Non-destructive monitoring of early stages of white rot by Trametes versicolor in Fraxinus excelsior

? Non-destructive detection of fungal decay in living trees is relevant for forest management of valuable species, hazard tree assessment, and research in forest pathology. A variety of tomographic methods, based on stress wave timing, radioactive radiation, or electrical resistivity have been used to detect decay in standing trees non-destructively. But apart from mobile gamma ray computed tomography (Habermehl and Ridder, 1993) which is virtually unavailable, the detection of incipient stages of decay is still not possible.

? Wood moisture and electrolyte content influence the electric resistivity of wood. Both are changed by fungal decay. Therefore electric resistivity tomography (ERT) should detect decay in its early stages. Then it could be used to monitor the spatial and temporal progress of degradation.

? We infected four Fraxinus excelsior trees with Trametes versicolor using wooden dowels and measured two-dimensional electric resistivity tomograms 3, 10, 13 and 21 months after infection. Immediately after the last electric resistivity measurement trees were felled for further analyses of stem cross-sections. Wood moisture content and raw density had significantly increased in infected areas, but dry density had not significantly changed after 21 months. Areas of very low electric resistivity around the infected wounds correlated very well with infected wood in the stem cross-sections. Increasing areas of low electric resistivity around the infected wounds during consecutive measurements indicate increasing areas of infected wood.

? We conclude that the growth of white rot by Trametes versicolor can be monitored with electric resistivity tomography (ERT) beginning from incipient stages, even before wood density decreases. ERT could therefore be a powerful research tool for decay dynamics as well as a method for diagnosing wood decay in forestry and arboriculture.

     

Nondestructive detection of decay in living trees

We used a four-point resistivity method to detect wood decay in living trees. A low-frequency alternating current was applied to the stem and the induced voltage measured between two points along the stem. The effective resistivity of the stem was estimated based on stem cross-sectional area. A comparison within a group of trees showed that trees with butt rot had an effective resistivity that was at least a factor of two lower than that of healthy trees. In tests on several groups of Norway spruce (Picea abies (L.) Karst.) comprising more than 300 trees in total, the method detected butt rot with high accuracy. We validated the method both by measurements and by finite element modeling and simulations.     

Complex resistivity tomography (CRT) for fungus detection on standing oak trees

Complex resistivity tomography is presented as an extension of electrical impedance tomography for non-destructive structural tree investigation. Results of laboratory measurements with different frequencies suggest measuring the resistivity and in addition the phase shift at about 0.1 Hz. The measured data are processed using a finite-element-based inversion algorithm, which uses triangular meshes and is thus able to consider any tree shape. We apply the technique to three different oak trees with the aim of fungi detection. Measurements of a healthy tree both in summer and in winter show a ring-shaped structure and indicate a strong seasonal dependence, particularly for the resistivity magnitude. Tomograms on fungi-infected trees clearly show disturbances at the infections at different heights compared with healthy trees. A comparison with tree section photographs shows promising agreement. Moreover, a comparison with measurements at oak-wood samples in the laboratory shows at least partly quantitative coincidence. To conclude, the phase image provides additional information and helps to differentiate disturbances in the cell structure from pure moisture changes. Therefore, the method has the potential to deliver useful additional information, when carried out during routine tree assessment.     

大兴安岭松岭大扬气林场落叶松生长规律研究

树木生长量的大小及生长速率,一方面受树木本身遗传因素的影响,另一方面也受所处环境条件的制约。以大扬气林场的兴安落叶松为研究对象,基于其37株标准木的树干解析、生长数据,利用线性模型、对数模型、多项式模型、指数模型研究不同测树因子(胸径、树高等)之间的关系,分析模拟其生长规律。结果表明:在研究区域内,多项式模型模拟所得到的相关系数相对较高,因此可以利用此模型来预估此区域落叶松的生长规律。     

Stem breakage of trees and energy dissipation during rockfall impacts

The capacity of individual trees to dissipate the energy released by rockfalls has previously only been quantified based on data obtained from static tree-pulling tests or from dynamic impact tests on wood samples. We predicted that these data are not representative of the maximum amount of energy that can be dissipated by living trees during rockfall impacts. To test this prediction, we carried out rockfall experiments on a forested slope in the French Alps. To calculate the rock's energy before and after impact, rockfalls were filmed digitally. The recordings of nine impacts causing instantaneous breakage of Abies alba Mill. trees were analyzed in detail. An exponential relationship between stem diameter at breast height (DBH) and the maximum amount of energy a tree can dissipate was highly correlated for all of our experimental data. We applied this relationship to other tree species based on published fracture energies. The relationships obtained for Cedrus spp., Fagus sylvatica L. and Picea abies (L.) Karst. were significantly correlated with data from other dynamic impact tests in the field and with maximum bending moments obtained from tree-pulling experiments. Multiple linear regressions showed that impact height influences the energy that will be dissipated by an A. alba tree, particularly for trees with a DBH less than 15 cm. For trees with a DBH greater than 15 cm, the effect of impact height was minimal up to a height of 1 m. There was a strong relationship between the amount of energy dissipated by a tree and the horizontal distance between the impact center and the vertical central axis of the tree.     

