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1.
The role of different agroforestry systems in the conservation of plant diversity and forest structure has not been directly compared in many agricultural dominated landscapes. In this study, we investigated tree diversity and forest structure in a complex agroforestry landscape traditionally grown for cocoa and mixed food crops and compared these to the natural forest in southeastern Ghana. The study was carried out using 36 25 m × 25 m plots. There was significant difference [95% Confidence Interval (95% CI)] in the native forest/non-crop tree species richness between the natural forest and the agroforest farmlands but species richness was similar between the cocoa and mixed food crops agroforests. The density of native forest/non-crop trees was significantly higher (P < 0.05) in the natural forest but similar between cocoa and mixed food crops agroforest. Similarly, the basal area of native forest/non-crop trees was significantly higher (P < 0.05) in the natural forest but comparable between cocoa and food crops agroforest. Of the 20 most abundant native forest/non-crop trees recorded, 12 of them showed significant responses (P < 0.05) to land use change with nine of the species significantly abundant in the natural forest relative to the agroforest systems. Eighteen native forest/non-crop trees species in the agroforestry systems were commonly recorded as being used; 100% of them being used as fuel wood with 83.3 and 77.8%, respectively, used as medicines and materials. The findings of this study suggests that although complex agroforestry systems are a poor substitute for the natural forest the heterogeneous mosaic landscape in which complex agroforestry forms part can be strategically managed to maximize the benefits of both sustainable agriculture production and conservation of plant diversity by acting as buffer between protected areas and intensively managed areas.  相似文献   

2.
Cocoa cultivation is generally considered to foster deforestation. Contrary to this view, in the forest–savannah interface area in Cameroon, farmers have planted cocoa agroforestry systems on Imperata cylindrica grasslands, a soil-climate zone generally considered unsuitable for cocoa cultivation. We undertook a survey to understand the agricultural and ecological bases of this innovation. Age, cropping history and marketable cocoa yield were assessed in a sample of 157 cocoa plantations established on grasslands and 182 cocoa plantations established in gallery forests. In a sub-sample of 47 grassland cocoa plantations, we inventoried tree species associated with cocoa trees and measured soil organic matter levels. Marketable cocoa yields were similar for the two types of cocoa plantations, regardless of their age: 321?kg?ha?1 in cocoa plantations on grasslands and 354?kg?ha?1 in cocoa plantations in gallery forests. Two strategies were used by farmers to eliminate I. cylindrica prior to the establishment of cocoa plantations, i.e., cropping oil palms in dense stands and planting annual crops. Farmers then planted cocoa trees and fruit tree species, while preserving specific forest trees. The fruit tree and forest tree densities respectively averaged 223 and 68 trees?ha?1 in plantations under 10?years old, and 44 and 27 trees?ha?1 in plantations over 40?years old, whereas the cocoa tree density remained stable at 1,315 trees?ha?1. The Shannon–Weaver index increased from 1.97 to 2.26 over the same period although the difference was not statistically significant. The soil organic matter level was 3.13?% in old cocoa plantations, as compared to 1.7?% in grasslands. In conclusion, our results show that the occupation of grasslands by cocoa agroforestry systems is both an important example of ecological intensification and a significant farmer innovation in the history of cocoa growing.  相似文献   

3.
The sustainability of cocoa growing systems in the humid tropics is debatable. Socio-economic and technical data were obtained from 1,171 cocoa farmers and 1,638 cocoa plantations to assess the long-term dynamics of cocoa agroforests in central Cameroon since the beginning of the twentieth century. On-site, we estimated the age of the cocoa trees and measured their density in a sub-sample of 402 cocoa plantations. We inventoried associated woody species in 45 cocoa plantations from this sub-sample. Our results revealed a high Shannon index for the cocoa plantations (2.6) and showed that an average of 25 tree species per cocoa plantation had been planted with the cocoa trees at a density of 120 trees ha−1. Surveys indicated that there had been no mineral fertilization. Nearly 70% of the cocoa agroforests were over 40 years old, and all farmers continuously regenerated their cocoa tree stands. Irrespective of the cocoa plantation age, the cocoa tree density remained over 1,000 plants ha−1, and fermented dried cocoa yields were 255 kg ha−1 on average. Cocoa agroforests occupied 60% of the cultivated area on farms and cocoa sales accounted for 75% of total farm income. Almost a third of the farmers were from the area and under 40 years old. In conclusion, our results show that the farmers’ agroforestry practices, in addition to the fact that the cocoa tree stands were continuously regenerated and passed down between generations of farmers, could explain the long-term dynamics of cocoa agroforests in central Cameroon.  相似文献   

