Cut logs and high stumps of spruce, birch, aspen and oak - nine years of saproxylic fungi succession

Managed stands generally contain little coarse woody debris compared to natural forests. This study addresses the potential of retained cut wood to increase the amount of substrate available for a variety of saproxylic fungi.Fruit bodies of fungi were recorded from 270 cut high stumps and logs of spruce, birch, aspen and oak over nine years of initial succession. A total of 1565 occurrences of 148 species, seven of which were red-listed, were found. Numbers of species were significantly higher on logs than on stumps. Annual diversity peaked four to seven years after logging, sooner on logs than on stumps. Numbers of species were positively related to substrate diameter, but not to the level of shade/sun-exposure, while the presence of some individual species were significantly affected by one or both of these factors. Comparisons with data from the literature indicated no fundamental differences between fungal communities on cut wood and on naturally dead substrates. We conclude that cut wood left on site, especially logs, may mimic dead wood from trees that die swiftly from natural causes and support diverse fungal communities, both in shaded stands and in open logging sites. Substrates generated by slow self-thinning processes in natural forests however, are probably difficult to mimic in managed stands.     

Relationships of dead wood patterns with biophysical characteristics and ownership according to scale in Coastal Oregon,USA

Dead wood patterns and dynamics vary with biophysical factors, disturbance history, ownership, and management practices; the relative importance of these factors is poorly understood, especially at landscape to regional scales. This study examined current dead wood amounts in the Coastal Province of Oregon, USA, at multiple spatial scales. Objectives were to: (1) describe current regional amounts of several characteristics of dead wood; (2) compare dead wood amounts across ownerships; (3) determine the relative importance, according to spatial scale, of biophysical and ownership characteristics, to regional dead wood abundance. Dead wood plot data were evaluated with respect to explanatory variables at four spatial scales of resolution: plots, subwatersheds, watersheds and subbasins. The relationships of dead wood characteristics with biophysical attributes and ownership were diverse and scale-specific. Region-wide dead wood abundance and types varied among ownerships, with public lands typically having higher amounts of dead wood and more large dead wood than private lands. Regression analysis of total dead wood volume indicated that ownership was important at the subbasin scale. Growing season moisture stress was important at plot, subwatershed, and watershed scales. Topography was important at the two coarser scales. Multivariate analysis of dead wood gradients showed that ownership was important at all scales, topography at the subbasin scale, historical vegetation at watershed and subbasin scales, and current vegetation at plot and subwatershed scales. Management for dead wood and related biodiversity at watershed to landscape scales should consider the distinct dynamics of snags and logs, the importance of historical effects, and the relevance of ownership patterns.     

Dynamics of large woody debris in small streams disturbed by the 2001 Dogrib fire in the Alberta foothills

We investigated the temporal dynamics of large woody debris (LWD) in five headwater streams before and after the 2001 Dogrib fire in the foothills of Alberta. The density of LWD varied from 5 to 41 logs per 50 m of stream reach and accounted for 19.4 ± 5.1 m³ ha⁻¹ (mean ± standard error) of wood in the riparian zones and 114.1 ± 30.1 m³ ha⁻¹ of wood in the bankfull margins of the stream channel. Individual logs averaged 18.9 ± 1.15 cm in diameter, 5.5 ± 0.7 m in length, and 0.2 ± 0.02 m³ in volume. Logs became significantly shorter in decay classes II–IV. Bridges were longer than partial bridges, which were longer than loose and buried LWD. Individual log volume was greatest for bridges, but not significantly different among other position classes. Bridges and loose LWD contributed little to stream morphology and function; however, 55% of partial bridges and all buried logs contributed to sediment storage, channel armouring, or riffles and pools in the stream channel.     