How fast do European conifers overgrow wounds inflicted by rockfall?

The capacity of trees to recover from mechanical disturbance is of crucial importance for tree survival but has been primarily investigated in saplings using artificially induced wounds. In this study, mature Larix decidua Mill., Picea abies (L.) Karst. and Abies alba Mill. trees growing on alpine slopes that were wounded by naturally occurring rockfall were analyzed to determine their efficiency in overgrowing wounds. In total 43 L. decidua, P. abies and A. alba trees were sampled. First, 106 samples from 27 L. decidua and P. abies trees were analyzed to reconstruct yearly and overall overgrowth rates. Cross sections were taken at the maximum extension of the injury and overgrowth rates were determined on a yearly basis. Results clearly showed that L. decidua overgrew wounds more efficiently than P. abies with an average overgrowth rate of 19° and 11.8° per year, respectively. The higher on the stem the injury was located, the faster the wound was closed. Young and small trees overgrew wounds more efficiently than older or thicker trees. In contrast, no correlation was observed between injury size or increment before/after wounding and wound closure. Second, cross sections from 16 L. decidua, P. abies and A. alba (54 injuries) were used to assess closure rates at different heights around the injury. Overgrowth was generally smallest at the height of the maximum lateral extension of the injury and increased at the upper and lower end of the injury. The efficiency with which L. decidua closes wounds inflicted by rockfall makes this species highly adapted to sites with this type of mechanical disturbance.     

Invasive sequence and ecological niche of main insect borers of <Emphasis Type="Italic">Larix gmelinii</Emphasis> forest in Aershan,Inner Mongolia

After the outbreak of Dendrolimus superans Buter in 2002, many insect borers quickly invaded larch （Larix gmelinii Rupr.） forests in the Aershan of Inner Mongolia. Methods involved included setting sample plots, collecting adults in iron traps and measuring areas of galleries to study the invasive sequence, their ecological niche and the extent of the different effects by the main insect borers to their hosts. The results showed that the damage of D. superans weakened L. gmelinii, first Ips subelongatus Motschulsky invaded, followed by Acanthocinus carinulatus Gebler, Monochamus urussovi Fisher and M. sutor L. After the outbreak of D. superans, the average density of longhorn beetles per L. gmelinii tree increased. The ecological niche of Ips subelongatus stretches almost from the base to the top of the trunk. The number of insects in older stands of L. gmelinii is larger than those in middle aged stands. They do not damage healthy trees of L. gmelinii. The ecological niche of A. carinulatus is higher in dead L. gmelinii trees than in weak ones. The degree of damage is directly proportional with age and depth of bark. M. urussovi mainly damages trunks below 4 m in weak trees; in dead trees they can do damage up to 6 m in height. M. sutor mainly damages trunks below 5 m in weak L. gmelinii trees; in dead trees they cause damage up to 7 m. Again, the degree of damage is directly proportional with age. None of the three species of longhorn beetles damage healthy L. gmelinii and younger trees. Among the main insect borers, the degree of damage caused by I. subelongatus is more serious than that of other insects.     

In situ detection of tree root distribution and biomass by multi-electrode resistivity imaging

Traditional methods for studying tree roots are destructive and labor intensive, but available nondestructive techniques are applicable only to small scale studies or are strongly limited by soil conditions and root size. Soil electrical resistivity measured by geoelectrical methods has the potential to detect belowground plant structures, but quantitative relationships of these measurements with root traits have not been assessed. We tested the ability of two-dimensional (2-D) DC resistivity tomography to detect the spatial variability of roots and to quantify their biomass in a tree stand. A high-resolution resistivity tomogram was generated along a 11.75 m transect under an Alnus glutinosa (L.) Gaertn. stand based on an alpha-Wenner configuration with 48 electrodes spaced 0.25 m apart. Data were processed by a 2-D finite-element inversion algorithm, and corrected for soil temperature. Data acquisition, inversion and imaging were completed in the field within 60 min. Root dry mass per unit soil volume (root mass density, RMD) was measured destructively on soil samples collected to a depth of 1.05 m. Soil sand, silt, clay and organic matter contents, electrical conductivity, water content and pH were measured on a subset of samples. The spatial pattern of soil resistivity closely matched the spatial distribution of RMD. Multiple linear regression showed that only RMD and soil water content were related to soil resistivity along the transect. Regression analysis of RMD against soil resistivity revealed a highly significant logistic relationship (n = 97), which was confirmed on a separate dataset (n = 67), showing that soil resistivity was quantitatively related to belowground tree root biomass. This relationship provides a basis for developing quick nondestructive methods for detecting root distribution and quantifying root biomass, as well as for optimizing sampling strategies for studying root-driven phenomena.     

