核桃大树芽接对树冠恢复、主干感病及产量的影响

在非目的品种核桃大树上利用方块形芽接方法,探求与核桃树地径相适应的预留橛数和嫁接芽数,以期为核桃生产中的大树芽接技术提供操作依据。在相同肥力地块选择相同地径水平的核桃树作 为砧木,设置单因素4 处理试验。第1 年短截骨干枝,第2 年在新生嫩枝上采用方块形芽接技术嫁接目的品种芽块。接后从第2 年开始,连续3 年调查核桃树冠直径恢复情况、主干感染腐烂病的情况及单位面积产量。最终总结出合理的留橛数和嫁接芽数。调查结果表明,在一定范围内预留橛数越多,嫁接芽数越多,树冠恢复就越快,主干感病越轻,产量恢复也越快。对于地径在20~25 cm内的核桃大树应预留16 个树橛,嫁接40 个芽为宜。试验探求了一套成活率高,树冠及产量恢复较快,且树干不易感病的核桃大树芽接技术,为核桃生产中的大树芽接提供参考依据。     

毛纤维直径及成分测试方法标准制定中重要技术指标的确立

[目的]制定毛纤维直径及成分分析仪的检测方法标准,确立标准中的重要技术指标,以利于仪器的正确使用。[方法]采用查阅资料、专家咨询及实验室检测等方法。[结果]确定了标准名称、纤维片段截取长度、截取方法、允许误差率及试验纤维根数等重要技术指标。[结论]该研究为毛纤维直径及成分检测方法标准的制定提供了理论依据。     

控根育苗技术引进试验初步效果

为提高森林城市建设工程质量,赤峰市林业科学研究所从陕西杨凌引进澳大利亚先进的控根快速育苗技术,对17种树木分3种不同规格容器进行培育试验,对树木成活率、生长量和增根效果进行调查分析,结果表明:树木成活率为97%,当年高度生长量在0.3~0.9m不等,均优于大田树木;用纵切1/4根系的方法测量根系鲜重,平均鲜重为0.120kg,约是大田对照鲜重的2倍。       

The influence of cutting cycle and stocking level on the structure and composition of managed old-growth northern hardwoods

Forest management approaches are increasingly being focused on restoring or retaining structurally complex old forest conditions. Evaluations of the long-term impacts of different management regimes on the maintenance and restoration of these conditions are critical for informing and refining current management approaches. To this end, we examined the long-term effects of differing intensities of single-tree selection harvest on stand structural attributes within northern hardwood forests in the Upper Peninsula of Michigan, USA. Stands in this study were classified as old growth at the onset of the experiment and were repeatedly treated and maintained at three residual stocking levels (11.5, 16.1, and 20.7 m² ha⁻¹ in trees greater than 24 cm DBH) with three different cutting cycle lengths (5, 10, and 15 years) over a 57-year period. Conditions within an adjacent, unmanaged old-growth system were used as a benchmark for comparing stand structural attributes, including abundance of downed woody debris (DWD), regeneration, and large diameter trees.     

Retention of native vegetation within the plantation matrix improves its conservation value for a generalist woodpecker

The suitability of plantation monocultures for the conservation of forest animals is an issue under continous debate. The adaptability of forest dwellers and the forest management regime seem to play key roles. In this study, I investigated the habitat selection of a generalist bird, the great spotted woodpecker (Dendrocopos major), within a pine (Pine spp.) monoculture, as well as the importance of the native habitat features within the pine matrix for the species’ conservation. I compared 52 plots with woodpecker presence against 121 plots where the species was absent, as well as 68 nest-trees against 90 random ones. Regression analyses were used to investigate the habitat attributes involved in the habitat selection. Although the great spotted woodpecker is considered a generalist forest dweller, it shows a marked habitat selection. Based on presence/absence records, the woodpecker prefers well-forested patches with high levels of tree diversity and with good coverage of a secondary species such as the strawberry tree (Arbutus unedo). To excavate their nests, woodpeckers select large trees in patches where other trees are also larger, rejecting patches with a high number of small trees. The most striking conclusion from this work is the preference shown for native trees, especially Portuguese oaks (Quercus faginea), as nest-trees. This is noteworthy because native trees are smaller and they are surrounded by smaller trees than pines. These findings support that woodpecker conservation benefits from an increase of habitat heterogeneity, particularly by the retention of native woodland patches within the plantation matrix.     

不同种源杉木幼苗早期造林生长状况比较分析

该文以1.5代种子实生苗、2代种子实生苗、3代种子实生苗、延平种子苗、顺昌无性系5种不同类型的杉木优良材料为研究对象,在南平延平区林地泛自然条件下进行了早期造林生长比较试验。调查分析结果表明,2代、3代种子苗的树高、地径生长在前2a略占优势;2a后,1.5代种子苗逐渐表现出优势,而顺昌无性系不论是树高、地(胸)径,还是单株材积,在参试的5种杉木材料中表现都不及其他。据此推断,延平种子苗可能更适宜南平延平区生长,其次是1.5代种子苗,但仍需继续跟踪调查。     

The limiting irregularity of single wool fibers

Fiber irregularity affects fiber mechanical properties. This study has, for the first time, introduced the concept of limiting irregularity to single wool fibers. The limiting irregularity is the minimum variation in fiber cross sectional area that can be expected of a single wool fiber, assuming a random length-wise distribution of its constituent cortical cells. Cortical cells were extracted from merino wool fibers and their dimensions were measured from SEM images to calculate their cross sectional area variations both between cortical cells and within cortical cells, and to work out the average number of cortical cells in the cross section of wool fibers of a given diameter. Single wool fibers were also measured at 5 μm interval along length for fiber diameter variations. These variations were found to be larger than that based on fiber limiting irregularity.     

