Songbird response to experimental retention harvesting in red pine (Pinus resinosa) forests

Traditional harvesting practices frequently result in simplification of the structure and composition within managed forest stands in comparison to their natural counterparts. In particular, loss of heterogeneity within stands may pose a problem for maintaining biodiversity in perpetuity. In this study, we survey breeding bird diversity and abundance in response to different spatial harvesting patterns in mature red pine forests located on the Chippewa National Forest of northern Minnesota, USA. Treatments are designed to increase structural complexity over time and include three overstory manipulations (dispersed retention, aggregate retention with small gaps, and aggregate retention with large gaps), one understory manipulation (brush removal), and controls (no harvesting, and/or no brush removal). In 2003, the first breeding season following the harvest, we found little difference in bird community composition between control and treatment stands. In 2005, the third breeding season following harvest, avian abundance, richness, and diversity were all greater within treatments. Species associated with edge, shrub, and early successional habitats generally show positive response to treatments (e.g. Chestnut-sided Warbler [Dendroica pensylvanica], Mourning Warbler [Oporornis philadelphia], Chipping Sparrow [Spizella passerine]), as do some species associated with mature forest (e.g., Pine Warbler [Dendroica pinus], Rose-breasted Grosbeak [Pheucticus ludovicianus]). Ovenbirds (Seiurus aurocapilla) and Black-throated Green Warblers (Dendroica virens) were more abundant in control stands. There are, as of yet, no discernable differences in avian community composition among the three overstory treatments or between the single understory treatment and the understory control, but differences are expected as the treatments diversify due to understory development. While overstory retention harvests provide habitat for a diverse and abundant bird community, the temporal divergence in avian community composition that we observed between treatment and control stands reveals the importance of uncut, mature red pine forest as a component of a biodiverse landscape.     

Growth analysis on the competition–density effect in Chinese fir (Cunninghamia lanceolata) and Masson pine (Pinus massoniana) stands

The competition–density (C–D) effect for Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and Masson pine (Pinus massoniana Lamb.) stands was analyzed using the reciprocal equation of the C–D effect, i.e. 1/w=Aρ+B, where w and ρ, respectively, represent mean stem volume and stand density. The C–D curve, which is given by the reciprocal equation on logarithmic coordinates, shifted upward with the progress of time. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. The biological time τ defined as the integral of λ(t), the coefficient of growth in the general logistic growth curve, with respect to physical time t, tended to increase to an asymptote with increasing t. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (=wρ), increased abruptly up to a maximum value and then tended to decrease gradually to a constant level. On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume, decreased exponentially and tended to close to zero with increasing τ. The λ(t) decreased with increasing stand age, whereas the final yield Y(t) defined as W(t) ρ, where W(t) is the asymptote of w in the general logistic growth curve, tended to increase gradually with increasing stand age.     

Identification of Cylindrocladium sp. causing damping-off disease of Japanese black pine (Pinus thunbergii) and factors affecting the disease severity in a black locust (Robinia pseudoacacia)-dominated area

The regeneration of Japanese black pine (Pinus thunbergii) seedlings is inhibited in a black locust (Robinia pseudoacacia)-dominated area. We examined the presence of pathogenic fungi in Japanese black pine seedlings in the area in order to determine the effect of pathogenic fungi on the inhibition of regeneration. When Japanese black pine seedlings were planted in the soil obtained from a black locust-dominated area, all of the seedlings died under low-intensity light conditions, whereas 84% of the seedlings survived in the soil obtained from a Japanese black pine-dominated area under the same light conditions. One fungus was isolated from 48.7% of the dead pine seedlings and was identified as Cylindrocladium pacificum Kang, Crous & Schoch, based on the morphological characteristics, growth, and DNA analysis. This fungus was also isolated from 50% of the dead pine seedlings in 2005 and 66.7% of the seedlings in 2006—both were planted in a black locust-dominated area. The virulence of this fungus increased under high-nitrogen and/or low-intensity light conditions. These results reveal the possibility that the soil eutrophication and shading by the black locust are conducive to a severe damping-off disease and threaten the survival and regeneration of Japanese black pine seedlings.     

