木质材料阻燃技术研究现状与趋势

近年来, 木质材料阻燃新技术不断涌现。文中在分析了大量文献的基础上, 比较详细地综述了木材阻燃剂的作用和主要的阻燃机理, 简述了我国学者在应用上所取得的主要成果和国外畅销的阻燃剂种类, 并提出了今后的研究方向。     

A comparative assessment on regeneration status of indigenous woody plants in Eucalyptus grandis plantation and adjacent natural forest

Diversity, density and species composition of naturally regenerated woody plants under Eucalyptus grandis plantation and the adjacent natural forest were investigated and compared. Twenty plots, with an area of 20 m × 20 m for each, were established in both of E. grandis plantation and adjacent natural forest, independently. In each plot, species name, abundance, diameter and height were recorded. Numbers of seedling were collected in five sub-plots (4 m²) within each major plot. A total of 46 species in the plantation, and 52 species in the natural forest, which belongs to 36 families were recorded. The diversity of species (H′) is 2.19 in the plantation and 2.74 in the natural forest. The density of understory woody plant was 3842 stems/ha in the plantation and 4122 stems/ha in the natural forest. The densities of seedlings in the natural forest and the plantation were 8101 stems/ha and 4151 stems/ha, respectively. High similarity of woody species composition was found between the natural forest and the plantation. The E. grandis plantation was found favoring the regeneration and growth of Millitia ferruginia and Coffea arabica in a much better way than other underneath woody species.     

Spatial patterns of litter-dwelling taxa in relation to the amounts of coarse woody debris in European temperate deciduous forests

We studied the leaf litter-dwelling fauna of managed deciduous forests and primeval reference sites in Western and Central Europe and addressed the questions if the higher overall species richness close to downed coarse woody debris (CWD) is related to intra-specific or inter-specific aggregation, if the aggregation pattern changes with the amount of CWD on the forest floor, and how much CWD is needed for different taxa. The analysis is based on shelled Gastropoda, Diplopoda/Isopoda, Chilopoda and Coleoptera. Among-sample heterogeneity was lower close to CWD than distant from CWD. This was most pronounced in Diplopoda/Isopoda and Gastropoda. Diplopoda/Isopoda are comparatively mobile and assemblages were already quite homogenous close to CWD at levels above 5 m³ downed deadwood ha⁻¹. Gastropoda have a low mobility, and more than 20 m³ downed deadwood ha⁻¹ is needed for assemblage homogeneity. We further focused on the Gastropoda as sensitive indicators. Enhanced densities and species richness close to CWD were not a simple function of leaf litter weight, thus effects of densities on heterogeneity are not solely driven by leaf litter accumulation close to CWD. In contrast to euryecious litter-dwellers such as the Punctidae, stenecious slow active dispersers such as the Clausiliidae clearly require more than 20 m³ CWD ha⁻¹ for an even distribution. Specialists depending on CWD even seem to have gone extinct in some managed forests. For conserving the litter-dwelling fauna, we propose a target of at least 20 m³ downed CWD ha⁻¹ in already managed forests and rigorous restrictions for deadwood removal from still (almost) pristine systems.     

Factors influencing the formation of unburned forest islands within the perimeter of a large forest fire

Large forest fires have recently increased in frequency and severity in many ecosystems. Due to the heterogeneity in fuels, weather and topography, these large fires tend to form unburned islands of vegetation. This study focuses on a large forest fire that occurred in north-eastern Spain in 1998, which left large areas of unburned vegetation within its perimeter. Based on a satellite post-fire severity map we searched for the relative influence of biotic and abiotic factors leading to unburned island formation. We divided the area of the fire into individual units we called “slopes” which were meant to separate the differential microclimatic effects of contrasted aspects. The number of unburned islands and their areas were related to 12 variables that influence their formation (i.e. land cover composition, aspect, steepness, forest structure, two landscape indices and weather variables). We hypothesized that unburned vegetation islands would concentrate on northern aspects, in less flammable forests (i.e. broadleaf species) and higher fragmentation to interrupt the advance of fire. While north and western aspects did have a higher presence of unburned vegetation islands, our study suggests greater presence of islands in slopes that are larger (i.e. more continuous areas with relatively homogeneous aspect), with greater proportions of forest cover, with higher wood volumes and with lower proportions of broadleaf species. Climate also played a role, with relative humidity and wind speed positively and negatively correlated to island formation, respectively. Unburned vegetation was more frequent on slopes with lower diversity of land covers and higher dominance of one land cover in the slope. Since slopes with only one land cover (i.e. forests) had more islands than slopes with multiple cover types, we infer that under severe meteorological conditions, fragmented forests can be more affected by wind and by water stress, thus burning more readily than forests that are protected from this edge phenomenon. These results would reinforce forest management strategies that avoid linear features (fire-lines and fire-breaks), to enhance fuel treatments that focus on areas and minimize fragmentation.     

Decomposition of stumps in a chronosequence after clear-felling vs. clear-felling with prescribed burning in a southern boreal forest in Finland

The wood bulk density, bark mass and decomposition rate constants of cut stumps of the main European boreal tree species were assessed along a 40-year chronosequence of clear-felled sites with and without prescribed burning. Using the single exponential model, the annual decomposition rate constants k of above-ground stumps were calculated as 0.048, 0.052 and 0.068 year⁻¹ for Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula sp.), respectively. Bark decomposed faster than wood and bark fragmentation increased the rate of decomposition. There was a significant negative effect of burning on decomposition rate for pine wood, and for pine and spruce bark but not for spruce and birch wood or for birch bark. The decomposition of bark of all species was slower with larger diameter stumps but only slightly slower in the case of birch wood. Our results suggest (i) using different decomposition rate constants for wood and bark, (ii) taking into account fragmentation as it greatly increases the volume loss, and (iii) adjusting of k in carbon dynamics studies on burned sites. Such refinements to estimates of coarse woody debris decomposition constants could aid in identification of ecosystems and management scenarios necessary to maximize carbon storage and conserve biodiversity. Prescribed burning for restoration purposes decreases decomposition rates and consequently ensures longer persistence of stumps for maintaining biodiversity in intensively managed forests.     

