An empirical approach to the analysis of forest stratification

Natural forest communities are made up of different overlapping elementary subpopulations consisting of individuals of different species and ages. To stratify the individuals of a forest stand into elementary subpopulations by using tree height records, a graphical method was empirically proposed employing a derivative of Pearson's type VII distribution as a basis. Arranging all of the individual trees in a stand in the descending order of their height (x), and introducing the rank (N) of any individual in the ordered ranking ofx, finite difference (n) ofN and three values ofx, i.e.,x(N), x(N−n), andx(N+n) labelled byN, N−n, andN+n, respectively, the proposed method used the linear relation betweenx(N) and [x(N−n)+x(N+n)]. On thex(N) vs.[x(N−n)+x(N+n)] diagram, the relation between both the variables could be approximated by a few segmental linear relations and used for stratifying the individuals of a forest stand into subpopulations. The method was applied for analyzing the vertical stratification in forest stands of different forest formations in Japan, Southeast Asia, Africa, and South America. The conclusions on stratification which resulted from the proposed method corresponded well to the conclusions on stratification from profile diagrams.     

Effects of disturbance and size structure on the regeneration process in a sub-boreal coniferous forest,northern Japan

The stand structure and disturbance history in a sub-boreal coniferous forest dominated byPicea jezoensis, Picea glehnii andAbies sachalinensis were investigated in four study plots set up in Taisetsuzan National Park, Japan. The effect of stand characteristics on the growth and mortality rates of understory trees was examined. Although all the stands showed inverse J-shape d.b.h. (diameter at breast height) distributions, the age structure and disturbance history differed amongst the stands. The stands with wide d.b.h. distribution (i.e. large CV and skewness) were more uneven-aged than those with narrow d.b.h. distribution (i.e. small CV and skewness). The disturbance-return interval based on the model of Hett and Loucks was 31 to 65 years. The gap ratio in the canopy was also different among the stands. These suggest that the variations in stand structure represent different occurrences of natural disturbances. Furthermore, the structural features such as size structure, canopy gap ratio and density of canopy trees also affected the growth dynamics of understory trees (≥2 m in height and <10 cm in diameter at breast height). The growth and mortality rates of understory trees changed with the canopy gap ratio and canopy tree density. The understory trees of stands with wide canopy d.b.h. distribution had higher growth and canopy recruitment rates than those of stands with narrow canopy d.b.h. distribution, contributing to the maintenance of continuous stand stratification. The understory trees of stands with narrow canopy d.b.h. distribution showed lower growth and higher mortality rates than those of stands with narrow canopy d.b.h. distribution, leading to the formation of a single-canopy structure. It is suggested that natural disturbance governs the regeneration process in the future by affecting the growth and mortality patterns of understory trees through the stand structure (size and age structure, canopy tree density, canopy gap ratio).     

黄浦江中上游杨树人工林生态系统碳储量研究

以上海地区黄浦江中上游杨树人工林为研究对象,构建了杨树立木及各器官(根、干、皮、枝、叶)生物量方程,并对杨树人工林林分生物量(乔木层、地表枯落物层)、碳储量和土壤碳储量进行了估测。结果表明:杨树立木及各器官的生物量方程拟合效果较好(R2=0.96～0.99,P0.001)。9年生杨树人工林生态系统碳储量为90.9 t·hm-2。其中乔木层碳储量所占比例为36.6%,乔木层各组分碳储量大小排序为树干树根树枝树皮树叶;地表枯落物层碳储量所占比例仅为1.7%。土壤碳储量(0～50 cm)所占比例最大,为61.6%。这些杨树人工幼龄林正处于快速生长阶段,对上海地区人工林碳汇经营具有重要意义。     

