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1.
Five contrasting deciduous forest stands were studied to characterize the spatial structural variability in human-influenced forests. These stands are representative of cultural forest types widely represented in western Europe: one plantation, two coppices, one wood-pasture forest and one high forest stand. All stems with DBH > 5 cm were measured and mapped, and stem DBH distributions, spatial structure of DBH, spatial point patterns and spatial associations were analysed. Spatial autocorrelation for DBH was calculated with Moran’s I correlograms and semivariograms. Complete spatial randomness hypothesis for spatial point patterns, and both independence and random labelling hypotheses for spatial associations were analysed using Ripley’s K function. The results showed that tree sizes were conditioned by particular former management systems, which determined unimodal symmetric, positively skewed or compound DBH distributions. Spatial structure was more complex when human influence became reduced. Coppice stands showed clumped spatial patterns and independence among size classes, as a consequence of sexual and vegetative establishment of new stems in open areas. The largest clumping intensity was observed in the wood-pasture with an intermediate disturbance frequency and low inter-tree competition. The high forest stand displayed spatial traits consistent with the gap-dynamics paradigm, such as clumping of smaller trees, random arrangement of larger trees, negative association between juveniles and adults, and high structural heterogeneity. It can be expected that after cessation of human interference, coppices and wood-pastures would evolve to a more heterogeneous structure, probably with a higher habitat and species diversity.  相似文献   

2.
The widespread European forest tree Fagus sylvatica L. is of great importance for forest management. However, information about seed dispersal is still very rare, though important for harvesting strategies and later on seed source identification. We refined a DNA fingerprinting method for beech nut shells in order to directly assign dispersed seeds to their mother trees. A pilot study was conducted in two beech stands in Germany where leaves of the adult trees and the exocarp of dispersed seeds were fingerprinted at six nSSR loci. While one stand was randomly analysed for adults and dispersed seeds the other was systematically investigated following common harvesting procedures. Imitating the typical net harvesting strategy, seeds were collected beneath 19 adult trees. Exocarp genotyping revealed that on average three different mother trees contributed to a sample of five or six seeds collected beneath a single adult tree. Of the identified mother trees most were located within a radius of 15 m from the sampling point. The repeated pattern of seed dispersal within a short distance constitutes the basis for a straightforward strategy for the assignment of seed lots to a seed source stand. This strategy is based on the matching of individual genotypes without the necessity for a full inventory of the putative source stand. Additionally, we provide allelic ladders of five nSSR loci for standardization among laboratories.  相似文献   

3.
Spatial structure of genetic variation within populations of forest trees   总被引：1，自引：0，他引：1  
B. K. Epperson 《New Forests》1992,6(1-4):257-278
The spatial pattern and structure of genetic variation are important aspects of the population genetics of forest stands. Combined with limits to seed and pollen dispersal, spatial structure affects the level of inbreeding and the action of natural selection. The genetic constitution of stand regeneration, following different forestry practices, is also influenced by spatial structure. For example, natural regeneration with seed trees involves sampling seed trees from a stand that may be genetically nonhomogeneous. This paper reviews theoretical and empirical results on spatial patterns of genetic variation, produced under limited gene flow and selection, in terms of recently developed spatial statistics (e.g., spatial autocorrelation). Genetic correlations in samples from spatially structured populations are also described, as well as how spatial samples can be used to characterize the structure of genetic variation, and how inferences can be made about (spatially distributed) components of fitness and yield.  相似文献   

