Ahornschmierlaus Phenaccocus aceris als ��bertr?ger des Little Cherry Virus-2 an S��?kirsche in Baden-W��rttemberg nachgewiesen

The Apple mealybug Phenacoccus aceris was verified as the vector of the Little Cherry Virus-2 (LChV-2) in Baden-Württemberg. However, this does not exclude the participation of even more different vectors. Because the Apple mealybug is more spread than presumed as of yet, this vector should be specifically controlled as well as fought in cherry orchards. If planting new cherry orchards it must be strictly adhered to virus-free, certificated plant matter, so that in areas free from Little cherry an epidemic as in the ??Altes Land?? can be avoided.     

Tree,stand and site characteristics affecting the occurrence of lammas growth and multiple tops in field-grown Norway spruce

New Forests - In the Nordic-Baltic region, there has been a growing concern about an increasing occurrence of multiple tops in young stands of Norway spruce. There is however a lack of...     

Estimating the age–diameter relationship of oak species in Switzerland using nonlinear mixed-effects models

Tree growth plays a key role in forest dynamics, yet little attention has been paid to quantifying tree age–diameter relationships. Predicting diameter growth of oaks is especially important due to their role in nature conservation and adaptive forest management under climate change. Thus, we (1) identified environmental variables that shape age–diameter relationships of oaks and (2) quantified the accuracy of predictions based on these variables. We determined the age–diameter relationship of 243 oaks (Quercus spp.) growing in Switzerland by using tree-ring samples. Nonlinear mixed-effects models based on a modified Chapman-Richards equation were fitted with environmental variables included as covariates. The fixed effects elevation, slope and water-holding capacity were most important in shaping the age–diameter relationships. Lower elevations, steeper slopes, north-facing aspects, higher water-holding capacities and moister summers resulted in larger maximum diameters. For 75 % of the oaks, age–diameter relationships predicted by the fixed effects matched fairly well the observations (root mean square error between predictions and observations <6 cm); the inclusion of random effects reduced root mean square errors for 86 % of the trees. These results suggest that water runoff plays a key role for the age–diameter relationships, accompanied by limiting temperature effects at higher elevations. The fixed effects covered variability in site quality, whereas the random effects included tree-specific deviations from expected age–diameter relationships, potentially due to neighbourhood effects such as stand density and competition.     

Ecological and economical sustainability assessment of community forest management in Nepal: A reality check

This study analyzes the sustainability of community forest management, representing four forest types of two physiographic region Hills and Terai of Nepal. We assess the sustainability based on species composition, stand density, growing stock volume, and growth-to-removal ratio using inventory data of 109 permanent forest plots from four consecutive intervals of three to five years. In addition, forest users, forest committee members, and forest officials were consulted. We observed increment on the representation of economically valuable tree species in all forest types of both regions. The pole-size tree dominates in all forest types with declining number of trees and regeneration. In case of Hills forests, they were over-harvested until 2013 but were under-harvested in the recent period. In contrary, forests were under-harvested in the Terai. We found that ecological objectives of sustainable management are fully achieved while economic benefits remained unharnessed where harvesting is far below the growth. We conclude that maintaining a large number of trees may contribute to ecological but not on economical sustainability. We argue to rationalize annual harvest in all categories of the forest to enhance resource conditions together with regular benefits to the local communities.     

Past,current and future drivers for the development of decision support systems in forest management

The potential for development in decision support for forest management is set by decision theory, available technology and methods. Demands for decision support are emerging from contemporary challenges and problems of forest management which act as stimuli for the science community. Objectives and approaches in forest management as well as technologies have been changing throughout history. Accordingly, the demand for tools to support planning and decision-making has evolved. In this contribution, the authors review the historic development of decision support systems (DSS) for forest management and discuss past, current and future drivers. Based on evidence from scientific literature, case studies in the frame of the Forest Management Decision Support Systems (FORSYS) action, as well as experiences of the authors some hypotheses about the future of DSS are drawn. It is shown that in the past, the drivers evolving from forest management as well as decision support technologies have influenced the way of how models and methods have been applied as well as how DSS architectures have been designed. It is concluded that in the future, the challenges for DSS development will increase, as the complexity of decision-making processes and the related models will compete with the user demands which ask for simplicity.     

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.     

Establishing a spatial grouping base for surface soil properties along urban–rural gradient—A case study in Nanjing,China

Conventional classification systems based on vegetation and land use are frequently used to characterize or describe urban soils to determine the influence of urbanization on soils. In this study, the sensitivity of different grouping methods in reflecting soil variations along an urban–rural gradient was compared. The objective of this study was to determine the most sensitive grouping system in depicting and explaining variations of soil attributes around an urban area. Grouping methods, including urban–rural division, in situ vegetation type, land use types in different scales and numerical clustering, were compared for both single soil attributes and “soil set” defined by multiple variables. The result shows urbanization has a strong impact on many soil properties, especially that of gravel content, sand content, pH, phosphorus and soil compaction. In terms of the variations of soil attributes, in situ vegetation type is the most sensitive in comparison with local land use types and district-viewed land use types. In other words, soil properties in this study are not sensitive to coarser spatial resolution. Therefore, it's hard to interpret the spatial variation of urban soil by regular methods using natural soil-landscape paradigm. Furthermore, vegetation would best proxy the delineation of single attribute of urban soils. Numerical clusters effectively reflect the land use types and their change during urbanization. All clusters were interpreted as different sets with practical meanings: soil in abandoned greenbelt, soil in ill-managed greenbelt, soil in new vegetable land, extreme urban conditioned soil, soil in well-managed greenbelt, soil in highly mellowed vegetable land, soil in common urban–peri-urban greenbelt and weak-urban-impacted soil. They can be used as bases for soil regionalization in urban and peri-urban environment.     

Considerations on the future biomass production potential of Iceland,and what role that could have in future fuel supply and carbon balances

This study suggests that Iceland may be able to produce sufficient liquid hydrocarbon fuels from biological sources in the future to substitute the Icelandic 2016 consumption of fossil fuels, by using forest products. The authors evaluate a strategy to put forest on up to 35,000 km² in Iceland to 2050. The preliminary study shows that Iceland could reach climate neutrality around 2050 and be a significant net carbon sequester for the next 250 years. Approximate estimates suggest that the total forest biomass production could reach about 10 million m³yr^?1, comprising 3.1 million m³yr^?1 of roundwood, 3.1 million m³yr^?1 for generic biomass, and about 4.2 million m³yr^?1 woody material for biofuel use. This could result in a net annual carbon dioxide sequestration of 2–2.5 mill ton CO₂ yr^?1 by 2100. The calculations suggest that such an afforestation and land restoration undertaking would be long term profitable in economic terms and that the payback time would be about 2050. The method applied in this study is that of a static mass balance calculations at different time points into the future. Parallel to this work, a full integrated regional forest production model is being developed and will be applied to this issue.