我国南方湿地松木材物理力学性质变异初探

我国南方五省区湿地松木材的密度、晚材率和各项力学强度,随纬度的增加,呈递减状态。纬度与气干容重之间的直线回归方程为:G=1.28—0.027L,相关系数r=0.984.产生此现象的主要原因是,木材的管胞宽度和厚度随着纬度的增加逐渐变窄、变薄。产地的年平均气温和年降水量对湿地松树木的年轮宽度和晚材带宽度影响较大;年轮和晚材带的平均宽度随产地自北向南依次增加,随着山地海拔的升高而减小。     

南带产区杉木正常木与被压木的比较解剖研究

为了解杉木正常木与被压木木材解剖上的差异,采用宏观、微观的方法,以广西国营高峰林场12～13年生的杉木木材为试验材料,于2001～2003年研究了南带产区杉木正常木与被压木木材解剖特征.结果表明,正常木与被压木的生长轮宽度径向变异规律相似,均为随着树龄的增加呈先增加后减小的趋势,纵向变异规律相似,均随着树高的增加呈先增加后减小的趋势.正常木的年轮宽度大于被压木.正常木与被压木的晚材率径向变异规律相似,均随着树龄的增加而基本保持不变,纵向变异规律相似,均为随着树高的增加而基本保持不变.正常木与被压木管胞长度     

气候因子对新疆雪岭云杉树轮最大晚材密度的影响

Isl＞2.5,1953～2008年)或连续2～3年干旱指数绝对值接近1.5σ时,水分条件将会对MXD产生影响.这一气候响应特征与研究区半干旱气候有关,在干早年份,水分匮缺会限制晚材细胞壁的加厚,从而影响MXD.因此,与相对湿润地区相比,半干旱地区树轮MXD对气温响应的同时也会受到极端降水状况的影响,作为气温代用指标需谨慎而有限度的使用.     

祁连山青海云杉径向生长对气候的响应

为探明树木径向生长对气候变化的响应,以祁连山中部下限青海云杉为研究对象,采用年表气候相关分析和特征年分析方法,研究了青海云杉的年轮宽度、早材宽度、晚材宽度标准化年表与月均温度和降雨量的关系。结果表明:年轮宽度、早材宽度、晚材宽度与6、7月的月均温度显著负相关。年轮宽度、早材宽度与3、5、6月的降雨量显著正相关,与9月的降雨量显著负相关;晚材宽度与降雨量无显著相关,晚材宽度对气候的敏感性弱于早材宽度。特征年分析进一步发现:当夏季温度高于同期温度而夏季降雨量又低于同期降雨量时,容易形成窄年轮;相反,当夏季温度低于同期温度而夏季降雨量又高于同期降雨量时,容易形成宽年轮。表明春季和夏季降雨量对祁连山中部下限青海云杉的径向生长有促进作用,而夏季温度有抑制作用。      

云杉属木材晚材率变异系数与声振动特性参数

选择了8种主要云杉属树种木材,进行了弯曲振动条件下各项声振动特性参数的检测和比较,初步分析了振动特性参数与木材构造中晚材率变异系数之间的关系,探索了晚材率变异系数对乐器用材质量的影响,为深入评价云杉属乐器用材品质奠定了基础.     

板栗年轮结构对北京地区气候因子的响应分析

以北京地区板栗为材料,建立板栗年轮宽度、早材宽度和晚材宽度3项年轮结构指标的标准化年表和差值年表,分析板栗径向生长与气候因子间的相关关系和响应,并对可重建的气候因子进行筛选。结果表明：板栗年轮宽度和晚材宽度的年表质量明显好于早材宽度年表,其中差值年表优于标准化年表,其样本总体代表性达到93%,第1主成分方差解释量达到40%。差值年表与气候因子的相关分析和响应分析结果表明：年轮宽度、早材宽度和晚材宽度与各项气候因子间响应关系不同,在将来重建过去气候时,可利用年轮宽度和晚材宽度重建当年6月的温度,晚材宽度还可以重建当年7月的降水,早材宽度重建当年3月和4月的温度。     

Response to climate changes in radial growth of Picea crassifolia in the Qilian mountains of northwestern China

