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1.
Population viability risk management (PVRM) provides a framework for explicitly including qualitative information about the possible outcomes of a management decision with regard to the viability of an endangered population in conservation management. Multi-criteria decision-making (MCDM) techniques enables managers to select the most preferred choice of action in a context where several criteria apply simultaneously. In that context a combined approach of the PVRM concept and a MCDM technique is presented for the development, evaluation and finally ranking of the in situ conservation strategies. We discuss the concept based on a case study for the maintenance of a gene conservation forest of an English yew population (Taxus baccata L.) in Styria, Austria. As part of the PVRM the analytic hierarchy process (AHP) is used to evaluate six conservation strategies with regard to the viability of the yew population. The viability of the population is evaluated based on the results of an analysis of the current environmental, social and economical state and a characterization of the ecological parameters of its population. The most significant risk factors (illegal cutting, browsing by game, tree competition, light availability and genetic sustainability) are structured and prioritised according to their impact on the viability of the yew population applying the AHP. Effects of the six conservation strategies on the viability of the yew population are determined through a qualitative assessment of the probability of a decrease of the population along with four different environmental scenarios. In this context strategy IV combining selective thinning, protection measures, game control with public relation activities seems to be the most effective alternative. The benefits of the combined approach of the PVRM concept with the AHP for the rational analysis of conservation strategies for this endangered tree species are discussed.  相似文献   

2.
English yew Taxus baccata L. has been catalogued as endangered tree species and prone to extinction in Austria as well as many other parts of Europe. The present work is based on the comparison of the natural population of two gene conservation forests from different geographic locations in Austria where the spatial structure, regeneration status and possible conservation measures are examined. The pole stand distribution varied distinctly in each sites. The total no of individuals per ha （DBH ≥5 cm）, average DBH and average height were 492 n.hm^-2, 8.8 cm and 6.3 m in Stiwollgraben whereas in Leininger Riese 45 n.hm^-2, 16.3 cm and 7.6 m respectively. Over 79% of the Stiwollgraben population were represented the good health condition, while in Leininger Riese it was less then 49 % which means population of Stiwollgraben is in better condition compared to Leininger Riese. The sites differed considerably in the pattern of regeneration but pattern were consistent with the dynamics depicted by the age distribution. Considering the one-year-old seedlings Stiwollgraben contains 13 019 individuals.hm^-2 whereas Leininger Riese only 1 368. Surprisingly there were no any saplings in respect of 51 to 150 cm height classes in both sites and 30 to 50 cm in Stiwollgraben. In that context the conservation of English yew on the forest level may require well-managed reserves and long-term rotations between harvest events, protection from the herbivore and reduction of competition, which will enhance the long-term viability of the species.  相似文献   

3.
The conversion of anthropogenic into more natural, self-regenerating forests is one of the major objectives of forestry throughout Europe. In this study, we present investigations on permanent plots with different silvicultural treatment in NE German pine stands. Management of old-growth pine stands on acidic and nutrient-poor sandy sites differs in fencing, thinning, and planting of certain tree species. The investigations were carried out on the community, population, and individual level of the pine forest ecosystems. Thus, vegetation changes, size and height of tree populations, and height increment of tree individuals were observed over a time span of 6 years. Special attention was paid to short-lived tree species such as, e.g., Frangula alnus and Sorbus aucuparia, as well as to Fagus sylvatica as one of the most typical forest tree species of Central Europe. Vegetation changes are interpreted as a consequence of natural regeneration of formerly degraded forest sites, involving an increase in nutrient availability. High browsing pressure can be considered as a key factor for the inhibition of tree seedlings and growth of saplings. Some Sorbus aucuparia individuals, however, succeeded in growing out of the browsing height also in unfenced stands. Few found specimens of Fagus sylvatica proved that this species is able to establish spontaneously on these relatively dry, acidic sites under continental climate influence. Such natural regeneration processes, also including spontaneous rejuvenation of trees, can be integrated into silviculture as passive forest conversion management. An active management like thinning of stands, planting of trees, and fencing can accelerate forest conversion with regard to height growth and species number of trees.  相似文献   