4.
On the basis of nine Norway spruce (Picea abies (L.) Karst.) and ten European beech (Fagus sylvatica L.) thinning experiments in Germany, for which both residual and removed stock had been registered first during 1870, I scrutinize how moderate and heavy thinning from below (B-, C-grade) affects the production of merchantable volume compared with light thinning (A-grade). In relation to A-grade, cumulative merchantable volume (CV) of B- and C-grade amounts in average to 103–107% in juvenile and to 97–102% in mature Norway spruce stands. The corresponding findings for European beech are 101–106% and 94–102%. CV of individual stands varies between 89% and 130% for Norway spruce and 73% and 155% for European beech (CV of A-grade = 100%). These findings are substantiated by the relation between stand density (SDI) and periodic annual increment (PAI). On the B- and C-grade plots of spruce and beech, respectively, SDI was reduced down to 41–91% and 31–83% of the A-grade. When SDI is reduced in young stands, PAI follows a unimodal curve. Norway spruce’s PAI culminates in 109% if SDI is reduced to 59%; European beech’s PAI culminates in 123% when density is reduced to 50%. Whereas Norway spruce’s growth reacts most positively on thinning under poor site conditions and with increment reduction on favourable sites, European beech behaves oppositely. With stand development the culmination point of the unimodal relation moves towards maximum density, so that in older stands PAI follows the increasing pattern, which is the left portion of a unimodal curve. A model is presented which apparently unifies contradictory patterns of stand density–growth reactions by integrating relative stand density, average tree size and site fertility effects, and makes the findings operable for forest management.  相似文献   

5.
For the demands of automatic pruning, an effective discrimination rule of the forked and non-forked larch trees is established. First, information of trunk and branch diameters of a larch plantations was collected from the west mountain of Beijing. The growth characteristics of the forked and non-forked trees were studied. Given the statistical characteristics of the trunk and branch diameters, a discriminant function of the forked branch and non-forked larch trees was established statistically. Excellent discrimination results were obtained by the function and the rule. The study presents an effective discrimination rule to separate forked trees from straight trees for automatic pruning.  相似文献   

6.
R. Perrin 《Forest Pathology》1984,14(6):321-325
Variability of Fagus sylvatica susceptibility to Nectria coccinca, one of the agents of beech bark disease . N. coccinea was inoculated into wounds of young beeches raised from seeds of 6 bark diseased trees and 6 healthy ones in the same stand of the forest of Lyons. Classifieation of the progenies, according to the size of the necrosis, is in good agreement with the health of the mother trees. N. coccinca susceptibility of beech has a genetic origin.  相似文献   

7.
The basal area and height growth of trees and saplings in silver fir–European beech single stem selection forest were studied with regard to their social status and crown parameters of size, coverage, shading and vitality. On 24 permanent research plots (20 m × 20 m each) all trees [diameter at breast height (dbh) ≥10 cm] and saplings (≥1.3 m tall and dbh <10 cm) were surveyed. Repeated measurements of dbh (N = 1,608) and height (N = 1,135) 10 years apart enabled the calculation of annual basal area increment (BAI) of trees and saplings, and annual height (HI) increment of saplings. To obtain the growth characteristics for individual trees and saplings, their social status and crown parameters were assessed by rank. In the multivariate general linear model for BAI, social status, crown size and crown coverage of individuals as the predictors, and dbh2 as the covariate, explained 70% of total variability. Similarly, social status, crown size, crown coverage and crown shading had a significant impact on the HI of saplings, explaining 70% of total variability. Among the observed variables, social status determined according to the individual’s position in vertical stand structure was, in addition to dbh, the most important predictor for both BAI and HI. Significant differences were observed between the BAI and HI models for the main tree species (European beech and silver fir), indicating their different growth characteristics. The applied method could be used as a supplement to the more widely used approaches for studying basal area and height growth of individual trees in selection forest stands.  相似文献   

8.
Oriental Beech is the most important commercial tree species in northern Iran. In recent years wood production companies interested in felling large beech trees for profit have challenged advocates of close-to-nature silviculture who favor conservation. Our study objective was to assess the economic value of over-mature beech trees by relating tree diameter (DBH) to amount of decay. Based on the location of onset of decay, we categorized three types of decay as stump, stem, and crown decay. Trees of greater diameter (age) typically showed greater decay in the stem. Percent of decayed volume, diameter of decayed tissue, and length of decay in tree stems varied between 0.5%?64.3%, 15 cm?75 cm, and 2.0?19.5 m, respectively. With increasing trunk diameter, the proportion of truck decay increased. Red heart and dark red heart constituted 25% and 14.3% of sampled trees, respectively. However, we found no correlation between intensity of stem decay and morphological characteristics of trees. Seedlings were not abundant around the bases of over-mature trees, suggesting that the trees did not contribute to regeneration of the stand. Beech trees of diameter >1 m do not provide valuable round wood for industries and cause to raise wood production costs. We recommend that these trees >1 m DBH should be retained in forest stands because of their low commercial value but high ecological and conservational values such as maintaining biodiversity in forest ecosys-tems.  相似文献   