呼伦贝尔沙地樟子松生产力及其对气候因子的响应

目的 森林在减缓温室气体浓度和气候变化方面发挥着巨大作用,研究不同密度下林分生产力及其对气候的响应有助于森林生态系统的功能评估及适应性管理。 方法 本研究利用树木年轮学方法得到了呼伦贝尔沙地不同密度（用林分胸高断面积表示）的天然樟子松林净初级生产力,并结合气象因子分析其对温度、降水及干旱指数的响应。 结果 表明：胸高断面积为8.83、21.94、24.28、32.36和34.9 m2·hm−2的樟子松林的多年平均净初级生产力分别为1.17、2.99、3.55、4.69和4.86 t ·hm−2 ·a−1,随样地密度增加而增加;高密度樟子松林净初级生产力与上年7月和当年9月平均气温及平均最高气温显著正相关（P＜0.05）;5月降水是天然樟子松林净初级生产力的关键限制因子,所有密度林分的净初级生产力均与当年5月降水显著正相关（P＜0.05）;自上年11月至当年7月,净初级生产力与帕默尔干旱胁迫指数（PDSI）的相关系数随林分密度增加而减小,表明林分竞争的增加导致了净初级生产力对PDSI敏感性的降低。 结论 林分密度对呼伦贝尔沙地天然樟子松的净初级生产力及其气候响应存在明显影响,密度调整可能是气候变化下森林适应性管理的关键措施。     

Spatial distribution and sampling of Thaumetopoea pityocampa (Den. & Schiff.) (Lep. Thaumetopoeidea) populations on Pinus pinaster Ait. in Montesinho, N. Portugal

The pine processionary moth, Thaumetopoea pityocampa (Den. & Schiff.) is one of the most destructive pine pests in the Mediterranean countries. The first objective of this study was to analyse the spatial distribution of this insect on the tree on Pinus pinaster Ait., in northeast Portugal. The second objective was to develop two sampling plans: a sampling plan with fixed levels of precision for estimating T. pityocampa populations and a sequential sampling plan to classify the pest. Population estimates were made by registering the number of insect egg batches on 90 trees distributed over 3 stands during a 3-year study (1997–2000). Taylor's power law and Iwao regression were used to analyse the spatial distribution of the pest. Taylor's power law fitted the data better (r² = 0.775) than Iwao's regression model (r² = 0.704). The aggregation indices (b and β) were both significantly greater than one, indicating the aggregation of T. pityocampa egg batches. Optimal sample sizes for fixed precision levels of 0.10, 0.15 and 0.25 were estimated with Taylor's regression coefficients. Required sample sizes increased dramatically with increased levels of precision. The two sampling plans presented should be a tool for research on population dynamics and pest management decision.     

The influence of silvicultural treatments and site conditions on American chestnut (Castanea dentata) seedling establishment in eastern Kentucky, USA

After more than 50 years of research and selective breeding, blight-resistant American chestnut (Castanea dentata) trees will soon be available for planting into the species’ pre-blight range. Increased understanding of the regeneration requirements of pure American chestnut (C. dentata [Marsh.] Borkh.) will increase the success of future efforts to establish blight-resistant chestnut. We quantified survival and initial growth of bare-root American chestnut seedlings at five locations in eastern Kentucky, USA. We used a split-plot design to compare seedlings planted within adjacent mesic and xeric sites treated with either a two-age shelterwood overstory treatment or a midstory removal treatment. The silvicultural treatments and topographic settings allowed us to evaluate chestnut seedling performance under four light and site productivity combinations. Seedling survival was 57% and seedling height averaged 94 cm following two growing seasons. Seedling survival was negatively related to sand and coarse fragment content, but was unrelated to silviculture treatment or topographic position. Chestnut seedlings grew best in shelterwood overstory treatments areas on mesic sites. Seedlings growing in shelterwood overstory treatment areas added 3- and 3.5-times more height and stem increment compared to seedlings planted after midstory removal. Seedling leaf mass and foliar nitrogen (N) content were also greatest in shelterwood plantings on mesic sites. The high-light environment created by shelterwood overstory removal resulted in better initial seedling growth, but the moderate-light of the midstory removal treatment may ultimately provide chestnut seedlings a greater advantage over competing vegetation.