4.
Remnant trees and the conservation of biodiversity in Costa Rican pastures   总被引：1，自引：0，他引：1  
Remnant trees may play an important role in conserving biodiversity within agricultural systems because they provide habitats and resources that are otherwise absent from agricultural landscapes. In order to determine the potential importance of remnant trees for conservation, we surveyed the density and species composition of remnant trees occurring in pastures of 24 dairy farms near Monteverde, Costa Rica. In addition, we conducted interviews with farmers to determine why they leave trees in pastures and how they manage them. In our survey of 237 ha of pastures, we counted 5583 trees of 190 species (mean density of 25 trees/ha). Primary forest trees accounted for 57% of all of the species and 33% of tree individuals. Over 90% of the species are known to provide food for forest birds and other animals. In addition, many of the species are important locally for humans as sources of timber (37%), firewood (36%) or fence posts (20%). Farmers mentioned 19 reasons for leaving trees in pastures. Of these, shade for cattle, timber, fruits for birds and fence posts were most commonly cited. Most farmers were well aware of both the economic and ecological benefits of pasture trees, and were interested in the possibility of increasing tree cover within their pastures. Although the current densities and richness of pasture trees in Monteverde are high, the size distribution indicates that diversity will decrease substantially in future years, both because farmers are harvesting trees and because saplings of primary forest trees are scarce within the pastures. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

5.
In Central Cameroon cocoa is mainly produced by household farming systems based on complex associations between cocoa and companion trees. Setup either on native/remnant forest or savannah, these agroforestry systems (AFS) are managed according their geographical position and local pedoclimatic conditions. In this paper, we investigated the effects of local management strategies on carbon (C) storage of live trees in three different cocoa production zones of Central Cameroon. In the 58 fields studied, 8,996 cocoa trees and 1,258 companions were surveyed. Tree sampling was non-destructive and to estimate C storage we used allometric models for above- and belowground biomasses. We measured abundance, height, diameter at breast height and determined species of companion trees. We distinguished between four cocoa plantation age categories (immature, young, mature and senescent) and three preceding systems (forest, forest gallery and savannah). We surveyed farmers’ use of each associated tree, allocated it to a functional category and asked if it had been introduced or conserved. Total C content of live trees was on average close to 70 t ha?1. We found that it mostly relied on associated trees—cocoa trees contribution being ac. 2–12 % of live trees total C. The level of contribution to C storage of companions from different use categories differed between sites—trees producing food had contributed most in Bokito and Obala while trees used for shading or fertility contributed most in Ngomedzap. Dynamics of C storage in live trees was found to be independent from cocoa trees growth and age. When aging, AFS continuously lost companion trees and especially conserved ones putatively because of farmers’ selective logging. Yet, AFS apparently maintained equivalent C storage abilities with time. Hence, even if cocoa do not contribute significantly to C storage in our study, the systems into which they are included are able to significantly store C and may also contribute to other ecological services such as conservation.  相似文献   

6.
This study assessed the effects of exploitations in natural forest ecosystems on tree species diversity and environmental conservation. This was achieved by comparing tree species diversity and yield in an unlogged forest (Strict Nature Reserve) and a forest reserve where active logging is in progress in Ondo State, Nigeria. Eight plots (20 m × 20 m) were assessed in each site using systematic sampling techniques. All living trees with dbh >10 cm were identified, categorized into families with their diameter at breast height (dbh) measured in each plot. Shannon-Weiner and species evenness indices were used to assess and compare tree species diversity and abundance. The results show that the tropical humid forest is very rich in tree species, as a total of 54 different tropical hardwood species from 23 families were encountered in both forest types. There were 46 species distributed among 21 families in the unlogged forest and 24 species in 14 families in the logged forest. Shannon-Weiner diversity index of 3.16 and 3.03 and evenness index of .83 and .81 were also obtained for the unlogged and logged forest, respectively. Every variable computed had a higher value in the unlogged forest relative to the logged forest. In the unlogged forest, the species with the highest number of occurrence was Mansonia altissima A. Chev. (80 stems/ha). Caesalpinoidae and Sterculiaceae families had the highest number of species (6). In the logged forest, Triplochiton scleroxylon K. Schum. (18 stems/ha) had the highest frequency and Caesalpinoidae family has the highest number of species (4). The study concludes that exploitation has affected species diversity in the ecosystem and subsequently, the roles of trees in environmental conservation are affected.  相似文献   