9.
《林业研究》2021,32(4)
Forest management may have significant effects on forest connectivity and natural population sizes.Harvesting old-growth single trees may also change natural patterns of genetic variation and spatial genetic structure.This study evaluated the impacts of forest management using a silvicultural system of seed trees on the genetic diversity and spatial genetic structure of Eremanthus erythropappus(DC.)MacLeish.A complete survey of 275 trees on four plots was undertaken out to compare the genetic variation of a managed stand with an unmanaged stand.We genotyped all adult and juvenile individuals 60 months after the management and compared the genetic diversity and the spatial genetic structure parameters.Genetic diversity was considered high because of an efficient gene flow between stands.There were no genetic differences between stands and no evidence of inbreeding.Genetic clustering identified a single population(K=1),indicating no genetic differentiation between managed and unmanaged stands.Adult and juvenile individuals of the unmanaged stand were more geographically structured than individuals from the managed one.There was a tendency of coancestry among juveniles at the first class of distance of the managed stand,suggesting a drift of genetic structure possibly caused by management.Understanding early responses to management on genetic diversity and stand structure is a first step to ensuring the effectiveness of conservation practices of tree species.The sustainability of forest management of E.erythropappus on genetic diversity,and more accurately,on spatial genetic structure needs evaluation over time to promote effective conservation of the population size and genetic variability.  相似文献   

10.
The first part of this paper highlights spatial stand structure as the central stand characteristic and introduces methods of pattern identification. This involves two nearest-neighbour methods for the identification of stand structures, i.e., the aggregation index R by Clark and Evans [Clark, Ph.J. and Evans, F.C., 1954. Distance to nearest neighbor as a measure of spatial relationships in populations. Ecology 35 (4) 445–453.] for univariate patterns and the segregation index S by Pielou [Pielou, E.C., 1977. Mathematical Ecology. Wiley.] for bivariate patterns. Both were used to describe the structure of 53 experimental plots of mixed beech-larch stands in Lower Saxony which provided the data base for this investigation. The second part of the study deals with the development of the STRUGEN stand structure generator, designed for the modeling and reproduction of spatial stand structures. To generate stand structures, a two-dimensional homogeneous Poisson process is used as well as a set of two-dimensional distribution functions which determine mixture type and intermingling intensity of main and associated tree species. Moreover, a distance function secures minimum distances between competing neighbouring trees. Consequently, the produced pattern is the result of a combination of an inhomogeneous Poisson process (for generating mixture units) and a hard-core process (for securing minimum distances between neighbours). The STRUGEN generator was designed and successfully used for the investigation of 53 mixed beech-larch stands. It provides initial values and stand structures for distance-dependent single-tree models from estimated qualitative stand characteristics. STRUGEN is a useful tool and allows initial, pragmatic steps towards fully utilising available qualitative and quantitative information to diagnose the state of a forest and to predict its growth.  相似文献   

11.
Oriental beech (Fagus orientalis Lipsky.) and Oriental spruce [Picea orientalis (L.) Link] are the two most common tree species in northeast Turkey. Their distribution, stand type and understorey species are known to be influenced by topographical landforms. However, little information is available as to how these changes affect litter decomposition rates of these two species. Here, we investigated the effects of slope positions (top 1,800 m, middle 1,500 m and bottom 1,200 m), stand type (pure and mixed stands) and purple-flowered rhododendron (Rhododendron ponticum) on litter decomposition rates of Oriental beech and spruce for 4 years using the litterbag technique in the field. Among these three factors, stand type had the strongest influence on litter decomposition (P < 0.001, F = 58.8), followed by rhododendron (P < 0.001, F = 46.8) and slope position (P < 0.05, F = 11.6). Litter decomposition was highest under mixed beech/spruce forest, followed by pure beech and spruce forest. Beech and spruce litter decomposed much faster in mixed bags (beech–spruce) than they did separately under each stand type. Purple-flowered rhododendron significantly reduced litter decomposition of Oriental beech and spruce. Beech and spruce litter decomposed much slower at top slope position than at either bottom or middle position. Differential litter decomposition of Oriental beech and spruce was mainly due to adverse conditions in spruce forest and the presence of rhododendron on the ground which was associated with lower soil pH. Higher elevations (top slope position) slowed down litter decomposition by changing environmental conditions, most probably by decreasing temperature as also other factors are different (pH, precipitation) and no detailed investigations were made to differentiate these factors. The adverse conditions for litter decomposition in spruce forest can be effectively counteracted by admixture of beech to spruce monoculture and by using the clear-cutting method for controlling rhododendron.  相似文献   

