Conifer leader browsing by roe deer in English upland forests: Effects of deer density and understorey vegetation

At moderate to high densities ungulates can impact negatively on forest crops and these may be managed by lethal control. In production forestry an understanding of the relationship between ungulate density, habitat-related factors and the incidence of tree damage may promote more efficient ungulate damage management than by lethal control alone. In plantation forests in the north east of England, the incidence of conifer leader browsing by roe deer (Capreolus capreolus) was positively associated with an index of deer density (at the site scale) and planted crop tree density (at the feeding patch scale) and was negatively associated with the relative abundance of palatable understorey vegetation (at the site scale). An interaction between the deer density index and palatable understorey browse abundance was positively associated with leader browsing. Coefficients from the optimal model were used to construct a browse probability surface across a matrix of values of deer dung density and palatable understorey vegetation abundance. This illustrated a very different relationship between dung density and conifer leader browsing probability across the various levels of palatable understorey vegetation abundance. From this we hypothesise that in areas of limited palatable understorey vegetation abundance, higher levels of culling may be required to achieve reductions in the incidence of conifer leader browsing than would be necessary in areas with moderate to high palatable understorey vegetation abundance. Improvements to understorey vegetation in concert with roe deer population control may enhance the efficiency of deer damage management in upland areas with nutrient-poor soils.     

Thickness swelling and density variation in aspen flakeboards

Summary This paper reports the relationship between thickness swelling and density in labmade aspen flakeboards. The boards were manufactured with several levels of initial mat moisture content and urea resin content. Weight increase and thickness swelling at 12 locations on each board were recorded under specified environmental conditions over a period of 71 days. Each board was then cut into 12 specimens, each containing one of the 12 locations at its center, and density was calculated. No definite relationship was found between thickness swelling and density among the 12 specimens of each board. Our results suggest that high initial moisture content and high resin content can decrease thickness swelling. Variations in mat pressure and core temperature during the press cycle and weight increase at 80 percent relative humidity are discussed.The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright     

猴猕岭野放坡鹿种群与栖息地现状

2003年开始由大田自然保护区向猴猕岭野放海南坡鹿,至2005年止共野放296头。2007年5月,海南林业局组织了海南坡鹿种群全面调查。我们对猴猕岭野放海南坡鹿种群数量与栖息地现状进行了调查,采用现场直观点数调查、样方调查和访问调查相结合的方法进行。调查结果为海南坡鹿530头,种群年均增长率约21．4％。事实证明了迁地野放坡鹿是成功的,为促进坡鹿种群的进一步发展及栖息质量不断改善,提出了相应的保护建议。     

Changes in spatial patterns of sika deer distribution and herbivory of planted seedlings: a comparison before and after deer population control by culling

Sika deer (Cervus nippon) sometimes cause extensive damage to planted tree seedlings. To evaluate the effects of culling on the spatial distribution patterns of sika deer and browse damage to planted seedlings, we compared the data collected before and after experimental culling in a cool, temperate, mixed forest on Kyushu Island, Japan. Experimental culling, conducted in an area of 1 km², removed five, four and two sika deer in April, June and October 2011, respectively. During the year before culling, the spatial pattern of the number of sika deer caught on camera corresponded to the predicted sika deer density. Sika deer immediately browsed planted seedlings after the initial planting. The cumulative number of browsed seedlings increased over time, especially in winter. The spatial pattern of the cumulative number of sika deer caught on camera corresponded to that of browsed seedlings at the year’s end. During the year when culling was conducted, the number of sika deer caught on camera decreased around the center of the study site where the culling was conducted and the number of browsed seedlings decreased. During the year following culling, the cumulative number of browsed seedlings was very similar to that in the year before the culling, while the same low number of sika deer was caught on camera. These results indicate that the effects of deer culling resulted in decreased levels of sika deer appearance and browse damage for more than 1 year and for several months, respectively.     