4.
A series of conventional distance-independent and distance-dependent competition indices, a highly flexible distance-dependent crowding index, and two light resource estimation indices were compared to predict individual tree diameter growth of five species of mature trees from natural-origin boreal mixed forests. The crowding index was the superior index for most species and ecosites. However, distance-independent indices, such as basal area of competing trees, were also effective. Distance-dependent light estimation indices, which estimate the fraction of seasonal photosynthetically-active radiation available to each tree, ranked intermediate to low. Determining separate competition indices for each competitor species accounted for more variation than ignoring species or classifying by ecological groups. Species’ competitive ability ranked (most competitive to least): paper birch ≈ white spruce ≈> trembling aspen > lodgepole pine > balsam poplar. Stratification by ecosite further improved model performance. However, the overall impact of competition on mature trees in these forests appears to be small.  相似文献   

5.
Secondary evergreen broadleaved forests are precious remnants for biodiversity conservation and templates for sustainable management of natural forests in subtropical China. Floristic composition, size structure, and spatial pattern of dominant tree species have been investigated for a subtropical secondary evergreen broadleaved forest in the Huitong Yingzuijie National Forest Reserve, Hunan, China. The location of all trees greater than 4 cm in diameter at breast height (DBH) were mapped within a 0.96-ha plot in which species, DBH, and total tree height were recorded. Ripley’s K(t) function was used to analyze spatial patterns and associations. The secondary forest consisted of 74 tree species and 1,596 stems per hectare. A reverse-J shaped DBH classes distribution was observed for all stems and trees of later seral species whereas trees of earlier successional species were distributed irregularly. Significant aggregated spatial patterns were observed for all trees within the forest and for conspecific trees of each dominant species. This result, and a repulsive spatial pattern for interspecific trees of Choerospondias axillaries and Cyclobalanopsis glauca against other dominant tree species, support segregation hypothesis. Contributions of seed dispersal, topographic heterogeneity, and competition to spatial patterns of conspecific trees vary depending on tree species. Attractive spatial pattern among interspecific trees of Liquidambar fortunei, Liquidambar formosana, and Pinus massoniana reflects stochastic colonization of pioneer tree species and a facilitation relationship. Although deciduous species are long-lived and persist over long successional processes, they will eventually be replaced by late seral evergreen species within the secondary forest if no disturbance events occur.  相似文献   

6.
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   

7.
The genetic structures of six populations of English yew (Taxus baccata L.) from different parts of Bosnia and Herzegovina have been characterized by means of isozyme analyses. Using six polymorphic gene loci, a total of 16 alleles have been found with a number of nine alleles, which were in common in all populations. In general, the values of observed heterozygosity reflect a very high level of individual genetic variation. Great differences in the relative allele frequencies lead to relatively high gene pool distances between the populations. Whereas the genetic structures of four populations corresponded essentially with the results of publicized investigations of yew populations from other parts of Europe, two occurrences show great differences. The possible reasons of these peculiarities are discussed. Based on the results of the genetic analyses, different measures for the maintenance and development of the genetic resources are recommended. The conservation management on the population level can prevent the possible loss of genetic adaptation as far as the reasons of genetic differences and their importance are not discovered to a sufficient extent.  相似文献   

8.
Fire hazard reduction treatments are commonly applied to mixed-species coniferous forests in western Montana, USA, to modify fuels structures and alter the competitive environments of individual trees. An improved understanding of how competition can be measured and how it conditions individual tree growth is needed for projecting the development of these forests, with and without treatment. Numerous studies have evaluated how competition affects tree growth and many indices have been developed to quantify the competition an individual tree experiences. These studies suggest that no single competition index or a single class of indices is universally superior; indices perform differently according to forest type and forest conditions. We chose several widely used distance-independent and distance-dependent competition indices, and also derived anisotropic distance-dependent indices from estimates of light interception by tree crowns. We evaluated the effectiveness of these competition measures for predicting basal area increment (BAI) of Pinus ponderosa, Pseudotsuga menziesii, and Larix occidentalis in western Montana. The best distance-dependent competition indices explained a larger proportion of growth variation than the best distance-independent indices (64% vs. 56%). This result indicates that competition is an important growth determinant in these forests and that competition varies locally, with variable tree densities and relatively complex stand structures creating heterogeneous neighborhood conditions. Competition indices derived from light interception models were only weakly correlated with other indices and performed poorly in terms of predicting tree growth. This result accords with previous observations that competition for light is not the primarily growth limitation for trees in the semi-arid conditions of western Montana. More sophisticated light availability models could be used to better assess variability in light interception and its marginal contribution to predictive accuracy of radial tree growth. Diameter and distance-dependent BAI models were developed for growth prediction at the species level and for all species combined.  相似文献   