7.
ABSTRACT

The Chunati Wildlife Sanctuary (CWS), a degraded protected area in southeastern Bangladesh, had been under comanagement since 2004. This study examined phytosociological characteristics and diversity of trees in CWS and discussed villagers’ opinions on the impact of comanagement on forest conservation. Following a stratified and systematic sampling 140 circular plots, 17.84-m radius each, were laid out in seven forest beats for the assessment of phytosociological characteristics and tree diversity. Several key-informant interviews and 15 focus group discussions were held to explore the impact of comanagement on forest conservation and on villagers’ livelihood. A total of 93 tree species were identified having a diameter at breast height (dbh) of ≥ 5 cm in 36 plant families. The dominant species were Acacia auriculiformis, Dipterocarpus turbinatus, Ficus hispida, and Tectona grandis. The average density of trees was 239 trees/ha of which 60% was composed of planted exotic species. Nearly 90% trees were belonging to 5- to 15-cm dbh class and the Shannon-Wiener index was 3.15. The comanagement governance had brought positive changes in forest conservation. However, to sustain the engagement of poor villagers in the comanagement and conservation of degraded CWS, more collective efforts are needed to support their living.  相似文献   

8.
The purpose of this study was to quantify the changes in tree diversity and above-ground biomass associated with six land-use types in Kodagu district of India's Western Ghats. We collected data on species richness,composition and above-ground biomass(AGB) of trees,shrubs and herbs from 96 sample plots of 0.1 ha. Totals of83 species from 26 families were recorded across the landuses. Tree species richness, diversity and composition were significantly higher in evergreen forest(EGF) than in other land-uses. Similarly, stem density and basal area were greater in EGF compared to other land-uses. Detrended correspondence analysis(DCA) yielded three distinct groups along the land-use intensities and rainfall gradient on the first and second axes, respectively. The first DCA axis accounted for 45% and second axis for 35% of the total variation in species composition. Together the first two axes accounted for over 2/3 of the variation in species composition across land-use types. Across the land-uses,AGB ranged from 58.6 Mg ha-1 in rubber plantation to327.3 Mg ha-1 in evergreen forest. Our results showed that species diversity and AGB were negatively impacted bythe land-use changes. We found that coffee agroforests resembled natural forest and mixed species plantation in terms of tree diversity and biomass production, suggesting that traditional coffee farms can help to protect tree species, sustain smallholder production and offer opportunities for conservation of biodiversity and climate change mitigation.  相似文献   

9.
In Africa’s main cocoa producing countries, rehabilitation of old cocoa orchards is increasingly debated but rarely adopted. In Central Cameroon, rehabilitation practices are regularly set up in old cocoa-based agroforestry systems (cAFS). To better understand the impact of such practices we built a chronosequence of 40 cAFS. We carried out specific surveys with farmers on each plot in order to check for rehabilitation effects on cocoa stands and associated woody species (AWS). We found that cocoa trees represented on average 88.2% of woody individuals and increased with age (from 84.7 to 91.5%). The cocoa stand basal area (BA) share significantly increased with age and reached up to 40.2% in the oldest systems. Cocoa, fruit and forest trees mean BA increased with aging. They were on average of 6.5, 5.7 and 10.7 m2 ha?1 respectively. Six different architectural types, different from the theoretical architectural evolution of cocoa trees over time, were identified. Among them, type 4 characterized by several orthotropic suckers of differing ages, was found typical of farmers’ cutting back practices. Type 4 cocoa trees density increased over time and its BA represented on average 60% of cocoa stand BA in the oldest systems. Concomitantly, farmer’s management of AWS led to continuous evolution of the systems both in terms of density and species composition. Our results show that (i) permanent densification and cutting back practices (type 4) allow the rejuvenation of cocoa stands while increasing cocoa stands BA share; (ii) the continuous management of AWS by farmers is undertaken to favour cocoa trees share over time by limiting inter-specific competition and promoting complementarity between cocoa trees and AWS. We argue that such practices explain a fair part of the long-term sustainability observed in cAFS from Central Cameroon and represent a model from which new rehabilitation schemes could be inspired.  相似文献   

