人工接种后次代抗松材线虫松树的抗病性

为了解抗病松树后代对松树线虫的抗性,采用人工接种松树线虫,相隔一定时间调查其枯死情况,用3%酸性染料染色研究了抗性松与普通松水分输导情况,线虫的数量,结果表明,普通黑松3个月后枯死率为91.1%,次代抗性赤松枯死率为4.46%,除中央髓部的水分输导受影响外周边木质部和形成层未受影响;次代抗性黑松除两株水分严重受阻外,其他与赤松相似,接种线虫1周后从次代抗性松树上分离线虫最多,以后逐渐下降,5周后则很少.

从巴蜀区域文化的角度论何其芳的人格和文品

何其芳身上体现出巴蜀文人的行事风度和精神品格,具体表现为“松树性”和“柳树性”,其创作受乡土记忆影响,作品具有浓郁的巴蜀文化意味。

Responses of the seedlings of five dominant tree species in Changbai Mountain to soil water stress

Soil water stress was studied on the potted seedlings of five dominant tree species (Pinus koraienes Sieb.et Zucc., Fraxinus mandshurica Rupr., Juglans mandshurica Maxim, Tilia amurensis Rupr. and Quercus mongolica Fisch.ex Turcz) from the broadleaved/Korean pine forest in Changbai Mountain. Leaf growth, water transpiration and photosynthesis were compared for each species under three soil moisture conditions: 85%-100% (high water, CK), 65%-85% (Medium water, MW) and 45%-65% (low water, LW) of 37.4% water-holding capacity in field. The results showed that the characteristic of typical drought-resistance of the leaves is significantly developed. The net photosynthetic rate and water use efficiency of Fraxinus mandshurica were higher in MW than those in CK. But for the other four species, the net photosynthetic rate and water use efficiency in CK were lower than those in MW and LW. The transpiration rate responding to soil moistures varied from species to species.

Identification of seeds of Pinus species by microsatellite markers

The 276 pair-primers （nuclear and chloroplast microsatellite） developed from seven species of Pinaceae were selected and identified for cross-species transferability to ten Pinus species （P massoniana, P kesiya, P tabulaeformis P densiflora, P thunbergii, P caribaea, P taeda, P yunnanensis, P densata, P sylvestris）belonging to Sect. Pinus by BSA （bulked segregate analysis） method. The results showed that 23 of 276 （8.0%） markers were successful to have amplification product in ten species, and 5 of 23 （21.7%） were polymorphic cross species and lack of polymorphic within species. Eight of 10 Pinus species were identified by using single primer, two and more combination of primers, but there were still no effective SSR primers for identifying other 2 species （P. kesiya and P. densata）.

Susceptibility of pine stands to bark stripping by chacma baboons Papio ursinus in the Eastern Highlands of Zimbabwe

The aim of this study was to determine the susceptibility, intensity and distribution of pine trees to bark stripping by chacma baboons Papio ursinus in three plantations in the Eastern Highlands of Zimbabwe. The number of plots/ha, stripped trees/ plot and stripped trees/ha was recorded during the pre-rainy, rainy and post-rainy seasons from August 2006 to May 2007. During data collection, altitude, aspect, season and other site predictor variables （e. g., roads and fire traces, water points, indigenous vegetation conservation areas, crop felds, human settlements, wattle scrubs, rocky areas, open grasslands, earlier stripped sites and roost sites） were recorded for each plot in association with selected predictor variables within plantation estates. Data on the number of stripped plots/ha, stripped trees/plot and stripped trees/ha were analysed as dependent variables using the Generalised Linear Model （GLM） through SPSS version 15 （2006） to determine which predictor variables were significantly related to bark stripping. Differences between means were tested using Bonferroni tests with a 5 % level of significance. Our findings show that bark stripping of pine trees by baboons occurred at all altitudes and aspects. Overall, the number of bark stripped trees/ha did not significandy vary by season. The number of bark stripped plots/ha was lower during the pre-rainy season than the rainy season, whereas the number of bark stripped trees/plot was higher during the pre-rainy than the rainy season. Bark stripping of pines occurred more often in the vicinities of areas with abundant food and water

Effect of Distances from Different Trees Species on the Properties of Mollic Horizon