粤东亚热带森林群落树种组成对苔藓植物分布的影响

为探究森林群落树种组成对苔藓植物分布的影响,利用多元统计方法研究粤东亚热带地区苔藓植物的组成和分布对林分类型的响应。根据森林乔木层的树种组成划分为翻白叶树(Pterospermum heterophyllum)、木荷(Schima superba)+米锥(Castanopsis carlesii)和米锥3种森林类型。结果表明,3种森林类型中苔类(liverworts)和藓类(mosses)植物群落组成特征总体上存在显著差异;双齿裂萼苔(Chiloscyphus latifolius)和细指苔(Kurzia gonyotricha)在3种类型林分中的重要值变化指示了苔类植物群落的差异。3种类型林分中,均以东亚拟鳞叶藓(Pseudotaxiphyllum pohliaecarpum)为优势种。不同林分中藓类植物种类组成主要表现为亚优种分布的不同。这表明森林群落树种组成作为重要的生物因子,对林内苔藓植物的分布和种类组成有重要影响。     

Density effect, self-thinning and size distribution in Pinus densiflora Sieb. et Zucc. stands

The competition-density (C-D) effect for given times and self-thinning over time in even-aged, natural, pure stands of Pinus densiflora Sieb. et Zucc. were analyzed with the reciprocal equation of the C-D effect in self-thinning stands, and the equation describing the time-trajectory of mean stem volume and stand density. The C-D effect and self-thinning were consistently well explained by the two equations. Differences in mean stem volume and in stand density among the stands tended to merge with increasing stand age. The self-thinning line with a slope of approximately –3/2 was reached by the higher density stand prior to the medium and lower density stands. The skewness of tree height distribution showed positive values, which means that the distribution is more or less L-shaped, and in addition the skewness decreased with increasing mean tree height, which indicates that smaller trees died as the stands grew. This trend is consistent with the asymmetric (one-sided) competition hypothesis that self-thinning is driven by competition for light. The tree height distribution was analyzed using the Weibull distribution. The location parameter h _min of the Weibull distribution increased with increasing stand age, and the scale parameter a tended to increase slightly with increasing stand age. The range of the shape parameter b of the Weibull distribution corresponded to that of the skewness.     

Community dynamics of evergreen broadleaf forests in southwestern Japan

The process and rate of revegetation in gaps in an evergreen oak forest were studied by comparing the species composition, tree density, frequency distribution of tree height, and relation between diameter at breast height and tree height among different aged stands. For estimating stand ages, the ages of gap indicators, such as,Symplocos prunifolia andAcer rufinerve, were very useful. It took about 70 years for gaps to be filled by large fully-grown trees. Since the mean residence time of the forest canopy was 180 years, the trees that attain the forest canopy were expected to be canopy trees for 110 years on the average. Tree densities of all broadleaved evergreens exceptS. prunifolia, were independent of stand age. On the other hand, densities of gap indicators,S. prunifolia andA. rufinerve, decreased as stand age increased. Other deciduous broadleaf and coniferous species were scarce as a whole. According to the frequency distributions of height of live and dead trees in different aged stands, it was suggested that shorter trees were more susceptible to death than taller trees. The self-thinning in revegetation process in gaps approximately followed the 3/2 power law, though the power was larger (−1.32) than expected from the law.     

A Simple model of the leaf daily water potential dynamics of some forest tree species

A simple model was developed to characterize the daily water potential dynamics (Ψ_x of sun and shade leaves of three forest tree species (Quercus cerris, Acer campestre andCarpinus betulus) under anticyclonic weather types. Input data used for this-model were the vapour pressure deficit (d) and the soil moisture content (w.). The model is usable for the calculation of the actual Ψ_x-values with a probable error 0.18 –0.28 MPa and limits the maximum and minimum Ψ_x-values which may occur with the particular tree species. The model makes it possible to establish for each species the regime, determined byd andw, at which the water potential of the leaves reacts most sensitively to the changes of the environmental parameters.     

Unusual Fine Root Distributions of Two Deciduous Tree Species in Southern France: What Consequences for Modelling of Tree Root Dynamics?

