Riparian trees,shrubs, and forest regeneration in the coastal mountains of Oregon

Riparian trees and shrubs are important providers of shade, bank stability, and woody debris needed for optimal stream quality and fish habitat in the coastal mountains of Oregon, but more data are needed to relate this woody vegetation to environmental variables. Trees, shrubs, and forest regeneration were studied in 22 riparian environments to provide those data. Conifer basal area increased with elevation, stream gradient, time since disturbance, and distance from the stream; it decreased with stream width. Salmonberry (Rubus spectabilis Pursh) cover and stink currant (Ribes bracteosum Dougl. ex Hook.) cover were highest near the streams. Dwarf Oregon grape (Berberis nervosa Pursh) cover and salal (Gaultheria shallon Pursh) cover were lowest near the streams. Although forest regeneration was poor everywhere, it decreased with total shrub cover and increased with stream gradient. Existing riparian conifer stands should be maintained wherever a continuing supply of coarse woody debris is required.     

Nonisothermal moisture movement in wood

In order to analyze the effect of temperature gradient on moisture movement during highly intensive drying, such as microwave-vacuum drying, the profile of the temperature and moisture content in sealed wood whose opposite faces were subjected to temperature gradient for a short time was measured. The ratio of the moisture content (MC) gradient to the temperature gradient (dM/dT) was calculated and the factors influencing moisture movement under nonisothermal conditions were discussed. The results indicate that moisture moved in wood from the warm surface to the cold one even if opposite faces of the sealed wood assembly were exposed continuously to different but constant temperatures for a short period. The moisture content on the cold surface was higher than that on the warm surface. The moisture content gradient opposite to the temperature gradient was established, and the dM/dT was below 0.9%/°C. The temperature in the sample and the distance from the hot surface of the sample was strongly linearly correlated. With an increase in temperature, initial moisture content and experimental time, the dM/dT was significantly increased. __________ Translated from Journal of Beijing Forestry University, 2005, 27(2): 96–100 [译自: 北京林业大学学报, 2005, 27(2): 96–100]     

甜槠林群落结构及物种多样性特征研究

在分析不同海拔高度甜槠林群落结构及物种重要值特征的基础上,应用物种多样性的丰富度指数、多样性指数、均匀度等指标测定甜槠群落不同海拔梯度物种多样性,分析甜槠林物种多样性梯度变化效应。结果表明,甜槠群落物种多样性梯度变化规律明显;总体上物种多样性高,种类组成复杂,群落乔木层、灌木层、草本层层次明显。     

云南不同海拔小粒种咖啡生长发育情况调查

对云南思茅、保山、德宏、西双版纳4个地区的调查结果，小粒种咖啡在海拔900m以下的植株生长量和第3年的产量大于海拔1 100、1 300m植区的生长量和产量，但随海拔升高咖啡干豆千粒种增加，大象豆减少；随海拔升高，咖啡的果酸度增加，杯品品质提高。     

闽东高海拔山地地形因子对杉木人工林生长的影响

应用地形5个因子在2个水平下的正交试验设计方法,系统分析了闽东高海拔山地14年生杉木人工林生长的变化规律,结果表明:影响杉木人工林胸径、树高的各地形因子的重要程度依次为:坡形>坡位>坡向>海拔>坡度,影响杉木人工林冠幅的各地形因子的重要程度依次为:坡形>坡位>坡向>坡度>海拔,影响杉木人工林枝下高的各地形因子的重要程度依次为:坡形>坡位>海拔>坡向>坡度。坡形对杉木人工林胸径、树高和枝下高影响显著,坡位对杉木人工林树高影响显著。影响杉木人工林生长的最重要地形因子是坡形,其次是坡位,坡向、海拔和坡度(在45°以内)对杉木人工林生长影响不显著。     

黑龙江省东部山区森林植物多样性与环境梯度的相关性研究

为了探讨森林植物多样性与环境梯度的相关关系,本研究在黑龙江省帽儿山国家森林公园调查了23块不同结构的森林群落,每个群落布设的样方面积为400m2。森林植物多样性的计算采用Shannon-Wiener多样性指数,环境梯度的量化采用Whittaker的集合环境梯度计算方法,同时,采用相似性测度方法计算了Beta多样性指数。结果表明:Shannon-Wiener多样性指数随环境梯度的增大而增大,并且β多样性指数与环境梯度呈线性增加的趋势。图2表3参12。     