9.
Tree height and crown allometries reflect adaptations for resource acquisition and structural stability, as well as plastic responses to a heterogeneous environment. While both light and soil resources limit growth and influence competitive responses in tropical forests, the effects of belowground resources on allometries are less understood, especially within the understory. To characterize outcomes of tree competition along an edaphic resource gradient, we quantified variation in height and crown allometries of six Bornean tree species from contrasting regeneration niches (light-demanding vs. shade-tolerant) on two soil habitats (clay-fine loam and sandy loam) within a 52-ha forest dynamics plot. Using empirically-fit allometric parameters and diameter growth rates from plot census data, we modeled tree height and crown area growth over the projected life span of each species. Based on resource competition theory, we hypothesized that tree species specializing on and populations of generalist species growing on the relatively moister, more fertile clay-fine loam soil habitat would have faster height and crown growth rates, compared to those on the sandy loam habitat, regardless of regeneration niche. Among soil specialists and within generalists of both genera, trees growing on clay-fine loam had taller stems and larger crowns at a given age and faster height and crown area growth rates at most sizes than trees on sandy loam. Differences in height and crown growth were driven by the faster diameter growth rates of trees on clay-fine loam, not by differences in height- and crown-diameter allometries, as trees on sandy loam were significantly taller at a given diameter, and differences in crown allometry were not consistent across soil habitats. Characterizing the height and crown growth responses of trees along resource gradients provides insight into the mechanisms that maintain diversity in tropical forests. Our results point to the importance of adaptive and plastic responses to both above and belowground resource availability in determining the allometric growth of trees and suggest that this diversity of responses may contribute tree species coexistence through competition-based trade-off mechanisms and variation in growth among individuals. Additionally, as the importance estimating natural carbon sequestration increases with the escalating effects of anthropogenic climate change, differences in tree growth and architecture across soil habitats also have implications for the approximation of forest carbon storage on heterogeneous tropical soils.  相似文献   

10.

Context

Uneven-aged management systems based on selection silviculture have become popular in European mountain forests and progressively replace other silvicultural practices. In time, this trend could lead to a homogenisation of the forest mosaic with consequences on structural indices recognised as beneficial to forest biodiversity.

Aims

This study was conducted to investigate the potential effects of a generalisation of the selection silvicultural system on structural diversity in the forest landscape with consequences for forest biodiversity conservation.

Methods

We compared four structural indices (tree species richness, diameter heterogeneity, deadwood volume and basal area of mature trees) in five different stand types typical of the northern French Alps, using forest plot data in the Vercors mountain range. Through virtual landscape simulations, we then calculated predicted mean proportions of stand types under two different conservation strategies: (i) maximising mean index values at the landscape level and (ii) maximising the number of plots in the landscape with index values above given thresholds.

Results

Multi-staged forests did not maximise all indices, the best solution being to combine the five stand types in uneven proportions to improve biodiversity conservation.