10.
The extensive area of degraded tropical land and the calls to conserve forest biodiversity and sequester carbon to offset climate change demonstrate the need to restore forest in the tropics. Deforested land is sometimes replanted with fast-growing trees; however, the consequences of intensive replanting on biomass accumulation or plant and animal diversity are poorly understood. The purpose of this study was to determine how intensive replanting affected tropical forest regeneration and biomass accumulation over ten years. We studied reforested sites in Kibale National Park, Uganda, that were degraded in the 1970s and replanted with five native tree species in 1995. We identified and measured the size of planted versus naturally regenerating trees, and felled and weighed matched trees outside the park to calculate region-specific allometric equations for above-ground tree biomass. The role of shrubs and grasses in facilitating or hindering the establishment of trees was evaluated by correlating observed estimates of percent cover to tree biomass. We found 39 tree species naturally regenerating in the restored area in addition to the five originally planted species. Biomass was much higher for planted (15,675 kg/ha) than naturally regenerated trees (4560 kg/ha), but naturally regenerating tree regrowth was an important element of the landscape. The establishment of tree seedlings initially appeared to be facilitated by shrubs, primarily Acanthus pubescens and the invasive Lantana camara; however, both are expected to hinder tree recruitment in the long-term. Large and small-seeded tree species were found in the replanted area, indicating that bird and mammal dispersers contributed to natural forest restoration. These results demonstrate that intensive replanting can accelerate the natural accumulation of biomass and biodiversity and facilitate the restoration of tropical forest communities. However, the long-term financial costs and ecological benefits of planting and maintaining reforested areas need to be weighed against other potential restoration strategies.  相似文献   

11.
Coffee agroforestry is a conservation strategy that has shown promise to support the diversity of bird, bat, and insect communities, but few studies have focused on non-volant mammals in coffee farms. We assessed mammal diversity within coffee agroforestry systems in Kodagu, India and investigated the impacts of the non-native shade tree species, Grevillea robusta, on mammal diversity. Twenty farms, with varying amounts of G. robusta planted within the coffee farm, were sampled throughout three rainfall zones during the 4-month study period. We captured six species of small mammals, with indirect methods yielding an additional five species, totaling 11 mammal species. Contrary to current ecological thought, we found that increased amounts of G. robusta did not have a negative impact on either abundance or richness of mammals. Small mammal abundances were higher at farms with greater amounts of herbaceous ground cover and larger, mature shade trees, while small mammal species richness was found to increase with an increase in tree species richness as well as greater amounts of herbaceous ground cover. Additionally, small mammal abundance was higher at coffee farms closer to forested areas. Based on these findings, we suggest the maintenance or cultivation of shade tree richness, mature shade trees, and herbaceous ground cover within coffee farms and preservation of forested areas within the landscape to enhance coffee agroforestry habitat for non-volant mammals. We hope that these habitat requirements will be incorporated into conservation strategies for the promotion of biodiversity within coffee agroforestry systems.  相似文献   

12.
Agroforestry systems are potentially suitable for conservation of tree genetic resources. Farmers around Mt. Kenya usually integrate trees into their farm. Large parts of these trees seem to be of exotic origin, whereas indigenous species have priority for conservation. This study aimed at determining on-farm richness, composition and frequency of indigenous and exotic woody species around Mount Kenya to assess the suitability of farms for the conservation of indigenous tree species. 265 on-farm plots of 0.5 ha size each were selected in 18 different agro-ecological zones by using a stratified sampling scheme. All woody species within the plot were recorded with their local and scientific names. Total species richness was 424 (including 306 indigenous ones), mean richness per plot 16.5 species (including 8.8 indigenous ones). Eight out of the 10 most frequent species were exotic ones with Grevillea robusta from Australia ranking first (found on almost 76% of the surveyed farms). The proportion of indigenous species increased with increasing aridity and temperature. Dominance of exotic species was found at farms of humid mid- and highlands. Ordination analysis revealed that mostly exotic species contributed to separation of farms in the highlands and upper midlands, whereas indigenous species in the lower midlands and lowlands. As the frequencies of most indigenous trees were low, only parts of the surveyed farms can contribute to conservation of tree genetic resources, particularly the less intensively managed farms of the more arid lands. Farmers’ access to knowledge on valuable indigenous tree species and to quality seedlings of these trees need to be improved to increase indigenous species’ frequencies on farms and possibly to replace some of the exotic species in the future.  相似文献   