Woody vegetation structure and composition along a protection gradient in a miombo ecosystem of western Tanzania

Fully protected areas such as National Parks are often assumed to be the best way to conserve plant diversity and maintain intact forest composition and structure. To evaluate this assertion, we sampled trees in areas with four different levels of protection: a National Park, where the protection level is very high, a Game Controlled Area which allows tourist hunting of big game animals, a Forest Reserve which allows selective harvest of trees, and an Open Area where human populations have unrestricted access to forest resources. All four land management areas had healthy size-class distributions with greater numbers of juvenile trees (2–10 cm DBH) than adults. Surprisingly, mean stem density of trees was highest (947 stems ha⁻¹) in the Game Controlled Area but was lowest (635 stems ha⁻¹) in the National Park. The former had the highest basal area value (24 m² ha⁻¹) while the human-inhabited Open Area had the lowest (11 m² ha⁻¹). Species richness in the Forest Reserve and Game Controlled Area was significantly higher than in the other areas. The total number of plots with unique species not found anywhere else was lowest in the National. Our measures of forest structure and composition therefore show that fully protected National Parks do not necessarily conserve the greatest diversity of tree species or unique species, indicating that a suite of different types of protection strategies may be the key to conservation of trees in these African dry tropical forests.     

The importance of seedling competition in the segregation of spruce and fir in the southern Appalachians

Fraser fir (Abies fraseri [Pursh] Poir.) and red spruce (Picea rubens Sarg.) are codominants of southern Appalachian spruce-fir forests. Fraser fir generally dominates above 1740 m, while red spruce usually dominates below this elevation. This study was designed to determine whether the present segregation of the two species along elevational gradients is associated with seedling competition or contrasting physiological responses to environmental factors. Seedlings were grown for two years in a replacement series experiment along two elevational transects extending from 1300 m to 1900 m, and harvested for growth analysis.Competition increased with decreasing elevation and Fraser fir was apparently the stronger competitor. Mortality was inversely correlated with elevation and was most evident in red spruce in May, and in fir in late summer. Fir growth increased with elevation and red spruce grew most at the middle elevation (1600 m). Neither competitive interactions nor growth responses completely explained the elevational segregation of red spruce and Fraser fir. We hypothesize that the early-successional Fraser fir quickly dominates at higher elevations following disturbance and that continued disturbance will favor its dominance at higher elevations. However, the late-successional noncompetitive red spruce slowly establishes itself and, while consistently present, may only dominate in the absence of disturbance and where other species are at the margins of their distribution.     

Comparison of moisture distribution along radial direction in a log cross section of heartwood and mixed sapwood and heartwood during radio-frequency/vacuum drying

The purpose of this study was to compare the distribution of moisture contents (MCs) along the radial direction during radio-frequency/vacuum (RF/V) drying of log cross sections of heartwood (HLC) where sapwood was removed from a green log cross section and log cross section of mixed sapwood and heartwood (MLC) prepared with debarked logs of Japanese larch (Larix leptolepis) and locust (Robinia pseudoacacia). For Japanese larch, an even distribution of MC was observed over the entire cross section in HLC not only at the initial stage of drying but also up to the completion of drying. Furthermore, the moisture gradient between the outermost slice and the adjacent inner slice was more gradual compared with that in MLC. For locust, the moisture gradient between the outermost slice and the adjacent inner slice became severe as drying progressed. It decreased after reaching the maximum during the middle stage of drying but continued until the late stage of drying. Furthermore, despite the fact that the average initial MC of mixed slice within MLC was higher compared with that in heartwood slice, this trend reversed immediately after drying started. It was suggested that the possibility of formation of border checking would be high during drying the MLC, since it would be so complicate that the sapwood and heartwood reach fiber saturation point together because of differences in their green MCs and permeability between them.     

祁连山不同海拔梯度青海云杉树高和生物量变化规律的研究

通过野外样地调查和试验,以祁连山典型林分的建群树种青海云杉作为研究对象,研究了青海云杉树高、地上生物量和地下生物量沿海拔梯度的变化规律。结果表明:海拔从低到高,青海云杉树高总体上呈单峰型曲线变化,但总体变化幅度较小,最大值分布在海拔3 200m处,为12.4m;最小值分布在海拔3 300m处,其值为7.3m。地上生物量和地下生物量海拔梯度总体上呈单峰型曲线变化,最大值出现在海拔3 200 m处,分别为3.34t·hm-2和0.92t·hm-2。