The spatial distribution of fine roots of two deciduous tree species was investigated in contrasting growing conditions in southern France. Hybrid walnut trees (Juglans regia×nigra cv. NG23) and hybrid poplars (Populus euramericana cv. I214) were both cultivated with or without annual winter intercrops for 10 years on deep alluvial soils. Soil samples for measuring the fine root distribution of both trees and crops were obtained by soil coring down to 3-m depth at several distances and orientations from the tree trunk. The distribution of live fine roots from walnut and poplar trees was patchy and sometimes unexpected. In the tree-only stands, fine root profiles followed the expected pattern, as fine root density decreased with increasing depth and distance from the tree trunk. However, many fine root profiles under intercropped trees were uniform with depth, and some inverse profiles were observed. These distributions may result from a high degree of plasticity of tree root systems to sense and adapt to fluctuating and heterogeneous soil conditions. The distortion of the tree root system was more pronounced for the walnut trees that only partially explored the soil volume: in the tree-only stand, the walnut rooting pattern was very superficial, but in the intercropped stand walnut trees developed a deep and dense fine root network below the crop rooting zone. The larger poplars explored the whole available soil volume, but the intercrop significantly displaced the root density from the topsoil to layers below 1 m depth. Most tree root growth models assume a decreasing fine root density with depth and distance from the tree stem. These models would not predict correctly tree–tree and tree–understorey competition for water and nutrients in 3D heterogeneous soil conditions that prevail under low-density tree stands. To account for the integrated response of tree root systems to such transient gradients in soils, we need a dynamic model that would allow for both genotypic plasticity and transient environmental local soil conditions.     

Patterns of Trunk Diameter, Tree Height and Crown Depth in Crowded Abies Stands

The size structure of trees in crowded, even-aged Abies (fir)stands of ‘Shimagare’ or ‘wave-regenerated’sub-alpine forests is analyzed. Tree-height distributions showconsistently smaller variation and less positive skewness thanthe distributions of trunk diameter and crown depth (tree heightminus height of the lowest branch). This difference is associatedwith changes in the relationships between trunk diameter, treeheight and crown depth as stands age. These, in turn, resultfrom self-pruning of the lower foliage crown due to competitionfor light in crowded stands. Abies, diameter-height curve, competition, size distribution, stand development, tree geometry, wave-regeneration     

Clustered root distribution in mature stands of <Emphasis Type="Italic">Fagus sylvatica</Emphasis> and <Emphasis Type="Italic">Picea abies</Emphasis>

Distribution of small roots (diameter between 2 mm and 5 mm) was studied in 19 pits with a total of 72 m² trench profile walls in pure stands of Fagus sylvatica and Picea abies. Root positions within the walls were marked and transformed into x-coordinates and y-coordinates. In a GIS-based evaluation, zones of potential influence around each root were calculated. The total potential influence produced isoline maps of relative root influence zones, thus indicating small root clustering. The questions studied were (1) whether there were marked clusters of small roots in the soil and (2) whether trees surrounding the pit (defined as tree density) correlate with the root abundance and distribution on the trench profile walls. Small roots of both species showed maximum abundance in the top 20 cm of the soil, where pronounced root clusters occurred next to areas with only low root accumulation. The area of root clusters did not differ significantly between the two stands. Weighted clumping, WC, calculated as a product of root class, and its area was used as an index of root clustering, which again did not differ between beech and spruce stands. However, evaluations on a single root level showed that beech achieved the same degree of clustering with lower number of roots. Regardless of soil properties related to root clusters, a significantly higher clustering acquired per root for beech than for spruce suggests beech to be more efficient in belowground acquisition of space. Because none of the parameters describing root clustering were correlated with tree density around the investigated soil profiles, clusters of small roots are inherently present within the tree stands.     

Tree shape plasticity in relation to crown exposure

Trees outside closed forest stands differ in the relation between stem diameter, height and crown volume from trees that grew with neighbours close by. Whether this plasticity in tree shape varies between species in relation to their light requirement is unknown. We purposefully sampled 528 trees ranging 5–100?cm diameter at breast height growing in a range of light conditions. Across ten broad-leaved species observed in Sumatra or Kalimantan, a generic relationship was found between light exposure of the crown and a light-dependent a _l parameter that modifies the height–diameter allometric equation (H?=?a _l D ^b ) from those for closed stands. In our results, vertical stretching is well predicted by light availability. In fully open conditions, trees are on average 31% shorter for the same diameter than under (partial) shade. Most of the stretching response occurs in all species as soon as some degree of lateral shading occurs. The response, however, varies by species (8–44% reduction) in a way apparently unrelated to species’ successional status. Crown volume varied less than stem height in its relationship with stem diameter across all light conditions tested. The scaling of crown volume with stem diameter, however, differed markedly between tree species.     

