Neutron imaging versus standard X-ray densitometry as method to measure tree-ring wood density

Neutron imaging is a new non-destructive testing method in wood science. It is similar to X-ray methods but with differing sensitivities for different elements. In this study, neutron imaging was used to ascertain the density profiles of thin spruce samples and compared with results generated with standard X-ray microdensitometry. Data obtained through neutron imaging were similar to those resulting from the X-ray method. The advantage of neutron imaging is its higher sensitivity to some elements such as hydrogen. Together with the high neutron-sensitivity of the applied detectors (imaging plates) this makes shorter exposure times possible, and yields more detailed information on the inner composition of wood. X-ray film, which is still most commonly used in X-ray densitometry, has the disadvantage that the relationship between the optical density of the film and the density of wood is non-linear. This means that corrections and calibration with step wedges are necessary, whereas with neutron imaging the digital values can be used directly to calculate the density at a certain point of the specimen. Thus neutron imaging appears to be an appropriate method, which can be used as complement to established X-ray methods for fast and straightforward investigations of tree rings, growth zones and wood density.     

xRing—An R package to identify and measure tree-ring features using X-ray microdensity profiles

Climate influences tree-ring density and ring-density variables extracted from X-ray images have been widely used for climate reconstructions. The R package xRing was developed to identify and measure tree rings on X-ray microdensity profiles automatically. This package is available for free and it offers functions to visualize and calibrate X-ray images, to detect tree-ring borders and to identify earlywood-latewood transition using wood density variations at the inter- and the intra-ring scale. The most important functions are calibrateFilm, detectRings, correctRings, detectEwLw, and getDensity. Outputs of these functions are S3 objects, for which specific methods are provided, including plot and print. The non-linear relationship between optical density of the film and wood density is defined by the function calibrateFilm. The function detectRings detects tree rings using wood density profiles as input. This function uses the difference between local maximum and minimum values to identify tree-ring borders automatically. The correctRings function is used to call a Graphical User Interface (GUI) to visualize and to correct tree-ring borders manually. After correcting tree-ring borders, the detectEwLw function is used to compute earlywood and latewood widths by dividing rings according to relative intra-ring density changes. The getDensity function computes for each tree ring the minimum (maximum) density and the mean earlywood, latewood and whole-ring density. Finally, a list with dataframes with tree-ring width and density variables can be obtained using the function getRwls. One of the major advantages of xRing package is that requires little knowledge of R language, but at the same time it can be easily changed or adapted by experienced users.     

What tree rings can tell us about the competition between trees and lianas? A case study based on growth,anatomy, density,and carbon accumulation

In tropical forest, landscape fragmentation and the consequent degradation of disturbed forests increase the incidence of light and dry hot winds, causing a disturbance on natural regeneration. Under these conditions, lianas (woody vines) development is stimulated instead of other species, which are more suited to mature forest and under less influence of the edge effect. For this, lianas colonization is an important variable for assessing the disturbance level of a forest. In this context, it becomes important to understand the nature of the competitive relationships between hyper-abundant lianas and ring growth of the host trees. Here, we selected trees with occupation or absence of lianas from two tropical species – Pinus caribaea var. hondurensis (Caribbean pine) and Tectona grandis (teak) – localized in a semideciduous forest fragment in southeastern Brazil, aiming to compare growth, climatic response, anatomy (vessels and intra-annual density fluctuations), wood density and carbon, by tree-ring analysis. The results showed that the lianas caused a change in tree-ring anatomy of host trees in last 10 years, mainly. We observed that trees occupied by lianas had a decrease the radial growth and carbon in the two species, an increase of the vessels size in teak and a decrease of the IADF frequency in Caribbean pine. In teak, the climate-tree relationship indicated that trees with lianas had lower response to rainfall and higher response to temperature in the summer (rainy and hottest period); in Caribbean pine, we observed that trees with lianas had a 2-month delay in the radial growth response to rainfall in the dry season. In the teak group, we observed that host trees had higher wood density values than liana-free tree in the outer rings, and the opposite was showed for pine. These findings show that tree-ring growth of host trees are a strong bioindicator of forest disturbance caused by aggressive colonization of lianas. We believe that these methods are applicable to future studies relating to the effects of habitat fragmentation and forest degradation on biodiversity and ecosystem services, particularly in the context of global climate change.     