12.
The structure of natural subalpine spruce forest in the Zadná Pol’ana massif of the Western Carpathians was analysed. We focused on the variability of different aspects of stand structure, tree decay and regeneration processes in altitudinal gradient. We used systematic sampling, covering an area of 2 km2, to detect even subtle changes in stand structure within one forest type over a range of less than 200 m in elevation. Mean stand density was 290 trees (>7 cm DBH) per hectare, average basal area was 41 m2 ha−1, and the volume accumulation in living trees amounted to 500 m3/ha−1. Stand volume decreased by more than 50% between 1,260 and 1,434 m a.s.l. This means for an increase of altitude of 100 m that stand volume decreased by nearly 200 m3. Neither stand density nor basal area was related to elevation. Maximum tree height was strongly correlated to elevation, and it decreased on average by 6 m for each 100 m increment of altitude. No significant changes in the maximum spruce diameter were recorded in relation to the elevation gradient. Spatial distribution of trees was biased toward regularity at lower altitudes. Tree clustering increased with increasing altitude. The stock of coarse woody debris (CWD) decreased slightly along the altitudinal gradient, but changes were not significant. Density of spruce saplings and their number growing on CWD significantly increased across the elevation gradient. Despite the fact that the analysed forest tract was relatively large, highly variable in respect to environmental factors, and that stand volume, spatial structure, and tree height displayed strong variability along the elevation gradient, the diameter structure of stands and regeneration measures were uniform. Our results suggest that the recruitment of new trees in the Zadná Pol’ana subalpine spruce forest is not temporally continuous even at a scale of several square kilometres.  相似文献   

13.

The anticipated increase in extreme disturbance events due to climate change is likely to expose Norway spruce (Picea abies (L.) Karst.) dominated forests in northern Europe to new conditions. Empirical data on the resilience of such natural (unmanaged) forests to disturbance and the long-term patterns of regeneration in its aftermath are currently scarce. We performed a quantitative assessment of natural forest stands in north–western Latvia to identify and characterise the patterns of stand structure 44 years after a stand-replacing disturbance and investigated the effects of legacies on regeneration. The spatial distribution of tree species and their dimensions were assessed in 71 circular sample plots (500 m2 each) in natural forest areas, where Norway spruce dominated prior to the windthrow and salvage logging was not carried out. Spatial indices (species mingling index, size differentiation index, and aggregation index) were used to characterise stand structure and diversity. The different initial states (age and coverage of surviving trees) of stands affected eventual tree species dominance, size differentiation, degree of mingling and aggregation. Our results demonstrate a close relationship between disturbance legacies and spatial indices. The pre-storm understory and canopy survivors decreased species mingling, whereas survivors increased size differentiation. The size differentiation increased also with a higher degree of species mingling. Leaving differential post-storm legacies untouched promotes a higher structural and species diversity and therefore supports the management approach of preserving canopy survivors.