华南地区常见树种导管特征与树干液流的关系

为探讨树木结构与功能的关系,对华南地区常见8种树木边材的导管特征进行观察,并利用Granier热扩散探针法测量干、湿季树干的液流密度,分析导管特征与树干液流的关系。结果表明,除红锥(Castanopsis hystrix)有两种导管外,大叶相思(Acacia auriculaeformis)、荷木(Schima superba)、火力楠(Michelia macclurei)、藜蒴(C.fissa)、马占相思(A.mangium)、柠檬桉(Eucalyptus citriodora)、尾巨桉(E.urophylla×E.grandis)的导管类型单一。导管特征在种间存在明显差异,且导管长度、密度和孔径之间存在明显相关性,它们与标准化的边材面积呈现显著相关。湿季液流最大值与导管特征无明显相关性,但整树最大蒸腾速率与导管特征呈显著相关;树木的日蒸腾量与导管特征也有明显相关性。因此,树木的液流速率并不受树干的导管影响;而树干的导管孔径与边材面积间的负相关权衡机制,可以降低树种间由于导管孔径差异引起的树干的水分输送速率的差异性。     

Stand dynamics during a 12-year period in a second-growth stand in a cool temperature forest in northern Japan

In 1981 and 1993, trees over 2 m high were measured and mapped to clarify stand dynamics in two permanent plots of 0.1 ha in a secondary, cool temperate, mixed broadleaf/conifer forest after logging in the Tomakomai Experiment Forest, central Hokkaido, northern Japan. The species could be placed in two groups according to the change in basal area and density, and annual height growth:Quercus mongolica var.grosseserrata, Phellodendron amurense, Prunus sargentii andTilia japonica (Group I: GI) showed episodic regeneration and/or fast height growth;Acer mono, Acer palmatum var.matsumuae andSorbus alnifolia (Group II: GII) showed continuous regeneration and/or slow height growth. The age distribution of stems over 10 cm in d.b.h. suggests synchronous regeneration of GI and GII species. Vertical stratification was promoted during the 12-year period by the difference in annual height growth between the two species groups. Additional tree censuses in both remnant old-growth stands and second-growth stands after large scale blowdowns demonstrated thatQ. mongolica var.grosseserrata is most dominant in stands varying in the stages of development. Disturbance history and successional trends in dominant species implied that stand-devastating disturbances were responsible for the regeneration ofQ. mongolica var.grosseserrata in the study forest.     

Stand structure and carbon metabolism of coppice forests at a heavy snowfall climate region of central Japan. I. Dynamics of stand structure during 14 years

The coppice stands under the climatic conditions of Warmth Index (WI)≧85°C·month, and Coldness Index (CI)≦−10°C·month could be classified into aQuercus serrata type andCarpinus types at a heavy snowfall climate region of central Japan. The latter types tended to be more distributed on steeper slopes rather than the former. An analysis of tree forms and growth rates of species could reveal the characteristic of this habitat and vegetation type. The growth rates of stem diameter of dominant species on a gentle slope were higher than ones on a steep slope. However, the dominant species on the steeper slope had plasticity to basal bend with sustentacular roots, which is one form of tolerance of heavy snowfall on steep slopes. Average mortality during 14 years was 26%, irrespective of the gradient of a slope. More than one-third of dead shoots were induced by direct damage, while cracked or broken pieces of a stem were from heavy snowfall. The shoot density at smaller diameter classes tended to be higher at a stand having high horizontal variance of canopy surface caused by basal bend of big shoots. A frequency distribution function of individual tree weight (w), f(w)=pw^−3/2, could be obtained at each coppice stand by statistical analysis. The value of a parameter p, a packing factor, tended to be higher at stands on steeper slopes consisting of largely bent shoots and was constant irrespective of the growth.     

