Arbuscular mycorrhizal fungal association in Asteraceae plants growing in the arid lands of Saudi Arabia

The present research was undertaken to explor the possibility of arbuscular mycorrhizal(AM) association with Asteraceae plants in the arid lands of Saudi Arabia(Al-Ghat, Buraydah, Thumamah and Huraymila). AM fungal colonization in the roots, spore numbers in the rhizosphere soil, fungal species diversity and correlation between AM properties and soil properties were determined. The highest colonization was in Conyza bonariensis(65%) from Al-Ghat, Anthemis cotula(52%) from Buraydah and C. bonariensis(53%) from Thumamah. The lowest was in Vernonia schimperi(41%) from Al-Ghat, Pulicaria undulata(25%) from Buraydah, Acanthospermum hispidum(34%) from Thumamah, Asteriscus graveolens(22%) and V. schimperi(22%) from Huraymila. Vesicular and arbuscular colonization were also presented in all plant species examined. The number of spores were 112–207 in Al-Ghat, 113–133 in Buraydah, 87–148 in Thumamah and 107–158 in Huraymila. Funneliformis mosseae, Glomus etunicatum, G. fasciculatum and G. aggregatum were identified. Relative frequency of AM fungal species varied widely and was irrespective of location and plant species. Diversity index varied with the rhizosphere soils of different plant species at various locations. Soil properties varied with locations and no distinct correlations were observed among the soil properties, root colonization and the number of spores. The results of the present study specified the association of AM fungi in different plants of Asteraceae and its significance in the ecological functioning of annual plants in the punitive environments of the rangelands in Saudi Arabia.     

Population viability risk management (PVRM) for in situ management of endangered tree species—A case study on a Taxus baccata L. population

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.     

奥地利两块基因资源保育林内英国紫杉生态条件与保护现状比较

在奥地利及其他多数欧洲国家英国紫杉濒临灭绝,被列为濒危树种.基于不同地理位置的自然群落的比较,调查了奥地利两块基因资源保育林内英国紫杉的空间结构、更新状况及可采取的保育方法等.每块样地圆杆材分布变化较大.林地Stiwollgraben内紫杉单位面积植株总数,平均胸径和平均株高分别为492 n·hm-2, 8.8 cm and 6.3 m;Leininger Riese仅为45 n·hm-2, 16.3 cm and 7.6 m.Stiwollgraben群落紫杉长势较好,健康植株79%以上,而Leininger Riese群落的健康植株低于49%.两块样地内紫杉更新模式差异较大,与其各自的树龄动态分布相一致.1年龄幼树相比较,Stiwollgraben林地内紫杉密度为13019株/公顷,而Leininger Riese仅为1368株/公顷.Leininger Riese林地内未发现树高51-150cm的幼树,而Stiwollgraben林地内树高30-150cm的幼树鲜能见到.这种情况下,英国紫杉林的保育需要管理完善的保护区、采伐期间采取长期轮伐,同时还要防止牲畜啃食和减轻种间竞争,以此来增强红豆杉的生存能力.图4表4参41.     

Large scale biotic damage impacts on forest ecosystem services

Insect outbreaks are natural phenomena that play a critical role in the development, senescence, and rebirth of forests. However, the damage caused by large-scale epidemics can have landscape scale consequences that are often poorly understood. The recent mountain pine beetle (MPB) outbreak in Canada has impacted a record >18.5 million hectares of pine forests, placing forest values at risk and significantly impacting forest-dependent communities within the region. To assess this impact, an ecosystem service-based approach was applied. Based on land cover information and monitoring data, four ecosystem services were assessed and mapped: merchantable timber, water provisioning, aboveground carbon storage, and vegetation diversity (supporting habitat). Timber is the most impacted provisioning ecosystem service followed by water provisioning, with peak stream flow in affected watersheds being positively related to mortality percent. Effects on carbon storage are substantial, with 20% of total timber aboveground carbon in dead pine trees. These effects may be mitigated, however, by the growth response of residual live trees and forest regeneration. The potential vegetation diversity showed a positive response to MPB-caused tree mortality. The results of our study may help with setting management priorities in response to large-scale biotic damage in forests in British Columbia and elsewhere.     

Variability in height growth,survival and nursery carryover effect of Betula papyrifera provenances

Eleven paper birch (Betula papyrifera Marsh.) provenances from a single geographic region in northern Idaho and four geographic regions in British Columbia (BC) were studied to determine whether morphometric variability was due to species' genetics, growing environment, or their interaction. Seedlings were grown at three nurseries in BC and Idaho and planted in a randomised single-tree interlocking block design at Skimikin (50°47′) and Red Rock (53°45′) common gardens in BC. Geographic variation in birch height growth was regulated by genetics and a complex interaction with environmental factors. Growth does not follow latitudinal, longitudinal or elevational clines although provenances at the southern garden showed better height growth compared to the northern garden. Greater percentages of seedling mortality were observed at the northern garden compared to provenances planted at the southern garden. Birch height growth was significantly influenced by nursery displacement effects up to four years after establishment. The safe range of southward seed-transfer distance may be as much as 5°, and beyond this limit a detrimental effect likely occurs. Collectively, these results suggest that a provenance best suited to one environment might not be the best for another environment. However, these findings will be useful in understanding the genecology of paper birch when establishing operational seed-transfer guidelines in BC.     

Comparison of ecological condition and conservation status of English yew population in two Austrian gene conservation forests

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.     

Structural diversity of English yew (<Emphasis Type="Italic">Taxus baccata</Emphasis> L.) populations

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.