  相似文献   

14.
In natural plant populations, leaf polyphenols show high intraspecific variation that occurs both temporally and spatially. Leaf phenolics may be induced by diverse ecological factors such as light, nitrogen availability or herbivory attack. Both light and nitrogen availability can show spatial structure in forested stands, meaning that they each have a high degree of autocorrelation, which can determine the appearance of spatial structure in leaf polyphenols. However, the availability of these resources may be drastically changed by forest disturbance, and little is known about the effect of forest disturbance on the spatial pattern and scale of leaf secondary compounds. We hypothesise that the spatial structure of leaf polyphenols in understory vegetation will disappear due to forest harvesting, because these compounds depend on light availability, yet it will remain unaltered for those compounds that either depend on the availability of other resources or are under major genetic control. The study was performed in young pedunculate oak (Quercus robur) populations growing either under a pine canopy (Pinus pinaster) stand or in a pine harvested stand in NW Spain. The spatial structures of green and senescent leaf polyphenols, tannins, non-tannin polyphenols and nitrogen were analysed in both stands using geostatistical analysis. The spatial structures observed for green and senescent leaf polyphenols and tannins in the forested stand disappeared in the harvested stand. However, non-tannin polyphenols, as well as nitrogen, showed spatial structure in both stands. Understanding these changes may be important for the successful recovery of native oak populations growing under pine forests in NW Spain, one of the priorities of the local government. Our results showed that changes in the concentration of leaf secondary compounds after disturbance may be accompanied by differences in their spatial properties, which may have important consequences for ecosystem function.  相似文献   

15.
Tree growth and carbon dynamics are important issues especially in the context of climate change. However, we essentially lack knowledge about the effects on carbon dynamics especially in mixed stands. Thus, the objective of this study was to test the effects of climatic changes on the above and below ground carbon dynamics of a mixed stand of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) by means of scenario simulations. To account for the typical tree interactions in a mixed-species stand a spatial explicit tree growth model based on eco-physiological processes was applied. Three different climate scenarios considering altered precipitation, temperature, and radiation were calculated for an unthinned and a thinned stand. The results showed significant changes of above and belowground biomass over time, especially when temperature and radiation were increased additionally to decreased precipitation. The reduction in biomass increments of Norway spruce were more attenuated above than below ground. In contrast, the results for beech were the opposite: The belowground increments were reduced more. These results suggest a shift in the species contribution to above and belowground biomass under dryer and warmer conditions. Distinct effects were also found when thinned and unthinned stands were compared. A reduced stand density changed the proportions of above and below ground carbon allocation. As a main reason for the changed growth reactions the water balance of trees was identified which lead to changed biomass allocation pattern. This article belongs to the special issue “Growth and defence of Norway spruce and European beech in pure and mixed stands”.  相似文献   

16.
This investigation of three Abies alba stands differing in stem density (338–715 per ha) and vertical structure (one-storeyed or multi-layered) explored the relations between distance from neighbouring tree stems and local canopy openness and selected topsoil properties. The null hypothesis was that in relatively densely stocked forests of close–random stem distribution topsoil morphology, pH and moisture do not differ in inter-crown and under-crown patches. In three plots 1.1 ha in area, soil samples were taken in a square grid 5.0 × 5.0 m and analysed using semivariogram estimation and spatial autocorrelation. The local configuration of trees around the sampled locations was characterised using hemispheral photography and a local stand density index based on tree locations and diameters. The largest portion of the total variation in the soil variables analysed (68–100%) was attributable to small-scale variation in scales <5 m. In all stands, irrespective of density and vertical structure, local stand density/canopy openness correlated positively/negatively with ectohumus layer thickness but negatively/positively with upper soil pH and moisture. Variation in the local configuration of trees explained up to 17% of the total variation in organic horizon thickness, up to 22–29% in topsoil pH (depending on the horizon) and up to 19–27% in topsoil moisture. The results indicate that even in stands of random tree patterning, stem neighbourhood and small-scale variation in canopy density may contribute significantly to topsoil heterogeneity and potentially affect the functioning and structure of forest floor vegetation.  相似文献   

17.
The structure of forest stands changes through developmental phases. This study is carried out in the unmanaged, oriental beech (Fagus orientalis Lipsky) stands in the north of Iran. The aim of this research was to quantify structural characteristics of stands in the stem exclusion phase using common structural indices, which include mingling, tree–tree distance, stem diameter, and tree height differentiation. According to our measurements from three stands, naturally regenerated stands tend to be mixed in species composition have slightly heterogeneous diameter distributions and uniform tree height. The average distance between trees was 3.3 m. Stocking volume of the stands had an average of 540 m3 ha?1 and 412 stem ha?1. Dead wood volume was 24 m3 ha?1, and as a standing volume, the most frequent species in dead wood pool was oriental beech (F. orientalis) (48 %). The common form of dead trees was snag (41 %). The mean value of mingling and tree-to-tree interval indices revealed that beech was mixed intensively with hornbeam and appears to be a more successful competitor for space and light compared with hornbeam; moreover, we found relatively high evidence of inter-species competition in this phase. A better understanding of stand characteristics in the stem exclusion phase as a critical part of the natural dynamics of forest ecosystems could facilitate predictions about the future changes within the stand.  相似文献   

