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| 1 | Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech显示文摘Background: Climate change triggered many studies showing that trends and events of environmental conditions can reduce but also accelerate growth at the stand and individual tree level. However, it is still rather unknown how climate change modifies the growth partitioning between the trees in forest stands.Methods: Based on long-term girth-tape measurements in mature monospecific and mixed-species stands of Norway spruce(Picea abies(L.) Karst.) and European beech(Fagus sylvatica L.) we traced the effect of the severe droughts in 2003 and 2015 from the stand down to the tree level.Results: Stand growth of Norway spruce decreased by about 30% in the once-in-a-century drought 2015, while European beech was much more drought resistant. Water availability generally amplified size-asymmetric growth partitioning. Especially in case of Norway spruce water availability primarily fostered the growth of predominant trees, whereas drought favoured the growth of small trees at the expense of the predominant ones. We could not detect significant differences between mixed and monospecific stands in this regard.Conclusions: The drought-induced reallocation of growth in favour of small trees in case of spruce may result from its isohydric character. We hypothesize that as small trees are shaded, they can benefit from the reduced water consumption of their sun-exposed taller neighbours. In case of beech, as an anisohydric species, tall trees suffer less and smaller trees benefit less under drought. The discussion elaborates the consequences of the water dependent growth allocation for forest monitoring, growth modelling, and silviculture. | Hans Pretzsch Gerhard Schutze Peter Biber | 2018 | Forest Ecosystems2018，5，3： | 2 |
| 2 | Forestry projections for species diversity-oriented management:an example from Central Europe显示文摘Introduction:Changes in socio-economy and climate are affecting the demand of wood products globally.At the same time,society requires that forest supporting structures like biodiversity are maintained and preserved while the demand for wood products is also covered.Management support systems,like forest simulation models,that are able to analyze connections as well as quantify trade-offs between forest structure management and biodiversity indicators are highly sought.However,such models are generally developed for the local plot or stand scale only and ecosystem-scale analyses are missing.In this study,we analyzed ways to interpret results from the single-tree forest simulator SILVA from the local to the ecosystem scale.We also analyzed the impacts of forest management on biodiversity using two species diversity indicators,the species profile index and the species intermingling,for scenarios adapted from the GLOBIOM model in the case study“Augsburg Western Forests”,a high productive region in South-Germany.In order to evaluate diversity tendencies across the ecosystem,we applied a moving window methodology.Results:The relevance of scale for the interpretation of management effects on species diversity was shown and clear differences between scenarios revealed.The differences between scenarios were particularly visible when comparing the two diversity indicators,especially because the species profile index focuses on vertical and horizontal information and the species intermingling focuses mainly on horizontal structures.Under a multifunctional scenario,biodiversity values could be preserved at all scales in the vertical dimension.However,under a bio-energy-oriented scenario diversity at the local scale was reduced,although at the ecosystem level,and only in the horizontal dimension,diversity remained at relatively high values.Conclusions:With this work,we can conclude that integrative modeling,with multiple scenarios,is highly needed to support forestry decision making and towards the evolution of forest management to consider the ecosystem scale,especially when the optimization of diversity is a management priority. | Astor Toraño Caicoya Peter Biber Werner Poschenrieder Fabian Schwaiger Hans Pretzsch | 2018 | Ecological Processes2018，7，1： | 0 |
| 3 | Effects of the urban heat island and climate change on the growth of Khaya senegalensis in Hanoi,Vietnam显示文摘Background: Recent projections expect that Vietnam will be affected most severely by climate change with higher temperatures, more precipitation and rising sea levels. Especially increased temperatures will worsen the situations in cities, amplifying the urban heat island effect. Green infrastructures, i.e. urban trees are a common tool to improve the urban micro-climate for humans. Vital and well growing trees provide greatest benefits such as evaporative cooling, shading, air filtering and carbon storage. However, urban tree growth is often negatively affected by urban growing conditions such as high soil sealing with compacted tree pits providing small growing spaces with limited water, nutrient and oxygen supply, further warm temperatures and high pollution emissions. This study analyzed the growth of urban and rural African mahogany {Khoyo senegalensis(Desr.) A. Juss.) trees in the city of Hanoi, Vietnam and the effects of the surrounding climate conditions on tree growth.Results: The results showed that rural African mahogany trees grew better than trees situated in the city center, which is contrary to other results on tree growth of temperate and subtropical cities worldwide. Moreover tree growth was similar regardless of the time of growth. Other results regarding stem growth of African mahogany located in different areas of Hanoi(east, west, north, city center) revealed a better growth in the northern and western outskirts of the city compared to the growth of trees in the city center.Conclusion: African mahogany trees in the urban centers of Hanoi showed a decreased growth compared to rural trees,which was likely induced by a low ground-water level and high pollution rates. In view of climate change and global warming, the decreased tree growth in the city center may also affea tree service provision such as shading and cooling. Those climate mitigation solutions are strongly needed in areas severely affected by climate change and global warming such as Vietnam. | Astrid Moser-Reischl Enno Uhl Thomas Rotzer Peter Biber Tran van Con Nguyen Thanh Tan Hans Pretzsch | 2018 | Forest Ecosystems2018，5，4： | 0 |
| 4 | Analysing the effect of stand density and site conditions on structure and growth of oak species using Nelder trials along an environmental gradient:experimental design,evaluation methods,and results显示文摘Background: Most current approaches in forest science and practice require information about structure and growth of individual trees rather than- or in addition to- sum and mean values of growth and yield at forest stand level as provided by classic experimental designs. By inventing the wheel design, Nelder provided the possibility to turn to the individual tree as basic information unit. Such trials provide valuable insights into the dependency of growth on stand density at particular sites.Methods: Here, we present an extension of the original design and evaluation by Nelder.(i) We established Nelder wheels along an environmental gradient through Europe in atlantic climate in Belgium and Germany, Mediterranean climate in Italy, continental climate in Hungary as well as on high land climate in Mexico. Such disjunct Nelder wheels along an environmental gradient can be regarded and analysed as a two-factor design with the factors of site condition and stand density.(ii) We present an advanced statistical approach to evaluate density dependent growth dynamics of trees planted in form of the Nelder design, which considers spatio-temporal autocorrelation.(iii)We prove the usefulness of the methods in improving ecological theory concerning density related productivity,trade-offs between facilitation and competition, and allometric relations between size variables.Results: First evaluations based on remeasured Nelder wheels in oak(Quercus robur L.) show a size growth differentiation during the first observation period. In particular, height growth is accelerated under higher competition indicating facilitation effects. We detect furthermore a high variability in allometric relations.Conclusions: The proposed design, methods, and results are discussed regarding their impact on forest practice,model building, and ecological theory. We conclude that the extended Nelder approach is highly efficient in providing currently lacking individual tree level information. | Enno Uhl Peter Biber Matthias Ulbricht Michael Heym Tamás Horváth Ferenc Lakatos Janós Gál Leonhard Steinacker Giustino Tonon Maurizio Ventura Hans Pretzsch | 2015 | Forest Ecosystems2015，2，3： | 0 |
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