Conclusion

The expansion of selection silviculture in European heterogeneous forest landscapes could enhance biodiversity conservation if other stand types with complementary structural characteristics are maintained.  相似文献   

11.
Models for predicting height and diameter of individual trees in young Picea abies (L.) Karst. stands were developed. Data collected in a large survey of young forest stands in Sweden (the HUGIN young stand survey) were used in the construction of the models. Models were developed both with and without competition indices included. When constructing the competition indices trees within three metres from the subject tree were regarded as competitors. Functions with competition indices included (distance dependent) will be useful in analyses of the development of stands with different stand structure, whereas functions without competition indices (distance independent) will be useful in systems for long‐term forecasts of yield.  相似文献   

12.
在瓦屋山定位研究了中亚热带湿性常绍阔叶林次生群落１５a来各乔木种且成及其重要值、密度，大小结构、高度结构和材积生产力的动态变化，结果表明，自然恢复过程中次生常绿阔叶林群落乔木层物种组成变化明显，有１１种从群落乔木层消失，也有１０种出现，乔木层树种多样性（丰富度）基本保持动态平衡和发展；优势种地位保持不变，但次优势种地位得以加强；群落结构变化较大，突出表现为种群密度、胸径和树高分布格局的变化和立体空间的分布，群落由单优或双优种向双优或多优势种发展，由单一乔木屋向多层次立体结构发展，空间加厚，群落更复杂、稳定性增强。乔木种群平均高生长速度在２４－４８cm.a^-1 ,平均ＤＢＨ生长率在０.３４－１.１０cm.a^-1，各种群生长速度差异明显，按生长速度可划分为适应性强的速生树种如细梗呈茱萸叶五加，华木荷（平均ＤＢＨ生长在０．７０cm.a^-1以上），中等速度的小叶青冈、扁制栲（平均ＤＨＢ生长在０．４０cm.a^-1以上），慢生种如润楠、石栎（平均ＤＨＢ生长在０．４cm.a^-1以下）；种群材积生产力高低不一，优势种扁刺种群材积生产力并不是直增长，而是在后期出现下降；次优势和睦产长速度较快。１９９７年３固定样地材积量２１８－２２５m^3.hm^-2，优势种群材积生产力是群落材积生产力的高低的关键，在相同的环境条件下和各种群相互作用下，密度是各种群生长和材积生产力高低的决定因素之一。  相似文献   

13.
Conspecific negative density dependence in tree species can have major consequences for structuring of communities, yet in temperate forests this phenomenon remains largely unexplored. We investigated density-dependent recruitment in the long-lived conifer yew (Taxus baccata L.), for which low levels of regeneration have been linked with reduced light availability beneath conspecific canopies and speculative autotoxic effects. We combined in situ assessment of yew regeneration in a temperate forest in southwest Ireland with ex situ pot experiments to assess whether light and/or beneath conspecific canopy conditions inhibit the germination and early growth of yew. In field experiments, recruitment was related to distance from adult conspecifics, with higher levels of regeneration found in areas not beneath yew canopies. However, reduced light availability beneath the dense yew canopy was not responsible for this pattern, with abundant seedlings found in areas of equivalent or even lower light availability. Pot experiments showed that seedling survival was highest in deep shade treatments. Experiments also demonstrated that the addition of yew needles negatively affected seedling growth, but not seed germination. Together, our results suggest that under natural forest conditions, the absence of regeneration beneath mature yew canopies, often attributed to low light availability, may at least be partly related to substances in yew canopy or leaf leachates.  相似文献   

14.
Gmelina arborea is an important timber-yielding tree that grows naturally in the tropical and subtropical regions of Southeast Asia and has also been introduced as a plantation species outside these regions. Genetic diversity in this tree species was observed in stone/seed-related traits and in vitro responses of cultured nodal segments from plants of eight different populations representing natural forests, fragmented forests and plantations. Variance analysis showed significant differences between populations for these traits. However, it was not possible to separate the different populations using these traits by multivariate analysis, even after environmental variation was reduced over six subcultures. Genetic diversity was therefore analysed using molecular markers. Inter-simple sequence repeat (ISSR) primers yielded 95% polymorphic loci among the eight populations and UPGMA analysis enabled separation of these populations on the basis of their genetic distances. Diversity was also analyzed using population genetics parameters like Nei’s genetic diversity and gene differentiation. Nei’s genetic diversity was 0.29 between populations and 0.11 within populations. AMOVA analysis indicated 41 and 59% within- and between-population genetic diversity, respectively. Mantel test suggested that genetic differentiation between six Indian populations was positively correlated to geographic distance (r = 0.626, P = 0.029). Assessment of the genetic variation in G. arborea populations is an important step in selection of conservation strategies for this species since diversity forms the basis for species adaptation.  相似文献   