海桑属(Sonneratia)植物的木材结构及其系统演化意义

研究了海桑科海桑属(Sonnerotia)6种植物的木材结构特征,并与同科的八宝树属(Duabanga)、千屈菜科的紫薇属(Lagerstroemia)植物的木材结构进行比较。结果表明：1.射线高度和射线宽度可作为卵叶海桑区别于其它种类的鉴定特征或辅助特征;2．海桑属形成一单系的类群,并与紫薇属有更近的亲缘关系,而与同科的八宝树属的亲缘关系更远;3．导管数量特征的聚类分析可以推测海桑属植物沿两支进化,一支进化为水分输导效率高的种类(即导管直径宽和输导面积大,管孔密度小,如海桑和拟海桑),另一支进化为水分输导安全性高的种类(即导管直径窄、输导面积小,管孔密度大,如杯萼海桑、卵叶海桑、无瓣海桑、海南海桑)。     

Relationship between wood anatomy,tree-ring widths and wood density of Pinus sylvestris L. and climate at high latitudes in northern Sweden

In this study, wood anatomy, tree-ring width and wood density of Pinus sylvestris at the northern timberline in Fennoscandia were used to identify relationships among the parameters and to screen them for their climatic signals. Furthermore we investigated the influence of the juvenile wood section for all parameters developed. The measurements of wood anatomy were conducted with confocal laser scanning microscopy (CLSM) while the density profiles were produced using an Itrax MultiScanner. We developed chronologies of ring width, wood density and anatomy for a period between 1940 and 2010. Correlations between wood density and wood anatomy were strong in the latewood part. For some wood anatomy and density chronologies youth trends were found in the juvenile part. Wood density decreased from the pith up to the 9th ring and stabilized afterwards, while cell lumen diameter and lumen area increased simultaneously up to the 15th ring. All chronologies contained strong summer temperature signals. The wood anatomical variables provided additional information about seasonal precipitation which could not be found in wood density and tree-ring widths. Our study confirmed previous results stating that the parameter maximum density contains the strongest climate signal, that is, summer temperatures at the northern timberline. Nevertheless, the intra-annual data on tracheid dimensions showed good potential to supply seasonal climatic information and improve our understanding of climatic effects on tree growth and wood formation.     

X-ray microdensitometry applied to subfossil tree-rings: growth characteristics of ancient pines from the southern boreal forest zone in Finland at intra-annual to centennial time-scales

A collection of subfossil wood of Pinus sylvestris (Scots pine) was exposed to X-ray densitometry. The collection of 64 samples from the southern boreal forest zone was dendrochronologically cross-dated to a.d. 673-1788. Growth characteristics were determined by performing density profiles including the following parameters: minimum density, earlywood and latewood boundary density, maximum density, earlywood width, earlywood density, latewood width, latewood density, annual ring width and annual ring density. Seven out of the nine parameters were found to contain non-climatic growth trends and six were found to be heteroscedastic in their variance. Tree-specific records were indexed, to remove the non-climatic growth trends and stabilize the variance, and combined into nine parameter-specific tree-ring chronologies. Growth characteristics of the pines changed in parallel with the generally agreed climatic cooling from the Medieval Warm Period to the Little Ice Age: pine tree-rings showed decreasing maximum densities from the period a.d. 975-1150 to a.d. 1450–1625. A concomitant change in the intra-annual growth characteristics was detected between these periods. The findings indicate that not only the trees growing near the species’ distributional limits are sensitive to large-scale climatic variations but also the trees growing in habitats remote from the timberline have noticeably responded to past climate changes.     

三种阔叶树雌雄异株木材结构的比较

在光学显微镜下较详细地比较了重阳木、大叶刺篱木和红毛丹,雌雄异株木材的结构。结果表明：同一种树木两性间木材结构总体上是很相似的,但有的定量特征差异显著甚至极显著。３个种的树木中,雌株木纤维壁腔比值较雄株的大,而分膈纤维和纤维管胞数量较小。雌株木材结构特点可能表明其木材具较强的机械支持能力,利用于果实的支持 。     

Annual variation and influence of climate on the ring width and wood hydrosystem of Prosopis flexuosa DC trees using image analysis

We developed chronologies based on the width of tree rings, total area of vessels, and the number of vessels per tree ring of the Prosopis flexuosa wood samples from the xerophytic woodlands of central Argentina. We evaluated the influence of climate on these tree-ring characteristics considering the period from 1940 to 2004 (65 years). The width of the rings, the number of vessels, and the total area of vessels were positively influenced by regional precipitation corresponding to the seasonalized November to December period, which reflects the importance of the water availability in the initial stage of the formation of the wood. The width of the rings and the total area of vessels were negatively influenced by temperature during the same period, while the number of vessels was not significantly correlated with temperature. The high temperatures in spring increase evapotranspiration, which reduces water availability to plants and results in an inverse growth response. This study was the first to develop chronologies based on anatomical characters of wood from the arid and semiarid regions of South America and with significant applications in ecological and climatic studies.     

