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Wulf M.,Leibniz Center for Agricultural Landscape Research | Baeten L.,Ghent University | Brunet J.,Swedish University of Agricultural Sciences | Decocq G.,French National Center for Scientific Research | And 12 more authors.
Ecography | Year: 2016

Ecological niches of organisms vary across geographical space, but niche shift patterns between regions and the underlying mechanisms remain largely unexplored. We studied shifts in the pH niche of 42 temperate forest plant species across a latitudinal gradient from northern France to boreo-nemoral Sweden. We asked 1) whether species restrict their niches with increasing latitude as they reach their northern range margin (environmental constraints); 2) whether species expand their niches with increasing latitude as regional plant species richness decreases (competitive release); and 3) whether species shift their niche position toward more acidic sites with increasing latitude as the relative proportion of acidic soils increases (local adaptation). Based on 1458 vegetation plots and corresponding soil pH values, we modelled species response curves using Huisman-Olff-Fresco models. Four niche measures (width, position, left and right border) were compared among regions by randomization tests. We found that with increasing latitude, neutrophilic species tended to retreat from acidic sites, indicating that these species retreat to more favorable sites when approaching their range margin. Alternatively, these species might benefit from enhanced nitrogen deposition on formerly nutrient-poor, acidic sites in southern regions or lag behind in post-glacial recolonization of potential habitats in northern regions. Most acidophilic species extended their niche toward more base-rich sites with increasing latitude, indicating competitive release from neutrophilic species. Alternatively, acidophilic species might benefit from optimal climatic conditions in the north where some have their core distribution area. Shifts in the niche position suggested that local adaptation is of minor importance. We conclude that shifts in the pH niche of temperate forest plants are the rule, but the directions of the niche shifts and possible explanations vary. Our study demonstrates that differentiating between acidophilic and neutrophilic species is crucial to identify general patterns and underlying mechanisms. © 2016 Nordic Society Oikos.

Brunet-Navarro P.,Leibniz Center for Agricultural Landscape Research | Jochheim H.,Leibniz Center for Agricultural Landscape Research | Muys B.,Division Forest
Global Change Biology | Year: 2016

In addition to forest ecosystems, wood products are carbon pools that can be strategically managed to mitigate climate change. Wood product models (WPMs) simulating the carbon balance of wood production, use and end of life can complement forest growth models to evaluate the mitigation potential of the forest sector as a whole. WPMs can be used to compare scenarios of product use and explore mitigation strategies. A considerable number of WPMs have been developed in the last three decades, but there is no review available analysing their functionality and performance. This study analyses and compares 41 WPMs. One surprising initial result was that we discovered the erroneous implementation of a few concepts and assumptions in some of the models. We further described and compared the models using six model characteristics (bucking allocation, industrial processes, carbon pools, product removal, recycling and substitution effects) and three model-use characteristics (system boundaries, model initialization and evaluation of results). Using a set of indicators based on the model characteristics, we classified models using a hierarchical clustering technique and differentiated them according to their increasing degrees of complexity and varying levels of user support. For purposes of simulating carbon stock in wood products, models with a simple structure may be sufficient, but to compare climate change mitigation options, complex models are needed. The number of models has increased substantially over the last ten years, introducing more diversity and accuracy. Calculation of substitution effects and recycling has also become more prominent. However, the lack of data is still an important constraint for a more realistic estimation of carbon stocks and fluxes. Therefore, if the sector wants to demonstrate the environmental quality of its products, it should make it a priority to provide reliable life cycle inventory data, particularly regarding aspects of time and location. © 2016 John Wiley & Sons Ltd.