18.
Using the physiological single tree growth model BALANCE, vitality of forest stands was simulated in dependence of the site-related factors, climate and stand structure. At six level II plots in southern Germany with the main tree species beech (Fagus sylvatica L.), oak (Quercus robur L.), spruce (Picea abies [L.] Karst.), and pine (Pinus sylvestris L.), simulated results were compared to measured values (soil water content, bud burst and leaf colouring, diameter at breast height, tree height and crown density) in order to validate the model. Sensitivity tests were done to examine the influence and the interactions of the environmental parameters. The validation results show that BALANCE is capable of realistically simulating the growth and vitality of forest stands for central European regions for medium term time spans (several years). The validation of the water balance module produces mean absolute errors based on field capacity between 2.7 and 6.9% in dependence of sites and forest stands. Senescence of foliage as well as crown density is reproduced with a correlation coefficient of 0.70 compared to measurements. Differences between measured and simulated diameter values were smaller than 1% for spruce and smaller than 6.5% for beech after 7 years of simulation, and smaller than 1% for oak after 8 years of simulation. On the other hand, the simulations for pine trees conform less with the measurements (difference: 22.6% after 8 years). The sensitivity of the model on environmental changes and on combinations of these parameters could be demonstrated. The responses of the forest stands were quite different.  相似文献   

19.
In the north Saxon lowlands (near Torgau), effects of conversion of pure pine stands (Pinus sylvestris L.) into mixed stands by planting deciduous trees [Fagus sylvatica L. and Quercus petraea (Matt.) Liebl] were investigated on parasitoid wasps as pest antagonists. The effects of planting deciduous trees in pine stands were investigated using the strategy of space-for-time substitution including advanced plantations of beech and oak of different age classes. Wasps were captured at 4-week intervals by ground photoeclectors (GPE, n=6, 1 m2) and flight-interception traps (FIT, n=8), placed in the tree crown layer during the vegetation period (April–October) of 2000. A total of 32,479 parasitoid wasps belonging to 30 families were caught in the traps. Fifty-nine percent of individuals were representatives of families relevant as antagonists of forest insect pests: Ichneumonidae, Braconidae, Pteromalidae, Eulophidae, Mymaridae, Trichogrammatidae, and Scelionidae. Compared to the pure pine stand, individual numbers of most families of parasitoid wasps were statistically significantly higher in mixed stands with deciduous trees. The clearest promoting effects of deciduous trees on parasitoid wasps were manifested in the oldest age classes of advanced beech and oak plantations. Oak exerted stronger effects than beech. This applied especially to the tree crown layer, the stratum with the highest spatial correlation between important phytophagous pine pests and relevant parasitoids. The increased structural diversity of the stands and the broader spectrum of potential hosts are regarded as key factors for the promoting effects of advanced plantings of deciduous trees in pine stands on the community of parasitoid wasps.  相似文献   

20.
To determine the lifespan of Siebold’s beech (Fagus crenata), a dominant canopy tree species of the cool temperate forests of Japan, we estimated the age of 33 mature beech trees felled by a large typhoon in September 2004 at Karibayama, in southern Hokkaido. The study site lies within one of the northernmost distributions of Siebold’s beech populations in Japan. We counted tree rings from tree disks at a height of 1 m, and diameter growth was measured in annual increments. The sample age revealed two major peaks at 240 and 175 years. The diameter growth was good between 40 and 60 years of age and gradually decreased after 70 years of age. Annual diameter increments were noticeably small in good fruiting years, indicating a large allocation of annual carbon gains to the reproductive organs. Bud scale counts of juvenile trees revealed that the age at which the height reached 1 m was approximately 6–13 years. The lifespan of Siebold’s beech in the Karibayama population was therefore estimated to be approximately 250 years, an estimation that is higher than that previously reported for this species in the northernmost populations.  相似文献   

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