Ex situ genetic conservation potential of seeds of two high elevation white pines

Genetic variation in a plant species is a key to its ability to survive and evolve in the face of changing environmental pressures. Due to insect and disease impacts, changes in fire regimes, and a changing climate, many populations of high elevation white pine species continue to experience high mortality levels and potentially worrisome decreases in genetic variation. In recent years, some trees rated highly for resistance to the non-native white pine blister rust have been killed by fire or mountain pine beetle. Ex situ genetic conservation offers the possibility to conserve the genetic variation within a species before much of it is lost. For many conifer species, freezer storage of seed offers a relatively inexpensive, long-term method of storing germplasm for future use. However, there is uncertainty concerning how long seed of some conifers can be stored and retain viability. We report here on results of germination testing of the oldest known seedlots of whitebark pine (Pinus albicaulis Engelm.) and foxtail pine (P. balfouriana Grev. & Balf.), some of which had been in storage for several decades. The 52 whitebark pine seedlots averaged 47.7% germination (average seed age of 19.2 years), while the four foxtail pine seedlots had an average germination of 71.3% (average seed age of 15.3 years). Some seedlots of both species had greater than 90% germination. Refinements to the stratification procedure have since been developed which should enhance germination further. A follow-up study examining seedling vigor of long-stored whitebark pine seed is planned.     

Reproductive investment of <Emphasis Type="Italic">Pinus pseudostrobus</Emphasis> along an altitudinal gradient in Western Mexico: implications of climate change

Climate varies along altitudinal gradients and species performance may be affected in response to these variations. Climate change can modify these gradients and, at the lower limit of species distributions, individuals may become stressed and their general health and reproductive performance may decrease. Study and prediction of the effects of climate change on the distribution of species along these gradients is therefore necessary. Our model study species, Pinus pseudostrobus, is a widely distributed pine in Mexico, ranging from 1600 to 3200 masl in altitude. In order to explore changes in health condition and reproductive investment along an altitudinal gradient, ten reproductive trees were selected in each of four populations (at 2300, 2400, 2700 and 2900 masl). As a proxy of individual health, we conducted a rapid visual assessment for each tree, based on crown defoliation, dead branches and foliage discoloration. This stress condition index (SCI) ranges from zero to fifteen, and lower values indicate low stress and therefore better health conditions. We also evaluated reproductive (cone weight, number/weight of seeds) and progeny (germination/seedling growth) traits. In addition, the relationships between SCI and the reproductive/progeny traits were assessed. The lowest altitude population presented poor health, with higher values of SCI (mean ± SE = 6.3 ± 0.9) that reduced up to 4.8-fold in higher-altitude populations. Cone weight also differed among altitudes, with lighter cones in the lower population (mean ± SE = 38.2 ± 4.3 g), and 1.5-fold heavier cones found in the higher populations. In general, all of the reproductive/progeny traits differed among altitudes. The population of intermediate altitude (2700 masl) presented the highest values for all traits evaluated, indicating higher performance at this altitude. Finally, a negative relationship was found between stress condition and cone weight. Based on our results and climate change models and their predictions, an increase in physiological stress can be expected in individuals of low altitude populations. Furthermore, possible increases in pests and pathogens are likely to contribute to the decline of this population. It is therefore necessary to maintain efforts of stress condition assessment and population dynamics, as well as to permanently monitor the climate along altitudinal gradients.     

Communities of saprobic fungi on leaf litter of <Emphasis Type="Italic">Vismia guianensis</Emphasis> in remnants of the Brazilian Atlantic Forest

We examined the mycobiota associated with Vismia guianensis leaf litter in three Atlantic Forest remnants of Brazil’s semiarid region. Among the study sites, two remnants were protected forest reserves, whereas the third was influenced by major anthropogenic activities. Eighteen litter samples were collected in wet and dry seasons and were processed by particle filtration technique. A total of 4750 fungal isolates of 142 taxa were identified. Species richness was higher in litter samples collected during wet season. Nonmetric multidimensional scaling multivariate analysis showed differences in the composition of fungal communities among the sampling sites and the seasons. Analysis of similarity showed that the differences were statistically significant (R = 0.85; P = 0.0001). Our findings revealed that spatial and temporal heterogeneity, and human activities had significant impacts on the saprobic fungi of V. guianensis leaf litter.     

Time Consumption and Production Costs of Two Small-Scale Wood Harvesting Systems in Northern Greece

A field-based study was carried out to determine the productivity and production cost of the tree length (TL) and the wood assortment (WA) systems implemented under small-scale forestry conditions in two Scots pine stands in Northern Greece. Tree felling and processing productivity were estimated at 8.64 m³ per productive machine hour (PMH^?1) and 10.21 m³ PMH^?1, respectively. Wood felling and processing times were strongly dependent on dbh and total tree volume. However, when manual debarking was also considered the productivity rates decreased to 1.96 and 1.43 m³ PMH^?1, respectively. Skidding productivity was calculated to be 3.35 m³ PMH^?1 for TL and 7.17 m³ PMH^?1 for WA, respectively. Strong correlations have been found between the net skidding time and (a) the skidding distance and (b) the load per turn in both wood harvesting systems. Production costs varied greatly, from 19.38 € m^?3 up to 44.81 € m^?3 of roundwood depending on the harvesting system and the inclusion of debarking. The findings suggest that the WA system is more efficient in terms of productivity and production cost than TL, and that there is a substantial optimization potential. The optimization potential can be encoded in four suggestions: (a) opening up of more forest roads to reduce high skidding times, (b) replacement of manual debarking by mechanical debarking at the sawmill, (c) replacement of old pieces of equipment with newer ones and (d) training of the existing workforce.     