原木到材方式集约化经营的研究

本文系统分析了当前伐区原木生产的现状，并结合国情，科学地论述了原木到材方式集约化经营的设想，并建立了适用的集约化经营的数学模型，以及实现设想的措施，对林业企业的伐区生产尽快地由粗放的经营方式向集约化经营方式的转换将会起到推进作用。     

Biased estimation of forest log characteristics using intersect diameters

Logs are an important structural feature of forest ecosystems, and their abundance affects many resources and forest processes, including fire regimes, soil productivity, silviculture, carbon cycling, and wildlife habitat. Consequently, logs are often sampled to estimate their frequency, percent cover, volume, and weight. The line-intersect method (LIM) is one of the most widely used methods to obtain these estimates and has been shown to produce unbiased estimates of log characteristics. With the traditional LIM the diameters of each log at the point of its intersection with the sampling transect are used to estimate log characteristics. Based on a simulation study and a large set of empirical data, we found that use of intersect log diameters to define size classes provided biased estimates of log characteristics. The bias varied by diameter class. Results from the simulation study showed that log frequency and volume were overestimated in small-diameter log classes and underestimated in large-diameter classes. Similarly, results from our empirical analysis showed a 40% overestimate of log volume in the smallest diameter class (15–25 cm), and a 31% underestimate of volume in the largest diameter class (>50 cm). Just as size classes of snags and trees are best defined by their diameter-at-breast height (DBH), size classes of logs should be defined by their large-end diameters (LEDs). When large-end diameters of logs were used instead of diameters measured at the point of transect intersection, bias was substantially reduced or eliminated. These results indicate that line-intersect sampling could be substantially improved by including measurements of LEDs to estimate log characteristics. Our results have far-reaching implications for estimates of log characteristics, such as estimates of fuel loading and subsequent wildfire risk, carbon source and sink dynamics, silviculture, nutrient cycling, and habitat for wildlife. Without our suggested correction to line-intersect sampling, many forest resources associated with log characteristics will not be estimated accurately, affecting a plethora of log-based management and research programs.     

Model study of log feeding technology at the dam of Ertan Hydropower Station in China

IntroductionErtanhydropowerstationissituatedinSichuanProvince.Itis3okmfromtheexitofY8longRiver.ltisabigkeyprojectforwatercontrol.ItsmainpurposeistogenerateeIectricityandcrossingthefloatedlogsoverdammustbedealtwithaswell.Theheightofdamis24om.Itconsistsoffoursystems(dam,flood-dischargetunneI,workshopsystem,andIogpassingtunnel).TheeIectricitygenerationcapacityis3.3miIlionkw.Theelectricenergyproductionis17biIlionkiIowattsayear.Thereservoircapacityis5.8'billionm3.ThenormalwaterIeveIis12oOmi…     

原木评等中漏节计算问题的探讨

本探讨了现行原木缺陷标准中对漏节的检算方法，认为统计漏节个数时不应把漏节数目相加。且漏节尺寸与树干内腐不成正比。     

小径原木干燥工艺初探

本文是在桦木（Ｂｅｔｕｌａｐｌａｔｙｐｈｙｌｌａ）、刺槐（Ｒｏｂｉｎｉａｐｓｅｕｄｏａｃａｃｉａ）与水曲柳（Ｆｒａｘｉ－ｎｕｓｍａｎｄｓｈｕｒｉｃａ）等小径原木干燥可行性分析与干燥特性研究等工作的基础上，总结出了小径原木的干燥工艺过程。生产实践证明，该工艺过程对小径原木的干燥是可行的。     

原木形状识别系统设计

基于原木识别系统的设计原理,以原木沿纵向形状的椭圆形曲线为主,分析了原木的尺寸,以便识别原木的形状,计算原木的材积.原木识别系统采用8个传感器对原木进行8点采样,实测各点的数据,并通过计算机模拟再现原木外形,经过运算分析得出原木端面径级等几何形状参数,并由数据库统一存储和管理每根原木的参数信息.同时对电路系统进行了设计,实现设备与识别系统的接口.原木形状检测装置--WQK3102原木形状识别系统经实际应用表明,可以满足原木形状识别功能的要求.