13.
The suitability of plantation monocultures for the conservation of forest animals is an issue under continous debate. The adaptability of forest dwellers and the forest management regime seem to play key roles. In this study, I investigated the habitat selection of a generalist bird, the great spotted woodpecker (Dendrocopos major), within a pine (Pine spp.) monoculture, as well as the importance of the native habitat features within the pine matrix for the species’ conservation. I compared 52 plots with woodpecker presence against 121 plots where the species was absent, as well as 68 nest-trees against 90 random ones. Regression analyses were used to investigate the habitat attributes involved in the habitat selection. Although the great spotted woodpecker is considered a generalist forest dweller, it shows a marked habitat selection. Based on presence/absence records, the woodpecker prefers well-forested patches with high levels of tree diversity and with good coverage of a secondary species such as the strawberry tree (Arbutus unedo). To excavate their nests, woodpeckers select large trees in patches where other trees are also larger, rejecting patches with a high number of small trees. The most striking conclusion from this work is the preference shown for native trees, especially Portuguese oaks (Quercus faginea), as nest-trees. This is noteworthy because native trees are smaller and they are surrounded by smaller trees than pines. These findings support that woodpecker conservation benefits from an increase of habitat heterogeneity, particularly by the retention of native woodland patches within the plantation matrix.  相似文献   

14.
This study explores the diversity in sensitivity to drought of moist tropical forest tree species. Yearly tree growth records collected over a ten-year period in two one-hectare 70-year-old damar agroforest plots in Sumatra are analysed. These agroforests are mixed tree plantations, dominated by Shorea javanica K. & V., a dipterocarp tree cultivated and tapped for its commercially valuable resin (damar). Many indigenous fruit tree species grow in these agroforests, as well as timber tree species originating from the nearby natural forest. During the census period the multi-species stands were subjected to three El Nino Southern Oscillation (ENSO)-related droughts (1994, 1997 and 2002). At the tree community level, these droughts were associated with a marked decrease in radial stem growth. Multilevel modelling was used to explore the relative contribution of species, tree size and individual tree characteristics to the observed response to drought.All tree species appeared to be sensitive to drought but the amplitude of the response varied significantly across species. Predicted species mean decrease in stem radial growth rate on drought years (i.e. years with 6 months with less than 50 mm/month rainfall) ranged from less than 5% to more than 80%. Shared species were ranked consistently between plots indicating that the results were robust. Stem diameter significantly affected tree sensitivity to drought in two species only, but in opposite ways: in S. javanica, larger trees appeared to be less sensitive while the opposite was true for Lansium domesticum, an abundant fruit tree. Individual tree sensitivity to drought contributed significantly albeit to a small extent to the overall response to drought. This individual tree effect did not show any pattern of spatial correlation and hence could not be related to topographic features. It is likely to reflect the individual's unique history and genotype.  相似文献   

15.
In the last 10 years the Sri Lankan government has changed its policy regarding its remaining rain forest from one that promoted commercial exploitation to one of conservation. The growing importance of uplands as catchments for water production, biodiversity conservation and other downstream services has been recognized by the Sri Lankan government. It is therefore timely that we review 15 years of research investigating rain forest dynamics of southwest Sri Lanka with the objective of using this knowledge for forest restoration. We provide six common principles for understanding the integrity of rain forest dynamics in southwest Sri Lanka. The principles are: (i) disturbances provide the simultaneous initiation and/or release of a new forest stand; (ii) that disturbances are generally non-lethal to the groundstory vegetation; (iii) disturbances are variable in severity, type and extent across rain forest topography; (iv) guild diversity (habitat diversity) is dependent upon “advance regeneration”; (v) tree canopy stratification is based on both “static” and “dynamic” processes; and (vi) canopy dominant late-successional tree species are site specialists restricted to particular topographic positions of the rain forest. These principles are applied to determine effects of two rain forest degradation processes that have been characterized as chronic (continuous detrimental impacts) and acute (one-time detrimental impacts). Restoration pathways are suggested that range from: (i) the simple prevention of disturbance to promote release of rain forest succession; (ii) site-specific enrichment planting protocols for canopy trees; (iii) sequential amelioration of arrested fern and grasslands by use of plantation analogs of old field pine to facilitate secondary succession of rain forest, and plantings of late-seral rain forest tree species; and (iv) establishment and release of successionally compatible mixed-species plantations. We summarize with a synthesis of the restoration techniques proposed for reforestation using native vegetation on cleared conservation areas and parks, and for the stabilization of eroded upland watersheds. We conclude with a comparative analysis with restoration work done in other tropical forest regions.  相似文献   