A power function for forest structure and regeneration pattern of pioneer and climax species in patch mosaic forests

The DBH-class distribution in natural deciduous broad-leaved forests was elucidated with a power function. A power function (y=ax ^b, y: stem density, x: represents DBH class, a and b: constants) fits the distribution better than an exponential function (y = a exp bx). The parameter b in the power function is approximately –2. This means that the natural forests studied have a patch-mosaic structure and that tree cohorts regenerate from gaps. Parameter a implies the number of juveniles, and b means size-dependent mortality. The value of –2 for parameter b means that when trees in a given DBH class double their DBH, the density of the size class should decrease by one-fourth. This phenomenon results from self-thinning and is caused by horizontal space competition among trees, called the `tile model'. The parameter describing DBH-class distribution for a forest with self-thinning patches should be approximately –2. I call this the `–2 power law' for DBH-class distribution. In a typical natural forest dominated by deciduous broadleaf tree species, trees are recognized as pioneer or climax species by the parameters describing their regeneration patterns. When I applied the power functional model to the DBH-class distribution of each dominant species, in pioneer species parameter a was high and b was less than –2 (markedly less than zero), suggesting that there are many juveniles, but mortality is high. On the other hand, in climax species parameter a was low value and the value of b was larger (negative, but closer to zero), suggesting that there are not many juveniles, but mortality is low. A power-function analysis of DBH-class distribution can be used to clarify the patch mosaic structure of a forest, and to clarify the regeneration pattern of pioneer and climax species by applying the function for each species.     

The spatial distribution of beetles within the canopies of oak trees in Richmond Park, U.K.

1. 5054 adult beetles of 144 species were collected in a total of 696 1‐m² collecting trays by knockdown insecticide fogging of 36 different oak trees in closed canopy woodland at Richmond Park, U.K., with three of the trees sampled on each of 12 dates, at 2‐ to 3‐week intervals, between April and October 1984. 2. In late spring (April/May), more individuals and species of beetles were collected in trays close to the trunks of trees than in trays more distant from the trunk. The reverse was the case in late September/October. Neither pattern prevailed in the intervening months. 3. Individual species exhibited a variety of patterns, with some species more abundant near the trunk, e.g. Leiopus nebulosus (L.), Strophosoma melanogrammum (Forster), Cylindronotus laevioctostriatus (Goeze), and Dromius agilis (Fabricius), and some less abundant near the trunk, e.g. Curculio pyrrhoceras (Marsham) and Rhynchaenus signifer (Creutzer). For Adalia decempunctata (L.), this preference changed with season. The observed species preferences for parts of a tree crown near or distant from the main trunk are discussed with reference to their known biologies. 4. No pronounced pattern of preference for north‐ or south‐facing aspects of trees in closed canopy woodland was observed, however populations of some species exhibited patterns of within‐tree distribution that correlate with compass angle; for one species, the ladybird Adalia decempunctata, this distribution changed with season and between colour morphs.     

Spatial distribution of saproxylic beetles on trunks of standing Scots pine trees

1. The spatial distribution of saproxylic beetles landing and climbing stems of 12 grown and healthy Scots pine trees (Pinus sylvestris L.) was examined in detail during a 3-year trial. The beetles were sampled using sticky traps attached to the tree trunk at three tree parts (i.e., the trunk base, middle part of the trunk, and trunk in crown). Each tree part was sampled using two sticky traps facing opposite cardinal directions (north and south).
2. In total, 4063 individuals representing 169 taxa of saproxylic beetles were yielded in the 1405 obtained samples.
3. Remarkable interstrata diversification of saproxylic beetle assemblages reflecting distribution of breeding substrates in the forest stand was observed. Overall, species richness decreased considerably from the trunk base to the crown, with intermediate values for the middle part of the trunk. However, the abundance of mycetophages and saproxylophages decreased from the trunk base to the crown, with xylophages being the most abundant in the tree crown.
4. The cardinal direction exhibited overall weak effects on abundance, species richness, and composition, but the occurrence of a few particular species was significantly associated with the south (13 species) or north (3 species) facing part of the trunk.
5. Our results suggest that primary attraction and random landing strategies are combined during the substrate selection by many species.
6. High variability in the importance of the studied explanatory variables was observed among taxa, which shows how the species composition recorded in any study might alter its general outcomes.