In order to investigate the response to climate changes in radial growth of Picea crassifolia at the lower tree line in the middle Qilian mountains in northwestern China, relationships of standardized chronologies of annua ring, earlywood and latewood widths with mean monthly temperature and total monthly precipitation were analyzed by ways of correlation and pointer year analyses. The results show that annual ring, earlywood and latewood widths are significantly negatively correlated with mean monthly temperature in June and Juy. Annual ring and eadywooc widths are significantly and positively correlated with tOtal monthly precipitation in March, May and June and negatively correlated with total monthly precipitation in September. Latewood width is less sensitive to climate changes than the width of earlywood and insignificantly sensitive to precipitation. The results of pointer year analysis revealed that whet summer temperatures are higher than the mean summer temperature synchronization and the summer precipitatior lower than mean summer precipitation synchronization, narrow annual rings are formed. Wide annual rings are formec~ when summer temperatures are lower than the mean summer temperature synchronization and summer precipitation higher than mean summer precipitation synchronization. The results indicate that more precipitation in the spring and summer is helpful for radial growth while warmer summer restricts radial growth of P. crassifolia at the lower tree line in the middle Qilian mountains.     

Dependence of shear strength on wood properties in cultivated Larix sibirica

Abstract

Mechanical properties are very important in structural uses of wood. In the case of larch wood, shear strength (SS) may be a limiting property, because the wood is brittle and it splinters easily. In this study, SS of Siberian larch (Larix sibirica) wood was studied in relation to its axial and radial location and to some other wood properties in the part of the trunk that produces logs of good carpentry quality. SS increased by 21–23% from the pith to the outer heartwood at each studied height (butt, 4.5 and 9 m), and it was at its most approximately 7% higher at the butt than at the other studied heights. The main reason for the radial increase in SS was the increase in density caused by wood maturation, but other factors also affected SS, depending on the grouping mode (combined material, radial/axial location). An exception was sapwood, for which no factors affecting SS could be identified. Thus, sapwood may behave differently from heartwood regarding use, even unexpectedly. The results suggest that mature heartwood, but not juvenile wood and sapwood, of Larix sibirica should primarily be used in products that require high SS.     

Ecological and climatological signals in tree-ring width and density chronologies along a latitudinal boreal transect

Shifts in the climate sensitivity of trees throughout the twentieth century might indicate climate change effects in the boreal forest ecosystem. We here evaluated such potential changes by analyzing six tree-ring width (TRW) and maximum latewood density (MXD) chronologies from northern, central and southern boreal forests in Finland (60°N–69°N). Besides latitudinal effects, differing micro-sites (lakeshore and inland) were considered to evaluate the influence of ground water access on twentieth-century tree-ring formation and climate sensitivity. Overall, the boreal MXD chronologies appeared less affected by micro-site conditions compared to the TRW chronologies. Along the boreal transect, mean growth rates decrease with increasing latitude, but the ratio of earlywood-to-latewood (～70%/～30%) remains stable. However, latewood is slightly denser at the dry inland micro-sites. The correlations with climate data showed that TRW and MXD at all sites are positively related with summer temperature. The MXD chronologies are also negatively correlated with precipitation, a feature that is largely missing in TRW. A recent trend toward wetter and cloudier conditions in the study region coincides with a shift of the MXD signal from a distinct temperature limitation toward an additional sensitivity to precipitation, which in turn stimulated the trees’ competition for sunlight.     

Variation in the incidence and severity of drought crack in three conifer species in North East Scotland

The incidence of longitudinal drought cracks in coniferous trees may increase as a consequence of climate change. While larger diameter trees are more prone to splitting, it is unclear why only some of the larger trees within the same stand typically suffer damage. Matched pairs of trees of the same size with and without cracks were studied in two adjacent pole-stage mixed stands of Sitka spruce/grand fir (Picea sitchensis/Abies grandis) and Sitka spruce/noble fir (Picea sitchensis/Abies procera) located in North-East Scotland. A range of attributes were measured on 15 damaged and undamaged trees of each species. Length and position of cracks on stems were also recorded, and annual ring width and latewood percentage measured on cores. Noble fir had significantly longer cracks and these were located higher in the stem than the other species. Fewer cracks formed on east-facing side of stems in all species suggesting that prevailing westerly winds may place greater tensile forces on the damaged sides of stems. A higher proportion of latewood (associated with higher tangential shrinkage) was found in the firs and may explain the greater incidence of cracking on grand and noble fir stems (13% and 16%, respectively) in comparison with Sitka spruce (3%).