16.
As reforestation and restoration processes gain momentum across the world native tree species are being established for production, conservation and restoration purposes in agricultural landscapes. One such tree with promise is dinde [Maclura tinctoria (L.) D. Don ex Steud]; a multi-purpose, Neotropical tree species that is being widely introduced on to farms of the coffee axis region in the Latin American Andes. No formal studies have been made that examine its potential for reforestation. In this study we aim to measure and define the relationships between age, bole size (dbh), tree height, and crown size of planted dinde trees for the development of spacing guidelines at time of planting and for thinning. We also sought to identify whether tree growth is influenced by various measures of soil fertility. We studied these relationships on dinde trees planted at twelve farms in the central Andean foothills of Colombia. Our results are the first to show dinde has comparable growth to other native and exotic trees used for reforestation in Latin America. Strong relationships exist for tree age and diameter at breast height (DBH) with crown size and height. Based on these relationships we developed spacing and thinning guidelines for timber production in plantation and silvo-pastoral circumstances. Soils were generally fertile but varied between farms. Growth varied with soil primarily related to pH and calcium, and secondly to soil nitrogen and organic matter. Our results provide preliminary information for the forester and/or the farmer on expected growth and size relationships for given ages in relation to soil fertility for planted trees. As more trees are planted on a wider array of soils and providing a greater diversity of ages further studies are necessary for refining guidelines.  相似文献   

17.
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18.
Tree diversity in West Africa is threatened by intensified land uses and salinization,and farmers' role in conservation of tree species is unclear.We hypothesized that farmers contribute to conservation of tree diversity through protection of trees in their agroforestry landscapes and compared the diversity and structure of the tree vegetation across landscape classes.Inventories were carried out in three villages in the Groundnut Basin in Senegal,assessing tree diversity,density and crown cover.Tree diversity as assessed by species accumulation curves was high in forests,but cultivated landscapes had comparable or almost comparable diversity,especially in the cases where the forest was planted or was affected by charcoal production.However,the occurrence of exotic species was higher in cultivated parts of the landscape,and although many species were in common,ordination plots indicated that forests and cultivated landscapes to some degree had different species composition.Salinity had a strong influence on vegetation,not only in the tans(salt marshes) but also across the other landscape classes.In conclusion,agroforestry landscapes in the three villages harbor considerable tree diversity,but insufficient to fully conserve the tree species.We argue that informing and including farmers in tree management in the region will contribute to overall conservation of tree genetic resources.  相似文献   

19.
Agroforestry for production and ecosystem health is a centuries-old form of ecosystem management used in many cultures indigenous to Mesoamerica, yet implications of such practices for biodiversity conservation are not well understood. Agroforestry systems were studied using interviews of farmers and field surveys of tree and bird diversity in three communities surrounding the Calakmul Biosphere Reserve in Campeche, Mexico to examine how differences in forest management practices affect forest biodiversity. Tree diversity and bird species richness were higher in areas surrounding communities that generated a greater variety of forest products and that cultivated “restoration trees,” species planted to aid in regeneration of mature forest. We conclude that traditional ecosystem management methods in areas surrounding natural reserves as practiced by inhabitants who depend on resources in the reserve for survival are compatible with maintaining and perhaps enhancing diversity of bird and tree communities at the site level.  相似文献   

20.
In Europe, the English yew species (Taxus baccata L.) is endangered. Intensive human land-use, including forest management, has caused a decrease of the yew populations all over Europe. In Austria, gene conservation forests are used for the in situ conservation of populations of this rare tree species by silvicultural treatments. In order to improve the conservation management in these gene conservation forests, this study addresses the relation between competition and viability of yew populations through the use of structural diversity indices. The structural indices, which include mingling, tree–tree distance, diameter, and tree height differentiation, were determined for a structural group of four trees as well as the neighbouring trees of the male and female yews at the monitoring plots on a regular grid in three gene conservation forests. Although the three study sites provided quite different environmental conditions for English yew, the vitality of each individual yew was influenced by the inter-specific competition of the neighbouring tree species at all sites. Low vitality was associated with a small mean distance to neighbours and large tree height differentiation. In conclusion, we suggest that a combination of different structural indicators is needed for an integrative assessment of conservation status in the gene conservation forests. This would help improve the evaluation of the impact management has on yew population viability.  相似文献   

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