15.
We analyzed the structure of pollarded oak forest and biometric indices of pollarded oak species in relation to aspect in northern Zagros forests, western Iran. A number of 319 circular plots (0.1 ha) were established using a systematic random method over the study area. In each plot, for all trees (diameter at breast height ≥5 cm) diameter was measured and tree species was recorded. Total height, trunk height, and major and minor diameter axis of the crown of two trees in each plot (nearest tree to the center of the plot and the largest tree in term of diameter) were measured. As the dispersion of slope and altitude classes in the study area were identical, the effect of these factors was assumed to be constant. To evaluate the effect of aspect on biometric indices of oak trees a comparison was used for each oak species separately. The results indicated that the forest species composition differed statistically significant in main aspects except for easterly and westerly aspects (P < 0.01). The diameter of similar oak trees was significantly different except for Lebanon oak in northerly and southerly and Gall oak in easterly and westerly aspects (P < 0.01), but there was no significant difference between the total height and crown area of similar oak species in different aspects. Differences in diameter, height, and crown area distributions showed a significant difference in main aspects. The basal area and tree density in northerly and southerly aspects were significantly different (P < 0.05).  相似文献   

16.
Sunström  Erik  Hånell  Björn 《New Forests》1999,18(2):113-129
In 1971, a series of five afforestation trials were established along a north-south gradient on open peatlands in Sweden. All areas were drained, fertilized and planted with Scots pine (Pinus sylvestris). Survival and height of the planted trees as well as the amount of natural establishment, i.e. downy birch (Betula pubescens), silver birch (Betula pendula), Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and other deciduous species: (e.g. Salix sp., Sorbus aucuparia), by seeding from nearby forests were measured 18–22 years later. The amount of naturally established trees exceeded the number of living planted trees in all five areas. Next to downy birch, Scots pine was the most common naturally established species. Large variations in both amount and height of natural establishment were found along the climatic gradient. Planted trees were taller than naturally established trees, except for the northernmost area. Number and height of naturally established trees correlated positively to closeness to nearest forest and to nearest ditch. These trees also responded positively to PK fertilization in the three southernmost areas. In the two northernmost areas no such response was found. It was concluded that natural seeding from neighbouring forests can be counted on and recommended in afforestation of low-productive peatlands in Sweden, provided that downy birch is accepted as a dominant tree species.  相似文献   

17.
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   

18.
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19.

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.

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20.
The structural diversity in urban forests is highly important to protect biodiversity. In particular, fruit trees and bush species, cavity-bearing trees and coarse, woody debris provide habitats for animals to feed, nest and hide.Improper silvicultural practices, intensive recreational use and illegal harvesting lead to a decline in the structural diversity in forests within larger metropolitan cities. It is important to monitor the structural diversity at definite time intervals using effective technologies with a view to instituting the necessary conservation measures. The use of satellite images seems to be appropriate to this end. Here we aimed to identify the associations between the textural features derived from the satellite images with different spatial resolutions and the structural diversity indices in urban forest stands(Shannon–Wiener index, complexity index, dominance index and density of wildlife trees).Rapid Eye images with a spatial resolution of 5 m 9 5 m,ASTER images with a spatial resolution of 15 m 9 15 m and Landsat-8 ETM satellite images with a spatial resolution of 30 m 9 30 m were used in this study. The firstorder(standard deviation of gray levels) and second order(GLCM entropy, GLCM contrast and GLCM correlation)textural features were calculated from the satellite images.When associations between textural features in the images and the structural diversity indices were assessed using the Pearson correlation coefficient, very high associations were found between the image textural features and the diversity indices. The highest association was found between the standard deviation of gray levels(SDGLRAP) derived from RVIRAPof Rapid Eye image and the Shannon–Wiener index(Hh) calculated on the basis of tree height(R2= 0.64). The findings revealed that Rapid Eye satellite images with a spatial resolution of 5 m 9 5 m are most suitable for estimating the structural diversity in urban forests.  相似文献   

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