木材的全木利用模式及经济学分析

随着生态恶化和能源危机的不断加剧,木质生物质能源的开发和利用逐渐受到人们的青睐.针对我国木材利用现状,提出了全木利用的概念和2套模式,并对全木利用模式的实施进行了必要性论证和可行性分析,着重阐述了木材的生态循环利用措施.     

我国木质林产品贸易与森林生态安全耦合度研究

“两头在外”是我国林产品贸易的典型特征, 它意味着对国内和国外森林资源的大量消耗。木质林产品贸易和森林生态安全的协调是开放条件下实现我国森林可持续发展的必经之路。文中运用耦合理论研究1961-2010年我国木质林产品贸易和森林生态安全之间的协调问题, 结论认为:1)2004之前森林生态安全指数高于木质林产品贸易指数, 2005-2008年则低于木质林产品贸易指数, 1991年之后木质林产品贸易指数的波动幅度显著大于森林生态安全指数。2)1961-1999年森林生态安全指数与木质林产品贸易指数的协调状态在初级协调和勉强协调之间波动; 2000年之后二者的协调进入稳定阶段, 并在2003年由初级协调进入中级协调阶段。     

森林粗木质物残体贮量及功能研究综述

粗木质物残体(CWD)在森林生态系统能量流动、物质循环以及维护森林生态系统的完整性和稳定性方面发挥着重要作用, 科学有效地对其贮量进行定量化研究, 对进一步了解CWD在生物地球化学循环过程中和全球碳循环与碳平衡中的地位与作用具有重要意义。文中论述了CWD的贮量、CWD的分解、CWD在碳贮量与碳循环中的重要作用以及影响CWD贮量和分解的原因, 系统阐明了CWD在促进森林生产力、维持生物多样性以及促成森林更新等方面的功能, 展望了CWD贮量定量化研究以及结构与功能研究的发展方向。     

Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an alfisol

Field trials were carried out on an Oxic Paleustalf in the humid zone of southwestern Nigeria withLeucaena leucocephala (Lam.) de Wit,Gliricidia sepium (Jacq.) Steud. andSesbania grandiflora (L.) Pers. alley cropped with maize and cowpea. The three leguminous woody species were grown in hedgerows spaced at 2 m. Trials were carried out one year after establishment of the hedgerows using a split-plot design with four replications. TheLeucaena trial had twenty pruning combinations consisting of five pruning heights (25, 50, 75, 100 and 150 cm) and four pruning frequencies (monthly, bi-, tri- and six-monthly). TheGliricidia andSesbania hedgerows were subjected to nine pruning intensities consisting of three pruning heights (25, 50 and 100 cm) and three pruning intensities (monthly, tri- and six-monthly).For the three woody species, biomass, dry wood and nitrogen yield from the hedgerow prunings increased with decreasing pruning frequency and increasing pruning height. Biomass, dry wood and nitrogen yields were in the following orderLeucaena >Gliricidia >Sesbania.The various pruning intensities had no effect on survival ofLeucaena plants. Pruning frequency had a larger effect than pruning height on survival ofGliricidia andSesbania plants. With monthly pruning, about 25 percent of theGliricidia and all of theSesbania plants died within six months of repeated pruning. Even with lower pruning frequencySesbania plants showed lower survival rates thanGliricidia orLeucaena.The various pruning intensities of all the hedgerow species had more pronounced effects on the grain yield of the alley cropped cowpea than on maize grain yield. Higher maize and cowpea yields were obtained with increasing pruning frequency and decreasing pruning height.IITA Journal paper number 335     

Effect of pruning intensities of three woody leguminous species grown in alley cropping with maize and cowpea on an alfisol

Field trials were carried out on an Oxic Paleustalf in the humid zone of southwestern Nigeria withLeucaena leucocephala (Lam.) de Wit,Gliricidia sepium (Jacq.) Steud. andSesbania grandiflora (L.) Pers. alley cropped with maize and cowpea. The three leguminous woody species were grown in hedgerows spaced at 2 m. Trials were carried out one year after establishment of the hedgerows using a split-plot design with four replications. TheLeucaena trial had twenty pruning combinations consisting of five pruning heights (25, 50, 75, 100 and 150 cm) and four pruning frequencies (monthly, bi-, tri- and six-monthly). TheGliricidia andSesbania hedgerows were subjected to nine pruning intensities consisting of three pruning heights (25, 50 and 100 cm) and three pruning intensities (monthly, tri- and six-monthly). For the three woody species, biomass, dry wood and nitrogen yield from the hedgerow prunings increased with decreasing pruning frequency and increasing pruning height. Biomass, dry wood and nitrogen yields were in the following orderLeucaena >Gliricidia >Sesbania. The various pruning intensities had no effect on survival ofLeucaena plants. Pruning frequency had a larger effect than pruning height on survival ofGliricidia andSesbania plants. With monthly pruning, about 25 percent of theGliricidia and all of theSesbania plants died within six months of repeated pruning. Even with lower pruning frequencySesbania plants showed lower survival rates thanGliricidia orLeucaena. The various pruning intensities of all the hedgerow species had more pronounced effects on the grain yield of the alley cropped cowpea than on maize grain yield. Higher maize and cowpea yields were obtained with increasing pruning frequency and decreasing pruning height. IITA Journal paper number 335