     

Comparative Growth Behaviour and Leaf Nutrient Status of Native Trees Planted on Mine Spoil With and Without Nutrient Amendment

The effect of nutrient amendment on growth of nine indigenoustree species planted on coal mine spoil was studied. Greatergrowth in fertilized plots was accompanied by greater foliarN and P concentrations in all species. The response to fertilizationvaried among species and was greater in non-leguminous thanin leguminous species. Furthermore, leguminous species exhibitedhigher growth rates compared to non-leguminous species. Thelog-transformed height-diameter relationships were significantfor all tree species and treatments. Acacia catechu, Dalbergiasissoo, Gmelina arborea and Azadirachta indica fitted the elasticsimilarity model of tree growth; whereas Pongamia pinnata andPhyllanthus emblica followed the constant stress model. Tectonagrandis was the only species which fitted the geometric similaritymodel. In Albizia lebbeck and Terminalia bellirica, the b -values(the gradients of the log-transformed height to diameter relationships)were considerably lower (<0.5), and these two species didnot fit any model of tree growth. In several cases, the b -valueswere considerably influenced by nutrient amendment. The log-transformedcrown mass and trunk mass relationships were significant forall treatments and species. The slope of the crown mass:trunkmass relationship was near unity in A. indica, D. sissoo, G.arborea, P. emblica, P. pinnata, T. grandis, and T. bellirica.However, in A. catechu and A. lebbeck, this slope was well belowunity suggesting a greater allocation to non-photosynthetictissue. Fertilizer amendment resulted in a heavier crown relativeto trunk in A. indica, T. grandis and T. bellirica. Copyright2001 Annals of Botany Company Diameter increment, fertilizer application, foliar N, foliar P, height increment, tree growth, volume increment     

Vertical distribution of Hymenophyllaceae species among host tree microhabitats in a temperate rain forest in Southern Chile

Question: Are differences in microhabitat preferences of co‐occurring epiphytic Hymenophyllaceae species (filmy ferns) correlated with differences in ecophysiological responses to light availability and humidity in the host tree? Location: The Andean foothills in south‐central Chile. Methods: We evaluated the distribution pattern of nine filmy fern species in microhabitats that differ in light availability and humidity in four host tree species. A DCA was developed to assess Hymenophyllaceae species microhabitat preference in terms of canopy openness (CO) and relative humidity. We assessed whether differences in chlorophyll content, maximum photochemical efficiency (Fv/Fm), photosynthetic capacity (A_max), evapotranspiration (E) and instantaneous water use efficiency (WUE) are consistent with any pattern. Results: CO and relative humidity differed significantly with height in the host trees. While CO increased with height in a host tree, relative humidity decreased. DCA analysis showed that filmy fern species distribution within and among trees was mainly explained by the relative humidity of the microhabitat. Chlorophyll content, chlorophyll a/b ratio, A_max and E differed significantly among filmy fern species. A_max and E were correlated with axis 1 scores from the DCA analysis. Conclusions: The vertical distribution and abundance of filmy fern species in Chilean temperate rain forest seems to be closely related to the different microhabitats offered by host trees. This pattern may reflect interspecific differences in ecophysiological traits related both to light availability and humidity. Our results suggest that humidity is the main environmental factor driving functional responses and habitat preferences of these filmy fern species.     

Structure of Anogeissus leiocarpa Guill., Perr. natural stands in relation to anthropogenic pressure within Wari‐Maro Forest Reserve in Benin

The present study focused on the analysis of the structure of the Anogeissus leiocarpa dominated natural stands in the Wari‐Maro forest reserve which are under high and minimal anthropogenic pressures. These stands were considered for forest inventories after carrying out a random sampling scheme of 40 sample units of 30 m × 50 m. In each level pressure stand, the dbh and tree‐height of identified tree‐species were measured in each plot. Data analyses were based on the computation of structural parameters, establishment of diameter and height distributions and the floristic composition of the two types of stands. Results obtained showed higher values for the overall basal area (9.78 m² ha^?1), mean height (22.37 m) and mean diameter (36.92 cm) for A. leiocarpa in low‐pressure stands. In high‐pressure stands, some species like Afzelia africana had lower Importance Value Index and the frequency of A. leiocarpa trees in the successive diameter classes dropped rapidly and the value of the logarithmic slope of the height–diameter relationship was lower (9.77) indicating a lanky shape. Results obtained suggest that effective conservation is needed for A. leiocarpa stands under high pressure by limiting human interference and developing appropriate strategy for restoration purposes.