Genetic variation in wood density and correlations with tree growth in Prosopis africana from Burkina Faso and Niger

? Variation in wood basic density and its correlation with tree growth were investigated at 13 years in a provenance/progeny test of Prosopis africana in Niger. The test included progeny from 256 trees sampled from 24 provenances in the Sahelian ecozone of Burkina Faso and Niger.

? Variation in wood density was significant due to provenances and families within provenances. Individual tree heritability was higher for wood density than for growth traits. Provenance means for wood density increased from the more humid to the drier parts of the sample region. Phenotypic correlations indicated that larger trees tended to have denser wood.

? Clines suggest that natural populations of P. africana from the drier parts of the sample region have the genetic capacity to produce denser wood, compared with populations from the more humid parts of the region. Correlations and heritability estimates suggest that selection of faster-growing trees may produce a small gain in wood volume but little (if any) gain in density in the subsequent generation. Multi-location provenance/tests are needed to confirm this tentative conclusion.

     

Seedling density dependence regulated by population density and habitat filtering: Evidence from a mixed primary broad-leaved Korean pine forest in Northeastern China

Key message

The effects of distance dependence, negative density dependence (NDD), phylogenetic density dependence, and habitat filtering were integrated to provide additional evidence in temperate forest tree seedling survival. The main focus of this study was to explore how population density and habitat filtering regulate NDD. An approach involving four classes of population density and three classes of soil moisture was tested, including the effect of habitat variables to more accurately evaluate the underlying ecological processes affecting the density dependence of seedlings.

Context

NDD is an important mechanism for the maintenance of species diversity across multiple life stages, particularly during seedling recruitment. By regulating specific population structures to maintain species diversity, the effects of density dependence and distance dependence are sometimes difficult to distinguish. Nevertheless, the contribution of NDD to community assembly, relative to other processes such as habitat filtering, remains a subject of debate. Recently, it has been reported that seedling survivals are also negatively correlated with phylogenetic relatedness between neighbors and focal individuals. This effect is known as phylogenetic negative density dependence (PNDD). However, another opposite effect known as phylogenetic positive density dependence (PPDD) has also been reported to exist.

Aims

The objectives of this study are to examine the following: (i) how population density affects negative density dependence (NDD); (ii) how habitat filtering regulates the NDD; (iii) whether more evidence can be found for PNDD or PPDD and why; and (iv) whether the intensity of negative density dependence is affected by the distance between parent trees and seedlings.

Methods

The study was conducted in a 20-ha primary mixed broad-leaved Korean pine forest in Changbai Mountain of China. We used generalized linear mixed models to analyze how the seedling survival of 23 woody plant species relates to neighborhoods and habitat variables. Four models were established with and without habitat variables, and two of the four models were used to test how different population densities of focal seedlings and different gradients of habitat variable regulated negative density dependence.

Results

The following results were obtained: (1) the strongest conspecific negative density dependence (CNDD) was found within a radius of 15 m; (2) seedling survival were most strongly impacted by the density of conspecific seedling and adult neighbors in habitats with relatively low soil moisture; (3) the effect of seedling-seedling CNDD was especially significant, when densities ranged from 20 to 40 seedlings/4 m², and (4) there were some evidences of phylogenetic positive density dependence (PPDD), and the effect of seedling-seedling PPDD was increasing with an increase in soil moisture.

Conclusion

Our results demonstrate that conspecific negative density dependence played an important role in seedling survival, which is closely related to habitat filtering and population density. However, we found some evidences of phylogenetic positive density dependence. We suggest that future studies of neighborhood density dependence should increase awareness of evolutionary relationships.