The study area is located in Duhok province-Kurdistan region-Northern Iraq and including two locations the first location is situated in Galbook village and the vegetation cover is trees of （Quercus aegilops L.）, the second location is situated in Koradeer village that covered with threes of Prunus dulcis （Mill.） Webb.. Disturbed surface soil samples at depth 0-30 cm were collected at four different distances （1, 5, 10 and 15 m） from the tree with randomized selection three trees in each study location. Soil organic matter decreases with increasing distances from tree in both locations under two different trees species, which is attributed to the effect of tree crown. Ordinarily, organic matter content in both locations correspond to the requirements of Mollisols. Statistical analysis of data showed significant differences in organic matter content between locations. Cation exchange capacity is high under tree crown and decreasing with distances from tree in both locations, as a result of decreasing organic matter and increasing calcium carbonate with distances. Commonly soil pH is slightly increased with increasing distances from tree because of increasing calcium carbonate with distances and decreasing organic matter content. Calcium was not uniform with distances and Mg decreasing with distances in both locations. The values of fine clay/coarse clay and fine clay/total clay of soil samples confirm development of the soils under study. Porosity percentage under tree crown is high and decreasing with distances. Soil bulk density was increased with distances in both locations, as a result of decreasing organic matter content with distances. This study aims to explain the effect of tree distances and species on the mollic horizon properties.

Water Absorption and Degraded Stress Relaxation Behavior in Water-Borne Anticorrosive Urethane/Epoxy Coatings

The kinetics of water absorption in water-borne anticorrosive urethane/epoxy coatings, which were actually introduced in the industrial field, are studied. It is found that the high water affinity of a water-borne coating supports a higher saturated water content, Mχ, and helps to facilitate absorption D. The three parameters of stretched exponential function called the William-Watt equation, Eo, τ, and β, are determined to fit the degraded stress relaxation behavior in the water absorption process because this function quantitatively describes the relaxing ability and has been successfully used by a number of researchers. An increasing in the water content is shown to correlate strongly with a decrease in Eo and fl early in the absorption process between Mt/M（χ） = 0 and Mt/Mχ≈ 0.5. The adhesive characteristics of the coatings are correlated with water content, and shown to exhibit higher cohesive failure in coating epoxies under saturated conditions. This suggests that water interferes with the intermolecular bonding between polymer chains which degrades the bulk materials ability to diffuse stress concentrations and reduces its overall strength.

Spatial patterns of a savanna palm tree Borassus aethiopum and its temporal variability

The spatial distributions and associations of plant species in a stand can provide essential information about their dynamics.However,since tree spatial distribution and association depend on factors that operate at different scales,disentangling the effects of environmental heterogeneity and plant-plant interactions requires the choice of a suitable null model for spatial analysis.We analyzed the spatial distributions of the same savanna palm tree populations that were studied,the underlying hypothesis being that these distributions have changed in 20 years.To remove the effect of large-scale environmental heterogeneity,the inhomogeneous L-function under the heterogeneous Poisson null model was used.We showed:(i)unlike 20 years ago,adults had a regular distribution instead of an aggregated distribution in the grass savanna;(i)although the spatial distribution of seedlings and juveniles was always aggregated,we observed a decrease in the size of the aggregates(intensities);ili)except for juveniles,no other stages were associated with nutrient-rich patches,which was also different 20 years ago;(iv)we did not observe any particular difference in structure between two study sites,only that female palm trees were spatially associated with entire-leafed seedlings in the reserve while they were spatially independent in the rural area.Our study supports the hypothesis that the spatial distributions have partially changed,and that the management of spatial heterogeneity has improved and given more precision in the results.

Study on Surface Energy Characteristics of Poplar and Yellow Pine Strands

The objective of this study was to investigate the surface free energy of poplar and yellow pine strands by Wilhelmy Plate Method. The measurement items included the surface contact angle, surface free energy and change of sample weight. Thirty industrial strands were randomly collected for each condition. The samples were cut down to 25.0-26.0 mm long, 7.0-8.0 mm wide. The density and thickness of each sample were also tested. The range of density was from 0.35 to 0.75 g/cm^3 and the range of thickness was from 0.5 to 1.0 ram. The research result shows that there is a close relationship between the wettability, mass change and moisture content. Both the density and the thickness of the strand have a small influence on the surface contact angle and the surface free energy.

Study on Wood Drying Properties under Vacuum-floating Pressure

Using Masson pine as specimens, when drying mediums are overheated steam and hot-air respectively, preheating characteristics of wood under vacuum-floating pressure drying are discussed by measurement of internal temperature field and variation of moisture content during period of preheating. The relationship between drying medium conditions and drying rate of wood reveals that, firstly, compared with process of air-drying, time needed to be preheated under vacuum-floating decreased dramatically, meanwhile,the magnitude of condensation on the surface is relatively larger. Secondly, drying rate of wood under vacuum-floating pressure increases coupled with temperature of medium, reduction of absolute pressure,and raise of fluctuation rate of pressure. The sequence of factors contribution to drying rate is listed as following: temperature of medium (t) > fluctuation rate of pressure (f)> absolute pressure (p).