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Hørsholm, Denmark

Poeplau C.,Johann Heinrich Von Thunen Institute | Don A.,Johann Heinrich Von Thunen Institute | Vesterdal L.,Forest and Landscape Denmark | Leifeld J.,ART Agroscope Reckenholz Tanikon | And 3 more authors.
Global Change Biology

Land-use change (LUC) is a major driving factor for the balance of soil organic carbon (SOC) stocks and the global carbon cycle. The temporal dynamic of SOC after LUC is especially important in temperate systems with a long reaction time. On the basis of 95 compiled studies covering 322 sites in the temperate zone, carbon response functions (CRFs) were derived to model the temporal dynamic of SOC after five different LUC types (mean soil depth of 30±6cm). Grassland establishment caused a long lasting carbon sink with a relative stock change of 128±23% and afforestation on former cropland a sink of 116±54%, 100 years after LUC (mean±95% confidence interval). No new equilibrium was reached within 120 years. In contrast, there was no SOC sink following afforestation of grasslands and 75% of all observations showed SOC losses, even after 100 years. Only in the forest floor, there was carbon accumulation of 0.38±0.04Mgha-1yr-1 in afforestations adding up to 38±4Mgha-1 labile carbon after 100 years. Carbon loss after deforestation (-32±20%) and grassland conversion to cropland (-36±5%), was rapid with a new SOC equilibrium being reached after 23 and 17 years, respectively. The change rate of SOC increased with temperature and precipitation but decreased with soil depth and clay content. Subsoil SOC changes followed the trend of the topsoil SOC changes but were smaller (25±5% of the total SOC changes) and with a high uncertainty due to a limited number of datasets. As a simple and robust model approach, the developed CRFs provide an easily applicable tool to estimate SOC stock changes after LUC to improve greenhouse gas reporting in the framework of UNFCCC. © 2011 Blackwell Publishing Ltd. Source

Achten W.M.J.,Catholic University of Leuven | Nielsen L.R.,Forest and Landscape Denmark | Aerts R.,Catholic University of Leuven | Lengkeek A.G.,Tree Domestication Team | And 7 more authors.

Jatropha curcas L. attracts a lot of interest as a biofuel crop, triggering large investments and rapid expansion of cultivation areas, and yet, it should still be considered as a (semi-)wild, undomesticated plant. To use the full potential of Jatropha and to support further expansion and systematic selection, breeding and domestication are a prerequisite. This review reveals and identifies gaps in knowledge that still impede domestication of Jatropha. Prebreeding knowledge is limited. In particular, the regeneration ecology and the degree of genetic diversity among and within natural populations in and outside the center of origin are poorly studied. There is only a limited understanding of the Jatropha breeding system and the effect of inbreeding and outbreeding. This review presents all currently available and relevant information on the species distribution, site requirements, regeneration ecology, genetic diversity, advances in selection, development of varieties and hybridization. It also describes possible routes to a better Jatropha germplasm, gives recommendations for tackling current problems and provides guidance for future research. We also discuss the participatory domestication strategy of Jatropha integration in agroforestry. © 2010 Future Science Ltd. Source

Wagner S.,TU Dresden | Collet C.,Agro ParisTech | Collet C.,French National Institute for Agricultural Research | Madsen P.,Forest and Landscape Denmark | And 3 more authors.
Forest Ecology and Management

This review describes key regeneration characteristics of the genus Fagus as represented by its four most prominent species: F. crenata (F.c.), F. grandifolia (F.g.), F. orientalis (F.o.) and F. sylvatica (F.s.). Similarities and differences in the relevant life phases of these species are identified. Those are related to natural disturbance regimes and synecological peculiarities of the forests where they grow, thereby establishing a basis for evaluating the likely outcome of different silvicultural measures. Common ecological characteristics of these Fagus species' life cycles include the masting phenomenon, pollen dispersal with effective distances of about 100 m, seed dispersal to about 20 m, seedling sensitivity to frost, drought, and animal predation, and a very shade tolerant establishment phase. This commonality suggests its appropriateness as a "model-genus". However, some species also have unique ecological characteristics not observed in the others. F.g. exhibits root suckering, and beech bark disease seems to trigger vegetative regeneration by that means. Likewise, its masting behaviour deviates from F.s. F.o. and F.c., occurring more frequently and more regularly. In F.c. forests, dwarf bamboo species and their ecological characteristics are important determinants of tree regeneration establishment. The small canopy gaps that commonly occur in Fagus dominated natural forests fit very well with the genus' regeneration characteristics. These conditions are best duplicated by management measures, which maintain partial overstory shading until the seedlings are large enough for release. However, such a strategy reduces chances to regenerate more light-demanding associated species. Together with differences in landowner objectives, the diversity of ecological conditions within and between the species of Fagus requires site-specific prescriptions to insure regeneration success, e.g. cutting regimes. Of particular interest to research are the challenges of managing mixed-species stands for high quality timber production in Central European and Caspian beech forests, the decline of F.g. and how to deal with the aftermath forest, and effective ways to manage F.c. in coexistence with dwarf bamboo. Further, the historic dispersal of heavy seeded Fagus species over long distances is still poorly understood. In addition, since their drought sensitive seedlings may be damaged or killed during extreme weather, research must address the possible effects of global climate change on the regeneration potential of beech forests. Species-bridging research may be needed to address these questions. © 2010 Elsevier B.V. Source

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