     

ESTIMATING DENSITY AND POPULATION SIZE OF TIBETAN SNOWCOCK IN TIBET

PREFACETibetansnowcock(Tetragallustibetanus)isakindofplateaubird,whichlivesinhighestlandamongseveralpheas-antsintheworld.ThesnowcockismainlydistributinginTibetanditshabitatstretchesfromeastinQinlingMountainstowestinPamirPlateau.Tibetisavastexpanseofplateauterritorywithe1evationofmorethan4,OOom.TherearemanysnowmountainsinTibet,especial1yinwesternparts.Theriversand1akesspreadovera1lplaces.BecauseofhightopographyfeaturesandtheHimalayasmountainsys-temacrossfromeasttowest,thechimateisveryco…     

乌桕群体/家系苗期性状遗传变异

于2009年11月采集四川、重庆地区10个乌桕群体共300个家系种子,在四川达州市林业中心苗圃播种育苗,并进行苗期观测,结果表明:乌桕群体/家系的苗高、地径、主根长、侧根数、分枝数均存在极显著差异,苗期表型平均分化系数为17.63%,群体内的变异大于群体间的变异;5个性状的家系遗传力受中等强度的遗传控制,单株遗传力受中等到高等强度的遗传控制;以欧式平均距离5为阈值聚类,10个群体可聚为北部群体、中部群体和南部群体3大类。     

White-tailed deer activity reconstructed from tree-rings in eastern boreal Canada

We evaluated the potential of tree-ring techniques for the reconstruction of recent and past seasonal activity of introduced white-tailed deer in a boreal environment of eastern Canada. Hoof scrape scars on balsam fir stems and trampling scars on roots were used to reconstruct deer activity during the winter and snow-free seasons, respectively. Tree damage showed that there was continuous deer activity in the north-central part of Anticosti Island since the mid-1960s. High scrape scars along tree stems (3–3.5 m from the ground) indicate that 1975, 1976, 1981, 1983 and 1985 were years of intensive food search by deer on high balsam fir foliage. The annual number of hoof scrape scars was low between 1982 and 1985, when severe defoliation by the spruce budworm, combined with deer browsing, led to high fir sapling mortality, food depletion, degradation of the winter shelter forests and a decrease in deer activity. The lowest scrape scars 50 cm above ground correspond to the mean height of the residual snowpack in the shelter forest at springtime, when deer start searching for food in nearby open sites and use logging roads, where dead and bonsai-like fir predominate due to overbrowsing. The trampling scar age frequency distribution from two sites indicated that deer activity during the snow-free season started synchronously in the late 1960s. In response to degradation of winter shelter forests, deer may have moved from the southern part to the north-central part of the island and other sectors to survive. Deer-induced tree damage and tree-ring techniques can thus be used to reconstruct past seasonal activity of white-tailed deer.     

Between- and within-site variation of density and bending properties of Picea abies structural timber from Norway

This study provides an analysis on the variability of structural timber of Norway spruce (Picea abies) grown in Norway. Density, modulus of elasticity (MOE) and bending strength were measured on 1188 boards from 205 trees, sampled from 14 sites throughout Southern Norway, Eastern Norway and Trøndelag. The area represents the procurement area for the majority of Norwegian sawmills. The variability of the timber properties was analysed in a linear mixed model where the random variance was divided into variance due to site, variance due to trees and within-tree variance. Models describing variance due to site based on site index, altitude and latitude were developed, and combined with data from the Norwegian National Forest Inventory to estimate mean values and variability of the timber properties. The results showed that major parts of the variance due to site are explained by altitude and site index, and for density also by latitude. Major parts of the variance due to site and the variance due to trees in bending strength and MOE were explained by density.     

Importance of woody materials for seasonal variation in leaf area index from optical methods in a deciduous needleleaf forest

Woody materials (woody area index, WAI) is a key error source in estimating leaf area index (LAI) by optical methods, but how to correct the error caused by WAI during different seasons has not reached consensus. In this study, effective plant area index (PAI_e) was first estimated using two indirect optical methods (digital hemispherical photography, DHP, and LAI-2000) in a deciduous needleleaf forest, and then four different schemes for correcting the contribution of WAI to PAI_e were tested here. We also directly estimated the seasonality of LAI by a litter collection method and an allometric method. Directly subtracting WAI from PAI resulted in a greater degree of uncertainty in correcting seasonal changes of PAI_e from both DHP and LAI-2000. Therefore, we introduced a new correction factor, the stem-to-total area ratio, which was reasonable and useful for quantifying seasonal changes in the contribution of WAI to PAI_e. We finally recommend a practical scheme for correcting PAI_e from both DHP and LAI-2000, with accuracies as high as 88% and 87% during most growing seasons, respectively. Additionally, LAI values estimated from allometry were concordant with those estimated from litter collection, indicating that the allometry method is useful for tracking seasonal changes in LAI.     