Micro-habitat niche differentiation contributing to coexistence of Eucryptorrhynchus scrobiculatus Motschulsky and Eucryptorrhynchus brandti (Harold)*

Temporal, spatial, and trophic niche differentiation usually occurs among species living in similar habitats which can reduce interspecific competition under limited resources. Eucryptorrhynchus scrobiculatus and Eucryptorrhynchus brandti are sympatric and closely related species and are host-specific to Ailanthus altissima (Mill.) Swingle in China. However, the possibility of niche differentiation between the two species is not clear. Therefore, we investigated the density of the two weevils temporally, spatially, and trophically (plant parts of A. altissima) at Lingwu farm and Haojiaqiao town, Lingwu city, Ningxia Hui Autonomous Region. No differences were found in temporal Levin’s niche breath index values ranging from 3.74 to 3.95 and temporal Pianka’s niche overlap values (0.98–0.99). There was little differentiation in the vertical spatial niche. The vertical distribution of E. scrobiculatus was mainly located from 0?cm (ground) to over 250?cm on tree-of-heaven. Eucryptorrhynchus brandti was found predominantly from 0.1 to 50?cm to over 250?cm on tree-of-heaven. The overlap of the cardinal direction spatial niche was 0.90–0.98, indicating no significant overlap in the cardinal direction at Lingwu farm and Haojiaqiao town. Significant differentiation of trophic niche occurred with E. scrobiculatus feeding on 1-year-old branches, perennial branches, and petioles, while E. brandti feed on the stem.     

一种枣植物组织改良的Steedman’s wax石蜡切片方法

为了建立一种简便、安全、快速的石蜡制片方法,减少试验过程中有毒试剂二甲苯的使用,以4个时期灵武长枣（Ziziphus jujuba ‘Lingwu Changzao’）的叶和果实为试验材料,采用改良的低熔点多酯蜡（Steedman’s wax）切片法观察不同时期的叶和果实结构特征,包括采用改良包埋试剂,省略二甲苯透明步骤,缩短试验过程,建立起一套可行的植物组织石蜡制片方法,并与常规石蜡切片方法比较,为研究植物组织结构特征提供新思路。结果表明：通过改良的低熔点多酯蜡切片法获得的叶片和果实组织的形态结构完整且染色清晰,该改良方法不但简化了试验步骤、缩短了制片周期,而且制得的切片质量与常规石蜡切片质量无差别,达到了优化试验步骤、避免二甲苯等有毒试剂使用、节省试验时间、整体上提高植物石蜡制片效率的目的,值得用于更多植物形态解剖学研究。     

Are climatic factors responsible for the process of oak decline in Poland?

Oak decline, a complex process leading to increased mortality of this species, has been observed in Europe for many years. Previous studies suggest that climate conditions, especially drought, may be one of the most important factors that trigger this phenomenon. The paper investigates the radial growth and wood anatomy features of pedunculate oak (Quercus robur) trees of various health status as well as their response to climate conditions. Wood samples including all annual increments were taken at two sites (western and central Poland, 15 trees each). Based on the crown defoliation level, three health groups (healthy, weakened and dead oaks) were distinguished. Cross-sections were prepared with sliding microtome and Cell P image analysis software was used for the measurements. Tree-ring width (TRW), earlywood vessels density (VDen) and non-weighted vessels diameter (VD) were determined and correlated with mean monthly values of temperature, precipitation, vapour pressure, and Palmer Drought Severity Index (PDSI). Radial increment and anatomical parameters were significantly higher for the healthy oaks than for the weakened and the dead trees. TRW showed smaller dependence on climate than analysed anatomical attributes. No obvious pattern of relationship was found between oak radial growth and climate regarding tree health status. Our results revealed that the drought has a weak impact on the process of oak decline on investigated sites in Poland.     

不同生境下蓝桉的木材解剖研究

用光镜及扫描电镜对不同生境下的蓝桉（Ｅｕｃａｌｙｐｔｕｓｇｌｏｂｕｌｕｓ Ｌａｂｉｌｌ．）木材结构进行了解剖学观察,描述了木材结构特征。以蓝桉木材的１１ 个主要特征——导管频率、单孔率、导管直径、导管分子长度、管胞长度和直径、纤维管胞长度和直径、纤维长度、射线频率和高度为指标,对生长在不同生境下的蓝桉进行比较发现：随着纬度的增加,生长轮变化不明显;木材中大部分组成分子的数量特征,除导管频率有降低趋势外均与纬度成正相关。评述了年降雨量对蓝桉木材结构的影响