of both plots remained within the stand initiation stage until 1991, and then progressed to the stem exclusion stage by 2014, 60 years after the windthrow. Based on patterns of increasing tree density by species in both plots, vegetative regeneration was presumed to have contributed abundantly to the recovery of the stand after the windthrow. Species diversity increased after the windthrow as species richness increased in both stands; diversities peaked 23 or 32 years after the windthrow and declined slightly thereafter. Although the successional composition of the pre-disturbance coniferous stand regressed to an early stage under the influence of the windthrow, the relative importance of late-successional species approached the pre-disturbance value as the plot recovered. In contrast, the successional composition of the mixed conifer/hardwood plot was unaffected by the windthrow, but gradually changed to an early stage over several decades following the windthrow. The difference in successional composition between plots was likely a result of differences in pre-disturbance stand conditions between stands. Our 60-year permanent plot study determined stand and population dynamics, the duration of the stand initiation stage, and the interrelationships between diversity and species richness. Long-term permanent plot studies contribute crucial data for the interpretation of forest dynamics following disturbance.

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We examined potentially contrasting conservation benefits of land sparing (land-use specialization) and land sharing (multiple-use forestry) strategies in forested landscapes by investigating relationships between bird functional group densities and basal areas of coniferous trees (an index of plantation intensity) in Sakhalin fir (Abies sachalinensis) and Sakhalin spruce (Picea glehnii) plantations. Densities of most bird functional groups increased with decreasing plantation intensity in both plantation types. In many cases, linear models were best for descriptors of bird density-plantation intensity relationships, but statistical support of linear and nonlinear (quadratic) models was similar. This outcome indicates that ecological benefits of land sparing and land sharing are potentially comparable in the plantations we studied. In real landscapes, land-use decision making depends on a variety of factors other than biodiversity conservation (e.g., social and biophysical factors). Furthermore, niche theory also predicts that population densities could linearly respond to environmental gradients. When density-intensity relationships are linear, as in this study, land-sparing and land-sharing strategies provide similar benefits in terms of biodiversity conservation, and contrasting land-use strategies could be flexibly chosen to enhance the accommodation of biodiversity conservation to resource production