小兴安岭落叶松人工林立地指数表的编制

通过对小兴安岭8个林业局各种不同立地条件下落叶松人工林的调查,选设88块标准地的优势木和平均木,编制出落叶松人工林立地指数表,实现了合理经营落叶松人工林的目的。     

Simple models for light competition within agroforestry discontinuous tree stands: are leaf clumpiness and light interception by woody parts relevant factors?

Predicting the temporal and spatial variability of radiation intensity under wide-spaced tree stands is required for many applied issues in savannah-like ecosystems, orchards, agroforestry and urban forestry systems. Numerous authors have advocated the use of simple light interception models that approximate the crown shape with ellipsoids. They have suggested taking into account leaf clumping to improve the efficiency of these simple models, but this was never assessed. We tested this hypothesis together with the impact of including predictions of light interception by woody parts (trunks, branches). We calibrated and evaluated the model using cross-validation across eight walnut trees with field measurements of radiation intensity and spatial heterogeneity using hemispherical photographs. Leafless trees were efficiently modelled using Wood Area Density (WAD, m²m⁻³) for branches and an opaque cone for the trunk. We introduced a clumping parameter (μ) but this proved inefficient, clumping being highly variable amongst trees. This results from the limitations of representing the crown as an ellipsoid, a procedure too coarse to be improved by using a clumping parameter. The model proved efficient to predict the light pattern around an average tree, but was not fit for simulating the variability of individual trees. We finally discuss practical recommendations for modelling light competition in integrated agroforestry models simply.     

大兴安岭地区落叶松生物量模型研究

以不同年龄、不同密度的落叶松(Larix gmelini)人工林为研究对象,基于标准地37株标准木的树干解析、枝解析的生物量数据,研究胸径、树高、冠幅等指标与单木各分量(树干、枝、叶)生物量之间的关系,通过统计分析建立了落叶松单木各部分生物量的回归模型,为了解落叶松人工林生产力,并对其进行合理经营提供了科学依据。     

板栗树皮电阻值与枝干病害的关系

利用万用电表对板栗枝干病害的病情程度与树皮电阻值的关系进行了研究。结果表明：在不同的植株间,树皮电阻值随着病情的加重而增加;在同一植株上,树皮电阻值随着树体的高度增加而增大;在树干基部、主枝和梢头三个部位中,电阻值差异比较显著．诙研究为今后板栗乃至其他林木枝干病害研究提供了一种简便易行的新方法。     

Effects of heavy,repeated bark stripping by Cervus nippon on survival of Abies veitchii in a subalpine coniferous forest in central Japan

The management of deer impacts on forested lands requires quantification of the negative factors(e.g.,bark stripping) on tree survival in relation to other ecological variables(e.g.,competition from neighboring trees).This study measured the effects of bark stripping by sika deer,Cervus nippon,and competition among trees on the survival of Abies veitchii in a subalpine coniferous forest in central Japan over 12 years.Most of the trees subjected to bark stripping by deer were small(10 cm in diameter at breast height);however,some trees were stripped repeatedly.Although light bark stripping did not strongly influence tree survival after 12 years,heavily stripped stems(i.e., 65% of the stem circumference stripped) were severely affected.The effect on longevity for each tree after bark stripping was explained by maximum bark stripping intensity during the study period,rather than initial bark stripping intensity.When 85% of the stem circumference had been stripped,survival rates decreased.Bark stripping influenced survival rates much more than competition from neighboring trees.Because bark stripping occurred repeatedly,frequent measurements are important to grasp the full effects caused by this action.Heavy bark stripping of a stem enhances tree mortality.Thus,management of bark stripping is an essential element of stand maintenance and species composition in subalpine coniferous forests in Japan.     