乔木柳无性系木材基本朱内变异的研究

利用乔木柳12年生无性系对比试验林的材料，研究了13个柳树无性系木材基本密度株内径向和纵向的变异模式，并对密度选择的时期和取样位置进行了探讨。结果表明：（1）在1.3m高度，乔木柳无性系各年轮组木材戏向变异多数为“M”型曲线，即从木芯向外第、至第3年轮组（1－6a）的木材密度逐渐增加，第4年轮组（7－8a）略有下降，第5年轮组（9－10a）又有明显增加，至最外侧年轮（11－12a）木材密度则显著下降，根据各无性系的变异特点，分成3种类型，其中无性系221的变异较为独特，为典型的“N”型；（2）乔木柳无性系生长期密度变化的规律为：1－2年生时木材基本密度相对较低，3－4a以后密度相对稳定并接近无性系加权平均密度，3－4年生时木材基本密度与5－12年生时的测定值相关系数为0.789－0.985，均达到极显著相关水平（α＝0.01），5－12年生乔木柳无性系木材基本密度的变异为62.2％－97.0％与3－4年生时木材基本密度的值有关，3－4a作为5百木柳木材基本密度的选择年龄最为合适；（3）供试群体木材密度株内纵向变异模式大多也可用“M”型曲线加以描述，具典型的苴孔材绷向密度变异特征，根据各无性系的变异特点，分成4种变异类型；树干高1.3，3.6和7.2m处的木材基本密度与无性系平均密度的相关系数达到显著和极显著水平，可以在树干1.3m处取样以推测无性系平均值；（4）在供试群体中，有的无性系木材基本密度纵向和径向变异的幅度均很小，木材较为均一，如苏柳791，表明在乔木柳杂种后代中选择木材均一的柳树新品种是可能的。     

Radial variation of wood density components and ring width in cork oak trees

The radial variation of ring width and wood density was studied in cork oaks (Quercus suber) using microdensitometry. The observations were made in young never debarked cork oaks (30–40 years of age) and in mature trees under cork production (37–60 years of age). The cork oak wood is very dense (mean ring density 0.86 g.cm^?3, between 0.79 g.cm^?3 and 0.97 g.cm^?3) with a small intra-ring variability (mean earlywood density 0.80 g.cm^?3 and latewood density 0.90 g.cm^?3). The density components decreased from pith to bark more rapidly until the 15th ring, and then only slightly. There were no significant differences in the mean density components between never debarked trees and trees under cork production but their outwards decrease was accentuated in the never debarked trees. The annual growth was high, with a ring width mean of 3.9 mm (4.2 mm in the first 30 years) and the latewood represented 57% of the annual growth.     

杉木成熟林土壤容重空间变异特征

为探明土壤容重空间变异特征及其采样间距,以杉木成熟林为研究对象,选取100 m×100 m区域,利用网格法(10 m×10 m)设置样地共计100个,采用经典统计学与地统计学方法分析研究区内不同土壤深度(0~20、20~40 cm)土壤容重的空间异质性,并进行再采样探寻该尺度下最佳采样间距及采样数,旨在减少土壤容重采样人力和物力的消耗。结果表明:土壤容重及其变异系数随土层增加而增加,中等变异,0~20、20~40 cm最佳模型分别为指数模型、球状模型,空间分布呈斑块状,属中等空间自相关;采样间距增大会导致采样数呈"减小-稳定-极限"的变化趋势,变异系数变化虽不大,却能获得更为真实的土壤容重变异系数,20 m×20 m采样间距以下空间自相关性变化程度、拟合效果、块金值等参数较好,小尺度(100 m×100 m)空间变异分析时,采样间距20 m×20 m、采样点布设25个,既能满足Kriging插值精度,又能节省人力和物力。     