De Smedt P.,Ghent University | Wuyts K.,University of Antwerp | Baeten L.,Ghent University | De Schrijver A.,Ghent University | And 8 more authors.
Insect Conservation and Diversity | Year: 2016

Worldwide, forest fragmentation induces edge effects, thereby strongly altering the forest microclimate and abiotic characteristics in the forest edge compared to the forest interior. The impact of edge-to-interior gradients on abiotic parameters has been extensively studied, but we lack insights on how biodiversity, and soil communities in particular, are structured along these gradients. Woodlice (Isopoda) and millipedes (Diplopoda) are dominant macro-detritivores in temperate forests with acidic sandy soils. We investigated the distribution of these macro-detritivores along forest edge-to-interior gradients in six different forest stands with sandy soils in northern Belgium. Woodlouse abundance decreased exponentially with distance from the forest edge, whereas millipede abundance did not begin to decrease until 7 m inside the forest stands. Overall, these patterns were highly species specific and could be linked to the species' desiccation tolerance. Whereas the observed abundance patterns were independent from forest stand and dominant tree species, tree species had a large effect on community structure. Edge gradients in macro-detritivores may consequently have implications for nutrient cycling, especially in smaller forest fragments with a large edge-to-interior ratio. Insect Conservation and Diversity © 2016 The Royal Entomological Society.

Degerickx J.,Division Forest | Almeida J.,Division Forest | Moonen P.C.,Division Forest | Vervoort L.,Division Forest | And 2 more authors.
GCB Bioenergy | Year: 2015

Small-scale Jatropha cultivation and biodiesel production have the potential of contributing to local development, energy security, and greenhouse gas (GHG) mitigation. In recent years however, the GHG mitigation potential of biofuel crops is heavily disputed due to the occurrence of a carbon debt, caused by CO2 emissions from biomass and soil after land-use change (LUC). Most published carbon footprint studies of Jatropha report modeled results based on a very limited database. In particular, little empirical data exist on the effects of Jatropha on biomass and soil C stocks. In this study, we used field data to quantify these C pools in three land uses in Mali, that is, Jatropha plantations, annual cropland, and fallow land, to estimate both the Jatropha C debt and its C sequestration potential. Four-year-old Jatropha plantations hold on average 2.3 Mg C ha-1 in their above- and belowground woody biomass, which is considerably lower compared to results from other regions. This can be explained by the adverse growing conditions and poor local management. No significant soil organic carbon (SOC) sequestration could be demonstrated after 4 years of cultivation. While the conversion of cropland to Jatropha does not entail significant C losses, the replacement of fallow land results in an average C debt of 34.7 Mg C ha-1, mainly caused by biomass removal (73%). Retaining native savannah woodland trees on the field during LUC and improved crop management focusing on SOC conservation can play an important role in reducing Jatropha's C debt. Although planting Jatropha on degraded, carbon-poor cropland results in a limited C debt, the low biomass production, and seed yield attained on these lands reduce Jatropha's potential to sequester C and replace fossil fuels. Therefore, future research should mainly focus on increasing Jatropha's crop productivity in these degraded lands. © 2015 John Wiley & Sons Ltd.

Hundera K.,Jimma University | Honnay O.,Plant Conservation and Population Biology University of Leuven Kasteelpark Arenberg 31 2435 3001 Leuven Belgium | Aerts R.,Division Forest | Muys B.,Division Forest
African Journal of Ecology | Year: 2015

Ethiopian Afromontane moist forests where coffee grows as understorey shrub are traditionally managed by the local communities for coffee production through thinning of the shade tree canopy and slashing of competing undergrowth. This management practice has a negative impact on the coffee shrubs, because the removal of shade tree saplings and seedlings reduces the succession potential of the shade tree canopy, which threatens the very existence of the shade coffee production system. We assessed the functionality of small exclosures to initiate coffee shade tree canopy restoration through natural regeneration. Our results show that small exclosures have a strong restoration potential for the coffee shade trees preferred by farmers (Albizia schimperiana, A. gummifera and Millettia ferruginea), as evidenced from their seedling abundance, survival and growth. The regeneration of late-successional tree species of the moist Afromontane forest was not successful in the small exclosures, most probably due to the low abundance or absence of adult trees as seed sources for regeneration. Therefore, temporary establishment of small exclosures in degraded coffee forest fragments where shade trees are getting old or dying is recommended for sustainable shade coffee production. © 2015 John Wiley & Sons Ltd.

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