Modelling the impacts of various thinning intensities on tree growth and survival in a mixed species eucalypt forest in central Gippsland,Victoria, Australia

The response of tree survival and diameter growth to thinning treatments was examined over 29 years, in various thinning treatments established in a 21-year-old even-aged mixed species regenerating forest in Victoria, Australia. The treatments were control, crown release, strip thinning and three different intensities of thinning from below (light, moderate, and heavy). Each treatment was replicated three times in a complete randomised design. Logistic and multilevel regression analyses showed that tree survival, growth and thinning response (change of tree growth due to a thinning treatment) were functions of tree species, size, age, removed and remaining competition, as well as time since the treatment. Mean annual tree diameter growth in unthinned stands was highest for Eucalyptus sieberi L. Johnson (1.9 mm) followed by Eucalyptus baxteri (Benth.) Maiden & Blakely ex J. Black (1.6 mm), and lowest for both Eucalyptus consideniana (Maiden) and Eucalyptus radiata (Sieber ex DC) combined (0.7 mm). Diameter growth increased with tree size for both E. sieberi and E. baxteri, but not for E. consideniana and E. radiata. Smaller trees were more likely to die due to shading and suppression than their larger counterparts. A mortality model suggested, however, that both shading and suppression had very little effect on trees in both E. consideniana and E. radiata species, which were less likely to die compared to trees in the other species. This result indicates that both E. consideniana and E. radiata species may be relatively shade tolerant compared with the other species. Total thinning response was a sum of positive (increased growing space) and negative (thinning stress) effects. Following thinning, smaller trees showed signs of thinning stress for the first one or two years, after which the highest percentage thinning response was observed. While larger trees were initially less responsive to thinning, the rate of decrease in the response for subsequent years was greater in smaller trees than larger ones. The average amount of thinning response showed similar trends to diameter growth increasing from E. sieberi (1.7 mm) through E. baxteri (0.6 mm) to both E. consideniana and E. radiata (0.5 mm). This translates into low average percentage thinning response in E. baxteri (34%), twice as much in both E. consideniana and E. radiata (69%) and highest overall percentage response in E. sieberi (87%). Thinning response and the duration of this response appeared to increase with thinning intensity and was still evident 29 years after thinning. Heavy thinning did, however, reduce the number of trees to a severely under-stocked condition, which prohibited optimum site occupancy, requiring 29 years of post-thinning development for the heavily thinned stands to regain their pre-thinning stand basal area.     

Relationships between morphological traits and resistance to pine wood nematode in two Japanese pines

It has been suggested that certain morphological traits of Japanese pines function as resistance factors against the pine wood nematode (PWN), Bursaphelenchus xylophilus. The aim of this study was to verify this concept, and to determine the relationships between traits and resistance at both the individual and family levels. Relationships between survival rate and morphological traits of Pinus densiflora and Pinus thunbergii were studied after inoculation with PWN. Morphometric parameters used were height, basal diameter of the axis, and the number of branches from the axis. Three indices of relationships were analysed: (1) among individuals within a family (survival difference between smaller and larger morphometric populations within each family); (2) among individuals (correlation between each morphometric average and survival rate in quintile populations of all subjects within each pine species based on the order of morphometric values); and (3) among families (correlation between each morphometric average and survival rate in the family). Both significant and non-significant differences were detected within a family, indicating a need for macro techniques. Among individuals, a thicker axis and more branches were correlated with increased survival, indicating that they are resistance factors. However, these correlations were not significant among different families. These results indicate that morphological traits cannot be used to evaluate resistance at a family level, even if they are significant at an individual level. Further studies on traits associated with resistance should be conducted at a family rather than an individual level, to breed for Japanese pines with resistance to PWN.

天然次生林直径分布的研究

该研究应用东北林区调查的119天然林标准地数据,通过绘制各林分直径分布直方图,分析林分的直径分布规律,运用SB分布、指数分布、正态分布、WeibuU分布和β分布函数对其进行拟合,建立直径回归模型,并采用矩解法求解参数,更精确地比较各种分布函数对实际数据的拟合效果.研究结果表明:林木株数随着直径的增大呈减少的趋势;指数分布和Weibull分布的拟合效果较好,但指数分布优于Weibull分布.观察指数分布函数的各参数的变化规律,发现参数a基本不变,而参数b在变化.绘制参数b与林分调查因子间的散点图,发现指数分布中的参数b与林分平均直径有显著的相关性.通过相关性分析,选择函数进行拟合,结果表明:幂函数的拟合效果最好,相关系数最高.通过对参数b的再参数化建立模型,最终得到最优的天然次生林林直径分布模型.