手持式测树枪量测树冠体积方法研究

为实现单木树冠体积的精准测量,文章介绍了一种手持式测树枪量测树冠体积的方法。在被测树周围布设测站点,以一定的顺序获取各测站点正对树冠边缘点位坐标,通过等高线内插法分层,以构成多面体,利用积分算法求算树冠的体积。将电子测树枪所测结果与传统方法、无棱镜全站仪以及三维激光扫描仪所测结果进行对比分析。结果表明,测树枪所测精度与等高距呈线性关系,测树枪所测精度远高于传统方法,略低于无棱镜全站仪,低于三维激光扫描仪的精度,满足林业调查精度要求,可以在林业行业中推广使用。     

Algorithm for improving the co-registration of LiDAR-derived digital canopy height models and field data

Improving trees location under LiDAR-derived digital canopy height models (DCMs) is of great interest as discrepancies between both dataset influence the accuracy of the estimations of forest attributes. A method is proposed for the co-registration of LiDAR-derived DCMs with local field positional measurements under a dense tree canopy. This approach consists of two main stages: (1) the assessment of the match between the LiDAR-derived digital terrain model and topographic surveying measurements when shifting the coordinates around a measured position; and (2) a comparison between the field height of selected trees and the LiDAR-derived DCM. Satisfactory results were obtained from geo-referencing field data and LiDAR models for characterizing the forest structure in heterogeneous Pinus sylvestris stands. Closure error of topographic surveying was 17.7 cm, and GPS accuracy to 95 % probability was below 10 cm, thus considerably lower than the resolution of the LiDAR models (1 m-pixel). The best co-location for field trees and LiDAR models provided a coefficient of determination of 0.56 between field-measured tree heights and LiDAR-derived DCM values.     

Electric resistance as a measure of tree water status during seasonal drought in a tropical dry forest in Costa Rica

Variation in electric resistance of stem tissues was used to measure differences and changes in water status among trees in a tropical dry forest in Costa Rica during the dry season. For more than 30 tree species, stem water content (SWC), measured as electric resistance between nails driven 20 mm deep into tree trunks, correlated well with wood density, saturation water content, dehydration, measured with the pressure chamber, and tree development during drought. At dry sites, SWC was lowest in hardwood trees (characterized by high wood density) and highest in stem-succulent lightwood trees (characterized by low wood density). Among hardwood trees, SWC varied with soil water availability. During the dry season, SWC declined before leaf shedding and increased during rehydration preceding bud break. The time course of seasonal changes in SWC apparently constitutes an indirect measure of variation in the relative water content of outer stem tissues, which determines development of dry-forest trees during the dry season.     

Tiarosporella durmitorensis sp. nov. – a new pathogenic fungus on needles of Abies alba

A fungus causing necrosis and needle cast has been discovered on fir trees (Abies alba) in a hight of 1700 m above sea level in Yugoslavia. The intensity of infection was very high, and the needles of all age classes were infected. The consequence of the infection is the death of the tree. The pathogen is described as a new species Tiarosporella durmitorensis Karad?i?. So far, this fungus has been found only in European silver fir stands in the National Park Durmitor and in the National Park Biogradska Gora (Montenegro).     

Oviposition preference of Anoplophora glabripennis emerging from five host tree species under field conditions

The Asian longhorned beetle （ALB）, Anoplophora glabripennis （Motschulsky） is a polyphagous woodborer of hardwood trees. In order to well understand the oviposition preference of A. glabripennis emerging from different larval host tree species, we selected five common host tree species in the field and evaluated its oviposition preferences. The five host tree species are Acer negundo （AN）, Salix matsudana f. lobato-glandulosa （SM）, Populus nigra L. var. thevestina （Dode） Bean （PN）, P. simonii × P. pyramidalis cv. Opera 8277 （PS） and P. alba var. pyramidalis （PA）. Results show that adult beetles emerging from these five tree species almost have the same oviposition phenomenon. All adult beetles, except those emerging from PS, chewed the highest potential sites and laid most eggs on AN trees. Adult beetles emerging from AN, PN, PS and PA did not chew any sites nor laid any eggs on PA trees. These results showed that adult A. glabripennis emerging from the five host tree species did not show any clear oviposition preference for their larval host tree species in the field but they did present the most obvious preference for AN and the lowest preference for PA.     

Growth and yield models for Dahurian larch plantations

IntroductionDahurianlarch(L8risgmeliniiRupr.)isoneofthemostimportanttimberspeciesinChina.AsaresuItofovercuttingforseveraIdecades,thenaturaIDahurianIarchforestresourcesaredecliningrapidly.PIantationsofdahurianIarchhavebecomeanimportantpartofforestpreserveresourcesinDaxing'anMountains.ConsequentIystudyingthegroWthofDahurianlarchandformingtheforesttabfesareofsignrficancetofor-estproduction.ThispaperpresentsinformationongroWthandyieIdmodeIsofDahurianlarchpIantations.MethodsDataof4O5stema…