A Survey of Logging Contract Rates in the Southern European Alps

A survey of harvesting contracts was conducted in the Alpine regions of France and Italy. The main goal was to produce a benchmark for the harvesting contract rates in the area that may guide forest owners and logging contractors when making their harvesting decisions. The sample included 443 contracts, evenly distributed between France and Italy. The mean tract size was 9.17 ha, while the mean lot size was slightly larger than 500 m³ under bark (ub). Mean removal intensity varied from 70 to 120 m³ ub ha^?1, depending on country and harvesting technique (i.e. ground-based or cable-yarder based). Mean contract rate was 35€ m^?3 ub, but individual contract rates varied significantly between countries and for different harvest techniques. Regression analysis showed that contract rate was strongly affected by tree size, extraction distance and harvest technique. Contrary to expectation, neither tract size nor lot size had any effect on contract rate. This may be explained by the widespread use of mobile operations that are specifically designed for handling small lots and incur minimum relocation cost. The technical factors explored in the study could only explain 40 % of the variability in the dataset, and therefore at least part of the variability must derive from non-technical factors such as local market dynamics and national economics. The study did find significant differences between countries. In particular, ground-based operations were more cost efficient in France, and cable yarder-based operations in Italy.     

The effect of surface fire on tree ring growth of <Emphasis Type="Italic">Pinus radiata</Emphasis> trees

Key message

Pinus radiata trees showed significantly reduced basal area increments and increased latewood/earlywood ratios, when their stem was charred by surface fires even if no needle damage occurred. An interaction of fire damage and precipitation on growth was observed.

Context

Heat from forest fires is able to penetrate beyond the bark layer and damage or completely kill a tree’s cambium. Short-term growth reductions following surface fires have been reported for some species. However, most studies have in common that they describe a compound effect of stem and foliage damage.

Aims

This study investigated the impact of surface fires on the radial growth of Pinus radiata, where only the stem of trees was charred, while no needle damage was recorded.

Methods

Tree ring measurements were performed on cores obtained at breast height. Analysis of variance and tests, based on annual basal area increment values were calculated to quantify pre- and post-fire growth differences of tree ring width and latewood/earlywood ratios.

Results

The analysis revealed significant growth reductions following a surface fire on P. radiata in the year on which the fire occurred as well as in the following year. As a consequence of the fire, basal area increment and latewood/earlywood ratios were significantly reduced. An interaction of fire damage and precipitation on growth was observed.

Conclusion

The obtained results show how fires without crown damage can affect growth and tree ring structure of P. radiata trees and indicate that stem char could be associated with a significant decrease in ring width and latewood/earlywood ratio.

     

Xylem traits in European beech (Fagus sylvatica L.) display a large plasticity in response to canopy release

Key message

The position of trees in the canopy impacts xylem structure and its inter-annual variation. After canopy release, the increase in the hydraulic conductivity of growth rings was driven by an increase in radial growth in large trees, and by both an increase in radial growth and changes in xylem structure in saplings.

Context

Forest canopies are frequently subjected to disturbances that allow understory trees to access the upper canopy. The effect of canopy release on xylem anatomy has been assessed in juvenile trees and saplings, while the potential acclimation of larger trees remains poorly documented.

Aims

We estimated the potential hydraulic conductivity of growth rings in large understory trees compared to overstory trees, and evaluated the responses to canopy release in large trees and in saplings.

Methods

We recorded radial growth, wood density, and vessel structure in beech trees according to their position within the canopy and their size. Xylem traits were followed during 6 years after canopy release for large trees, and during 2 years for saplings. Vessel diameter and frequency as well as ring area were used to compute the potential annual ring hydraulic conductivity.

Results

Large understory trees displayed lower radial growth increments and lower potential annual ring hydraulic conductivity than overstory trees. After canopy release, potential annual ring hydraulic conductivity increased in large trees, due exclusively to increased radial growth without any change in specific hydraulic conductivity. It increased in saplings due to both increased radial growth and increased specific conductivity.

Conclusion

Tree size impacted xylem structure and resulted in plasticity of the potential hydraulic conductivity of the annual tree ring following canopy release.

     

黄杞容器扦插繁殖技术试验研究

通过正交试验设计L9（34）深入研究了使用不同种类生根促进剂（H ）来处理母株不同采插穗部位的插穗（F ）和插穗不同基部下切口型（E ）对黄杞扦插生根率、生根数及生根长的影响差异。试验结果表明：采用生根促进剂ABT －1＃（H1）＋母株下部采的插穗（F3）＋基部下切口型为双削面（E2）,即 H1 F3 E2组合试验效果最好,其平均生根率高达86．8％、平均生根数8．8条、平均生根长达18．6cm。     

北斗导航系统在新疆安全生产过程中的应用研究

针对新疆通信盲区多、移动信号覆盖差,安全事故信息不能及时上报,应急救援指挥严重滞后的现状,提出了建设针对长途客货营运车辆、危险品运输车辆、应急运输车辆、野外工程车的基于我国自主建设、独立运行的北斗卫星导航系统的安全生产运输车辆监控管理系统,提供面向各行业需重点监控各型车辆及其主管调度部门的基于位置的综合信息服务。从而实现生产事故应急救援指挥,有序开展野外事故设备、人员的搜寻,有效提高安全生产信息化水平。