Leaf area index estimated by direct,semi-direct,and indirect methods in European beech and sycamore maple stands

Leaf area index(LAI)is one of the most important characteristics of forest stands that affects the fundamentals of tree physiological processes,biomass production,and mechanical stability.The LAI results obtained by the semi-direct and indirect methods(the needle technique and an LAI-2000 PCA)in three European beech(Fagus sylvatica L.)stands and one sycamore maple(Acer pseudoplatanus L.)stand were compared with LAI estimated by litter traps during the 2013 growing season.Seasonal LAI was estimated using an LAI-2000 PCA which showed similar trends among the stands and strongly corresponded to phenological phases of deciduous stands in Europe,with the fastest rate of leaf area increment occurring during the first month following bud break.During the growing season,maximum stand LAI value was on June 19th and reached 4.5–5.1,and 4.0 in the beech and maple stands,respectively.The needle technique significantly underestimated(p<0.05)direct LAI on average by 22.0% and 40.0% in the beech and maple stands,respectively.The LAI-2000 PCA insignificantly underestimated(p>05)LAI on average by 15.1%and 5.8%in the beech and maple stands,respectively.All methods for LAI estimation at the stand level could be applicable in deciduous forest stands(beech,maple)with similar site and stand characteristics.However,calibration by direct method is necessary to obtain the required precision.     

Vertical distribution of fine root density, length density, area index and mean diameter in a Quercus ilex forest

We used minirhizotrons to determine the vertical distribution of fine roots in a holm oak (Quercus ilex L.) forest in a typical Mediterranean area over a 3-year period (June 1994-March 1997). We measured fine root density (number of roots per unit area), fine root length density (length of roots per unit area), fine root area index (area of roots per unit area) and fine root mean diameter. Variables were pooled for each 10-cm depth interval to a depth of 60 cm. Fine roots tended to decrease with increasing depth except between 0 and 10 cm, where the values of all fine root variables were less than in the 10-cm stratum below. Fine root vertical distribution was compared with soil water content and soil temperature at different depths in the soil profile.     

Effects of semi-isostatic densification of wood on the variation in strength properties with density

The variation in strength properties with density was compared between semi-isostatically densified and non-densified wood. Strength properties were compared with published data from earlier studies using other methods for densification. Small clear specimens of eight species were analysed for compression strength in axial, radial and tangential direction, three-point bending and Brinell hardness. After densification, all tested strength properties increased with density, but especially strength perpendicular to grain became lower than expected from the density of non-densified wood. Strength of densified wood relative to what could be expected for non-densified wood of similar density was denoted as ‘strength potential index’. For axial compression strength and bending strength, strength potential index of individual wood species varied between 0.7 and 1.0, i.e. densified wood is slightly weaker than what could be expected from its density. Strength potential index was lower for properties much determined by strength perpendicular to grain. In radial direction, densified wood was rubbery with low modulus of elasticity and nearly no proportional limit or modulus of rupture. Generally, wood was apparently weakened in proportion to the degree of compression in respective direction. Strength potential index also increased with increasing original density of the species.     

A stand density index for complex mixed species forests in the northeastern United States

Quantifying stand density is important for accurate prediction of net biomass and carbon accumulation, for estimating growth and mortality risks of trees, stands, and regions, and for the management of forests for multiple goods and services. Building on previous work relating maximum stand density to wood specific gravity, we develop a stand density equation for the mixed species forests of the northeastern United States using data from the US Forest Service, Forest Inventory and Analysis program. We used quantile regression, in concert with a quantile selection and evaluation procedure, to ensure conformity between our density measure and previously developed guidance for well-studied stand types. The resulting strictly additive relative density measure appears to provide reasonable prediction of maximum density even for plantations of exotic conifers in the region. The results suggest that maximum stand densities after accounting for wood specific gravity may be lower in northeastern North America than in the south or west.